WorldWideScience

Sample records for satellite altimeter measurements

  1. Controls on ERS altimeter measurements over ice sheets: Footprint-scale topography, backscatter fluctuations, and the dependence of microwave penetration depth on satellite orientation

    Science.gov (United States)

    Arthern, R. J.; Wingham, D. J.; Ridout, A. L.

    2001-12-01

    We consider the reliability of radar altimeter measurements of ice sheet elevation and snowpack properties in the presence of surface undulations. We demonstrate that over ice sheets the common practice of averaging echoes by aligning the first return from the surface at the origin can result in a redistribution of power to later times in the average echo, mimicking the effects of microwave penetration into the snowpack. Algorithms that assume the topography affects the radar echo shape in the same way that waves affect altimeter echoes over the ocean will therefore lead to biased estimates of elevation. This assumption will also cause errors in the retrieval of echoshape parameters intended to quantify the penetration of the microwave pulse into the snowpack. Using numerical simulations, we estimate the errors in retrievals of extinction coefficient, surface backscatter, and volume backscatter for various undulating topographies. In the flatter portions of the Antarctic plateau, useful estimates of these parameters may be recovered by averaging altimeter echoes recorded by the European Remote Sensing satellite (ERS-1). By numerical deconvolution of the average echoes we resolve the depths in the snowpack at which temporal changes and satellite travel-direction effects occur, both of which have the potential to corrupt measurements of ice sheet elevation change. The temporal changes are isolated in the surface-backscatter cross section, while directional effects are confined to the extinction coefficient and are stable from year to year. This allows the removal of the directional effect from measurement of ice-sheet elevation change.

  2. Wind waves in tropical cyclones: satellite altimeter observations and modeling

    Science.gov (United States)

    Golubkin, Pavel; Kudryavtsev, Vladimir; Chapron, Bertrand

    2016-04-01

    Results of investigation of wind-wave generation by tropical cyclones using satellite altimeter data are presented. Tropical cyclones are generally relatively small rapidly moving low pressure systems that are capable of generating severe wave conditions. Translation of a tropical cyclone leads to a prolonged period of time surface waves in the right sector remain under high wind forcing conditions. This effect has been termed extended fetch, trapped fetch or group velocity quasi-resonance. A tropical cyclone wave field is thus likely more asymmetrical than the corresponding wind field: wind waves in the tropical cyclone right sector are more developed with larger heights than waves in the left one. A dataset of satellite altimeter intersections of the Western Pacific tropical cyclones was created for 2010-2013. Data from four missions were considered, i.e., Jason-1, Jason-2, CryoSat-2, SARAL/AltiKa. Measurements in the rear-left and front-right sectors of tropical cyclones were examined for the presence of significant wave asymmetry. An analytical model is then derived to efficiently describe the wave energy distribution in a moving tropical cyclone. The model essentially builds on a generalization of the self-similar wave growth model and the assumption of a strongly dominant single spectral mode in a given quadrant of the storm. The model provides a criterion to anticipate wave enhancement with the generation of trapped abnormal waves. If forced during a sufficient timescale interval, also defined from this generalized self-similar wave growth model, waves can be trapped and large amplification of the wave energy will occur in the front-right storm quadrant. Remarkably, the group velocity and corresponding wavelength of outrunning wave systems will become wind speed independent and solely relate to the translating velocity. The resulting significant wave height also only weakly depends on wind speed, and more strongly on the translation velocity. Satellite

  3. Geodetic Mobil Solar Spectrometer for JASON Altimeter Satellite Calibration

    Science.gov (United States)

    Somieski, A.; Buerki, B.; Geiger, A.; Kahle, H.-G.; Becker-Ross, H.; Florek, S.; Okruss, M.

    Atmospheric water vapor is a crucial factor in achieving highest accuracies for space geodetic measurements. Water vapor causes a delay of the propagation time of the altimeter satellite signal, which propagates into errors for the determination of surface heights. Knowledge of the precipitable water vapor (PW) enables a tropospheric correction of the satellite signal. Therefore, different remote sensing techniques have been pursued to measure the PW continuously. The prototype Geodetic Mobil Solar Spectrometer (GEMOSS) was developed at the Geodesy and Geodynamics Laboratory (GGL, ETH Zurich) in cooperation with the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) (Berlin, Germany). A new optical approach allows the simultaneous measurement of numerous single absorption lines of water vapor in the wide range between 728 nm and 915 nm. The large number of available absorption lines increases the accuracy of the absolute PW retrievals considerably. GEMOSS has been deployed during two campaigns in Greece in the framework of the EU-project GAVDOS, which deals with the calibration of the altimeter satellite JASON. During the overfly of JASON, the ground-based determination of PW enables the correction of the satellite measurements due to tropospheric water vapor. Comparisons with radiometer and radiosondes data allow to assess the accuracy and reliability of GEMOSS. The instrumental advancement of GEMOSS is presented together with the results of the campaigns carried out.

  4. Improved interpretation of satellite altimeter data using genetic algorithms

    Science.gov (United States)

    Messa, Kenneth; Lybanon, Matthew

    1992-01-01

    Genetic algorithms (GA) are optimization techniques that are based on the mechanics of evolution and natural selection. They take advantage of the power of cumulative selection, in which successive incremental improvements in a solution structure become the basis for continued development. A GA is an iterative procedure that maintains a 'population' of 'organisms' (candidate solutions). Through successive 'generations' (iterations) the population as a whole improves in simulation of Darwin's 'survival of the fittest'. GA's have been shown to be successful where noise significantly reduces the ability of other search techniques to work effectively. Satellite altimetry provides useful information about oceanographic phenomena. It provides rapid global coverage of the oceans and is not as severely hampered by cloud cover as infrared imagery. Despite these and other benefits, several factors lead to significant difficulty in interpretation. The GA approach to the improved interpretation of satellite data involves the representation of the ocean surface model as a string of parameters or coefficients from the model. The GA searches in parallel, a population of such representations (organisms) to obtain the individual that is best suited to 'survive', that is, the fittest as measured with respect to some 'fitness' function. The fittest organism is the one that best represents the ocean surface model with respect to the altimeter data.

  5. A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

    Science.gov (United States)

    Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

    1983-01-01

    Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

  6. Validation of Chinese HY-2 satellite radar altimeter significant wave height

    Institute of Scientific and Technical Information of China (English)

    YE Xiaomin; LIN Mingsen; XU Ying

    2015-01-01

    Chinese Haiyang-2(HY-2) satellite is the first Chinese marine dynamic environment satellite. The dual-frequency (Ku and C band) radar altimeter onboard HY-2 has been working effective to provide operational significant wave height (SWH) for more than three years (October 1, 2011 to present).We validated along-track Ku-band SWH data of HY-2 satellite against National Data Buoy Center (NDBC)in-situ measurements over a time period of three years from October 1, 2011 to September 30, 2014, the root mean square error (RMSE) and mean bias of HY-2 SWH is 0.38 m and (–0.13±0.35) m, respectively. We also did cross validation against Jason-2 altimeter SWH data,the RMSE and the mean bias is 0.36m and (–0.22±0.28) m, respectively. In order to compare the statistical results between HY-2 and Jason-2 satellite SWH data, we validated the Jason-2 satellite radar altimeter along-track Ku-band SWH data against NDBC measurements using the same method. The results demonstrate the validation method in this study is scientific and the RMSE and mean bias of Jason-2 SWH data is 0.26 m and (0.00±0.26) m, respectively. We also validated both HY-2 and Jason-2 SWH data every month, the mean bias of Jason-2 SWH data almost equaled to zero all the time, while the mean bias of HY-2 SWH data was no less than –0.31m before April 2013 and dropped to zero after that time. These results indicate that the statistical results for HY-2 altimeter SWH are reliable and HY-2 altimeter along-track SWH data were steady and of high quality in the last three years. The results also indicate that HY-2 SWH data have greatly been improved and have the same accuracy with Jason-2 SWH data after April, 2013. SWH data provided by HY-2 satellite radar altimeter are useful and acceptable for ocean operational applications.

  7. ALTWAVE: Toolbox for use of satellite L2P altimeter data for wave model validation

    Science.gov (United States)

    Appendini, Christian M.; Camacho-Magaña, Víctor; Breña-Naranjo, José Agustín

    2016-03-01

    To characterize some of the world's ocean physical processes such as its wave height, wind speed and sea surface elevation is a major need for coastal and marine infrastructure planning and design, tourism activities, wave power and storm surge risk assessment, among others. Over the last decades, satellite remote sensing tools have provided quasi-global measurements of ocean altimetry by merging data from different satellite missions. While there is a widely use of altimeter data for model validation, practical tools for model validation remain scarce. Our purpose is to fill this gap by introducing ALTWAVE, a MATLAB user-oriented toolbox for oceanographers and coastal engineers developed to validate wave model results based on visual features and statistical estimates against satellite derived altimetry. Our toolbox uses altimetry information from the GlobWave initiative, and provides a sample application to validate a one year wave hindcast for the Gulf of Mexico. ALTWAVE also offers an effective toolbox to validate wave model results using altimeter data, as well as a guidance for non-experienced satellite data users. This article is intended for wave modelers with no experience using altimeter data to validate their results.

  8. Simulation of the satellite radar altimeter sea ice thickness retrieval uncertainty

    Directory of Open Access Journals (Sweden)

    R. T. Tonboe

    2009-07-01

    Full Text Available Although it is well known that radar waves penetrate into snow and sea ice, the exact mechanisms for radar-altimeter scattering and its link to the depth of the effective scattering surface from sea ice are still unknown. Previously proposed mechanisms linked the snow ice interface, i.e. the dominating scattering horizon, directly with the depth of the effective scattering surface. However, simulations using a multilayer radar scattering model show that the effective scattering surface is affected by snow-cover and ice properties. With the coming Cryosat-2 (planned launch 2009 satellite radar altimeter it is proposed that sea ice thickness can be derived by measuring its freeboard. In this study we evaluate the radar altimeter sea ice thickness retrieval uncertainty in terms of floe buoyancy, radar penetration and ice type distribution using both a scattering model and ''Archimedes' principle''. The effect of the snow cover on the floe buoyancy and the radar penetration and on the ice cover spatial and temporal variability is assessed from field campaign measurements in the Arctic and Antarctic. In addition to these well known uncertainties we use high resolution RADARSAT SAR data to simulate errors due to the variability of the effective scattering surface as a result of the sub-footprint spatial backscatter and elevation distribution sometimes called preferential sampling. In particular in areas where ridges represent a significant part of the ice volume (e.g. the Lincoln Sea the simulated altimeter thickness estimate is lower than the real average footprint thickness. This means that the errors are large, yet manageable if the relevant quantities are known a priori. A discussion of the radar altimeter ice thickness retrieval uncertainties concludes the paper.

  9. Simulation of the satellite radar altimeter sea ice thickness retrieval uncertainty

    Science.gov (United States)

    Tonboe, R. T.; Pedersen, L. T.; Haas, C.

    2009-07-01

    Although it is well known that radar waves penetrate into snow and sea ice, the exact mechanisms for radar-altimeter scattering and its link to the depth of the effective scattering surface from sea ice are still unknown. Previously proposed mechanisms linked the snow ice interface, i.e. the dominating scattering horizon, directly with the depth of the effective scattering surface. However, simulations using a multilayer radar scattering model show that the effective scattering surface is affected by snow-cover and ice properties. With the coming Cryosat-2 (planned launch 2009) satellite radar altimeter it is proposed that sea ice thickness can be derived by measuring its freeboard. In this study we evaluate the radar altimeter sea ice thickness retrieval uncertainty in terms of floe buoyancy, radar penetration and ice type distribution using both a scattering model and ''Archimedes' principle''. The effect of the snow cover on the floe buoyancy and the radar penetration and on the ice cover spatial and temporal variability is assessed from field campaign measurements in the Arctic and Antarctic. In addition to these well known uncertainties we use high resolution RADARSAT SAR data to simulate errors due to the variability of the effective scattering surface as a result of the sub-footprint spatial backscatter and elevation distribution sometimes called preferential sampling. In particular in areas where ridges represent a significant part of the ice volume (e.g. the Lincoln Sea) the simulated altimeter thickness estimate is lower than the real average footprint thickness. This means that the errors are large, yet manageable if the relevant quantities are known a priori. A discussion of the radar altimeter ice thickness retrieval uncertainties concludes the paper.

  10. The Rigorous Geometric Model of Satellite Laser Altimeter and Preliminarily Accuracy Validation

    Directory of Open Access Journals (Sweden)

    TANG Xinming

    2016-10-01

    Full Text Available It has been paid attention to improving the elevation accuracy of satellite stereo images aided by laser altimeter. The GF-7 satellite scheduled to launch in 2018 will be equipped with optical stereo cameras and a laser altimeter. ICESat (Ice, Cloud, and land Elevation Satellite with GLAS(Geo-science Laser Altimeter System is the first and still only laser altimeter satellite for earth observation until now. In this paper, the comprehensively analysis about the rigorous geometric model and accuracy analysis of laser altimeter is presented. The error induced by laser pointing aberration and mounting is proposed, and the data processing workflow of ICESat/GLAS from level 0 to level 2 is introduced. What's more, the geo-location accuracy between this paper and GLAS product is compared and the model is validated by the result that the accuracy based on the model is about 3 cm and 11 cm in the horizontal and vertical direction, respectively. The laser altimeter data loaded on the ZY3-02 satellite has been processed and validated preliminarily. The conclusion of this paper is valuable and can be viewed as reference for the subsequent domestic laser altimeter satellites.

  11. Mean Sea Surface (mss) Model Determination for Malaysian Seas Using Multi-Mission Satellite Altimeter

    Science.gov (United States)

    Yahaya, N. A. Z.; Musa, T. A.; Omar, K. M.; Din, A. H. M.; Omar, A. H.; Tugi, A.; Yazid, N. M.; Abdullah, N. M.; Wahab, M. I. A.

    2016-09-01

    The advancement of satellite altimeter technology has generated many evolutions to oceanographic and geophysical studies. A multi-mission satellite altimeter consists with TOPEX, Jason-1 and Jason-2, ERS-2, Envisat-1, CryoSat-2 and Saral are extracted in this study and has been processed using Radar Altimeter Database System (RADS) for the period of January 2005 to December 2015 to produce the sea surface height (hereinafter referred to SSH). The monthly climatology data from SSH is generated and averaged to understand the variation of SSH during monsoon season. Then, SSH data are required to determine the localised and new mean sea surface (MSS). The differences between Localised MSS and DTU13 MSS Global Model is plotted with root mean square error value is 2.217 metres. The localised MSS is important towards several applications for instance, as a reference for sea level variation, bathymetry prediction and derivation of mean dynamic topography.

  12. MEAN SEA SURFACE (MSS MODEL DETERMINATION FOR MALAYSIAN SEAS USING MULTI-MISSION SATELLITE ALTIMETER

    Directory of Open Access Journals (Sweden)

    N. A. Z. Yahaya

    2016-09-01

    Full Text Available The advancement of satellite altimeter technology has generated many evolutions to oceanographic and geophysical studies. A multi-mission satellite altimeter consists with TOPEX, Jason-1 and Jason-2, ERS-2, Envisat-1, CryoSat-2 and Saral are extracted in this study and has been processed using Radar Altimeter Database System (RADS for the period of January 2005 to December 2015 to produce the sea surface height (hereinafter referred to SSH. The monthly climatology data from SSH is generated and averaged to understand the variation of SSH during monsoon season. Then, SSH data are required to determine the localised and new mean sea surface (MSS. The differences between Localised MSS and DTU13 MSS Global Model is plotted with root mean square error value is 2.217 metres. The localised MSS is important towards several applications for instance, as a reference for sea level variation, bathymetry prediction and derivation of mean dynamic topography.

  13. Acceleration of Sea Level Rise Over Malaysian Seas from Satellite Altimeter

    Science.gov (United States)

    Hamid, A. I. A.; Din, A. H. M.; Khalid, N. F.; Omar, K. M.

    2016-09-01

    Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS). Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA) are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

  14. ACCELERATION OF SEA LEVEL RISE OVER MALAYSIAN SEAS FROM SATELLITE ALTIMETER

    Directory of Open Access Journals (Sweden)

    A. I. A. Hamid

    2016-09-01

    Full Text Available Sea level rise becomes our concern nowadays as a result of variously contribution of climate change that cause by the anthropogenic effects. Global sea levels have been rising through the past century and are projected to rise at an accelerated rate throughout the 21st century. Due to this change, sea level is now constantly rising and eventually will threaten many low-lying and unprotected coastal areas in many ways. This paper is proposing a significant effort to quantify the sea level trend over Malaysian seas based on the combination of multi-mission satellite altimeters over a period of 23 years. Eight altimeter missions are used to derive the absolute sea level from Radar Altimeter Database System (RADS. Data verification is then carried out to verify the satellite derived sea level rise data with tidal data. Eight selected tide gauge stations from Peninsular Malaysia, Sabah and Sarawak are chosen for this data verification. The pattern and correlation of both measurements of sea level anomalies (SLA are evaluated over the same period in each area in order to produce comparable results. Afterwards, the time series of the sea level trend is quantified using robust fit regression analysis. The findings clearly show that the absolute sea level trend is rising and varying over the Malaysian seas with the rate of sea level varies and gradually increase from east to west of Malaysia. Highly confident and correlation level of the 23 years measurement data with an astonishing root mean square difference permits the absolute sea level trend of the Malaysian seas has raised at the rate 3.14 ± 0.12 mm yr-1 to 4.81 ± 0.15 mm yr-1 for the chosen sub-areas, with an overall mean of 4.09 ± 0.12 mm yr-1. This study hopefully offers a beneficial sea level information to be applied in a wide range of related environmental and climatology issue such as flood and global warming.

  15. Assimilation of Satellite Altimeter Data With a Four Dimensional Model of the Japan Sea

    Science.gov (United States)

    Hirose, Naoki; Ichiro, Fukumori; Jong-Hwan, Yoon

    1999-01-01

    A data assimilation is carried out to detect the variability of the Japan Sea circulation in the range from a few days to several years and from eddy to basin scale. The model applied in this study is the same 1/6 degree GFDL MOM1 as Kim and Yoon (1999) but is driven by ECMWF daily wind stress, heat and fresh water fluxes. The satellite altimeter data of TOPEX/POSEIDON, ERS-1 (phase C and G) and -2 are assimilated by an approximate Kalman filter (Fukumori and M.Rizzoli, 1995). The approximation is made by seeking an asymptotic steady error covariance matrix (Fukumori et al., 1993) and by introducing a coarser grid model for the innovation (data-model misfit). The coarse grid model is defined on 1/2 degree horizontal resolution and consists of the barotropic stream function, first baroclinic displacement and velocity amplitudes. The assimilated estimates explain about 6cm sea level variability of the data (approximately 12cm in the southern part), which is much larger than the previous reduced-gravity model and TOPEX/POSEIDON altimeter data assimilation (Hirose et al., 1999). The impacts of the T/P and ERS data on the filtered estimates are comparable. The result also shows high correlation to subsurface water temperatures measured by CTD. Many of the mesoscale eddies/disturbances travel east-northeastward with the advection speed of 1-3cm/s though most of them generated in the western region can not pass over the Oki Spur. The quasi-biennial variability found by Hirose and Ostrovskii (1999) did not show clear propagation pattern. The shallow Oki Spur may work as a "western boundary" to this signal. This is more plausible estimation than by the R-G model which has no bottom topography.

  16. GPS Survey of the salar de Uyuni, Bolivia, for Satellite Altimeter Calibration

    Science.gov (United States)

    Borsa, A. A.; Fricker, H. A.; Bills, B. G.; Carabajal, C. C.; Quinn, K.; Minster, J. B.; Schutz, B.

    2002-12-01

    The salar de Uyuni, a 100km x 100km salt flat in the Andean Altiplano of southern Bolivia, is the largest dry lake on Earth. The size, high albedo and remarkable flatness of the salar make it an ideal reference surface for satellite-based altimeters - in particular, the Geoscience Laser Altimeter System (GLAS) to be flown on the Ice, Cloud and Land Elevation Satellite (ICESat) - especially with regard to range measurements and waveform analysis of return signals. A simple reference surface such as the salar can be mapped by ground-based surveying, although the sheer size of the area requires adaptations to standard survey techniques. We describe a survey of the salar de Uyuni carried out with car-mounted kinematic GPS over a seven-day period in September 2002. We divided the salar surface into a number of survey grids that were driven in multiple directions to yield redundant measurements and corresponding error statistics at grid crossover points. Adjacent grids were overlapped so we could also determine errors between grids and over multi-day time periods. In addition, we set up five fixed GPS sites on the salar to serve as local survey control in post-processing. These fixed sites will be used to map ionospheric effects and interpolate them to the roving GPS receivers. If successful, this will allow reprocessing of GPS solutions using L1 data only, with a corresponding reduction in noise compared to solutions using the standard ionosphere-free LC combination. We present our surveyed topography of the eastern half of the salar de Uyuni, comparing it to previously-published elevation measurements and to the best geoid model available for the region. We show the close relationship between the topography of the salar and the shape of the geoid, a result we had expected since the salar is flooded each austral summer to an almost uniform depth. We also demonstrate knowledge of the surface height of the salar to within the measurement error specified for the GLAS

  17. A geopotential model from satellite tracking, altimeter, and surface gravity data: GEM-T3

    Science.gov (United States)

    Lerch, F. J.; Nerem, R. S.; Putney, B. H.; Felsentreger, T. L.; Sanchez, B. V.; Marshall, J. A.; Klosko, S. M.; Patel, G. B.; Williamson, R. G.; Chinn, D. S.

    1994-01-01

    An improved model of Earth's gravitational field, Goddard Earth Model T-3 (GEM-T3), has been developed from a combination of satellite tracking, satellite altimeter, and surface gravimetric data. GEM-T3 provides a significant improvement in the modeling of the gravity field at half wavelengths of 400 km and longer. This model, complete to degree and order 50, yields more accurate satellite orbits and an improved geoid representation than previous Goddard Earth Models. GEM-T3 uses altimeter data from GEOS 3 (1975-1976), Seasat (1978) and Geosat (1986-1987). Tracking information used in the solution includes more than 1300 arcs of data encompassing 31 different satellites. The recovery of the long-wavelength components of the solution relies mostly on highly precise satellite laser ranging (SLR) data, but also includes Tracking Network (TRANET) Doppler, optical, and satellite-to-satellite tracking acquired between the ATS 6 and GEOS 3 satellites. The main advances over GEM-T2 (beyond the inclusion of altimeter and surface gravity information which is essential for the resolution of the shorter wavelength geoid) are some improved tracking data analysis approaches and additional SLR data. Although the use of altimeter data has greatly enhanced the modeling of the ocean geoid between 65 deg N and 60 deg S latitudes in GEM-T3, the lack of accurate detailed surface gravimetry leaves poor geoid resolution over many continental regions of great tectonic interest (e.g., Himalayas, Andes). Estimates of polar motion, tracking station coordinates, and long-wavelength ocean tidal terms were also made (accounting for 6330 parameters). GEM-T3 has undergone error calibration using a technique based on subset solutions to produce reliable error estimates. The calibration is based on the condition that the expected mean square deviation of a subset gravity solution from the full set values is predicted by the solutions' error covariances. Data weights are iteratively adjusted until

  18. A study of possible sea state information in the sample and hold gate statistics for the GEOS-3 satellite altimeter

    Science.gov (United States)

    Wells, W. T.; Borman, K. L.; Mitchell, R. D.; Dempsey, D. J.

    1979-01-01

    The statistical variations in the sample gate outputs of the GEOS-3 satellite altimeter were studied for possible sea state information. After examination of a large number of statistical characteristics of the altimeter waveforms, it was found that the best sea predictor for H-1/3 in the range of 0 to 3 meters was the 75th percentile of sample and hold gate number 11.

  19. Validation, Analysis of the Chinese HY-2 Satellite Altimeter Data and their Applications in the China Sea and its Vicinity

    Science.gov (United States)

    Yang, Jungang; Zhang, Jie; Cui, Wei; Zhao, Xinhua; Han, Weixiao; Martinez, Bernat

    2016-08-01

    Chinese first altimetry satellite HY-2 has been on obit almost 5 years by now and a large amount of marine observing data of HY-2 altimeter have acquired. In this paper, sea surface height (SSH) data of HY-2 altimeter are validated by the SSH difference at the self- crossover of the HY-2 ascending and descending obit, and at the mutual-crossover of HY-2 and Jason-2 obit. Significant wave height (SWH) data of HY-2 altimeter are validated by the data of NDBC buoys. On the data application of HY-2 altimeter, mesoscale eddies in the South China Sea and the western Pacific Ocean, the characteristics of ocean wave in the China Sea and the characteristics of Kuroshio are analyzed by combing with Envsiat RA-2, Jason-1/2 data.

  20. A preliminary estimate of geoid-induced variations in repeat orbit satellite altimeter observations

    Science.gov (United States)

    Brenner, Anita C.; Beckley, B. D.; Koblinsky, C. J.

    1990-01-01

    Altimeter satellites are often maintained in a repeating orbit to facilitate the separation of sea-height variations from the geoid. However, atmospheric drag and solar radiation pressure cause a satellite orbit to drift. For Geosat this drift causes the ground track to vary by + or - 1 km about the nominal repeat path. This misalignment leads to an error in the estimates of sea surface height variations because of the local slope in the geoid. This error has been estimated globally for the Geosat Exact Repeat Mission using a mean sea surface constructed from Geos 3 and Seasat altimeter data. Over most of the ocean the geoid gradient is small, and the repeat-track misalignment leads to errors of only 1 to 2 cm. However, in the vicinity of trenches, continental shelves, islands, and seamounts, errors can exceed 20 cm. The estimated error is compared with direct estimates from Geosat altimetry, and a strong correlation is found in the vicinity of the Tonga and Aleutian trenches. This correlation increases as the orbit error is reduced because of the increased signal-to-noise ratio.

  1. A preliminary estimate of geoid-induced variations in repeat orbit satellite altimeter observations

    Science.gov (United States)

    Brenner, Anita C.; Beckley, B. D.; Koblinsky, C. J.

    1990-01-01

    Altimeter satellites are often maintained in a repeating orbit to facilitate the separation of sea-height variations from the geoid. However, atmospheric drag and solar radiation pressure cause a satellite orbit to drift. For Geosat this drift causes the ground track to vary by + or - 1 km about the nominal repeat path. This misalignment leads to an error in the estimates of sea surface height variations because of the local slope in the geoid. This error has been estimated globally for the Geosat Exact Repeat Mission using a mean sea surface constructed from Geos 3 and Seasat altimeter data. Over most of the ocean the geoid gradient is small, and the repeat-track misalignment leads to errors of only 1 to 2 cm. However, in the vicinity of trenches, continental shelves, islands, and seamounts, errors can exceed 20 cm. The estimated error is compared with direct estimates from Geosat altimetry, and a strong correlation is found in the vicinity of the Tonga and Aleutian trenches. This correlation increases as the orbit error is reduced because of the increased signal-to-noise ratio.

  2. Improved threshold retracker for satellite altimeter waveform retracking over coastal sea

    Institute of Scientific and Technical Information of China (English)

    GUO Jinyun; HWANG Cheiway; CHANG Xiaotao; LIU Yuting

    2006-01-01

    Data quality is a key factor for the application of satellite altimetry to geodesy and oceanography. Accuracy of altimetry is limited in the coastal area because the altimeter waveforms are seriously contaminated by topography and environmental pollution. So waveform retracking is needed to compute the range correction of geophysical data records (GDRs) for better accuracy. In this paper, a new waveform retracker named the improved threshold retracker (ITR) is put forward. The retracker first builds sub-waveforms based on leading edges detected in a waveform, then determines the middle point of each leading edge to compute the retracking range correction,finally calculates the referenced sea surface heights according to the geoid undulation from a local geopotential model and tide heights from an ocean tide model, and compares it with all retracking ranges to determine the best one. As a test, altimeter waveforms of Geosat/GM are retracked around the Taiwan coastal area. The result shows that accuracy of ITR method is two times better than that of theβ-5-parameter function-fitting method and threshold method, and three times better than that of GDRs. ITR can efficiently improve the altimetry accuracy of the coastal sea area.

  3. Variations in transport derived from satellite altimeter data over the Gulf Stream

    Science.gov (United States)

    Molinelli, E.; Lambert, R. B.

    1981-01-01

    Variations in total change of sea surface height (delta h) across the Gulf Stream are observed using Seasat radar altimeter data. The sea surface height is related to transport within the stream by a two layer model. Variations in delta h are compared with previously observed changes in transport found to increase with distance downstream. No such increase is apparent since the satellite transports show no significant dependence on distance. Though most discrepancies are less than 50 percent, a few cases differ by about 100 percent and more. Several possible reasons for these discrepancies are advanced, including geoid error, but only two oceanographic contributions to the variability are examined, namely, limitations in the two layer model and meanders in the current. It is concluded that some of the discrepancies could be explained as changes in the density structure not accounted for by the two layer model.

  4. The accuracy of satellite radar altimeter data over the Greenland ice sheet determined from airborne laser data

    DEFF Research Database (Denmark)

    Bamber, J.L.; Ekholm, Simon; Krabill, W.

    1998-01-01

    The 336 days of the geodetic phase of ERS-1 provides dense coverage, by satellite radar altimetry, of the whole of the Greenland ice sheet. These data have been used to produce a digital elevation model of the ice sheet. The errors present in the altimeter data were investigated via a comparison...... with airborne laser altimeter data an absolute accuracy typically in the range 2-10 cm +/- 10 cm. Comparison of differences between the radar and laser derived elevations, showed a correlation with surface slope. The difference between the two data sets ranged from 84 cm +/- 79 cm for slopes below 0.1 degrees...

  5. Trends of wave height and period in the Central Arabian Sea from 1996 to 2012: A study based on satellite altimeter data

    Digital Repository Service at National Institute of Oceanography (India)

    Hithin, N.K.; SanilKumar, V.; Shanas, P.R.

    : Ocean Eng., Vol.108; 2015; 416-425. Trends of wave height and period in the Central Arabian Sea from 1996 to 2012: A study based on satellite altimeter data N.K. Hithin, V. Sanil Kumar*, P.R. Shanas+ Ocean Engineering Division, CSIR... measures wind speed at 3 m above the sea surface and SWH at a 3-h interval. Wind observation is a 10-minute average with wind speed and direction sampled at 1 Hz by a cup anemometer with vane. The accuracy of wind speed measurements is 1.5% of full scale...

  6. Inversion of marine gravity anomalies over southeastern China seas from multi-satellite altimeter vertical deflections

    Science.gov (United States)

    Zhang, Shengjun; Sandwell, David T.; Jin, Taoyong; Li, Dawei

    2017-02-01

    The accuracy and resolution of marine gravity field derived from satellite altimetry mainly depends on the range precision and dense spatial distribution. This paper aims at modeling a regional marine gravity field with improved accuracy and higher resolution (1‧ × 1‧) over Southeastern China Seas using additional data from CryoSat-2 as well as new data from AltiKa. Three approaches are used to enhance the precision level of satellite-derived gravity anomalies. Firstly we evaluate a suite of published retracking algorithms and find the two-step retracker is optimal for open ocean waveforms. Secondly, we evaluate the filtering and resampling procedure used to reduce the full 20 or 40 Hz data to a lower rate having lower noise. We adopt a uniform low-pass filter for all altimeter missions and resample at 5 Hz and then perform a second editing based on sea surface slope estimates from previous models. Thirdly, we selected WHU12 model to update the corrections provided in geophysical data record. We finally calculated the 1‧ × 1‧ marine gravity field model by using EGM2008 model as reference field during the remove/restore procedure. The root mean squares of the discrepancies between the new result and DTU10, DTU13, V23.1, EGM2008 are within the range of 1.8- 3.9 mGal, while the verification with respect to shipboard gravity data shows that the accuracy of the new result reached a comparable level with DTU13 and was slightly superior to V23.1, DTU10 and EGM2008 models. Moreover, the new result has a 2 mGal better accuracy over open seas than coastal areas with shallow water depth.

  7. Unabated global mean sea-level rise over the satellite altimeter era

    Science.gov (United States)

    Watson, Christopher S.; White, Neil J.; Church, John A.; King, Matt A.; Burgette, Reed J.; Legresy, Benoit

    2015-06-01

    The rate of global mean sea-level (GMSL) rise has been suggested to be lower for the past decade compared with the preceding decade as a result of natural variability, with an average rate of rise since 1993 of +3.2 +/- 0.4 mm yr-1 (refs , ). However, satellite-based GMSL estimates do not include an allowance for potential instrumental drifts (bias drift). Here, we report improved bias drift estimates for individual altimeter missions from a refined estimation approach that incorporates new Global Positioning System (GPS) estimates of vertical land movement (VLM). In contrast to previous results (for example, refs , ), we identify significant non-zero systematic drifts that are satellite-specific, most notably affecting the first 6 years of the GMSL record. Applying the bias drift corrections has two implications. First, the GMSL rate (1993 to mid-2014) is systematically reduced to between +2.6 +/- 0.4 mm yr-1 and +2.9 +/- 0.4 mm yr-1, depending on the choice of VLM applied. These rates are in closer agreement with the rate derived from the sum of the observed contributions, GMSL estimated from a comprehensive network of tide gauges with GPS-based VLM applied (updated from ref. ) and reprocessed ERS-2/Envisat altimetry. Second, in contrast to the previously reported slowing in the rate during the past two decades, our corrected GMSL data set indicates an acceleration in sea-level rise (independent of the VLM used), which is of opposite sign to previous estimates and comparable to the accelerated loss of ice from Greenland and to recent projections, and larger than the twentieth-century acceleration.

  8. Gavdos/West Crete Cal-Val Site: Over a Decade Calibrations for Jason Series, SARAL/AltiKa, Cryosat-2, Sentinel-3 and Hy-2 Altimeter Satellites

    Science.gov (United States)

    Mertikas, Stelios; DonLon, Craig; Mavrochordatos, Constantin; Tziavos, Ilias; Galanakis, Demitris; Vergos, George; Baltazar Andersen, Ole; Tripolitsiotis, Achilles; Frantzis, Xenofon; Lin, Mingsen; Qiao, Fangli

    2016-08-01

    This work presents and compares the latest altimeter calibration results for Jason series, the SARAL/AltiKa the Chinese HY-2 missions and the ESA missions of CryoSat-2 and Sentinel-3, conducted at the Gavdos/Crete calibration/validation facilities. At first, the Jason altimeter calibration values will be given for the ascending Pass No.109 and the descending Pass No.18, based on the GDR-E (Jason-1), GDR-D (Jason- 2) and GDR-T (Jason-3) products. Secondly, these values will be cross-examined against the altimeter bias for the SARAL/AltiKa (GDR-T) satellite at Gavdos Cal/Val using its reference ascending orbit No. 571. The Chinese HY-2 satellite altimeter bias will be presented using the CRS1 permanent site in southwest Crete for the descending HY-2 Pass No. 280, at 20 Hz based on SGDR data products. Finally, values will be compared against the Sentinel-3 altimeter. Additionally, altimeter biases as determined by locally developed Mean Sea Surface models, will be presented and compared with the conventional sea-surface calibration methodology.

  9. The validation of HY-2 altimeter measurements of a significant wave height based on buoy data

    Institute of Scientific and Technical Information of China (English)

    WANG Jichao; ZHANG Jie; YANG Jungang

    2013-01-01

    HY-2 has been launched by China on August 16, 2011 which assembles multi-microwave remote sensing payloads in a body and has the ability of monitoring ocean dynamic environments. The HY-2 satellite data need to be calibrated and validated before being put into use. Based on the in-situ buoys from the Nation-al Data Buoy Center (NDBC), Ku-band significant wave heights (SWH, hs) of HY-2 altimeter are validated. Eleven months of HY-2 altimeter Level 2 products data are chose from October 1, 2011 to August 29, 2012. Using NDBC 60 buoys yield 902 collocations for HY-2 by adopting collocation criteria of 30 min for tempo-ral window and 50 km for a spatial window. An overall RMS difference of the SWH between HY-2 and buoy data is 0.297 m. A correlation coefficient between these is 0.964. An ordinary least squares (OLS) regression is performed with the buoy data as an independent variable and the altimeter data as a dependent vari-able. The regression equation of hs is hs(HY-2)=0.891×hs(NDBC)+0.022. In addition, 2016 collocations are matched with temporal window of 30 min at the crossing points of HY-2 and Jason-2 orbits. RMS difference of Ku-band SWH between the two data sets is 0.452 m.

  10. Prediction of bathymetry from satellite altimeter based gravity in the Arabian Sea: Mapping of two unnamed deep seamounts

    Science.gov (United States)

    Jena, B.; Kurian, P. J.; Swain, D.; Tyagi, A.; Ravindra, R.

    2012-06-01

    This work attempts to predict bathymetry from satellite altimeter based gravity in the Arabian Sea. A collocated match-up database (n = 17,016) was created on Multibeam Echosounder (MBES) bathymetry and satellite gravity values (˜1 min spatial resolution) derived from remote sensing satellites. A Radial Basis Function (RBF) based Artificial Neural Network (ANN) model was developed to predict bathymetry from satellite gravity values. The ANN model was trained with variable undersea features such as seamount, knoll, abyssal plain, hill, etc. to familiarize the network with all possible geomorphic features as inputs through learning and the corresponding target outputs. The performance of the predictive model was evaluated by comparing bathymetric values with MBES datasets that were not used during the training and verification steps of the ANN model formulation. The model was then compared with MBES surveyed seamount observations (those were not used during ANN analysis) and global model bathymetry products. Results demonstrate better performance of ANN model compared to global model products for mapping of two unnamed seamounts in the Arabian Sea. These two unnamed seamounts have been predicted, mapped and their morphology is reported for the first time through this work.

  11. Polarimetric, Two-Color, Photon-Counting Laser Altimeter Measurements of Forest Canopy Structure

    Science.gov (United States)

    Harding, David J.; Dabney, Philip W.; Valett, Susan

    2011-01-01

    Laser altimeter measurements of forest stands with distinct structures and compositions have been acquired at 532 nm (green) and 1064 nm (near-infrared) wavelengths and parallel and perpendicular polarization states using the Slope Imaging Multi-polarization Photon Counting Lidar (SIMPL). The micropulse, single photon ranging measurement approach employed by SIMPL provides canopy structure measurements with high vertical and spatial resolution. Using a height distribution analysis method adapted from conventional, 1064 nm, full-waveform lidar remote sensing, the sensitivity of two parameters commonly used for above-ground biomass estimation are compared as a function of wavelength. The results for the height of median energy (HOME) and canopy cover are for the most part very similar, indicating biomass estimations using lidars operating at green and near-infrared wavelengths will yield comparable estimates. The expected detection of increasing depolarization with depth into the canopies due to volume multiple-scattering was not observed, possibly due to the small laser footprint and the small detector field of view used in the SIMPL instrument. The results of this work provide pathfinder information for NASA's ICESat-2 mission that will employ a 532 nm, micropulse, photon counting laser altimeter.

  12. Geodynamics implication of GPS and satellite altimeter and gravity observations to the Eastern Mediterranean

    Directory of Open Access Journals (Sweden)

    Khaled H. Zahran

    2012-06-01

    Results show important zones of mass discontinuity in this region correlated with the seismological activities and temporal gravity variations agree with the crustal deformation obtained from GPS observations. The current study indicates that satellite gravity data is a valuable source of data in understanding the geodynamical behavior of the studied region and that satellite gravity data is an important contemporary source of data in the geodynamical studies.

  13. Lidar Altimeter Measurements of Canopy Structure: Methods and Validation for Closed Canopy, Broadleaf Forests

    Science.gov (United States)

    Harding, D. J.; Lefsky, M. A.; Parker, G. G.; Blair, J. B.

    1999-01-01

    Lidar altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne lidar altimeter data was acquired using the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) for a successional sequence of four, closed-canopy, deciduous forest stands in eastern Maryland. The four stands were selected so as to include a range of canopy structures of importance to forest ecosystem function, including variation in the height and roughness of the outer-most canopy surface and the vertical organization of canopy stories and gaps. The character of the SLICER backscatter signal is described and a method is developed that accounts for occlusion of the laser energy by canopy surfaces, transforming the backscatter signal to a canopy height profile (CHP) that quantitatively represents the relative vertical distribution of canopy surface area. The transformation applies an increased weighting to the backscatter amplitude as a function of closure through the canopy and assumes a horizontally random distribution of the canopy components. SLICER CHPs, averaged over areas of overlap where lidar ground tracks intersect, are shown to be highly reproducible. CHP transects across the four stands reveal spatial variations in vegetation, at the scale of the individual 10 m diameter laser footprints, within and between stands. Averaged SLICER CHPs are compared to analogous height profile results derived from ground-based sightings to plant intercepts measured on plots within the four stands. Tbe plots were located on the segments of the lidar ground tracks from which averaged SLICER CHPs were derived, and the ground observations were acquired within two weeks of the SLICER data acquisition to minimize temporal change. The differences in canopy structure between the four stands is similarly described by the SLICER and ground-based CHP results, however a Chi-square test of similarity

  14. A wave energy resource assessment in the China's seas based on multi-satellite merged radar altimeter data

    Institute of Scientific and Technical Information of China (English)

    WAN Yong; ZHANG Jie; MENG Junmin; WANG Jing

    2015-01-01

    Wave energy resources are abundant in both offshore and nearshore areas of the China's seas. A reliable assessment of the wave energy resources must be performed before they can be exploited. First, for a water depth in offshore waters of China, a parameterized wave power density model that considers the effects of the water depth is introduced to improve the calculating accuracy of the wave power density. Second, wave heights and wind speeds on the surface of the China's seas are retrieved from an AVISO multi-satellite altim-eter data set for the period from 2009 to 2013. Three mean wave period inversion models are developed and used to calculate the wave energy period. Third, a practical application value for developing the wave energy is analyzed based on buoy data. Finally, the wave power density is then calculated using the wave field data. Using the distribution of wave power density, the energy level frequency, the time variability indexes, the to-tal wave energy and the distribution of total wave energy density according to a wave state, the offshore wave energy in the China's seas is assessed. The results show that the areas of abundant and stable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, southeast of Taiwan in the China's seas; the wave power density values in these areas are approximately 14.0–18.5 kW/m. The wave energy in the China’s seas presents obvious seasonal variations and optimal seasons for a wave energy utilization are in winter and autumn. Except for very coastal waters, in other sea areas in the China's seas, the energy is primarily from the wave state with 0.5 m≤Hs≤4 m, 4 s≤Te≤10 s whereHs is a significant wave height andTe is an energy period; within this wave state, the wave energy accounts for 80% above of the total wave energy. This characteristic is advantageous to designing wave energy convertors (WECs). The practical application value of the wave energy is higher

  15. New Radar Altimeter Missions are Providing a Dramatically Sharper Image of Global Marine Tectonics

    Science.gov (United States)

    Sandwell, D. T.; Müller, D.; Garcia, E.; Matthews, K. J.; Smith, W. H. F.; Zaron, E.; Zhang, S.; Bassett, D.; Francis, R.

    2015-12-01

    Marine gravity, derived from satellite radar altimetry, is a powerful tool for mapping tectonic structures, especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment. The ability to infer seafloor tectonics from space was first demonstrated in 1978 using Seasat altimeter data but the spatial coverage was incomplete because of the short three-month lifetime of the satellite. Most ocean altimeters have repeat ground tracks with spacings of hundreds of kilometers so they do not resolve tectonic structures. Adequate altimeter coverage became available in 1995 when the United States Navy declassified the Geosat radar altimeter data and the ERS-1 altimeter completed a 1-year mapping phase. These mid-1990's altimeter-derived images of the ocean basins remained static for 15 years because there were no new non-repeat altimeter missions. This situation changed dramatically in 2010 when CryoSat-2, with its advanced radar altimeter, was launched into a non-repeat orbit and continues to collect data until perhaps 2020. In addition the Jason-1 altimeter was placed into a 14-month geodetic phase at the end of its lifetime. More recently the 1.5 times higher precision measurements from the AltiKa altimeter aboard the SARAL spacecraft began to drift away from its 35-day repeat trackline. The Chinese HY-2 altimeter is scheduled to begin a dense mapping phase in early 2016. Moreover in 2020 we may enjoy significantly higher resolution maps of the ocean basins from the planned SWOT altimeter mission with its advanced swath mapping ability. All of this new data will provide a much sharper image of the tectonics of the deep ocean basins and continental margins. During this talk we will tour of the new tectonic structures revealed by CryoSat-2 and Jason-1 and speculate on the tectonic views of the ocean basins in 2020 and beyond.

  16. Geoscience Laser Altimeter System (GLAS) on the ICESat Mission: Initial Science Measurement Performance

    Science.gov (United States)

    Abshire, J. B.; Sun, X.; Riris, H.; Sirota, M.; McGarry, J.; Palm, S.

    2003-12-01

    The Geoscience Laser Altimeter System is the space lidar on the NASA ICESat mision. Its design combines an altimeter with 5 cm precision with a laser pointing angle determination system and a dual wavelength cloud and aerosol lidar. GLAS measures the range to the Earth's surface with 1064 nm laser pulses. Each laser pulse produces a precision pointing measurement from the stellar reference system (SRS) and an echo pulse waveform, which permits range determination and waveform spreading analysis. The single shot ranging accuracy is < 10 cm for ice surfaces with slopes < 2 degrees. GLAS also measures atmospheric backscatter profiles at both 1064 and 532 nm. The 1064 nm measurements use an analog Si APD detector and measure the height and profile the backscatter signal from thicker clouds. The measurements at 532 nm use photon counting detectors, and will measure the vertical height distributions of optically thin clouds and aerosol layers Before launch, the measurement performance of GLAS was evaluated using a lidar test instrument called the Bench Check Equipment (BCE). The BCE was developed in parallel with GLAS and served as an inverse altimeter, inverse lidar and a stellar source simulator. It was used to simulate the range of expected optical inputs to the GLAS receiver by illuminating its telescope with simulated background light as well as laser echoes with known powers, energy levels, widths and delay times. The BCE also allowed monitoring of the transmitted laser energy, the angle measurements of the SRS, the co-alignment of the transmitted laser beam to the receiver line of sight, and performance of the flight science algorithms. Performance was evaluated during the GLAS development, before and after environmental tests, and after delivery to the spacecraft. The ICESat observatory was launched into a 94 degree inclination, 590 km altitude circular polar orbit on January 12, 2003. Beginning in early February, GLAS was powered on tested in stages. Its 1064 nm

  17. The eSurge-Venice project: altimeter and scatterometer satellite data to improve the storm surge forecasting in the city of Venice

    Science.gov (United States)

    Zecchetto, Stefano; De Biasio, Francesco; Umgiesser, Georg; Bajo, Marco; Vignudelli, Stefano; Papa, Alvise; Donlon, Craig; Bellafiore, Debora

    2013-04-01

    On the framework of the Data User Element (DUE) program, the European Space Agency is funding a project to use altimeter Total Water Level Envelope (TWLE) and scatterometer wind data to improve the storm surge forecasting in the Adriatic Sea and in the city of Venice. The project will: a) Select a number of Storm Surge Events occurred in the Venice lagoon in the period 1999-present day b) Provide the available satellite Earth Observation (EO) data related to the Storm Surge Events, mainly satellite winds and altimeter data, as well as all the available in-situ data and model forecasts c) Provide a demonstration Near Real Time service of EO data products and services in support of operational and experimental forecasting and warning services d) Run a number of re-analysis cases, both for historical and contemporary storm surge events, to demonstrate the usefulness of EO data The re-analysis experiments, based on hindcasts performed by the finite element 2-D oceanographic model SHYFEM (https://sites.google.com/site/shyfem/), will 1. use different forcing wind fields (calibrated and not calibrated with satellite wind data) 2. use Storm Surge Model initial conditions determined from altimeter TWLE data. The experience gained working with scatterometer and Numerical Weather Prediction (NWP) winds in the Adriatic Sea tells us that the bias NWP-Scatt wind is negative and spatially and temporally not uniform. In particular, a well established point is that the bias is higher close to coasts then offshore. Therefore, NWP wind speed calibration will be carried out on each single grid point in the Adriatic Sea domain over the period of a Storm Surge Event, taking into account of existing published methods. Point #2 considers two different methodologies to be used in re-analysis tests. One is based on the use of the TWLE values from altimeter data in the Storm Surge Model (SSM), applying data assimilation methodologies and trying to optimize the initial conditions of the

  18. Geoscience Laser Altimeter System (GLAS) on the ICESat Mission: Science Measurement Performance since Launch

    Science.gov (United States)

    Sun, X.; Abshire, J. B.; Riris, H.; McGarry, J.; Sirota, M.

    2004-12-01

    The Geoscience Laser Altimeter System is a space lidar and the primary instrument on NASA's ICESat mision. Since launch in January 2003 GLAS has produced about 544 million measurements of the Earth's surface and atmosphere. It has made global measurements of the Earth's icesheets, land topography and atmosphere with unprecedented vertical resolution and accuracy. GLAS was first activated for science measurements in February 2003. Since then its operation and performance has confirmed many pre-launch expectations and exceed a few of the most optimistic expectations in vertical resolution and sensitivity. However GLAS also suffered an unexpected failure with its first laser, and the GLAS measurements have yielded some surprises in other areas. This talk will give a post-launch assessment of the science measurement performance of the GLAS instrument, and compare the measurement environment and its science measurements to pre-launch expectations. It also will address some of what has been learned from the GLAS design, operations and measurements which may benefit future space lidar.

  19. Uncertainties in Steric Sea Level Change Estimation During the Satellite Altimeter Era: Concepts and Practices

    Science.gov (United States)

    MacIntosh, C. R.; Merchant, C. J.; von Schuckmann, K.

    2016-10-01

    This article presents a review of current practice in estimating steric sea level change, focussed on the treatment of uncertainty. Steric sea level change is the contribution to the change in sea level arising from the dependence of density on temperature and salinity. It is a significant component of sea level rise and a reflection of changing ocean heat content. However, tracking these steric changes still remains a significant challenge for the scientific community. We review the importance of understanding the uncertainty in estimates of steric sea level change. Relevant concepts of uncertainty are discussed and illustrated with the example of observational uncertainty propagation from a single profile of temperature and salinity measurements to steric height. We summarise and discuss the recent literature on methodologies and techniques used to estimate steric sea level in the context of the treatment of uncertainty. Our conclusions are that progress in quantifying steric sea level uncertainty will benefit from: greater clarity and transparency in published discussions of uncertainty, including exploitation of international standards for quantifying and expressing uncertainty in measurement; and the development of community "recipes" for quantifying the error covariances in observations and from sparse sampling and for estimating and propagating uncertainty across spatio-temporal scales.

  20. Uncertainties in Steric Sea Level Change Estimation During the Satellite Altimeter Era: Concepts and Practices

    Science.gov (United States)

    MacIntosh, C. R.; Merchant, C. J.; von Schuckmann, K.

    2017-01-01

    This article presents a review of current practice in estimating steric sea level change, focussed on the treatment of uncertainty. Steric sea level change is the contribution to the change in sea level arising from the dependence of density on temperature and salinity. It is a significant component of sea level rise and a reflection of changing ocean heat content. However, tracking these steric changes still remains a significant challenge for the scientific community. We review the importance of understanding the uncertainty in estimates of steric sea level change. Relevant concepts of uncertainty are discussed and illustrated with the example of observational uncertainty propagation from a single profile of temperature and salinity measurements to steric height. We summarise and discuss the recent literature on methodologies and techniques used to estimate steric sea level in the context of the treatment of uncertainty. Our conclusions are that progress in quantifying steric sea level uncertainty will benefit from: greater clarity and transparency in published discussions of uncertainty, including exploitation of international standards for quantifying and expressing uncertainty in measurement; and the development of community "recipes" for quantifying the error covariances in observations and from sparse sampling and for estimating and propagating uncertainty across spatio-temporal scales.

  1. NASA Ocean Altimeter Pathfinder Project. Report 1; Data Processing Handbook

    Science.gov (United States)

    Koblinsky, C. J.; Beckley, Brian D.; Ray, Richard D.; Wang, Yan-Ming; Tsaoussi, Lucia; Brenner, Anita; Williamson, Ron

    1998-01-01

    The NOAA/NASA Pathfinder program was created by the Earth Observing System (EOS) Program Office to determine how satellite-based data sets can be processed and used to study global change. The data sets are designed to be long time-sedes data processed with stable calibration and community consensus algorithms to better assist the research community. The Ocean Altimeter Pathfinder Project involves the reprocessing of all altimeter observations with a consistent set of improved algorithms, based on the results from TOPEX/POSEIDON (T/P), into easy-to-use data sets for the oceanographic community for climate research. This report describes the processing schemes used to produce a consistent data set and two of the products derived f rom these data. Other reports have been produced that: a) describe the validation of these data sets against tide gauge measurements and b) evaluate the statistical properties of the data that are relevant to climate change. The use of satellite altimetry for earth observations was proposed in the early 1960s. The first successful space based radar altimeter experiment was flown on SkyLab in 1974. The first successful satellite radar altimeter was flown aboard the Geos-3 spacecraft between 1975 and 1978. While a useful data set was collected from this mission for geophysical studies, the noise in the radar measured and incomplete global coverage precluded ft from inclusion in the Ocean Altimeter Pathfinder program. This program initiated its analysis with the Seasat mission, which was the first satellite radar altimeter flown for oceanography.

  2. Further development of an improved altimeter wind speed algorithm

    Science.gov (United States)

    Chelton, Dudley B.; Wentz, Frank J.

    1986-01-01

    A previous altimeter wind speed retrieval algorithm was developed on the basis of wind speeds in the limited range from about 4 to 14 m/s. In this paper, a new approach which gives a wind speed model function applicable over the range 0 to 21 m/s is used. The method is based on comparing 50 km along-track averages of the altimeter normalized radar cross section measurements with neighboring off-nadir scatterometer wind speed measurements. The scatterometer winds are constructed from 100 km binned measurements of radar cross section and are located approximately 200 km from the satellite subtrack. The new model function agrees very well with earlier versions up to wind speeds of 14 m/s, but differs significantly at higher wind speeds. The relevance of these results to the Geosat altimeter launched in March 1985 is discussed.

  3. Stream Gauges and Satellite Measurements

    Science.gov (United States)

    Alsdorf, D. E.

    2010-12-01

    Satellite measurements should not be viewed as a replacement for stream gauges. However, occasionally it is suggested that because satellite-based measurements can provide river discharge, a motivation for satellite approaches is an increasing lack of stream gauges. This is an argument for more stream gauges, but not necessarily for satellite measurements. Rather, in-situ and spaceborne methods of estimating discharge are complementary. Stream gauges provide frequent measurements at one point in the river reach whereas satellites have the potential to measure throughout all reaches but at orbital repeat intervals of days to weeks. The Surface Water and Ocean Topography satellite mission (SWOT) is an opportunity to further develop these complements. The motivation for SWOT, and indeed for any satellite based method of estimating discharge, should not be as a replacement for stream gauges. Scientific and application uses should motivate the measurements. For example, understanding floods with their dynamic water surfaces are best sampled from remote platforms that provide water surface elevations throughout the floodwave. As another example, today’s water and energy balance models are giving outputs at increasing spatial resolution and are making use of water surface elevations throughout the modeled basin. These models require a similar resolution in the calibrating and validating observations. We should also be aware of practical limitations. In addition to providing spatially distributed hydrodynamic measurements on rivers, SWOT will be able to measure storage changes in the estimated 30 million lakes in the world that are larger than a hectare. Knowing the storage changes in these lakes is especially important in certain regions such as the Arctic but gauging even a small fraction of these is impractical. Another motivator for satellite methods is that even in the presence of stream gauges, discharge data is not always well shared throughout all countries

  4. Altimeter Setting Indicator

    Data.gov (United States)

    Department of Transportation — The Altimeter Setting Indicator (ASI) is an aneroid system used at airports to provide an altimeter setting for aircraft altimeters. This indicator may be an analog...

  5. Variability of surface velocity in the Kuroshio Current and adjacent waters derived from Argos drifter buoys and satellite altimeter data

    Institute of Scientific and Technical Information of China (English)

    MA Chao; WU Dexing; LIN Xiaopei

    2009-01-01

    By combining Argos drifter buoys and TOPEX/POSEIDON altimeter data, the time series of sea-surface velocity fields in the Kuroshio Current (KC) and adjacent regions are established. And the variability of the KC from the Luzon Strait to the Tokara Strait is studied based on the velocity fields. The results show that the dominant variability period varies in different segments of the KC" The primary period near the Luzon Strait and to the east of Taiwan Island is the intra-seasonal time scale; the KC on the continental shelf of the ECS is the steadiest segment without obvious periodicity, while the Tokara Strait shows the period of seasonal variability. The diverse periods are caused by the Rossby waves propagating from the interior ocean, with adjustments in topography of island chain and local wind stress.

  6. Measurements of sea ice by satellite and airborne altimetry

    DEFF Research Database (Denmark)

    Kildegaard Rose, Stine

    A changing sea ice cover in the Arctic Ocean is an early indicator of a climate in transition, the sea ice has in addition a large impact on the climate. The annual and interannual variations of the sea ice cover have been observed by satellites since the start of the satellite era in 1979......, and it has been in retreat every since. The mass balance of the sea ice is an important input to climate models, where the ice thickness is the most uncertain parameter. In this study, data from the CryoSat-2 radar altimeter satellite are used. CryoSat-2 has been measuring the sea ice in the Arctic Ocean...... freeboard is found to be 35 cm for both the airborne and satellite data implying, that the radar signal is here reflected from the snow surface, probably due to weather conditions. CryoSat-2 is very sensitive to returns from specular surfaces, even if they appear o_-nadir. This contaminates the “true...

  7. GAVDOS/west crete cal-val site: Over a decade calibrations for Jason series, SARAL/Altika, cryoSat-2, Sentinel-3 and HY-2 altimeter satellites

    DEFF Research Database (Denmark)

    Mertikas, Stelios; Tziavos, Ilias; Galanakis, Demitris

    for the ascending Pass No.109 and the descending Pass No.18, based on the the GDR-E (Jason-1) and GDR-D (Jason-2) products. Secondly, these values will be cross-examined against the altimeter bias for the SARAL/AltiKa (GDR-T) satellite at Gavdos Cal/Val using its reference ascending orbit No. 571. The Chinese HY-2...

  8. Improved retracking algorithm for oceanic altimeter waveforms

    Institute of Scientific and Technical Information of China (English)

    Lifeng Bao; Yang Lu; Yong Wang

    2009-01-01

    Over the deep oceans without land/ice interference, the waveforms created by the return altimeter pulse generally follow the ocean model of Brown, and the corresponding range can be properly determined using the result from an onboard tracker. In the case of com-plex altimeter waveforms corrupted due to a variety of reasons, the processor on the satellite cannot properly determine the center of the leading edge, and range observations can be in error. As an efficacious method to improve the precision of those altimeter observations with complex waveforms, waveform retracking is required to reprocess the original returning pulse. Based on basic altimeter theory and the geometric feature of altimeter waveforms, we developed a new altimeter waveform retracker, which is valid for all altimeter wave-forms once there exists a reasonable returning signal. The performances of the existing Beta-5 retracker, threshold retracker, improved threshold retracker, and the new retracker are assessed in the experimental regions (China Seas and its adjacent regions), and the improvements in the accuracy of sea surface height are investigated by the difference between retracked altimeter observations and ref-erenced geoid. The comparisons denote that the new algorithm gives the best performance in both the open ocean and coastal regions. Also, the new retracker presents a uniform performance in the whole test region. Besides, there is a significant improvement in the short-wavelength precision and the spatial resolution of sea surface height after retracking process.

  9. Validation of satellite-derived tropical cyclone heat potential with in situ observations in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Nagamani, P.V.; Ali, M.M.; Goni, G.J.; Dinezio, P.N.; Pezzullo, J.C.; UdayaBhaskar, T.V.S.; Gopalakrishna, V.V.; Nisha, K.

    , there is a need for satellite-based estimations. One potential solution is to use sea surface height anomalies (SSHAs) from altimeter observations. However, any estimation derived from satellite measurements requires extensive regional validation...

  10. Deriving Time Series of Ice-Sheet Accumulation Variations from Altimeter Measurements of Surface-Elevation Changes

    Science.gov (United States)

    Zwally, H. J.; Li, J.

    2014-12-01

    Information on ice-sheet surface accumulation, A(t), is needed for studies of mass balance, polar climate variability, ice-sheet evolution, and dynamics. This paper describes a new method for deriving time series of A(t) variations, δA(t), on a monthly basis from continuous altimeter measurements. Changes in ice-sheet thickness and surface elevation are driven by a combination of δA(t), changes in the rates of firn compaction, and the rates of dynamic ice thickening or thinning (dHd/dt). Relevant time scales range from monthly fluctuations in δA(t) and surface temperature, Ts(t), to decadal to millennial scales of dynamic changes in ice flow. Our concept is based on the widely differing time-scales of principal processes, e.g. T> 5 years for dynamic changes and t = year/12 for δA(t) so that T >> t. An important aspect is our use of a baseline of ICESat-1 and ERS-1/ERS-2 altimeter measurements to obtain the multi-year (e.g. 5 to 17 years) dHd/dt of the Antarctic and Greenland ice sheets. We calculate changes in surface elevations caused by variations in the rate of firn compaction driven by both δA(t) and Ts(t) to adjust the altimeter-observed height changes, dH/dt, in order to derive dHd/dt over time periods of ≥ 5 years. Although monthly values of both δA(t) and Ts(t) are used, the derived dHd/dt is dependent only on the average change in δA(t) over the period and not on the higher-frequency monthly δA(t). On a monthly basis, the total accumulation-driven height change, dHaCA/dt, is a sum of the direct-height change, dHa/dt, and the change in firn compaction, dCA/dt, both caused by δA(t). dHa/dt is equal to δA(t)/ρs, where ρs is relative density of surface snow (typically 0.3) and δA(t) is w.e. Model simulations of dHaCA/dt driven by monthly δA(t) from ERA-interim re-analyses show that altimeter-observable dHaCA/dt and the desired dHa/dt = δA(t)/ρs are closely related. The relationship is better at colder locations such as the South Pole (Tm

  11. Crater Morphometry and Crater Degradation on Mercury: Mercury Laser Altimeter (MLA) Measurements and Comparison to Stereo-DTM Derived Results

    Science.gov (United States)

    Leight, C.; Fassett, C. I.; Crowley, M. C.; Dyar, M. D.

    2017-01-01

    Two types of measurements of Mercury's surface topography were obtained by the MESSENGER (MErcury Surface Space ENvironment, GEochemisty and Ranging) spacecraft: laser ranging data from Mercury Laser Altimeter (MLA) [1], and stereo imagery from the Mercury Dual Imaging System (MDIS) camera [e.g., 2, 3]. MLA data provide precise and accurate elevation meaurements, but with sparse spatial sampling except at the highest northern latitudes. Digital terrain models (DTMs) from MDIS have superior resolution but with less vertical accuracy, limited approximately to the pixel resolution of the original images (in the case of [3], 15-75 m). Last year [4], we reported topographic measurements of craters in the D=2.5 to 5 km diameter range from stereo images and suggested that craters on Mercury degrade more quickly than on the Moon (by a factor of up to approximately 10×). However, we listed several alternative explanations for this finding, including the hypothesis that the lower depth/diameter ratios we observe might be a result of the resolution and accuracy of the stereo DTMs. Thus, additional measurements were undertaken using MLA data to examine the morphometry of craters in this diameter range and assess whether the faster crater degradation rates proposed to occur on Mercury is robust.

  12. Comparison of airborne radar altimeter and ground-based Ku-band radar measurements on the ice cap Austfonna, Svalbard

    Directory of Open Access Journals (Sweden)

    O. Brandt

    2008-11-01

    Full Text Available We compare coincident data from the European Space Agency's Airborne SAR/Interferometric Radar Altimeter System (ASIRAS with ground-based Very High Bandwidth (VHB stepped-frequency radar measurements in the Ku-band. The ASIRAS instrument obtained data from ~700 m above the surface, using a 13.5 GHz center frequency and a 1 GHz bandwidth. The ground-based VHB radar measurements were acquired using the same center frequency, but with a variable bandwidth of either 1 or 8 GHz. Four sites were visited with the VHB radar; two sites within the transition region from superimposed ice to firn, and two sites in the long-term firn area (wet-snow zone. The greater bandwidth VHB measurements show that the first peak in the airborne data is a composite of the return from the surface (i.e. air-snow interface and returns of similar or stronger amplitude from reflectors in the upper ~30 cm of the subsurface. The peak position in the airborne data is thus not necessarily a good proxy for the surface since the maximum and width of the first return depend on the degree of interference between surface and subsurface reflectors. The major response from the winter snowpack was found to be caused by units of thin crust/ice layers (0.5–2 mm surrounded by large crystals (>3 mm. In the airborne data, it is possible to track such layers for tens of kilometers. The winter snowpack lacked thicker ice layers. The last year's summer surface, characterized by a low density large crystal layer overlaying a harder denser layer, gives a strong radar response, frequently the strongest. The clear relationship observed between the VHB and ASIRAS waveforms, justifies the use of ground-based radar measurements in the validation of air- or spaceborne radars.

  13. Mapping of sea bottom topography over western offshore, India using TOPEX/ERS-1 altimeter data

    Digital Repository Service at National Institute of Oceanography (India)

    Mohanty, K.K.; Majumdar, T.J.; Kunte, P.D.; Srivastava, A.K.

    convolution model using satellite altimeter data over the Indian offshore region. The study used TOPEX/POSEIDON as well as ERS-1 altimeter data, along with National Geophysical Data Centre (NGDC), USA ship-borne bathymetry data. The altimeter range data...

  14. Lunar Impact Basins: Stratigraphy, Sequence and Ages from Superposed Impact Crater Populations Measured from Lunar Orbiter Laser Altimeter (LOLA) Data

    Science.gov (United States)

    Fassett, C. I.; Head, J. W.; Kadish, S. J.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2012-01-01

    Impact basin formation is a fundamental process in the evolution of the Moon and records the history of impactors in the early solar system. In order to assess the stratigraphy, sequence, and ages of impact basins and the impactor population as a function of time, we have used topography from the Lunar Orbiter Laser Altimeter (LOLA) on the Lunar Reconnaissance Orbiter (LRO) to measure the superposed impact crater size-frequency distributions for 30 lunar basins (D = 300 km). These data generally support the widely used Wilhelms sequence of lunar basins, although we find significantly higher densities of superposed craters on many lunar basins than derived by Wilhelms (50% higher densities). Our data also provide new insight into the timing of the transition between distinct crater populations characteristic of ancient and young lunar terrains. The transition from a lunar impact flux dominated by Population 1 to Population 2 occurred before the mid-Nectarian. This is before the end of the period of rapid cratering, and potentially before the end of the hypothesized Late Heavy Bombardment. LOLA-derived crater densities also suggest that many Pre-Nectarian basins, such as South Pole-Aitken, have been cratered to saturation equilibrium. Finally, both crater counts and stratigraphic observations based on LOLA data are applicable to specific basin stratigraphic problems of interest; for example, using these data, we suggest that Serenitatis is older than Nectaris, and Humboldtianum is younger than Crisium. Sample return missions to specific basins can anchor these measurements to a Pre-Imbrian absolute chronology.

  15. Effective aerodynamic roughness estimated from airborne laser altimeter measurements of surface features

    NARCIS (Netherlands)

    De Vries, AC; Kustas, WP; Ritchie, JC; Klaassen, W; Menenti, M; Rango, A; Prueger, JH

    2003-01-01

    Aerodynamic roughness length (z(0)) and displacement height (d(0)) are important surface parameters for estimating surface fluxes in numerical models. These parameters are generally determined from wind flow characteristics using logarithmic wind profiles measured at a meteorological tower or by

  16. Effective aerodynamic roughness estimated from airborne laser altimeter measurements of surface features

    NARCIS (Netherlands)

    De Vries, AC; Kustas, WP; Ritchie, JC; Klaassen, W; Menenti, M; Rango, A; Prueger, JH

    2003-01-01

    Aerodynamic roughness length (z(0)) and displacement height (d(0)) are important surface parameters for estimating surface fluxes in numerical models. These parameters are generally determined from wind flow characteristics using logarithmic wind profiles measured at a meteorological tower or by bal

  17. First calibration results of Jason-2 and SARAL/AltiKa satellite altimeters from the Qianli Yan permanent Cal/Val facilities, China

    Science.gov (United States)

    Yang, Lei; Zhou, Xinghua; Mertikas, S. P.; Zhu, Lin; Yang, Long; Lei, Ning

    2017-06-01

    This work presents the first calibration results for the Jason-2 and the SARAL/AltiKa altimetric missions by using the permanent calibration facilities on the Qianli Yan islet (China). Qianli Yan is located in the Yellow Sea and only ∼3 km from the Jason-2 and SARAL/AltiKa crossover point. Analysis of the Jason-2 and SARAL/AltiKa waveform data and geophysical data over the Qianli Yan calibration area has proven that the altimeters and microwave radiometers are not contaminated by the mainland or the islet. The accuracies of the regional geoid model, provided by the First Institute of Oceanography (FIO), State Oceanic Administration of China, and the DTU10 MSS model were assessed by a GNSS buoy experiment. The results indicated that the FIO model is suitable for altimeter calibration in the Qianli Yan area. From the observations and the geoid model, the absolute biases for the Jason-2 and SARAL/AltiKa altimeters (2013-2014) were determined as 21.0 ± 5.9 and -44.0 ± 7.3 mm, respectively. The 2 years' results indicated that the Jason-2 bias had no trend. However, the SARAL/AltiKa bias presented a downward trend that was more stable in 2014 than in 2013. The Qianli Yan results are consistent with those determined by other international dedicated calibration sites and crossover analysis.

  18. Photon-counting spaceborne altimeter simulator

    Science.gov (United States)

    Blazej, Josef

    2004-11-01

    We are presenting of a photon counting laser altimeter simulator. The simulator is designed to be a theoretical and numerical complement for a Technology Demonstrator of the space born laser altimeter for planetary studies built on our university. The European Space Agency has nominated the photon counting altimeter as one of the attractive devices for planetary research. The device should provide altimetry in the range 400 to 1400 km with one meter range resolution under rough conditions - Sun illumination, radiation, etc. The general altimeter concept expects the photon counting principle laser radar. According to this concept, the simulator is based on photon counting radar simulation, which has been enhanced to handle planetary surface roughness, vertical terrain profile and its reflectivity. The simulator is useful complement for any photon counting altimeter both for altimeter design and for measured data analysis. Our simulator enables to model the orbital motion, range, terrain profile, reflectivity, and their influence on the over all energy budget and the ultimate signal to noise ratio acceptable for the altimetry. The simulator can be adopted for various air or space born application.

  19. Bowie Lecture: The Record of Sea Level Change from Satellite Measurements: What Have We Learned?

    Science.gov (United States)

    Nerem, R. S.

    2005-12-01

    Over the last decade, satellite geodetic measurements together with in situ measurements, have revolutionized our understanding of present-day sea level change. This is important because sea level change can be used as one barometer of climate variations and because of the implications sea level change has for coastal populations. With measurements from satellite altimeter missions (TOPEX/Posiedon and Jason), satellite gravity missions (GRACE), and the Global Positioning System (GPS), we are now able to start asking some important questions with regards to global sea level change and its regional variations. What has been the rate of global mean sea level change over the last dozen years? Is this rate different from the historical rate observed by the tide gauges over the last century? What are the principal causes of the observed sea level change, and are they related to anthropogenic climate variations? The record of sea level change from satellite altimetry will be reviewed, its error sources and limitations discussed, and the results placed in context with other estimates of sea level change from tide gauges, in situ measurements, and global climate models. The much shorter, but just as important, record of ocean mass variations from satellite gravity measurements will be similarly reviewed. In addition, GPS measurements of the deformation of the solid Earth due to the melting of continental ice and what they tell us about sea level change will be discussed. A sea level change budget will be presented, both for the altimetric era and the last century, containing estimates of contributions from thermal expansion, ocean mass changes (melting ice, runoff, etc.), and other contributions to sea level change. Finally, the need for continuing the satellite measurements of sea level change will be discussed in the context of future missions and the scientific gain that would result.

  20. Detailed gravimetric geoid for the GEOS-C altimeter calibration area

    Science.gov (United States)

    Marsh, J. G.; Vincent, S.

    1974-01-01

    The GEOS-C spacecraft scheduled for launch in late 1974 will carry a radar altimeter for the purpose of measuring sea surface topography. In order to calibrate and evaluate the performance of the altimeter system, ground truth data are required. In this respect a detailed gravimetric geoid has been computed for the GEOS-C altimeter calibration area in the Atlantic Ocean off the East Coast of the U.S. This geoid is based upon a combination of mean free air surface gravity anomalies and the Goddard Space Flight Center GEM-6 satellite-derived spherical harmonic coefficients. Surface gravity anomalies have been used to provide information on the short wave length undulations of the geoid while the satellite-derived coefficients have provided information on the long wave length components. As part of these analyses, GSFC, SAO and OSU satellite-derived gravity models were used in the computations. Although geoid heights based upon the various satellite models differed by as much as 30 meters in the Southern Hemisphere, the differences in this Atlantic Ocean area were less than 4 meters.

  1. Ocean topography mapping, improvement of the marine geoid, and global permanent ocean circulation studies from TOPEX/Poseidon altimeter data

    Science.gov (United States)

    Marsh, James G.; Lerch, F. J.; Koblinsky, C. J.; Nerem, R. S.; Klosko, S. M.; Williamson, R. G.

    1991-01-01

    The TOPEX/POSEIDON altimeter measurements will be the first global observations of the sea surface with accuracy sufficient to make quantitative determinations of the ocean's general circulation and its variations. These measurements are an important step to understanding global change in the ocean and its impact on the climate. Our investigation will focus on the examination of features in the sea surface elevation at the largest spatial and temporal scales. TOPEX/POSEIDON altimeter measurements will be used in conjunction with observations from past satellite-altimeter missions, such as NASA's GEOS-3 and Seasat, the U.S. Navy's Geosat and SALT, and the European Remote Sensing satellite in order to address the following issues: (1) Improve models of the marine geoid, especially at wavelengths needed to understand the basin-scale ocean dynamic topograpy. (2) Measure directly from the altimeter data the expression of the mean global ocean circulation in the sea surface at the largest scales through a simultaneous solution for gravity, orbital, and oceanographic parameters. (3) Examine the sea surface measurements for changes in global ocean mass or volume, interannual variations in the basin-scale ocean circulation, and annual changes in the heating and cooling of the upper ocean.

  2. Hydrological parameter estimation for ungauged basin based on satellite altimeter data and discharge modeling. A simulation for the Caqueta River (Amazonian Basin, Colombia

    Directory of Open Access Journals (Sweden)

    J. G. Leon

    2006-09-01

    Full Text Available The main objective of this paper is to review the usefulness of altimetric data in ungauged or very poorly monitored basin. It is shown that altimetric measurements can be combined with a single in-situ gauge to derive a reliable stage-discharge relationship upstream from the gauge. The Caqueta River in the Colombian Amazon Basin was selected to simulate a poorly monitored basin. Thus it was possible to derive the stage-discharge relationship for 13 "virtual gauge stations'' defined at river crossing with radar altimetric ground tracks. Stage measurements are derived from altimetric data following the methodology developed by Leon et al. (2006. Discharge is modeled using PROGUM – a flow routing model based on the Muskingum Cunge (M-C approach considering a diffusion-cum-dynamic wave propagation (Leon et al., 2006 using a single gauge located downstream from the basin under study. Rating curve parameters at virtual stations are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the modelled discharges. The methodology allows the ellipsoidal height of effective zero flow to be estimated. This parameter is a good proxy of the mean water depth from which the bottom slope of the reaches can be computed. Validation has been conducted by comparing the results with stages and discharges measured at five other gauges available on the Caqueta basin. Outflow errors range from 10% to 20% between the upper basin and the lower basin, respectively. Mean absolute differences less than 1.10 m between estimated equivalent water depth and measured water depth indicates the reliability of the proposed method. Finally, a 1.2×10−4 mm−1 mean bottom slope has been obtained for the 730 km long reach of the Caqueta main stream considered.

  3. Ocean surface waves and winds over the north Indian Ocean from satellite altimeter - preliminary results of SAC-NIO joint project

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.; Rajkumar, R.; Gairola, R.M.; Gohil, B.S.; Vethamony, P.; Rao, L.V.G.

    and NIO. Though there had been three cruises during the period, there were very few satellite-ship overlaps. Data pairs (satellite derived and in situ) of surface wind speed, significant wave height and minimum significant swell height were used to find...

  4. Dynamic sea surface topography, gravity, and improved orbit accuracies from the direct evaluation of Seasat altimeter data

    Science.gov (United States)

    Marsh, J. G.; Koblinsky, C. J.; Lerch, F.; Klosko, S. M.; Robbins, J. W.

    1990-01-01

    A gravitational model incorporating Seasat altimetry, surface gravimetry, and satellite tracking data has been determined in terms of global spherical harmonics complete to degree and order 50. This model, PGS-3337, uses altimeter data as a dynamic observation of the satellite's height above the sea surface. A solution for the ocean's dynamic topography is recovered simultaneously with the orbit parameters, gravity, and ocean tidal terms. The recovered dynamic topography reveals the global long wavelength circulation of the oceans with a resolution of 2000 km and is very similar to the mean upper ocean dynamic height derived from historical ship observations. The PGS-3337 geoid has an uncertainty of 60 cm rms globally but 25 cm rms over the ocean because of the altimeter measurements. Seasat orbits determined in this solution have an estimated accuracy for the radial position of 20 cm rms. The difference between the altimeter observed sea height and the geoid plus dynamic topography model is 30 cm rms. Contained in these residuals are the sea height variability, as well as errors from the geoid, orbits, tidal models, and altimeter range measurement. This performance level is 2 to 3 times better than that achieved with previous Goddard gravitational models.

  5. A Fiducial Reference Stie for Satellite Altimetry in Crete, Greece

    Science.gov (United States)

    Mertikas, Stelios; Donlon, Craig; Mavrocordatos, Constantin; Bojkov, Bojan; Femenias, Pierre; Parrinello, Tommaso; Picot, Nicolas; Desjonqueres, Jean-Damien; Andersen, Ole Baltazar

    2016-08-01

    With the advent of diverse satellite altimeters and variant measuring techniques, it has become mature in the scientific community, that an absolute reference Cal/Val site is regularly maintained to define, monitor, control the responses of any altimetric system.This work sets the ground for the establishment of a Fiducial Reference Site for ESA satellite altimetry in Gavdos and West Crete, Greece. It will consistently and reliably determine (a) absolute altimeter biases and their drifts; (b) relative bias among diverse missions; but also (c) continuously and independently connect different missions, on a common and reliable reference and also to SI-traceable measurements. Results from this fiducial reference site will be based on historic Cal/Val site measurement records, and will be the yardstick for building up capacity for monitoring climate change. This will be achieved by defining and assessing any satellite altimeter measurements to known, controlled and absolute reference signals with different techniques, processes and instrumentation.

  6. Measurement of Satellite Bunches at the LHC

    CERN Document Server

    Jeff, A; Boccardi, A; Bozyigit, S; Bravin, E; Lefevre, T; Rabiller, A; Roncarolo, F; Welsch, C P; Fisher, A S

    2012-01-01

    The RF gymnastics involved in the delivery of proton and lead ion bunches to the LHC can result in satellite bunches of varying intensity occupying the nominally empty RF buckets. Quantification of these satellites is crucial for bunch-by-bunch luminosity normalization as well as for machine protection. We present an overview of the longitudinal density monitor (LDM) which is the principal instrument for the measurement of satellite bunches in the LHC. The LDM uses single photon counting of synchrotron light. The very high energies reached in the LHC, combined with a dedicated undulator for diagnostics, allow synchrotron light measurements to be made with both protons and heavy ions. The arrival times of photons are collected over a few million turns, with the resulting histogram corrected for the effects of the detector’s deadtime and afterpulsing in order to reconstruct the longitudinal profile of the entire LHC ring. The LDM has achieved a dynamic range in excess of 105 and a time resolution of 90 ps. Ex...

  7. Antarctica: measuring glacier velocity from satellite images.

    Science.gov (United States)

    Lucchitta, B K; Ferguson, H M

    1986-11-28

    Many Landsat images of Antarctica show distinctive flow and crevasse features in the floating part of ice streams and outlet glaciers immediately below their grounding zones. Some of the features, which move with the glacier or ice stream, remain visible over many years and thus allow time-lapse measurements of ice velocities. Measurements taken from Landsat images of features on Byrd Glacier agree well with detailed ground and aerial observations. The satellite-image technique thus offers a rapid and cost-effective method of obtaining average velocities, to a first order of accuracy, of many ice streams and outlet glaciers near their termini.

  8. Integrated Monitoring of the Soya Warm Current Using HF Ocean Radars, Satellite Altimeters, Coastal Tide Gauges, and a Bottom-Mounted ADCP

    Science.gov (United States)

    Ebuchi, N.; Fukamachi, Y.; Ohshima, K. I.; Wakatsuchi, M.

    2007-12-01

    The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. The SWC flows into the Sea of Okhotsk from the Sea of Japan through the Soya/La Perouse Strait, which is located between Hokkaido, Japan, and Sakhalin, Russia. It supplies warm, saline water in the Sea of Japan to the Sea of Okhotsk and largely affects the ocean circulation and water mass formation in the Sea of Okhotsk, and local climate, environment and fishery in the region. However, the SWC has never been continuously monitored due to the difficulties involved in field observations related to, for example, severe weather conditions in the winter, political issues at the border strait, and conflicts with fishing activities in the strait. Detailed features of the SWC and its variations have not yet been clarified. In order to monitor variations in the SWC, three HF ocean radar stations were installed around the strait. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and subinertial variations of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference.

  9. Remote sensing of Gulf Stream using GEOS-3 radar altimeter

    Science.gov (United States)

    Leitao, C. D.; Huang, N. E.; Parra, C. G.

    1978-01-01

    Radar altimeter measurements from the GEOS-3 satellite to the ocean surface indicated the presence of expected geostrophic height differences across the the Gulf Stream. Dynamic sea surface heights were found by both editing and filtering the raw sea surface heights and then referencing these processed data to a 5 minute x 5 minute geoid. Any trend between the processed data and the geoid was removed by subtracting out a linear fit to the residuals in the open ocean. The mean current velocity of 107 + or - 29 cm/sec calculated from the dynamic heights for all orbits corresponded with velocities obtained from hydrographic methods. Also, dynamic topographic maps were produced for August, September, and October 1975. Results pointed out limitations in the accuracy of the geoid, height anomaly deteriorations due to filtering, and lack of dense time and space distribution of measurements.

  10. Satellite to measure equatorial ozone layer

    Science.gov (United States)

    1975-01-01

    The Atmosphere Explorer E (Explorer 55) Satellite is described. The satellite will gather information on the earth's upper atmosphere, particularly regarding the condition of the protective ozone layer. The satellite will also provide information concerning the earth's heat balance, and heat flow characteristics, and energy conversion mechanisms.

  11. ZY3-02 Laser Altimeter Footprint Geolocation Prediction

    Directory of Open Access Journals (Sweden)

    Junfeng Xie

    2017-09-01

    Full Text Available Successfully launched on 30 May 2016, ZY3-02 is the first Chinese surveying and mapping satellite equipped with a lightweight laser altimeter. Calibration is necessary before the laser altimeter becomes operational. Laser footprint location prediction is the first step in calibration that is based on ground infrared detectors, and it is difficult because the sample frequency of the ZY3-02 laser altimeter is 2 Hz, and the distance between two adjacent laser footprints is about 3.5 km. In this paper, we build an on-orbit rigorous geometric prediction model referenced to the rigorous geometric model of optical remote sensing satellites. The model includes three kinds of data that must be predicted: pointing angle, orbit parameters, and attitude angles. The proposed method is verified by a ZY3-02 laser altimeter on-orbit geometric calibration test. Five laser footprint prediction experiments are conducted based on the model, and the laser footprint prediction accuracy is better than 150 m on the ground. The effectiveness and accuracy of the on-orbit rigorous geometric prediction model are confirmed by the test results. The geolocation is predicted precisely by the proposed method, and this will give a reference to the geolocation prediction of future land laser detectors in other laser altimeter calibration test.

  12. Satellite measurements of formaldehyde from shipping emissions

    Directory of Open Access Journals (Sweden)

    T. Marbach

    2009-04-01

    Full Text Available International shipping is recognized as a pollution source of growing importance, in particular in the remote marine boundary layer. Nitrogen dioxide originating from ship emissions has previously been detected in satellite measurements. This study presents the first satellite measurements of formaldehyde (HCHO linked to shipping emissions as derived from observations made by the Global Ozone Monitoring Experiment (GOME instrument.

    We analyzed enhanced HCHO tropospheric columns from shipping emissions over the Indian Ocean between Sri Lanka and Sumatra. This region offers good conditions in term of plume detection with the GOME instrument as all ship tracks follow a single narrow track in the same east-west direction as used for the GOME pixel scanning. The HCHO signal alone is weak but could be clearly seen in the high-pass filtered data. The line of enhanced HCHO in the Indian Ocean as seen in the 7-year composite of cloud free GOME observations clearly coincides with the distinct ship track corridor from Sri Lanka to Indonesia. The observed mean HCHO column enhancement over this shipping route is about 2.0×1015 molec/cm2.

    The observed HCHO pattern also agrees qualitatively well with results from the coupled earth system model ECHAM5/MESSy applied to atmospheric chemistry (EMAC. However, the modelled HCHO values over the ship corridor are two times lower than in the GOME high-pass filtered data. This might indicate that the used emission inventories are too low and/or that the in-plume chemistry taking place in the narrow path of the shipping lanes are not well represented at the rather coarse model resolution.

  13. Spatial and Temporal Antarctic Ice Sheet Mass Trends, Glacio-Isostatic Adjustment, and Surface Processes from a Joint Inversion of Satellite Altimeter, Gravity, and GPS Data

    Science.gov (United States)

    Martin-Espanol, Alba; Zammit-Mangion, Andrew; Clarke, Peter J.; Flament, Thomas; Helm, Veit; King, Matt A.; Luthcke, Scott B.; Petrie, Elizabeth; Remy, Frederique; Schon, Nana; hide

    2016-01-01

    We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003-2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003-2013, Antarctica has been losing mass at a rateof -84 +/- 22 Gt per yr, with a sustained negative mean trend of dynamic imbalance of -111 +/- 13 Gt per yr. West Antarctica is the largest contributor with -112 +/- 10 Gt per yr, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade, with a mean rate of -28 +/- 7 Gt per yr and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total mass loss is partly compensated by a significant mass gain of 56 +/- 18 Gt per yr in East Antarctica due to a positive trend of surface mass balance anomalies.

  14. Integration Of GPS And GLONASS Systems In Geodetic Satellite Measurements

    Science.gov (United States)

    Maciuk, Kamil

    2015-12-01

    The article shows the results of satellites measurements elaborations using GPS & GLONASS signals. The aim of this article is to define the influence of adding GLONASS signals on position determination accuracy. It especially concerns areas with big horizon coverages. Object of the study were analysis of DOP coefficients, code and RTK solutions, and usage of satellite techniques in levelling. The performed studies and analysis show that integrated GPS-GLONASS satellite measurements provide possibility to achieve better results than measurements using single navigation satellite system (GPS).

  15. Thermal Conductivity Measurements on Icy Satellite Analogs

    Science.gov (United States)

    Javeed, Aurya; Barmatz, Martin; Zhong, Fang; Choukroun, Mathieu

    2012-01-01

    With regard to planetary science, NASA aspires to: "Advance scientific knowledge of the origin and history of the solar system, the potential for life elsewhere, and the hazards and resources present as humans explore space". In pursuit of such an end, the Galileo and Cassini missions garnered spectral data of icy satellite surfaces implicative of the satellites' structure and material composition. The potential for geophysical modeling afforded by this information, coupled with the plausibility of life on icy satellites, has pushed Jupiter's Europa along with Saturn's Enceladus and Titan toward the fore of NASA's planetary focus. Understanding the evolution of, and the present processes at work on, the aforementioned satellites falls squarely in-line with NASA's cited goal.

  16. Selected Geomagnetic Measurements From Several Satellites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — More than 17 million selected magnetic observations from several orbiting low-altitude satellites are contained in this digital collection. Except for MAGSAT, all...

  17. Inference of Altimeter Accuracy on Along-track Gravity Anomaly Recovery

    Directory of Open Access Journals (Sweden)

    LI Yang

    2015-04-01

    Full Text Available A correlation model between along-track gravity anomaly accuracy, spatial resolution and altimeter accuracy is proposed. This new model is based on along-track gravity anomaly recovery and resolution estimation. Firstly, an error propagation formula of along-track gravity anomaly is derived from the principle of satellite altimetry. Then the mathematics between the SNR (signal to noise ratio and cross spectral coherence is deduced. The analytical correlation between altimeter accuracy and spatial resolution is finally obtained from the results above. Numerical simulation results show that along-track gravity anomaly accuracy is proportional to altimeter accuracy, while spatial resolution has a power relation with altimeter accuracy. e.g., with altimeter accuracy improving m times, gravity anomaly accuracy improves m times while spatial resolution improves m0.4644 times. This model is verified by real-world data.

  18. A fiducial reference site for satellite altimetry in Crete, Greece

    DEFF Research Database (Denmark)

    Mertikas, Stelios; Donlon, Craig; Mavrokordatos, Constantin

    With the advent of diverse satellite altimeters and variant measuring techniques, it has become mature in the scientific community, that an absolute reference Cal/Val site is regularly maintained to define, monitor, control the responses of any altimetric system. This work sets the ground...

  19. Effect of High-Frequency Sea Waves on Wave Period Retrieval from Radar Altimeter and Buoy Data

    Directory of Open Access Journals (Sweden)

    Xifeng Wang

    2016-09-01

    Full Text Available Wave periods estimated from satellite altimetry data behave differently from those calculated from buoy data, especially in low-wind conditions. In this paper, the geometric mean wave period T a is calculated from buoy data, rather than the commonly used zero-crossing wave period T z . The geometric mean wave period uses the fourth moment of the wave frequency spectrum and is related to the mean-square slope of the sea surface measured using altimeters. The values of T a obtained from buoys and altimeters agree well (root mean square difference: 0.2 s only when the contribution of high-frequency sea waves is estimated by a wavenumber spectral model to complement the buoy data, because a buoy cannot obtain data from waves having wavelengths that are shorter than the characteristic dimension of the buoy.

  20. Altimeter Estimation of Sea Surface Wind Stress for Light to Moderate Winds

    Science.gov (United States)

    Vandemark, Douglas; Edson, James B.; Chapron, Bertrand

    1997-01-01

    Aircraft altimeter and in situ measurements are used to examine relationships between altimeter backscatter and the magnitude of near-surface wind and friction velocities. Comparison of altimeter radar cross section with wind speed is made through the modified Chelton-Wentz algorithm. Improved agreement is found after correcting 10-m winds for both surface current and atmospheric stability. An altimeter friction velocity algorithm is derived based on the wind speed model and an open-ocean drag coefficient. Close agreement between altimeter- and in situ-derived friction velocities is found. For this dataset, quality of the altimeter inversion to surface friction velocity is comparable to that for adjusted winds and clearly better than the inversion to true 10-m wind speed.

  1. What Limits an Altimeter's Resolution of Along-Track Geoid Slope? Insights from Saral and Cryosat

    Science.gov (United States)

    Smith, W. H. F.

    2014-12-01

    Satellite altimeter data collected along densely spaced ground tracks can map the marine gravity field, revealing the tectonic fabric of the sea floor. This application requires high accuracy of the along-track derivative of sea surface height over distances shorter than 80 km, and so is very sensitive to the instrument's range precision and any factors that produce short-scale along-track correlation of range measurement errors. To date the altimeters that have collected data over a dense network of ground tracks all acquired their largest data sets in Ku band and employing conventional (incoherent) processing. Two new altimeters go beyond conventional Ku instruments. SARAL AltiKa operates as an incoherent altimeter at Ka-band, and CryoSat collects some Ku-band data in a SAR mode to permit coherent processing for aperture synthesis and delay-Doppler calculations. The along-track range noise correlation characteristics of each of these new measurements are different from what has been seen in previous altimeters. SARAL AltiKa has a lower noise floor than pre-Cryosat Ku-band instruments and its noise spectrum shows decorrelation at different wavelengths, in partial agreement with theoretical work on speckle noise decorrelation over homogeneous surfaces. This improved noise performance results in demonstrable improvement in the resolution of geoid anomalies over small seamounts. Retracking of Cryosat's SAR mode multi-looked waveform yields a decorrelation of range errors unlike that found in conventional instruments, such that it doesn't require two-pass retracking to get the best geoid slope resolution. This is due mainly to the waveform's shape, which yields partial derivatives with respect to geophysical parameter estimates that are more nearly orthogonal than in conventional Ku-band Brown model waveforms. Further understanding of the limits on range precision in these instruments will require understanding of the heterogeneities in reflecting surfaces that are

  2. Efficient statistical classification of satellite measurements

    CERN Document Server

    Mills, Peter

    2012-01-01

    Supervised statistical classification is a vital tool for satellite image processing. It is useful not only when a discrete result, such as feature extraction or surface type, is required, but also for continuum retrievals by dividing the quantity of interest into discrete ranges. Because of the high resolution of modern satellite instruments and because of the requirement for real-time processing, any algorithm has to be fast to be useful. Here we describe an algorithm based on kernel estimation called Adaptive Gaussian Filtering that incorporates several innovations to produce superior efficiency as compared to three other popular methods: k-nearest-neighbour (KNN), Learning Vector Quantization (LVQ) and Support Vector Machines (SVM). This efficiency is gained with no compromises: accuracy is maintained, while estimates of the conditional probabilities are returned. These are useful not only to gauge the accuracy of an estimate in the absence of its true value, but also to re-calibrate a retrieved image and...

  3. Land mobile satellite propagation measurements in Japan using ETS-V satellite

    Science.gov (United States)

    Obara, Noriaki; Tanaka, Kenji; Yamamoto, Shin-Ichi; Wakana, Hiromitsu

    1993-01-01

    Propagation characteristics of land mobile satellite communications channels have been investigated actively in recent years. Information of propagation characteristics associated with multipath fading and shadowing is required to design commercial land mobile satellite communications systems, including protocol and error correction method. CRL (Communications Research Laboratory) has carried out propagation measurements using the Engineering Test Satellite-V (ETS-V) at L band (1.5 GHz) through main roads in Japan by a medium gain antenna with an autotracking capability. This paper presents the propagation statistics obtained in this campaign.

  4. Interference susceptibility measurements for an MSK satellite communication link

    Science.gov (United States)

    Kerczewski, Robert J.; Fujikawa, Gene

    1992-01-01

    The results are presented of measurements of the degradation of an MSK satellite link due to modulated and CW (unmodulated) interference. These measurements were made using a hardware based satellite communication link simulator at NASA-Lewis. The results indicate the amount of bit error rate degradation caused by CW interference as a function of frequency and power level, and the degradation caused by adjacent channel and cochannel modulated interference as a function of interference power level. Results were obtained for both the uplink case (including satellite nonlinearity) and the downlink case (linear channel).

  5. Single photon laser altimeter data processing, analysis and experimental validation

    Science.gov (United States)

    Vacek, Michael; Peca, Marek; Michalek, Vojtech; Prochazka, Ivan

    2015-10-01

    Spaceborne laser altimeters are common instruments on-board the rendezvous spacecraft. This manuscript deals with the altimeters using a single photon approach, which belongs to the family of time-of-flight range measurements. Moreover, the single photon receiver part of the altimeter may be utilized as an Earth-to-spacecraft link enabling one-way ranging, time transfer and data transfer. The single photon altimeters evaluate actual altitude through the repetitive detections of single photons of the reflected laser pulses. We propose the single photon altimeter signal processing and data mining algorithm based on the Poisson statistic filter (histogram method) and the modified Kalman filter, providing all common altimetry products (altitude, slope, background photon flux and albedo). The Kalman filter is extended for the background noise filtering, the varying slope adaptation and the non-causal extension for an abrupt slope change. Moreover, the algorithm partially removes the major drawback of a single photon altitude reading, namely that the photon detection measurement statistics must be gathered. The developed algorithm deduces the actual altitude on the basis of a single photon detection; thus, being optimal in the sense that each detected signal photon carrying altitude information is tracked and no altitude information is lost. The algorithm was tested on the simulated datasets and partially cross-probed with the experimental data collected using the developed single photon altimeter breadboard based on the microchip laser with the pulse energy on the order of microjoule and the repetition rate of several kilohertz. We demonstrated that such an altimeter configuration may be utilized for landing or hovering a small body (asteroid, comet).

  6. Digitization and Position Measurement of Astronomical Plates of Saturnian Satellites

    Science.gov (United States)

    Yan, D.; Yu, Y.; Zhang, H. Y.; Qiao, R. C.

    2014-05-01

    Using the advanced commercial scanners to digitize astronomical plates may be a simple and effective way. In this paper, we discuss the method of digitizing and astrometrically reducing six astronomical plates of Saturnian satellites, which were taken from the 1 m RCC (Ritchey Chretien Coude) telescope of Yunnan Observatory in 1988, by using the 10000XL scanner of Epson. The digitized images of the astronomical plates of Saturnian satellites are re-reduced, and the positions of Saturnian satellites based on the UCAC2 (The Second US Naval Observatory CCD Astrograph Catalog) catalogue are given. A comparison of our measured positions with the IMCCE (Institut de Mecanique Celeste et de Calcul des Ephemerides) ephemeris of Saturnian satellites shows the high quality of our measurements, which have an accuracy of 106 mas in right ascension and 89 mas in declination. Moreover, our measurements appear to be consistent with this ephemeris within only about 56 mas in right ascension and 9 mas in declination.

  7. Offshore limit of coastal ocean variability identified from hydrography and altimeter data in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Swamy, G.N.; Somayajulu, Y.K.

    In this communication, we describe a hitherto-unknown offshore limit to the coastal ocean variability signatures away from the continental shelf in the eastern Arabian Sea, based on hydrographic observations and satellite altimeter (TOPEX...

  8. Satellite measurements of the earth's crustal magnetic field

    Science.gov (United States)

    Schnetzler, C. C.

    1989-01-01

    The literature associated with the Magsat mission has evaluated the capabilities and limitations of satellite measurements of the earth's crustal magnetic field, and demonstrated that there exists a 300-3000 km magnetic field, related to major features in the earth's crust, which is primarily caused by induction. Due to its scale and sensitivity, satellite data have been useful in the development of models for such large crustal features as subduction zones, submarine platforms, continental accretion boundaries, and rifts. Attention is presently given to the lack of agreement between laboratory and satellite estimates of lower crustal magnetization.

  9. Fifth generation lithospheric magnetic field model from CHAMP satellite measurements

    OpenAIRE

    Maus, S.; Hermann Lühr; Martin Rother; Hemant, K.; Balasis, G.; Patricia Ritter; Claudia Stolle

    2007-01-01

    Six years of low-orbit CHAMP satellite magnetic measurements have provided an exceptionally high-quality data resource for lithospheric magnetic field modeling and interpretation. Here we describe the fifth-generation satellite-only magnetic field model MF5. The model extends to spherical harmonic degree 100. As a result of careful data selection, extensive corrections, filtering, and line leveling, the model has low noise levels, even if evaluated at the Earth's surface. The model is particu...

  10. A new approach to lightweight radar altimeters

    Science.gov (United States)

    Levanon, N.; Stremler, F. G.; Suomi, V. E.

    1974-01-01

    Test results and key principles are given for a radar altimeter designed for meteorological balloons. The instrument, which weighs 160 g and consumes 0.7 W, will fill a gap in meteorological sensing using balloons - an area where pressure altitude was formerly the prevailing reference. The instrument is basically a delay-lock radar utilizing a superregenerative RF stage. Long-term absolute accuracy of plus or minus 10 m and short-term stability of better than 2 m rms were measured at altitudes of 20 km.

  11. Measuring snow and glacier ice properties from satellite

    Science.gov (United States)

    KöNig, Max; Winther, Jan-Gunnar; Isaksson, Elisabeth

    2001-02-01

    Satellite remote sensing is a convenient tool for studying snow and glacier ice, allowing us to conduct research over large and otherwise inaccessible areas. This paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing. These methods have been improving with the use of new satellite sensors, like the synthetic aperture radar (SAR) during the last decade, leading to the development of new and powerful methods, such as SAR interferometry for glacier velocity, digital elevation model generation of ice sheets, or snow cover mapping. Some methods still try to overcome the limitations of present sensors, but future satellites will have much increased capability, for example, the ability to measure the whole optical spectrum or SAR sensors with multiple polarization or frequencies. Among the methods presented are the satellite-derived determination of surface albedo, snow extent, snow volume, snow grain size, surface temperature, glacier facies, glacier velocities, glacier extent, and ice sheet topography. In this review, emphasis is put on the principles and theory of each satellite remote sensing method. An extensive list of references, with an emphasis on studies from the 1990s, allows the reader to delve into specific topics.

  12. Prediction of Gravity Anomalies Over the South China and Philippine Seas from Multi-satellite Altimeter Sea Surface Heights%根据多卫星高度计海面高数据推算南中国海及菲律宾海域重力异常

    Institute of Scientific and Technical Information of China (English)

    Isaac Dadzie; 李建成; 褚永海

    2008-01-01

    Gravity anomalies on a 2.5×2.5 arc-minute grid in a non-tidal system were derived over the South China and Philippine Seas from multi-satellite altimetry data. North and east components of deflections of the vertical were computed from altimeter-derived sea surface heights at crossover locations, and gridded onto a 2.5×2.5 arc-minute resolution grid. EGM96-derived components of deflections of the vertical and gravity anomalies gridded into 2.5×2.5 arc-minute resolutions were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Inverse Vening Meinesz formula via the 1D-FFT technique to predict the gravity anomalies over the South China and Philippine Seas from the gridded altimeter-derived Components of deflections of the vertical. Statistical comparisons between the altime-ter-derived and the shipboard gravity anomalies showed that there is a root-mean-square agreement of 5.7 mgals between them.

  13. Satellite data sets for the atmospheric radiation measurement (ARM) program

    Energy Technology Data Exchange (ETDEWEB)

    Shi, L.; Bernstein, R.L. [SeaSpace Corp., San Diego, CA (United States)

    1996-04-01

    This abstract describes the type of data obtained from satellite measurements in the Atmospheric Radiation Measurement (ARM) program. The data sets have been widely used by the ARM team to derive cloud-top altitude, cloud cover, snow and ice cover, surface temperature, water vapor, and wind, vertical profiles of temperature, and continuoous observations of weather needed to track and predict severe weather.

  14. A Next Generation Radar Altimeter: The Proposed SWOT Mission

    Science.gov (United States)

    Fu, L. L.

    2014-12-01

    Conventional nadir-looking radar altimeter is based on pulse-limited footprint approach. Near a coast the pulse limited footprint is contaminated by land within the much larger radar footprint, causing data quality to decay within 10 km from a coast. In the open ocean, the instrument noise limits the detection of dynamic ocean signals to wavelengths longer than 70 km. Using the technique of radar interferometry, the proposed Surface Water and Ocean Topography (SWOT) Mission would reduce instrument noise to resolve ocean signals to 15 km in wavelength over most of the open ocean without land contamination in the coastal zone. Sea surface height would be measured in two dimensions over a swath 120 km wide across the satellite's flight path. SWOT is under development as a joint mission of NASA and the French Space Agency, CNES, with contributions from the Canadian Space Agency and the UK Space Agency. The launch is baselined for 2020. An overview of the projected mission performance for oceanographic applications will be presented. SWOT would also measure the elevation of land surface water with hydrological applications.

  15. An Orbiting Standards Platform for communication satellite system RF measurements

    Science.gov (United States)

    Wallace, R. G.; Woodruff, J. J.

    1978-01-01

    The Orbiting Standards Platform (OSP) is a proposed satellite dedicated to performing RF measurements on space communications systems. It would consist of a quasi-geostationary spacecraft containing an ensemble of calibrated RF sources and field strength meters operating in several microwave bands, and would be capable of accurately and conveniently measuring critical earth station and satellite RF performance parameters, such as EIRP, gain, figure of merit (G/T), crosspolarization, beamwidth, and sidelobe levels. The feasibility and utility of the OSP concept has been under joint study by NASA, NBS, Comsat and NTIA. A survey of potential OSP users was conducted by NTIA as part of this effort. The response to this survey, along with certain trends in satellite communications system design, indicates a growing need for such a measurement service.

  16. Results of ionospheric measurements, got on micro satellite "Compass-2"

    Science.gov (United States)

    Dokukin, Vladimir; Kuznetsov, V. D.; Garipov, G. K.; Kapustina, O.; Mikhailov, Yu. M.; Mikhailova, G. A.; Ruzhin, Yu. Ya.; Sinelnikov, V. M.; Shirokov, A. V.; Yashin, I. V.; Danilkin, V. A.; Degtyar, V. G.

    Results of measurements, executed by complex of scientific instruments of micro satellite Compass-2 in the period of 2006-2007, are presented. The project was aimed on registration and study of ionospheric effects, related to the natural and anthropogenic anomalous phenomena. The effects of interaction of solar wind with magnetosphere in the period of flare activity of the Sun and anomalous low frequency radiations, happened one day before the earthquake with magnitude 4.2, are registered. The data was got on measurements of corpuscular radiation, wide band radiations and low frequency waves along the orbit of satellite.

  17. Determination of atmospheric aerosol properties over land using satellite measurements

    NARCIS (Netherlands)

    Kokhanovsky, A.A.; Leeuw, G. de

    2009-01-01

    Mostly, aerosol properties are poorly understood because the aerosol properties are very sparse. The first workshop on the determination of atmospheric aerosol properties over land using satellite measurements is convened in Bremen, Germany. In this workshop, the topics of discussions included a var

  18. Shuttle Laser Altimeter (SLA): A pathfinder for space-based laser altimetry and lidar

    Science.gov (United States)

    Bufton, Jack; Blair, Bryan; Cavanaugh, John; Garvin, James

    1995-01-01

    The Shuttle Laser Altimeter (SLA) is a Hitchhiker experiment now being integrated for first flight on STS-72 in November 1995. Four Shuttle flights of the SLA are planned at a rate of about a flight every 18 months. They are aimed at the transition of the Goddard Space Flight Center airborne laser altimeter and lidar technology to low Earth orbit as a pathfinder for operational space-based laser remote sensing devices. Future alser altimeter sensors such as the Geoscience Laser Altimeter System (GLAS), an Earth Observing System facility instrument, and the Multi-Beam Laser Altimeter (MBLA), the land and vegetation laser altimeter for the NASA TOPSAT (Topography Satellite) Mission, will utilize systems and approaches being tested with SLA. The SLA Instrument measures the distance from the Space Shuttle to the Earth's surface by timing the two-way propagation of short (approximately 10 na noseconds) laser pulses. laser pulses at 1064 nm wavelength are generated in a laser transmitter and are detected by a telescope equipped with a silicon avalanche photodiode detector. The SLA data system makes the pulse time interval measurement to a precision of about 10 nsec and also records the temporal shape of the laser echo from the Earth's surface for interpretation of surface height distribution within the 100 m diam. sensor footprint. For example, tree height can be determined by measuring the characteristic double-pulse signature that results from a separation in time of laser backscatter from tree canopies and the underlying ground. This is accomplished with a pulse waveform digitizer that samples the detector output with an adjustable resolution of 2 nanoseconds or wider intervals in a 100 sample window centered on the return pulse echo. The digitizer makes the SLA into a high resolution surface lidar sensor. It can also be used for cloud and atmospheric aerosol lidar measurements by lengthening the sampling window and degrading the waveform resolution. Detailed test

  19. Spectral Measurements of Geosynchronous Satellites During Glint Season

    Science.gov (United States)

    Chun, F.; Tucker, R.; Weld, E.; Chun, F.; Tippets, R.

    During certain times of the year, stable geosynchronous (GEO) satellites are known to glint or exhibit a very bright specular reflection, which is easily observed through broadband photometric filters. The glints are typically brighter in the Johnson red filter compared to the Johnson blue filter. In previous years, USAFA cadets have developed and refined techniques to take, calibrate and process satellite spectral data taken using a diffraction grating on the USAFA 16-inch, f/8.2 telescope (slitless spectroscopy). To the best of our knowledge, we have not seen any published research on observing glints across the visible spectrum. We present research from an Air Force Academy senior physics capstone project on observing glints off of GEO satellites using slitless spectroscopy. We discuss the calibration of the measurements using solar analog and solar twin stars, as well as results of the spectra of a glinting GEO satellite. A key question is whether a GEO satellite glint is localized in wavelength or equally observed across the entire spectra.

  20. Web-based Altimeter Service

    Science.gov (United States)

    Callahan, P. S.; Wilson, B. D.; Xing, Z.; Raskin, R. G.

    2010-12-01

    We have developed a web-based system to allow updating and subsetting of TOPEX data. The Altimeter Service will be operated by PODAAC along with their other provision of oceanographic data. The Service could be easily expanded to other mission data. An Altimeter Service is crucial to the improvement and expanded use of altimeter data. A service is necessary for altimetry because the result of most interest - sea surface height anomaly (SSHA) - is composed of several components that are updated individually and irregularly by specialized experts. This makes it difficult for projects to provide the most up-to-date products. Some components are the subject of ongoing research, so the ability for investigators to make products for comparison or sharing is important. The service will allow investigators/producers to get their component models or processing into widespread use much more quickly. For coastal altimetry, the ability to subset the data to the area of interest and insert specialized models (e.g., tides) or data processing results is crucial. A key part of the Altimeter Service is having data producers provide updated or local models and data. In order for this to succeed, producers need to register their products with the Altimeter Service and to provide the product in a form consistent with the service update methods. We will describe the capabilities of the web service and the methods for providing new components. Currently the Service is providing TOPEX GDRs with Retracking (RGDRs) in netCDF format that has been coordinated with Jason data. Users can add new orbits, tide models, gridded geophysical fields such as mean sea surface, and along-track corrections as they become available and are installed by PODAAC. The updated fields are inserted into the netCDF files while the previous values are retained for comparison. The Service will also generate SSH and SSHA. In addition, the Service showcases a feature that plots any variable from files in netCDF. The

  1. Laser altimeter of CE-1 payloads system

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The design and operation of the Laser Altimeter of CE-1 Payloads System are presented in this paper.The paper includes the design of the system and spacecraft-level laser,the description of the emitting-system and receiving system,and the testing of the laser altimeter.The CE-1 laser altimeter is the first Chinese deep-space probe using a laser.It has one beam and operates at 1 Hz,with a nominal accuracy of 5 m.The laser altimeter has operated successfully in lunar orbit since November 28,2007.It has obtained 9120 thousand data values about the lunar altitude.

  2. Monitoring Surface Climate With its Emissivity Derived From Satellite Measurements

    Science.gov (United States)

    Zhou, Daniel K.; Larar, Allen M.; Liu, Xu

    2012-01-01

    Satellite thermal infrared (IR) spectral emissivity data have been shown to be significant for atmospheric research and monitoring the Earth fs environment. Long-term and large-scale observations needed for global monitoring and research can be supplied by satellite-based remote sensing. Presented here is the global surface IR emissivity data retrieved from the last 5 years of Infrared Atmospheric Sounding Interferometer (IASI) measurements observed from the MetOp-A satellite. Monthly mean surface properties (i.e., skin temperature T(sub s) and emissivity spectra epsilon(sub v) with a spatial resolution of 0.5x0.5-degrees latitude-longitude are produced to monitor seasonal and inter-annual variations. We demonstrate that surface epsilon(sub v) and T(sub s) retrieved with IASI measurements can be used to assist in monitoring surface weather and surface climate change. Surface epsilon(sub v) together with T(sub s) from current and future operational satellites can be utilized as a means of long-term and large-scale monitoring of Earth 's surface weather environment and associated changes.

  3. RADS Version 4: An Efficient Way to Analyse the Multi-Mission Altimeter Database

    Science.gov (United States)

    Scharroo, Remko; Leuliette, Eric; Naeije, Marc; Martin-Puig, Cristina; Pires, Nelson

    2016-08-01

    The Radar Altimeter Database System (RADS) has grown to become a mature altimeter database. Over the last 18 years it is continuously being developed, first at Delft University of Technology, now also at the National Oceanic and Atmospheric Administration (NOAA) and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).RADS now serves as a fundamental Climate Data Record for sea level. Because of the multiple users involved in vetting the data and the regular updates to the database, RADS is one of the most accurate and complete databases of satellite altimeter data around.RADS version 4 is a major change from the previous version. While the database is compatible with both software versions, the new software provides new tools, allows easier expansion, and has a better and more standardised interface.

  4. Computation of a new Mean Dynamic Topography for the Mediterranean Sea from model outputs, altimeter measurements and oceanographic in-situ data

    Directory of Open Access Journals (Sweden)

    M.-H. Rio

    2014-02-01

    Full Text Available The accurate knowledge of the ocean Mean Dynamic Topography (MDT is a crucial issue for a number of oceanographic applications and in some areas of the Mediterranean Sea, important limitations have been found pointing to the need of an upgrade. We present a new Mean Dynamic Topography (MDT that was computed for the Mediterranean Sea. It takes profit of improvements made possible by the use of extended datasets and refined processing. The updated dataset spans the 1993–2012 period and consists of: drifter velocities, altimetry data, hydrological profiles and model data. The methodology is similar to the previous MDT Rio et al. (2007. However, in Rio et al. (2007 no hydrological profiles had been taken into account. This has required the development of dedicated processing. A number of sensitivity studies have been carried out to obtain the most accurate MDT as possible. The main results from these sensitivity studies are the following: moderate impact to the choice of correlation scales but almost negligible sensitivity to the choice of the first guess (model solution. A systematic external validation to independent data has been made to evaluate the performance of the new MDT. Compared to previous version, SMDT-MED-2014 features shorter scales structures, which results in an altimeter velocity variance closer to the observed velocity variance and, at the same time, gives better Taylor skills.

  5. Air quality performed with satellite measurement within the QUITSAT project

    Science.gov (United States)

    Masieri, Samuele; Petritoli, Andrea; Premuda, Margarita; Kostadinov, Ivan; Bortoli, Daniele; Ravegnani, Fabrizio; Giovanelli, Giorgio

    Ground pollutants monitoring, using satellite observation, represents an interesting and high potential approach to air quality that could be inserted into Global monitoring systems. The QUITSAT Italian pilot project (air QUality with Integration of ground based and SAtellite measurements and chemical Transport and multiphase model), funded by the Italian Space Agency (ASI), proposes a new approach producing some interesting results in this frame. The approach focuses in the integration of the satellite observations (ENVISAT/SCIAMACHY and AURA/OMI) with the outputs of the GAMES (Gas Aerosol Modelling Evaluation System) chemical transport model, to provide the evaluation of the tropospheric profiles of some atmo-spheric compounds such as NO2 , O3 , HCHO and SO2 . This activity appears to be very useful to retrieve the surface concentration of trace gases from tropospheric columns of atmospheric compounds obtained with satellite instrumentation. The comparison with the in situ analyzer network over the Po' Valley shows a good correlation between the two data set. The corre-spondence can be improved taking into account also concentration gradients between different stations, classifying the ground base stations according to their rural or urban characteristics and considering the general orography of the ground. Results and methodology are presented and discussed.

  6. Simulation of Full-Waveform Laser Altimeter Echowaveform

    Science.gov (United States)

    Lv, Y.; Tong, X. H.; Liu, S. J.; Xie, H.; Luan, K. F.; Liu, J.

    2016-06-01

    Change of globe surface height is an important factor to study human living environment. The Geoscience Laser Altimeter System (GLAS) on ICESat is the first laser-ranging instrument for continuous global observations of the Earth. In order to have a comprehensive understanding of full-waveform laser altimeter, this study simulated the operating mode of ICESat and modeled different terrains' (platform terrain, slope terrain, and artificial terrain) echo waveforms based on the radar equation. By changing the characteristics of the system and the targets, numerical echo waveforms can be achieved. Hereafter, we mainly discussed the factors affecting the amplitude and size (width) of the echoes. The experimental results implied that the slope of the terrain, backscattering coefficient and reflectivity, target height, target position in the footprint and area reacted with the pulse all can affect the energy distribution of the echo waveform and the receiving time. Finally, Gaussian decomposition is utilized to decompose the echo waveform. From the experiment, it can be noted that the factors which can affect the echo waveform and by this way we can know more about large footprint full-waveform satellite laser altimeter.

  7. Cloud and Thermodynamic Parameters Retrieved from Satellite Ultraspectral Infrared Measurements

    Science.gov (United States)

    Zhou, Daniel K.; Smith, William L.; Larar, Allen M.; Liu, Xu; Taylor, Jonathan P.; Schluessel, Peter; Strow, L. Larrabee; Mango, Stephen A.

    2008-01-01

    Atmospheric-thermodynamic parameters and surface properties are basic meteorological parameters for weather forecasting. A physical geophysical parameter retrieval scheme dealing with cloudy and cloud-free radiance observed with satellite ultraspectral infrared sounders has been developed and applied to the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric InfraRed Sounder (AIRS). The retrieved parameters presented herein are from radiance data gathered during the Joint Airborne IASI Validation Experiment (JAIVEx). JAIVEx provided intensive aircraft observations obtained from airborne Fourier Transform Spectrometer (FTS) systems, in-situ measurements, and dedicated dropsonde and radiosonde measurements for the validation of the IASI products. Here, IASI atmospheric profile retrievals are compared with those obtained from dedicated dropsondes, radiosondes, and the airborne FTS system. The IASI examples presented here demonstrate the ability to retrieve fine-scale horizontal features with high vertical resolution from satellite ultraspectral sounder radiance spectra.

  8. Ice Surface Elevation Changes in East Antarctica from Satellite Altimetry

    Science.gov (United States)

    Zwally, H. Jay; Brenner, Anita C.; DiMarzio, John

    1998-01-01

    Estimates of the overall mass balance and seasonal and inter-annual variations in the surface mass balance are obtainable from time-series of ice surface elevations measured by satellite altimetry. Beginning in 2001, NASA's ICESat laser altimeter and lidar mission will significantly improve the range accuracy, the orbit accuracy, and the spatial coverage for measurement of ice sheet elevations (to 86 S) , as compared to previous radar altimeters designed for ocean measurements The radar altimeters on Seasat and Geosat provided ice sheet measurements to 72 S, and on ERS-1 and ERS-2 to 81 S. Although radar altimetry has significant limitations in coverage (due to loss of tracking) and accuracy over sloping surfaces, information on ice-sheet surface-elevation changes has been derived for parts of Antarctica. Recently, the accuracy of the ice measurements by Seasat (3 months of 1978) and Geosat (1985 to 1989) have been improved by new calculations of the satellite orbit heights and other altimeter corrections. Residual orbit errors and inter-satellite biases are evaluated by crossover analysis and by global adjustments to an ocean surface derived from altimeter data. The standard deviation of the orbit error is less than 9 cm, and the long-term trend in the error appears to be less than 1 cm/yr. Orbit errors can be further reduced by adjustment to the ocean surface, but false signals of several cm/yr may be also introduced by the adjustments. These false signals are caused mainly by residual errors in the altimeter corrections over the ocean, and secondary by real changes in the ocean surface elevation. Maps of ice sheet elevation changes north of 72 S are derived from Seasat-Geosat crossovers and from 4.5 years of Geosat crossovers. A notable ice thinning rate of about 50 cm/yr is found at elevations below 2200 meters between 70 and 72 S to the East of the Amery ice shelf, in both the Seasat-Geosat and Geosat-Geosat time intervals Above 2200 meters, to the ridge

  9. NOx emission trends in megacities derived from satellite measurements

    Science.gov (United States)

    Konovalov, Igor; Beekmann, Matthias; Richter, Andreas

    2010-05-01

    The effects of air pollutant emissions on both local air quality in megacities and composition of the atmosphere on regional and global scales are currently an important issue of atmospheric researches. In order to properly evaluate these effects, atmospheric models should be provided with accurate information on emissions of major air pollutants. However, such information is frequently very uncertain, as it is documented in literature. The quantification of emissions and related effects is an especially difficult task in the case of developing countries. Recently, it has been demonstrated that satellite measurements of nitrogen dioxide (NO2) can be used as a source of independent information on NOx emissions. In particular, the satellite measurements were used in our earlier studies to improve spatial allocation of NOx emissions, to estimate multi-annual changes of NOx emissions on regional scales and to validate data of traditional emission inventories (see Ref. 1, 2). The goals of the present study are (1) developing an efficient method for estimation of NOx emissions trend in megacity regions by using satellite measurements and an inverse modeling technique and (2) obtaining independent estimates of NOx emission trends in several megacities in Europe and the Middle East in the period from 1996 to 2008. The study is based on the synergetic use of the data for tropospheric NO2 column amounts derived from the long-term GOME and SCIAMACHY measurements and simulations performed by the CHIMERE chemistry transport model. We performed the analysis involving methods of different complexity ranging from estimation of linear trends in the tropospheric NO2 columns retrieved from satellite measurements to evaluation of nonlinear trends in NOx emission estimates obtained with the inverse modeling approach, which, in the given case, involves only very simple and transparent formulations. The most challenging part of the study is the nonlinear trend estimation, which is

  10. Effects of tropospheric and ionospheric refraction errors in the utilization of GEOS-C altimeter data

    Science.gov (United States)

    Goad, C. C.

    1977-01-01

    The effects of tropospheric and ionospheric refraction errors are analyzed for the GEOS-C altimeter project in terms of their resultant effects on C-band orbits and the altimeter measurement itself. Operational procedures using surface meteorological measurements at ground stations and monthly means for ocean surface conditions are assumed, with no corrections made for ionospheric effects. Effects on the orbit height due to tropospheric errors are approximately 15 cm for single pass short arcs (such as for calibration) and 10 cm for global orbits of one revolution. Orbit height errors due to neglect of the ionosphere have an amplitude of approximately 40 cm when the orbits are determined from C-band range data with predominantly daylight tracking. Altimeter measurement errors are approximately 10 cm due to residual tropospheric refraction correction errors. Ionospheric effects on the altimeter range measurement are also on the order of 10 cm during the GEOS-C launch and early operation period.

  11. A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland

    Science.gov (United States)

    Gray, Laurence; Burgess, David; Copland, Luke; Dunse, Thorben; Langley, Kirsty; Moholdt, Geir

    2017-05-01

    We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration-validation sites on Devon Ice Cap and western Greenland. Comparisons are included for both the heights derived from the first return (the point-of-closest-approach or POCA) and heights derived from delayed waveform returns (swath processing). While swath-processed heights are normally less precise than edited POCA heights, e.g. standard deviations of ˜ 3 and ˜ 1.5 m respectively for the western Greenland site, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction ( ˜ 0.0075° ± 0.0025°), or equivalent phase correction ( ˜ 0.0435 ± 0.0145 radians), provides an improved calibration of the interferometric SARIn mode. We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms and that it is possible to detect and measure the height of summer supraglacial lakes in western Greenland. A supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near-normal incidence. This provides an ideal situation for swath processing and we demonstrate a height precision of ˜ 0.5 m for two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending passes, which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite imagery and be helpful as proxy indicators for surface melt around

  12. Regional applicability of forest height and aboveground biomass models for the Geoscience Laser Altimeter System

    Science.gov (United States)

    Dirk Pflugmacher; Warren B. Cohen; Robert E. Kennedy; Michael. Lefsky

    2008-01-01

    Accurate estimates of forest aboveground biomass are needed to reduce uncertainties in global and regional terrestrial carbon fluxes. In this study we investigated the utility of the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land Elevation Satellite for large-scale biomass inventories. GLAS is the first spaceborne lidar sensor that will...

  13. Measurement of sea ice and icebergs topography using satellite imagery

    Science.gov (United States)

    Zakharov, I.; Power, D.; Prasad, S.

    2016-12-01

    Sea ice topography represents geospatial information on the three-dimensional geometrical attributes of the ice surface including height and shape of various ice features. The features interest consist of deformed (pressure ridges, rubbles and hummocks) and level sea ice as well as glacial ice. Sea ice topography is important for scientific research and climate studies because it helps characterise ice volume and thickness and it influences the near-surface atmospheric transport by impacting the drag coefficients. It also represents critical information to marine operational applications, such as ships navigation and risks assessment for offshore infrastructures. The several methods were used to measure sea ice topography from a single satellite image as well as multiple images. The techniques based on the single image, acquired by optical or synthetic aperture radar (SAR) satellites, derive the height and shape information from shadow and shading. Optical stereo images acquired by very high resolution (0.5 m) satellites were used to extract highly detailed digital elevation model (DEM). SAR imagery allowed extraction of DEM using stereo-radargrammetry and interferometry. The images from optical satellites WorldView, Pleiades, GeoEye, Spot, and Landsat-8 were used to measure topography of sea ice deformation features and glacial ice including icebergs and ice islands. These features were mapped in regions of the Central Arctic, Baffin Bay and the coast of Greenland. SAR imagery including interferometric TanDEM-X data and full polarimetric Radarsat-2 were used to extract ridge frequency and measure spatial parameters of glacial features. The accuracy was evaluated by comparison of the results from different methods demonstrating their strengths and limitations. Ridge height and frequency were also compared with the high resolution results from the Los Alamos sea ice model (CICE), regionally implemented for Baffin Bay and the Labrador Sea.

  14. Evaluation of Aerosol Properties in GCMs using Satellite Measurements

    Science.gov (United States)

    Wang, Y.; Jiang, J. H.; Su, H.; Zhang, H.

    2015-12-01

    Atmospheric aerosols from natural or anthropogenic sources have profound impacts on the regional and global climate. Currently the radiative forcing of aerosols predicted by global climate models remains highly uncertain, representing the largest uncertainty in climate predictions. The uncertainty mainly arises from the complicated aerosol chemical and physical properties, coarse emission inventories for pre-cursor gases as well as unrealistic representations of aerosol activation and cloud processing in global climate models. In this study, we will utilize multiple satellite measurements including MODIS, MISR and CALIPSO to quantitatively evaluate aerosol simulations from climate models. Our analyses show that the global means in AOD climatology from NCAR CAM5 and GFDL AM3 simulations are comparable with satellite measurements. However, the overall correlation coefficient between the AOD spatial patterns from CAM5 and satellite is only 0.4. Moreover, at finer scales, the magnitude of AOD in CAM5 is much lower than satellite measurements for most of the non-dust regions, especially over East Asia. GFDL AM3 shows better AOD simulations over East Asia. The underestimated AOD over remote maritime areas in CAM5 was attributed to the unrealistic wet removal processes in convective clouds of CAM5. Over continents, biases on AOD could stem from underestimations in the emissions inventory and unresolved sub-grid variations of relative humidity due to the model's coarse resolution. Uncertainty from emission inventory over developing countries in East Asia will be assessed using the newly updated Regional Emission inventory in Asia (REAS) and Multi-resolution Emission Inventory in China (MEIC) in the model simulations.

  15. Land-mobile-satellite fade measurements in Australia

    Science.gov (United States)

    Vogel, Wolfhard J.; Goldhirsh, Julius; Hase, Yoshihiro

    1992-01-01

    Attenuation measurements were implemented at L-band (1.5 GHz) in southeastern Australia during an 11-day period in October 1988 as part of a continuing examination of the propagation effects due to roadside trees and terrain for mobile-satellite service. Beacon transmissions from the geostationary ETS-V and IPORS satellites were observed. The Australian campaign expanded to another continent our Mobile Satellite Service data base of measurements executed in the eastern and southwestern United States regions. An empirical fade distribution model based on U.S. data predicted the Australian results with errors generally less than 1 dB in the 1-20 percent probability region. Directive antennas are shown to suffer deeper fades under severe shadowing conditions (3 dB excess at 4 percent), the equal-probability isolation between co- and cross-polarized transmissions deteriorated to 10 dB at the 5 dB fade level, and antenna diversity reception may reduce unavailability of the system by a factor of 2-8.

  16. Evaluation of CHAMP Satellite Orbit with SLR Measurements

    Institute of Scientific and Technical Information of China (English)

    QIN Xianping; YANG Yuanxi

    2005-01-01

    The technique of Evaluating CHAMP satellite orbit with SLR measurements is presented. As an independent evaluation of the orbit solution, SLR data observed from January 1 to 16, 2002 are processed to compute the residuals after fixing the GFZ's post science orbits solutions. The SLR residuals are computed as the differences of the SLR measurements minus the corresponding distances between the SLR station and the GPS-derived orbit positions. On the basis of the SLR residuals analysis, it is found that the accuracy of GFZ's post science orbits is better than 10 em and that there is no systematic error in GFZ's post science orbits.

  17. Intercomparison of desert dust optical depth from satellite measurements

    Directory of Open Access Journals (Sweden)

    E. Carboni

    2012-08-01

    Full Text Available This work provides a comparison of satellite retrievals of Saharan desert dust aerosol optical depth (AOD during a strong dust event through March 2006. In this event, a large dust plume was transported over desert, vegetated, and ocean surfaces. The aim is to identify the differences between current datasets. The satellite instruments considered are AATSR, AIRS, MERIS, MISR, MODIS, OMI, POLDER, and SEVIRI. An interesting aspect is that the different algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. These include multi-angle approaches (MISR, AATSR, polarisation measurements (POLDER, single-view approaches using solar wavelengths (OMI, MODIS, and the thermal infrared spectral region (SEVIRI, AIRS. Differences between instruments, together with the comparison of different retrieval algorithms applied to measurements from the same instrument, provide a unique insight into the performance and characteristics of the various techniques employed. As well as the intercomparison between different satellite products, the AODs have also been compared to co-located AERONET data. Despite the fact that the agreement between satellite and AERONET AODs is reasonably good for all of the datasets, there are significant differences between them when compared to each other, especially over land. These differences are partially due to differences in the algorithms, such as assumptions about aerosol model and surface properties. However, in this comparison of spatially and temporally averaged data, it is important to note that differences in sampling, related to the actual footprint of each instrument on the heterogeneous aerosol field, cloud identification and the quality control flags of each dataset can be an important issue.

  18. Eruption column height: a comparison between ground and satellite measurements

    Science.gov (United States)

    Scollo, Simona; Prestifilippo, Michele; Pecora, Emilio; Corradini, Stefano; Merucci, Luca; Spata, Gaetano; Coltelli, Mauro

    2014-05-01

    The eruption column height estimation is an essential parameter to evaluate the total mass eruption rate, the gas and aerosol plume dispersal and retrievals. The column height may be estimated using different systems (e.g. satellite, aircraft and ground observations) which may present marked differences. In this work we use the calibrated images collected by the video-surveillance system of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, from the visible camera located in Catania, 27 km from the vent. The analysis is carried out on twenty lava fountains from the New South East Crater during the recent Etna explosive activity. Firstly, we calibrated the camera to estimate its intrinsic parameters and the full camera model. Furthermore, we selected the images which recorded the maximum phase of the eruptive activity. Hence, we applied an appropriate correction to take into account the wind effect. The column height was also evaluated using SEVIRI and MODIS satellite images collected at the same time of the video camera measurements. The satellite column height retrievals is realized by comparing the 11 μm brightness temperature of the most opaque plume pixels with the atmospheric temperature profile measured at Trapani WMO Meteo station (the nearest WMO station to the Etnean area). The comparison between satellite and ground data show a good agreement and the column altitudes ranges between 7.5 and 9 km (upper limit of the camera system). For nine events we evaluated also the thickness of the volcanic plumes in the umbrella region (near the vent) which ranges between 2 and 3 km. The proposed approach help to quantitatively evaluate the column height that may be used by volcanic ash dispersal and sedimentation models for improving forecasts and reducing risks to aviation during volcanic crisis.

  19. Detection of Solid Tides on Europa Through Ground-Tracking of a Low-Altitude, Altimeter- Equipped Orbiter

    Science.gov (United States)

    Casotto, S.; Padovan, S.; Bardella, M.

    2007-12-01

    The possibility of detecting a global liquid ocean beneath the icy crust of Europa without the use of landers or ice penetrators rests on the measurement of the Love numbers h2 and k2. These are respectively related to the radial deformation of the surface and the consequent tidally-induced variation of the gravitational field of this icy satellite. Depending on the rigidity of the icy crust, the response of the Europan surface to the tidal forces gives an indication of the depth of a possible subsurface ocean. Previous studies in this area have addressed the detection of tidal surface deformations through the analysis of the tidally induced orbital perturbations of a Europan orbiter. As a preliminary study in preparation for future missions to Europa, as in the LAPLACE proposal to the European Space Agency, the approach followed here is to introduce the presence of an onboard altimeter. In this study we then generate synthetic measurements taken from an altimeter-equipped, low-altitude orbiter, supplemented with Earth-based tracking of the orbiter. For simplicity, ground-tracking is simulated as a range data-type. Altimeter measurements are simulated using parameters based on available models for the interior of Europa derived from Galileo mission data. Reference orbits were obtained by numerical investigations of the dynamically unstable near-Europa environment. Orbits were found to be stable over periods of approximately one to three months at altitudes of 100 km and inclinations varying from 75 degrees to 105 degrees. The measurements are consequently simulated over a period of one to two months. Under the hypothesis that Europan gravity field information of sufficient accuracy has been obtained in the first phase of the mission, the simulations address the detection of the solid tide related Love parameters h2 and k2. Results of this sensitivity study will be presented for a variety of orbital configurations with the aim to help in the design of future Europa

  20. The Gulf Stream front - A comparison between Seasat altimeter observations and theory

    Science.gov (United States)

    Kao, T. W.; Cheney, R. E.

    1982-01-01

    A quantitative comparison is made between a model which gives a universal shape and width of the sea surface height rise anomaly across the Gulf Stream and six Gulf Stream altimeter profiles representing a range of conditions. The closeness of the fit obtained reinforces the validity of both the model and the role of satellite altimetry in ocean dynamics. Further comparisons of the data with the theories of Stommel (1966) and Charney (1955) show that the former is incomplete, accepting only one altimeter-derived parameter.

  1. Scenarios and performance measures for advanced ISDN satellite design and experiments

    Science.gov (United States)

    Pepin, Gerard R.

    1991-01-01

    Described here are the contemplated input and expected output for the Interim Service Integrated Services Digital Network (ISDN) Satellite (ISIS) and Full Service ISDN Satellite (FSIS) Models. The discrete event simulations of these models are presented with specific scenarios that stress ISDN satellite parameters. Performance measure criteria are presented for evaluating the advanced ISDN communication satellite designs of the NASA Satellite Communications Research (SCAR) Program.

  2. Study on Atmospheric Refraction Delay Correction for Satellite Laser Altimeter System%星载激光测高系统的大气折射延迟改正模型研究

    Institute of Scientific and Technical Information of China (English)

    李松; 肖建明; 马跃; 周辉; 郭想

    2013-01-01

    星载激光测高仪通过测量从卫星平台发射的激光脉冲在卫星与地面激光脚点之间的渡越时间计算两者之间的距离.由于光束经过大气层时发生的折射,导致卫星激光测高系统典型的与大气延迟相关的测距误差在数米量级.讨论了大气折射延迟修正的理论与方法,分析比较了各种大气折射率模型,以全球首个对地观测星载激光测高仪系统GLAS系统为例,给出了各种折射率模型的计算偏差,发现在常见温度和湿度范围内Owens375模型是一种精度较高的简化折射率模型;计算了GLAS系统高度角偏离天顶方向不超过10°的情况下,使用简单映射函数与CfA2.2映射函数模型的值,发现其差异不超过0.5 mm.%Satellite laser altimetry system(SLR) measures the distance between the satellite and the surface of the earth by figuring out the transit time of laser pulse. The characteristics ranging error is few meters for a SLR because of the atmospheric refraction delay. The theory and method of atmospheric refraction delay correction are discussed. The various models of atmospheric refraction are analyzed and compared. The atmospheric refraction delay based on different models by using GLAS's parameters is calculated. It shows that the model of Owens 375 is with great precise and simplified in most temperature and humidity conditions. The refraction delay corrections in the condition that altitude angle within 10?are calculated by using a simplified mapping function and CfA2. 2, and diffrences between them is only 0. 5 mm.

  3. Transportable IOT measurement station for direct-broadcast satellites

    Science.gov (United States)

    Ulbricht, Michael

    A transportable 11.7-12.5-GHz flux-density measurement facility for use in the in-orbit testing (IOT) of the FRG TV-Sat direct-broadcast satellites is described. Major components include a 1.2-m-diameter antenna, the fluxmeter, a radiometer to determine atmospheric attenuation, a weather station, and a control and data-processing computer; all of the components are mounted on a 5.10 x 2.35 x 2.70-m trailer. IOT performance parameters include gain/temperature ratio 15.9 dB/K, measurement range -97 to -117 dBW/sq m, measurement accuracy less than 0.5 dB rms, and measurement rate 250-650 msec. Photographs and a block diagram are provided.

  4. On retrieving sea ice freeboard from ICESat laser altimeter

    Science.gov (United States)

    Khvorostovsky, Kirill; Rampal, Pierre

    2016-10-01

    Sea ice freeboard derived from satellite altimetry is the basis for the estimation of sea ice thickness using the assumption of hydrostatic equilibrium. High accuracy of altimeter measurements and freeboard retrieval procedure are, therefore, required. As of today, two approaches for estimating the freeboard using laser altimeter measurements from Ice, Cloud, and land Elevation Satellite (ICESat), referred to as tie points (TP) and lowest-level elevation (LLE) methods, have been developed and applied in different studies. We reproduced these methods for the ICESat observation periods (2003-2008) in order to assess and analyse the sources of differences found in the retrieved freeboard and corresponding thickness estimates of the Arctic sea ice as produced by the Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC). Three main factors are found to affect the freeboard differences when applying these methods: (a) the approach used for calculation of the local sea surface references in leads (TP or LLE methods), (b) the along-track averaging scales used for this calculation, and (c) the corrections for lead width relative to the ICESat footprint and for snow depth accumulated in refrozen leads. The LLE method with 100 km averaging scale, as used to produce the GSFC data set, and the LLE method with a shorter averaging scale of 25 km both give larger freeboard estimates comparing to those derived by applying the TP method with 25 km averaging scale as used for the JPL product. Two factors, (a) and (b), contribute to the freeboard differences in approximately equal proportions, and their combined effect is, on average, about 6-7 cm. The effect of using different methods varies spatially: the LLE method tends to give lower freeboards (by up to 15 cm) over the thick multiyear ice and higher freeboards (by up to 10 cm) over first-year ice and the thin part of multiyear ice; the higher freeboards dominate. We show that the freeboard underestimation

  5. Robust Control for the Mercury Laser Altimeter

    Science.gov (United States)

    Rosenberg, Jacob S.

    2006-01-01

    Mercury Laser Altimeter Science Algorithms is a software system for controlling the laser altimeter aboard the Messenger spacecraft, which is to enter into orbit about Mercury in 2011. The software will control the altimeter by dynamically modifying hardware inputs for gain, threshold, channel-disable flags, range-window start location, and range-window width, by using ranging information provided by the spacecraft and noise counts from instrument hardware. In addition, because of severe bandwidth restrictions, the software also selects returns for downlink.

  6. Measuring thermal budgets of active volcanoes by satellite remote sensing

    Science.gov (United States)

    Glaze, L.; Francis, P. W.; Rothery, D. A.

    1989-01-01

    Thematic Mapper measurements of the total radiant energy flux Q at Lascar volcano in north Chile for December 1984 are reported. The results are consistent with the earlier suggestion that a lava lake is the source of a reported thermal budget anomaly, and with values for 1985-1986 that are much lower, suggesting that fumarolic activity was then a more likely heat source. The results show that satellite remote sensing may be used to monitor the activity of a volcano quantitatively, in a way not possible by conventional ground studies, and may provide a method for predicting eruptions.

  7. Total ozone retrieval from satellite multichannel filter radiometer measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lovill, J.E.; Sullivan, T.J.; Weichel, R.L.; Ellis, J.S.; Huebel, J.G.; Korver, J.; Weidhaas, P.P.; Phelps, F.A.

    1978-05-25

    A total ozone retrieval model has been developed to process radiance data gathered by a satellite-mounted multichannel filter radiometer (MFR). Extensive effort went into theoretical radiative transfer modeling, a retrieval scheme was developed, and the technique was applied to the MFR radiance measurements. The high quality of the total ozone retrieval results was determined through comparisons with Dobson measurements. Included in the report are global total ozone maps for 20 days between May 12 and July 5, 1977. A comparison of MFR results for 13 days in June 1977 with Dobson spectrophotometer measurements of ozone for the same period showed good agreement: there was a root-mean-square difference of 6.2% (equivalent to 20.2 m.atm.cm). The estimated global total ozone value for June 1977 (296 m.atm.cm) was in good agreement with satellite backscatter ultraviolet data for June 1970 (304 m.atm.cm) and June 1971 (preliminary data--299 m.atm.cm).

  8. A next generation altimeter for mapping the sea surface height variability: opportunities and challenges

    Science.gov (United States)

    Fu, Lee-Lueng; Morrow, Rosemary

    2016-07-01

    The global observations of the sea surface height (SSH) have revolutionized oceanography since the beginning of precision radar altimetry in the early 1990s. For the first time we have continuous records of SSH with spatial and temporal sampling for detecting the global mean sea level rise, the waxing and waning of El Niño, and the ocean circulation from gyres to ocean eddies. The limit of spatial resolution of the present constellation of radar altimeters in mapping SSH variability is approaching 100 km (in wavelength) with 3 or more simultaneous altimetric satellites in orbit. At scales shorter than 100 km, the circulation contains substantial amount of kinetic energy in currents, eddies and fronts that are responsible for the stirring and mixing of the ocean, especially from the vertical exchange of the upper ocean with the deep. A mission currently in development will use the technique of radar interferometry for making high-resolution measurement of the height of water over the ocean as well as on land. It is called Surface Water and Ocean Topography (SWOT), which is a joint mission of US NASA and French CNES, with contributions from Canada and UK. SWOT promises the detection of SSH at scales approaching 15 km, depending on the sea state. SWOT will make SSH measurement over a swath of 120 km with a nadir gap of 20 km in a 21-day repeat orbit. A conventional radar altimeter will provide measurement along the nadir. This is an exploratory mission with applications in oceanography and hydrology. The increased spatial resolution offers an opportunity to study ocean surface processes to address important questions about the ocean circulation. However, the limited temporal sampling poses challenges to map the evolution of the ocean variability that changes rapidly at the small scales. The measurement technique and the development of the mission will be presented with emphasis on its science program with outlook on the opportunities and challenges.

  9. A digital elevation model of the Greenland ice sheet and validation with airborne laser altimeter data

    Science.gov (United States)

    Bamber, Jonathan L.; Ekholm, Simon; Krabill, William B.

    1997-01-01

    A 2.5 km resolution digital elevation model (DEM) of the Greenland ice sheet was produced from the 336 days of the geodetic phase of ERS-1. During this period the altimeter was operating in ice-mode over land surfaces providing improved tracking around the margins of the ice sheet. Combined with the high density of tracks during the geodetic phase, a unique data set was available for deriving a DEM of the whole ice sheet. The errors present in the altimeter data were investigated via a comparison with airborne laser altimeter data obtained for the southern half of Greenland. Comparison with coincident satellite data showed a correlation with surface slope. An explanation for the behavior of the bias as a function of surface slope is given in terms of the pattern of surface roughness on the ice sheet.

  10. Global distribution of pauses observed with satellite measurements

    Indian Academy of Sciences (India)

    M Venkat Ratnam; P Kishore; Isabella Velicogna

    2013-04-01

    Several studies have been carried out on the tropopause, stratopause, and mesopause (collectively termed as ‘pauses’) independently; however, all the pauses have not been studied together. We present global distribution of altitudes and temperatures of these pauses observed with long-term space borne high resolution measurements of Global Positioning System (GPS) Radio Occultation (RO) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) aboard Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite. Here we study the commonality and differences observed in the variability of all the pauses. We also examined how good other datasets will represent these features among (and in between) different satellite measurements, re-analysis, and model data. Hemispheric differences observed in all the pauses are also reported. In addition, we show that asymmetries between northern and southern hemispheres continue up to the mesopause. We analyze inter and intra-seasonal variations and long-term trends of these pauses at different latitudes. Finally, a new reference temperature profile is shown from the ground to 110 km for tropical, mid-latitudes, and polar latitudes for both northern and southern hemispheres.

  11. A note on radar altimeter signatures of internal solitary waves in the ocean

    Science.gov (United States)

    da Silva, J. C. B.; Cerqueira, A. L. F.

    2016-10-01

    It is well known that Internal Waves of tidal frequency (i.e. Internal Tides) are successfully detected in seasurface height (SSH) by satellite altimetry [1]. Shorter period Internal Solitary Waves (ISWs), whose periods are an order of magnitude smaller than tidal internal waves, are however generally assumed too small to be detected with standard altimeters (at low sampling rates, i.e. 1 Hz). This is because the Radar Altimeter (RA) footprint is somewhat larger, or of similar size at best, than the ISWs typical wavelengths. Here it will be demonstrated that new generation high sampling rate satellite altimetry data (i.e. 20 Hz) hold a variety of short-period signatures that are consistent with surface manifestations of ISWs in the ocean. Our observational method is based on satellite synergy with imaging sensors such as Synthetic Aperture Radar (SAR) and other high-resolution optical sensors (e.g. 250m resolution MODIS images) with which ISWs are unambiguously recognized. A first order commonly accepted ISW radar imaging mechanism is based on hydrodynamic modulation models [2] [3] in which the straining of surface waves due to ISW orbital currents is known to cause modulation of decimeter-scale surface waves, which have group velocities close to the IW phase velocity. This effect can be readily demonstrated by measurements of wind wave slope variances associated with short-period ISWs, as accomplished in the pioneer work of Hughes and Grant [4]. Mean square slope can be estimated from nadir looking RAs using a geometric optics (specular) scattering model [5][6][7], and directly obtained from normalized backscatter (sigma0) along-track records. We use differential scattering from the dual-band (Ku- and C-bands) microwave pulses of the Jason- 2 high-rate RA to isolate the contribution of small-scale surface waves to mean square slope. The differenced altimeter mean square slope estimate, derived for the nominal wave number range 40-100 rad/m, is then used to detect

  12. Improving maps of ice-sheet surface elevation change using combined laser altimeter and stereoscopic elevation model data

    DEFF Research Database (Denmark)

    Fredenslund Levinsen, Joanna; Howat, I. M.; Tscherning, C. C.

    2013-01-01

    laser altimeters have relatively low errors but are spatially limited to the ground tracks, while DEMs have larger errors but provide spatially continuous surfaces. The principle of our method is to fit the DEM surface to the altimeter point clouds in time and space to minimize the DEM errors and use......We combine the complementary characteristics of laser altimeter data and stereoscopic digital elevation models (DEMs) to construct high-resolution (_100 m) maps of surface elevations and elevation changes over rapidly changing outlet glaciers in Greenland. Measurements from spaceborne and airborne...... that surface to extrapolate elevations away from altimeter flight lines. This reduces the DEM registration errors and fills the gap between the altimeter paths. We use data from ICESat and ATM as well as SPOT 5 DEMs from 2007 and 2008 and apply them to the outlet glaciers Jakobshavn Isbræ (JI...

  13. Strategies for estimating the marine geoid from altimeter data

    Science.gov (United States)

    Argentiero, P.; Kahn, W. D.; Garza-Robles, R.

    1974-01-01

    In processing altimeter data from a spacecraft borne altimeter to estimate the fine structure of the marine geoid, a problem is encountered. In order to describe the geoid fine structure, a large number of parameters must be employed and it is not possible to simultaneously estimate all of them. Unless the parameterization exhibits good orthogonality in the data, serious aliasing results. From simulation studies it has been found that amongst several competing parameterizations, the mean free air gravity anomaly model (i.e., Stokes' formula) exhibited promising geoid recovery characteristics. Using covariance analysis techniques, this report provides quantitative measures of the orthogonality properties associated with the above mentioned parameterization. It has been determined that a 5 deg x 5 deg area mean free air gravity anomaly can be estimated with an uncertainty of 1 mgal (40 cm undulation) provided that all free air gravity anomalies within a spherical radius of 10 arc degrees are simultaneously estimated.

  14. The use of satellites in gravity field determination and model adjustment

    Science.gov (United States)

    Visser, Petrus Nicolaas Anna Maria

    1992-06-01

    Methods to improve gravity field models of the Earth with available data from satellite observations are proposed and discussed. In principle, all types of satellite observations mentioned give information of the satellite orbit perturbations and in conjunction the Earth's gravity field, because the satellite orbits are affected most by the Earth's gravity field. Therefore, two subjects are addressed: representation forms of the gravity field of the Earth and the theory of satellite orbit perturbations. An analytical orbit perturbation theory is presented and shown to be sufficiently accurate for describing satellite orbit perturbations if certain conditions are fulfilled. Gravity field adjustment experiments using the analytical orbit perturbation theory are discussed using real satellite observations. These observations consisted of Seasat laser range measurements and crossover differences, and of Geosat altimeter measurements and crossover differences. A look into the future, particularly relating to the ARISTOTELES (Applications and Research Involving Space Techniques for the Observation of the Earth's field from Low Earth Orbit Spacecraft) mission, is given.

  15. Accuracy of Satellite-Measured Wave Heights in the Australian Region for Wave Power Applications

    Science.gov (United States)

    Meath, Sian E.; Aye, Lu; Haritos, Nicholas

    2008-01-01

    This article focuses on the accuracy of satellite data, which may then be used in wave power applications. The satellite data are compared to data from wave buoys, which are currently considered to be the most accurate of the devices available for measuring wave characteristics. This article presents an analysis of satellite- (Topex/Poseidon) and…

  16. Ocean tidal signals in observatory and satellite magnetic measurements

    DEFF Research Database (Denmark)

    Maus, S.; Kuvshinov, A.

    2004-01-01

    Ocean flow moves sea water through the Earth's magnetic field, inducing electric fields, currents and secondary magnetic fields. These motionally induced magnetic fields have a potential for the remote sensing of ocean flow variability. A first goal must be to gain a better understanding...... of magnetic field generation by tidal ocean flow. We predict the motionally induced magnetic fields for the six major tidal constituents and compare their amplitudes with the spectra of night time observatory and satellite magnetic measurements for the Indian Ocean. The magnetic variations at the solar S2, K1......, and P1 periods turn out to be dominated by unrelated external fields. In contrast, observed lunar M2 and N2 tidal signals are in fair agreement with predictions from motional induction. The lunar diurnal O1 signal, visible at some observatories, could be caused by ocean flow but disagrees in amplitude...

  17. Satellite measurements of formaldehyde linked to shipping emissions

    Directory of Open Access Journals (Sweden)

    T. Wagner

    2009-11-01

    Full Text Available International shipping is recognized as a pollution source of growing importance, in particular in the remote marine boundary layer. Nitrogen dioxide originating from ship emissions has previously been detected in satellite measurements. This study presents the first satellite measurements of formaldehyde (HCHO linked to shipping emissions as derived from observations made by the Global Ozone Monitoring Experiment (GOME instrument.

    We analyzed enhanced HCHO tropospheric columns from shipping emissions over the Indian Ocean between Sri Lanka and Sumatra. This region offers good conditions in term of plume detection with the GOME instrument as all ship tracks follow a single narrow track in the same east-west direction as used for the GOME pixel scanning. The HCHO signal alone is weak but could be clearly seen in the high-pass filtered data. The line of enhanced HCHO in the Indian Ocean as seen in the 7-year composite of cloud free GOME observations clearly coincides with the distinct ship track corridor from Sri Lanka to Indonesia. The observed mean HCHO column enhancement over this shipping route is about 2.0×1015 molec/cm2.

    Compared to the simultaneously observed NO2 values over the shipping route, those of HCHO are substantially higher; also the HCHO peaks are found at larger distance from the ship routes. These findings indicate that direct emissions of HCHO or degradation of emitted NMHC cannot explain the observed enhanced HCHO values. One possible reason might be increased CH4 degradation due to enhanced OH concentrations related to the ship emissions, but this source is probably too weak to fully explain the observed values.

    The observed HCHO pattern also agrees qualitatively well with results from the coupled earth system model ECHAM5/MESSy applied to atmospheric chemistry (EMAC. However, the modelled HCHO values over the ship corridor are two times lower than in the

  18. A Stochastic Approach to Noise Modeling for Barometric Altimeters

    Directory of Open Access Journals (Sweden)

    Angelo Maria Sabatini

    2013-11-01

    Full Text Available The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes, we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions.

  19. A stochastic approach to noise modeling for barometric altimeters.

    Science.gov (United States)

    Sabatini, Angelo Maria; Genovese, Vincenzo

    2013-11-18

    The question whether barometric altimeters can be applied to accurately track human motions is still debated, since their measurement performance are rather poor due to either coarse resolution or drifting behavior problems. As a step toward accurate short-time tracking of changes in height (up to few minutes), we develop a stochastic model that attempts to capture some statistical properties of the barometric altimeter noise. The barometric altimeter noise is decomposed in three components with different physical origin and properties: a deterministic time-varying mean, mainly correlated with global environment changes, and a first-order Gauss-Markov (GM) random process, mainly accounting for short-term, local environment changes, the effects of which are prominent, respectively, for long-time and short-time motion tracking; an uncorrelated random process, mainly due to wideband electronic noise, including quantization noise. Autoregressive-moving average (ARMA) system identification techniques are used to capture the correlation structure of the piecewise stationary GM component, and to estimate its standard deviation, together with the standard deviation of the uncorrelated component. M-point moving average filters used alone or in combination with whitening filters learnt from ARMA model parameters are further tested in few dynamic motion experiments and discussed for their capability of short-time tracking small-amplitude, low-frequency motions.

  20. Merging altimeter data with Argo profiles to improve observation of tropical Pacific thermocline circulation and ENSO

    Science.gov (United States)

    Zhang, D.; Lee, T.; Wang, F.; McPhaden, M. J.; Kessler, W. S.

    2016-12-01

    Meridional thermocline currents play an important role in the recharge and discharge of tropical Pacific warm water during the development and transition of ENSO cycles. Previous analyses have shown large variations of the equatorward meridional thermocline convergence/divergence on ENSO and decadal time scales in the interior ocean. The total convergence/divergence is however unknown due to the lack of long term observation in the western boundary currents. Numerical modelling studies suggested a tendency of compensation between the interior and western boundary currents, but the exact compensation is model dependent. While Argo floats provide reasonable data coverage in the interior ocean, few floats are in the western boundary currents. Recent multi-mission satellite altimeter data and advanced processing techniques have resulted in higher resolution sea surface height anomaly (SSHA) products with better accuracy closer to the coasts. This study utilizes the statistical relationship between Argo dynamic height profiles and altimeter SSHA to calculate geostrophic thermocline currents in both the interior ocean and the western boundary of the tropical Pacific. The derived thermocline currents in the western boundary are validated by a 3.5-year moored Acoustic Doppler Current Profiler (ADCP) measurement in the Mindanao Current and by a series of glider surveys (Davis et al. 2012) in the Solomon Sea. The meridional transport timeseries of the interior and western boundary currents in the thermocline show different lead-lag relationships to the Nino 3.4 index. Results will be discussed in the context of recent 2014-2015 El Nino development and the potential contribution to the Tropical Pacific Observing System (TPOS).

  1. Coherent Uncertainty Analysis of Aerosol Measurements from Multiple Satellite Sensors

    Science.gov (United States)

    Petrenko, M.; Ichoku, C.

    2013-01-01

    Aerosol retrievals from multiple spaceborne sensors, including MODIS (on Terra and Aqua), MISR, OMI, POLDER, CALIOP, and SeaWiFS altogether, a total of 11 different aerosol products were comparatively analyzed using data collocated with ground-based aerosol observations from the Aerosol Robotic Network (AERONET) stations within the Multi-sensor Aerosol Products Sampling System (MAPSS, http://giovanni.gsfc.nasa.gov/mapss/ and http://giovanni.gsfc.nasa.gov/aerostat/). The analysis was performed by comparing quality-screened satellite aerosol optical depth or thickness (AOD or AOT) retrievals during 2006-2010 to available collocated AERONET measurements globally, regionally, and seasonally, and deriving a number of statistical measures of accuracy. We used a robust statistical approach to detect and remove possible outliers in the collocated data that can bias the results of the analysis. Overall, the proportion of outliers in each of the quality-screened AOD products was within 12%. Squared correlation coefficient (R2) values of the satellite AOD retrievals relative to AERONET exceeded 0.6, with R2 for most of the products exceeding 0.7 over land and 0.8 over ocean. Root mean square error (RMSE) values for most of the AOD products were within 0.15 over land and 0.09 over ocean. We have been able to generate global maps showing regions where the different products present advantages over the others, as well as the relative performance of each product over different landcover types. It was observed that while MODIS, MISR, and SeaWiFS provide accurate retrievals over most of the landcover types, multi-angle capabilities make MISR the only sensor to retrieve reliable AOD over barren and snow / ice surfaces. Likewise, active sensing enables CALIOP to retrieve aerosol properties over bright-surface shrublands more accurately than the other sensors, while POLDER, which is the only one of the sensors capable of measuring polarized aerosols, outperforms other sensors in

  2. Coherent uncertainty analysis of aerosol measurements from multiple satellite sensors

    Directory of Open Access Journals (Sweden)

    M. Petrenko

    2013-02-01

    Full Text Available Aerosol retrievals from multiple spaceborne sensors, including MODIS (on Terra and Aqua, MISR, OMI, POLDER, CALIOP, and SeaWiFS – altogether, a total of 11 different aerosol products – were comparatively analyzed using data collocated with ground-based aerosol observations from the Aerosol Robotic Network (AERONET stations within the Multi-sensor Aerosol Products Sampling System (MAPSS, http://giovanni.gsfc.nasa.gov/mapss/ and http://giovanni.gsfc.nasa.gov/aerostat/. The analysis was performed by comparing quality-screened satellite aerosol optical depth or thickness (AOD or AOT retrievals during 2006–2010 to available collocated AERONET measurements globally, regionally, and seasonally, and deriving a number of statistical measures of accuracy. We used a robust statistical approach to detect and remove possible outliers in the collocated data that can bias the results of the analysis. Overall, the proportion of outliers in each of the quality-screened AOD products was within 12%. Squared correlation coefficient (R2 values of the satellite AOD retrievals relative to AERONET exceeded 0.6, with R2 for most of the products exceeding 0.7 over land and 0.8 over ocean. Root mean square error (RMSE values for most of the AOD products were within 0.15 over land and 0.09 over ocean. We have been able to generate global maps showing regions where the different products present advantages over the others, as well as the relative performance of each product over different landcover types. It was observed that while MODIS, MISR, and SeaWiFS provide accurate retrievals over most of the landcover types, multi-angle capabilities make MISR the only sensor to retrieve reliable AOD over barren and snow/ice surfaces. Likewise, active sensing enables CALIOP to retrieve aerosol properties

  3. Coherent uncertainty analysis of aerosol measurements from multiple satellite sensors

    Directory of Open Access Journals (Sweden)

    M. Petrenko

    2013-07-01

    Full Text Available Aerosol retrievals from multiple spaceborne sensors, including MODIS (on Terra and Aqua, MISR, OMI, POLDER, CALIOP, and SeaWiFS – altogether, a total of 11 different aerosol products – were comparatively analyzed using data collocated with ground-based aerosol observations from the Aerosol Robotic Network (AERONET stations within the Multi-sensor Aerosol Products Sampling System (MAPSS, http://giovanni.gsfc.nasa.gov/mapss/ and http://giovanni.gsfc.nasa.gov/aerostat/. The analysis was performed by comparing quality-screened satellite aerosol optical depth or thickness (AOD or AOT retrievals during 2006–2010 to available collocated AERONET measurements globally, regionally, and seasonally, and deriving a number of statistical measures of accuracy. We used a robust statistical approach to detect and remove possible outliers in the collocated data that can bias the results of the analysis. Overall, the proportion of outliers in each of the quality-screened AOD products was within 7%. Squared correlation coefficient (R2 values of the satellite AOD retrievals relative to AERONET exceeded 0.8 for many of the analyzed products, while root mean square error (RMSE values for most of the AOD products were within 0.15 over land and 0.07 over ocean. We have been able to generate global maps showing regions where the different products present advantages over the others, as well as the relative performance of each product over different land cover types. It was observed that while MODIS, MISR, and SeaWiFS provide accurate retrievals over most of the land cover types, multi-angle capabilities make MISR the only sensor to retrieve reliable AOD over barren and snow/ice surfaces. Likewise, active sensing enables CALIOP to retrieve aerosol properties over bright-surface closed shrublands more accurately than the other sensors, while POLDER, which is the only one of the sensors capable of measuring polarized aerosols, outperforms other sensors in certain

  4. IMPROVE THE ZY-3 HEIGHT ACCURACY USING ICESAT/GLAS LASER ALTIMETER DATA

    Directory of Open Access Journals (Sweden)

    G. Li

    2016-06-01

    Full Text Available ZY-3 is the first civilian high resolution stereo mapping satellite, which has been launched on 9th, Jan, 2012. The aim of ZY-3 satellite is to obtain high resolution stereo images and support the 1:50000 scale national surveying and mapping. Although ZY-3 has very high accuracy for direct geo-locations without GCPs (Ground Control Points, use of some GCPs is still indispensible for high precise stereo mapping. The GLAS (Geo-science Laser Altimetry System loaded on the ICESat (Ice Cloud and land Elevation Satellite, which is the first laser altimetry satellite for earth observation. GLAS has played an important role in the monitoring of polar ice sheets, the measuring of land topography and vegetation canopy heights after launched in 2003. Although GLAS has ended in 2009, the derived elevation dataset still can be used after selection by some criteria. In this paper, the ICESat/GLAS laser altimeter data is used as height reference data to improve the ZY-3 height accuracy. A selection method is proposed to obtain high precision GLAS elevation data. Two strategies to improve the ZY-3 height accuracy are introduced. One is the conventional bundle adjustment based on RFM and bias-compensated model, in which the GLAS footprint data is viewed as height control. The second is to correct the DSM (Digital Surface Model straightly by simple block adjustment, and the DSM is derived from the ZY-3 stereo imaging after freedom adjustment and dense image matching. The experimental result demonstrates that the height accuracy of ZY-3 without other GCPs can be improved to 3.0 meter after adding GLAS elevation data. What’s more, the comparison of the accuracy and efficiency between the two strategies is implemented for application.

  5. Improve the ZY-3 Height Accuracy Using Icesat/glas Laser Altimeter Data

    Science.gov (United States)

    Li, Guoyuan; Tang, Xinming; Gao, Xiaoming; Zhang, Chongyang; Li, Tao

    2016-06-01

    ZY-3 is the first civilian high resolution stereo mapping satellite, which has been launched on 9th, Jan, 2012. The aim of ZY-3 satellite is to obtain high resolution stereo images and support the 1:50000 scale national surveying and mapping. Although ZY-3 has very high accuracy for direct geo-locations without GCPs (Ground Control Points), use of some GCPs is still indispensible for high precise stereo mapping. The GLAS (Geo-science Laser Altimetry System) loaded on the ICESat (Ice Cloud and land Elevation Satellite), which is the first laser altimetry satellite for earth observation. GLAS has played an important role in the monitoring of polar ice sheets, the measuring of land topography and vegetation canopy heights after launched in 2003. Although GLAS has ended in 2009, the derived elevation dataset still can be used after selection by some criteria. In this paper, the ICESat/GLAS laser altimeter data is used as height reference data to improve the ZY-3 height accuracy. A selection method is proposed to obtain high precision GLAS elevation data. Two strategies to improve the ZY-3 height accuracy are introduced. One is the conventional bundle adjustment based on RFM and bias-compensated model, in which the GLAS footprint data is viewed as height control. The second is to correct the DSM (Digital Surface Model) straightly by simple block adjustment, and the DSM is derived from the ZY-3 stereo imaging after freedom adjustment and dense image matching. The experimental result demonstrates that the height accuracy of ZY-3 without other GCPs can be improved to 3.0 meter after adding GLAS elevation data. What's more, the comparison of the accuracy and efficiency between the two strategies is implemented for application.

  6. Benefits Derived From Laser Ranging Measurements for Orbit Determination of the GPS Satellite Orbit

    Science.gov (United States)

    Welch, Bryan W.

    2007-01-01

    While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current research is examining methods to lower the error in the GPS satellite ephemerides below their current level. Two GPS satellites that are currently in orbit carry retro-reflectors onboard. One notion to reduce the error in the satellite ephemerides is to utilize the retro-reflectors via laser ranging measurements taken from multiple Earth ground stations. Analysis has been performed to determine the level of reduction in the semi-major axis covariance of the GPS satellites, when laser ranging measurements are supplemented to the radiometric station keeping, which the satellites undergo. Six ground tracking systems are studied to estimate the performance of the satellite. The first system is the baseline current system approach which provides pseudo-range and integrated Doppler measurements from six ground stations. The remaining five ground tracking systems utilize all measurements from the current system and laser ranging measurements from the additional ground stations utilized within those systems. Station locations for the additional ground sites were taken from a listing of laser ranging ground stations from the International Laser Ranging Service. Results show reductions in state covariance estimates when utilizing laser ranging measurements to solve for the satellite s position component of the state vector. Results also show dependency on the number of ground stations providing laser ranging measurements, orientation of the satellite to the ground stations, and the initial covariance of the satellite's state vector.

  7. Estimates of forest height in the Amazon basin using radar altimeter data of SARIN mode onboard Cryosat-2

    Science.gov (United States)

    Yang, L.; Sun, G.; Liu, Q.

    2013-12-01

    Forest height is an important parameter for global carbon cycle studies. New technologies are required since the end of the operation ofGeoscience Laser Altimeter System (GLAS) onboard The Ice, Cloud, and land Elevation Satellite (IceSat) in 2009. CryoSat-2 is a European Space Agencyenvironmental research satellite which was launched in April 2010.The SIRAL (SAR Interferometer Radar Altimeter) on board CryoSat-2 provides three operational modes for different observational requirements. Before the launch of Icesat2 around July 2016, CryoSat data represents a unique source of information on regional-to-global scale forest canopy height.We propose to use radar altimetry waveforms from the synthetic aperture/interferometric (SARin) mode to estimate canopy height in the Amazon basin. To understand the relation between canopy structure and the SIRAL waveform in Ku band, a 3D model was developed and implemented based on a Lidar model by introducingthe scattering items from crown, trunk and ground surface at Ku band. The vertical distribution of tree crown volume within a SIRAL footprint was calculated from its 3-D stand model by summing the volumes of all tree crown cells at the same height from the ground. The preliminary comparisons between simulated and measured SIRAL waveforms show that the model captures the major characteristics of the SIRAL signature. Cryosat waveform data of SARin mode and from June, 2011 to June, 2012 (cycle 04) is used to retrieve canopy height at Amazon basin under Cryosat groundtrack. The canopy height is derived by extracting the key points of vegetation and ground returns after noise estimation. Because of lack of field tree height measurement in 2012 at Amazon, we validated the results using the field measurements at four areas (the km 67 camp, the km 77 camp, Ruropolis, the Taoajos river) of Tapajos National Forest, Brazil in November 1999, and compared the results with the canopy height estimation from previous studies using Laser

  8. Estimation of Satellite Orientation from Space Surveillance Imagery Measured with an Adaptive Optics Telescope

    Science.gov (United States)

    1996-12-01

    SATELLITE ORIENTATION FROM SPACE SURVEILLANCE IMAGERY MEASURED WITH AN ADAPTIVE OPTICS TELESCOPE THESIS Gregory E. Wood Lieutenant, USAF AFIT/GSO/ENP...the official policy or position of the Department of Defense or the U. S. Government. AFIT/GSO/ENP/96D-02 ESTIMATION OF SATELLITE ORIENTATION FROM...surveillance operations. xii ESTIMATION OF SATELLITE ORIENTATION FROM SPACE SURVEILLANCE IMAGERY MEASURED WITH AN ADAPTIVE OPTICS TELESCOPE

  9. Global Land Surface Emissivity Retrieved From Satellite Ultraspectral IR Measurements

    Science.gov (United States)

    Zhou, D. K.; Larar, A. M.; Liu, Xu; Smith, W. L.; Strow, L. L.; Yang, Ping; Schlussel, P.; Calbet, X.

    2011-01-01

    Ultraspectral resolution infrared (IR) radiances obtained from nadir observations provide information about the atmosphere, surface, aerosols, and clouds. Surface spectral emissivity (SSE) and surface skin temperature from current and future operational satellites can and will reveal critical information about the Earth s ecosystem and land-surface-type properties, which might be utilized as a means of long-term monitoring of the Earth s environment and global climate change. In this study, fast radiative transfer models applied to the atmosphere under all weather conditions are used for atmospheric profile and surface or cloud parameter retrieval from ultraspectral and/or hyperspectral spaceborne IR soundings. An inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral IR sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface or cloud microphysical parameters. This inversion scheme has been applied to the Infrared Atmospheric Sounding Interferometer (IASI). Rapidly produced SSE is initially evaluated through quality control checks on the retrievals of other impacted surface and atmospheric parameters. Initial validation of retrieved emissivity spectra is conducted with Namib and Kalahari desert laboratory measurements. Seasonal products of global land SSE and surface skin temperature retrieved with IASI are presented to demonstrate seasonal variation of SSE.

  10. Estimating the Retrievability of Temperature Profiles from Satellite Infrared Measurements

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A method is developed to assess retrievability, namely the retrieval potential for atmospheric temperature profiles, from satellite infrared measurements in clear-sky conditions. This technique is based upon generalized linear inverse theory and empirical orthogonal function analysis. Utilizing the NCEP global temperature reanalysis data in January and July from 1999 to 2003, the retrievabilities obtained with the Atmospheric Infrared Sounder (AIRS) and the High Resolution Infrared Radiation Sounder/3 (HIRS/3)sounding channel data are derived respectively for each standard pressure level on a global scale. As an incidental result of this study, the optimum truncation number in the method of generalized linear inverse is deduced too. The results show that the retrievabilities of temperature obtained with the two datasets are similar in spatial distribution and seasonal change characteristics. As for the vertical distribution, the retrievabilities are low in the upper and lower atmosphere, and high between 400 hPa and 850 hPa. For the geographical distribution, the retrievabilities are low in the low-latitude oceanic regions and in some regions in Antarctica, and relatively high in mid-high latitudes and continental regions. Compared with the HIRS/3 data, the retrievability obtained with the AIRS data can be improved by an amount between 0.15 and 0.40.

  11. Design of A Pentagon Microstrip Antenna for Radar Altimeter Application

    Directory of Open Access Journals (Sweden)

    K. RamaDevi

    2012-11-01

    Full Text Available In the navigational applications, radar and satellite requires a device that is a radar altimeter. Theworking frequency of this system is 4.2 to 4.3GHz and also requires less weight, low profile, and high gainantennas. The above mentioned application is possible with microstrip antenna as also known as planarantenna. In this paper, the microstrip antennas are designed at 4.3GHz (C-band in rectangular andcircular shape patch antennas in single element and arrays with parasitic elements placed in H-planecoupling. The performance of all these shapes is analyzed in terms of radiation pattern, half power points,and gain and impedance bandwidth in MATLAB. This work extended here with designed in different shapeslike Rhombic, Pentagon, Octagon and Edges-12 etc. Further these parameters are simulated in ANSOFTHFSSTMV9.0 simulator.

  12. Geoscience Laser Altimeter System: Characteristics and Performance of the Altimeter Receiver

    Science.gov (United States)

    Sun, Xiao-Li; Yi, Dong-Hui; Abshire, James B.

    2003-01-01

    The Geoscience Laser Altimeter System (GLAS) on board ICESat spacecraft measures the surface height (altimetry) via the time of flight of its 1064 nm laser pulse. The GLAS laser transmitter produces 6 ns wide pulses with 70 mJ energy at 1064 nm at a 40 Hz rate. The altimeter receiver consists of a telescope, aft optics, a silicon avalanche photodiode, and electronic amplifiers. The transmitted and echo pulse waveforms are digitized at 1 GHz rate. The laser pulse time of flight is determined on the ground from the two digitized pulse waveforms and their positions in the full waveform record (about 5.4 ms ong) by computing the pulse centroids or by curve fitting. The GLAS receiver algorithms in on board software selects the two waveform segments containing the transmitted and the echo pulses and sends them to ground. The probability of echo pulse detection and the accuracy of time of flight measurement depend on the received signal level, the background light within the receiver field of view, the inherent detector and amplifier noise, the quantization of the digitizer, and some times by cloud obscurations. A receiver model has been developed to calculate the probability of detection and accuracy of the altimeter measurements with these noise sources. From prelaunch testing, the minimum detectable echo pulse energy for 90% detection probability was about 0.1 fj/pulse onto the detector. Such a receiver sensitivity allows GLAS to measure the surface height through clouds with optical density less than 2. The echo pulse energy required to achieve 10 cm ranging accuracy was found to be about 3 times higher than the minimum detectable signal level. The smallest single shot range measurement error, which was determined by ranging to a fixed target with strong echo pulses and no background light, was 2 to 3cm. The maximum linear response echo pulse energy was 10 fJ/pulse for the strongest echo signals, assuming a Lambertian scattering snow surface, clear sky atmosphere

  13. Observing convection with satellite, radar, and lightning measurements

    Science.gov (United States)

    Hamann, Ulrich; Nisi, Luca; Clementi, Lorenzo; Ventura, Jordi Figueras i.; Gabella, Marco; Hering, Alessandro M.; Sideris, Ioannis; Trefalt, Simona; Germann, Urs

    2015-04-01

    Heavy precipitation, hail, and wind gusts are the fundamental meteorological hazards associated with strong convection and thunderstorms. The thread is particularly severe in mountainous areas, e.g. it is estimated that on average between 50% and 80% of all weather-related damage in Switzerland is caused by strong thunderstorms (Hilker et al., 2010). Intense atmospheric convection is governed by processes that range from the synoptic to the microphysical scale and are considered to be one of the most challenging and difficult weather phenomena to predict. Even though numerical weather prediction models have some skills to predict convection, in general the exact location of the convective initialization and its propagation cannot be forecasted by these models with sufficient precision. Hence, there is a strong interest to improve the short-term forecast by using statistical, object oriented and/or heuristic nowcasting methods. MeteoSwiss has developed several operational nowcasting systems for this purpose such as TRT (Hering, 2008) and COALITION (Nisi, 2014). In this contribution we analyze the typical development of convection using measurements of the Swiss C-band Dual Polarization Doppler weather radar network, the MSG SEVIRI satellite, and the Météorage lighting network. The observations are complemented with the analysis and forecasts of the COSMO model. Special attention is given to the typical evolutionary stages like the pre-convective environment, convective initiation, cloud top glaciation, start, maximum, and end of precipitation and lightning activity. The pre-convective environment is examined using instability indices derived from SEVIRI observations and the COSMO forecasts. During the early development satellite observations are used to observe the rise of the cloud top, the growth of the cloud droplet or crystals, and the glaciation of the cloud top. SEVIRI brightness temperatures, channel differences, and temporal trends as suggested by

  14. High Density GEOSAT/GM Altimeter Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The high density Geosat/GM altimeter data south of 30 S have finally arrived. In addition, ERS-1 has completed more than 6 cycles of its 35-day repeat track. These...

  15. Surface topography of the Greenland Ice Sheet from satellite radar altimetry

    Science.gov (United States)

    Bindschadler, Robert A.; Zwally, H. Jay; Major, Judith A.; Brenner, Anita C.

    1989-01-01

    Surface elevation maps of the southern half of the Greenland subcontinent are produced from radar altimeter data acquired by the Seasat satellite. A summary of the processing procedure and examples of return waveform data are given. The elevation data are used to generate a regular grid which is then computer contoured to provide an elevation contour map. Ancillary maps show the statistical quality of the elevation data and various characteristics of the surface. The elevation map is used to define ice flow directions and delineate the major drainage basins. Regular maps of the Jakobshavns Glacier drainage basin and the ice divide in the vicinity of Crete Station are presented. Altimeter derived elevations are compared with elevations measured both by satellite geoceivers and optical surveying.

  16. CONCEPTUAL PAPER : Utilization of GPS Satellites for Precise Irradiation Measurement and Monitoring

    Indian Academy of Sciences (India)

    S. Vijayan

    2008-03-01

    Precise measurement of irradiance over the earth under various circumstances like solar flares, coronal mass ejections, over an 11-year solar cycle, etc. leads to better understanding of Sun–earth relationship. To continuously monitor the irradiance over earth-space regions several satellites at several positions are required. For that continuous and multiple satellite monitoring we can use GPS (Global Positioning System) satellites (like GLONASS, GALILEO, future satellites) installed with irradiance measuring and monitoring instruments. GPS satellite system consists of 24 constellations of satellites. Therefore usage of all the satellites leads to 24 measurements of irradiance at the top of the atmosphere (or 12 measurements of those satellites which are pointing towards the Sun) at an instant. Therefore in one day, numerous irradiance observations can be obtained for the whole globe, which will be very helpful for several applications like Albedo calculation, Earth Radiation Budget calculation, monitoring of near earth-space atmosphere, etc. Moreover, measuring irradiance both in ground (using ground instruments) and in space at the same instant of time over a same place, leads to numerous advantages. That is, for a single position we obtain irradiance at the top of the atmosphere, irradiance at ground and the difference in irradiance from over top of the atmosphere to the ground. Measurement of irradiance over the atmosphere and in ground at a precise location gives more fine details about the solar irradiance influence over the earth, path loss and interaction of irradiance with the atmosphere.

  17. A fiducial reference site for satellite altimetry in Crete, Greece

    DEFF Research Database (Denmark)

    Mertikas, Stelios; Donlon, Craig; Mavrokordatos, Constantin;

    With the advent of diverse satellite altimeters and variant measuring techniques, it has become mature in the scientific community, that an absolute reference Cal/Val site is regularly maintained to define, monitor, control the responses of any altimetric system. This work sets the ground......, on a common and reliable reference and also to SI-traceable measurements. Results from this fiducial reference site will be based on historic Cal/Val site measurement records, and will be the yardstick for building up capacity for monitoring climate change. This will be achieved by defining and assessing any...

  18. GEOS-3 ocean current investigation using radar altimeter profiling. [Gulf Stream surface topography

    Science.gov (United States)

    Leitao, C. D.; Huang, N. E.; Parra, C. G.

    1978-01-01

    Both quasi-stationary and dynamic departures from the marine geoid were successfully detected using altitude measurements from the GEOS-3 radar altimeter. The quasi-stationary departures are observed either as elevation changes in single pass profiles across the Gulf Stream or at the crowding of contour lines at the western and northern areas of topographic maps generated using altimeter data spanning one month or longer. Dynamic features such as current meandering and spawned eddies can be monitored by comparing monthly mean maps. Comparison of altimeter inferred eddies with IR detected thermal rings indicates agreement of the two techniques. Estimates of current velocity are made using derived slope estimates in conjunction with the geostrophic equation.

  19. Measurements of Integration Gain for the Cospas-Sarsat System from Geosynchronous Satellites

    Science.gov (United States)

    Klein-Lebbink, Elizabeth; Christo, James; Peters, Robert; Nguyen, Xuan

    2015-01-01

    The GOES-R satellite is the first satellite to use a standard straight bent pipe transponder with no on-board re-modulation to support Search and Rescue (SAR) operations. Here, we report on the link measurements with a high fidelity satellite transponder simulator made up of satellite EDU (Engineering Design Units) components using an uplink from a beacon simulator and received by a GEOLUT (GEOsynchronous satellite Local User Terminal). We also report on the first ever measurements showing the performance gain obtained by the signal integration performed by the GEOLUT. In addition, a simulator made of commercially available off-the-shelf components assembled to develop the test plan was found to perform very close to the high fidelity simulator. In this paper, we describe what message integration is, how it is implemented in the particular satellite receiving station model used for this tests, and show the measured improvement in message decoding due to this integration process. These are the first tests to quantify the integration gain and are the first tests on the new SARSAT standard for the bent pipe (no onboard re-modulation) repeater used in GOES-R. An inexpensive satellite simulator to run test scripts built from off the shelf components was also found to have the same performance as a high fidelity simulator using actual satellite EDUs.

  20. Calculation of smoke plume mass from passive UV satellite measurements by GOME-2 polarization measurement devices

    Science.gov (United States)

    Penning de Vries, M. J. M.; Tuinder, O. N. E.; Wagner, T.; Fromm, M.

    2012-04-01

    The Wallow wildfire of 2011 was one of the most devastating fires ever in Arizona, burning over 2,000 km2 in the states of Arizona and New Mexico. The fire originated in the Bear Wallow Wilderness area in June, 2011, and raged for more than a month. The intense heat of the fire caused the formation of a pyro-convective cloud. The resulting smoke plume, partially located above low-lying clouds, was detected by several satellite instruments, including GOME-2 on June 2. The UV Aerosol Index, indicative of aerosol absorption, reached a maximum of 12 on that day, pointing to an elevated plume with moderately absorbing aerosols. We have performed extensive model calculations assuming different aerosol optical properties to determine the total aerosol optical depth of the plume. The plume altitude, needed to constrain the aerosol optical depth, was obtained from independent satellite measurements. The model results were compared with UV Aerosol Index and UV reflectances measured by the GOME-2 polarization measurement devices, which have a spatial resolution of roughly 10x40 km2. Although neither the exact aerosol optical properties nor optical depth can be obtained with this method, the range in aerosol optical depth values that we calculate, combined with the assumed specific extinction mass factor of 5 m2/kg lead us to a rough estimate of the smoke plume mass that cannot, at present, be assessed in another way.

  1. Spectral Measurements of Geosynchronous Satellites During Glint Season

    Science.gov (United States)

    2015-10-18

    primarily due to specular reflection off of the solar panels , the occurrence of a glint relative to solar phase angle or even the number of glints can...and south solar panels on DTV-12 being offset in different east-west angles causing two glints, whereas the two solar panels of Wildblue-1 are both in... solar panels that maintain a stable attitude relative to the earth and sun. During the equinox periods of the year, the geometry of the satellite

  2. The OSIRIS-REx Laser Altimeter (OLA) Investigation and Instrument

    Science.gov (United States)

    Daly, M. G.; Barnouin, O. S.; Dickinson, C.; Seabrook, J.; Johnson, C. L.; Cunningham, G.; Haltigin, T.; Gaudreau, D.; Brunet, C.; Aslam, I.; Taylor, A.; Bierhaus, E. B.; Boynton, W.; Nolan, M.; Lauretta, D. S.

    2017-08-01

    The Canadian Space Agency (CSA) has contributed to the Origins Spectral Interpretation Resource Identification Security-Regolith Explorer (OSIRIS-REx) spacecraft the OSIRIS-REx Laser Altimeter (OLA). The OSIRIS-REx mission will sample asteroid 101955 Bennu, the first B-type asteroid to be visited by a spacecraft. Bennu is thought to be primitive, carbonaceous, and spectrally most closely related to CI and/or CM meteorites. As a scanning laser altimeter, the OLA instrument will measure the range between the OSIRIS-REx spacecraft and the surface of Bennu to produce digital terrain maps of unprecedented spatial scales for a planetary mission. The digital terrain maps produced will measure ˜7 cm per pixel globally, and ˜3 cm per pixel at specific sample sites. In addition, OLA data will be used to constrain and refine the spacecraft trajectories. Global maps and highly accurate spacecraft trajectory estimates are critical to infer the internal structure of the asteroid. The global and regional maps also are key to gain new insights into the surface processes acting across Bennu, which inform the selection of the OSIRIS-REx sample site. These, in turn, are essential for understanding the provenance of the regolith sample collected by the OSIRIS-REx spacecraft. The OLA data also are important for quantifying any hazards near the selected OSIRIS-REx sample site and for evaluating the range of tilts at the sampling site for comparison against the capabilities of the sample acquisition device.

  3. Measurements of Cumulonimbus Clouds using quantitative satellite and radar data

    Science.gov (United States)

    Negri, A. J.; Reynolds, D. W.; Maddox, R. A.

    1977-01-01

    Results are reported for a preliminary study of SMS-2 digital brightness and IR data obtained at frequent 5-7.5 min intervals. The clouds studied were over the Central and Great Plains in midlatitudes and thus were typical of an environment much different from that of the tropical oceans. The satellite data are compared to radar data for both a severe weather event and weak thundershower activity of the type which might be a target for weather modification efforts. The relative importance of short time interval satellite data is shown for both cases, and possible relationships between the two types of data are presented. It is concluded that (1) using a threshold technique for visible reflected brightness, precipitating vs. nonprecipitating clouds can be discriminated; (2) brightness is well related to cloud size and shape; and (3) satellite-derived growth rates may be a significant parameter to be used in determining storm severity, especially if rapid time sequence data are used during the development phase of the storm.

  4. The Geodesy of the Main Saturnian Satellites from Range Rate Measurements of the Cassini Spacecraft

    Science.gov (United States)

    Ducci, M.; Iess, L.; Armstrong, J. W.; Asmar, S. W.; Jacobson, R. A.; Lunine, J. I.; Racioppa, P.; Rappaport, N. J.; Stevenson, D. J.; Tortora, P.

    2012-03-01

    During Cassini's eight-year tour in the saturnian system, the gravity field of the main satellites was inferred from range rate measurements of the spacecraft. Here we present our latest results and an overview of our analysis methods.

  5. Satellite (Timed, Aura, Aqua) and In Situ (Meteorological Rockets, Balloons) Measurement Comparability

    Science.gov (United States)

    Schmidlin, F. J.; Goldberg, Richard A.; Feofilov, A.; Rose, R.

    2010-01-01

    Measurements using the inflatable falling sphere often are requested to provide density data in support of special sounding rocket launchings into the mesosphere and thermosphere. To insure density measurements within narrow time frames and close in space, the inflatable falling sphere is launched within minutes of the major test. Sphere measurements are reliable for the most part, however, availability of these rocket systems has become more difficult and, in fact, these instruments no longer are manufactured resulting in a reduction of the meager stockpile of instruments. Sphere measurements also are used to validate remotely measured temperatures and have the advantage of measuring small-scale atmospheric features. Even so, with the dearth of remaining falling spheres perhaps it is time to consider whether the remote measurements are mature enough to stand alone. Presented are two field studies, one in 2003 from Northern Sweden and one in 2010 from the vicinity of Kwajalein Atoll that compare temperature retrievals between satellite and in situ failing spheres. The major satellite instruments employed are SABER, MLS, and AIRS. The comparisons indicate that remotely measured temperatures mimic the sphere temperature measurements quite well. The data also confirm that satellite retrievals, while not always at the exact location required for individual studies, are adaptable enough and highly useful. Although the falling sphere will provide a measurement at a specific location and time, satellites only pass a given location daily or less often. This report reveals that averaged satellite measurements can provide temperatures and densities comparable to the falling sphere.

  6. Calculation of the satellite "Sich-1M" orientation on onboard magnetometric measurements

    Science.gov (United States)

    Suhorukov, A.; Kozak, L.

    2005-04-01

    The satellite "Sich-1M" was launched on 24 December 2004. It came out onto the elliptic orbit with the perigee height near 280 km except planned earlier higher near circle orbit. In addition, the satellite has gotten a non-planned rotation (about 2 rotations per turn). Later the gravitational beam had been pulled out from the satellite which partly stabilized it. A rotation of the satellite was superseded by its oscillation with a period near 2-4 swings per turn and amplitude 50 degrees. The oscillations have an unstable character. Rotations and oscillations of the satellite set inessential limitations on realization of scientific tasks of the project "Variant" because there is a possibility to determine the satellite orientation for a given time moment with the help of measurements of ferrosonde magnetometer FZM or onboard magnetometer. The device FZM measures three components of magnetic field Bx, By, Bz of the Earth in coordinate system of the satellite. To determine the satellite orientation we have used the fact that each of the component of the magnetic field at the present time moment is a function of geographical coordinates of the satellite (latitude, longitude, height over sea level), its orientation and components of a vector of Earth magnetic field in this point, calculated from magnetosphere model. Thus, having direct satellite measurements of Bx, By, Bz at given time moment in given point, orbital elements and position of the satellite on the orbit and using the standard model of Earth's magnetosphere one can calculate the satellite orientation as function of time. For the calculation we have used the magnetosphere model "The International Geomagnetic Reference Field" (IGRF) which empirically calculates the components of magnetic field of the Earth and is recommended for scientific investigations by International Association of Geomagnetism and Aeronomy (IAGA). Coefficients of IGRF model are based on accessible information sources including

  7. Satellite and terrestrial narrow-band propagation measurements at 2.05 GHz

    Science.gov (United States)

    Vaisnys, Arv; Vogel, Wolf

    1995-08-01

    A series of satellite and terrestrial propagation measurements were conducted on 15 and 16 Dec. 1994 in the vicinity of the Jet Propulsion Laboratory (JPL), Pasadena, California, in support of the VOA/JPL DBS-Radio Program. The reason for including terrestrial measurements was the possible use of terrestrial boosters to improve reception in some satellite digital audio broadcasting system service areas. The signal sources used were the NASA TDRS satellite located at 171 degrees West and a terrestrial transmitter located on a high point on JPL property. Both signals were unmodulated carriers near 2.05 GHz, spaced a few kHz apart so that both could be received simultaneously by a single receiver. An unmodulated signal was used in order to maximize the dynamic range of the signal strength measurement. A range of greater than 35 dB was achieved with the satellite signal, and over 50 dB was achieved with the terrestrial signal measurements. Three test courses were used to conduct the measurements: (1) a 33 km round trip drive from JPL through Pasadena was used to remeasure the propagation of the satellite signal over the path previously used in DBS-Radio experiments in mid 1994. A shortened portion of this test course, approximately 20 km, was used to measure the satellite and terrestrial signals simultaneously; (2) a 9 km round trip drive through JPL property, going behind buildings and other obstacles, was used to measure the satellite and terrestrial signals simultaneously; and (3) a path through one of the buildings at JPL, hand carrying the receiver, was also used to measure the satellite and terrestrial signals simultaneously.

  8. Sub-visual cirrus LIDAR measurements for satellite masking improvement

    Science.gov (United States)

    Landulfo, Eduardo; Larroza, Eliane G.; Lopes, Fábio J. S.; de Jesus, Wellington C.; Bottino, Marcus; Nakaema, Walter M.; Steffens, Juliana

    2008-10-01

    Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial emitted radiations is crucial for climate studies. Unlike most boundary layer stratus and stratocumulus clouds that have a net cooling effect on the climate, high-level thin cirrus clouds have a warming effect on our climate. However, the satellites as GOES from the NOAA series are limited to the cloud top and its reflectivity or brightness temperature, without assessing accurately the optical depth or physical thickness. Other more recent sensors as MODIS are able to determine optical depths for aerosols and clouds but when related to cirrus they are still inaccurate. Research programs as First ISCCP, FIRE, HOIST, ECLIPS and ARM have concentrated efforts in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and airplanes instruments. LIDARs are able to detect sub-visual cirrus cloud (SVCs) in altitudes above 15 km and estimate exactly their height, thickness and optical depth, contributing with information for satellites sensors and radiative transfer models. In order to research characteristics of SVCs, the LIDAR system at Instituto de Pesquisas Energeticas e Nucleares has as objective to determine such parameters and implement a cirrus cloud mask that could be used in the satellite images processing as well as in the qualitative improvement of the radiative parameters for numerical models of climate changes. The first preliminary study shows where we compare the data lidar with Brightness temperature differences between the split-window data from GOES-10 (DSA/INPE) and CALIPSO.

  9. Ocean state indicators from MyOcean altimeter products

    Directory of Open Access Journals (Sweden)

    L. Bessières

    2013-06-01

    Full Text Available The European MyOcean project (http://www.myocean.eu.org provides observations of the ocean dynamic topography from altimeter measurements. Three specific indicators have been developed, based on altimeter data only, in order to monitor the ocean state. The first ocean indicator observes the positive and negative phases of the ENSO events in the tropical Pacific, the El Niño/La Niña events, since 1992. The second ocean indicator tracks the contracted or extended state of the Kuroshio Extension. The last ocean indicator is dedicated to the Ionian Basin in the Mediterranean Sea and permits separation of "zonal-cyclonic" state (1998–2005 and since 2011 up to now from the "anticyclonic" state (1993–1996 usually discussed in the literature. In addition, it allows identifying a third state in which both the anticyclonic circulation around the northern part of the basin and the strong zonal Mid-Ionian Jet co-exist (2008–2010.

  10. Laser Altimeter for Flight Simulator

    Science.gov (United States)

    Webster, L. D.

    1986-01-01

    Height of flight-simulator probe above model of terrain measured by automatic laser triangulation system. Airplane simulated by probe that moves over model of terrain. Altitude of airplane scaled from height of probe above model. Height measured by triangulation of laser beam aimed at intersection of model surface with plumb line of probe.

  11. Spin period and attitude of satellites and space debris measured by using photometry

    Science.gov (United States)

    Shakun, Leonid; Koshkin, Nikolay; Korobeynikova, Elena; Strakhova, Svetlana; Melikyants, Seda; Ryabov, Andrey

    2016-07-01

    Photometry is an essential method for studying of the properties of the proper rotation of satellites and space debris. The observation method with high time resolution is used in the Odessa astronomical observatory for observations of artificial satellites. This method provides the measuring of the orbital motion and the proper rotation of satellites. Worth note, that the time resolution of the light curve and the accuracy of positioning in time of the details in the light curve are more important for the interpretation of the brightness variations than the precise measuring of the brightness. The rapid photometry allows not only registering of the flashes caused by mirror surfaces of structure satellite elements but also determining the indicatrix of the corresponding structure satellite element. This principal change of the photometric quality allows significant improving the interpretation of the satellites' light curves. We obtained a large amount of the photometric observations sequences of the satellites with time resolution 0.02 sec on the 50 cm telescope during last 11 years. We used this data for determination of the rotational parameters of several space objects. We present the method and results of the data analysis for the inactive satellites such as Envisat, Cbers-2B, Topex and other. Each of them changes its rotational parameters in its own way. For some satellites, the rotation period increases, for other it decreases. The rotation axis also change their orientation in space. The obtained information about rotation characteristics can be used for the precise numerical models of the satellite orbital motion and for the future Active Debris Removal missions.

  12. MEaSUREs Land Surface Temperature from GOES Satellites

    Science.gov (United States)

    Pinker, Rachel T.; Chen, Wen; Ma, Yingtao; Islam, Tanvir; Borbas, Eva; Hain, Chris; Hulley, Glynn; Hook, Simon

    2017-04-01

    Information on Land Surface Temperature (LST) can be generated from observations made from satellites in low Earth orbit (LEO) such as MODIS and ASTER and by sensors in geostationary Earth orbit (GEO) such as GOES. Under a project titled: "A Unified and Coherent Land Surface Temperature and Emissivity Earth System Data Record for Earth Science" led by Jet Propulsion Laboratory, an effort is underway to develop long term consistent information from both such systems. In this presentation we will describe an effort to derive LST information from GOES satellites. Results will be presented from two approaches: 1) based on regression developed from a wide range of simulations using MODTRAN, SeeBor Version 5.0 global atmospheric profiles and the CAMEL (Combined ASTER and MODIS Emissivity for Land) product based on the standard University of Wisconsin 5 km emissivity values (UWIREMIS) and the ASTER Global Emissivity Database (GED) product; 2) RTTOV radiative transfer model driven with MERRA-2 reanalysis fields. We will present results of evaluation of these two methods against various products, such as MOD11, and ground observations for the five year period of (2004-2008).

  13. A pathway to generating Climate Data Records of sea-surface temperature from satellite measurements

    Science.gov (United States)

    Minnett, Peter J.; Corlett, Gary K.

    2012-11-01

    In addition to having known uncertainty characteristics, Climate Data Records (CDRs) of geophysical variables derived from satellite measurements must be of sufficient length to resolve signals that might reveal the signatures of climate change against a background of larger, unrelated variability. The length of the record requires using satellite measurements from many instruments over several decades, and the uncertainty requirement implies that a consistent approach be used to establish the errors in the satellite retrievals over the entire period. Retrieving sea-surface temperature (SST) from satellite is a relatively mature topic, and the uncertainties of satellite retrievals are determined by comparison with collocated independent measurements. To avoid the complicating effects of near-surface temperature gradients in the upper ocean, the best validating measurements are from ship-board radiometers that measure, at source, the surface emission that is measured in space, after modification by its propagation through the atmosphere. To attain sufficient accuracy, such ship-based radiometers must use internal blackbody calibration targets, but to determine the uncertainties in these radiometric measurements, i.e. to confirm that the internal calibration is effective, it is necessary to conduct verification of the field calibration using independent blackbodies with accurately known emissivity and at very accurately measured temperatures. This is a well-justifiable approach to providing the necessary underpinning of a Climate Data Record of SST.

  14. Experimental study of mountain lee—waves by means of satellite photographs and aircraft measurements

    OpenAIRE

    Cruette, Denise

    2011-01-01

    This paper is a summary of a Ph.D. Thesis1 which was a systematic study of the influence of various meteorological factors on the occurrence and characteristics of mountain waves, more specifically of lee-waves of great horizontal extent. The data used are, beside classical meteorological informations, that given by satellite pictures completed by quasi-simultaneous measurements from planes or gliders. The analysis of many satellite pictures received at the french station of Lannion (Brittany...

  15. Comparing clouds and their seasonal variations in 10 atmospheric general circulation models with satellite measurements

    OpenAIRE

    Zhang, M.; Lin, W.; Klein, S.; J. Bacmeister; Bony, S.; Cederwall, R.; Del Genio, A; Hack, J.; Loeb, N.; Lohmann, U.; P. Minnis; Musat, I.; Pincus, R; Stier, P.; Suarez, M.

    2005-01-01

    To assess the current status of climate models in simulating clouds, basic cloud climatologies from ten atmospheric general circulation models are compared with satellite measurements from the International Satellite Cloud Climatology Project (ISCCP) and the Clouds and Earth's Radiant Energy System (CERES) program. An ISCCP simulator is employed in all models to facilitate the comparison. Models simulated a four-fold difference in high-top clouds. There are also, however, large uncertainties ...

  16. CONTRIBUTION OF SATELLITE ALTIMETRY DATA IN GEOLOGICAL STRUCTURE RESEARCH IN THE SOUTH CHINA SEA

    Directory of Open Access Journals (Sweden)

    T. D. Tran

    2016-06-01

    Full Text Available The study area is bordered on the East China Sea, the Philippine Sea, and the Australian-Indo plate in the Northeast, in the East and in the South, respectively. It is a large area with the diversely complicated conditions of geological structure. In spite of over the past many years of investigation, marine geological structure in many places have remained poorly understood because of a thick seawater layer as well as of the sensitive conflicts among the countries in the region. In recent years, the satellite altimeter technology allows of enhancement the marine investigation in any area. The ocean surface height is measured by a very accurate radar altimeter mounted on a satellite. Then, that surface can be converted into marine gravity anomaly or bathymetry by using the mathematical model. It is the only way to achieve the data with a uniform resolution in acceptable time and cost. The satellite altimetry data and its variants are essential for understanding marine geological structure. They provide a reliable opportunity to geologists and geophysicists for studying the geological features beneath the ocean floor. Also satellite altimeter data is perfect for planning the more detailed shipboard surveys. Especially, it is more meaningful in the remote or sparsely surveyed regions. In this paper, the authors have effectively used the satellite altimetry and shipboard data in combination. Many geological features, such as seafloor spreading ridges, fault systems, volcanic chains as well as distribution of sedimentary basins are revealed through the 2D, 3D model methods of interpretation of satellite-shipboard-derived data and the others. These results are improved by existing boreholes and seismic data in the study area.

  17. Contribution of Satellite Altimetry Data in Geological Structure Research in the South China Sea

    Science.gov (United States)

    Dung Tran, Tuan; Ho, Thi Huong Mai

    2016-06-01

    The study area is bordered on the East China Sea, the Philippine Sea, and the Australian-Indo plate in the Northeast, in the East and in the South, respectively. It is a large area with the diversely complicated conditions of geological structure. In spite of over the past many years of investigation, marine geological structure in many places have remained poorly understood because of a thick seawater layer as well as of the sensitive conflicts among the countries in the region. In recent years, the satellite altimeter technology allows of enhancement the marine investigation in any area. The ocean surface height is measured by a very accurate radar altimeter mounted on a satellite. Then, that surface can be converted into marine gravity anomaly or bathymetry by using the mathematical model. It is the only way to achieve the data with a uniform resolution in acceptable time and cost. The satellite altimetry data and its variants are essential for understanding marine geological structure. They provide a reliable opportunity to geologists and geophysicists for studying the geological features beneath the ocean floor. Also satellite altimeter data is perfect for planning the more detailed shipboard surveys. Especially, it is more meaningful in the remote or sparsely surveyed regions. In this paper, the authors have effectively used the satellite altimetry and shipboard data in combination. Many geological features, such as seafloor spreading ridges, fault systems, volcanic chains as well as distribution of sedimentary basins are revealed through the 2D, 3D model methods of interpretation of satellite-shipboard-derived data and the others. These results are improved by existing boreholes and seismic data in the study area.

  18. Relative navigation for satellite formation flight using a continuous-discrete converted measurement Kalman filter

    Institute of Scientific and Technical Information of China (English)

    XUE Dan; CAO Xi-bin

    2008-01-01

    The present paper develops an approach of relative orbit determination for satellite formation flight. Inter-satellite measurements by the onboard devices of the satellite were chosen to perform this relative naviga-tion, and the equations of relative motion expressed in the Earth Centered Inertial frame were used to eliminate the assumption of the circular reference orbit. The relative orbit estimation was achieved through a continuous-discrete converted measurement Kalman filter design, in which the measurements were transformed to the iner-tial frame to avoid the linearization error of the observation equation. In addition, the situation of the coarse measurement period (only microwave radar measurements are available) existing was analyzed. The numerical simulation results verify the validity of the navigation approach, and it has been proved that this approach can be applied to the formation with an elliptical reference orbit.

  19. Understanding data noise in gravity field recovery on the basis of inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE

    NARCIS (Netherlands)

    Ditmar, P.; Teixeira da Encarnacao, J.; Hashemi Farahani, H.

    2012-01-01

    Spectral analysis of data noise is performed in the context of gravity field recovery from inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE. The motivation of the study is two-fold: (i) to promote a further improvement of GRACE data processing techniques and

  20. Recovery Of Short Wavelength Geophysical Signals With Future Delay-Doppler Altimeters (Cryosat Ii And Sentinel Type)

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar

    2010-01-01

    A number of geophysical phenomena in the open ocean are still unresolved by conventional 1 Hz altimetry, but could be observed through the potential improvements offered by SAR, or Delay-Doppler (DD), altimetry. The DD altimeter offers the following benefits with respect to conventional satellite...... wavelength geophysical signal related to mainly bathymetric features. The combination of upward continuation from the sea bottom and smoothing the altimeter observations resulted in the best recovery of geophysical signal for simulated 5-Hz DD observations. Simulations carried out in this investigation...... indicate, that if the Cryosat-II mission meets the mission goals, the possibility of recovering a huge number of geophysical signal not currently mapped and the possibility to recover global gravity to an accuracy of up to twice that known today from conventional satellite altimetry....

  1. Test Port for Fiber-Optic-Coupled Laser Altimeter

    Science.gov (United States)

    Ramos Izquierdo, Luis; Scott, V. Stanley; Rinis, Haris; Cavanaugh, John

    2011-01-01

    A test port designed as part of a fiber optic coupled laser altimeter receiver optical system allows for the back-illumination of the optical system for alignment verification, as well as illumination of the detector(s) for testing the receiver electronics and signal-processing algorithms. Measuring the optical alignment of a laser altimeter instrument is difficult after the instrument is fully assembled. The addition of a test port in the receiver aft-optics allows for the back-illumination of the receiver system such that its focal setting and boresight alignment can be easily verified. For a multiple-detector receiver system, the addition of the aft-optics test port offers the added advantage of being able to simultaneously test all the detectors with different signals that simulate the expected operational conditions. On a laser altimeter instrument (see figure), the aft-optics couple the light from the receiver telescope to the receiver detector(s). Incorporating a beam splitter in the aft-optics design allows for the addition of a test port to back-illuminate the receiver telescope and/or detectors. The aft-optics layout resembles a T with the detector on one leg, the receiver telescope input port on the second leg, and the test port on the third leg. The use of a custom beam splitter with 99-percent reflection, 1-percent transmission, and a mirrored roof can send the test port light to the receiver telescope leg as well as the detector leg, without unduly sacrificing the signal from the receiver telescope to the detector. The ability to test the receiver system alignment, as well as multiple detectors with different signals without the need to disassemble the instrument or connect and reconnect components, is a great advantage to the aft-optics test port. Another benefit is that the receiver telescope aperture is fully back-illuminated by the test port so the receiver telescope focal setting vs. pressure and or temperature can be accurately measured (as

  2. In-Flight Thermal Performance of the Geoscience Laser Altimeter System (GLAS) Instrument

    Science.gov (United States)

    Grob, Eric; Baker, Charles; McCarthy, Tom

    2003-01-01

    The Geoscience Laser Altimeter System (GLAS) instrument is NASA Goddard Space Flight Center's first application of Loop Heat Pipe technology that provides selectable/stable temperature levels for the lasers and other electronics over a widely varying mission environment. GLAS was successfully launched as the sole science instrument aboard the Ice, Clouds, and Land Elevation Satellite (ICESat) from Vandenberg AFB at 4:45pm PST on January 12, 2003. After SC commissioning, the LHPs started easily and have provided selectable and stable temperatures for the lasers and other electronics. This paper discusses the thermal development background and testing, along with details of early flight thermal performance data.

  3. Measurements of ionospheric TEC in the direction of GPS satellites and comparison with three ionospheric models

    Directory of Open Access Journals (Sweden)

    E. Zuccheretti

    1997-06-01

    Full Text Available The IEN Galileo Ferraris uses GPS for time and frequency synchronization. To obtain high performance it is important to reduce the error due to the ionospheric time-delay in GPS measurements. Evaluations of TEC in the direction of GPS satellites, obtained from three different ionospheric models, have been compared with corresponding measurements by GPS signal.

  4. Radiation budget and related measurements in 1985 and beyond. [earth radiation budget satellite system

    Science.gov (United States)

    1978-01-01

    Development of systems for obtaining radiation budget and cloud data is discussed. Instruments for measuring total solar irradiance, total infrared flux, reflected solar flux, and cloud heights and properties are considered. Other topics discussed include sampling by multiple satellites, user identification, and determination of the parameters that need to be measured.

  5. Stochastic estimation of dynamically changing object orientation parameters using satellite measurements

    OpenAIRE

    Lukasevich, V. I.; Kramarov, S. O.; Sokolov, Sergey V.

    2015-01-01

    It is solved a problem of a posteriori estimation of dynamically modified parameters of angular movement of the object by satellite measurements. There are shown advantages of application of the methods of stochastic non-linear dynamic filtration before single-stage measurements. It is represented an example, showing efficiency of proposed approach.

  6. Analysis and interpretation of Cassini Titan radar altimeter echoes

    Science.gov (United States)

    Zebker, Howard A.; Gim, Yonggyu; Callahan, Philip; Hensley, Scott; Lorenz, Ralph; Cassini Radar Team

    2009-03-01

    The Cassini spacecraft has acquired 25 radar altimeter elevation profiles along Titan's surface as of April 2008, and we have analyzed 18 of these for which there are currently reconstructed ephemeris data. Altimeter measurements were collected at spatial footprint sizes from 6-60 km along ground tracks of length 400-3600 km. The elevation profiles yield topographic information at this resolution with a statistical height accuracy of 35-50 m and kilometer-scale errors several times greater. The data exhibit significant variations in terrain, from flat regions with little topographic expression to very rugged Titanscapes. The bandwidth of the transmitted waveform admits vertical resolution of the terrain height to 35 m at each observed location on the surface. Variations in antenna pointing and changes in surface statistics cause the range-compressed radar echoes to exhibit strong systematic and time-variable biases of hundreds of meters in delay. It is necessary to correct the received echoes for these changes, and we have derived correction algorithms such that the derived echo profiles are accurate at the 100 m level for off-nadir pointing errors of 0.3° and 0.6°, for leading edge and echo centroid estimators, respectively. The leading edge of the echo yields the elevation of the highest points on the surface, which we take to be the peaks of any terrain variation. The mean value of the echo delay is more representative of the mean elevation, so that the difference of these values gives an estimate of any local mountain heights. Finding locations where these values diverge indicates higher-relief terrain. Elevation features are readily seen in the height profiles. Several of the passes show mountains of several hundred m altitude, spread over 10's or even 100's of km in spatial extent, so that slopes are very small. Large expanses of sub-100 m topography are commonplace on Titan, so it is rather smooth in many locations. Other areas exhibit more relief

  7. Monitoring Sea Level in the Coastal Zone with Satellite Altimetry and Tide Gauges

    Science.gov (United States)

    Cipollini, Paolo; Calafat, Francisco M.; Jevrejeva, Svetlana; Melet, Angelique; Prandi, Pierre

    2016-11-01

    We examine the issue of sustained measurements of sea level in the coastal zone, first by summarizing the long-term observations from tide gauges, then showing how those are now complemented by improved satellite altimetry products in the coastal ocean. We present some of the progresses in coastal altimetry, both from dedicated reprocessing of the radar waveforms and from the development of improved corrections for the atmospheric effects. This trend towards better altimetric data at the coast comes also from technological innovations such as Ka-band altimetry and SAR altimetry, and we discuss the advantages deriving from the AltiKa Ka-band altimeter and the SIRAL altimeter on CryoSat-2 that can be operated in SAR mode. A case study along the UK coast demonstrates the good agreement between coastal altimetry and tide gauge observations, with root mean square differences as low as 4 cm at many stations, allowing the characterization of the annual cycle of sea level along the UK coasts. Finally, we examine the evolution of the sea level trend from the open to the coastal ocean along the western coast of Africa, comparing standard and coastally improved products. Different products give different sea level trend profiles, so the recommendation is that additional efforts are needed to study sea level trends in the coastal zone from past and present satellite altimeters. Further improvements are expected from more refined processing and screening of data, but in particular from the constant improvements in the geophysical corrections.

  8. Monitoring Sea Level in the Coastal Zone with Satellite Altimetry and Tide Gauges

    Science.gov (United States)

    Cipollini, Paolo; Calafat, Francisco M.; Jevrejeva, Svetlana; Melet, Angelique; Prandi, Pierre

    2017-01-01

    We examine the issue of sustained measurements of sea level in the coastal zone, first by summarizing the long-term observations from tide gauges, then showing how those are now complemented by improved satellite altimetry products in the coastal ocean. We present some of the progresses in coastal altimetry, both from dedicated reprocessing of the radar waveforms and from the development of improved corrections for the atmospheric effects. This trend towards better altimetric data at the coast comes also from technological innovations such as Ka-band altimetry and SAR altimetry, and we discuss the advantages deriving from the AltiKa Ka-band altimeter and the SIRAL altimeter on CryoSat-2 that can be operated in SAR mode. A case study along the UK coast demonstrates the good agreement between coastal altimetry and tide gauge observations, with root mean square differences as low as 4 cm at many stations, allowing the characterization of the annual cycle of sea level along the UK coasts. Finally, we examine the evolution of the sea level trend from the open to the coastal ocean along the western coast of Africa, comparing standard and coastally improved products. Different products give different sea level trend profiles, so the recommendation is that additional efforts are needed to study sea level trends in the coastal zone from past and present satellite altimeters. Further improvements are expected from more refined processing and screening of data, but in particular from the constant improvements in the geophysical corrections.

  9. Application of satellite infrared measurements to mapping sea ice

    Science.gov (United States)

    Barnes, J. C.

    1972-01-01

    The application of the ITOS-SR (scanning radiometer) infrared measurements for mapping sea ice was examined. The work included detailed mapping of ice features visible in the ITOS nighttime DRSR (direct readout scanning radiometer) pictorial data and in Nimbus summertime film strip data. Analyses of digital temperature values from computer printouts of ITOS stored data and from Nimbus data listings were also undertaken, and densitometric measurements of both ITOS and Nimbus data were initiated.

  10. Improvement of NCEP Numerical Weather Prediction with Use of Satellite Land Measurements

    Science.gov (United States)

    Zheng, W.; Ek, M. B.; Wei, H.; Meng, J.; Dong, J.; Wu, Y.; Zhan, X.; Liu, J.; Jiang, Z.; Vargas, M.

    2014-12-01

    Over the past two decades, satellite measurements are being increasingly used in weather and climate prediction systems and have made a considerable progress in accurate numerical weather and climate predictions. However, it is noticed that the utilization of satellite measurements over land is far less than over ocean, because of the high land surface inhomogeneity and the high emissivity variabilities in time and space of surface characteristics. In this presentation, we will discuss the application efforts of satellite land observations in the National Centers for Environmental Prediction (NCEP) operational Global Forecast System (GFS) in order to improve the global numerical weather prediction (NWP). Our study focuses on use of satellite data sets such as vegetation type and green vegetation fraction, assimilation of satellite products such as soil moisture retrieval, and direct radiance assimilation. Global soil moisture data products could be used for initialization of soil moisture state variables in numerical weather, climate and hydrological forecast models. A global Soil Moisture Operational Product System (SMOPS) has been developed at NOAA-NESDIS to continuously provide global soil moisture data products to meet NOAA-NCEP's soil moisture data needs. The impact of the soil moisture data products on numerical weather forecast is assessed using the NCEP GFS in which the Ensemble Kalman Filter (EnKF) data assimilation algorithm has been implemented. In terms of radiance assimilation, satellite radiance measurements in various spectral channels are assimilated through the JCSDA Community Radiative Transfer Model (CRTM) on the NCEP Gridpoint Statistical Interpolation (GSI) system, which requires the CRTM to calculate model brightness temperature (Tb) with input of model atmosphere profiles and surface parameters. Particularly, for surface sensitive channels (window channels), Tb largely depends on surface parameters such as land surface skin temperature, soil

  11. Validation of satellite data with IASOA observatories and shipboard measurements in Arctic Ocean

    Science.gov (United States)

    Repina, Irina; Artamonov, Arseniy; Mazilkina, Alexandra; Valiullin, Denis; Stanichny, Sergey

    2016-04-01

    The paper shows the possibility of using surface observation data at high latitudes for the validation of different satellite products. We use data from International Arctic Systems for Observing the Atmosphere (IASOA) observatories and data from Nansen and Amundsen basins observation system (NABOS) project. The NABOS field experiment was carried out in the central part of the Arctic and in the eastern Arctic seas during summer and fall period of 2004-2009, 2013 and 2015. Newly improved satellite products and surface observations provide an opportunity to revisit remote-sensing capabilities for estimating shortwave and longwave radiative fluxes, as well as turbulent fluxes at high latitudes. Estimates of SW fluxes from the MODIS and LW fluxes from the NOAA satellites are evaluated against land observations from IASOA observatories, and unique shipboard measurements. Results show that the satellite products are in better agreement with observations than those from numerical models. Therefore, the large scale satellite based estimates should be useful for model evaluation and for providing information in formulating energy budgets at high latitudes. Visible and near-infrared albedos over snow and ice surfaces are retrieved from AVHRR. Comparison with surface measurements of albedo in arctic observatories and Arctic ocean shows very good agreement. Meteorological and micrometeorological observations were used to validate the surface temperature and surface heat fluxes in the satellite data. Compared data arrays are independent and sufficiently detailed to perform trustworthy evaluations. The spatial and temporal patterns of the resulting flux fields are investigated and compared with those derived from satellite observations such as HOAPS, from blended data such as AOFLUX (in the open water cases). A computation of the sensible heat flux at the surface is formulated on the basis of spatial variations of the surface temperature estimated from satellite data. Based on

  12. Coarse Initial Orbit Determination for a Geostationary Satellite Using Single-Epoch GPS Measurements

    Directory of Open Access Journals (Sweden)

    Ghangho Kim

    2015-04-01

    Full Text Available A practical algorithm is proposed for determining the orbit of a geostationary orbit (GEO satellite using single-epoch measurements from a Global Positioning System (GPS receiver under the sparse visibility of the GPS satellites. The algorithm uses three components of a state vector to determine the satellite’s state, even when it is impossible to apply the classical single-point solutions (SPS. Through consideration of the characteristics of the GEO orbital elements and GPS measurements, the components of the state vector are reduced to three. However, the algorithm remains sufficiently accurate for a GEO satellite. The developed algorithm was tested on simulated measurements from two or three GPS satellites, and the calculated maximum position error was found to be less than approximately 40 km or even several kilometers within the geometric range, even when the classical SPS solution was unattainable. In addition, extended Kalman filter (EKF tests of a GEO satellite with the estimated initial state were performed to validate the algorithm. In the EKF, a reliable dynamic model was adapted to reduce the probability of divergence that can be caused by large errors in the initial state.

  13. Fade-durations derived from land-mobile-satellite measurements in Australia

    Science.gov (United States)

    Hase, Yoshihiro; Vogel, Wolfhard J.; Goldhirsh, Julius

    1991-01-01

    Transmissions from the Japanese ETS-V geostationary satellite were measured at L band (1.5 GHz) in a vehicle driving on roads of southeastern Australia. The measurements were part of a program designed to characterize propagation effects due to roadside trees and terrain for mobile satellite service. It is shown that the cumulative distributions of fade and nonfade durations follow a lognormal and power law, respectively. At 1 percent probability, fades last 2-8 m, and nonfades 10-100 m, depending on the degree of shadowing. Phase fluctuations are generally small, allowing the channel characteristics to be estimated from levels only.

  14. Validation of PV performance models using satellite-based irradiance measurements : a case study.

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Joshua S.; Parkins, Andrew (Clean Power Research); Perez, Richard (University at Albany)

    2010-05-01

    Photovoltaic (PV) system performance models are relied upon to provide accurate predictions of energy production for proposed and existing PV systems under a wide variety of environmental conditions. Ground based meteorological measurements are only available from a relatively small number of locations. In contrast, satellite-based radiation and weather data (e.g., SUNY database) are becoming increasingly available for most locations in North America, Europe, and Asia on a 10 x 10 km grid or better. This paper presents a study of how PV performance model results are affected when satellite-based weather data is used in place of ground-based measurements.

  15. A thermodynamic geography: night-time satellite imagery as a proxy measure of emergy.

    Science.gov (United States)

    Coscieme, Luca; Pulselli, Federico M; Bastianoni, Simone; Elvidge, Christopher D; Anderson, Sharolyn; Sutton, Paul C

    2014-11-01

    Night-time satellite imagery enables the measurement, visualization, and mapping of energy consumption in an area. In this paper, an index of the "sum of lights" as observed by night-time satellite imagery within national boundaries is compared with the emergy of the nations. Emergy is a measure of the solar energy equivalent used, directly or indirectly, to support the processes that characterize the economic activity in a country. Emergy has renewable and non-renewable components. Our results show that the non-renewable component of national emergy use is positively correlated with night-time satellite imagery. This relationship can be used to produce emergy density maps which enable the incorporation of spatially explicit representations of emergy in geographic information systems. The region of Abruzzo (Italy) is used to demonstrate this relationship as a spatially disaggregate case.

  16. Improving knowledge of the surface salinity annual cycle with Aquarius satellite measurements

    Science.gov (United States)

    Lagerloef, G. S. E.

    2016-12-01

    To improve knowledge of the ocean surface salinity annual cycle, and its link to global precipitation patterns, remains a key science measurement objective for satellites. The Aquarius satellite data are applied here to address this, and the analysis is not as straightforward as it may seem. Sensor calibration is considered carefully to ensure that seasonality in external calibration data sources do not alias the satellite measurements. For example, quasi-monthly calibration error signals were identified early in the Aquarius mission. Subsequently, Aquarius data processing has relied primarily on an ocean target calibration method, whereby the satellite observations were co-located with output from the US Navy operational HYCOM model to adjust for these quasi-monthly calibration drifts. It was later determined that HYCOM salinity fields are themselves adjusted with a climatological restoring term, that imprints the seasonal climatology signal on the sensor calibration. When that output is compared with a parallel Aquarius data processing that bypasses the HYCOM ocean target calibration, and substitutes a simulation of the sensor electronics, the globally averaged output show very different annual signals between these trials. A modified ocean-target calibration, that employs satellite data matched directly with the in situ observations, is presently being investigated. The methodology uses signal processing to separate the satellite-in situ differences related to the sensor calibration from geophysical error sources. This remains a work-in-progress, and the results, with any unresolved issues, will be discussed. The presentation will also provide a very brief summary of Aquarius scientific accomplishments, the final "legacy" data set production, and the program to continue salinity data processing from other satellites.

  17. Oceanography from satellites

    Science.gov (United States)

    Wilson, W. S.

    1981-01-01

    It is pointed out that oceanographers have benefited from the space program mainly through the increased efficiency it has brought to ship operations. For example, the Transit navigation system has enabled oceanographers to compile detailed maps of sea-floor properties and to more accurately locate moored subsurface instrumentation. General descriptions are given of instruments used in satellite observations (altimeter, color scanner, infrared radiometer, microwave radiometer, scatterometer, synthetic aperture radar). It is pointed out that because of the large volume of data that satellite instruments generate, the development of algorithms for converting the data into a form expressed in geophysical units has become especially important.

  18. Saharan dust detection using multi-sensor satellite measurements.

    Science.gov (United States)

    Madhavan, Sriharsha; Qu, John J; Hao, X

    2017-02-01

    Contemporary scientists have vested interest in trying to understand the climatology of the North Atlantic Basin since this region is considered as the genesis for hurricane formation that eventually get shipped to the tropical Atlantic region and the Caribbean. The effects of atmospheric water cycle and the climate of West Africa and the Atlantic basin are hugely impacted by the radiative forcing of Saharan dust. The focus area in this paper would be to improve the dust detection schemes by employing the use of multi sensor measurements in the thermal emissive wavelengths using legacy sensors such as Terra (T) and Aqua (A) MODerate-resolution Imaging Spectroradiometer (MODIS), fusing with Ozone Monitoring Instrument (OMI). Previous work by Hao and Qu (2007) had considered a limited number of thermal infrared channels which led to a correlation coefficient R(2) value of 0.765 between the Aerosol Optical Thickness (AOT) at 550 nm and the modeled dust index. In this work, we extend the thermal infrared based dust detection by employing additional channels: the 8.55 μm which has shown high sensitivity to the Saharan dust, along with water vapor channel of 7.1 μm and cloud top channel of 13.1 μm. Also, the dust pixels were clearly identified using the OMI based aerosol types. The dust pixels were cleanly segregated from the other aerosol types such as sulfates, biomass, and other carbonaceous aerosols. These improvements led to a much higher correlation coefficient R(2) value of 0.85 between the modified dust index and the AOT in comparison to the previous work. The key limitations from the current AOT products based on MODIS and were put to test by validating the improved dust detection algorithm. Two improvements were noted. First, the dust measurement radiometry using MODIS is significantly improved by at least an order of 2. Second the spatial measurements are enhanced by a factor of at least 10.

  19. Saharan dust detection using multi-sensor satellite measurements

    Directory of Open Access Journals (Sweden)

    Sriharsha Madhavan

    2017-02-01

    Full Text Available Contemporary scientists have vested interest in trying to understand the climatology of the North Atlantic Basin since this region is considered as the genesis for hurricane formation that eventually get shipped to the tropical Atlantic region and the Caribbean. The effects of atmospheric water cycle and the climate of West Africa and the Atlantic basin are hugely impacted by the radiative forcing of Saharan dust. The focus area in this paper would be to improve the dust detection schemes by employing the use of multi sensor measurements in the thermal emissive wavelengths using legacy sensors such as Terra (T and Aqua (A MODerate-resolution Imaging Spectroradiometer (MODIS, fusing with Ozone Monitoring Instrument (OMI. Previous work by Hao and Qu (2007 had considered a limited number of thermal infrared channels which led to a correlation coefficient R2 value of 0.765 between the Aerosol Optical Thickness (AOT at 550 nm and the modeled dust index. In this work, we extend the thermal infrared based dust detection by employing additional channels: the 8.55 μm which has shown high sensitivity to the Saharan dust, along with water vapor channel of 7.1 μm and cloud top channel of 13.1 μm. Also, the dust pixels were clearly identified using the OMI based aerosol types. The dust pixels were cleanly segregated from the other aerosol types such as sulfates, biomass, and other carbonaceous aerosols. These improvements led to a much higher correlation coefficient R2 value of 0.85 between the modified dust index and the AOT in comparison to the previous work. The key limitations from the current AOT products based on MODIS and were put to test by validating the improved dust detection algorithm. Two improvements were noted. First, the dust measurement radiometry using MODIS is significantly improved by at least an order of 2. Second the spatial measurements are enhanced by a factor of at least 10.

  20. Japanese Global Precipitation Measurement (GPM) mission status and application of satellite-based global rainfall map

    Science.gov (United States)

    Kachi, Misako; Shimizu, Shuji; Kubota, Takuji; Yoshida, Naofumi; Oki, Riko; Kojima, Masahiro; Iguchi, Toshio; Nakamura, Kenji

    2010-05-01

    As accuracy of satellite precipitation estimates improves and observation frequency increases, application of those data to societal benefit areas, such as weather forecasts and flood predictions, is expected, in addition to research of precipitation climatology to analyze precipitation systems. There is, however, limitation on single satellite observation in coverage and frequency. Currently, the Global Precipitation Measurement (GPM) mission is scheduled under international collaboration to fulfill various user requirements that cannot be achieved by the single satellite, like the Tropical Rainfall Measurement Mission (TRMM). The GPM mission is an international mission to achieve high-accurate and high-frequent rainfall observation over a global area. GPM is composed of a TRMM-like non-sun-synchronous orbit satellite (GPM core satellite) and constellation of satellites carrying microwave radiometer instruments. The GPM core satellite carries the Dual-frequency Precipitation Radar (DPR), which is being developed by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT), and microwave radiometer provided by the National Aeronautics and Space Administration (NASA). Development of DPR instrument is in good progress for scheduled launch in 2013, and DPR Critical Design Review has completed in July - September 2009. Constellation satellites, which carry a microwave imager and/or sounder, are planned to be launched around 2013 by each partner agency for its own purpose, and will contribute to extending coverage and increasing frequency. JAXA's future mission, the Global Change Observation Mission (GCOM) - Water (GCOM-W) satellite will be one of constellation satellites. The first generation of GCOM-W satellite is scheduled to be launched in 2011, and it carries the Advanced Microwave Scanning Radiometer 2 (AMSR2), which is being developed based on the experience of the AMSR-E on EOS Aqua satellite

  1. Support scattering effects on low-gain satellite antenna pattern measurements

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen

    1973-01-01

    The purpose of the present investigation is to determine the difference between the scattering effects from two types of supports on satellite antenna pattern measurements. The difference in scattering effects is estimated by comparing low-gain antenna patterns recorded when using a foam tower an...

  2. Derivation of the radiation budget at ground level from satellite measurements

    Science.gov (United States)

    Raschke, E.

    1982-01-01

    Determination of the Earth radiaton budget and progress in measurement of the budget components and in the treatment of imaging data from satellites are described. Methods for calculating the radiation budget in a general circulation model, radiative transfer characteristics of clouds, computation of solar radiation at ground level using meteorological data and development of a 10-channel radiometer are discussed.

  3. Linear and Nonlinear Relative Navigation Strategies for Small Satellite Formation Flying Based on Relative Position Measurement

    Science.gov (United States)

    Zhang, Xiaomin; Zheng, You

    Based on linear and nonlinear mathematical model of spacecraft formation flying and technology of relative position measurement of small satellites, the linear and nonlinear relative navigation strategies are developed in this paper. The dynamical characteristics of multi spacecraft formation flying have been researched in many references, including the authors' several International Astronautical Congress papers with numbers of IAF-98-A.2.06, IAA-99-IAA.11.1.09, IAA-01-IAA.11.4.08. Under conditions of short distance and short time, the linear model can describe relative orbit motion; otherwise, nonlinear model must be adopted. Furthermore the means of measurement and their error will influence relative navigation. Thus three kinds of relative navigation strategy are progressed. With consideration of difficulty in relative velocity measurement of small satellites, the three relative navigation strategies are proposed and only depend on sequential data of relative position through measuring the relative distance and relative orientation. The first kind of relative navigation strategy is based on linear model. The second relative navigation strategy is based on nonlinear model, with inclusion of the second order item. In fact the measurement error can not be avoided especially for small satellites, it is mainly considered in the third relative navigation strategy. This research is theoretical yet and a series of formulas of relative navigation are presented in this paper. Also the authors analyzed the three strategies qualitatively and quantitatively. According to results of simulation, the ranges of application are indicated and suggested in allusion to the three strategies of relative navigation. On the view of authors, the relative navigation strategies for small satellite formation flying based on relative position measurement are significant for engineering of small satellite formation flying.

  4. Pico satellite attitude estimation via Robust Unscented Kalman Filter in the presence of measurement faults.

    Science.gov (United States)

    Soken, Halil Ersin; Hajiyev, Chingiz

    2010-07-01

    In the normal operation conditions of a pico satellite, a conventional Unscented Kalman Filter (UKF) gives sufficiently good estimation results. However, if the measurements are not reliable because of any kind of malfunction in the estimation system, UKF gives inaccurate results and diverges by time. This study introduces Robust Unscented Kalman Filter (RUKF) algorithms with the filter gain correction for the case of measurement malfunctions. By the use of defined variables named as measurement noise scale factor, the faulty measurements are taken into consideration with a small weight, and the estimations are corrected without affecting the characteristics of the accurate ones. Two different RUKF algorithms, one with single scale factor and one with multiple scale factors, are proposed and applied for the attitude estimation process of a pico satellite. The results of these algorithms are compared for different types of measurement faults in different estimation scenarios and recommendations about their applications are given.

  5. Long-term stability of TES satellite radiance measurements

    Directory of Open Access Journals (Sweden)

    T. C. Connor

    2011-07-01

    Full Text Available The utilization of Tropospheric Emission Spectrometer (TES Level 2 (L2 retrieval products for the purpose of assessing long term changes in atmospheric trace gas composition requires knowledge of the overall radiometric stability of the Level 1B (L1B radiances. The purpose of this study is to evaluate the stability of the radiometric calibration of the TES instrument by analyzing the difference between measured and calculated brightness temperatures in selected window regions of the spectrum. The Global Modeling and Assimilation Office (GMAO profiles for temperature and water vapor and the Real-Time Global Sea Surface Temperature (RTGSST are used as input to the Optimal Spectral Sampling (OSS radiative transfer model to calculate the simulated spectra. The TES reference measurements selected cover a 4-year period of time from mid 2005 through mid 2009 with the selection criteria being; observation latitudes greater than −30° and less than 30°, over ocean, Global Survey mode (nadir view and retrieved cloud optical depth of less than or equal to 0.01. The TES cloud optical depth retrievals are used only for screening purposes and no effects of clouds on the radiances are included in the forward model. This initial screening results in over 55 000 potential reference spectra spanning the four year period. Presented is a trend analysis of the time series of the residuals (observation minus calculations in the TES 2B1, 1B2, 2A1, and 1A1 bands, with the standard deviation of the residuals being approximately equal to 0.6 K for bands 2B1, 1B2, 2A1, and 0.9 K for band 1A1. The analysis demonstrates that the trend in the residuals is not significantly different from zero over the 4-year period. This is one method used to demonstrate that the relative radiometric calibration is stable over time, which is very important for any longer term analysis of TES retrieved products (L2, particularly well-mixed species such as carbon dioxide and methane.

  6. Recovery Of Short Wavelength Geophysical Signals With Future Delay-Doppler Altimeters (Cryosat Ii And Sentinel Type)

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar

    2010-01-01

    A number of geophysical phenomena in the open ocean are still unresolved by conventional 1 Hz altimetry, but could be observed through the potential improvements offered by SAR, or Delay-Doppler (DD), altimetry. The DD altimeter offers the following benefits with respect to conventional satellite...... indicate, that if the Cryosat-II mission meets the mission goals, the possibility of recovering a huge number of geophysical signal not currently mapped and the possibility to recover global gravity to an accuracy of up to twice that known today from conventional satellite altimetry....

  7. ATM Quality of Service Parameters at 45 Mbps Using a Satellite Emulator: Laboratory Measurements

    Science.gov (United States)

    Ivancic, William D.; Bobinsky, Eric A.

    1997-01-01

    Results of 45-Mbps DS3 intermediate-frequency loopback measurements of asynchronous transfer mode (ATM) quality of service parameters (cell error ratio and cell loss ratio) are presented. These tests, which were conducted at the NASA Lewis Research Center in support of satellite-ATM interoperability research, represent initial efforts to quantify the minimum parameters for stringent ATM applications, such as MPEG-1 and MPEG-2 video transmission. Portions of these results were originally presented to the International Telecommunications Union's ITU-R Working Party 4B in February 1996 in support of their Draft Preliminary Recommendation on the Transmission of ATM Traffic via Satellite.

  8. In situ autonomous optical radiometry measurements for satellite ocean color validation in the Western Black Sea

    Directory of Open Access Journals (Sweden)

    G. Zibordi

    2014-12-01

    Full Text Available The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A and the Visible/Infrared Imager/Radiometer Suite (VIIRS, is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the Ocean Color component of the Aerosol Robotic Network (AERONET-OC. The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities with those observed at the Gloria site. Results from the comparison of normalized-water leaving radiance LWN indicate biases of a few percent between satellite derived and in situ data at the center-wavelengths relevant for the determination of chlorophyll a concentration (443–547 nm, or equivalent. Remarkable is the consistency among the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center-wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm and red (i.e., 667 nm, or equivalent center-wavelengths, suggesting difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters.

  9. Regional CalVal of Altimeter Range at Non-Dedicated Sites in Preparation f Sentinel-3

    Science.gov (United States)

    Cancet, M.; Watson, C.; Haines, B.; Bonnefond, P.; Lyard, F.; Femenias, P.; Guinle, T.

    2015-12-01

    In situ calibration ensures regular and long-term control of the altimeter sea surface height (SSH) time series through comparisons with independent records. Usually, in situ calibration and validation of altimeter SSH is undertaken at specific CALVAL sites through the direct comparison of the altimeter data with in situ data [1]. However, NOVELTIS has developed a regional CALVAL technique, which aims at increasing the number and the repeatability of the altimeter bias assessments by determining the altimeter bias both on overflying passes and on satellite passes located far away from the calibration site. In principle this extends the single site approach to a wider regional scale, thus reinforcing the link between the local and the global CALVAL analyses. It also provides a means to maintain a calibration time series through periods of data-outage at a specific dedicated calibration site. The regional method was initially developed at the Corsican calibration sites of Senetosa and Ajaccio. The method was used to compute the biases of Jason-1, Jason-2 and Envisat (before and after the orbit change in 2010) at both sites, and proved its stability and generality through this cross-calibration exercise [2]. These last years, the regional method was successfully implemented at the Californian site of Harvest and at the Australian site of Bass Strait, in close collaboration with JPL and the University of Tasmania, respectively. These recent studies gave the first Envisat absolute bias estimates at non-dedicated sites using the same method, and showed high consistency with the analyses of the global CALVAL teams and the work of the in situ CALVAL teams. These results highlight the numerous advantages of this technique for monitoring missions on any orbits such as the future Sentinel-3 and Jason-CS/Sentinel-6 missions.

  10. Near-nadir microwave specular returns from the sea surface - Altimeter algorithms for wind and wind stress

    Science.gov (United States)

    Wu, Jin

    1992-01-01

    Two approaches have been adopted to construct altimeter wind algorithms: one is based on the mean-square sea surface slope, and the other is based on the Seasat scatterometer wind. Both types of algorithms are critically reviewed with respect to the mechanism governing near-nadir sea returns and the comparison between altimeter and buoy winds. A new algorithm is proposed; it is deduced on the basis of microwave specular reflection and is finely tuned with buoy-measured winds. On the basis of this algorithm and the formula of the wind-stress coefficient, a simple wind-stress algorithm is also proposed.

  11. Vertical Accuracy Assessment of ZY-3 Digital Surface Model Using Icesat/glas Laser Altimeter Data

    Science.gov (United States)

    Li, G.; Tang, X.; Yuan, X.; Zhou, P.; Hu, F.

    2017-05-01

    The Ziyuan-3 (ZY-3) satellite, as the first civilian high resolution surveying and mapping satellite in China, has a very important role in national 1 : 50,000 stereo mapping project. High accuracy digital surface Model (DSMs) can be generated from the three line-array images of ZY-3, and ZY-3 DSMs of China can be produced without using any ground control points (GCPs) by selecting SRTM (Shuttle Radar Topography Mission) and ICESat/GLAS (Ice, Cloud, and land Elevation Satellite, Geo-science Laser Altimeter System) as the datum reference in the Satellite Surveying and Mapping Application Center, which is the key institute that manages and distributes ZY-3 products. To conduct the vertical accuracy evaluation of ZY-3 DSMs of China, three representative regions were chosen and the results were compared to ICESat/GLAS data. The experimental results demonstrated that the root mean square error (RMSE) elevation accuracy of the ZY-3 DSMs was better than 5.0 m, and it even reached to less than 2.5 m in the second region of eastern China. While this work presents preliminary results, it is an important reference for expanding the application of ZY-3 satellite imagery to widespread regions. And the satellite laser altimetry data can be used as referenced data for wide-area DSM evaluation.

  12. Comparison of Satellite-Derived Wind Measurements with Other Wind Measurement Sensors

    Science.gov (United States)

    Susko, Michael; Herman, Leroy

    1995-01-01

    The purpose of this paper is to compare the good data from the Jimsphere launches with the data from the satellite system. By comparing the wind speeds from the Fixed Pedestal System 16 (FPS-16) Radar/Jimsphere Wind System and NASA's 50-MHz Radar Wind Profiler, the validation of winds from Geostationary Operational Environmental Satellite 7 (GOES-7) is performed. This study provides an in situ data quality check for the GOES-7 satellite winds. Comparison was made of the flowfields in the troposphere and the lower stratosphere of case studies of pairs of Jimsphere balloon releases and Radar Wind Profiler winds during Space Shuttle launches. The mean and standard deviation of the zonal component statistics, the meridional component statistics, and the power spectral density curves show good agreement between the two wind sensors. The standard deviation of the u and v components for the STS-37 launch (consisting of five Jimsphere/Radar Wind Profiler data sets) was 1.92 and 1.67 m/s, respectively; for the STS-43 launch (there were six Jimsphere/Wind Profiler data sets) it was 1.39 and 1.44 m/s, respectively. The overall standard deviation was 1.66 m/s for the u component and 1.55 m/s tor the v component, and a standard deviation of 2.27 m/s tor the vector wind difference. The global comparison of satellite with Jimsphere balloon vector winds shows a standard deviation of 3.15 m/s for STS-43 and 4.37 m/s for STS-37. The overall standard deviation of the vector wind was 3.76 m/s, with a root-mean-square vector difference of 4.43 m/s. These data have demonstrated that this unique comparison of the Jimsphere and satellite winds provides excellent ground truth and a frame of reference during testing and validation of satellite data

  13. Quantitative measurements of Jupiter, Saturn, their rings and satellites made from Voyager imaging data

    Science.gov (United States)

    Collins, S. A.; Bunker, A. S.

    1983-01-01

    The Voyager spacecraft cameras use selenium-sulfur slow scan vidicons to convert focused optical images into sensible electrical signals. The vidicon-generated data thus obtained are the basis of measurements of much greater precision than was previously possible, in virtue of their superior linearity, geometric fidelity, and the use of in-flight calibration. Attention is given to positional, radiometric, and dynamical measurements conducted on the basis of vidicon data for the Saturn rings, the Saturn satellites, and the Jupiter atmosphere.

  14. Measurement-based perturbation theory and differential equation parameter estimation for high-precision high-resolution reconstruction of the Earth's gravitational field from satellite tracking measurements

    CERN Document Server

    Xu, Peiliang

    2016-01-01

    The numerical integration method has been routinely used to produce global standard gravitational models from satellite tracking measurements of CHAMP/GRACE types. It is implemented by solving the differential equations of the partial derivatives of a satellite orbit with respect to the unknown harmonic coefficients under the conditions of zero initial values. From the mathematical point of view, satellite gravimetry from satellite tracking is the problem of estimating unknown parameters in the Newton's nonlinear differential equations from satellite tracking measurements. We prove that zero initial values for the partial derivatives are incorrect mathematically and not permitted physically. The numerical integration method, as currently implemented and used in satellite gravimetry and statistics, is groundless. We use three different methods to derive new local solutions to the Newton's nonlinear governing differential equations of motion with a nominal reference orbit. Bearing in mind that satellite orbits ...

  15. Algorithm for Detection of Ground and Canopy Cover in Micropulse Photon-Counting Lidar Altimeter Data in Preparation for the ICESat-2 Mission

    Science.gov (United States)

    Herzfeld, Ute Christina; McDonald, Brian W.; Neumann, Thomas Allen; Wallin, Bruce F.; Neumann, Thomas A.; Markus, Thorsten; Brenner, Anita; Field, Christopher

    2014-01-01

    NASA's Ice, Cloud and Land Elevation Satellite-II (ICESat-2) mission is a decadal survey mission (2016 launch). The mission objectives are to measure land ice elevation, sea ice freeboard, and changes in these variables, as well as to collect measurements over vegetation to facilitate canopy height determination. Two innovative components will characterize the ICESat-2 lidar: 1) collection of elevation data by a multibeam system and 2) application of micropulse lidar (photon-counting) technology. A photon-counting altimeter yields clouds of discrete points, resulting from returns of individual photons, and hence new data analysis techniques are required for elevation determination and association of the returned points to reflectors of interest. The objective of this paper is to derive an algorithm that allows detection of ground under dense canopy and identification of ground and canopy levels in simulated ICESat-2 data, based on airborne observations with a Sigma Space micropulse lidar. The mathematical algorithm uses spatial statistical and discrete mathematical concepts, including radial basis functions, density measures, geometrical anisotropy, eigenvectors, and geostatistical classification parameters and hyperparameters. Validation shows that ground and canopy elevation, and hence canopy height, can be expected to be observable with high accuracy by ICESat-2 for all expected beam energies considered for instrument design (93.01%-99.57% correctly selected points for a beam with expected return of 0.93 mean signals per shot (msp), and 72.85%-98.68% for 0.48 msp). The algorithm derived here is generally applicable for elevation determination from photoncounting lidar altimeter data collected over forested areas, land ice, sea ice, and land surfaces, as well as for cloud detection.

  16. Establishing the Antarctic Dome C community reference standard site towards consistent measurements from Earth observation satellites

    Science.gov (United States)

    Cao, C.; Uprety, S.; Xiong, J.; Wu, A.; Jing, P.; Smith, D.; Chander, G.; Fox, N.; Ungar, S.

    2010-01-01

    Establishing satellite measurement consistency by using common desert sites has become increasingly more important not only for climate change detection but also for quantitative retrievals of geophysical variables in satellite applications. Using the Antarctic Dome C site (75°06′S, 123°21′E, elevation 3.2 km) for satellite radiometric calibration and validation (Cal/Val) is of great interest owing to its unique location and characteristics. The site surface is covered with uniformly distributed permanent snow, and the atmospheric effect is small and relatively constant. In this study, the long-term stability and spectral characteristics of this site are evaluated using well-calibrated satellite instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS). Preliminary results show that despite a few limitations, the site in general is stable in the long term, the bidirectional reflectance distribution function (BRDF) model works well, and the site is most suitable for the Cal/Val of reflective solar bands in the 0.4–1.0 µm range. It was found that for the past decade, the reflectivity change of the site is within 1.35% at 0.64 µm, and interannual variability is within 2%. The site is able to resolve calibration biases between instruments at a level of ~1%. The usefulness of the site is demonstrated by comparing observations from seven satellite instruments involving four space agencies, including OrbView-2–SeaWiFS, Terra–Aqua MODIS, Earth Observing 1 (EO-1) – Hyperion, Meteorological Operational satellite programme (MetOp) – Advanced Very High Resolution Radiometer (AVHRR), Envisat Medium Resolution Imaging Spectrometer (MERIS) – dvanced Along-Track Scanning Radiometer (AATSR), and Landsat 7 Enhanced Thematic Mapper Plus (ETM+). Dome C is a promising candidate site for climate quality calibration of satellite radiometers towards more consistent satellite measurements, as part

  17. Assessment of the quality of OSIRIS mesospheric temperatures using satellite and ground-based measurements

    Directory of Open Access Journals (Sweden)

    P. E. Sheese

    2012-12-01

    Full Text Available The Optical Spectrograph and InfraRed Imaging System (OSIRIS on the Odin satellite is currently in its 12th year of observing the Earth's limb. For the first time, continuous temperature profiles extending from the stratopause to the upper mesosphere have been derived from OSIRIS measurements of Rayleigh-scattered sunlight. Through most of the mesosphere, OSIRIS temperatures are in good agreement with coincident temperature profiles derived from other satellite and ground-based measurements. In the altitude region of 55–80 km, OSIRIS temperatures are typically within 4–5 K of those from the SABER, ACE-FTS, and SOFIE instruments on the TIMED, SciSat-I, and AIM satellites, respectively. The mean differences between individual OSIRIS profiles and those of the other satellite instruments are typically within the combined uncertainties and previously reported biases. OSIRIS temperatures are typically within 2 K of those from the University of Western Ontario's Purple Crow Lidar in the altitude region of 52–79 km, where the mean differences are within combined uncertainties. Near 84 km, OSIRIS temperatures exhibit a cold bias of 10–15 K, which is due to a cold bias in OSIRIS O2 A-band temperatures at 85 km, the upper boundary of the Rayleigh-scatter derived temperatures; and near 48 km OSIRIS temperatures exhibit a cold bias of 5–15 K, which is likely due to multiple-scatter effects that are not taken into account in the retrieval.

  18. Ice Mass Change in Greenland and Antarctica Between 1993 and 2013 from Satellite Gravity Measurements

    Science.gov (United States)

    Talpe, Matthieu J.; Nerem, R. Steven; Forootan, Ehsan; Schmidt, Michael; Lemoine, Frank G.; Enderlin, Ellyn M.; Landerer, Felix W.

    2017-01-01

    We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.

  19. Comparison of the simulated performance of a VSAT satellite link with measurements

    Science.gov (United States)

    Mwanakatwe, M.; Willis, M. J.; Evans, B. G.

    1991-06-01

    The transmisson performance of a Ka-band VSAT system (CODE) has been simulated to verify the systems design and to demonstrate the adequacy of the implementation margin and phase noise. A detailed simulation of phase noise effects on VSAT systems design is also presented. Hardware measurements and BOSS simulations for the test set-up show a good agreement for values of Eb/N0 up to 7dB. The simulated results indicate an increased error when the TWTA is operated in the nonlinear region, with the simulations indicating larger degradation than the measurement. The phase noise performance of the digital TRL modem is found to be consistently better than that of the simulated model. There appears to be closer agreement with the BOSS simulations than with the TOPSIM III simulations. The discrepancy between the TOPSIM III and BOSS phase noise simulations was only resolved by measurements taken using the Olympus satellite and BTI satellite simulator.

  20. The Measurement of Landfill Gas Emissions with the Orbiting Carbon Observatory and CarbonSAT Satellites

    Science.gov (United States)

    Vigil, S. A.; Bovensmann, H.

    2010-12-01

    Landfill gas is a significant contributor to anthropogenic emissions of CH4 and CO2. The U.S. Environmental Protection Agency has estimated the total U.S. 2007 emissions of the CH4 component of landfill gas at 132.9 Tg CO2 Equivalent. This compares to total CH4 emission from all US sources in 2007 at 585.3 Tg CO2 Equivalent. Worldwide CH4 emissions from landfill gas have been estimated at 668 Tg CO2 Equivalent. Satellite remote sensing can also be used to characterize landfill gas emissions. The NASA Orbiting Carbon Observatory (OCO-2) and the proposed CarbonSAT (University of Bremen) satellites are particularly suited for this purpose. The Orbiting Carbon Observatory (OCO) was designed to provided high spatial resolution ( developed countries. In general, landfills in the developed countries have landfill gas control system ground based landfill gas monitoring systems. These ground-based measurements can be used to calibrate OCO-2 and CarbonSAT landfill gas measurements. OCO-2 and CarbonSAT can be used to measure landfill emissions from the large landfills and open dumps of the emerging megacities in the developing world where accurate ground measurements are not available. For example Mexico City generates 26,000 MT of municipal solid waste that is disposed of in two uncontrolled landfills. Similar conditions exist in Asia, Latin America, and Africa. Satellite based measurements of these landfill gas emissions could help prioritize greenhouse gas remediation projects for these countries.

  1. Vertical Profiles of Aerosol Optical Properties Over Central Illinois and Comparison with Surface and Satellite Measurements

    Science.gov (United States)

    Sheridan P. J.; Andrews, E.; Ogren, J A.; Tackett, J. L.; Winker, D. M.

    2012-01-01

    Between June 2006 and September 2009, an instrumented light aircraft measured over 400 vertical profiles of aerosol and trace gas properties over eastern and central Illinois. The primary objectives of this program were to (1) measure the in situ aerosol properties and determine their vertical and temporal variability and (2) relate these aircraft measurements to concurrent surface and satellite measurements. Underflights of the CALIPSO satellite show reasonable agreement in a majority of retrieved profiles between aircraft-measured extinction at 532 nm (adjusted to ambient relative humidity) and CALIPSO-retrieved extinction, and suggest that routine aircraft profiling programs can be used to better understand and validate satellite retrieval algorithms. CALIPSO tended to overestimate the aerosol extinction at this location in some boundary layer flight segments when scattered or broken clouds were present, which could be related to problems with CALIPSO cloud screening methods. The in situ aircraft-collected aerosol data suggest extinction thresholds for the likelihood of aerosol layers being detected by the CALIOP lidar. These statistical data offer guidance as to the likelihood of CALIPSO's ability to retrieve aerosol extinction at various locations around the globe.

  2. A new, high-resolution digital elevation model of Greenland fully validated with airborne laser altimeter data

    DEFF Research Database (Denmark)

    Bamber, J.L.; Ekholm, Simon; Krabill, W.B.

    2001-01-01

    A new digital elevation model of the Greenland ice sheet and surrounding rock outcrops has been produced at 1-km postings from a comprehensive suite of satellite remote sensing and cartographic data sets. Height data over the ice sheet were mainly from ERS-1 and Geosat radar altimetry. These data...... coverage existed. The data were interpolated onto a regular grid with a spacing of similar to1 km. The accuracy of the resultant digital elevation model over the ice sheet was assessed using independent and spatially extensive measurements from an airborne laser altimeter that had an accuracy of between 10...... and 12 cm. In a comparison with the laser altimetry the digital elevation model was found to have a slope-dependent accuracy ranging from -1.04 +/-1.98 m to -0.06 +/- 14.33 m over the ice sheet for a slope range of 0.0-1.0 degrees. The mean accuracy over the whole ice sheet was -0.33 +/-6.97 m. Over...

  3. Comprehensive Comparisons of Satellite Data, Signals, and Measurements between the BeiDou Navigation Satellite System and the Global Positioning System.

    Science.gov (United States)

    Jan, Shau-Shiun; Tao, An-Lin

    2016-05-13

    The Chinese BeiDou navigation satellite system (BDS) aims to provide global positioning service by 2020. The combined use of BDS and Global Positioning System (GPS) is proposed to provide navigation service with more stringent requirements. Actual satellite data, signals and measurements were collected for more than one month to analyze the positioning service qualities from both BDS and GPS. In addition to the conversions of coordinate and timing system, five data quality analysis (DQA) methods, three signal quality analysis (SQA) methods, and four measurement quality analysis (MQA) methods are proposed in this paper to improve the integrated positioning performance of BDS and GPS. As shown in the experiment results, issues related to BDS and GPS are resolved by the above proposed quality analysis methods. Thus, the anomalies in satellite data, signals and measurements can be detected by following the suggested resolutions to enhance the positioning performance of the combined use of BDS and GPS in the Asia Pacific region.

  4. Integrated Multi-Point Space Plasma Measurements With Four Ionospheric Satellites

    Science.gov (United States)

    Siefring, C. L.; Bernhardt, P. A.; Selcher, C.; Wilkens, M. R.; McHarg, M. G.; Krause, L.; Chun, F.; Enloe, L.; Panholzer, R.; Sakoda, D.; Phelps, R.; D Roussel-Dupre, D.; Colestock, P.; Close, S.

    2006-12-01

    The STP-1 launch scheduled for late 2006 will place four satellites with ionospheric plasma diagnostics into the same nearly circular orbit with an altitude of 560 km and inclination of 35.4°. The satellites will allow for unique multipoint measurements of ionospheric scintillations and their causes. Both the radio and in-situ diagnostics will provide coverage of low- and mid-latitudes. The four satellites, STPSat1, NPSat1, FalconSat3, and CFE will follow the same ground-track but because of drag and mass differences their relative velocities will be different and vary during the lifetime of the satellites. The four satellites will start close together; separate over a few months and coming back together with near conjunctions at six and eight months. Two satellite conjunctions between NPSat1 and STPSat1 will occur most often, approximately one month apart at the end of the mission. STPSat1 is equipped with CITRIS (sCintillation and TEC Receiver In Space) which will measure scintillations in the VHF, UHF and L-band along with measuring Total Electron Content (TEC) along the propagation path. NPSat1 will carry a three-frequency CERTO (Coherent Electromagnetic Radio TOmography) Beacon which broadcasts phase-coherent signals at 150.012 MHz, 400.032 MHz, and 1066.752 MHz. CITRIS will be able to measure TEC and Scintillations along the orbital path (propagation path from NPSat1 to STPSat1) as well as between the CITRIS and the ground. NPSat1 carries electron and ion saturation Langmuir Probes, while FalconSat3 carries the FLAPS (FLAt Plasma Spectrometer) and PLANE (Plasma Local Anomalous Noise Environment). The in-situ diagnostic complement the CITRIS/CERTO radio techniques in many ways. The CIBOLA Flight Experiment (CFE) contains a wide band receiver covering 100 to 500 MHz. The CFE data can be processed to show distortion of wide-band modulations by ionospheric irregularities. CFE and CITRIS can record ground transmissions from the French DORIS beacons which radiate

  5. A decade of ERS satellite orbits and altimetry

    NARCIS (Netherlands)

    Scharroo, R.

    2002-01-01

    The First European Remote Sensing Satellite, ERS-1, was launched in July 1991, fol- lowed by ERS-2 in April 1995. Both satellites carry a radar altimeter to serve oper- ational applications and scientific research in the fields of geodesy, oceanography, glaciology and meteorology. Together, the sate

  6. Satellite laser ranging measurements in South Africa: Contributions to earth system sciences

    Directory of Open Access Journals (Sweden)

    Christina M. Botai

    2015-03-01

    Full Text Available This contribution reassesses progress in the development of satellite laser ranging (SLR technology and its scientific and societal applications in South Africa. We first highlight the current global SLR tracking stations within the framework of the International Laser Ranging Service (ILRS and the artificial satellites currently being tracked by these stations. In particular, the present work focuses on analysing SLR measurements at Hartebeesthoek Radio Astronomy Observatory (HartRAO, South Africa, based on the MOBLAS-6 SLR configuration. Generally, there is a weak geometry of ILRS stations in the southern hemisphere and the SLR tracking station at HartRAO is the only active ILRS station operating on the African continent. The SLR-derived products such as station positions and velocities, satellite orbits, components of earth's gravity field and their temporal variations, earth orientation parameters are collected, merged, achieved and distributed by the ILRS under the Crustal Dynamic Data Information System. These products are used in various research fields such as detection and monitoring of tectonic plate motion, crustal deformation, earth rotation, polar motion, and the establishment and monitoring of International Terrestrial Reference Frames, as well as modelling of the spatio-temporal variations of the earth's gravity field. The MOBLAS-6 tracking station is collocated with other geodetic techniques such as very long baseline interferometry and Global Navigation Satellite Systems, thus making this observatory a fiducial geodetic location. Some applications of the SLR data products are described within the context of earth system science.

  7. Energetic particle radiations measured by particle detector on board CBERS-1 satellite

    Institute of Scientific and Technical Information of China (English)

    HAO YongQiang; XIAO Zuo; ZOU Hong; ZHANG DongHe

    2007-01-01

    Using the data measured by energetic particle detector on board CBERS-01 and -02 for the past five years, statistics was made to show the general features of MeV electrons and protons along a solar synchronous orbit at an altitude of 780 km. This height is in the bottom region of the Earth's radiation belts. Detectors are inside the satellite cabinet and such continuous monitoring of particle radiation environment inside a satellite has seldom conducted so far. After a proper and careful treatment, it is indicated that the data inside satellite are well correlated with the radiation environment outside. Besides the agreement of the general distribution characteristics of energetic electrons and protons with similar observations from other satellites, attention is particularly paid to the disturbed conditions. Variations of particle fluxes are closely related with solar proton events, in general, electron fluxes of outer belt are well correlated with Dst index after three days' delay while the electron injection occurred almost at the same day during great magnetic storms. It is confirmed that both energetic electrons and protons appear in the Polar Cap region only after the solar proton events.

  8. Heavy precipitation retrieval from combined satellite observations and ground-based lightning measurements

    Science.gov (United States)

    Mugnai, A.; Dietrich, S.; Casella, D.; di Paola, F.; Formenton, M.; Sanò, P.

    2010-09-01

    We have developed a series of algorithms for the retrieval of precipitation (especially, heavy precipitation) over the Mediterranean area using satellite observations from the available microwave (MW) radiometers onboard low Earth orbit (LEO) satellites and from the visible-infrared (VIS-IR) SEVIRI radiometer onboard the European geosynchronous (GEO) satellite Meteosat Second Generation (MSG), in conjunction with lightning data from ground-based networks - such as ZEUS and LINET. These are: • A new approach for precipitation retrieval from space (which we call the Cloud Dynamics and Radiation Database approach, CDRD) that incorporates lightning and environmental/dynamical information in addition to the upwelling microwave brightness temperatures (TB’s) so as to reduce the retrieval uncertainty and improve the retrieval performance; • A new combined MW-IR technique for producing frequent precipitation retrievals from space (which we call PM-GCD technique), that uses passive-microwave (PM) retrievals in conjunction with lightning information and the Global Convection Detection (GCD) technique to discriminate deep convective clouds within the GEO observations; • A new morphing approach (which we call the Lightning-based Precipitation Evolving Technique, L-PET) that uses the available lightning measurements for propagating the rainfall estimates from satellite-borne MW radiometers to a much higher time resolution than the MW observations. We will present and discuss our combined MW/IR/lightning precipitation algorithms and analyses with special reference to some case studies over the western Mediterranean.

  9. Are there urban signatures in the tropospheric ozone column products derived from satellite measurements?

    Directory of Open Access Journals (Sweden)

    J. Kar

    2010-06-01

    Full Text Available In view of the proposed geostationary satellite missions to monitor air quality from space, it is important to first assess the capability of the current suite of satellite instruments to provide information on the urban scale pollution. We explore the possibility of detecting urban signatures in the tropospheric column ozone data derived from Total Ozone Mapping Spectrometer (TOMS/Solar Backscattered Ultraviolet (SBUV and Ozone Monitoring Instrument (OMI/Microwave Limb Sounder (MLS satellite data. We find that distinct isolated plumes of tropospheric ozone near several large and polluted cities around the world may be detected in these data sets. The ozone plumes generally correspond with the tropospheric column NO2 plumes around these cities as observed by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY instrument. Similar plumes are also seen in tropospheric mean ozone mixing ratio distribution after accounting for the surface and tropopause pressure variations. The total column ozone retrievals indicate fairly significant sensitivity to the lower troposphere over the polluted land areas, which might help explain these detections. These results indicate that ultraviolet (UV measurements may, in principle, be able to capture the urban signatures and may have implications for future missions using geostationary satellites.

  10. Application of remote sensing to thermal pollution analysis. [satellite sea surface temperature measurement assessment

    Science.gov (United States)

    Hiser, H. W.; Lee, S. S.; Veziroglu, T. N.; Sengupta, S.

    1975-01-01

    A comprehensive numerical model development program for near-field thermal plume discharge and far field general circulation in coastal regions is being carried on at the University of Miami Clean Energy Research Institute. The objective of the program is to develop a generalized, three-dimensional, predictive model for thermal pollution studies. Two regions of specific application of the model are the power plants sites at the Biscayne Bay and Hutchinson Island area along the Florida coastline. Remote sensing from aircraft as well as satellites are used in parallel with in situ measurements to provide information needed for the development and verification of the mathematical model. This paper describes the efforts that have been made to identify problems and limitations of the presently available satellite data and to develop methods for enhancing and enlarging thermal infrared displays for mesoscale sea surface temperature measurements.

  11. Air Quality Measurements from Satellites during the 2008 Beijing Olympics and Paralympics

    Science.gov (United States)

    Witte, J. C.; Schoeberl, M.; Douglass, A.; Gleason, J.; Krotkov, N.; Gille, J.; Pickering, K.; Livesey, N.

    2009-05-01

    In preparation for the Olympic and Paralympic games in August and September 2008 in Beijing, China, the Chinese government imposed strict controls on industrial emissions and motor vehicle traffic in and around the city and vicinity before and during the events to improve the air quality for the competitors and visitors. To test the efficacy of these measures, we used satellite data from NASA's Aura/Ozone Monitoring Instrument (OMI) and Terra/Measurements Of Pollution In The Troposphere (MOPITT) over Beijing and surrounding areas during the Olympic and Paralympic period. The satellite instruments recorded significant reductions in nitrogen dioxide of up to 50%, up to 10% in tropospheric column ozone, 20-40% in boundary layer sulfur dioxide, and 10-20% reductions in carbon monoxide concentrations below 700 hPa.

  12. Optimality of incompletely measurable active and passive attitude control systems. [for satellites

    Science.gov (United States)

    Schiehlen, W.; Popp, K.

    1973-01-01

    Passive attitude control systems and active systems with incomplete state measurements are only suboptimal systems in the sense of optimal control theory, since optimal systems require complete state measurements or state estimations. An optimal system, then, requires additional hardware (especially in the case of flexible spacecraft) which results in higher costs. Therefore, it is a real engineering problem to determine how much an optimal system exceeds the suboptimal system, or in other words, what is the suboptimal system's degree of optimality. The problem will be treated in three steps: (1) definition of the degree of optimality for linear, time-invariant systems; (2) a computation method using the quadratic cost functional; (3) application to a gravity-gradient stabilized three-body satellite and a spinning flexible satellite.

  13. Validation of aerosol measurements by the satellite sensors SAM II and Sage

    Science.gov (United States)

    Russell, P. B.; Mccormick, M. P.; Swissler, T. J.

    1982-01-01

    A global data base on stratospheric aerosols has been obtained with the aid of the sensors SAM II and SAGE since the satellites carrying the sensors were launched in October 1978 and Feburary 1979, respectively. Several major comparative experiments have been conducted to acquire correlative data for validating the extinction profiles measured by these satellite sensors. The present investigation has the objective to present results from the first two of these experiments, which were conducted at Sondrestorm, Greenland, in November 1978, and at Poker Flat, Alaska, in July 1979. In both experiments, extinction profiles derived from the correlative sensors (dustsonde, lidar, filter, wire impactor) agreed, to within their respective uncertainties, with the extinction profiles measured by SAM II and SAGE (which in turn agreed with each other).

  14. FPGA Sequencer for Radar Altimeter Applications

    Science.gov (United States)

    Berkun, Andrew C.; Pollard, Brian D.; Chen, Curtis W.

    2011-01-01

    A sequencer for a radar altimeter provides accurate attitude information for a reliable soft landing of the Mars Science Laboratory (MSL). This is a field-programmable- gate-array (FPGA)-only implementation. A table loaded externally into the FPGA controls timing, processing, and decision structures. Radar is memory-less and does not use previous acquisitions to assist in the current acquisition. All cycles complete in exactly 50 milliseconds, regardless of range or whether a target was found. A RAM (random access memory) within the FPGA holds instructions for up to 15 sets. For each set, timing is run, echoes are processed, and a comparison is made. If a target is seen, more detailed processing is run on that set. If no target is seen, the next set is tried. When all sets have been run, the FPGA terminates and waits for the next 50-millisecond event. This setup simplifies testing and improves reliability. A single vertex chip does the work of an entire assembly. Output products require minor processing to become range and velocity. This technology is the heart of the Terminal Descent Sensor, which is an integral part of the Entry Decent and Landing system for MSL. In addition, it is a strong candidate for manned landings on Mars or the Moon.

  15. Relative performance of future altimeter systems and tide gauges in constraining a model of North Sea high-frequency barotropic dynamics

    Science.gov (United States)

    Mourre, Baptiste; de Mey, Pierre; Ménard, Yves; Lyard, Florent; Le Provost, Christian

    2006-12-01

    We evaluate in this paper the ability of several altimeter systems, considered separately as well as together with tide gauges, to control the time evolution of a barotropic model of the North Sea shelf. This evaluation is performed in the framework of the particular model errors due to uncertainties in bathymetry. An Ensemble Kalman Filter (EnKF) data assimilation approach is adopted, and observing-systems simulation experiments (OSSEs) are carried out using ensemble spread statistics. The skill criterion for the comparison of observing networks is, therefore, not based on the misfit between two simulations, as done in classic twin experiments, but on the reduction of ensemble variance occurring as a consequence of the assimilation. Future altimeter systems, such as the Wide Swath Ocean Altimeter (WSOA) and satellite constellations, are considered in this work. A single WSOA exhibits, for instance, similar performance as two-nadir satellites in terms of sea-level correction, and is better than three satellites in terms of model velocity control. Generally speaking, the temporal resolution of observations is shown to be of major importance for controlling the model error in these experiments. This result is clearly related to the focus adopted in this study on the specific high-frequency response of the ocean to meteorological forcing. Altimeter systems lack adequate temporal sampling for properly correcting the major part of model error in this context, whereas tide gauges, which provide a much finer time resolution, lead to better global statistical performance. When looking into further detail, tide gauges and altimetry are demonstrated to exhibit an interesting complementary character over the whole shelf, as tide gauge networks make it possible to properly control model error in a ˜100-km coastal band, while high-resolution altimeter systems are more efficient farther from the coast.

  16. Study of Ice Crystal Orientation in Cirrus Clouds based on Satellite Polarized Radiance Measurements

    OpenAIRE

    Noel, Vincent; Chepfer, Hélène

    2004-01-01

    International audience; The goal of this paper is to retrieve information about ice particle orientation in cirrus clouds. This is achieved by comparing simulations of sunlight reflection on a cirrus cloud with measurements of polarized radiances from the spaceborne instrument Polarization and Directionality of the Earth's Reflectance (POLDER-1) on Advanced Earth Observing Satellite-1 (ADEOS-1). Results show that horizontal orientation of cr ystals can be spotted by the presence of a local ma...

  17. Environmental Satellites: Strategy Needed to Sustain Critical Climate and Space Weather Measurements

    Science.gov (United States)

    2010-04-01

    together. For example, climate measurements have allowed scientists to better understand the effect of deforestation on how the earth absorbs heat, retains...Geostationary Operational Environmental Satellites: Progress Has Been Made, but Improvements Are Needed to Effectively Manage Risks, GAO-08-18 (Washington...color; and atmospheric observations such as greenhouse gas levels (e.g., carbon dioxide), aerosol and dust particles, and moisture concentration. When

  18. Combining satellite, aerial and ground measurements to assess forest carbon stocks in Democratic Republic of Congo

    Science.gov (United States)

    Beaumont, Benjamin; Bouvy, Alban; Stephenne, Nathalie; Mathoux, Pierre; Bastin, Jean-François; Baudot, Yves; Akkermans, Tom

    2015-04-01

    Monitoring tropical forest carbon stocks changes has been a rising topic in the recent years as a result of REDD+ mechanisms negotiations. Such monitoring will be mandatory for each project/country willing to benefit from these financial incentives in the future. Aerial and satellite remote sensing technologies offer cost advantages in implementing large scale forest inventories. Despite the recent progress made in the use of airborne LiDAR for carbon stocks estimation, no widely operational and cost effective method has yet been delivered for central Africa forest monitoring. Within the Maï Ndombe region of Democratic Republic of Congo, the EO4REDD project develops a method combining satellite, aerial and ground measurements. This combination is done in three steps: [1] mapping and quantifying forest cover changes using an object-based semi-automatic change detection (deforestation and forest degradation) methodology based on very high resolution satellite imagery (RapidEye), [2] developing an allometric linear model for above ground biomass measurements based on dendrometric parameters (tree crown areas and heights) extracted from airborne stereoscopic image pairs and calibrated using ground measurements of individual trees on a data set of 18 one hectare plots and [3] relating these two products to assess carbon stocks changes at a regional scale. Given the high accuracies obtained in [1] (> 80% for deforestation and 77% for forest degradation) and the suitable, but still to be improved with a larger calibrating sample, model (R² of 0.7) obtained in [2], EO4REDD products can be seen as a valid and replicable option for carbon stocks monitoring in tropical forests. Further improvements are planned to strengthen the cost effectiveness value and the REDD+ suitability in the second phase of EO4REDD. This second phase will include [A] specific model developments per forest type; [B] measurements of afforestation, reforestation and natural regeneration processes and

  19. Comparison of NO2 vertical profiles from satellite and ground based measurements over Antarctica

    OpenAIRE

    Kulkarni, Pavan; Bortoli, Daniele; Costa, Maria João; Silva, Ana Maria; Ravegnani, Fabrizio; Giovanelli, Giorgio

    2011-01-01

    The Intercomparison of nitrogen dioxide (NO2) vertical profiles, derived from the satellite based HALogen Occultation Experiment (HALOE) measurements and from the ground based UV-VIS spectrometer GASCOD (Gas Analyzer Spectrometer Correlating Optical Differences) observations at the Mario Zucchelli Station (MZS), in Antarctica, are done for the first time. It is shown here that both datasets are in good agreement showing the same features in terms of magnitude, profile structure, a...

  20. Amazon vegetation greenness as measured by satellite sensors over the last decade

    OpenAIRE

    Atkinson, P.M.; Dash, J.; Jeganathan, C.

    2011-01-01

    [1] During the last decade two major drought events, one in 2005 and another in 2010, occurred in the Amazon basin. Several studies have claimed the ability to detect the effect of these droughts on Amazon vegetation response, measured through satellite sensor vegetation indices (VIs). Such monitoring capability is important as it potentially links climate changes (increasing frequency and severity of drought), vegetation response as observed through vegetation greenness, and land-atmosphere ...

  1. Comparison of advanced Arctic Ocean model sea ice fields to satellite derived measurements

    OpenAIRE

    Dimitriou, David S.

    1998-01-01

    Approved for public release; distribution is unlimited Numerical models have proven integral to the study of climate dynamics. Sea ice models are critical to the improvement of general circulation models used to study the global climate. The object of this study is to evaluate a high resolution ice-ocean coupled model by comparing it to derived measurements from SMMR and SSM/I satellite observations. Utilized for this study was the NASA Goddard Space Flight (GSFC) Sea Ice Concentration Dat...

  2. Simulation of Satellite Water Vapour Lidar Measurements: Performance Assessment under Real Atmospheric Conditions.

    OpenAIRE

    Di Girolamo, Paolo; Behrendt, Andreas; Kiemle, Christoph; Wulfmeyer, Volker; Bauer, Heinz; Summa, Donato; Dörnbrack, Andreas; Ehret, Gerhard

    2008-01-01

    A lidar simulator has been applied to assess the performances of a satellite water vapour differential absorption lidar (DIAL) system. Measurements performed by the airborne Deutsches Zentrum für Luft- und Raumfahrt (DLR) water vapour DIAL on 15 May 2002 during ESA’s Water Vapour Lidar Experiment (WALEX), in combination with MM5 mesoscale model output, were used to obtain backscatter and water vapour fields with high resolution and accuracy. These data and model output serve as input for the ...

  3. Computer-aided evaluation of the railway track geometry on the basis of satellite measurements

    Science.gov (United States)

    Specht, Cezary; Koc, Władysław; Chrostowski, Piotr

    2016-05-01

    In recent years, all over the world there has been a period of intensive development of GNSS (Global Navigation Satellite Systems) measurement techniques and their extension for the purpose of their applications in the field of surveying and navigation. Moreover, in many countries a rising trend in the development of rail transportation systems has been noticed. In this paper, a method of railway track geometry assessment based on mobile satellite measurements is presented. The paper shows the implementation effects of satellite surveying railway geometry. The investigation process described in the paper is divided on two phases. The first phase is the GNSS mobile surveying and the analysis obtained data. The second phase is the analysis of the track geometry using the flat coordinates from the surveying. The visualization of the measured route, separation and quality assessment of the uniform geometric elements (straight sections, arcs), identification of the track polygon (main directions and intersection angles) are discussed and illustrated by the calculation example within the article.

  4. Image-processing techniques in precisely measuring positions of Saturn and its satellites

    Institute of Scientific and Technical Information of China (English)

    PENG; Qingyu; (彭青玉)

    2003-01-01

    After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn's position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus-- two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Observatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.

  5. Towards validation of ammonia (NH3 measurements from the IASI satellite

    Directory of Open Access Journals (Sweden)

    M. Van Damme

    2014-12-01

    Full Text Available Limited availability of ammonia (NH3 observations is currently a barrier for effective monitoring of the nitrogen cycle. It prevents a full understanding of the atmospheric processes in which this trace gas is involved and therefore impedes determining its related budgets. Since the end of 2007, the Infrared Atmospheric Sounding Interferometer (IASI satellite has been observing NH3 from space at a high spatiotemporal resolution. This valuable data set, already used by models, still needs validation. We present here a first attempt to validate IASI-NH3 measurements using existing independent ground-based and airborne data sets. The yearly distributions reveal similar patterns between ground-based and space-borne observations and highlight the scarcity of local NH3 measurements as well as their spatial heterogeneity and lack of representativity. By comparison with monthly resolved data sets in Europe, China and Africa, we show that IASI-NH3 observations are in fair agreement but that they are characterized by a smaller variation in concentrations. The use of hourly and airborne data sets to compare with IASI individual observations allows to investigate the impact of averaging as well as the representativity of independent observations for the satellite footprint. The importance of considering the latter and the added value of densely located airborne measurements at various altitudes to validate IASI-NH3 columns are discussed. Perspectives and guidelines for future validation work on NH3 satellite observations are presented.

  6. Joint Polar Satellite System (JPSS) Common Ground System (CGS) Current Technical Performance Measures

    Science.gov (United States)

    Cochran, S.; Panas, M.; Jamilkowski, M. L.; Miller, S. W.

    2015-12-01

    ABSTRACT The National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation civilian weather and environmental satellite system: the Joint Polar Satellite System (JPSS). The Joint Polar Satellite System will replace the afternoon orbit component and ground processing system of the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA. The JPSS satellites will carry a suite of sensors designed to collect meteorological, oceanographic, climatological and geophysical observations of the Earth. The ground processing system for JPSS is known as the JPSS Common Ground System (JPSS CGS). Developed and maintained by Raytheon Intelligence, Information and Services (IIS), the CGS is a multi-mission enterprise system serving NOAA, NASA and their national and international partners. The CGS has demonstrated its scalability and flexibility to incorporate multiple missions efficiently and with minimal cost, schedule and risk, while strengthening global partnerships in weather and environmental monitoring. The CGS architecture is being upgraded to Block 2.0 in 2015 to "operationalize" S-NPP, leverage lessons learned to date in multi-mission support, take advantage of more reliable and efficient technologies, and satisfy new requirements and constraints in the continually evolving budgetary environment. To ensure the CGS meets these needs, we have developed 49 Technical Performance Measures (TPMs) across 10 categories, such as data latency, operational availability and scalability. This paper will provide an overview of the CGS Block 2.0 architecture, with particular focus on the 10 TPM categories listed above. We will provide updates on how we ensure the deployed architecture meets these TPMs to satisfy our multi-mission objectives with the deployment of Block 2.0.

  7. High Precision Vertical Deflection Over China Marginal Sea and Global Sea Derived from Multi-Satellite Altimeter%联合多种测高数据确定中国边缘海及全球海域的垂线偏差

    Institute of Scientific and Technical Information of China (English)

    王虎彪; 王勇; 陆洋

    2008-01-01

    On the basis of gravity field model (EIGEN_CG01C),together with multi-altimeter data,the improved deflection of the vertical gridded in 2'×2' in China marginal sea and gridded in 5'×5' in the global sea was determined by using the weighted method of along-track least squares,and the accuracy is better than 1.2" in China marginal sea.As for the qual-ity of the deflection of the vertical,it meets the challenge for the gravity field of high resolution and accuracy.It shows that,compared with the shipboard gravimetry in the sea,the accuracy of the gravity anomalies computed with the marine deflec-tion of the vertical by inverse Vening-Meinesz formula is 7.75 m·s-2.

  8. Experiences on Altimeter Calibration at Ibiza Island and Cape of Begur (Spain)

    Science.gov (United States)

    Martinez Benjamin, J. J.; Martinez Harcia, M.; Ortiz Castello, M. A.; Talaya, J.; Baron, A.; Rodriguez Velasco, G.; Martín Davila, J.; Garate, J.; Bonnefond, P.; Garcia, C.

    2006-07-01

    Three preliminary camp aigns for TOPEX /POSEIDON (T/P) wer e made in March 1999 and July 2000 and for JASON-1 in August 2002, in the NW Mediterran ean Sea at th e Begur Cape area. Dir ect abso lute altimeter calibration , and mapping of the sea surface, w ere made in these camp aigns from dir ect overflights using GPS buoys with a toroidal design performed at the I CC based in the orig inal design of the Univ ersity of Colorado at Boulder and a estimation of the TOPEX A lt- B bias w as made. A Spanish JASON-1 geoid gradien t campaign with Fench support has been made in June 2003 at the Ibiza island in the NW Mediterr anean Sea. Th e main objectiv e has b een to map w ith a new d esign ed, builded and calibrated GPS catamar an, the lo cal geoid gradien t in three ar eas around Ibiza island under the ascending (187) and descending (248) Jason-1ground tracks. The catamaran equ ipped with two GPS antennas to perform continuous sea lev el measur ements was towed by the Patro l Dev a from th e Span ish N avy. Five GPS reference stations were dep loyed on Ibiza island: one in Portinatx, two in San Anton io and two in Ibiza. The marin e geo id has been used to relate the coastal tide gauge data from Ibiza and San An tonio h arbours to off- shore altimetric data. In th e framework of the campaign, the levelling of the Ibiza and San Anton io tide gauges to the r espective GPS mark ers w as p erformed. We present synth esis of the resu lts obtained from Topex/Poseidon and th e first r esults on Jason-1 altimeter calibration using the direct measurements from GPS buoys and the derived marin e geoid. Th e Ibiza results agree relativ ely w ell with resu lts ob tained at Corsica, Harvest and Bass Strait calibration permanen t sites. Moreov er, the geod etic activities (e.g., GPS, levelling) has p ermitted to build a very accurate (few mm) local n etwork link ed to th e European one, w ith a reference frame compatible with th e satellite altimetry missions (ITRF2000). The GPS

  9. Gravimetric geodesy and sea surface topography studies by means of satellite-to-satellite tracking and satellite altimetry

    Science.gov (United States)

    Siry, J. W.

    1972-01-01

    A satellite-to-satellite tracking experiment is planned between ATS-F and GEOS-C with a range accuracy of 2-meters and a range rate accuracy of 0.035 centimeters per second for a 10-second integration time. This experiment is planned for 1974. It is anticipated that it will improve the spatial resolution of the satellite geoid by half an order of magnitude to about 6 degrees. Longer integration times should also permit a modest increase in the acceleration resolution. Satellite altimeter data will also be obtained by means of GEOS-C. An overall accuracy of 5-meters in altitude is the goal. The altimeter, per se, is expected to have an instrumental precision of about 2 meters, and an additional capability to observe with a precision of about 0.2 meters for limited periods.

  10. APPLICATION OF VISION METROLOGY TO IN-ORBIT MEASUREMENT OF LARGE REFLECTOR ONBOARD COMMUNICATION SATELLITE FOR NEXT GENERATION MOBILE SATELLITE COMMUNICATION

    Directory of Open Access Journals (Sweden)

    M. Akioka

    2016-06-01

    Full Text Available Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1 Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order

  11. Application of Vision Metrology to In-Orbit Measurement of Large Reflector Onboard Communication Satellite for Next Generation Mobile Satellite Communication

    Science.gov (United States)

    Akioka, M.; Orikasa, T.; Satoh, M.; Miura, A.; Tsuji, H.; Toyoshima, M.; Fujino, Y.

    2016-06-01

    Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1) Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order 2) Trial

  12. Fluxes of energetic protons and electrons measured on board the Oersted satellite

    Directory of Open Access Journals (Sweden)

    J. Cabrera

    2005-11-01

    Full Text Available The Charged Particle Detector (CPD on board the Oersted satellite (649 km perigee, 865 km apogee and 96.48° inclination currently measures energetic protons and electrons. The measured peak fluxes of E>1 MeV electrons are found to confirm the predictions of AE8-MAX, though they occur at a geographical position relatively shifted in the SAA. The fluxes of protons are one order of magnitude higher than the predictions of AP8-MAX in the energy range 20-500 MeV. This huge discrepancy between AP8 and recent measurements in LEO was already noticed and modelled in SAMPEX/PSB97 and TPM-1 models. Nevertheless some other LEO measurements such as PROBA and CORONA-F result in flux values in good agreement with AP8 within a factor 2. The anisotropy of the low-altitude proton flux, combined with measurement performed on board three-axis stabilised satellites, has been suspected to be one possible source of the important discrepancies observed by different missions. In this paper, we evaluate the effect of anisotropy on flux measurements conducted using the CPD instruments. On the basis of the available data, we confirm the inaccuracy of AP8 at LEO and suggest methods to improve the analysis of data in future flux measurements of energetic protons at low altitudes.

  13. Advanced two-way satellite frequency transfer by carrier-phase and carrier-frequency measurements

    Science.gov (United States)

    Fujieda, Miho; Gotoh, Tadahiro; Amagai, Jun

    2016-06-01

    Carrier-phase measurement is one of the ways to improve the measurement resolution of two-way satellite frequency transfer. We introduce two possible methods for carrier-phase measurement: direct carrier-phase detection identified by Two-Way Carrier-Phase (TWCP) and the use of carrier-frequency information identified by Two-Way Carrier Frequency (TWCF). We performed the former using an arbitrary waveform generator and an analog-to-digital sampler and the latter using a conventional modem. The TWCF measurement using the modem had a resolution of 10-13 and the result agreed with that obtained by GPS carrier-phase frequency transfer in a 1500 km baseline. The measurement accuracy may have been limited by the poor frequency resolution of the modem; however, the TWCF measurement was able to improve the stability of conventional two-way satellite frequency transfer. Additionally, we show that the TWCP measurement system has the potential to achieve a frequency stability of 10-17.

  14. A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data

    Science.gov (United States)

    Ricker, Robert; Hendricks, Stefan; Kaleschke, Lars; Tian-Kunze, Xiangshan; King, Jennifer; Haas, Christian

    2017-07-01

    Sea-ice thickness on a global scale is derived from different satellite sensors using independent retrieval methods. Due to the sensor and orbit characteristics, such satellite retrievals differ in spatial and temporal resolution as well as in the sensitivity to certain sea-ice types and thickness ranges. Satellite altimeters, such as CryoSat-2 (CS2), sense the height of the ice surface above the sea level, which can be converted into sea-ice thickness. Relative uncertainties associated with this method are large over thin ice regimes. Another retrieval method is based on the evaluation of surface brightness temperature (TB) in L-band microwave frequencies (1.4 GHz) with a thickness-dependent emission model, as measured by the Soil Moisture and Ocean Salinity (SMOS) satellite. While the radiometer-based method looses sensitivity for thick sea ice (> 1 m), relative uncertainties over thin ice are significantly smaller than for the altimetry-based retrievals. In addition, the SMOS product provides global sea-ice coverage on a daily basis unlike the altimeter data. This study presents the first merged product of complementary weekly Arctic sea-ice thickness data records from the CS2 altimeter and SMOS radiometer. We use two merging approaches: a weighted mean (WM) and an optimal interpolation (OI) scheme. While the weighted mean leaves gaps between CS2 orbits, OI is used to produce weekly Arctic-wide sea-ice thickness fields. The benefit of the data merging is shown by a comparison with airborne electromagnetic (AEM) induction sounding measurements. When compared to airborne thickness data in the Barents Sea, the merged product has a root mean square deviation (RMSD) of about 0.7 m less than the CS2 product and therefore demonstrates the capability to enhance the CS2 product in thin ice regimes. However, in mixed first-year (FYI) and multiyear (MYI) ice regimes as in the Beaufort Sea, the CS2 retrieval shows the lowest bias.

  15. Analysis of the role of urban vegetation in local climate of Budapest using satellite measurements

    Science.gov (United States)

    Pongracz, Rita; Bartholy, Judit; Dezso, Zsuzsanna; Fricke, Cathy

    2016-08-01

    Urban areas significantly modify the natural environment due to the concentrated presence of humans and the associated anthropogenic activities. In order to assess this effect, it is essential to evaluate the relationship between urban and vegetated surface covers. In our study we focused on the Hungarian capital, Budapest, in which about 1.7 million inhabitants are living nowadays. The entire city is divided by the river Danube into the hilly, greener Buda side on the west, and the flat, more densely built-up Pest side on the east. Most of the extended urban vegetation, i.e., forests are located in the western Buda side. The effects of the past changing of these green areas are analyzed using surface temperature data calculated from satellite measurements in the infrared channels, and NDVI (Normalized Difference Vegetation Index) derived from visible and near-infrared satellite measurements. For this purpose, data available from sensor MODIS (Moderate Resolution Imaging Spectroradiometer) of NASA satellites (i.e., Terra and Aqua) are used. First, the climatological effects of forests on the urban heat island intensity are evaluated. Then, we also aim to evaluate the relationship of surface temperature and NDVI in this urban environment with special focus on vegetation-related sections of the city where the vegetation cover either increased or decreased remarkably.

  16. The retrieval of cloud microphysical properties using satellite measurements and an in situ database

    Directory of Open Access Journals (Sweden)

    Christophe Poix

    Full Text Available By combining AVHRR data from the NOAA satellites with information from a database of in situ measurements, large-scale maps can be generated of the microphysical parameters most immediately significant for the modelling of global circulation and climate. From the satellite data, the clouds can be classified into cumuliform, stratiform and cirrus classes and then into further sub-classes by cloud top temperature. At the same time a database of in situ measurements made by research aircraft is classified into the same sub-classes and a statistical analysis is used to derive relationships between the sub-classes and the cloud microphysical properties. These two analyses are then linked to give estimates of the microphysical properties of the satellite observed clouds. Examples are given of the application of this technique to derive maps of the probability of occurrence of precipitating clouds and of precipitating water content derived from a case study within the International Cirrus Experiment (ICE held in 1989 over the North Sea.

  17. Real-time kinematic positioning of LEO satellites using a single-frequency GPS receiver

    CERN Document Server

    Chen, Pei; Sun, Xiucong

    2016-01-01

    Due to their low cost and low power consumption, single-frequency GPS receivers are considered suitable for low-cost space applications such as small satellite missions. Recently, requirements have emerged for real-time accurate orbit determination at sub-meter level in order to carry out onboard geocoding of high-resolution imagery, open-loop operation of altimeters and radio occultation. This study proposes an improved real-time kinematic positioning method for LEO satellites using single-frequency receivers. The C/A code and L1 phase are combined to eliminate ionospheric effects. The epoch-differenced carrier phase measurements are utilized to acquire receiver position changes which are further used to smooth the absolute positions. A kinematic Kalman filter is developed to implement kinematic orbit determination. Actual flight data from China small satellite SJ-9A are used to test the navigation performance. Results show that the proposed method outperforms traditional kinematic positioning method in term...

  18. First results of measurements of extreme ultraviolet radiation onboard a geostationary satellite "ELECTRO-L"

    Science.gov (United States)

    Nusinov, Anatoliy; Kazachevskaya, Tamara; Gonjukh, David

    Measurements of the intensity of EUV emission in the hydrogen Lyman-alpha line were conducted by a broadband photometer VUSS-E onboard geostationary Hydrometeorological satellite "Electro" since March 2011. The solar hydrogen Lyman-alpha line (lambda = 121.6 nm) was monitored. The photomultiplier with LiF window used as a detector insensitive to visible light. Long-wavelength limit of the spectral band sensitivity of the instrument is about 200 nm, so the signal of the device is defined as the flux of solar radiation in the region of 123-200 nm. Its exclusion was carried out by calculation. Since the satellite "Electro" designed for remote sensing of the Earth, its line of sight focused on Earth. Alignment of instrument in the Sun direction was achieved by installing it on the solar panel, periodically moved in the solar direction. Correction of instrument readings, reduced due to the deviation of its axis from the Sun direction, carried out by calculation. Measurements were carried out every second. The first results of the measurements are presented. The difference in absolute calibration Electro-L/VUSS-E is within 5% of corresponding values for measurements TIMED satellite in those days, that is in agreement with laboratory calibrations. It is useful to measure the temperature of the instrument, as its variation on a small interval of time makes change the value of the output signal about 1-2 %. During first year of operation, the sensitivity of the apparatus remained within ± 2% of measured value, significant degradation of sensitivity was not observed. Over time of observation there have been several large flares of X class. The increase of the signal in the ultraviolet range does not exceed a few percent during these flares.

  19. Secular Gravity Gradients in Non-Dynamical Chern-Simons Modified Gravity for Satellite Gradiometry Measurements

    CERN Document Server

    Qiang, Li-E

    2016-01-01

    With continuous advances in related technologies, relativistic gravitational experiments with orbiting gradiometers becomes feasible, which could naturally be incorporated into future satellite gravity missions. Tests of Chern-Simons modified gravity are meaningful since such a modification gives us insights into (possible) parity-violations in gravitation. In this work, we derive, at the post-Newtonian level, the new observables of secular gradients from the non-dynamical Chern-Simons modified gravity, which will greatly improve the constraint on the mass scale $M_{CS}$ that may be drawn from satellite gradiometry measurements. For superconducting gradiometers, a strong bound $M_{CS}\\geq 10^{-7}\\ eV$ could in principle be obtained. For future optical gradiometers based on similar technologies from the LISA PathFinder mission, a even stronger bound $M_{CS}\\geq 10^{-5}\\ eV$ might be expected.

  20. Ionizing radiation fluxes and dose measurements during the Kosmos 1887 satellite flight.

    Science.gov (United States)

    Charvat, J; Spurny, F; Kopecka, B; Votockova, I

    1990-01-01

    The results of dosimetric experiments performed during the flight of Kosmos 1887 biosatellite are presented. Two kinds of measurements were performed on the external surface of the satellite. First, the fluences and spectra of low energy charged particles were established. It was found that most of the particles registered by means of solid state nuclear track detectors are helium nuclei. Tracks of oxygen nuclei and some heavier charged particles were also observed. Thermoluminescent detectors were used to establish absorbed doses in open space on the satellite's surface and behind thin shielding. It was found that these doses were rather high; nevertheless, their decrease with shielding thickness is very rapid. Dosimetric and other consequences of the results obtained are analyzed and discussed.

  1. Absorbed dose measurements on external surface of Kosmos-satellites with glass thermoluminescent detectors.

    Science.gov (United States)

    Akatov YuA; Arkhangelsky, V V; Kovalev, E E; Spurny, F; Votochkova, I

    1989-01-01

    In this paper we present absorbed dose measurements with glass thermoluminescent detectors on external surface of satellites of Kosmos-serie flying in 1983-87. Experiments were performed with thermoluminescent aluminophosphate glasses of thicknesses 0.1, 0.3, 0.4, 0.5, and 1 mm. They were exposed in sets of total thickness between 5 and 20 mm, which were protected against sunlight with thin aluminized foils. In all missions, extremely high absorbed dose values were observed in the first layers of detectors, up to the thickness of 0.2 to 0.5 gcm-2. These experimental results confirm that, during flights at 250 to 400 km, doses on the surface of the satellites are very high, due to the low energy component of the proton and electron radiation.

  2. Distribution and composition of suspended particulate matter in the Atlantic Ocean: Direct measurements and satellite data

    Science.gov (United States)

    Lisitzin, A. P.; Klyuvitkin, A. A.; Burenkov, V. I.; Kravchishina, M. D.; Politova, N. V.; Novigatsky, A. N.; Shevchenko, V. P.; Klyuvitkina, T. S.

    2016-01-01

    The main purpose of this work is to study the real distribution and spatial-temporal variations of suspended particulate matter and its main components in surface waters of the Atlantic Ocean on the basis of direct and satellite measurements for development of new and perfection of available algorithms for converting satellite data. The distribution fields of suspended particulate matter were calculated and plotted for the entire Atlantic Ocean. It is established that its distribution in the open ocean is subordinate to the latitudinal climatic zonality. The areas with maximum concentrations form latitudinal belts corresponding to high-productivity eutrophic and mesotrophic waters of the northern and southern temperate humid belts and with the equatorial humid zone. Phytoplankton, the productivity of which depends primarily on the climatic zonality, is the main producer of suspended particulate matter in the surface water layer.

  3. Quantum-limited measurements of optical signals from a geostationary satellite

    CERN Document Server

    Günthner, Kevin; Elser, Dominique; Stiller, Birgit; Bayraktar, Ömer; Müller, Christian R; Saucke, Karen; Tröndle, Daniel; Heine, Frank; Seel, Stefan; Greulich, Peter; Zech, Herwig; Gütlich, Björn; Richter, Ines; Lutzer, Michael; Philipp-May, Sabine; Meyer, Rolf; Marquardt, Christoph; Leuchs, Gerd

    2016-01-01

    The measurement of quantum signals that traveled through long distances is of fundamental and technical interest. We present quantum-limited coherent measurements of optical signals, sent from a satellite in geostationary Earth orbit to an optical ground station. We bound the excess noise that the quantum states could have acquired after having propagated 38600 km through Earth's gravitational potential as well as its turbulent atmosphere. Our results indicate that quantum communication is feasible in principle in such a scenario, highlighting the possibility of a global quantum key distribution network for secure communication.

  4. Nearshore Bathymetric Change Resolved by Depth Inversions, Sonic Altimeters, and In-Situ Surveys

    Science.gov (United States)

    Brodie, K. L.; Palmsten, M. L.; Hesser, T.; Dickhudt, P.; Ladner, H.; Elgar, S.; Raubenheimer, B.; Penko, A.

    2016-12-01

    Video-based remote sensing of shoaling and breaking surface gravity waves combined with a depth-inversion algorithm, cBathy, may be able to provide bathymetry information with high spatial and temporal resolution in the nearshore (Holman et al., 2013, JGR, Vol 118). Although the accuracy of cBathy has been assessed in low-wave conditions when coincident in-situ surveys are available, it has not been tested for many conditions with significant wave height > 1.5 m. During high wave conditions, the use of linear wave theory in the depth-inversion algorithm may result in estimates of water depth that are too deep. Here, measurements from an in-situ array of sonic altimeters and from frequent watercraft surveys are used to assess the ability of cBathy to estimate the spatio-temporal evolution of the seafloor during a range of wave conditions at a micro-tidal sandy beach in Duck, NC. Observations were collected continuously from 14 October to 01 November 2015 with 8 altimeters in 1.5 to 4 m water depth on 2 cross-shore transects separated by 75 m in the alongshore during waves that ranged from 0.5 to 1.0 m. Nearshore bathymetry was alongshore variable, with a crescentic bar that attached to the shoreline along one transect and was 150 m offshore along the other transect. Sand levels changed by as much as 1 m in some locations. Additional measurements were collected with 3 altimeters on a single cross-shore transect for 6 months, with wave heights from 0.3 to 5.0 m and sand level fluctuations of up to 1 m in a single day. Initial comparisons with surveys show cBathy RMSE and bias are of similar magnitude to prior studies. Although cBathy resolves the large-scale spatial morphology of the sandbar, when Hs > 1.3 m cBathy estimates of the sandbar location are 10 to 50 m onshore of the surveyed location. cBathy uncertainty estimates were a poor representation of actual errors when compared with the surveys. Six-month-long time series of altimeter data will be used to assess c

  5. Improved Forest Biomass and Carbon Estimations Using Texture Measures from WorldView-2 Satellite Data

    Directory of Open Access Journals (Sweden)

    Sandra Eckert

    2012-03-01

    Full Text Available Accurate estimation of aboveground biomass and carbon stock has gained importance in the context of the United Nations Framework Convention on Climate Change (UNFCCC and the Kyoto Protocol. In order to develop improved forest stratum–specific aboveground biomass and carbon estimation models for humid rainforest in northeast Madagascar, this study analyzed texture measures derived from WorldView-2 satellite data. A forest inventory was conducted to develop stratum-specific allometric equations for dry biomass. On this basis, carbon was calculated by applying a conversion factor. After satellite data preprocessing, vegetation indices, principal components, and texture measures were calculated. The strength of their relationships with the stratum-specific plot data was analyzed using Pearson’s correlation. Biomass and carbon estimation models were developed by performing stepwise multiple linear regression. Pearson’s correlation coefficients revealed that (a texture measures correlated more with biomass and carbon than spectral parameters, and (b correlations were stronger for degraded forest than for non-degraded forest. For degraded forest, the texture measures of Correlation, Angular Second Moment, and Contrast, derived from the red band, contributed to the best estimation model, which explained 84% of the variability in the field data (relative RMSE = 6.8%. For non-degraded forest, the vegetation index EVI and the texture measures of Variance, Mean, and Correlation, derived from the newly introduced coastal blue band, both NIR bands, and the red band, contributed to the best model, which explained 81% of the variability in the field data (relative RMSE = 11.8%. These results indicate that estimation of tropical rainforest biomass/carbon, based on very high resolution satellite data, can be improved by (a developing and applying forest stratum–specific models, and (b including textural information in addition to spectral information.

  6. Processing the data of measurements of angular velocity and microaccelerations onboard the Foton-12 satellite

    Science.gov (United States)

    Sazonov, V. V.

    2011-10-01

    The results of reconstruction of uncontrolled rotational motion of the Foton-12 satellite using the measurement data of onboard sensors are presented. This problem has already been solved successfully several years ago. The satellite motion was reconstructed using the data of measuring the Earth's magnetic field. The data of measuring the angular velocity and microaccelerations by the QSAM system were actually not used for this purpose, since these data include a clearly seen additional component whose origin was at that time unclear. This component prevented one from using these data directly for reconstruction of the angular motion. Later it became clear that the additional component was caused by the Earth's magnetic field. Discovery of this fact allowed us to make necessary corrections when processing the QSAM system data and to use them for reconstruction of rotational motion of Foton-12. Below, a modified method of processing the QSAM system data is described together with the results of its application. The main result is obtained by comparing the motion reconstructed from measurements of angular velocity or acceleration with that found by way of processing the measurements of the Earth's magnetic field. Their coincidence turned out to be rather accurate.

  7. Subpixel Accuracy Analysis of Phase Correlation Shift Measurement Methods Applied to Satellite Imagery

    Directory of Open Access Journals (Sweden)

    S.M. Badwai

    2013-01-01

    Full Text Available the key point of super resolution process is the accurate measuring of sub-pixel shift. Any tiny error in measuring such shift leads to an incorrect image focusing. In this paper, methodology of measuring sub-pixel shift using Phase correlation (PC are evaluated using different window functions, then modified version of (PC method using high pass filter (HPF is introduced . Comprehensive analysis and assessment of (PC methods shows that different natural features yield different shift measurements. It is concluded that there is no universal window function for measuring shift; it mainly depends on the features in the satellite images. Even the question of which window is optimal of particular feature is generally remains open. This paper presents the design of a method for obtaining high accuracy sub pixel shift phase correlation using (HPF.The proposed method makes the change in the different locations that lack of edges easy.

  8. Surface radiation at sea validation of satellite-derived data with shipboard measurements

    Directory of Open Access Journals (Sweden)

    Hein Dieter Behr

    2009-03-01

    Full Text Available Quality-controlled and validated radiation products are the basis for their ability to serve the climate and solar energy community. Satellite-derived radiation fluxes are well preferred for this task as they cover the whole research area in time and space. In order to monitor the accuracy of these data, validation with well maintained and calibrated ground based measurements is necessary. Over sea, however, long-term accurate reference data sets from calibrated instruments recording radiation are scarce. Therefore data from research vessels operating at sea are used to perform a reasonable validation. A prerequisite is that the instruments on board are maintained as well as land borne stations. This paper focuses on the comparison of radiation data recorded on board of the German Research Vessel "Meteor" during her 13 months cruise across the Mediterranean and the Black Sea with CM-SAF products using NOAA- and MSG-data (August 2006-August 2007: surface incoming short-wave radiation (SIS and surface downward long-wave radiation (SDL. Measuring radiation fluxes at sea causes inevitable errors, e.g.shadowing of fields of view of the radiometers by parts of the ship. These ship-inherent difficulties are discussed at first. A comparison of pairs of ship-recorded and satellite-derived mean fluxes for the complete measuring period delivers a good agreement: the mean bias deviation (MBD for SIS daily means is −7.6 W/m2 with a median bias of −4 W/m2 and consistently the MBD for monthly means is −7.3 W/m2, for SDL daily means the MBD is 8.1 and 6 W/m2 median bias respectively. The MBD for monthly means is 8.2 W/m2. The variances of the daily means (ship and satellite have the same annual courses for both fluxes. No significant dependence of the bias on the total cloud cover recorded according to WMO (1969 has been found. The results of the comparison between ship-based observations and satellite retrieved surface radiation reveal the good accuracy

  9. Spatial-temporal analysis of sea level changes in China seas and neighboring oceans by merged altimeter data

    Science.gov (United States)

    Xu, Yao; Zhou, Bin; Yu, Zhifeng; Lei, Hui; Sun, Jiamin; Zhu, Xingrui; Liu, Congjin

    2017-01-01

    The knowledge of sea level changes is critical important for social, economic and scientific development in coastal areas. Satellite altimeter makes it possible to observe long term and large scale dynamic changes in the ocean, contiguous shelf seas and coastal zone. In this paper, 1993-2015 altimeter data of Topex/Poseidon and its follow-on missions is used to get a time serious of continuous and homogeneous sea level anomaly gridding product. The sea level rising rate is 0.39 cm/yr in China Seas and the neighboring oceans, 0.37 cm/yr in the Bo and Yellow Sea, 0.29 cm/yr in the East China Sea and 0.40 cm/yr in the South China Sea. The mean sea level and its rising rate are spatial-temporal non-homogeneous. The mean sea level shows opposite characteristics in coastal seas versus open oceans. The Bo and Yellow Sea has the most significant seasonal variability. The results are consistent with in situ data observation by the Nation Ocean Agency of China. The coefficient of variability model is introduced to describe the spatial-temporal variability. Results show that the variability in coastal seas is stronger than that in open oceans, especially the seas off the entrance area of the river, indicating that the validation of altimeter data is less reasonable in these seas.

  10. 20,000 Photons Under the Snow: Subsurface Scattering of Visible Laser Light and the Implications for Laser Altimeters

    Science.gov (United States)

    Greeley, A.; Kurtz, N. T.; Shappirio, M.; Neumann, T.; Cook, W. B.; Markus, T.

    2014-12-01

    Existing visible light laser altimeters such as ATM (Airborne Topographical Mapper) with NASA's Operation IceBridge and NASA's MABEL (Multiple Altimeter Beam Experimental Lidar; a simulator for NASA's ICESat-2 mission) are providing scientists with a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Measuring how these surfaces evolve in the face of a rapidly changing climate requires the utmost attention to detail in the design and calibration of these instruments, as well as understanding the changing optical properties of these surfaces. As single photon counting lidars, MABEL and NASA's ATLAS (Advanced Topographic Laser Altimeter System) on the upcoming ICESat-2 mission provide fundamentally different information compared with waveform lidars such as ATM, or GLAS (Geoscience Laser Altimeter System) on NASA's previous ICESat-1 mission. By recording the travel times of individual photons, more detailed information about the surface, and potentially the subsurface, are available and must be considered in elevation retrievals from the observed photon cloud. Here, we investigate possible sources of uncertainty associated with monochromatic visible light scattering in subsurface snow, which may affect the precision and accuracy of elevation estimates. We also explore the capacity to estimate snow grain size in near surface snow using experimental visible light laser data obtained in laboratory experiments.

  11. Evaluation of cloud base height measurements from ceilometer CL31 and MODIS satellite over Ahmedabad, India

    Directory of Open Access Journals (Sweden)

    S. Sharma

    2015-11-01

    Full Text Available Clouds play a tangible role in the Earth's atmosphere and in particular, the cloud base height (CBH which is linked to cloud type is one of the important characteristic to describe the influence of clouds on the environment. In present study, CBH observations from ceilometer CL31 have been extensively studied during May 2013 to January 2015 over Ahmedabad (23.03° N, 72.54° E, India. A detail comparison has been performed with the use of ground-based CBH measurements from ceilometer CL31 and CBH retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer onboard Aqua and Terra satellite. Some interesting features of cloud dynamics viz. strong downdraft and updraft have been observed over Ahmedabad which revealed different cloud characteristics during monsoon and post-monsoon periods. CBH shows seasonal variation during Indian summer monsoon and post-monsoon period. Results indicate that ceilometer is one of the excellent instruments to precisely detect low and mid-level clouds and MODIS satellite provides accurate retrieval of high-level clouds over this region. The CBH algorithm used for MODIS satellite is also able to capture the low-level clouds.

  12. Spatial variability of the Black Sea surface temperature from high resolution modeling and satellite measurements

    Science.gov (United States)

    Mizyuk, Artem; Senderov, Maxim; Korotaev, Gennady

    2016-04-01

    Large number of numerical ocean models were implemented for the Black Sea basin during last two decades. They reproduce rather similar structure of synoptical variability of the circulation. Since 00-s numerical studies of the mesoscale structure are carried out using high performance computing (HPC). With the growing capacity of computing resources it is now possible to reconstruct the Black Sea currents with spatial resolution of several hundreds meters. However, how realistic these results can be? In the proposed study an attempt is made to understand which spatial scales are reproduced by ocean model in the Black Sea. Simulations are made using parallel version of NEMO (Nucleus for European Modelling of the Ocean). A two regional configurations with spatial resolutions 5 km and 2.5 km are described. Comparison of the SST from simulations with two spatial resolutions shows rather qualitative difference of the spatial structures. Results of high resolution simulation are compared also with satellite observations and observation-based products from Copernicus using spatial correlation and spectral analysis. Spatial scales of correlations functions for simulated and observed SST are rather close and differs much from satellite SST reanalysis. Evolution of spectral density for modelled SST and reanalysis showed agreed time periods of small scales intensification. Using of the spectral analysis for satellite measurements is complicated due to gaps. The research leading to this results has received funding from Russian Science Foundation (project № 15-17-20020)

  13. Estimation of snow cover distribution in Beas basin, Indian Himalaya using satellite data and ground measurements

    Indian Academy of Sciences (India)

    H S Negi; A V Kulkarni; B S Semwal

    2009-10-01

    In the present paper,a methodology has been developed for the mapping of snow cover in Beas basin,Indian Himalaya using AWiFS (IRS-P6)satellite data.The complexities in the mapping of snow cover in the study area are snow under vegetation,contaminated snow and patchy snow. To overcome these problems,field measurements using spectroradiometer were carried out and reflectance/snow indices trend were studied.By evaluation and validation of different topographic correction models,it was observed that,the normalized difference snow index (NDSI)values remain constant with the variations in slope and aspect and thus NDSI can take care of topography effects.Different snow cover mapping methods using snow indices are compared to find the suitable mapping technique.The proposed methodology for snow cover mapping uses the NDSI (estimated using planetary re flectance),NIR band reflectance and forest/vegetation cover information.The satellite estimated snow or non-snow pixel information using proposed methodology was validated with the snow cover information collected at three observatory locations and it was found that the algorithm classify all the sample points correctly,once that pixel is cloud free.The snow cover distribution was estimated using one year (2004 –05)cloud free satellite data and good correlation was observed between increase/decrease areal extent of seasonal snow cover and ground observed fresh snowfall and standing snow data.

  14. Correlating Global Precipitation Measurement satellite data with karst spring hydrographs for rapid catchment delineation

    Science.gov (United States)

    Longenecker, Jake; Bechtel, Timothy; Chen, Zhao; Goldscheider, Nico; Liesch, Tanja; Walter, Robert

    2017-05-01

    To protect karst spring water resources, catchments must be known. We have developed a method for correlating spring hydrographs with newly available, high-resolution, satellite-based Global Precipitation Measurement data to rapidly and remotely locate recharge areas. We verify the method using a synthetic comparison of ground-based rain gage data with the satellite precipitation data set. Application to karst springs is proven by correlating satellite data with hydrographs from well-known springs with published catchments in Europe and North America. Application to an unknown-catchment spring in Pennsylvania suggests distant recharge, requiring a flow path that crosses topographic divides, as well as multiple lithologies, physiographic provinces, and tectonic boundaries. Although surprising, this latter result is consistent with published geologic/geophysical, monitoring well, and stream gage data. We conclude that the method has considerable potential to improve the speed and accuracy of catchment identification and hydrodynamic characterization, with applications to water resource protection and groundwater exploration, among others.

  15. A review of satellite radar altimetry applied to coastal ocean studies

    Science.gov (United States)

    Vignudelli, Stefano

    2016-07-01

    Satellite radar altimetry is today considered a mature technique in open ocean. The data stream from the various satellite missions are routinely used for a number of applications. In the last decade, significant research has been carried out into overcoming the problems to extend the capabilities of radar altimeters to the coastal zone, with the aim to integrate the altimeter-derived measurements of sea level, wind speed and significant wave height into coastal ocean observing systems. More/better (and new) datasets are being produced. Moreover, the advent of new satellite missions, both nadir-viewing (e.g., Sentinel-3) and wide-swath (e.g. SWOT), should globally improve both quantity and quality of coastal altimetry data. In this talk, after a brief review of the challenges in coastal altimetry and description of the new products, we showcase some application examples how the new products can be exploited, and we discuss directions for a global coastal altimetry dataset as an asset for long term monitoring of sea level and sea state in the coastal ocean.

  16. HY-2A satellite altimetric data evaluation in the Arctic ocean

    DEFF Research Database (Denmark)

    Cheng, Yongcun; Andersen, Ole Baltazar

    2014-01-01

    HY-2A (‘HaiYang’ denotes Ocean) was launched in August 2011. It payloads Ku and C bands radar altimeters with repeat cycles of 14 days (for three years) and 168 days. In the present study, we preliminary evaluate the HY-2 satellite altimetric data against SARAL/AltiKa and CryoSat-2 data in the Ar......HY-2A (‘HaiYang’ denotes Ocean) was launched in August 2011. It payloads Ku and C bands radar altimeters with repeat cycles of 14 days (for three years) and 168 days. In the present study, we preliminary evaluate the HY-2 satellite altimetric data against SARAL/AltiKa and CryoSat-2 data...... in the Arctic Ocean. The results demonstrates that the HY-2 data shows higher standard variation and mean sea level than AltiKa and CryoSat-2 data during HY-2 cycle 49 (20130803 and 20130817) with more available sea level measurements than CryoSat-2 satellite altimetry. Moreover, consistent sea level variation...

  17. Exploring the relationship between monitored ground-based and satellite aerosol measurements over the City of Johannesburg

    CSIR Research Space (South Africa)

    Garland, Rebecca M

    2012-09-01

    Full Text Available This project studied the relationship between aerosol optical depth (AOD) from the Multi-angle Imaging SpectroRadiometer (MISR) instrument on the Terra satellite, and ground-based monitored particulate matter (PM) mass concentrations measured...

  18. Online data base of satellite sounder and insitu measurements covering two solar cycles

    Science.gov (United States)

    Bilitza, D.; Reinisch, B.; Benson, R.; Grebowsky, J.; Papitashvili, N.; Huang, X.; Schar, W.; Hills, K.

    Accurate descriptions of the solar cycle variations of ionospheric parameters are an important goal of ionospheric modeling. Reliable predictions of these variations are of essential importance for almost all applications of ionospheric models. Unfortunately there are very few global data sources that cover a solar cycle or more. In an effort to expand the solar cycle coverage of data readily available for ionospheric modeling, we have processed a large number of satellite data sets from the sixties, seventies, and early eighties and have made them online accessible as part of NSSDC's ftp archive (http://nssdcftp.gsfc.nasa.gov/spacecraft data/) and it's ATMOWeb retrieval and plotting system (http://nssdc.gsfc.nasa.gov/atmoweb/). We report about two data restoration efforts supported through NASA's Applied Information Systems Research Program (AISRP). The first project deals with insitu data from a large number of US, Canadian, Japanese and German satellites that measured ionospheric densities and temperatures from 1964 to 1983. The accumulated data base includes data from the BE-B, DME-A, AE-B, Alouette 2, ISIS 1, 2, OGO-6, AEROS A, AE-C, -D, -E, Hinotori, ISS-b and DE-2 satellite missions. The second project involves the production of digital topside sounder ionograms from the ISIS 1 and 2 satellites and their subsequent inversion to produce electron-density profiles. Approximately 340,000 ionograms are available from NSSDC as of July 2002. An automatic topside ionogram scaler with true height algorithm (TOPIST) was developed as part of this project and is now being used to obtain electron density profiles from these ionograms. Providing global coverage over more than two solar cycles the database established by this two projects is a valuable asset for improvements of the International Reference Ionosphere model and for ionospheric research.

  19. Determination of Foton M-2 satellite attitude motion by the data of microacceleration measurements

    Science.gov (United States)

    Beuselinck, T.; van Bavinchove, C.; Sazonov, V. V.; Chebukov, S. Yu.

    2009-12-01

    The results of reconstruction of uncontrolled attitude motion of the Foton M-2 satellite using measurements with the accelerometer TAS-3 are presented. The attitude motion of this satellite has been previously determined by the measurement data of the Earth’s magnetic field and the angular velocity. The TAS-3 data for this purpose are used for the first time. These data contain a well-pronounced additional component which made impossible their direct employment for the reconstruction of the attitude motion and whose origin was unknown several years ago. Later it has become known that the additional component is caused by the influence of the Earth’s magnetic field. The disclosure of this fact allowed us to take into account a necessary correction in processing of TAS-3 data and to use them for the reconstruction of the attitude motion of Foton M-2. Here, a modified method of processing TAS-3 data is described, as well as results of its testing and employing. The testing consisted in the direct comparison of the motion reconstructed by the new method with the motion constructed by the magnetic measurements. The new method allowed us to find the actual motion of Foton M-2 in the period June 9, 2005-June 14, 2005, when no magnetic measurements were carried out.

  20. Global carbon monoxide products from combined AIRS, TES and MLS measurements on A-train satellites

    Directory of Open Access Journals (Sweden)

    J. X. Warner

    2013-06-01

    Full Text Available This study tests a novel methodology to add value to satellite datasets. This methodology, data fusion, is similar to data assimilation, except that the background model-based field is replaced by a satellite dataset, in this case AIRS (Atmospheric Infrared Sounder carbon monoxide (CO measurements. The observational information comes from CO measurements with lower spatial coverage than AIRS, namely, from TES (Tropospheric Emission Spectrometer and MLS (Microwave Limb Sounder. We show that combining these datasets with data fusion uses the higher spectral resolution of TES to extend AIRS CO observational sensitivity to the lower troposphere, a region especially important for air quality studies. We also show that combined CO measurements from AIRS and MLS provide enhanced information in the UTLS (upper troposphere/lower stratosphere region compared to each product individually. The combined AIRS/TES and AIRS/MLS CO products are validated against DACOM (differential absorption mid-IR diode laser spectrometer in situ CO measurements from the INTEX-B (Intercontinental Chemical Transport Experiment: MILAGRO and Pacific phases field campaign and in situ data from HIPPO (HIAPER Pole-to-Pole Observations flights. The data fusion results show improved sensitivities in the lower and upper troposphere (20–30% and above 20%, respectively as compared with AIRS-only retrievals, and improved coverage compared with TES and MLS CO data.

  1. Global Carbon Monoxide Products from Combined AIRS, TES and MLS Measurements on A-Train Satellites

    Science.gov (United States)

    Warner, Juying X.; Yang, R.; Wei, Z.; Carminati, F.; Tangborn, A.; Sun, Z.; Lahoz, W.; Attie, J. L.; El Amraoui, L.; Duncan, B.

    2014-01-01

    This study tests a novel methodology to add value to satellite data sets. This methodology, data fusion, is similar to data assimilation, except that the background modelbased field is replaced by a satellite data set, in this case AIRS (Atmospheric Infrared Sounder) carbon monoxide (CO) measurements. The observational information comes from CO measurements with lower spatial coverage than AIRS, namely, from TES (Tropospheric Emission Spectrometer) and MLS (Microwave Limb Sounder). We show that combining these data sets with data fusion uses the higher spectral resolution of TES to extend AIRS CO observational sensitivity to the lower troposphere, a region especially important for air quality studies. We also show that combined CO measurements from AIRS and MLS provide enhanced information in the UTLS (upper troposphere/lower stratosphere) region compared to each product individually. The combined AIRS-TES and AIRS-MLS CO products are validated against DACOM (differential absorption mid-IR diode laser spectrometer) in situ CO measurements from the INTEX-B (Intercontinental Chemical Transport Experiment: MILAGRO and Pacific phases) field campaign and in situ data from HIPPO (HIAPER Pole-to-Pole Observations) flights. The data fusion results show improved sensitivities in the lower and upper troposphere (20-30% and above 20%, respectively) as compared with AIRS-only version 5 CO retrievals, and improved daily coverage compared with TES and MLS CO data.

  2. Modeling Navigation System Performance of a Satellite-Observing Star Tracker Tightly Integrated with an Inertial Measurement Unit

    Science.gov (United States)

    2015-03-26

    Hancock, R.C. Stirbl, and B. Pain. “ Active pixel sensor (APS) based star tracker ”. Aerospace Conference, 1998 IEEE, volume 1, 119–127 vol.1. 1998...Modeling Navigation System Performance of a Satellite-Observing Star Tracker Tightly Integrated with an Inertial Measurement Unit DISSERTATION Scott...Navigation System Performance of a Satellite-Observing Star Tracker Tightly Integrated with an Inertial Measurement Unit DISSERTATION Presented to the

  3. REKF and RUKF for pico satellite attitude estimation in the presence of measurement faults

    Institute of Scientific and Technical Information of China (English)

    Halil Ersin Söken; Chingiz Hajiyev

    2014-01-01

    When a pico satel ite is under normal operational condi-tions, whether it is extended or unscented, a conventional Kalman filter gives sufficiently good estimation results. However, if the measurements are not reliable because of any kind of malfunc-tions in the estimation system, the Kalman filter gives inaccurate results and diverges by time. This study compares two different robust Kalman filtering algorithms, robust extended Kalman filter (REKF) and robust unscented Kalman filter (RUKF), for the case of measurement malfunctions. In both filters, by the use of de-fined variables named as the measurement noise scale factor, the faulty measurements are taken into the consideration with a smal weight, and the estimations are corrected without affecting the characteristic of the accurate ones. The proposed robust Kalman filters are applied for the attitude estimation process of a pico satel-lite, and the results are compared.

  4. Ensemble Kalman filter assimilation of temperature and altimeter data with bias correction and application to seasonal prediction

    Directory of Open Access Journals (Sweden)

    C. L. Keppenne

    2005-01-01

    Full Text Available To compensate for a poorly known geoid, satellite altimeter data is usually analyzed in terms of anomalies from the time mean record. When such anomalies are assimilated into an ocean model, the bias between the climatologies of the model and data is problematic. An ensemble Kalman filter (EnKF is modified to account for the presence of a forecast-model bias and applied to the assimilation of TOPEX/Poseidon (T/P altimeter data. The online bias correction (OBC algorithm uses the same ensemble of model state vectors to estimate biased-error and unbiased-error covariance matrices. Covariance localization is used but the bias covariances have different localization scales from the unbiased-error covariances, thereby accounting for the fact that the bias in a global ocean model could have much larger spatial scales than the random error.The method is applied to a 27-layer version of the Poseidon global ocean general circulation model with about 30-million state variables. Experiments in which T/P altimeter anomalies are assimilated show that the OBC reduces the RMS observation minus forecast difference for sea-surface height (SSH over a similar EnKF run in which OBC is not used. Independent in situ temperature observations show that the temperature field is also improved. When the T/P data and in situ temperature data are assimilated in the same run and the configuration of the ensemble at the end of the run is used to initialize the ocean component of the GMAO coupled forecast model, seasonal SSH hindcasts made with the coupled model are generally better than those initialized with optimal interpolation of temperature observations without altimeter data. The analysis of the corresponding sea-surface temperature hindcasts is not as conclusive.

  5. Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: comparison with coincident satellite and aircraft measurements

    Directory of Open Access Journals (Sweden)

    J. M. Livingston

    2005-01-01

    Full Text Available During the 2003 SAGE (Stratospheric Aerosol and Gas Experiment III Ozone Loss and Validation Experiment (SOLVE II, the fourteen-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14 was mounted on the NASA DC-8 aircraft and measured spectra of total and aerosol optical depth (TOD and AOD during the sunlit portions of eight science flights. Values of ozone column content above the aircraft have been derived from the AATS-14 measurements by using a linear least squares method that exploits the differential ozone absorption in the seven AATS-14 channels located within the Chappuis band. We compare AATS-14 columnar ozone retrievals with temporally and spatially near-coincident measurements acquired by the SAGE III and the Polar Ozone and Aerosol Measurement (POAM III satellite sensors during four solar occultation events observed by each satellite. RMS differences are 19 DU (7% of the AATS value for AATS-SAGE and 10 DU (3% of the AATS value for AATS-POAM. In these checks of consistency between AATS-14 and SAGE III or POAM III ozone results, the AATS-14 analyses use airmass factors derived from the relative vertical profiles of ozone and aerosol extinction obtained by SAGE III or POAM III. We also compare AATS-14 ozone retrievals for measurements obtained during three DC-8 flights that included extended horizontal transects with total column ozone data acquired by the Total Ozone Mapping Spectrometer (TOMS and the Global Ozone Monitoring Experiment (GOME satellite sensors. To enable these comparisons, the amount of ozone in the column below the aircraft is estimated either by assuming a climatological model or by combining SAGE and/or POAM data with high resolution in-situ ozone measurements acquired by the NASA Langley Research Center chemiluminescent ozone sensor, FASTOZ, during the aircraft vertical profile at the start or end of each flight. Resultant total column ozone values agree with corresponding TOMS and GOME measurements to within 10

  6. Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: comparison with coincident satellite and aircraft measurements

    Directory of Open Access Journals (Sweden)

    J. M. Livingston

    2005-01-01

    Full Text Available During the 2003 SAGE (Stratospheric Aerosol and Gas Experiment III Ozone Loss and Validation Experiment (SOLVE II, the fourteen-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14 was mounted on the NASA DC-8 aircraft and measured spectra of total and aerosol optical depth (TOD and AOD during the sunlit portions of eight science flights. Values of ozone column content above the aircraft have been derived from the AATS-14 measurements by using a linear least squares method that exploits the differential ozone absorption in the seven AATS-14 channels located within the Chappuis band. We compare AATS-14 columnar ozone retrievals with temporally and spatially near-coincident measurements acquired by the SAGE III and the Polar Ozone and Aerosol Measurement (POAM III satellite sensors during four solar occultation events observed by each satellite. RMS differences are 19 DU (6% of the AATS value for AATS-SAGE and 10 DU (3% of the AATS value for AATS-POAM. In these checks of consistency between AATS-14 and SAGE III or POAM III ozone results, the AATS-14 analyses use airmass factors derived from the relative vertical profiles of ozone and aerosol extinction obtained by SAGE III or POAM III.

    We also compare AATS-14 ozone retrievals for measurements obtained during three DC-8 flights that included extended horizontal transects with total column ozone data acquired by the Total Ozone Mapping Spectrometer (TOMS and the Global Ozone Monitoring Experiment (GOME satellite sensors. To enable these comparisons, the amount of ozone in the column below the aircraft is estimated either by assuming a climatological model or by combining SAGE and/or POAM data with high resolution in-situ ozone measurements acquired by the NASA Langley Research Center chemiluminescent ozone sensor, FASTOZ, during the aircraft vertical profile at the start or end of each flight. Resultant total column ozone values agree with corresponding TOMS and GOME measurements to

  7. In-Flight Performance of the Mercury Laser Altimeter Laser Transmitter

    Science.gov (United States)

    Yu, Anthony W.; Sun, Xiaoli; Li, Steven X.; Cavanaugh, John F.; Neumann, Gregory A.

    2014-01-01

    The Mercury Laser Altimeter (MLA) is one of the payload instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which was launched on August 3, 2004. MLA maps Mercury's shape and topographic landforms and other surface characteristics using a diode-pumped solid-state laser transmitter and a silicon avalanche photodiode receiver that measures the round-trip time of individual laser pulses. The laser transmitter has been operating nominally during planetary flyby measurements and in orbit about Mercury since March 2011. In this paper, we review the MLA laser transmitter telemetry data and evaluate the performance of solid-state lasers under extended operation in a space environment.

  8. Spatial and temporal variation of CO over Alberta using measurements from satellite, aircrafts, and ground stations

    Science.gov (United States)

    Marey, H. S.; Hashisho, Z.; Fu, L.; Gille, J.

    2014-12-01

    Alberta is Canada's largest oil producer and its oil sand deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) are examined for the 12 year period from 2002-2013. Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations of forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons, summer and spring. Distinct seasonal patterns of CO at the urban site s (Edmonton and Calgary cities) point to the strong influence of traffic. Meteorological parameters play an important role on the CO spatial distribution at various pressure levels. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values while the poor dispersion in central and south Alberta exacerbates the surface CO pollution. Inter-annual variations of satellite data depict a slightly decreasing trend for both regions while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical

  9. Spatial and temporal variation in CO over Alberta using measurements from satellites, aircraft, and ground stations

    Science.gov (United States)

    Marey, H. S.; Hashisho, Z.; Fu, L.; Gille, J.

    2015-04-01

    Alberta is Canada's largest oil producer, and its oil sands deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO) levels over Alberta. The multispectral product that uses both near-infrared (NIR) and the thermal-infrared (TIR) radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT) is examined for the 12-year period from 2002 to 2013. The Moderate Resolution Imaging Spectroradiometer (MODIS) thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations in forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System) aircraft CO profiles (April 2009-December 2011) are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons: summer and spring. Distinct seasonal patterns of CO at the urban sites (Edmonton and Calgary) point to the strong influence of traffic. Meteorological parameters play an important role in the CO spatial distribution at various pressure levels. Northern Alberta shows a stronger upward lifting motion which leads to larger CO total column values, while the poor dispersion in central and southern Alberta exacerbates the surface CO pollution. Interannual variations in satellite data depict a slightly decreasing trend for both regions, while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO vertical

  10. Monolithic sensors for low frequency motion measurement and control of spacecrafts and satellites

    Science.gov (United States)

    Barone, F.; Giordano, G.; Acernese, F.; Romano, R.

    2016-10-01

    In this paper we describe the characteristics and performances of a monolithic sensor designed for low frequency motion measurement and control of spacecrafts and satellites, whose mechanics is based on the UNISA Folded Pendulum. The latter, developed for ground-based applications, exhibits unique features (compactness, lightness, scalability, low resonance frequency and high quality factor), consequence of the action of the gravitational force on its inertial mass. In this paper we introduce and discuss the general methodology used to extend the application of ground-based folded pendulums to space, also in total absence of gravity, still keeping all their peculiar features and characteristics.

  11. Spatial and temporal variation of CO over Alberta using measurements from satellite, aircrafts, and ground stations

    Directory of Open Access Journals (Sweden)

    H. S. Marey

    2014-12-01

    Full Text Available Alberta is Canada's largest oil producer and its oil sand deposits comprise 30% of the world's oil reserves. The process of bitumen extraction and upgrading releases trace gases and aerosols to the atmosphere. In this study we present satellite-based analysis to explore, for the first time, various contributing factors that affect tropospheric carbon monoxide (CO levels over Alberta. The multispectral product that uses both near-infrared (NIR and the thermal-infrared (TIR radiances for CO retrieval from the Measurements of Pollution in the Troposphere (MOPITT are examined for the 12 year period from 2002–2013. Moderate Resolution Imaging Spectroradiometer (MODIS thermal anomaly product from 2001 to 2013 is employed to investigate the seasonal and temporal variations of forest fires. Additionally, in situ CO measurements at industrial and urban sites are compared to satellite data. Furthermore, the available MOZAIC/IAGOS (Measurement of Ozone, Water Vapor, Carbon Monoxide, Nitrogen Oxide by Airbus In-Service Aircraft/In service Aircraft for Global Observing System aircraft CO profiles (April 2009–December 2011 are used to validate MOPITT CO data. The climatological time curtain plot and spatial maps for CO over northern Alberta indicate the signatures of transported CO for two distinct biomass burning seasons, summer and spring. Distinct seasonal patterns of CO at the urban site s (Edmonton and Calgary cities point to the strong influence of traffic. Meteorological parameters play an important role on the CO spatial distribution at various pressure levels. Northern Alberta shows stronger upward lifting motion which leads to larger CO total column values while the poor dispersion in central and south Alberta exacerbates the surface CO pollution. Inter-annual variations of satellite data depict a slightly decreasing trend for both regions while the decline trend is more evident from ground observations, especially at the urban sites. MOPITT CO

  12. Note: Inter-satellite laser range-rate measurement by using digital phase locked loop.

    Science.gov (United States)

    Liang, Yu-Rong; Duan, Hui-Zong; Xiao, Xin-Long; Wei, Bing-Bing; Yeh, Hsien-Chi

    2015-01-01

    This note presents an improved high-resolution frequency measurement system dedicated for the inter-satellite range-rate monitoring that could be used in the future's gravity recovery mission. We set up a simplified common signal test instead of the three frequencies test. The experimental results show that the dominant noises are the sampling time jitter and the thermal drift of electronic components, which can be reduced by using the pilot-tone correction and passive thermal control. The improved noise level is about 10(-8) Hz/Hz(1/2)@0.01Hz, limited by the signal-to-noise ratio of the sampling circuit.

  13. Nonlinear features of equatorial baroclinic Rossby waves detected in Topex altimeter observations

    Directory of Open Access Journals (Sweden)

    R. E. Glazman

    1996-01-01

    Full Text Available Using a recently proposed technique for statistical analysis of non-gridded satellite altimeter data, regime of long equatorially-trapped baroclinic Rossby waves is studied. One-dimensional spatial and spatiotemporal autocorrelation functions of sea surface height (SSH variations yield a broad spectrum of baroclinic Rossby waves and permit determination of their propagation speed. The 1-d wavenumber spectrum of zonal variations is given by a power-law k-2 on scales from about 103 km to 104 km. We demonstrate that the observed wave regime exhibits features of soliton turbulence developing in the long baroclinic Rossby waves. However, being limited to second statistical moments, the present analysis does not allow us to rule out a possibility of weak wave turbulence.

  14. Subsurface circulation and mesoscale variability in the Algerian subbasin from altimeter-derived eddy trajectories

    Science.gov (United States)

    Escudier, Romain; Mourre, Baptiste; Juza, Mélanie; Tintoré, Joaquín.

    2016-08-01

    Algerian eddies are the strongest and largest propagating mesoscale structures in the Western Mediterranean Sea. They have a large influence on the mean circulation, water masses and biological processes. Over 20 years of satellite altimeter data have been analyzed to characterize the propagation of these eddies using automatic detection methods and cross-correlation analysis. We found that, on average, Algerian eddy trajectories form two subbasin scale anticlockwise gyres that coincide with the two Algerian gyres which were described in the literature as the barotropic circulation in the area. This result suggests that altimetry sea surface observations can provide information on subsurface currents and their variability through the study of the propagation of deep mesoscale eddies in semienclosed seas. The analysis of eddy sea level anomalies along the mean pathways reveals three preferred areas of formation. Eddies are usually formed at a specific time of the year in these areas, with a strong interannual variability over the last 20 years.

  15. Retrieval of Black Carbon Absorption from Proposed Satellite Measurements Over the Ocean Glint

    Science.gov (United States)

    Kaufman, Y. J.; Matins, J. V.; Remer, L. A.; Schoeberl, M. R.; Yamasoe, M. A.; Lau, William K. M. (Technical Monitor)

    2001-01-01

    Haze and air pollution includes many chemicals that together form small particles suspended in the air called aerosols. One of the main ingredients found to affect climate and human health is Black Carbon. Black particles emitted from engines that do not burn the fuel completely, e.g. old trucks. Black carbon absorption of sunlight emerges as one of the key components of man-made forcing of climate. However, global characterization of black carbon emissions, distribution and pathways in which it can affect the amount of solar radiation absorbed by the atmosphere is very uncertain. A new method is proposed to measure sunlight absorption by fine aerosol particles containing black carbon over the ocean glint from a satellite mission designed for this purpose. The satellite will scan the same spot over the ocean in the glint plane and a plane 40 degrees off-glint a minute apart, collecting measurements of the reflected light across the solar spectrum. First the dark ocean off the glint is used to derive aerosol properties. Then the black carbon absorption is derived prop the attenuation of the bright glint by the aerosol layer. Such measurements if realized in a proposed future mission - COBRA are expected to produce global monthly climatology of black carbon absorption with high accuracy (110 to 15%) that can show their effect on climate.

  16. Bathymetric Inversion of South China Sea from Satellite Altimetry Data

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This paper focuses on the study of ocean bathymetric inversion from satellite altimeter data by using FFT technique.In this study,the free-air gravity anomalies over the South China Sea are determined by the satellite altimeter data of GEOSAT,ERS-1,ERS-2 and T/P.And the 2.5′×2.5′ bathymetry model in South China Sea is calculated from the gravity anomalies with the inversion model given.After the analysis of the inversion and the comparison between the results,some conclusions can be drawn.

  17. Formaldehyde (HCHO) column measurements from airborne instruments: Comparison with airborne in-situ measurements, model, and satellites

    Science.gov (United States)

    Kwon, Hyeong-Ahn; Park, Rokjin; Nowlan, Caroline; González Abad, Gonzalo; Chance, Kelly; Janz, Scott

    2017-04-01

    Trace gas measurements from airborne instruments are useful to evaluate and improve a retrieval algorithm developed for the Geostationary Environment Monitoring Spectrometer (GEMS). We used radiances measured from two airborne 2D array sensors, the GeoCAPE Airborne Simulator (GCAS) and the Geostationary Trace gas and Aerosol Sensor Optimization (GeoTASO) for DISCOVER-AQ Texas in 2013 and for KORUS-AQ in 2016 to retrieve formaldehyde (HCHO) columns and to evaluate the GEMS retrieval algorithm. In addition, we used simulated aerosol concentrations constrained by airborne LIDAR observations for AMF calculation to convert slant columns to vertical columns. We compared retrieved HCHO columns with vertical columns obtained from in-situ airborne HCHO measurements. Optical properties and distributions of aerosols are found to be important factors, affecting HCHO retrievals. Finally, additional comparisons of retrieved results with model simulations and low-orbiting satellites provides quantitative information for improving bottom-up emission estimates of volatile organic carbon emissions.

  18. Seasonal variability of cloud optical depth over northwestern China derived from CERES/MODIS satellite measurements

    Institute of Scientific and Technical Information of China (English)

    Yonghang Chen; Hongtao Bai; Jianping Huang; Hua Zhang; Jinming Ge; Xiaodan Guan; Xiaoqin Mao

    2008-01-01

    The seasonal variability of cloud optical depth over northwestern China derived from Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) Edition 1B data from July 2002 to June 2004 is presented. The regions of interest are those with Asia monsoon influence, the Tianshan and Qilian Mountains, and the Taklimakan Desert. The results show that the instantaneous measurements presented here are much higher than the previous results derived from International Satellite Cloud Climatology Project (ISCCP) D2 monthly mean data. Generally the measurements of cloud optical depth are the highest in summer and the lowest in winter, however, Taklimakan Desert has the lowest measurements in autumn. The regional variation is quite significant over northwestern China.

  19. SIDRA instrument for measurements of particle fluxes at satellite altitudes. Laboratory prototype

    Science.gov (United States)

    Dudnik, O. V.; Prieto, M.; Kurbatov, E. V.; Sanchez, S.; Timakova, T. G.; Spassky, A. V.; Dubina, V. N.; Parra, P.

    2013-01-01

    The design concept and first set of results are presented for electronic modules of a laboratory prototype of the small-size satellite instrument SIDRA intended for measurements of charged particle fluxes in outer space. The working prototype consists of a detector assembly based on high-purity silicon and fast scintillation detectors, modules of analogue and digital processing, and a secondary power supply module. The first results are discussed of a Monte-Carlo simulation of the instrument with the use of the GEANT4 toolkit and of measurements of the main parameters of charge-sensitive pre-amplifiers, shapers, and peak detectors. Results of calibration measurements with the use of radioactive sources and beams of accelerated charged particles are presented.

  20. Measurements of UV irradiance within the area of one satellite pixel

    Science.gov (United States)

    Weihs, P.; Blumthaler, M.; Rieder, H. E.; Kreuter, A.; Simic, S.; Laube, W.; Schmalwieser, A. W.; Wagner, J. E.; Tanskanen, A.

    2008-09-01

    A measurement campaign was performed in the region of Vienna and its surroundings from May to July 2007. Within the scope of this campaign erythemal UV was measured at six ground stations within a radius of 30 km. First, the homogeneity of the UV levels within the area of one satellite pixel was studied. Second, the ground UV was compared to ground UV retrieved by the ozone monitoring instrument (OMI) onboard the NASA EOS Aura Spacecraft. During clear-sky conditions the mean bias between erythemal UV measured by the different stations was within the measurement uncertainty of ±5%. Short term fluctuations of UV between the stations were below 3% within a radius of 20 km. For partly cloudy conditions and overcast conditions the discrepancy of instantaneous values between the stations is up to 200% or even higher. If averages of the UV index over longer time periods are compared the difference between the stations decreases strongly. The agreement is better than 20% within a distance of 10 km between the stations for 3 h averages. The comparison with OMI UV showed for clear-sky conditions higher satellite retrieved UV values by, on the average, approximately 15%. The ratio of OMI to ground measured UV lies between 0.9 and 1.5. and strongly depends on the aerosol optical depth. For partly cloudy and overcast conditions the OMI derived surface UV estimates show larger deviation from the ground-based reference data, and even bigger systematic positive bias. Here the ratio OMI to ground data lies between 0.5 and 4.5. The average difference between OMI and ground measurements is +24 to +37% for partly cloudy conditions and more than +50% for overcast conditions.

  1. Measurements of UV irradiance within the area of one satellite pixel

    Directory of Open Access Journals (Sweden)

    P. Weihs

    2008-09-01

    Full Text Available A measurement campaign was performed in the region of Vienna and its surroundings from May to July 2007. Within the scope of this campaign erythemal UV was measured at six ground stations within a radius of 30 km. First, the homogeneity of the UV levels within the area of one satellite pixel was studied. Second, the ground UV was compared to ground UV retrieved by the ozone monitoring instrument (OMI onboard the NASA EOS Aura Spacecraft. During clear-sky conditions the mean bias between erythemal UV measured by the different stations was within the measurement uncertainty of ±5%. Short term fluctuations of UV between the stations were below 3% within a radius of 20 km. For partly cloudy conditions and overcast conditions the discrepancy of instantaneous values between the stations is up to 200% or even higher. If averages of the UV index over longer time periods are compared the difference between the stations decreases strongly. The agreement is better than 20% within a distance of 10 km between the stations for 3 h averages. The comparison with OMI UV showed for clear-sky conditions higher satellite retrieved UV values by, on the average, approximately 15%. The ratio of OMI to ground measured UV lies between 0.9 and 1.5. and strongly depends on the aerosol optical depth. For partly cloudy and overcast conditions the OMI derived surface UV estimates show larger deviation from the ground-based reference data, and even bigger systematic positive bias. Here the ratio OMI to ground data lies between 0.5 and 4.5. The average difference between OMI and ground measurements is +24 to +37% for partly cloudy conditions and more than +50% for overcast conditions.

  2. Feasibility of a Constellation of Miniature Satellites for Performing Measurements of the Magnetic Field of the Earth

    DEFF Research Database (Denmark)

    Thomsen, Michael; Merayo, José M.G.; Brauer, Peter

    2008-01-01

    This paper studies the requirements for a small constellation of satellites to perform measurements of the magnetic field of the Earth and a payload and boom design for such a mission is discussed. After studying communication, power and mass requirements it is found that it is feasible to develop...... a 10 x 10 x 30 cm(3) satellite with a mass of about 2.5 kg, which can fulfill such a mission. We also study the feasibility of controlling a constellation of such small satellites by means of air drag by extracting one or more flaps. It is found that it is indeed possible, but for best performance...

  3. Upper tropospheric water vapour variability over tropical latitudes observed using radiosonde and satellite measurements

    Indian Academy of Sciences (India)

    Ghouse Basha; M Venkat Ratnam; B V Krishna Murthy

    2013-12-01

    The present study deals with using long-term database for upper tropospheric water vapour (UTWV) variability studies over three tropical stations (Gadanki, Singapore and Truk), where different climatic conditions prevail. Over Gadanki (13.5°N, 79.2°E) strong seasonal variation in UTWV is revealed but not over Singapore (1.37°N, 103.98°E) and Truk (7.46°N, 151.85°E) except at 100 hPa. It is examined whether high resolution radiosonde measurements represent well the UTWV by comparing with different satellite based (Atmospheric Infrared Sounder (AIRS), Advanced Microwave Sounding Unit-B (AMSUB) and Microwave Limb Sounder (MLS)) water vapour measurements. Very good comparison in the nature of variations of UTWV is observed between radiosonde data and satellite data, except over Singapore particularly with AIRS and MLS data, on long-term basis. An attempt is also made to examine the source for UTWV. A close relationship is found between UTWV and deep convection over Gadanki indicating that the source for UTWV is convection particularly during the summer monsoon season.

  4. Modeling of solar irradiance using satellite images and direct terrestrial measurements with PV modules

    Science.gov (United States)

    Tyukhov, Igor; Schakhramanyan, Michael; Strebkov, Dmitry; Tikhonov, Anton; Vignola, Frank

    2009-08-01

    A simple, affordable and efficient multifaceted system with technical software programs, "Kosmos 3M", was developed for taking images of the Earth from NOAA satellites and for handling this images and analyzing many geographical and meteorological parameters. Technical software programs have been developed that utilize the "Kosmos 3M" Receiver system. Basic capabilities of the multifaceted "Kosmos 3M" system include: receiving signal from NOAA satellites; digital processing of space images with geographical fixing, superposition of maps of cities and coordinate grid; finding of geographical coordinates at any point of space image; finding of temperature of underlying surface at given points; finding of albedo (reflection coefficient) at any point of space image; finding of upper boundary of clouds (cloudiness); forecasting of dangerous weather phenomena; defining wind fields in cyclones; precipitations forecast; measuring distances between given points; measuring surfaces (areas); and forming of electronic library of images of the Earth. Work is underway to use the "Kosmos 3M" cloudiness images to estimate the incident solar radiation values for evaluating terrestrial solar energy performance in real time. Such kind of system would have a wide variety of uses from the classroom to the field.

  5. Measuring snow cover using satellite imagery during 1973 and 1974 melt season: North Santiam, Boise, and Upper Snake Basins, phase 1. [LANDSAT satellites, imaging techniques

    Science.gov (United States)

    Wiegman, E. J.; Evans, W. E.; Hadfield, R.

    1975-01-01

    Measurements are examined of snow coverage during the snow-melt season in 1973 and 1974 from LANDSAT imagery for the three Columbia River Subbasins. Satellite derived snow cover inventories for the three test basins were obtained as an alternative to inventories performed with the current operational practice of using small aircraft flights over selected snow fields. The accuracy and precision versus cost for several different interactive image analysis procedures was investigated using a display device, the Electronic Satellite Image Analysis Console. Single-band radiance thresholding was the principal technique employed in the snow detection, although this technique was supplemented by an editing procedure involving reference to hand-generated elevation contours. For each data and view measured, a binary thematic map or "mask" depicting the snow cover was generated by a combination of objective and subjective procedures. Photographs of data analysis equipment (displays) are shown.

  6. Global Fine Particulate Matter Concentrations and Trends Inferred from Satellite Observations, Modeling, and Ground-Based Measurements

    Science.gov (United States)

    Martin, Randall; van Donkelaar, Aaron; Boys, Brian; Philip, Sajeev; Lee, Colin; Snider, Graydon; Weagle, Crystal

    2014-05-01

    Outdoor fine particulate matter (PM2.5) is a leading environmentally-related cause of premature mortality worldwide. However, ground-level PM2.5 monitors remain sparse in many regions of the world. Satellite remote sensing from MODIS, MISR, and SeaWiFS yields a powerful global data source to address this issue. Global modeling (GEOS-Chem) plays a critical role in relating these observations to ground-level concentrations. The resultant satellite-based estimates of PM2.5 indicate dramatic variation around the world, with implications for global public health. A new ground-based aerosol network (SPARTAN) offers valuable measurements to understand the relationship between satellite observations of aerosol optical depth and ground-level PM2.5 concentrations. This talk will highlight recent advances in combining satellite remote sensing, global modeling, and ground-based measurements to improve understanding of global population exposure to outdoor fine particulate matter.

  7. Integrated analysis of PALSAR/Radarsat-1 InSAR and ENVISAT altimeter data for mapping of absolute water level changes in Louisiana wetlands

    Science.gov (United States)

    Kim, J.-W.; Lu, Zhiming; Lee, H.; Shum, C.K.; Swarzenski, C.M.; Doyle, T.W.; Baek, S.-H.

    2009-01-01

    Interferometric Synthetic Aperture Radar (InSAR) has been used to detect relative water level changes in wetlands. We developed an innovative method to integrate InSAR and satellite radar altimetry for measuring absolute or geocentric water level changes and applied the methodology to remote areas of swamp forest in coastal Louisiana. Coherence analysis of InSAR pairs suggested that the HH polarization is preferred for this type of observation, and polarimetric analysis can help to identify double-bounce backscattering areas in the wetland. ENVISAT radar altimeter-measured 18-Hz (along-track sampling of 417 m) water level data processed with regional stackfile method have been used to provide vertical references for water bodies separated by levees. The high-resolution (~ 40 m) relative water changes measured from ALOS PALSAR L-band and Radarsat-1 C-band InSAR are then integrated with ENVISAT radar altimetry to obtain absolute water level. The resulting water level time series were validated with in situ gauge observations within the swamp forest. We anticipate that this new technique will allow retrospective reconstruction and concurrent monitoring of water conditions and flow dynamics in wetlands, especially those lacking gauge networks. ?? 2009 Elsevier Inc.

  8. A do-it-yourself altimeter for trees

    NARCIS (Netherlands)

    Geesink, R.

    1982-01-01

    Commercially available tree altimeters are expensive and heavy, and my personal experience with these instruments is thus minimal. During my last expedition I only used it now and then in the base camp to correct my ’feeling for estimation’. I have little doubt that colleagues will recognize these f

  9. The Importance of Altimeter and Scatterometer Data for Ocean Prediction,

    Science.gov (United States)

    1984-01-01

    of water vapour , wind speed and wave height. Nature, 294, 529-532. Cheney, R. E. and J. G. Marsh, 1981: SEASAT altimeter observations of dynamic...E. and J. D. Thompson, 1980: A numerical study of Loop Current intrusions and eddy shedding. J. Phys. Oceanogr., 10, 1611-1651. ’Hurlburt, H. E. and J

  10. Satellite radar altimetry for monitoring small river and lakes in Indonesia

    Directory of Open Access Journals (Sweden)

    Y. B. Sulistioadi

    2014-03-01

    Full Text Available Remote sensing and satellite geodetic observations are capable for hydrologic monitoring of freshwater resources. For the case of satellite radar altimetry, limited temporal resolutions (e.g., satellite revisit period prohibit the use of this method for a short ( To address this scientific challenge, this study tries to monitor small (40–200 m width and medium-sized (200–800 m width rivers and lakes using satellite altimetry through identification and choice of the over-water radar waveforms corresponding to the appropriately waveform-retracked water level. This study addresses the humid tropics of Southeast Asia, specifically in Indonesia, where similar studies do not yet exist and makes use Level 2 radar altimeter measurements generated by European Space Agency's (ESA's Envisat (Environmental Satellite mission. This experiment proves that satellite altimetry provides a good alternative, or the only means in some regions, to measure the water level of medium-sized river (200–800 m width and small lake (extent 2 in Southeast Asia humid tropic with reasonable accuracy. In addition, the procedure to choose retracked Envisat altimetry water level heights via identification or selection of standard waveform shapes for inland water is recommended and should be a standard measure especially over small rivers and lakes. This study also found that Ice-1 is not necessarily the best retracker as reported by previous studies, among the four standard waveform retracking algorithms for Envisat radar altimetry observing inland water bodies.

  11. Direct measurements of laser light aberration from the ARTEMIS geostationary satellite through thin clouds

    CERN Document Server

    Kuzkov, Volodymyr; Sodnik, Zoran

    2015-01-01

    A precise ground based telescope system was developed for laser communication experiments with the geostationary satellite ARTEMIS of ESA. Precise tracking of the satellite was realized by using time resolved coordinates of the satellite. During the experiments, the time propagation of laser signal from the satellite and the point-ahead angle for the laser beam were calculated. Some laser experiments though thin clouds were performed. A splitting of some images of the laser beam from the satellite along declination and right ascension coordinates of telescope could be observed through thin clouds. The splitting along the declination coordinate may be interpreted as refraction in the atmosphere. The splitting along the right ascension coordinate is equivalent to the calculated point-ahead angle for the satellite. We find out that a small part of laser beam was observed ahead of the velocity vector in the point where the satellite would be after the laser light from the satellite reaches the telescope. These re...

  12. Earth's gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

    Science.gov (United States)

    Guo, X.; Ditmar, P.; Zhao, Q.; Klees, R.; Farahani, H. H.

    2017-09-01

    GPS data collected by satellite gravity missions can be used for extracting the long-wavelength part of the Earth's gravity field. We propose a new data processing method which makes use of the `average acceleration' approach to gravity field modelling. In this method, satellite accelerations are directly derived from GPS carrier phase measurements with an epoch-differenced scheme. As a result, no ambiguity solutions are needed and the systematic errors that do not change much from epoch to epoch are largely eliminated. The GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission are used to demonstrate the added value of the proposed method. An analysis of the residual accelerations shows that accelerations derived in this way are more precise, with noise being reduced by about 20 and 5% at the cross-track component and the other two components, respectively, as compared to those based on kinematic orbits. The accelerations obtained in this way allow the recovery of the gravity field to a slightly higher maximum degree compared to the solution based on kinematic orbits. Furthermore, the gravity field solution has an overall better performance. Errors in spherical harmonic coefficients are smaller, especially at low degrees. The cumulative geoid height error is reduced by about 15 and 5% up to degree 50 and 150, respectively. An analysis in the spatial domain shows that large errors along the geomagnetic equator, which are caused by a high electron density coupled with large short-term variations, are substantially reduced. Finally, the new method allows for a better observation of mass transport signals. In particular, sufficiently realistic signatures of regional mass anomalies in North America and south-west Africa are obtained.

  13. Validation of NH3 satellite observations by ground-based FTIR measurements

    Science.gov (United States)

    Dammers, Enrico; Palm, Mathias; Van Damme, Martin; Shephard, Mark; Cady-Pereira, Karen; Capps, Shannon; Clarisse, Lieven; Coheur, Pierre; Erisman, Jan Willem

    2016-04-01

    Global emissions of reactive nitrogen have been increasing to an unprecedented level due to human activities and are estimated to be a factor four larger than pre-industrial levels. Concentration levels of NOx are declining, but ammonia (NH3) levels are increasing around the globe. While NH3 at its current concentrations poses significant threats to the environment and human health, relatively little is known about the total budget and global distribution. Surface observations are sparse and mainly available for north-western Europe, the United States and China and are limited by the high costs and poor temporal and spatial resolution. Since the lifetime of atmospheric NH3 is short, on the order of hours to a few days, due to efficient deposition and fast conversion to particulate matter, the existing surface measurements are not sufficient to estimate global concentrations. Advanced space-based IR-sounders such as the Tropospheric Emission Spectrometer (TES), the Infrared Atmospheric Sounding Interferometer (IASI), and the Cross-track Infrared Sounder (CrIS) enable global observations of atmospheric NH3 that help overcome some of the limitations of surface observations. However, the satellite NH3 retrievals are complex requiring extensive validation. Presently there have only been a few dedicated satellite NH3 validation campaigns performed with limited spatial, vertical or temporal coverage. Recently a retrieval methodology was developed for ground-based Fourier Transform Infrared Spectroscopy (FTIR) instruments to obtain vertical concentration profiles of NH3. Here we show the applicability of retrieved columns from nine globally distributed stations with a range of NH3 pollution levels to validate satellite NH3 products.

  14. The contribution of satellite SAR-derived displacement measurements in landslide risk management practices

    Science.gov (United States)

    Raspini, Federico; Bardi, Federica; Bianchini, Silvia; Ciampalini, Andrea; Del Ventisette, Chiara; Farina, Paolo; Ferrigno, Federica; Solari, Lorenzo; Casagli, Nicola

    2017-04-01

    Landslides are common phenomena that occur worldwide and are a main cause of loss of life and damage to property. The hazards associated with landslides are a challenging concern in many countries, including Italy. With 13% of the territory prone to landslides, Italy is one of the European countries with the highest landslide hazard, and on a worldwide scale, it is second only to Japan among the technologically advanced countries. Over the last 15 years, an increasing number of applications have aimed to demonstrate the applicability of images captured by space-borne Synthetic Aperture Radar (SAR) sensors in slope instability investigations. InSAR (SAR Interferometry) is currently one of the most exploited techniques for the assessment of ground displacements, and it is becoming a consolidated tool for Civil Protection institutions in addressing landslide risk. We present a subset of the results obtained in Italy within the framework of SAR-based programmes and applications intended to test the potential application of C- and X-band satellite interferometry during different Civil Protection activities (namely, prevention, prevision, emergency response and post-emergency phases) performed to manage landslide risk. In all phases, different benefits can be derived from the use of SAR-based measurements, which were demonstrated to be effective in the field of landslide analysis. Analysis of satellite-SAR data is demonstrated to play a major role in the investigation of landslide-related events at different stages, including detection, mapping, monitoring, characterization and prediction. Interferometric approaches are widely consolidated for analysis of slow-moving slope deformations in a variety of environments, and exploitation of the amplitude data in SAR images is a somewhat natural complement for rapid-moving landslides. In addition, we discuss the limitations that still exist and must be overcome in the coming years to manage the transition of satellite SAR

  15. Earth's gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

    Science.gov (United States)

    Guo, X.; Ditmar, P.; Zhao, Q.; Klees, R.; Farahani, H. H.

    2017-02-01

    GPS data collected by satellite gravity missions can be used for extracting the long-wavelength part of the Earth's gravity field. We propose a new data processing method which makes use of the `average acceleration' approach to gravity field modelling. In this method, satellite accelerations are directly derived from GPS carrier phase measurements with an epoch-differenced scheme. As a result, no ambiguity solutions are needed and the systematic errors that do not change much from epoch to epoch are largely eliminated. The GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission are used to demonstrate the added value of the proposed method. An analysis of the residual accelerations shows that accelerations derived in this way are more precise, with noise being reduced by about 20 and 5% at the cross-track component and the other two components, respectively, as compared to those based on kinematic orbits. The accelerations obtained in this way allow the recovery of the gravity field to a slightly higher maximum degree compared to the solution based on kinematic orbits. Furthermore, the gravity field solution has an overall better performance. Errors in spherical harmonic coefficients are smaller, especially at low degrees. The cumulative geoid height error is reduced by about 15 and 5% up to degree 50 and 150, respectively. An analysis in the spatial domain shows that large errors along the geomagnetic equator, which are caused by a high electron density coupled with large short-term variations, are substantially reduced. Finally, the new method allows for a better observation of mass transport signals. In particular, sufficiently realistic signatures of regional mass anomalies in North America and south-west Africa are obtained.

  16. Comprehensive Comparisons of Satellite Data, Signals, and Measurements between the BeiDou Navigation Satellite System and the Global Positioning System

    Directory of Open Access Journals (Sweden)

    Shau-Shiun Jan

    2016-05-01

    Full Text Available The Chinese BeiDou navigation satellite system (BDS aims to provide global positioning service by 2020. The combined use of BDS and Global Positioning System (GPS is proposed to provide navigation service with more stringent requirements. Actual satellite data, signals and measurements were collected for more than one month to analyze the positioning service qualities from both BDS and GPS. In addition to the conversions of coordinate and timing system, five data quality analysis (DQA methods, three signal quality analysis (SQA methods, and four measurement quality analysis (MQA methods are proposed in this paper to improve the integrated positioning performance of BDS and GPS. As shown in the experiment results, issues related to BDS and GPS are resolved by the above proposed quality analysis methods. Thus, the anomalies in satellite data, signals and measurements can be detected by following the suggested resolutions to enhance the positioning performance of the combined use of BDS and GPS in the Asia Pacific region.

  17. Sixth generation lithospheric magnetic field model, MF6, from CHAMP satellite magnetic measurements

    Science.gov (United States)

    Maus, S.; Fan, Y.; Manoj, C.; Rother, M.; Rauberg, J.; Stolle, C.; Luhr, H.

    2007-12-01

    The CHAMP satellite continues to provide highly accurate magnetic field measurements with decreasing orbital altitudes (<350km) at solar minimum conditions. A promising new CHAMP data product has become available, which provides the total field with one order of magnitude smaller noise amplitudes. The product is inferred from suitably merged Fluxgate and Overhauser magnetometer data. While the low-noise Fluxgate measurements are used in the short-period range (<900sec, or <6000km wavelength), we take advantage of the high stability provided by the Overhauser for the longer periods. The new data set is used for generating an improved lithospheric magnetic field model (MF6). Although MF6 is still in production at the time of writing this abstract, we anticipate significant benefits in terms of resolving small- scale low-amplitude crustal features from the new data. Further improvements include a new correction for steady ocean circulation and an expansion to higher spherical harmonic degrees of the model.

  18. Night sky brightness at sites from DMSP-OLS satellite measurements

    CERN Document Server

    Cinzano, P

    2004-01-01

    We apply the sky brightness modelling technique introduced and developed by Roy Garstang to high-resolution DMSP-OLS satellite measurements of upward artificial light flux and to GTOPO30 digital elevation data in order to predict the brightness distribution of the night sky at a given site in the primary astronomical photometric bands for a range of atmospheric aerosol contents. This method, based on global data and accounting for elevation, Earth curvature and mountain screening, allows the evaluation of sky glow conditions over the entire sky for any site in the World, to evaluate its evolution, to disentangle the contribution of individual sources in the surrounding territory, and to identify main contributing sources. Sky brightness, naked eye stellar visibility and telescope limiting magnitude are produced as 3-dimensional arrays whose axes are the position on the sky and the atmospheric clarity. We compared our results to available measurements.

  19. Measurements of Ocean Spectral Irradiance for Correlation with Satellite Remote Sensing

    Science.gov (United States)

    1980-05-01

    PRT "E02="YR2; , +R9R15+R25;1+R9 36; SPCF R6+R26F PRT LOG f1E6R6)l- 7’I 22:1 37-o PRT "RA I) SI G ~-R:3R10R21+R3;R4RI IF R’?0OPRT 0; 8: 0R22+R4...Listings . ......... C-I APPENDIX D. Log Sheets ................ ............... D-1 (1) Daily Log (2) Data Printout Supplement APPENDIX E. XBT Trace...taken. --q a Estimated from XBT log ; between stations 17 and 18. X Measurement made or action taken. 0 No measurement or action. Table 2-1. Satellite

  20. SIMULATION OF THE Ku-BAND RADAR ALTIMETER SEA ICE EFFECTIVE SCATTERING SURFACE

    DEFF Research Database (Denmark)

    Tonboe, Rasmus; Andersen, Søren; Pedersen, Leif Toudal

    2006-01-01

    A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model...... is initialised with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73ºW; 85ºN). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard and ice thickness estimation....

  1. GFO and JASON Altimeter Engineering Assessment Report. Update: GFO-Acceptance to End of Mission on October 22, 2008, JASON-Acceptance to September 29, 2008

    Science.gov (United States)

    Conger, A. M.; Hancock, D. W., III; Hayne, G. S.; Brooks, R. L.

    2009-01-01

    The purpose of this document is to present and document GEOSAT Follow-On (GFO) performance analyses and results. This is the ninth Assessment Report since the initial report and is our final one. This report extends the performance assessment since acceptance on November 29, 2000 to the end of mission (EOM) on October 22, 2008. Since launch, February 10, 1998 to the EOM, we performed a variety of GFO performance studies; Appendix A provides an accumulative index of those studies. We began the inclusion of analyses of the JASON altimeter after the end of the Topographic Experiment (TOPEX) mission. Prior to this, JASON and TOPEX were compared during our assessment of the TOPEX altimeter. With the end of the TOPEX mission, we developed methods to report on JASON as it related to GFO. It should be noted the GFO altimeter, after operating for over 7 years, was power cycled off to on and on to off approximately 14 times a day for over 18 months in space with no failure. The GFO altimeter proved to be a remarkable instrument providing stable ocean surface measurements for nearly eight years. This report completes our GFO altimeter performance assessment.

  2. An Autonomous System to Take Angular Thermal-Infrared Measurements for Validating Satellite Products

    Directory of Open Access Journals (Sweden)

    Raquel Niclòs

    2015-11-01

    Full Text Available An autonomous system for field land surface temperature (LST measurements taken at different observation angles was developed to be deployed easily at any conventional meteorological tower station. The system permits ground-truth data to be acquired on a continuous basis, and angularly scans land and sky hemispheres with a single thermal-infrared (TIR radiometer. This paper describes the autonomous angular system and the methodology to assess ground-truth LST and relative-to-nadir emissivity data from system measurements. Ground-truth LSTs were used to validate satellite-retrieved LST products at two experimental sites (rice crop and shrubland areas. The relative-to-nadir emissivity values were used to analyze the anisotropy of surface emissive properties over thermally-homogeneous covers. The EOS-MODIS MOD11_L2/MYD11_L2 LST product was evaluated and shown to work within expected uncertainties (<2.0 K when tested against the system data. A slight underestimation of around −0.15 K was observed, which became greater for the off-nadir observation angles at the shrubland site. The system took angular measurements for the different seasonal homogeneous covers at the rice crop site. These measurements showed emissivity angular anisotropies, which were in good agreement with previously published data. The dual-view ENVISAT-AATSR data reproduced them, and revealed that the system data collected for thermally-homogeneous surfaces could be used to test future satellite TIR sensors with multi-angular or bi-angular capabilities, like the forthcoming SLSTR on board Copernicus Sentinel-3A.

  3. Observation operator for the assimilation of aerosol type resolving satellite measurements into a chemical transport model

    Directory of Open Access Journals (Sweden)

    M. Schroedter-Homscheidt

    2010-11-01

    Full Text Available Modelling of aerosol particles with chemical transport models is still based mainly on static emission databases while episodic emissions cannot be treated sufficiently. To overcome this situation, a coupling of chemical mass concentration modelling with satellite-based measurements relying on physical and optical principles has been developed. This study deals with the observation operator for a component-wise assimilation of satellite measurements. It treats aerosol particles classified into water soluble, water insoluble, soot, sea salt and mineral dust containing aerosol particles in the atmospheric boundary layer as separately assimilated aerosol components. It builds on a mapping of aerosol classes used both in observation and model space taking their optical and chemical properties into account. Refractive indices for primary organic carbon particles, anthropogenic particles, and secondary organic species have been defined based on a literature review. Together with a treatment of different size distributions in observations and model state, this allows transforming the background from mass concentrations into aerosol optical depths. A two-dimensional, variational assimilation is applied for component-wise aerosol optical depths. Error covariance matrices are defined based on a validation against AERONET sun photometer measurements. Analysis fields are assessed threefold: (1 through validation against AERONET especially in Saharan dust outbreak situations, (2 through comparison with the British Black Smoke and Sulphur Dioxide Network for soot-containing particles, and (3 through comparison with measurements of the water soluble components SO4, NH4, and NO3 conducted by the EMEP (European Monitoring and Evaluation Programme network. Separately, for the water soluble, the soot and the mineral dust aerosol components a bias reduction and subsequent a root mean square error reduction is observed in the

  4. CLAIRE: a Canadian Small Satellite Mission for Measurement of Greenhouse Gases

    Science.gov (United States)

    Sloan, James; Grant, Cordell; Germain, Stephane; Durak, Berke; McKeever, Jason; Latendresse, Vincent

    2016-07-01

    CLAIRE, a Canadian mission operated by GHGSat Inc. of Montreal, is the world's first satellite designed to measure greenhouse gas emissions from single targeted industrial facilities. Claire was launched earlier this year into a 500 km polar sun-synchronous orbit selected to provide an acceptable balance between return frequency and spatial resolution. Extensive simulations of oil & gas facilities, power plants, hydro reservoirs and even animal feedlots were used to predict the mission performance. The principal goal is to measure the emission rates of carbon dioxide and methane from selected targets with greater precision and lower cost than ground-based alternatives. CLAIRE will measure sources having surface areas less than 10 x 10 km2 with a spatial resolution better than 50 m, thereby providing industrial site operators and government regulators with the information they need to understand, manage and ultimately to reduce greenhouse gas emissions more economically. The sensor is based on a Fabry-Perot interferometer, coupled with a 2D InGaAs focal plane array operating in the short-wave infrared with a spectral resolution of about 0.1 nm. The patented, high étendue, instrument design provides signal to noise ratios that permit quantification of emission rates with accuracies adequate for most regulatory reporting thresholds. The very high spatial resolution of the density maps produced by the CLAIRE mission resolves plume shapes and emitter locations so that advanced dispersion models can derive accurate emission rates of multiple sources within the field of view. The satellite bus, provided by the University of Toronto's Space Flight Laboratory, is based on the well-characterized NEMO architecture, including hardware that has significant spaceflight heritage. The mission is currently undergoing initial test and validation measurements in preparation for commercial operation later this year.

  5. Estimation of fossil-fuel CO2 emissions using satellite measurements of "proxy" species

    Science.gov (United States)

    Konovalov, Igor B.; Berezin, Evgeny V.; Ciais, Philippe; Broquet, Grégoire; Zhuravlev, Ruslan V.; Janssens-Maenhout, Greet

    2016-11-01

    Fossil-fuel (FF) burning releases carbon dioxide (CO2) together with many other chemical species, some of which, such as nitrogen dioxide (NO2) and carbon monoxide (CO), are routinely monitored from space. This study examines the feasibility of estimation of FF CO2 emissions from large industrial regions by using NO2 and CO column retrievals from satellite measurements in combination with simulations by a mesoscale chemistry transport model (CTM). To this end, an inverse modeling method is developed that allows estimating FF CO2 emissions from different sectors of the economy, as well as the total CO2 emissions, in a given region. The key steps of the method are (1) inferring "top-down" estimates of the regional budget of anthropogenic NOx and CO emissions from satellite measurements of proxy species (NO2 and CO in the case considered) without using formal a priori constraints on these budgets, (2) the application of emission factors (the NOx-to-CO2 and CO-to-CO2 emission ratios in each sector) that relate FF CO2 emissions to the proxy species emissions and are evaluated by using data of "bottom-up" emission inventories, and (3) cross-validation and optimal combination of the estimates of CO2 emission budgets derived from measurements of the different proxy species. Uncertainties in the top-down estimates of the NOx and CO emissions are evaluated and systematic differences between the measured and simulated data are taken into account by using original robust techniques validated with synthetic data. To examine the potential of the method, it was applied to the budget of emissions for a western European region including 12 countries by using NO2 and CO column amounts retrieved from, respectively, the OMI and IASI satellite measurements and simulated by the CHIMERE mesoscale CTM, along with the emission conversion factors based on the EDGAR v4.2 emission inventory. The analysis was focused on evaluation of the uncertainty levels for the top-down NOx and CO emission

  6. Early assessment of Integrated Multi-satellite Retrievals for Global Precipitation Measurement over China

    Science.gov (United States)

    Guo, Hao; Chen, Sheng; Bao, Anming; Behrangi, Ali; Hong, Yang; Ndayisaba, Felix; Hu, Junjun; Stepanian, Phillip M.

    2016-07-01

    Two post-real time precipitation products from the Integrated Multi-satellite Retrievals for Global Precipitation Measurement Mission (IMERG) are systematically evaluated over China with China daily Precipitation Analysis Product (CPAP) as reference. The IMERG products include the gauge-corrected IMERG product (IMERG_Cal) and the version of IMERG without direct gauge correction (IMERG_Uncal). The post-research TRMM Multisatellite Precipitation Analysis version 7 (TMPA-3B42V7) is also evaluated concurrently with IMERG for better perspective. In order to be consistent with CPAP, the evaluation and comparison of selected products are performed at 0.25° and daily resolutions from 12 March 2014 through 28 February 2015. The results show that: Both IMERG and 3B42V7 show similar performances. Compared to IMERG_Uncal, IMERG_Cal shows significant improvement in overall and conditional bias and in the correlation coefficient. Both IMERG_Cal and IMERG_Uncal perform relatively poor in winter and over-detect slight precipitation events in northwestern China. As an early validation of the GPM-era IMERG products that inherit the TRMM-era global satellite precipitation products, these findings will provide useful feedbacks and insights for algorithm developers and data users over China and beyond.

  7. POGO satellite orbit corrections: an opportunity to improve the quality of the geomagnetic field measurements?

    Science.gov (United States)

    Stockmann, Reto; Christiansen, Freddy; Olsen, Nils; Jackson, Andrew

    2015-06-01

    We present an attempt to improve the quality of the geomagnetic field measurements from the Polar Orbiting Geophysical Observatory (POGO) satellite missions in the late 1960s. Inaccurate satellite positions are believed to be a major source of errors for using the magnetic observations for field modelling. To improve the data, we use an iterative approach consisting of two main parts: one is a main field modelling process to obtain the radial field gradient to perturb the orbits and the other is the state-of-the-art GPS orbit modelling software BERNESE to calculate new physical orbits. We report results based on a single-day approach showing a clear increase of the data quality. That single-day approach leads, however, to undesirable orbital jumps at midnight. Furthermore, we report results obtained for a much larger data set comprising almost all of the data from the three missions. With this approach, we eliminate the orbit discontinuities at midnight but only tiny quality improvements could be achieved for geomagnetically quiet data. We believe that improvements to the data are probably still possible, but it would require the original tracking observations to be found.

  8. Satellite quenching time-scales in clusters from projected phase space measurements matched to simulated orbits

    Science.gov (United States)

    Oman, Kyle A.; Hudson, Michael J.

    2016-12-01

    We measure the star formation quenching efficiency and time-scale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed Sloan Digital Sky Survey galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample (109-10^{11.5}M_{⊙}) by massive (> 10^{13} M_{⊙}) clusters is essentially 100 per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first pericentric passage. There is little variation in the onset of quenching from galaxy-to-galaxy: the spread in this time is at most ˜2 Gyr at fixed M*. Higher mass satellites quench earlier, with very little dependence on host cluster mass in the range probed by our sample.

  9. An Ad-hoc Satellite Network to Measure Filamentary Current Structures in the Auroral Zone

    Science.gov (United States)

    Nabong, C.; Fritz, T. A.; Semeter, J. L.

    2014-12-01

    An ad-hoc cubesat-based satellite network project known as ANDESITE is under development at Boston University. It aims to develop a dense constellation of easy-to-use, rapidly-deployable low-cost wireless sensor nodes in space. The objectives of the project are threefold: 1) Demonstrate viability of satellite based sensor networks by deploying an 8-node miniature sensor network to study the filamentation of the field aligned currents in the auroral zones of the Earth's magnetosphere. 2) Test the scalability of proposed protocols, including localization techniques, tracking, data aggregation, and routing, for a 3 dimensional wireless sensor network using a "flock" of nodes. 3) Construct a 6U Cube-sat running the Android OS as an integrated constellation manager, data mule and sensor node deplorer. This small network of sensor nodes will resolve current densities at different spatial resolutions in the near-Earth magnetosphere using measurements from magnetometers with 1-nT sensitivities and 0.2 nT/√Hz self-noise. Mapping of these currents will provide new constraints for models of auroral particle acceleration, wave-particle interactions, ionospheric destabilization, and other kinetic processes operating in the low-beta plasma of the near Earth magnetosphere.

  10. Surface Emissivity Retrieved with Satellite Ultraspectral IR Measurements for Monitoring Global Change

    Science.gov (United States)

    Zhou, Daniel K.; Larar, Allen M.; Liu, Xu; Smith, William L.; Schluessel, Peter

    2009-01-01

    Surface and atmospheric thermodynamic parameters retrieved with advanced ultraspectral remote sensors aboard Earth observing satellites are critical to general atmospheric and Earth science research, climate monitoring, and weather prediction. Ultraspectral resolution infrared radiance obtained from nadir observations provide atmospheric, surface, and cloud information. Presented here is the global surface IR emissivity retrieved from Infrared Atmospheric Sounding Interferometer (IASI) measurements under "clear-sky" conditions. Fast radiative transfer models, applied to the cloud-free (or clouded) atmosphere, are used for atmospheric profile and surface parameter (or cloud parameter) retrieval. The inversion scheme, dealing with cloudy as well as cloud-free radiances observed with ultraspectral infrared sounders, has been developed to simultaneously retrieve atmospheric thermodynamic and surface (or cloud microphysical) parameters. Rapidly produced surface emissivity is initially evaluated through quality control checks on the retrievals of other impacted atmospheric and surface parameters. Surface emissivity and surface skin temperature from the current and future operational satellites can and will reveal critical information on the Earth s ecosystem and land surface type properties, which can be utilized as part of long-term monitoring for the Earth s environment and global climate change.

  11. MONS on the Danish Roemer satellite Measuring Oscillations in Nearby Stars

    CERN Document Server

    Christensen-Dalsgaard, J

    2001-01-01

    MONS is the scientific project on the Danish Roemer satellite mission, which is being developed as part of the Danish Small Satellite Programme. The principal goal is to study solar-like oscillations in around 20 bright stars, with a precision that in the best cases will be limited only by the intrinsic stellar `noise'. The baseline orbit, a so-called Molniya orbit, allows access to essentially the entire sky during the planned 2-year mission. The main instrument is a short-focus reflecting telescope with an aperture of 32 cm, making two-colour measurements. A focused Field Monitor will be used to detect and correct for possible faint variable stars of substantial amplitude near the main target. In addition the Field Monitor, and the Star Trackers on the platform, may be used to observe a broad range of variable phenomena. The project has concluded the Systems Definition Phase by a successful review, and launch is scheduled for the middle of 2005.

  12. Hail detection algorithm for the Global Precipitation Measuring mission core satellite sensors

    Science.gov (United States)

    Mroz, Kamil; Battaglia, Alessandro; Lang, Timothy J.; Tanelli, Simone; Cecil, Daniel J.; Tridon, Frederic

    2017-04-01

    By exploiting an abundant number of extreme storms observed simultaneously by the Global Precipitation Measurement (GPM) mission core satellite's suite of sensors and by the ground-based S-band Next-Generation Radar (NEXRAD) network over continental US, proxies for the identification of hail are developed based on the GPM core satellite observables. The full capabilities of the GPM observatory are tested by analyzing more than twenty observables and adopting the hydrometeor classification based on ground-based polarimetric measurements as truth. The proxies have been tested using the Critical Success Index (CSI) as a verification measure. The hail detection algorithm based on the mean Ku reflectivity in the mixed-phase layer performs the best, out of all considered proxies (CSI of 45%). Outside the Dual frequency Precipitation Radar (DPR) swath, the Polarization Corrected Temperature at 18.7 GHz shows the greatest potential for hail detection among all GMI channels (CSI of 26% at a threshold value of 261 K). When dual variable proxies are considered, the combination involving the mixed-phase reflectivity values at both Ku and Ka-bands outperforms all the other proxies, with a CSI of 49%. The best-performing radar-radiometer algorithm is based on the mixed-phase reflectivity at Ku-band and on the brightness temperature (TB) at 10.7 GHz (CSI of 46%). When only radiometric data are available, the algorithm based on the TBs at 36.6 and 166 GHz is the most efficient, with a CSI of 27.5%.

  13. Direct Radiative Forcing from Saharan Mineral Dust Layers from In-situ Measurements and Satellite Retrievals

    Science.gov (United States)

    Sauer, D. N.; Vázquez-Navarro, M.; Gasteiger, J.; Chouza, F.; Weinzierl, B.

    2016-12-01

    Mineral dust is the major species of airborne particulate matter by mass in the atmosphere. Each year an estimated 200-3000 Tg of dust are emitted from the North African desert and arid regions alone. A large fraction of the dust is lifted into the free troposphere and gets transported in extended dust layers westward over the Atlantic Ocean into the Caribbean Sea. Especially over the dark surface of the ocean, those dust layers exert a significant effect on the atmospheric radiative balance though aerosol-radiation interactions. During the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013 airborne in-situ aerosol measurements on both sides of the Atlantic Ocean, near the African coast and the Caribbean were performed. In this study we use data about aerosol microphysical properties acquired between Cabo Verde and Senegal to derive the aerosol optical properties and the resulting radiative forcing using the radiative transfer package libRadtran. We compare the results to values retrieved from MSG/SEVIRI data using the RRUMS algorithm. The RRUMS algorithm can derive shortwave and longwave top-of-atmosphere outgoing fluxes using only information issued from the narrow-band MSG/SEVIRI channels. A specific calibration based on collocated Terra/CERES measurements ensures a correct retrieval of the upwelling flux from the dust covered pixels. The comparison of radiative forcings based on in-situ data to satellite-retrieved values enables us to extend the radiative forcing estimates from small-scale in-situ measurements to large scale satellite coverage over the Atlantic Ocean.

  14. Analysis of rain fade duration models for Earth-to-satellite path based on data measured in Malaysia

    Science.gov (United States)

    Dao, Hassan; Rafiqul, Islam Md; Al-Khateeb, Khalid A. S.

    2013-12-01

    Statistical analysis of rain fade duration is crucial information for system engineer to design and plan a fade mitigation technique (FMT) for the satellite communication system. An investigation is carried out based on data measured of one year period in Kuala Lumpur, Malaysia from satellite path of MEASAT3. This paper presents statistical analysis of measured fade duration on high elevation angle (77.4°) in Ku-band compared to three prediction models of fade duration. It is found that none of the models could predict measured fade duration distribution accurately.

  15. Capabilities and uncertainties of aircraft measurements for the validation of satellite precipitation products – a virtual case study

    Directory of Open Access Journals (Sweden)

    Andrea Lammert

    2015-08-01

    Full Text Available Remote sensing sensors on board of research aircraft provide detailed measurements of clouds and precipitation which can be used as reference data to validate satellite products. Such satellite derived precipitation data using passive microwave radiometers with a resolution of typically 50×50km2$50\\times50\\,\\text{km}^2$ stands against high spatial and temporal resolved airborne measurements, but only along a chosen line. This paper focuses on analysis on the uncertainty arising from the different spatial resolution and coverage. Therefore we use a perfect model approach, with a high resolved forecast model yielding perfect virtual aircraft and satellite observations. The mean precipitation and standard deviation per satellite box were estimated with a Gaussian approach. The comparison of the mean values shows a high correlation of 0.92, but a very wide spread. As criterion to define good agreement between satellite mean and reference, we choose a deviation of one standard deviation of the virtual aircraft as threshold. Considering flight tracks in the range of 50 km (one overflight, the perfect agreement of satellite and aircraft observations is only detected in 65 % of the cases. To increase this low reliability the precipitation distributions of the virtual aircraft were fitted by a gamma density function. Using the same quality criterion, the usage of gamma density fit yields an improvement of the Aircraft reliability up to 80 %.

  16. Quantifying Above-Cloud Aerosols through Integrating Multi-Sensor Measurements from A-Train Satellites

    Science.gov (United States)

    Zhang, Yan

    2012-01-01

    Quantifying above-cloud aerosols can help improve the assessment of aerosol intercontinental transport and climate impacts. Large-scale measurements of aerosol above low-level clouds had been generally unexplored until very recently when CALIPSO lidar started to acquire aerosol and cloud profiles in June 2006. Despite CALIPSO s unique capability of measuring above-cloud aerosol optical depth (AOD), such observations are substantially limited in spatial coverage because of the lidar s near-zero swath. We developed an approach that integrates measurements from A-Train satellite sensors (including CALIPSO lidar, OMI, and MODIS) to extend CALIPSO above-cloud AOD observations to substantially larger areas. We first examine relationships between collocated CALIPSO above-cloud AOD and OMI absorbing aerosol index (AI, a qualitative measure of AOD for elevated dust and smoke aerosol) as a function of MODIS cloud optical depth (COD) by using 8-month data in the Saharan dust outflow and southwest African smoke outflow regions. The analysis shows that for a given cloud albedo, above-cloud AOD correlates positively with AI in a linear manner. We then apply the derived relationships with MODIS COD and OMI AI measurements to derive above-cloud AOD over the whole outflow regions. In this talk, we will present spatial and day-to-day variations of the above-cloud AOD and the estimated direct radiative forcing by the above-cloud aerosols.

  17. Validation of Altimeter Data in the Spanish Coasts (Gulf of Cadiz and Strait of Gibraltar): Lessons Learned in the Prospect of Sentinel-3

    Science.gov (United States)

    Gomez-Enri, P.; Vignudelli, S.; Coca, J.; Tejedor, B.; Aboitiz, A.; Munoz, J. J.; Alvarez, O.; Cipollini, P.; Passaro, M.; Villares, P.

    2015-12-01

    The Gulf of Cadiz (Southwestern Iberian Peninsula) and the Strait of Gibraltar (the choke point connecting the Atlantic Ocean and the Mediterranean Sea) are being used to validate altimeter information coming from past (Envisat RA-2) and present (Cryosat-2 SIRAL) European Space Agency (ESA) missions, among others. These regions represent a valuable opportunity to validate future (Sentinel-3 SRAL) altimeter missions too. We present some of the results obtained in the study areas in terms of validation of altimeter-derived sea level data coming from Envisat RA-2 and Cryosat-2 SIRAL against the in-situ measurements, and we discuss the extension of the developed techniques to AltiKa SARAL (ISRO-CNES) and Sentinel-3 SRAL (ESA).

  18. Global top-down smoke aerosol emissions estimation using satellite fire radiative power measurements

    Directory of Open Access Journals (Sweden)

    C. Ichoku

    2013-10-01

    Full Text Available Biomass burning occurs seasonally in most vegetated parts of the world, consuming large amounts of biomass fuel, generating intense heat energy, and emitting corresponding amounts of smoke plumes that comprise different species of aerosols and trace gases. Accurate estimates of these emissions are required as model inputs to evaluate and forecast smoke plume transport and impacts on air quality, human health, clouds, weather, radiation, and climate. Emissions estimates have long been based on bottom-up approaches that are not only complex, but also fraught with compounding uncertainties. Fortunately, a series of recent studies have revealed that both the rate of biomass consumption and the rate of emission of aerosol particulate matter (PM by open biomass burning are directly proportional to the rate of release of fire radiative energy (FRE, which is fire radiative power (FRP that is measurable from satellite. This direct relationship enables the determination of coefficients of emission (Ce, which can be used to convert FRP or FRE to smoke aerosol emissions in the same manner as emission factors (EFs are used to convert burned biomass to emissions. We have leveraged this relationship to generate the first global 1° × 1° gridded Ce product for smoke aerosol or total particulate matter (TPM emissions using coincident measurements of FRP and aerosol optical thickness (AOT from the Moderate-resolution Imaging Spectro-radiometer (MODIS sensors aboard the Terra and Aqua satellites. This new Fire Energetics and Emissions Research version 1.0 (FEER.v1 Ce product has now been released to the community and can be obtained from http://feer.gsfc.nasa.gov/, along with the corresponding 1-to-1 mapping of their quality assurance (QA flags that will enable the Ce values to be filtered by quality for use in various applications. The regional averages of Ce values for different ecosystem types were found to be in the ranges of: 16–21 g MJ−1 for savanna

  19. Earth's lithospheric magnetic field determined to spherical harmonic degree 90 from CHAMP satellite measurements

    DEFF Research Database (Denmark)

    Maus, S.; Rother, M.; Hemant, K.;

    2006-01-01

    The CHAMP magnetic field mission is providing highly reliable measurements from which the global lithospheric magnetic field can be determined in unprecedented resolution and accuracy. Using almost 5 yr of data, we derive our fourth generation lithospheric field model termed MF4, which is expanded...... to spherical harmonic degree and order 90. After subtracting from the full magnetic field observations predicted fields from an internal field model up to degree 15, an external field model up to degree two, and the predicted magnetic field signatures for the eight dominant ocean tidal constituents, we fit...... of the lithospheric field down to an altitude of about 50 km at lower latitudes, with reduced accuracy in the polar regions. Crustal features come out significantly sharper than in previous models. In particular, bands of magnetic anomalies along subduction zones become visible by satellite for the first time....

  20. Equatorial ionosphere semiannual oscillation investigated from Schumann resonance measurements on board the C/NOFS satellite

    Science.gov (United States)

    Simões, Fernando; Pfaff, Robert; Freudenreich, Henry; Klenzing, Jeffrey; Rowland, Douglas; Bromund, Kenneth; Kepko, Larry; Le, Guan; Liebrecht, Maria Carmen; Martin, Steven; Uribe, Paulo

    2013-11-01

    of Schumann resonance signatures in the equatorial ionosphere offers remote sensing capabilities for the investigation of tropospheric and space weather effects in the ionosphere. Schumann resonances are electromagnetic oscillations in the earth-ionosphere cavity produced by lightning activity. Analysis of AC electric field measurements gathered by the Communications/Navigation Outage Forecasting System satellite reveals a semiannual pattern in Schumann resonance data recorded during nighttime in the equatorial ionosphere. This pattern observed in the Schumann resonance amplitude is expected to help validate—or at least constrain—potential mechanisms proposed to explain the semiannual oscillation observed in different geophysical records, such as those reported in a variety of tropospheric, ionospheric/thermospheric, and magnetospheric observations.

  1. Methods of Evaluating Thermodynamic Properties of Landscape Cover Using Multispectral Reflected Radiation Measurements by the Landsat Satellite

    Directory of Open Access Journals (Sweden)

    Yuriy Puzachenko

    2013-09-01

    Full Text Available The paper discusses methods of evaluating thermodynamic properties of landscape cover based on multi-spectral measurements by the Landsat satellites. Authors demonstrate how these methods could be used for studying functionality of landscapes and for spatial interpolation of Flux NET system measurements.

  2. An Analysis of Satellite, Radiosonde, and Lidar Observations of Upper Tropospheric Water Vapor from the Atmospheric Radiation Measurement Program

    Energy Technology Data Exchange (ETDEWEB)

    Soden, Brian J.; Turner, David D.; Lesht, B. M.; Miloshevich, Larry M.

    2004-02-25

    To improve our understanding of the distribution and radiative effects of water vapor, the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program has conducted a series of coordinated water vapor Intensive Observational Periods (IOPs). This study uses observations collected from four ARM IOPs to accomplish two goals: first, we compare radiosonde and Raman lidar observations of upper tropospheric water vapor with co-located geostationary satellite radiances at 6.7 micrometers. During all four IOPs, we find excellent agreement between the satellite and Raman lidar observations of upper tropospheric humidity with systematic differences of ~10%. In contrast, radiosondes equipped with Vaisala sensors are shown to be systematically drier in the upper troposphere by ~40% relative to both the lidar and satellite measurements. Second, we assess the performance of various "correction" strategies designed to rectify known deficiencies in the radiosonde measurements. It is shown that existing methods for correcting the radiosonde dry bias, while effective in the lower troposphere, offer little improvement in the upper troposphere. An alternative method based on variational assimilation of satellite radiances is presented and, when applied to the radiosonde measurements, is shown to significantly improve their agreement with coincident Raman lidar observations. It is suggested that a similar strategy could be used to improve the quality of the global historical record of radiosonde water vapor observations during the satellite era.

  3. Geophysical interpretation of satellite laser ranging measurements of crustal movement in California

    Science.gov (United States)

    Cohen, Steven C.

    1985-12-01

    As determined by satellite laser ranging the rate of contraction of a 900 km baseline between sites located near Quincy in northern California and San Diego in southern California is about 61-65 mm/yr with a formal uncertainty of about 10 mm/yr (Christodoulidis et al., 1985). The measured changes in baseline length are a manifestation of the relative motion between the North America and Pacific tectonic plates. This long baseline result is compared to measurements made by more conventional means on shorter baselines. Additional information based on seismiscity, geology, and theoretical modelling is also analyzed. Deformation lying within a few tens of kilometers about the major faults in southern California accounts for most, but not all, of the observed motion. Further motion is attributable to a broader-scale deformation in southern California. Data suggesting crustal movements north of the Garlock fault, in and near the southern Sierra Nevada and local motion at an observatory are also critically reviewed. The best estimates of overall motion indicated by ground observations lie between 40 and 60 mm/yr. This lies within one or two standard deviations of that deduced from satellite ranging but the possibility of some unresolved deficit cannot be entirely dismissed. The long time scale RM2 plate tectonic model of Minster and Jordan (1978) predicts a contraction between 47 and 53 mm/yr depending on the extension rate of the Basin and Range. Thus the ground based observations, SLR results, and RM2 rates differ at about the 10 mm/yr level but are not inconsistent with one another within the data and model uncertainties.

  4. Low-cost Citizen Science Balloon Platform for Measuring Air Pollutants to Improve Satellite Retrieval Algorithms

    Science.gov (United States)

    Potosnak, M. J.; Beck-Winchatz, B.; Ritter, P.

    2016-12-01

    High-altitude balloons (HABs) are an engaging platform for citizen science and formal and informal STEM education. However, the logistics of launching, chasing and recovering a payload on a 1200 g or 1500 g balloon can be daunting for many novice school groups and citizen scientists, and the cost can be prohibitive. In addition, there are many interesting scientific applications that do not require reaching the stratosphere, including measuring atmospheric pollutants in the planetary boundary layer. With a large number of citizen scientist flights, these data can be used to constrain satellite retrieval algorithms. In this poster presentation, we discuss a novel approach based on small (30 g) balloons that are cheap and easy to handle, and low-cost tracking devices (SPOT trackers for hikers) that do not require a radio license. Our scientific goal is to measure air quality in the lower troposphere. For example, particulate matter (PM) is an air pollutant that varies on small spatial scales and has sources in rural areas like biomass burning and farming practices such as tilling. Our HAB platform test flight incorporates an optical PM sensor, an integrated single board computer that records the PM sensor signal in addition to flight parameters (pressure, location and altitude), and a low-cost tracking system. Our goal is for the entire platform to cost less than $500. While the datasets generated by these flights are typically small, integrating a network of flight data from citizen scientists into a form usable for comparison to satellite data will require big data techniques.

  5. Multi-decadal satellite measurements of passive and eruptive volcanic SO2 emissions

    Science.gov (United States)

    Carn, Simon; Yang, Kai; Krotkov, Nickolay; Prata, Fred; Telling, Jennifer

    2015-04-01

    Periodic injections of sulfur gas species (SO2, H2S) into the stratosphere by volcanic eruptions are among the most important, and yet unpredictable, drivers of natural climate variability. However, passive (lower tropospheric) volcanic degassing is the major component of total volcanic emissions to the atmosphere on a time-averaged basis, but is poorly constrained, impacting estimates of global emissions of other volcanic gases (e.g., CO2). Stratospheric volcanic emissions are very well quantified by satellite remote sensing techniques, and we report ongoing efforts to catalog all significant volcanic SO2 emissions into the stratosphere and troposphere since 1978 using measurements from the ultraviolet (UV) Total Ozone Mapping Spectrometer (TOMS; 1978-2005), Ozone Monitoring Instrument (OMI; 2004 - present) and Ozone Mapping and Profiler Suite (OMPS; 2012 - present) instruments, supplemented by infrared (IR) data from HIRS, MODIS and AIRS. The database, intended for use as a volcanic forcing dataset in climate models, currently includes over 600 eruptions releasing a total of ~100 Tg SO2, with a mean eruption discharge of ~0.2 Tg SO2. Sensitivity to SO2 emissions from smaller eruptions greatly increased following the launch of OMI in 2004, but uncertainties remain on the volcanic flux of other sulfur species other than SO2 (H2S, OCS) due to difficulty of measurement. Although the post-Pinatubo 1991 era is often classified as volcanically quiescent, many smaller eruptions (Volcanic Explosivity Index [VEI] 3-4) since 2000 have injected significant amounts of SO2 into the upper troposphere - lower stratosphere (UTLS), peaking in 2008-2011. We also show how even smaller (VEI 2) tropical eruptions can impact the UTLS and sustain above-background stratospheric aerosol optical depth, thus playing a role in climate forcing on short timescales. To better quantify tropospheric volcanic degassing, we use ~10 years of operational SO2 measurements by OMI to identify the

  6. Some results on the upper atmosphere deduced from satellite occultation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Felske, D.; Knuth, R.; Martini, L.; Ohle, K.H.; Sonnemann, G.; Stark, B.

    1980-08-01

    Measurements of neutral gas densities in the upper atmosphere deduced from extinction profiles from the Intercosmos 1, 4, 7, 11 and 16 and SOLRAD 9 and 10 solar radiation satellites at sunrise and sunset are presented. Occultation measurements in the Lyman alpha range have revealed the presence of an anomalously high absorption above 110 km in winter, which may be explained by high densities of water in the thermosphere. Calculations of oxygen densities based on extinction profiles measured in Lyman alpha and the Schumann-Runge range also indicate the presence of high densities of NO, and an unknown Lyman alpha absorber of molecular weight corresponding to that of water. Observations obtained for the D-region winter anomaly indicate that the wavelike ionization variations have counterparts in similar neutral thermosphere density variations, which may influence the ion production and/or loss processes. Finally, short-term neutral density fluctuations between 90 and 300 km measured during a strong F-region disturbance are presented which demonstrate sharp rises in O density and decreases in O2 density accompanied by increases in electron concentration during the first phase of the disturbance, the opposite changes during the second phase, and complex mixing variations between O and O2 and their plasma counterparts in the recovery phase.

  7. Surface net solar radiation estimated from satellite measurements - Comparisons with tower observations

    Science.gov (United States)

    Li, Zhanqing; Leighton, H. G.; Cess, Robert D.

    1993-01-01

    A parameterization that relates the reflected solar flux at the top of the atmosphere to the net solar flux at the surface in terms of only the column water vapor amount and the solar zenith angle was tested against surface observations. Net surface fluxes deduced from coincidental collocated satellite-measured radiances and from measurements from towers in Boulder during summer and near Saskatoon in winter have mean differences of about 2 W/sq m, regardless of whether the sky is clear or cloudy. Furthermore, comparisons between the net fluxes deduced from the parameterization and from surface measurements showed equally good agreement when the data were partitioned into morning and afternoon observations. This is in contrast to results from an empirical clear-sky algorithm that is unable to account adequately for the effects of clouds and that shows, at Boulder, a distinct morning to afternoon variation. It is also demonstrated that the parameterization may be applied to irradiances at the top of the atmosphere that have been temporally averaged. The good agreement between the results of the parameterization and surface measurements suggests that the algorithm is a useful tool for a variety of climate studies.

  8. Surface Net Solar Radiation Estimated from Satellite Measurements: Comparisons with Tower Observations

    Science.gov (United States)

    Li, Zhanqing; Leighton, H. G.; Cess, Robert D.

    1993-01-01

    A parameterization that relates the reflected solar flux at the top of the atmosphere to the net solar flux at the surface in terms of only the column water vapor amount and the solar zenith angle was tested against surface observations. Net surface fluxes deduced from coincidental collocated satellite-measured radiances and from measurements from towers in Boulder during summer and near Saskatoon in winter have mean differences of about 2 W/sq m, regardless of whether the sky is clear or cloudy. Furthermore, comparisons between the net fluxes deduced from the parameterization and from surface measurements showed equally good agreement when the data were partitioned into morning and afternoon observations. This is in contrast to results from an empirical clear-sky algorithm that is unable to account adequately for the effects of clouds and that shows, at Boulder, a distinct morning to afternoon variation, which is presumably due to the predominance of different cloud types throughout the day. It is also demonstrated that the parameterization may be applied to irradiances at the top of the atmosphere that have been temporally averaged by using the temporally averaged column water vapor amount and the temporally averaged cosine of the solar zenith angle. The good agreement between the results of the parameterization and surface measurements suggests that the algorithm is a useful tool for a variety of climate studies.

  9. An Algorithm for Detection of Ground and Canopy Cover in Micropulse Photon-Counting Lidar Altimeter Data in Preparation of the ICESat-2 Mission

    Science.gov (United States)

    Herzfeld, Ute C.; McDonald, Brian W.; Wallins, Bruce F.; Markus, Thorsten; Neumann, Thomas A.; Brenner, Anita

    2012-01-01

    The Ice, Cloud and Land Elevation Satellite-II (ICESat-2) mission has been selected by NASA as a Decadal Survey mission, to be launched in 2016. Mission objectives are to measure land ice elevation, sea ice freeboard/ thickness and changes in these variables and to collect measurements over vegetation that will facilitate determination of canopy height, with an accuracy that will allow prediction of future environmental changes and estimation of sea-level rise. The importance of the ICESat-2 project in estimation of biomass and carbon levels has increased substantially, following the recent cancellation of all other planned NASA missions with vegetation-surveying lidars. Two innovative components will characterize the ICESat-2 lidar: (1) Collection of elevation data by a multi-beam system and (2) application of micropulse lidar (photon counting) technology. A micropulse photon-counting altimeter yields clouds of discrete points, which result from returns of individual photons, and hence new data analysis techniques are required for elevation determination and association of returned points to reflectors of interest including canopy and ground in forested areas. The objective of this paper is to derive and validate an algorithm that allows detection of ground under dense canopy and identification of ground and canopy levels in simulated ICESat-2-type data. Data are based on airborne observations with a Sigma Space micropulse lidar and vary with respect to signal strength, noise levels, photon sampling options and other properties. A mathematical algorithm is developed, using spatial statistical and discrete mathematical concepts, including radial basis functions, density measures, geometrical anisotropy, eigenvectors and geostatistical classification parameters and hyperparameters. Validation shows that the algorithm works very well and that ground and canopy elevation, and hence canopy height, can be expected to be observable with a high accuracy during the ICESat

  10. Satellite Altimetry and GRACE Gravimetry for Studies of Annual Water Storage Variations in Bangladesh

    Directory of Open Access Journals (Sweden)

    Ole Andersen

    2008-01-01

    Full Text Available Four different data sources have been compared with respect to observations of the annual water storage variations in the region of Bangladesh. Data from satellite altimeters and river gauges estimates the variation in surface water storage in the major rivers of Bangladesh. The GRACE satellites measure the integrated mass change and hence the terrestrial soil moisture variations, which can also be estimated by a hydrological model (GLDAS. These types of observations enable the derivation of the integrated water storage in the entire region of Bangladesh. For all data types, the annual signal has been estimated from a common dataset spanning the period 2003 and 2004. All four different data observe that water storage in Bangladesh is largely dominated by an annual signal with a phase peaking in early September. The annual variations in river level peaks roughly two weeks earlier than terrestrial soil moisture observations by GRACE observations and GLDAS model output.

  11. Satellite altimetry and GRACE gravimetry for studies of annual water storage variations in Bangladesh

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Berry, P.; Freeman, J.;

    2008-01-01

    Four different data sources have been compared with respect to observations of the annual water storage variations in the region of Bangladesh. Data from satellite altimeters and river gauges estimates the variation in surface water storage in the major rivers of Bangladesh. The GRACE satellites...... measure the integrated mass change and hence the terrestrial soil moisture variations, which can also be estimated by a hydrological model (GLDAS). These types of observations enable the derivation of the integrated water storage in the entire region of Bangladesh. For all data types, the annual signal...... has been estimated from a common dataset spanning the period 2003 and 2004. All four different data observe that water storage in Bangladesh is largely dominated by an annual signal with a phase peaking in early September. The annual variations in river level peaks roughly two weeks earlier than...

  12. Vertical profiles of aerosol optical properties over central Illinois and comparison with surface and satellite measurements

    Directory of Open Access Journals (Sweden)

    P. J. Sheridan

    2012-12-01

    Full Text Available Between June 2006 and September 2009, an instrumented light aircraft measured over 400 vertical profiles of aerosol and trace gas properties over eastern and central Illinois. The primary objectives of this program were to (1 measure the in situ aerosol properties and determine their vertical and temporal variability and (2 relate these aircraft measurements to concurrent surface and satellite measurements. The primary profile location was within 15 km of the NOAA/ESRL surface aerosol monitoring station near Bondville, Illinois. Identical instruments at the surface and on the aircraft ensured that the data from both platforms would be directly comparable and permitted a determination of how representative surface aerosol properties were of the lower column. Aircraft profiles were also conducted occasionally at two other nearby locations to increase the frequency of A-Train satellite underflights for the purpose of comparing in situ and satellite-retrieved aerosol data. Measurements of aerosol properties conducted at low relative humidity over the Bondville site compare well with the analogous surface aerosol data and do not indicate any major sampling issues or that the aerosol is radically different at the surface compared with the lowest flyby altitude of ~ 240 m above ground level. Statistical analyses of the in situ vertical profile data indicate that aerosol light scattering and absorption (related to aerosol amount decreases substantially with increasing altitude. Parameters related to the nature of the aerosol (e.g., single-scattering albedo, Ångström exponent, etc., however, are relatively constant throughout the mixed layer, and do not vary as much as the aerosol amount throughout the profile. While individual profiles often showed more variability, the median in situ single-scattering albedo was 0.93–0.95 for all sampled altitudes. Several parameters (e.g., submicrometer scattering fraction, hemispheric backscattering fraction, and

  13. A Methodology For Measuring Resilience in a Satellite-Based Communication Network

    Science.gov (United States)

    2014-03-27

    In the cyber realm, most satellite operators were in compliance with the National Security Agency’s (NSA) approved encryptions for transmissions...and more continue to meet compliance as new satellites are placed in orbit. Along with the encryptions , many 17 satellite operators utilize “deaf...nation at war may be of higher concern than the nation providing backdoor support which is higher than a neutral nation, and so on until a region not

  14. Far from thunderstorm UV transient events in the atmosphere measured by Vernov satellite

    Science.gov (United States)

    Morozenko, Violetta; Klimov, Pavel; Khrenov, Boris; Gali, Garipov; Margarita, Kaznacheeva; Mikhail, Panasyuk; Sergei, Svertilov; Robert, Holzworth

    2016-04-01

    The steady self-contained classification of events such as sprites, elves, blue jets emerged for the period of transient luminous events (TLE) observation. In accordance with TLE origin theories the presence of the thunderstorm region where the lightnings with the large peak current generating in is necessary. However, some far-from-thunderstorm region events were also detected and revealed to us another TLE generating mechanisms. For the discovering of the TLE nature the Universitetsky-Tatiana-2 and Vernov satellites were equipped with ultraviolet (240-400 nm) and red-infrared ( >610 nm) detectors. In both detector it was carried out regardless the lightnings with the guidance by the flashes in the UV wavelength where lightning's emitting is quite faint. The lowered threshold on the Vernov satellite allowed to select the great amount of TLE with the numerous far-from-thunderstorm region events examples. such events were not conjuncted with lightning activity measured by global lightning location network (WWLLN) on the large area of approximately 107 km2 for 30 minutes before and after the time of registration. The characteristic features of this type of event are: the absence of significant signal in the red-infrared detector's channel; a relatively small number of photons (less than 5 ṡ 1021). A large number of without lightning flash were detected at high latitudes over the ocean (30°S - 60°S). Lightning activity in the magnetic conjugate point also was analyzed. The relationship of far-from-thunderstorm region events with the specific lightning discharges didn't confirmed. Far-from-thunderstorm events - a new type of transient phenomena in the upper atmosphere is not associated with the thunderstorm activity. The mechanism of such discharges is not clear, though it was accumulated a sufficient amount of experimental facts of the existence of such flashes. According to the data of Vernov satellite the temporal profile, duration, location with earth

  15. Integration of radar altimeter, precision navigation, and digital terrain data for low-altitude flight

    Science.gov (United States)

    Zelenka, Richard E.

    1992-01-01

    Avionic systems that depend on digitized terrain elevation data for guidance generation or navigational reference require accurate absolute and relative distance measurements to the terrain, especially as they approach lower altitudes. This is particularly exacting in low-altitude helicopter missions, where aggressive terrain hugging maneuvers create minimal horizontal and vertical clearances and demand precise terrain positioning. Sole reliance on airborne precision navigation and stored terrain elevation data for above-ground-level (AGL) positioning severely limits the operational altitude of such systems. A Kalman filter is presented which blends radar altimeter returns, precision navigation, and stored terrain elevation data for AGL positioning. The filter is evaluated using low-altitude helicopter flight test data acquired over moderately rugged terrain. The proposed Kalman filter is found to remove large disparities in predicted AGL altitude (i.e., from airborne navigation and terrain elevation data) in the presence of measurement anomalies and dropouts. Previous work suggested a minimum clearance altitude of 220 ft AGL for a near-terrain guidance system; integration of a radar altimeter allows for operation of that system below 50 ft, subject to obstacle-avoidance limitations.

  16. ALGORITHM OF SAR SATELLITE ATTITUDE MEASUREMENT USING GPS AIDED BY KINEMATIC VECTOR

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, in order to improve the accuracy of the Synthetic Aperture Radar (SAR)satellite attitude using Global Positioning System (GPS) wide-band carrier phase, the SAR satellite attitude kinematic vector and Kalman filter are introduced. Introducing the state variable function of GPS attitude determination algorithm in SAR satellite by means of kinematic vector and describing the observation function by the GPS wide-band carrier phase, the paper uses the Kalman filter algorithm to obtian the attitude variables of SAR satellite. Compared the simulation results of Kalman filter algorithm with the least square algorithm and explicit solution, it is indicated that the Kalman filter algorithm is the best.

  17. Detailed gravimetric geoid confirmation of short wavelength features of sea surface topography detected by the Skylab S-193 altimeter in the Atlantic Ocean

    Science.gov (United States)

    Marsh, J. G.; Vincent, S.; Mcclinton, A. T.; Chang, E. S.

    1975-01-01

    A detailed gravimetric geoid was computed for the Northwest Atlantic Ocean and Caribbean Sea area in support of the calibration and evaluation of the GEOS-C altimeter. This geoid, computed on a 15 ft. x 15 ft. grid was based upon a combination of surface gravity data with the GSFC GEM-6 satellite derived gravity data. A comparison of this gravimetric geoid with 10 passes of SKYLAB altimeter data is presented. The agreement of the two data types is quite good with the differences generally less than 2 meters. Sea surface manifestations of numerous short wavelength (approximately 100 km) oceanographic features are now indicated in the gravimetric geoid and are also confirmed by the altimetry data.

  18. Cosmic radiation measurements on the Foton-M4 satellite by passive detectors

    Science.gov (United States)

    Strádi, Andrea; Pálfalvi, József K.; Szabó, Julianna; Pázmándi, Tamás; Ivanova, Olga A.; Shurshakov, Vyacheslav A.

    2017-02-01

    The Russian Foton spacecraft was designed to deliver scientific experiments to low Earth orbit and return them safely to the ground for further analysis. During the 44-d Foton-M4 satellite mission in 2014 several passive cosmic ray detectors were exposed outside (in a single holder) and inside (in 4 locations) the recoverable capsule to study the radiation field. The applied thermoluminescent detectors (TLDs) are more sensitive to the particles with LET under 10 keV μm-1, while the solid state nuclear track detectors (SSNTDs) measure the particles having LET over this value. According to our measurements the average internal absorbed dose rate varied between 374-562 μGy/day for low LET radiation and 40-52 μGy/day for high LET radiation. Outside the capsule the dose rate was much higher, 1078 μGy/day for low LET radiation and 75 μGy/day for high LET radiation. Within the paper the obtained absorbed dose rates has been compared to those measured on the previous Foton-M flights, during the Bion-M1 mission and in the Columbus module of the International Space Station.

  19. A New Satellite Measurement Capability for Assessing Damage to Crops from Regional Scale Ozone Pollution

    Science.gov (United States)

    Fishman, J. J.; Creilson, J. K.; Parker, P. A.; Ainsworth, E. A.; Vining, G. G.; Szarka, J. L.

    2009-05-01

    High concentrations of ground-level ozone are frequently measured over farmland regions in many parts of the world. Since laboratory data show that ozone can significantly impact crop productivity if levels above a threshold concentration are reached, there is a consensus that crop yield should be impacted now and that the effects will become even more detrimental as global background concentrations continue to rise, as suggested by the latest IPCC report. Using the long-term record of tropospheric ozone derived from satellite measurements (http://asd-www.larc.nasa.gov/TOR/data.html), we present a methodology that can be used to assess the impact of regional ozone pollution on crop productivity. In this study, we use soybean crop yield data during a 5-year period over the Midwest of the United States and analyze the results using multiple linear regression statistical models. The results are consistent with findings using conventional ground-based measurements and with results obtained from an open-air experimental facility SoyFACE (Soybean Free Air Concentration Enrichment) in central Illinois. Our analysis suggests that the cost to the farmers globally is substantial, and supports other studies that calculate an economic loss to the farming community of more than 10 billion dollars annually.

  20. Comprehensive Spectral Signal Investigation of a Larch Forest Combining - and Satellite-Based Measurements

    Science.gov (United States)

    Landmann, J. M.; Rutzinger, M.; Bremer, M.; chmidtner, K.

    2016-06-01

    Collecting comprehensive knowledge about spectral signals in areas composed by complex structured objects is a challenging task in remote sensing. In the case of vegetation, shadow effects on reflectance are especially difficult to determine. This work analyzes a larch forest stand (Larix decidua MILL.) in Pinnis Valley (Tyrol, Austria). The main goal is extracting the larch spectral signal on Landsat 8 (LS8) Operational Land Imager (OLI) images using ground measurements with the Cropscan Multispectral Radiometer with five bands (MSR5) simultaneously to satellite overpasses in summer 2015. First, the relationship between field spectrometer and OLI data on a cultivated grassland area next to the forest stand is investigated. Median ground measurements for each of the grassland parcels serve for calculation of the mean difference between the two sensors. Differences are used as "bias correction" for field spectrometer values. In the main step, spectral unmixing of the OLI images is applied to the larch forest, specifying the larch tree spectral signal based on corrected field spectrometer measurements of the larch understory. In order to determine larch tree and shadow fractions on OLI pixels, a representative 3D tree shape is used to construct a digital forest. Benefits of this approach are the computational savings compared to a radiative transfer modeling. Remaining shortcomings are the limited capability to consider exact tree shapes and nonlinear processes. Different methods to implement shadows are tested and spectral vegetation indices like the Normalized Difference Vegetation Index (NDVI) and Greenness Index (GI) can be computed even without considering shadows.

  1. First satellite measurements of chemical changes in coincidence with sprite activity

    Science.gov (United States)

    Arnone, Enrico; São Sabbas, Fernanda; Kero, Antti; Soula, Serge; Carlotti, Massimo; Chanrion, Olivier; Dinelli, Bianca Maria; Papandrea, Enzo; Castelli, Elisa; Neubert, Torsten

    2010-05-01

    The last twenty years have seen the discovery of electric discharges in the Earth's atmosphere above thunderstorms, the so-called sprites and jets. It has been suggested that they impact the atmospheric chemistry and possibly affect the ozone layer through their repeated occurrence. Whereas theoretical studies and laboratory experiments suggest enhancement of such gasses as nitrogen oxides by up to hundreds of percent within sprites, a definitive detection of their chemical effects have to date been unsuccessful. In this paper, we report on the first measurements of atmospheric chemical perturbations recorded in coincidence with sprite activity. A striking event occurred on 25 August 2003 when the MIPAS spectrometer onboard the Envisat satellite recorded spectroscopic measurements soon after a sequence of 11 sprites observed above Corsica (France) by Eurosprite ground facilities (details of the convective system are discussed in a companion paper by São Sabbas et al.). The measurements show an enhancement of ambient nitrous oxide by 80% at 52 km altitude in the region above the parent thunderstorm. The recorded chemical changes imply sprites can exert significant modification of the atmospheric chemistry at a regional scale, confirming model and laboratory predictions of sprite-chemistry, and requiring a new estimate of their global impact. The results of the analysis and their implications are discussed.

  2. Measurement of interseismic strain accumulation across the North Anatolian Fault by satellite radar interferometry

    Science.gov (United States)

    Wright, Tim; Parsons, Barry; Fielding, Eric

    In recent years, interseismic crustal velocities and strains have been determined for a number of tectonically active areas through repeated measurements using the Global Positioning System. The terrain in such areas is often remote and difficult, and the density of GPS measurements relatively sparse. In principle, satellite radar interferometry can be used to make millimetric-precision measurements of surface displacement over large surface areas. In practice, the small crustal deformation signal is dominated over short time intervals by errors due to atmospheric, topographic and orbital effects. Here we show that these effects can be over-come by stacking multiple interferograms, after screening for atmospheric anomalies, effectively creating a new interferogram that covers a longer time interval. In this way, we have isolated a 70 km wide region of crustal deformation across the eastern end of the North Anatolian Fault, Turkey. The distribution of deformation is consistent with slip of 17-32 mm/yr below 5-33 km on the extension of the surface fault at depth. If the GPS determined slip rate of 24±1 mm/yr is accepted, the locking depth is constrained to 18±6 km.

  3. Global Characterization of Biomass-Burning Patterns using Satellite Measurements of Fire Radiative Energy

    Science.gov (United States)

    Ichoku, Charles; Giglio, Louis; Wooster, Martin J.; Remer, Lorraine A.

    2008-01-01

    Remote sensing is the most practical means of measuring energy release from large open-air biomass burning. Satellite measurement of fire radiative energy (FRE) release rate or power (FRP) enables distinction between fires of different strengths. Based on a 1-km resolution fire data acquired globally by the MODerate-resolution Imaging Spectro-radiometer (MODIS) sensor aboard the Terra and Aqua satellites from 2000 to 2006, instanteaneous FRP values ranged between 0.02 MW and 1866 MW, with global daily means ranging between 20 and 40 MW. Regionally, at the Aqua-MODIS afternoon overpass, the mean FRP values for Alaska, Western US, Western Australia, Quebec and the rest of Canada are significantly higher than these global means, with Quebec having the overall highest value of 85 MW. Analysis of regional mean FRP per unit area of land (FRP flux) shows that a peak fire season in certain regions, fires can be responsible for up to 0.2 W/m(sup 2) at peak time of day. Zambia has the highest regional monthly mean FRP flux of approximately 0.045 W/m(sup 2) at peak time of day and season, while the Middle East has the lowest value of approximately 0.0005 W/m(sup 2). A simple scheme based on FRP has been devised to classify fires into five categories, to facilitate fire rating by strength, similar to earthquakes and hurricanes. The scheme uses MODIS measurements of FRP at 1-km resolution as follows: catagory 1 (less than 100 MW), category 2 (100 to less than 500 MW), category 3 (500 to less than 1000 MW), category 4 (1000 to less than 1500 MW), catagory 5 (greater than or equal to 1500 MW). In most regions of the world, over 90% of fires fall into category 1, while only less than 1% fall into each of categories 3 to 5, although these proportions may differ significantly from day to day and by season. The frequency of occurence of the larger fires is region specific, and could not be explained by ecosystem type alone. Time-series analysis of the propertions of higher category

  4. Scientific - Educational Micro-satellite "kolibri-2000": First Results of Measurements

    Science.gov (United States)

    Klimov, S. I.; Nozdrachev, M. N.; Tamkovich, G. M.; Grushin, V. A.; Grachov, Ye. A.; Grigoryan, O. R.; Afanasyev, Yu. V.; Zaitzev, A. N.; Farnakeev, I. V.; Parrot, M.

    Space today is an environment with intensive practical activity of mankind. The results of mastering of space are used in many ways, including education. School is a natural way to inform a broad public about space research. In this paper we will present the Program of Scientific - Educational Micro-satellite http://www.iki.rssi.ru/kollibri/mission1_e.htm. The space science and technologies that can be used as teaching tools in Program are: 1) The space systems of teleme- try, television, operational meteorological observations, remote exploration of the ground, and high-precision navigational systems which have become necessary and economically feasible parts of our life. 2) The space environment also attracts at- tention, as actively influencing many highly technological systems and the biosphere of the Earth, including the health of man. Space weather is becoming as well- known as (meteorological) weather. The first project of the Program is the Russian- Australian micro-satellite "Kolibri-2000" (total mass 22 kg) which start the oper- ation at the end of February 2002. In the project, several schools participate, in- cluding Russian schools sponsored by the Institute of Atomic Energy and Tech- nology (IAET, Obninsk www.obninsk.org) and two Australian schools in Sydney, Knox Grammar School www.knox.nsw.edu.au and Ravenswood School for Girls www.ravenswood.nsw.edu.au. "Kolibri-2000" is equipped with instruments to mea- sure and study the magnetic and electric field, and the radiation belts of the Earth. In this paper we will present the first measurements on the orbit near International Space Station.

  5. Receiver characteristics of laser altimeters with avalanche photodiodes

    Science.gov (United States)

    Sun, Xiaoli; Davidson, Frederic M.; Boutsikaris, Leo; Abshire, James B.

    1992-01-01

    The receiver characteristics of a laser altimeter system containing an avalanche photodiode photodetector are analyzed using the Gaussian approximation, the saddle-point approximation, and a nearly exact analysis. The last two methods are shown to yield very similar results except when the background noise is extremely low and the probability of false alarm is high. However, the Gaussian approximation method is shown to cause significant errors even under relatively high levels of background noise and received signal energy.

  6. Improving the Accuracy of Satellite Sea Surface Temperature Measurements by Explicitly Accounting for the Bulk-Skin Temperature Difference

    Science.gov (United States)

    Castro, Sandra L.; Emery, William J.

    2002-01-01

    The focus of this research was to determine whether the accuracy of satellite measurements of sea surface temperature (SST) could be improved by explicitly accounting for the complex temperature gradients at the surface of the ocean associated with the cool skin and diurnal warm layers. To achieve this goal, work centered on the development and deployment of low-cost infrared radiometers to enable the direct validation of satellite measurements of skin temperature. During this one year grant, design and construction of an improved infrared radiometer was completed and testing was initiated. In addition, development of an improved parametric model for the bulk-skin temperature difference was completed using data from the previous version of the radiometer. This model will comprise a key component of an improved procedure for estimating the bulk SST from satellites. The results comprised a significant portion of the Ph.D. thesis completed by one graduate student and they are currently being converted into a journal publication.

  7. New astrometric measurement and reduction of USNO photographic observations of the main Saturnian satellites: 1974-1998

    Science.gov (United States)

    Robert, V.; Pascu, D.; Lainey, V.; Arlot, J.-E.; De Cuyper, J.-P.; Dehant, V.; Thuillot, W.

    2016-11-01

    Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of their orbits and dynamics, and to infer the accuracy of the planet and satellite ephemerides. Aims: In the framework of the European FP7 ESPaCE program, we provide the positions of Saturn and its main satellites taken with the US Naval Observatory 26-inch refractor from 1974 to 1998. Methods: We measured 526 astrophotographic plates with the digitizer of the Royal Observatory of Belgium and reduced them through an optimal process that includes image, instrumental, and spherical corrections using the UCAC4 catalog to provide the most accurate equatorial (RA, Dec) positions. Results: We compared the observed positions of the satellites with the theoretical positions from INPOP13c and DE432 planetary ephemerides and from NOE-6-2015-SAT and SAT375 satellite ephemerides. The mean post-fit rms residuals in equatorial positions range from ±68 mas for the Titan observations or 400 km at Saturn, to ±100 mas for the Hyperion observations or 600 km at Saturn. The mean post-fit rms intersatellite residuals range from ±46 mas for the Rhea-Titan observations or 280 km at Saturn, to ±72 mas for the Hyperion-Titan observations or 430 km at Saturn. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A37 , at the Natural Satellites DataBase and Natural Satellites Data Center services of IMCCE via http://nsdb.imcce.fr/ or http://www.imcce.fr/nsdc/

  8. Satellite-based RAR performance simulation for measuring directional ocean wave spectrum based on SAR inversion spectrum

    Institute of Scientific and Technical Information of China (English)

    REN Lin; MAO Zhihua; HUANG Haiqing; GONG Fang

    2010-01-01

    Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence. Both them have their own advantages and limitations. Scientists hope that SAR and satellite-based RAR can complement each other for the research on wave properties in the future. For this study, the authors aim to simulate the satellite-based RAR system to validate performance for measuring the directional wave spectrum. The principal measurements are introduced and the simulation methods based on the one developed by Hauser are adopted and slightly modified. To enhance the authenticity of input spectrum and the wave spectrum measuring consistency for SAR and satellite-based RAR, the wave height spectrum inversed from Envisat ASAR data by cross spectrum technology is used as the input spectrum of the simulation system. In the process of simulation, the sea surface, backscattering signal, modulation spectrum and the estimated wave height spectrum are simulated in each look direction. Directional wave spectrum are measured based on the simulated observations from 0° to 360~. From the estimated wave spectrum, it has an 180° ambiguity like SAR, but it has no special high wave number cut off in all the direction. Finally, the estimated spectrum is compared with the input one in terms of the dominant wave wavelength, direction and SWH and the results are promising. The simulation shows that satellite-based RAR should be capable of measuring the directional wave properties. Moreover, it indicates satellite-based RAR basically can measure waves that SAR can measure.

  9. Signature of range observable in non-dynamical Chern-Simons modified gravity and the measurements with satellite-satellite tracking missions. Theoretical Studies

    CERN Document Server

    Qiang, Li-E

    2014-01-01

    Having great accuracy in the range and range rate measurements, the operating GRACE mission and the planed GRACE Follow On mission can in principle be employed to place strong constraints on certain relativistic gravity theories. In this paper, we work out in details the range observable in the non-dynamical Chern-Simons modified gravity for these Satellite-Satellite Tracking measurements. We find out that an characteristic time accumulating signal appears in the range observable in the non-dynamical Chern-Simons gravity, which has no analogy found in the standard metric theories of gravity. The magnitude of this Chern-Simons range signal will reach to a few times of $(\\frac{\\dot{\\theta}}{100r})meters$ for each free flight of these SST missions, here $\\dot{\\theta}$ measures the length scale of the theory and $r$ denotes the orbital radius of the SST mission. Therefore, with the 12 years data from the GRACE mission and the proper data analysis methods, one expects that the mass scale of the non-dynamical CS gr...

  10. Tidally induced velocity variations of the Beardmore Glacier, Antarctica, and their representation in satellite measurements of ice velocity

    Directory of Open Access Journals (Sweden)

    O. J. Marsh

    2013-09-01

    Full Text Available Ocean tides close to the grounding line of outlet glaciers around Antarctica have been shown to directly influence ice velocity, both linearly and non-linearly. These fluctuations can be significant and have the potential to affect satellite measurements of ice discharge, which assume displacement between satellite passes to be consistent and representative of annual means. Satellite observations of horizontal velocity variation in the grounding zone are also contaminated by vertical tidal effects, the importance of which is highlighted here in speckle tracking measurements. Eight TerraSAR-X scenes from the grounding zone of the Beardmore Glacier are analysed in conjunction with GPS measurements to determine short-term and decadal trends in ice velocity. Diurnal tides produce horizontal velocity fluctuations of >50% on the ice shelf, recorded in the GPS data 4 km downstream of the grounding line. This variability decreases rapidly to <5% only 15 km upstream of the grounding line. Daily fluctuations are smoothed to <1% in the 11-day repeat pass TerraSAR-X imagery, but fortnightly variations over this period are still visible and show that satellite-velocity measurements can be affected by tides over longer periods. The measured tidal displacement observed in radar look direction over floating ice also allows the grounding line to be identified, using differential speckle tracking where phase information cannot be easily unwrapped.

  11. Comparison of Historical Satellite-Based Estimates of Solar Radiation Resources with Recent Rotating Shadowband Radiometer Measurements: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Myers, D. R.

    2009-03-01

    The availability of rotating shadow band radiometer measurement data at several new stations provides an opportunity to compare historical satellite-based estimates of solar resources with measurements. We compare mean monthly daily total (MMDT) solar radiation data from eight years of NSRDB and 22 years of NASA hourly global horizontal and direct beam solar estimates with measured data from three stations, collected after the end of the available resource estimates.

  12. Solar absorption estimated from surface radiation measurements and collocated satellite products over Europe

    Science.gov (United States)

    Zyta Hakuba, Maria; Folini, Doris; Wild, Martin; Sanchez-Lorenzo, Arturo

    2013-04-01

    Anthropogenic climate change is physically speaking a perturbation of the atmospheric energy budget through the insertion of constituents such as greenhouse gases or aerosols. Changes in the atmospheric energy budget largely affect the global climate and hydrological cycle, but the quantification of the different energy balance components is still afflicted with large uncertainties. The overall aim of the present study is the assessment of the mean state and the spatio-temporal variations in the solar energy disposition, in which we focus on obtaining an accurate partitioning of absorbed solar radiation between the surface and the atmosphere. Surface based measurements of solar radiation (GEBA, BSRN) are combined with collocated satellite-retrieved surface albedo (MODIS, CERES FSW, or CM SAF GAC-SAL) and top-of-atmosphere net incoming solar radiation (CERES EBAF) to quantify the absorbed solar radiation (ASR) at the surface and within the atmosphere over Europe for the period 2001-2005. In a first step, we examine the quality and temporal homogeneity of the monthly time series beyond 2000 provided by GEBA in order to identify a subset of sufficient quality. We find the vast majority of monthly time series to be suitable for our purposes. Using the satellite-derived CM SAF surface solar radiation product at 0.03° spatial resolution, we assess the spatial representativeness of the GEBA and BSRN sites for their collocated 1° grid cells as we intend to combine the point measurements with the coarser resolved CERES EBAF products (1° resolution), and we find spatial sampling errors of on average 3 Wm-2 or 2% (normalized by point values). Based on the combination of 134 GEBA surface solar radiation (SSR) time series with MODIS white-sky albedo and CERES EBAF top-of-atmosphere net radiation (TOAnet), we obtain a European mean partitioning (2001-2005) of absorbed solar radiation (relative to total incoming radiation) of: ASRsurf= 41% and ASRatm= 25%, together equaling

  13. Lunar topographic model CLTM-s01 from Chang'E-1 laser altimeter

    Institute of Scientific and Technical Information of China (English)

    PING JinSong; HUANG Qian; YAN JianGuo; CAO JianFeng; TANG GeShi; SHU Rong

    2009-01-01

    More than 3 million range measurements from the Chang'E-1 Laser Altimeter have been used to pro-duce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang'E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25° (~7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, re-spectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (-1.777, -0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings.

  14. Lunar topographic model CLTM-s01 from Chang’E-1 laser altimeter

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    More than 3 million range measurements from the Chang’E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang’E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25o (~7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, respectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (-1.777, -0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings.

  15. A BP neural network model for sea state recognition using laser altimeter

    Science.gov (United States)

    Shi, Chun-bo; Jia, Xiao-dong; Li, Sheng; Wang, Zhen

    2009-07-01

    A BP neural network method for the recognition of sea state in laser altimeter is presented in this paper. Sea wave is the typical stochastic disturbance factor of laser altimeter effecting on low-altitude defense penetration of the intelligent antiship missiles, the recognition of sea state is studied in order to satisfy the practical needs of flying over the ocean. The BP neural network fed with the feature vector of laser range-measurement presents the analysis of features and outputs the estimation result of sea state. The two most distinguishing features are the mean and the variance of the sea echo, which are extracted from the distance characteristics of sea echo using general theory of statistics. The use of a feedforward network trained with the back-propagation algorithm is also investigated. The BP neural network is trained using sample data set to the neural network, and then the BP neural network trained is tested to recognize the sea state waiting for the classification. The network output shows the recognition accuracy of the model can up to 88%, and the results of tests show that the BP neural network model for the recognition of sea state is feasible and effective.

  16. Waveform analysis of airborne synthetic aperture radar altimeter over Arctic sea ice

    Directory of Open Access Journals (Sweden)

    M. Zygmuntowska

    2013-03-01

    Full Text Available Sea ice thickness is one of the most sensitive variables in the Arctic climate system. In order to quantify changes in sea ice thickness, CryoSat was launched in 2010 carrying a Ku-band Radar Altimeter (SIRAL designed to measure sea ice freeboard with a few centimeters accuracy. The instrument uses the synthetic aperture radar technique providing signals with a resolution of about 300 m along track. In this study, airborne Ku-band radar altimeter data over different sea ice types has been analyzed. A set of parameters has been defined to characterize the difference in strength and width of the returned power waveforms. With a Bayesian based method it is possible to classify about 80% of the waveforms by three parameters: maximum of the returned power echo, the trailing edge width and pulse peakiness. Furthermore, the radar power echo maximum can be used to minimize the rate of false detection of leads compared to the widely used Pulse Peakiness parameter. The possibility to distinguish between different ice types and open water allows to improve the freeboard retrieval and the conversion into sea ice thickness where surface type dependent values for the sea ice density and snow load can be used.

  17. Deriving Sea Surface Salinity and Density Variations From Satellite and Aircraft Microwave Radiometer Measurements: Application to Coastal Plumes Using STARRS

    Science.gov (United States)

    2008-03-01

    Deep Areas ( SALIDA )" under program element 0602435N mid- and low-latitude coastal seas). (NRL-Stennis Space Center contribution NRL/JA/7330-07-7162) and...surface velocities in 3317. the California Current System-Part I: Evaluation of TOPEX altimeter [37] J. Wesson, D. Burrage, J. Miller, W. Teague, and D

  18. Relasphone—Mobile and Participative In Situ Forest Biomass Measurements Supporting Satellite Image Mapping

    Directory of Open Access Journals (Sweden)

    Matthieu Molinier

    2016-10-01

    Full Text Available Due to the high cost of traditional forest plot measurements, the availability of up-to-date in situ forest inventory data has been a bottleneck for remote sensing image analysis in support of the important global forest biomass mapping. Capitalizing on the proliferation of smartphones, citizen science is a promising approach to increase spatial and temporal coverages of in situ forest observations in a cost-effective way. Digital cameras can be used as a relascope device to measure basal area, a forest density variable that is closely related to biomass. In this paper, we present the Relasphone mobile application with extensive accuracy assessment in two mixed forest sites from different biomes. Basal area measurements in Finland (boreal zone were in good agreement with reference forest inventory plot data on pine ( R 2 = 0 . 75 , R M S E = 5 . 33 m 2 /ha, spruce ( R 2 = 0 . 75 , R M S E = 6 . 73 m 2 /ha and birch ( R 2 = 0 . 71 , R M S E = 4 . 98 m 2 /ha, with total relative R M S E ( % = 29 . 66 % . In Durango, Mexico (temperate zone, Relasphone stem volume measurements were best for pine ( R 2 = 0 . 88 , R M S E = 32 . 46 m 3 /ha and total stem volume ( R 2 = 0 . 87 , R M S E = 35 . 21 m 3 /ha. Relasphone data were then successfully utilized as the only reference data in combination with optical satellite images to produce biomass maps. The Relasphone concept has been validated for future use by citizens in other locations.

  19. Feasibility of a Constellation of Miniature Satellites for Performing Measurements of the Magnetic Field of the Earth

    DEFF Research Database (Denmark)

    Thomsen, Michael; Merayo, José M.G.; Brauer, Peter;

    2008-01-01

    This paper studies the requirements for a small constellation of satellites to perform measurements of the magnetic field of the Earth and a payload and boom design for such a mission is discussed. After studying communication, power and mass requirements it is found that it is feasible to develop...

  20. Surface energy balance and actual evapotranspiration of the transboundary Indus Basin estimated from satellite measurements and the ETLook model

    NARCIS (Netherlands)

    Bastiaansen, W.G.M.; Cheema, M.J.M.; Immerzeel, W.W.; Miltenburg, I.J.; Pelgrum, H.

    2012-01-01

    The surface energy fluxes and related evapotranspiration processes across the Indus Basin were estimated for the hydrological year 2007 using satellite measurements. The new ETLook remote sensing model (version 1) infers information on actual Evaporation (E) and actual Transpiration (T) from combine

  1. A New Time Measurement Method Using a High-End Global Navigation Satellite System to Analyze Alpine Skiing

    Science.gov (United States)

    Supej, Matej; Holmberg, Hans-Christer

    2011-01-01

    Accurate time measurement is essential to temporal analysis in sport. This study aimed to (a) develop a new method for time computation from surveyed trajectories using a high-end global navigation satellite system (GNSS), (b) validate its precision by comparing GNSS with photocells, and (c) examine whether gate-to-gate times can provide more…

  2. SAM-2 ground-truth plan: Correlative measurements for the Stratospheric Aerosol Measurement-2 (SAM 2) sensor on the Nimbus G satellite

    Science.gov (United States)

    Russell, P. B.; Mccormick, M. P.; Mcmaster, L. R.; Pepin, T. J.; Chu, W. P.; Swissler, T. J.

    1978-01-01

    The SAM-2 will fly aboard the Nimbus-G satellite for launch in the fall of 1978 and measure stratospheric vertical profiles of aerosol extinction in high latitude bands. The plan gives details of the location and times for the simultaneous satellite/correlative measurements for the nominal launch time, the rationale and choice of the correlative sensors, their characteristics and expected accuracies, and the conversion of their data to extinction profiles. The SAM-2 expected instrument performance and data inversion results are presented. Various atmospheric models representative of polar stratospheric aerosols are used in the SAM-2 and correlative sensor analyses.

  3. Evaluation of the satellite-based Global Flood Detection System for measuring river discharge: influence of local factors

    Directory of Open Access Journals (Sweden)

    B. Revilla-Romero

    2014-07-01

    Full Text Available One of the main challenges for global hydrological modelling is the limited availability of observational data for calibration and model verification. This is particularly the case for real time applications. This problem could potentially be overcome if discharge measurements based on satellite data were sufficiently accurate to substitute for ground-based measurements. The aim of this study is to test the potentials and constraints of the remote sensing signal of the Global Flood Detection System for converting the flood detection signal into river discharge values. The study uses data for 322 river measurement locations in Africa, Asia, Europe, North America and South America. Satellite discharge measurements were calibrated for these sites and a validation analysis with in situ discharge was performed. The locations with very good performance will be used in a future project where satellite discharge measurements are obtained on a daily basis to fill the gaps where real time ground observations are not available. These include several international river locations in Africa: Niger, Volta and Zambezi rivers. Analysis of the potential factors affecting the satellite signal was based on a classification decision tree (Random Forest and showed that mean discharge, climatic region, land cover and upstream catchment area are the dominant variables which determine good or poor performance of the measurement sites. In general terms, higher skill scores were obtained for locations with one or more of the following characteristics: a river width higher than 1 km; a large floodplain area and in flooded forest; with a potential flooded area greater than 40%; sparse vegetation, croplands or grasslands and closed to open and open forest; Leaf Area Index > 2; tropical climatic area; and without hydraulic infrastructures. Also, locations where river ice cover is seasonally present obtained higher skill scores. The work provides guidance on the best

  4. Evolution of stratospheric ozone and water vapour time series studied with satellite measurements

    Directory of Open Access Journals (Sweden)

    A. Jones

    2009-01-01

    Full Text Available The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II, the HALogen Occultation Experiment (HALOE, the Solar BackscatterUltraViolet-2 (SBUV/2 instrument, the Sub-Millimetre Radiometer (SMR, the Optical Spectrograph InfraRed Imager System (OSIRIS, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY. Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO, and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing a weighted all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.7%/decade in the Northern Hemisphere and −7.8%/decade in the Southern Hemisphere. For the period 1997 to 2008 we find that the southern mid-latitudes between 35 and 45 km show the largest ozone recovery (+3.4%/decade compared to other global regions, although the estimated trend model error is of a similar magnitude (+2.1%/decade, at the 95% confidence level. An all instrument average is also constructed from water vapour anomalies during 1984–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (aura/MLS measurements. We report that the decrease in water vapour values after 2001 slows down around 2004 in the lower tropical stratosphere (20–25 km, and has even shown signs of increasing values in upper stratospheric mid

  5. Evolution of stratospheric ozone and water vapour time series studied with satellite measurements

    Directory of Open Access Journals (Sweden)

    A. Jones

    2009-08-01

    Full Text Available The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period of 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II, the HALogen Occultation Experiment (HALOE, the Solar BackscatterUltraViolet-2 (SBUV/2 instrument, the Sub-Millimetre Radiometer (SMR, the Optical Spectrograph InfraRed Imager System (OSIRIS, and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY. Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO, and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing an all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines (at two sigma from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.2%±0.9%/decade in the Northern Hemisphere and −7.1%±0.9%/in the Southern Hemisphere. Furthermore, for the period 1997 to 2008 we find that the same locations show the largest ozone recovery (+1.4% and +0.8%/decade respectively compared to other global regions, although the estimated trend model errors indicate that the trend estimates are not significantly different from a zero trend at the 2 sigma level. An all instrument average is also constructed from water vapour anomalies during 1991–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (Aura/MLS measurements. We report that the decrease in water vapour values after 2001 slows down around 2004–2005 in the lower tropical stratosphere (20–25 km and has even

  6. Characterization of the CTS 12 and 14 GHz communications links - Preliminary measurements and evaluation. [Communications Technology Satellite

    Science.gov (United States)

    Ippolito, L. J.

    1976-01-01

    The Communications Link Characterization Experiment is designed to characterize the radio frequency links of the Communications Technology Satellite. The experiment is twofold: (1) it will study the natural characteristics in the CTS frequency bands (14 GHz uplink, and 12 GHz downlink) including attenuation and signal degradation due primarily to absorption and scattering induced by precipitation, and (2) it will perform environmental measurements for the characterization of man-made, earth-based signals which could interfere with the uplink frequency bands of the satellite.

  7. Global Lithospheric Apparent Susceptibility Distribution Converted from Geomagnetic Models by CHAMP and Swarm Satellite Magnetic Measurements

    Science.gov (United States)

    Du, Jinsong; Chen, Chao; Xiong, Xiong; Li, Yongdong; Liang, Qing

    2016-04-01

    Recently, because of continually accumulated magnetic measurements by CHAMP satellite and Swarm constellation of three satellites and well developed methodologies and techniques of data processing and geomagnetic field modeling etc., global lithospheric magnetic anomaly field models become more and more reliable. This makes the quantitative interpretation of lithospheric magnetic anomaly field possible for having an insight into large-scale magnetic structures in the crust and uppermost mantle. Many different approaches have been utilized to understand the magnetized sources, such as forward, inversion, statistics, correlation analysis, Euler deconvolution, signal transformations etc. Among all quantitative interpretation methods, the directly converting a magnetic anomaly map into a magnetic susceptibility anomaly map proposed by Arkani-Hamed & Strangway (1985) is, we think, the most fast quantitative interpretation tool for global studies. We just call this method AS85 hereinafter for short. Although Gubbins et al. (2011) provided a formula to directly calculate the apparent magnetic vector distribution, the AS85 method introduced constraints of magnetized direction and thus corresponding results are expected to be more robust especially in world-wide continents. Therefore, in this study, we first improved the AS85 method further considering non-axial dipolar inducing field using formulae by Nolte & Siebert (1987), initial model or priori information for starting coefficients in the apparent susceptibility conversion, hidden longest-wavelength components of lithospheric magnetic field and field contaminations from global oceanic remanent magnetization. Then, we used the vertically integrated susceptibility model by Hemant & Maus (2005) and vertically integrated remanent magnetization model by Masterton et al. (2013) to test the validity of our improved method. Subsequently, we applied the conversion method to geomagnetic field models by CHAMP and Swarm satellite

  8. Comparison of global irradiance measurements of the official Spanish radiometric network for 2006 with satellite estimated data

    Directory of Open Access Journals (Sweden)

    J. M. Sancho

    2011-01-01

    Full Text Available The monthly average values of daily global irradiance measured in broadband at 40 stations of the National Radiometric Network of the Spanish Meteorological Agency have been compared with the monthly values of SIS (Surface Incoming Shortwave radiation of the Climate Monitoring-Satellite Application Facility for 2006. It is calculated by the data from the instrument Spinning Enhanced Visible and Infrared Imager of the Meteosat Second Generation satellite and of the Advanced Very High Resolution Radiometer of the NOAA polar satellites. The results show a great similarity between the data from both sources of information, and the discrepancies found are around 5%. The aim of such a comparison is to evaluate the suitability of the use of the SIS data for the elaboration of an atlas of solar irradiance available in Spain.

  9. Long-term groundwater variations in Northwest India from satellite gravity measurements

    Science.gov (United States)

    Chen, Jianli; Li, Jin; Zhang, Zizhan; Ni, Shengnan

    2014-05-01

    Satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) provides quantitative measures of terrestrial water storage (TWS) change at large spatial scales. Combining GRACE-observed TWS changes and model estimates of water storage changes in soil and snow at the surface offers a means for measuring groundwater storage change. In this study, we re-assess long-term groundwater storage variation in the Northwest India (NWI) region using an extended record of GRACE time-variable gravity measurements, and a fully unconstrained global forward modeling method. Our new assessments based on the GRACE release-5 (RL05) gravity solutions indicate that during the 10 year period January 2003 to December 2012, the NWI groundwater depletion remains pronounced, especially during the first 5 years (01/2003-12/2007). The newly estimated depletion rates are ~ 20.4 ± 7.1 Gigatonne (Gt)/yr averaged over the 10 year period, and 29.4 ± 8.4 Gt/yr during the first 5 years. The yearly groundwater storage changes in the NWI region are strongly correlated with yearly precipitation anomalies. In 2009, the driest season of the decade, the groundwater depletion reaches nearly 80 Gt, while in the two relatively wet seasons, 2008 and 2011, the groundwater storages even see net increases of about 24 and 35 Gt, respectively. The estimated mean groundwater depletion rates for the first 5 years are significantly higher than previous assessments. The larger depletion rates may reflect the benefits from improved data quality of GRACE RL05 gravity solutions, and improved data processing method, which can more effectively reduce leakage error in GRACE estimates. Our analysis indicates that the neighboring Punjab Province of Pakistan (especially Northern Punjab) apparently also experiences significant groundwater depletion during the same period, which has partly contributed to the new regional groundwater depletion estimates.

  10. Pulse-to-pulse correlation in CryoSat SAR mode radar altimeter echoes from the sea surface

    Science.gov (United States)

    Smith, W. H.

    2012-12-01

    Serial correlation among successive radar echoes returned from the ocean surface is an important design constraint in satellite altimetry. Walsh [1974, 1982] established the conventional wisdom. Taking the radar footprint to be a uniformly radiating disk, he derived a theoretically expected echo decorrelation time of about 0.5 milliseconds. Following Walsh, ocean altimeters usually employ a pulse repetition frequency (PRF) around 2 kHz, in order to obtain statistically independent echoes at (so it is thought) the maximum possible rate. CryoSat, designed for ranging to ice surfaces, employs a PRF of 18.2 kHz in its SAR mode. CryoSat SAR echo sequences over ocean surfaces can be used to empirically determine the ocean echo decorrelation, and thus to test Walsh's model. Such a test is presented in this paper. The analysis begins by forming the ensemble average of complex cross products of pairs of echoes separated by a time lag L * PRI, where the pulse repetition interval (PRI) is 55 microseconds and the echo lag L runs from 0 to 32. The L = 0 case yields the conventional pulse-limited waveform, which is used to determine the sea state in each ensemble average. The averages of lagged echo cross products reveal the complex coherency, with sampling in both slow time (lag, L), and fast time (range, sampled in waveform gates). Data from many areas and sea states are analyzed, and the results are explained using a simple theory approximating the complex coherency expected from a Gaussian radar pulse. This theory generalizes the classical Brown [1977] waveform model to lagged echo cross products, and generalizes Walsh's work to the case of footprints with non-uniform illumination and diffuse edges. Phase is due to vertical motion of the antenna. Amplitude variations in fast time are due to horizontal motion of the antenna, and are independent of wave height; their functional form confirms Brown's assumption that scattering is independent of azimuth. In slow time, the

  11. Direct Measurements of Laser Communication Point-Ahead Angles from the ARTEMIS Geostationary Satellite Through Clouds

    Science.gov (United States)

    Kuzkov, V.; Sodnik, Z.; Kuzkov, S.

    2017-01-01

    Laser experiments with ARTEMIS geostationary satellite have been performed in partly cloudy weather using the developed system for the telescope. It has been found that the part of the laser beam is observed simultaneously at the points in direction of the velocity vector where the satellite would arrive at when the laser light reaches the telescope. These results agree with the theory of relativity for light aberration in transition from fixed to moving coordinate system.Observation results open the way for research and development of systems to compensate atmospheric turbulence in laser communications between ground stations and satellites through the atmosphere.

  12. Direct Measurements of Laser Communication Point-Ahead Angles from the Artemis Geostationary Satellite Through Clouds

    Directory of Open Access Journals (Sweden)

    Kuzkov, V.P.

    2017-01-01

    Full Text Available Laser experiments with ARTEMIS geostationary satellite have been performed in partly cloudy weather using the developed system for the telescope. It has been found that the part of the laser beam is observed simultaneously at the points in direction of the velocity vector where the satellite would arrive at when the laser light reaches the telescope. These results agree with the theory of relativity for light aberration in transition from fixed to moving coordinate system. Observation results open the way for research and development of systems to compensate atmospheric turbulence in laser communications between ground stations and satellites through the atmosphere.

  13. Communications satellite business ventures - Measuring the impact of technology programmes and related policies

    Science.gov (United States)

    Greenberg, J. S.

    1986-01-01

    An economic evaluation and planning procedure which assesses the effects of various policies on fixed satellite business ventures is described. The procedure is based on a stochastic financial simulation model, the Domsat II, which evaluates spacecraft reliability, market performance, and cost uncertainties. The application of the Domsat II model to the assessment of NASA's ion thrusters for on-orbit propulsion and GaAs solar cell technology is discussed. The effects of insurance rates and the self-insurance option on the financial performance of communication satellite business ventures are investigated. The selection of a transportation system for placing the satellites into GEO is analyzed.

  14. Communications satellite business ventures - Measuring the impact of technology programmes and related policies

    Science.gov (United States)

    Greenberg, J. S.

    1986-01-01

    An economic evaluation and planning procedure which assesses the effects of various policies on fixed satellite business ventures is described. The procedure is based on a stochastic financial simulation model, the Domsat II, which evaluates spacecraft reliability, market performance, and cost uncertainties. The application of the Domsat II model to the assessment of NASA's ion thrusters for on-orbit propulsion and GaAs solar cell technology is discussed. The effects of insurance rates and the self-insurance option on the financial performance of communication satellite business ventures are investigated. The selection of a transportation system for placing the satellites into GEO is analyzed.

  15. All satellites total ozone evaluation in the tropics by comparison with SAOZ-NDACC ground-based measurements

    Science.gov (United States)

    Pommereau, Jean-Pierre; Lerot, Christophe; Van Roozendael, Michel; Goutail, Florence; Pazmino, Andrea; Frihi, Aymen; Bekki, Slimane; Clerbaux, Cathy

    2016-07-01

    All satellites total ozone measurements available from SBUV, OMI-T, OMI-D, OMI-CCI, GOME-CCI, GOME2-CCI, SCIAMACHY-CCI, NPP and IASI, since 2001 until 2015 are compared to those provided by the UV-Vis SAOZ/NDACC spectrometer at the two tropical stations of Reunion Island in the Indian Ocean and Bauru in Southern Brazil. The differences between satellites and SAOZ except IASI do show systematic seasonal variations of 0-3% (0-9 DU) amplitude and sharp negative peaks in Jan-Mar in Reunion Is in the austral summer. Whereas the summer negative peaks seen particularly on IASI, OMI-T, NPP and OMI-CCI at Reunion are shown to correlate with hurricanes and those seen in Brazil with high altitude overshooting convective clouds both not properly removed, ozone minima outside these events are shown to correlate with high altitude volcanic plumes impacting all satellites as well as ground-based total ozone measurements The seasonality of the Sat-SAOZ difference of varying amplitude from 0 to 3% with the satellite is attributed to the satellite retrieval. Surprisingly and though there has been no change in either SAOZ instruments or data analysis processes, the amplitude of the seasonal cycle of the Sat-SAOZ difference reduces in 2012 and drops to less than ± 0.5% (1.5 DU) after 2013 in Reunion Island and less than ±1% in Bauru, reduction for which there is no clear explanation yet. Shown in the presentation will be the demonstration of the impact of hurricanes, high altitude convective clouds and volcanic plumes on satellites total ozone retrievals, followed by a discussion of possible causes of seasonality of Sat-SAOZ amplitude drop after 2012.

  16. Comparative Study of Ground Measured, Satellite-Derived, and Estimated Global Solar Radiation Data in Nigeria

    Directory of Open Access Journals (Sweden)

    Boluwaji M. Olomiyesan

    2016-01-01

    Full Text Available In this study, the performance of three global solar radiation models and the accuracy of global solar radiation data derived from three sources were compared. Twenty-two years (1984–2005 of surface meteorological data consisting of monthly mean daily sunshine duration, minimum and maximum temperatures, and global solar radiation collected from the Nigerian Meteorological (NIMET Agency, Oshodi, Lagos, and the National Aeronautics Space Agency (NASA for three locations in North-Western region of Nigeria were used. A new model incorporating Garcia model into Angstrom-Prescott model was proposed for estimating global radiation in Nigeria. The performances of the models used were determined by using mean bias error (MBE, mean percentage error (MPE, root mean square error (RMSE, and coefficient of determination (R2. Based on the statistical error indices, the proposed model was found to have the best accuracy with the least RMSE values (0.376 for Sokoto, 0.463 for Kaduna, and 0.449 for Kano and highest coefficient of determination, R2 values of 0.922, 0.938, and 0.961 for Sokoto, Kano, and Kaduna, respectively. Also, the comparative study result indicates that the estimated global radiation from the proposed model has a better error range and fits the ground measured data better than the satellite-derived data.

  17. Dose Measurements on the BION-M1 satellite applying passive detector packages

    Science.gov (United States)

    Stradi, Andrea; Berger, Thomas; Kodaira, Satoshi; Kubancak, Jan; Palfalvi, Jozsef K.; Ambrozova, Iva; Tolochek, Raisa; Shurshakov, Vyacheslav; Szabo, Julianna

    A passive detector package was developed in the past years in the Centre for Energy Research, Hungarian Academy of Science to detect cosmic ray particles, to determine their flux and dose. It consists of thermoluminescent detectors (TLD) and plastic solid state nuclear track detectors (SSNTD). In the frame of a scientific co-operation between the Institute for Biomedical Problems (IBMP) fourteen packages were flow within the new BION-M1 satellite program together with biological samples and detector packages from other participants. Two packages were located outside and the rest ones inside the recoverable capsule. Comparing to the previous BION and similar FOTON experiments, (all together 17 successful ones), this flight was a “champion” with the highest altitude (575 km), orbital inclination (64.9°) and flight duration (30 days). The external exposure provided a unique possibility to study not only the elevated level of cosmic rays but also the behavior of the detector packages in extreme circumstances as low temperature and pressure. The paper will summarize the construction of the detector packages, the calibration and evaluation processes, as well as, the linear energy transfer (LET) spectra, the absorbed dose and the mean quality factor. These quantities will be compared taking into consideration their location inside and outside the capsule and to the results of other participants. Also some comparison of results to the previous BION and FOTON flights and contemporary measurements on the ISS will be presented.

  18. High-precision measurement of satellite velocity using the EISCAT radar

    Directory of Open Access Journals (Sweden)

    T. Nygrén

    2012-10-01

    Full Text Available This paper presents a method of measuring the velocity of a hard target using radar pulses reflected from the target flying through the radar beam. The method has two stages. First, the Doppler shifts of the echo pulses are calculated at a high accuracy with an algorithm which largely improves the accuracy given by the Fourier transform. The algorithm also calculates the standard deviations of the Doppler frequencies with Monte Carlo simulation. The second step is to fit the results from a sequence of radar pulses to a velocity model allowing linear variation of the second time derivative of target range. The achieved accuracies are demonstrated using radio pulses reflected by a satellite passing through the beam of the EISCAT UHF radar working at 930-MHz frequency. At high SNR levels, the standard deviations of the frequency from a single pulse reach typically down to 0.2 Hz. The best standard deviations of velocity fit are below 5 mm s−1 while those of the second time derivative of range are below 1 cm s−2.

  19. Satellite quenching timescales in clusters from projected phase space measurements matched to simulated orbits

    CERN Document Server

    Oman, Kyle A

    2016-01-01

    We measure the star formation quenching efficiency and timescale in cluster environments. Our method uses N-body simulations to estimate the probability distribution of possible orbits for a sample of observed SDSS galaxies in and around clusters based on their position and velocity offsets from their host cluster. We study the relationship between their star formation rates and their likely orbital histories via a simple model in which star formation is quenched once a delay time after infall has elapsed. Our orbit library method is designed to isolate the environmental effect on the star formation rate due to a galaxy's present-day host cluster from `pre-processing' in previous group hosts. We find that quenching of satellite galaxies of all stellar masses in our sample ($10^{9}-10^{11.5}\\,{\\rm M}_\\odot$) by massive ($> 10^{13}\\,{\\rm M}_\\odot$) clusters is essentially $100$ per cent efficient. Our fits show that all galaxies quench on their first infall, approximately at or within a Gyr of their first peric...

  20. Satellite gravity measurement monitoring terrestrial water storage change and drought in the continental United States

    Science.gov (United States)

    Yi, Hang; Wen, Lianxing

    2016-01-01

    We use satellite gravity measurements in the Gravity Recovery and Climate Experiment (GRACE) to estimate terrestrial water storage (TWS) change in the continental United States (US) from 2003 to 2012, and establish a GRACE-based Hydrological Drought Index (GHDI) for drought monitoring. GRACE-inferred TWS exhibits opposite patterns between north and south of the continental US from 2003 to 2012, with the equivalent water thickness increasing from -4.0 to 9.4 cm in the north and decreasing from 4.1 to -6.7 cm in the south. The equivalent water thickness also decreases by -5.1 cm in the middle south in 2006. GHDI is established to represent the extent of GRACE-inferred TWS anomaly departing from its historical average and is calibrated to resemble traditional Palmer Hydrological Drought Index (PHDI) in the continental US. GHDI exhibits good correlations with PHDI in the continental US, indicating its feasibility for drought monitoring. Since GHDI is GRACE-based and has minimal dependence of hydrological parameters on the ground, it can be extended for global drought monitoring, particularly useful for the countries that lack sufficient hydrological monitoring infrastructures on the ground.

  1. Ground truth measurements plan for the Multispectral Thermal Imager (MTI) satellite

    Energy Technology Data Exchange (ETDEWEB)

    Garrett, A.J.

    2000-01-03

    Sandia National Laboratories (SNL), Los Alamos National Laboratory (LANL), and the Savannah River Technology Center (SRTC) have developed a diverse group of algorithms for processing and analyzing the data that will be collected by the Multispectral Thermal Imager (MTI) after launch late in 1999. Each of these algorithms must be verified by comparison to independent surface and atmospheric measurements. SRTC has selected 13 sites in the continental U.S. for ground truth data collections. These sites include a high altitude cold water target (Crater Lake), cooling lakes and towers in the warm, humid southeastern US, Department of Energy (DOE) climate research sites, the NASA Stennis satellite Validation and Verification (V and V) target array, waste sites at the Savannah River Site, mining sites in the Four Corners area and dry lake beds in the southwestern US. SRTC has established mutually beneficial relationships with the organizations that manage these sites to make use of their operating and research data and to install additional instrumentation needed for MTI algorithm V and V.

  2. Statistical theory for estimating sampling errors of regional radiation averages based on satellite measurements

    Science.gov (United States)

    Smith, G. L.; Bess, T. D.; Minnis, P.

    1983-01-01

    The processes which determine the weather and climate are driven by the radiation received by the earth and the radiation subsequently emitted. A knowledge of the absorbed and emitted components of radiation is thus fundamental for the study of these processes. In connection with the desire to improve the quality of long-range forecasting, NASA is developing the Earth Radiation Budget Experiment (ERBE), consisting of a three-channel scanning radiometer and a package of nonscanning radiometers. A set of these instruments is to be flown on both the NOAA-F and NOAA-G spacecraft, in sun-synchronous orbits, and on an Earth Radiation Budget Satellite. The purpose of the scanning radiometer is to obtain measurements from which the average reflected solar radiant exitance and the average earth-emitted radiant exitance at a reference level can be established. The estimate of regional average exitance obtained will not exactly equal the true value of the regional average exitance, but will differ due to spatial sampling. A method is presented for evaluating this spatial sampling error.

  3. Determining the Cost Effectiveness of Nano-Satellites

    Science.gov (United States)

    2014-09-01

    Control Network, which has eight Remote Tracking Stations around the globe to communicate with satellites ( Hodges and Woll 2008). The resulting raw...Logan, Utah: AIAA/USU, 2014. Hodges , Len, and Ron Woll. “Air Force Satellite Control Network (AFSCN) Support For Operational Responsive Space (ORS...Warfare Systems Command, 2010. Stacy, Nick . “6U Radar Altimeter Concept.” Paper presented at 6U Cubesat Low Cost Space Missions Workshop. Canberra

  4. Measuring Phased-Array Antenna Beampatterns with High Dynamic Range for the Murchison Widefield Array using 137 MHz ORBCOMM Satellites

    CERN Document Server

    Neben, A R; Hewitt, J N; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Deshpande, A A; Goeke, R; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Lonsdale, C J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Prabu, T; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Tingay, S J; Wayth, R B; Webster, R L; Williams, A; Williams, C L

    2015-01-01

    Detection of the fluctuations in 21 cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137 MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the {\\it in situ} beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering), and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second reference dipole. We achieve beam measurements over 30 dB dynamic range in beam...

  5. Visual analysis as a method of interpretation of the results of satellite ionospheric measurements for exploratory problems

    Science.gov (United States)

    Korneva, N. N.; Mogilevskii, M. M.; Nazarov, V. N.

    2016-05-01

    Traditional methods of time series analysis of satellite ionospheric measurements have some limitations and disadvantages that are mainly associated with the complex nonstationary signal structure. In this paper, the possibility of identifying and studying the temporal characteristics of signals via visual analysis is considered. The proposed approach is illustrated by the example of the visual analysis of wave measurements on the DEMETER microsatellite during its passage over the HAARP facility.

  6. Satellite Imagery Measures of the Astronomically Aligned Megaliths at Nabta Playa

    Science.gov (United States)

    Brophy, T. G.; Rosen, P. A.

    2003-12-01

    Astronomically aligned megalithic structures described in field reports (Wendorf, F. and Malville, J.M., The Megalith Alignments, pp.489-502 in Holocene Settlement of the Egyptian Sahara, Vol.I, 2001.) are identified in newly acquired georectified 60 cm panchromatic satellite imagery of Nabta Playa, southern Egypt. The satellite images allow refinement, often significant, of the reported locations of the megaliths. The report that the primary megalithic alignment was constructed to point to the bright star Sirius, circa 4,820 BC, is reconsidered in light of the satellite data, new field data, radiocarbon, lithostratigraphic and geochronologic data, and the playa sedimentation history. Other possible archaeoastronomical interpretations are considered for that alignment, including the three stars of Orion's Belt circa 6,270 BC that are also implicated in the small Nabta Playa `calendar circle'. Other new features apparent in the satellite imagery are also considered.

  7. CAWRES: A Waveform Retracking Fuzzy Expert System for Optimizing Coastal Sea Levels from Jason-1 and Jason-2 Satellite Altimetry Data

    Directory of Open Access Journals (Sweden)

    Nurul Hazrina Idris

    2017-06-01

    Full Text Available This paper presents the Coastal Altimetry Waveform Retracking Expert System (CAWRES, a novel method to optimise the Jason satellite altimetric sea levels from multiple retracking solutions. CAWRES’ aim is to achieve the highest possible accuracy of coastal sea levels, thus bringing measurement of radar altimetry data closer to the coast. The principles of CAWRES are twofold. The first is to reprocess altimeter waveforms using the optimal retracker, which is sought based on the analysis from a fuzzy expert system. The second is to minimise the relative offset in the retrieved sea levels caused by switching from one retracker to another using a neural network. The innovative system is validated against geoid height and tide gauges in the Great Barrier Reef, Australia for Jason-1 and Jason-2 satellite missions. The regional investigations have demonstrated that the CAWRES can effectively enhance the quality of 20 Hz sea level data and recover up to 16% more data than the standard MLE4 retracker over the tested region. Comparison against tide gauge indicates that the CAWRES sea levels are more reliable than those of Sensor Geophysical Data Records (SGDR products, because the former has a higher (≥0.77 temporal correlation and smaller (≤19 cm root mean square errors. The results demonstrate that the CAWRES can be applied to coastal regions elsewhere as well as other satellite altimeter missions.

  8. Moist processes during MJO events as diagnosed from water isotopic measurements from the IASI satellite

    Science.gov (United States)

    Tuinenburg, O. A.; Risi, C.; Lacour, J. L.; Schneider, M.; Wiegele, A.; Worden, J.; Kurita, N.; Duvel, J. P.; Deutscher, N.; Bony, S.; Coheur, P. F.; Clerbaux, C.

    2015-10-01

    This study aims to investigate some characteristics of the moist processes of the Madden-Julian oscillation (MJO), by making use of joint HDO (or δD) and H2O vapor measurements. The MJO is the main intraseasonal mode of the tropical climate but is hard to properly simulate in global atmospheric models. The joint use of δD-H2O diagnostics yields additional information compared to sole humidity measurements. We use midtropospheric Infrared Atmospheric Sounding Interferometer (IASI) satellite δD and H2O measurements to determine the mean MJO humidity and δD evolution. Moreover, by making use of high temporal resolution data, we determine the variability in this evolution during about eight MJO events from 2010 to 2012 (including those monitored during the DYNAMO (the Dynamics of the MJO), CINDY (Cooperative Indian Ocean Experiment in Y2011) campaign). These data have a higher spatiotemporal coverage than previous δD measurements, enabling the sampling of individual MJO events. IASI measurements over the Indian Ocean confirm earlier findings that the moistening before the precipitation peak of an MJO event is due to water vapor slightly enriched in HDO. There is then a HDO depletion around the precipitation peak that also corresponds to the moister environment. Most interevent variability determined in the current study occurs 5 to 10 days after the MJO event. In 75% of the events, humidity decreases while the atmosphere remains depleted. In a quarter of the events, humidity increases simultaneously with an increase in δD. After this, the advection of relatively dry and enriched air brings back the state to the mean. Over the maritime continent, δD-H2O cycles are more variable on time scales shorter than the MJO and the interevent variability is larger than over the Indian Ocean. The sequence of moistening and drying processes as revealed by the q-δD cycles can be used as a benchmark to evaluate the representation of moist processes in models. This is done here

  9. An Arctic sea ice thickness variability revealed from satellite altimetric measurements

    Institute of Scientific and Technical Information of China (English)

    BI Haibo; HUANG Haijun; SU Qiao; YAN Liwen; LIU Yanxia; XU Xiuli

    2014-01-01

    A modified algorithm taking into account the first year (FY) and multiyear (MY) ice densities is used to derive a sea ice thickness from freeboard measurements acquired by satellite altimetry ICESat (2003-2008). Estimates agree with various independent in situ measurements within 0.21 m. Both the fall and winter campaigns see a dramatic extent retreat of thicker MY ice that survives at least one summer melting sea-son. There were strong seasonal and interannual variabilities with regard to the mean thickness. Seasonal increases of 0.53 m for FY the ice and 0.29 m for the MY ice between the autumn and the winter ICESat campaigns, roughly 4-5 month separation, were found. Interannually, the significant MY ice thickness de-clines over the consecutive four ICESat winter campaigns (2005-2008) leads to a pronounced thickness drop of 0.8 m in MY sea ice zones. No clear trend was identified from the averaged thickness of thinner, FY ice that emerges in autumn and winter and melts in summer. Uncertainty estimates for our calculated thick-ness, caused by the standard deviations of multiple input parameters including freeboard, ice density, snow density, snow depth, show large errors more than 0.5 m in thicker MY ice zones and relatively small stan-dard deviations under 0.5 m elsewhere. Moreover, a sensitivity analysis is implemented to determine the separate impact on the thickness estimate in the dependence of an individual input variable as mentioned above. The results show systematic bias of the estimated ice thickness appears to be mainly caused by the variations of freeboard as well as the ice density whereas the snow density and depth brings about relatively insignificant errors.

  10. Harmonized dataset of ozone profiles from satellite limb and occultation measurements

    Directory of Open Access Journals (Sweden)

    V. F. Sofieva

    2013-06-01

    Full Text Available In this paper, we present a HARMonized dataset of OZone profiles (HARMOZ based on limb and occultation measurements from Envisat (GOMOS, MIPAS and SCIAMACHY, Odin (OSIRIS, SMR and SCISAT (ACE-FTS satellite instruments. These measurements provide high-vertical-resolution ozone profiles covering the altitude range from the upper troposphere up to the mesosphere in years 2001–2012. HARMOZ has been created in the framework of European Space Agency Climate Change Initiative project. The harmonized dataset consists of original retrieved ozone profiles from each instrument, which are screened for invalid data by the instrument teams. While the original ozone profiles are presented in different units and on different vertical grids, the harmonized dataset is given on a common pressure grid in netcdf format. The pressure grid corresponds to vertical sampling of ~ 1 km below 20 km and 2–3 km above 20 km. The vertical range of the ozone profiles is specific for each instrument, thus all information contained in the original data is preserved. Provided altitude and temperature profiles allow the representation of ozone profiles in number density or mixing ratio on a pressure or altitude vertical grids. Geolocation, uncertainty estimates and vertical resolution are provided for each profile. For each instrument, optional parameters, which might be related to the data quality, are also included. For convenience of users, tables of biases between each pair of instruments for each month, as well as bias uncertainties, are provided. These tables characterize the data consistency and can be used in various bias and drift analyses, which are needed, for instance, for combining several datasets to obtain a long-term climate dataset. This user-friendly dataset can be interesting and useful for various analyses and applications, such as data merging, data validation, assimilation and scientific research. Dataset is available at: http

  11. Satellite Geomagnetism

    DEFF Research Database (Denmark)

    Olsen, Nils; Stolle, Claudia

    2012-01-01

    Observations of Earth’s magnetic field from space began more than 50 years ago. A continuous monitoring of the field using low Earth orbit (LEO) satellites, however, started only in 1999, and three satellites have taken highprecision measurements of the geomagnetic field during the past decade...... ability to characterize and understand the many sources that contribute to Earth’s magnetic field. In this review, we summarize investigations of Earth’s interior and environment that have been possible through the analysis of high-precision magnetic field observations taken by LEO satellites........ The unprecedented time-space coverage of their data opened revolutionary new possibilities for monitoring, understanding, and exploring Earth’s magnetic field. In the near future, the three-satellite constellation Swarm will ensure continuity of such measurement and provide enhanced possibilities to improve our...

  12. Sea Temperature Fiducial Reference Measurements for the Validation and Data Gap Bridging of Satellite SST Data Products

    Science.gov (United States)

    Wimmer, Werenfrid

    2016-08-01

    The Infrared Sea surface temperature Autonomous Radiometer (ISAR) was developed to provide reference data for the validation of satellite Sea Surface Temperature at the Skin interface (SSTskin) temperature data products, particularly the Advanced Along Track Scanning Radiometer (AATSR). Since March 2004 ISAR instruments have been deployed nearly continuously on ferries crossing the English Channel and the Bay of Biscay, between Portsmouth (UK) and Bilbao/Santander (Spain). The resulting twelve years of ISAR data, including an individual uncertainty estimate for each SST record, are calibrated with traceability to national standards (National Institute of Standards and Technology, USA (NIST) and National Physical Laboratory, Teddigton, UK (NPL), Fiducial Reference Measurements for satellite derived surface temperature product validation (FRM4STS)). They provide a unique independent in situ reference dataset against which to validate satellite derived products. We present results of the AATSR validation, and show the use of ISAR fiducial reference measurements as a common traceable validation data source for both AATSR and Sea and Land Surface Temperature Radiometer (SLSTR). ISAR data were also used to review performance of the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) Sea Surface Temperature (SST) analysis before and after the demise of ESA Environmental Satellite (Envisat) when AATSR inputs ceased This demonstrates use of the ISAR reference data set for validating the SST climatologies that will bridge the data gap between AATSR and SLSTR.

  13. A technique for measurement of earth station antenna G/T by radio stars and Applications Technology Satellites.

    Science.gov (United States)

    Kochevar, H. J.

    1972-01-01

    A new technique has been developed to accurately measure the G/T of a small aperture antenna using geostationary satellites and the well established radio star method. A large aperture antenna having the capability of accurately measuring its G/T by using a radio star of known power density is used to obtain an accurate G/T to use as a reference. The CNR of both the large and small aperture antennas are then measured using an Applications Technology Satellite (ATS). After normalizing the two C/N ratios to the large antenna system noise temperature the G/T or the gain G of the small aperture antenna can then be determined.

  14. Validation of VIIRS Cloud Base Heights at Night Using Ground and Satellite Measurements over Alaska

    Science.gov (United States)

    NOH, Y. J.; Miller, S. D.; Seaman, C.; Forsythe, J. M.; Brummer, R.; Lindsey, D. T.; Walther, A.; Heidinger, A. K.; Li, Y.

    2016-12-01

    Knowledge of Cloud Base Height (CBH) is critical to describing cloud radiative feedbacks in numerical models and is of practical significance to aviation communities. We have developed a new CBH algorithm constrained by Cloud Top Height (CTH) and Cloud Water Path (CWP) by performing a statistical analysis of A-Train satellite data. It includes an extinction-based method for thin cirrus. In the algorithm, cloud geometric thickness is derived with upstream CTH and CWP input and subtracted from CTH to generate the topmost layer CBH. The CBH information is a key parameter for an improved Cloud Cover/Layers product. The algorithm has been applied to the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi NPP spacecraft. Nighttime cloud optical properties for CWP are retrieved from the nighttime lunar cloud optical and microphysical properties (NLCOMP) algorithm based on a lunar reflectance model for the VIIRS Day/Night Band (DNB) measuring nighttime visible light such as moonlight. The DNB has innovative capabilities to fill the polar winter and nighttime gap of cloud observations which has been an important shortfall from conventional radiometers. The CBH products have been intensively evaluated against CloudSat data. The results showed the new algorithm yields significantly improved performance over the original VIIRS CBH algorithm. However, since CloudSat is now operational during daytime only due to a battery anomaly, the nighttime performance has not been fully assessed. This presentation will show our approach to assess the performance of the CBH algorithm at night. VIIRS CBHs are retrieved over the Alaska region from October 2015 to April 2016 using the Clouds from AVHRR Extended (CLAVR-x) processing system. Ground-based measurements from ceilometer and micropulse lidar at the Atmospheric Radiation Measurement (ARM) site on the North Slope of Alaska are used for the analysis. Local weather conditions are checked using temperature and precipitation

  15. CHASER: An Innovative Satellite Mission Concept to Measure the Effects of Aerosols on Clouds and Climate

    Science.gov (United States)

    Renno, N.; Williams, E.; Rosenfeld, D.; Fischer, D.; Fischer, J.; Kremic, T.; Agrawal, A.; Andreae, M.; Bierbaum, R.; Blakeslee, R.; Boerner, A.; Bowles, N.; Christian, H.; Dunion, J.; Horvath, A.; Huang, X.; Khain, A.; Kinne, S.; Lemos, M.-C.; Penner, J.

    2012-04-01

    The formation of cloud droplets on aerosol particles, technically known as the activation of cloud condensation nuclei (CCN), is the fundamental process driving the interactions of aerosols with clouds and precipitation. Knowledge of these interactions is foundational to our understanding of weather and climate. The Intergovernmental Panel on Climate Change (IPCC) and the Decadal Survey (NRC 2007) indicate that the uncertainty in how clouds adjust to aerosol perturbations dominates the uncertainty in the overall quantification of the radiative forcing attributable to human activities. The Clouds, Hazards, and Aerosols Survey for Earth Researchers (CHASER) mission concept responds to the IPCC and Decadal Survey concerns by studying the activation of CCN and their interactions with clouds and storms. CHASER proposes to revolutionize our understanding of the interactions of aerosols with clouds by making the first global measurements of the fundamental physical entity linking them: activated cloud condensation nuclei. The CHASER mission was conceptualized to measure all quantities necessary for determining the interactions of aerosols with clouds and storms. Measurements by current satellites allow the determination of crude profiles of cloud particle size but not of the activated CCN that seed them. CHASER uses a new technique (Freud et al. 2011; Rosenfeld et al. 2012) and high-heritage instruments to produce the first global maps of activated CCN and the properties of the clouds associated with them. CHASER measures the CCN concentration and cloud thermodynamic forcing simultaneously, allowing their effects to be distinguished. Changes in the behavior of a group of weather systems in which only one of the quantities varies (a partial derivative of the intensity with the desirable quantity) allow the determination of each effect statistically. The high uncertainties of current climate predictions limit their much-needed use in decision-making. CHASER mitigates this

  16. Incorporation of star measurements for the determination of orbit and attitude parameters of a geosynchronous satellite: An iterative application of linear regression

    Science.gov (United States)

    Phillips, D.

    1980-01-01

    Currently on NOAA/NESS's VIRGS system at the World Weather Building star images are being ingested on a daily basis. The image coordinates of the star locations are measured and stored. Subsequently, the information is used to determine the attitude, the misalignment angles between the spin axis and the principal axis of the satellite, and the precession rate and direction. This is done for both the 'East' and 'West' operational geosynchronous satellites. This orientation information is then combined with image measurements of earth based landmarks to determine the orbit of each satellite. The method for determining the orbit is simple. For each landmark measurement one determines a nominal position vector for the satellite by extending a ray from the landmark's position towards the satellite and intersecting the ray with a sphere with center coinciding with the Earth's center and with radius equal to the nominal height for a geosynchronous satellite. The apparent motion of the satellite around the Earth's center is then approximated with a Keplerian model. In turn the variations of the satellite's height, as a function of time found by using this model, are used to redetermine the successive satellite positions by again using the Earth based landmark measurements and intersecting rays from these landmarks with the newly determined spheres. This process is performed iteratively until convergence is achieved. Only three iterations are required.

  17. Tropospheric BrO column densities in the Arctic derived from satellite: retrieval and comparison to ground-based measurements

    Directory of Open Access Journals (Sweden)

    H. Sihler

    2012-11-01

    Full Text Available During polar spring, halogen radicals like bromine monoxide (BrO play an important role in the chemistry of tropospheric ozone destruction. Satellite measurements of the BrO distribution have become a particularly useful tool to investigate this probably natural phenomenon, but the separation of stratospheric and tropospheric partial columns of BrO is challenging. In this study, an algorithm was developed to retrieve tropospheric vertical column densities of BrO from data of high-resolution spectroscopic satellite instruments such as the second Global Ozone Monitoring Experiment (GOME-2. Unlike recently published approaches, the presented algorithm is capable of separating the fraction of BrO in the activated troposphere from the total BrO column solely based on remotely measured properties. The presented algorithm furthermore allows to estimate a realistic measurement error of the tropospheric BrO column. The sensitivity of each satellite pixel to BrO in the boundary layer is quantified using the measured UV radiance and the column density of the oxygen collision complex O4. A comparison of the sensitivities with CALIPSO LIDAR observations demonstrates that clouds shielding near-surface trace-gas columns can be reliably detected even over ice and snow. Retrieved tropospheric BrO columns are then compared to ground-based BrO measurements from two Arctic field campaigns in the Amundsen Gulf and at Barrow in 2008 and 2009, respectively. Our algorithm was found to be capable of retrieving enhanced near-surface BrO during both campaigns in good agreement with ground-based data. Some differences between ground-based and satellite measurements observed at Barrow can be explained by both elevated and shallow surface layers of BrO. The observations strongly suggest that surface release processes are the dominating source of BrO and that boundary layer meteorology influences the vertical distribution.

  18. Plate measurement techniques and reduction methods used by the West German satellite observers, and resulting consequences for the observation

    Science.gov (United States)

    Deker, H.

    1971-01-01

    The West German tracking stations are equipped with ballistic cameras. Plate measurement and plate reduction must therefore follow photogrammetric methods. Approximately 100 star positions and 200 satellite positions are measured on each plate. The mathematical model for spatial rotation of the bundle of rays is extended by including terms for distortion and internal orientation of the camera as well as by providing terms for refraction which are computed for the measured coordinates of the star positions on the plate. From the measuring accuracy of the plate coordinates it follows that the timing accuracy for the exposures has to be about one millisecond, in order to obtain a homogeneous system.

  19. Laser altimeter observations from MESSENGER's first Mercury flyby.

    Science.gov (United States)

    Zuber, Maria T; Smith, David E; Solomon, Sean C; Phillips, Roger J; Peale, Stanton J; Head, James W; Hauck, Steven A; McNutt, Ralph L; Oberst, Jürgen; Neumann, Gregory A; Lemoine, Frank G; Sun, Xiaoli; Barnouin-Jha, Olivier; Harmon, John K

    2008-07-04

    A 3200-kilometers-long profile of Mercury by the Mercury Laser Altimeter on the MESSENGER spacecraft spans approximately 20% of the near-equatorial region of the planet. Topography along the profile is characterized by a 5.2-kilometer dynamic range and 930-meter root-mean-square roughness. At long wavelengths, topography slopes eastward by 0.02 degrees , implying a variation of equatorial shape that is at least partially compensated. Sampled craters on Mercury are shallower than their counterparts on the Moon, at least in part the result of Mercury's higher gravity. Crater floors vary in roughness and slope, implying complex modification over a range of length scales.

  20. Lessons Learned from the Advanced Topographic Laser Altimeter System

    Science.gov (United States)

    Garrison, Matt; Patel, Deepak; Bradshaw, Heather; Robinson, Frank; Neuberger, Dave

    2016-01-01

    The ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS) instrument is an upcoming Earth Science mission focusing on the effects of climate change. The flight instrument passed all environmental testing at GSFC (Goddard Space Flight Center) and is now ready to be shipped to the spacecraft vendor for integration and testing. This presentation walks through the lessons learned from design, hardware, analysis and testing perspective. ATLAS lessons learned include general thermal design, analysis, hardware, and testing issues as well as lessons specific to laser systems, two-phase thermal control, and optical assemblies with precision alignment requirements.

  1. Soil moisture on Polish territory - comparison of satellite and ground-based measurements

    Science.gov (United States)

    Rojek, Edyta; Łukowski, Mateusz; Marczewski, Wojciech; Usowicz, Bogusław

    2014-05-01

    Assessment of water resources due to changing climatic conditions in time and space is still very uncertain. The territory of Poland has a limited resource of waters, occasionally resulting in small agricultural droughts. From the other side intense rainfalls, floods or run-offs, causing soil erosion are observed. Therefore, it is important to predict and prevent of this adverse phenomena. Huge spatial variability of soil moisture does not allow for accurate estimation of its distribution using ground-based measurements. SMOS soil moisture data are quite much inherently consistent in time and space, but their validation is still a challenge for further use in the climate and hydrology studies. This is the motivation for the research: to examine soil moisture from SMOS and ground based stations of the SWEX network held over eastern Poland. The presented results are related to changes of the soil moisture on regional scales for Poland in the period 2010-2013. Some results with SMOS L2 data are extended on continental scales for Europe. Time series from ground and satellite SMOS data sources were compared by regression methods. The region of Poland indicates clearly some genetic spatial distributions in weekly averaged values. In continental scales, the country territory contrasts evidently to Lithuania and in Polesie, and indicates seasonal cycling observed in archives and well known traditional records. The central part of Poland is repeatedly susceptible on droughts with soil moisture values ranging from about 0.02 to 0.20 m3 m-3. SMOS data allows on creating systematic drought data for Poland and watching annual changes, and differences to other drought services kept on national scales for agricultural purposes. We bound that drought susceptibility to the content of sand clay components and the land use there. Lack of rainfall in the late 2011 summer, caused a significant deficit of water in soil moisture content (below 0.05 m3 m-3) throughout the entire country

  2. NODC Standard Product: US Navy Geosat altimeter Crossover Differences (XDRs) for the Geodetic Mission (8 disc set) (NODC Accession 0054498)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains a copy of the NODC eight CD-ROMs product set of the Geosat altimeter Crossover Differences data Records (XDRs) for altimeter data obtained...

  3. On the scale estimation using truncated swath measurements from low Earth orbiting satellites

    Science.gov (United States)

    Liu, Qi

    2013-05-01

    Truncation effect caused by limited swath width of low Earth orbiting (LEO) satellites results in inevitable underestimation of object scale when using pixel-counting methods. A new approach is proposed to obtain more accurate object scale through truncated measurements. The approach is based upon the mean object area fraction (MOAF), which depicts the relative population of object points in a varying-size domain and proves to be less sensitive to truncation effect. The MOAF-equivalent radius (MER) is deduced by comparing the actual MOAF with the standard one inferred from a circle object. Numerical simulations are implemented to demonstrate the MER characteristics. In contrast to area-equivalent radius (AER) that is merely determined by the absolute amount of object points, MER relies on the overall spatial structure of the object. For objects with irregular shapes, the MER value is generally smaller than AER in the absence of truncation. Nevertheless, taking the actual AER as true scale, MER has significantly reduced biases compared to AER once the object is truncated. This advantage can be reinforced when focusing on size statistics of analogous objects, because negative and positive biases associated with various truncation situations coexist in MER, against the uniform negative biases of AER. When applied to MODIS cloud mask data that are restricted in individual granules, MER has consistently larger values than AER for most truncated clouds. Compared with the explicitly problematic estimation from AER due to truncation, MER offers a notable elevation on the estimated cloud size and gets closer to the truth.

  4. Snow thickness retrieval using SMOS satellite data: Comparison with airborne IceBridge and buoy measurements

    Science.gov (United States)

    Maaß, N.; Kaleschke, L.; Tian-Kunze, X.

    2015-12-01

    The passive microwave mission SMOS (Soil Moisture and Ocean Salinity) provides daily coverage of the polar regions and its data have been used to retrieve thin sea ice thickness up to about one meter. In addition, there has been an attempt to retrieve snow thickness over thick Arctic multi-year ice, which is a crucial parameter for the freeboard-based estimation of (thick) sea ice thickness from lidar and radar altimetry. SMOS provides measurements at a frequency of 1.4 GHz (L-band) at horizontal and vertical polarization for a range of incidence angles (0 to 60°). The retrieval of ice or snow parameters from SMOS measurements is based on an emission model that describes the 1.4 GHz brightness temperature of (snow-covered) sea ice as a function of the ice and snow thicknesses and the permittivities of these media, which are mainly determined by ice temperature and salinity and snow density, respectively. In the first attempts to retrieve snow thickness from SMOS data, these parameters were assumed to be constant in the emission model, and the resulting maps were compared with airborne ice and snow thickness measurements taken during NASA's Operation IceBridge mission in spring 2012. The present approach to produce SMOS snow thickness maps is more elaborate. For example, available information on the ice surface temperature from MODIS (MODerate resolution Imaging Spectroradiometer) satellite images or from the IceBridge campaign itself are used, and the ice in the retrieval model is described by temperature and salinity profiles instead of using bulk values. As a first step we have produced (winter/spring) snow thickness maps of the Arctic, from 3-day-averages up to monthly means, using the available SMOS data from 2010 on. Here, we show how our spatial snow thickness distributions compare with IceBridge campaign data in the western Arctic from spring 2011 to 2015. In addition, we show how the temporal evolution of SMOS-retrieved snow thickness compares with snow

  5. From quiescence to unrest: 20 years of satellite geodetic measurements at Santorini volcano, Greece

    Science.gov (United States)

    Parks, Michelle M.; Moore, James D. P.; Papanikolaou, Xanthos; Biggs, Juliet; Mather, Tamsin A.; Pyle, David M.; Raptakis, Costas; Paradissis, Demitris; Hooper, Andrew; Parsons, Barry; Nomikou, Paraskevi

    2015-02-01

    Periods of unrest at caldera-forming volcanic systems characterized by increased rates of seismicity and deformation are well documented. Some can be linked to eventual eruptive activity, while others are followed by a return to quiescence. Here we use a 20 year record of interferometric synthetic aperture radar (InSAR) and GPS measurements from Santorini volcano to further our understanding of geodetic signals at a caldera-forming volcano during the periods of both quiescence and unrest, with measurements spanning a phase of quiescence and slow subsidence (1993-2010), followed by a phase of unrest (January 2011 to April 2012) with caldera-wide inflation and seismicity. Mean InSAR velocity maps from 1993-2010 indicate an average subsidence rate of 6 mm/yr over the southern half of the intracaldera island Nea Kameni. This subsidence can be accounted for by a combination of thermal contraction of the 1866-1870 lava flows and load-induced relaxation of the substrate. For the period of unrest, we use a joint inversion technique to convert InSAR measurements from three separate satellite tracks and GPS observations from 10 continuous sites into a time series of subsurface volume change. The optimal location of the inflating source is consistent with previous studies, situated north of Nea Kameni at a depth of 4 km. However, the time series reveals two distinct pressure pulses. The first pulse corresponds to a volume change (ΔV) within the shallow magma chamber of (11.56 ± 0.14) × 106 m3, and the second pulse has a ΔV of (9.73 ± 0.10) × 106 m3. The relationship between the timing of these pulses and microseismicity observations suggests that these pulses may be driven by two separate batches of magma supplied to a shallow reservoir. We find no evidence suggesting a change in source location between the two pulses. The decline in the rates of volume change at the end of both pulses and the observed lag of the deformation signal behind cumulative seismicity, suggest

  6. Assessing satellite sea surface salinity from ocean color radiometric measurements for coastal hydrodynamic model data assimilation

    Science.gov (United States)

    Vogel, Ronald L.; Brown, Christopher W.

    2016-07-01

    Improving forecasts of salinity from coastal hydrodynamic models would further our predictive capacity of physical, chemical, and biological processes in the coastal ocean. However, salinity is difficult to estimate in coastal and estuarine waters at the temporal and spatial resolution required. Retrieving sea surface salinity (SSS) using satellite ocean color radiometry may provide estimates with reasonable accuracy and resolution for coastal waters that could be assimilated into hydrodynamic models to improve SSS forecasts. We evaluated the applicability of satellite SSS retrievals from two algorithms for potential assimilation into National Oceanic and Atmospheric Administration's Chesapeake Bay Operational Forecast System (CBOFS) hydrodynamic model. Of the two satellite algorithms, a generalized additive model (GAM) outperformed that of an artificial neural network (ANN), with mean bias and root-mean-square error (RMSE) of 1.27 and 3.71 for the GAM and 3.44 and 5.01 for the ANN. However, the RMSE for the SSS predicted by CBOFS (2.47) was lower than that of both satellite algorithms. Given the better precision of the CBOFS model, assimilation of satellite ocean color SSS retrievals will not improve CBOFS forecasts of SSS in Chesapeake Bay. The bias in the GAM SSS retrievals suggests that adding a variable related to precipitation may improve its performance.

  7. Tropospheric BrO column densities in the Arctic from satellite: retrieval and comparison to ground-based measurements

    Directory of Open Access Journals (Sweden)

    H. Sihler

    2012-05-01

    Full Text Available During polar spring, halogen radicals like bromine monoxide (BrO play an important role in the chemistry of tropospheric ozone destruction. Satellite measurements of the BrO-distribution have become a particularly useful tool to investigate this probably natural phenomenon, but the separation of stratospheric and tropospheric partial columns of BrO is challenging. In this study, an algorithm was developed to retrieve tropospheric vertical column densities of BrO from data of high-resolution spectroscopic satellite instruments such as the second Global Ozone Monitoring Experiment (GOME-2. Unlike recently published approaches, the presented algorithm is capable of separating the fraction of BrO in the activated troposphere from the total BrO column solely based on remotely measured properties. The sensitivity of each satellite pixel to BrO in the boundary-layer is quantified using the measured UV-radiance and the column density of the oxygen collision complex O4. A comparison of the sensitivities with CALIPSO LIDAR observations demonstrates that clouds shielding near-surface trace-gas columns can be reliably detected even over ice and snow. Retrieved tropospheric BrO columns are then compared to ground-based BrO measurements from two Arctic field campaigns in the Amundsen Gulf and at Barrow in 2008 and 2009, respectively. Our algorithm was found to be capable of retrieving enhanced near-surface BrO during both campaigns in good agreement to ground-based data. Some differences between ground-based and satellite measurements observed at Barrow can be explained by both, elevated and shallow surface layers of BrO. The observations strongly suggest that surface release processes are the dominating source of BrO and that boundary-layer meteorology influences the vertical distribution.

  8. Nature of the Venus thermosphere derived from satellite drag measurements (solicited paper)

    Science.gov (United States)

    Keating, G.; Theriot, M.; Bougher, S.

    2008-09-01

    From drag measurements obtained by Pioneer Venus and Magellan, the Venus upper atmosphere was discovered to be much colder than Earth's, even though Venus is much closer to the Sun than the Earth. On the dayside, exospheric temperatures are near 300K compared to Earth's of near 1200K [1]. This is thought to result principally from 15 micron excitation of carbon dioxide by atomic oxygen resulting in very strong 15 micron emission to space, cooling off the upper atmosphere [2]. On the nightside the Venus upper atmosphere is near 100K [3], compared to Earth where temperatures are near 900K. The nightside Venus temperatures drop with altitude contrary to a thermosphere where temperatures rise with altitude. As a result, the very cold nightside is called a "cryosphere" rather than a thermosphere. This is the first cryosphere discovered in the solar system [1]. Temperatures sharply drop near the terminator. Apparently, heat is somehow blocked near the terminator from being significantly transported to the nightside [4]. Recently, drag studies were performed on a number of Earth satellites to establish whether the rise of carbon dioxide on Earth was cooling the Earth's thermosphere similar to the dayside of Venus. Keating et al. [5] discovered that a 10 percent drop in density near 350km at solar minimum occurred globally over a period of 20 years with a 10 per cent rise in carbon dioxide. This should result in about a factor of 2 decline in density from 1976 values, by the end of the 21st century brought on by thermospheric cooling. Subsequent studies have confirmed these results. Thus we are beginning to see the cooling of Earth's upper atmosphere apparently from the same process cooling the Venus thermosphere. Fig. 1 VIRA Exospheric Temperatures Atmospheric drag data from the Pioneer Venus Orbiter and Magellan were combined to generate an improved version of the Venus International Reference Atmosphere (VIRA) [6], [7]. A "fountain effect" was discovered where the

  9. 14 CFR 91.411 - Altimeter system and altitude reporting equipment tests and inspections.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Altimeter system and altitude reporting equipment tests and inspections. 91.411 Section 91.411 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... RULES Maintenance, Preventive Maintenance, and Alterations § 91.411 Altimeter system and...

  10. 14 CFR 29.1325 - Static pressure and pressure altimeter systems.

    Science.gov (United States)

    2010-01-01

    ...: Installation § 29.1325 Static pressure and pressure altimeter systems. (a) Each instrument with static air case... between air pressure in the static pressure system and true ambient atmospheric static pressure is not..., when on the alternate static pressure system, differs from the reading of altimeter when on the primary...

  11. Case studies of ERS-1 altimeter data applicating in China Sea

    Institute of Scientific and Technical Information of China (English)

    杨学联; 季晓阳; 黄润恒; 凌铁军

    2001-01-01

    The impact of ERS-1 altimeter significant wave height on analysis of wave field and wave predictions is tested through analysis of selected cases. Application of the altimeter data may modifg initial field and thus 24-hour prediction of significant wave height. However the variations in initial wave field almost make no effect on 48-hour predictions.

  12. Observing the oceanic mesoscale processes with satellite altimetry: the state of the art and outlook

    Science.gov (United States)

    Fu, L.-L.

    2012-04-01

    Satellite altimetry has enabled the study of global oceanic mesoscale variability with increasing accuracy and resolution for the past three decades. The combination of the series of precision missions beginning with TOPEX/Poseidon and the series of missions beginning with ERS-1 has created a data record of sea surface height measurement from at least two simultaneously operating altimeters. This 19-year record has fundamentally expanded our knowledge about the dynamics of ocean circulation, in particular at the mesoscale. The progress made to date from the data record will be briefly reviewed, with emphasis on the remaining open questions. Spectral analysis of the existing altimeter data suggests that the spatial resolution is about 150 km in wavelength in space-time gridded data, and about 70-100 km in along-track data. The unresolved short scales, however, have important roles in the energy balance of ocean dynamics as well as the transport and dissipation of many properties of the ocean such as heat and dissolved chemicals. The prospect of the technique of radar interferometry for making high-resolution wide-swath measurement of sea surface height will be discussed with an update on the development of the SWOT (Surface Water and Ocean Topography) Mission, which is being jointly developed by NASA and CNES with contributions from the Canadian Space Agency. SWOT is being designed for applications in both oceanography and land surface hydrology and setting a standard for the next-generation altimetry missions.

  13. Characterization of Terrestrial Water Dynamics in the Congo Basin Using GRACE and Satellite Radar Altimetry

    Science.gov (United States)

    Lee, Lyongki; Beighley, R. Edward; Alsdorf, Douglas; Jung, Hahn Chul; Shum, C. K.; Duan, Jianbin; Guo, Junyi; Yamazaki, Dai; Andreadis, Konstantinos

    2011-01-01

    The Congo Basin is the world's third largest in size (approximately 3.7 million km^2), and second only to the Amazon River in discharge (approximately 40,200 cms annual average). However, the hydrological dynamics of seasonally flooded wetlands and floodplains remains poorly quantified. Here, we separate the Congo wetland into four 3 degree x 3 degree regions, and use remote sensing measurements (i.e., GRACE, satellite radar altimeter, GPCP, JERS-1, SRTM, and MODIS) to estimate the amounts of water filling and draining from the Congo wetland, and to determine the source of the water. We find that the amount of water annually filling and draining the Congo wetlands is 111 km^3, which is about one-third the size of the water volumes found on the mainstem Amazon floodplain. Based on amplitude comparisons among the water volume changes and timing comparisons among their fluxes, we conclude that the local upland runoff is the main source of the Congo wetland water, not the fluvial process of river-floodplain water exchange as in the Amazon. Our hydraulic analysis using altimeter measurements also supports our conclusion by demonstrating that water surface elevations in the wetlands are consistently higher than the adjacent river water levels. Our research also highlights differences in the hydrology and hydrodynamics between the Congo wetland and the mainstem Amazon floodplain.

  14. Flood modelling with global precipitation measurement (GPM) satellite rainfall data: a case study of Dehradun, Uttarakhand, India

    Science.gov (United States)

    Sai Krishna, V. V.; Dikshit, Anil Kumar; Pandey, Kamal

    2016-05-01

    Urban expansion, water bodies and climate change are inextricably linked with each other. The macro and micro level climate changes are leading to extreme precipitation events which have severe consequences on flooding in urban areas. Flood simulations shall be helpful in demarcation of flooded areas and effective flood planning and preparedness. The temporal availability of satellite rainfall data at varying spatial scale of 0.10 to 0.50 is helpful in near real time flood simulations. The present research aims at analysing stream flow and runoff to monitor flood condition using satellite rainfall data in a hydrologic model. The satellite rainfall data used in the research was NASA's Integrated Multi-satellite Retrievals for Global Precipitation Measurement (IMERG), which is available at 30 minutes temporal resolution. Landsat data was used for mapping the water bodies in the study area. Land use land cover (LULC) data was prepared using Landsat 8 data with maximum likelihood technique that was provided as an input to the HEC-HMS hydrological model. The research was applied to one of the urbanized cities of India, viz. Dehradun, which is the capital of Uttarakhand State. The research helped in identifying the flood vulnerability at the basin level on the basis of the runoff and various socio economic parameters using multi criteria analysis.

  15. The OSIRIS-REx laser altimeter (OLA): Development progress

    Science.gov (United States)

    Daly, M.; Barnouin, O.; Johnson, C.; Bierhaus, E.; Seabrook, J.; Dickinson, C.; Haltigin, T.; Gaudreau, D.; Brunet, C.; Cunningham, G.; Lauretta, D.; Boynton, W.; Beshore, E.

    2014-07-01

    Introduction: The NASA New Frontiers Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission will be the first to sample the B-type asteroid (101955) Bennu [1]. This asteroid is thought to be primitive and carbonaceous, and is probably closely related to CI and/or CM meteorites [2]. The OSIRIS-REx mission hopes to better understand both the physical and geochemical origin and evolution of carbonaceous asteroids through its investigation of Bennu. The OSIRIS-REx spacecraft will launch in September 2016, and arrive at Bennu two years later. The Canadian Space Agency is contributing a scanning lidar system known as the OSIRIS-REx Laser Altimeter (OLA), to the OSIRIS-REx Mission. The OLA instrument is part of suite of onboard instruments [3] including cameras (OCAMS) [4], a visible and near- infrared spectrometer (OVIRS) [5], a thermal emission spectrometer (OTES), and an X-ray imaging spectrometer (REXIS) [6]. OLA Objectives: The OLA instrument has a suite of scientific and mission operations purposes. At a global scale, it will update the shape and mass of Bennu to provide insights on the geological origin and evolution of Bennu, by, for example, further refining constraints on its bulk density. With a carefully undertaken geodesy campaign, OLA-based precision ranges, constraints from radio science (2-way tracking) data and stereo OCAMS images, it will yield broad-scale, quantitative constraints on any internal heterogeneity of Bennu and hence provide further clues to Bennu's origin and subsequent collisional evolution. OLA-derived global asteroid maps of slopes, elevation relative to the asteroid geoid, and vertical roughness will provide quantitative insights on how local-regional surfaces on Bennu evolved subsequent to the formation of the asteroid. In addition, OLA data and derived products support the assessment of the safety and sampleability of potential sample sites. At the sample-site scale, the OLA instrument

  16. Combining Satellite and Ground Magnetic Measurements to Improve Estimates of Electromagnetic Induction Transfer Functions

    Science.gov (United States)

    Balasis, G.; Egbert, G. D.

    2005-12-01

    Electromagnetic (EM) induction studies using satellite and ground-based magnetic data may ultimately provide critical new constraints on the electrical conductivity of Earth's mantle. Unlike ground-based observatories, which leave large areas of the Earth (especially the ocean basins) unsampled, satellites have the potential for nearly complete global coverage. However, because the number of operating satellites is limited, spatially complex (especially non-zonal) external current sources are sampled relatively poorly by satellites at any fixed time. The comparatively much larger number of ground-based observatories provides more complete synoptic sampling of external source structure. By combining data from both satellites and observatories models of external sources can be improved, leading to more reliable global mapping of Earth conductivity. For example, estimates of EM induction transfer functions estimated from night-side CHAMP data have been previously shown to have biases which depend systematically on local time (LT). This pattern of biases suggests that a purely zonal model does not adequately describe magnetospheric sources. As a first step toward improved modeling of spatial complexity in sources, we have applied empirical orthogonal function (EOF) methods to exploratory analysis of night-side observatory data. After subtraction of the predictions of the CM4 comprehensive model, which includes a zonally symmetric storm-time correction based on Dst, we find significant non-axisymmetric, but large scale coherent variability in the mid-latitude night-side observatory residuals. Over the restricted range of local times (18:00-6:00) and latitudes (50°S to 50°N) considered, the dominant spatial mode of variability is reasonably approximated by a q21 quadrupole spherical harmonic. Temporal variability of this leading EOF mode is well correlated with Dst. Strategies for moving beyond this initial exploratory EOF analysis to combine observatory data with

  17. Multi-decadal record of ice dynamics on Daugaard Jensen Gletscher, East Greenland, from satellite imagery and terrestrial measurements

    DEFF Research Database (Denmark)

    Stearns, L.A.; Hamilton, G.S.; Reeh, Niels

    2005-01-01

    The history of ice velocity and calving front position of Daugaard Jensen Gletscher, a large outlet glacier in East Greenland, is reconstructed from field measurements, aerial photography and satellite imagery for the period 1950-2001. The calving terminus of the glacier has remained in approxima......The history of ice velocity and calving front position of Daugaard Jensen Gletscher, a large outlet glacier in East Greenland, is reconstructed from field measurements, aerial photography and satellite imagery for the period 1950-2001. The calving terminus of the glacier has remained...... vs snow accumulation in the interior catchment show that Daugaard Jensen Gletscher has a small negative mass balance. This result is consistent with other mass-balance estimates for the inland region of the glacier....

  18. "Cloud Slicing" : A New Technique to Derive Tropospheric Ozone Profile Information from Satellite Measurements

    Science.gov (United States)

    Ziemke, J. R.; Chandra, S.; Bhartia, P. K.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    A new technique denoted cloud slicing has been developed for estimating tropospheric ozone profile information. All previous methods using satellite data were only capable of estimating the total column of ozone in the troposphere. Cloud slicing takes advantage of the opaque property of water vapor clouds to ultraviolet wavelength radiation. Measurements of above-cloud column ozone from the Nimbus 7 total ozone mapping spectrometer (TOMS) instrument are combined together with Nimbus 7 temperature humidity and infrared radiometer (THIR) cloud-top pressure data to derive ozone column amounts in the upper troposphere. In this study tropical TOMS and THIR data for the period 1979-1984 are analyzed. By combining total tropospheric column ozone (denoted TCO) measurements from the convective cloud differential (CCD) method with 100-400 hPa upper tropospheric column ozone amounts from cloud slicing, it is possible to estimate 400-1000 hPa lower tropospheric column ozone and evaluate its spatial and temporal variability. Results for both the upper and lower tropical troposphere show a year-round zonal wavenumber 1 pattern in column ozone with largest amounts in the Atlantic region (up to approx. 15 DU in the 100-400 hPa pressure band and approx. 25-30 DU in the 400-1000 hPa pressure band). Upper tropospheric ozone derived from cloud slicing shows maximum column amounts in the Atlantic region in the June-August and September-November seasons which is similar to the seasonal variability of CCD derived TCO in the region. For the lower troposphere, largest column amounts occur in the September-November season over Brazil in South America and also southern Africa. Localized increases in the tropics in lower tropospheric ozone are found over the northern region of South America around August and off the west coast of equatorial Africa in the March-May season. Time series analysis for several regions in South America and Africa show an anomalous increase in ozone in the lower

  19. Tropospheric BrO column densities in the Arctic derived from satellite: retrieval and comparison to ground-based measurements

    OpenAIRE

    H Sihler; Platt, U.; Beirle, S.; Marbach, T.; S. Kühl; S. Dörner; Verschaeve, J.; Frieß, U.; Pöhler, D.; Vogel, L.; Sander, R.; T. Wagner

    2012-01-01

    During polar spring, halogen radicals like bromine monoxide (BrO) play an important role in the chemistry of tropospheric ozone destruction. Satellite measurements of the BrO distribution have become a particularly useful tool to investigate this probably natural phenomenon, but the separation of stratospheric and tropospheric partial columns of BrO is challenging. In this study, an algorithm was developed to retrieve tropospheric vertical...

  20. Quantitative evaluation of smoke source strengths and impacts by infusing satellite fire- strength measurements in transport models.

    Science.gov (United States)

    Ichoku, C.; Chin, M.; Diehl, T.; Wooster, M.; Roberts, G.; Giglio, L.

    2007-05-01

    Chemical transport models currently derive their smoke emission sources from counts of fire hot spots detected from satellites, usually with single daily overpasses. However, fires vary in size and strength, with a significant diurnal trend, making the use of pixel counts measured at the same time of day very unreliable for estimating smoke sources. Fortunately, the Moderate-resolution Imaging Spectro-radiometer (MODIS) twin sensors onboard the Terra and Aqua satellites, not only detect fires everywhere at four strategic times of day, but also measure their strength in the form of fire radiative power (FRP) or rate of release of fire radiative energy (FRE). FRP is now also being derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) sensor onboard the geostationary Meteosat-8 platform, which observes Africa and Europe virtually every 15 mins. The SEVIRI measurements show that MODIS 4-times-a-day measurements capture the essence of the fire diurnal cycle. Therefore, MODIS is currently the only satellite data source ideal for estimating daily smoke emissions globally. In a number of recent studies, FRP has been found to be directly proportional to both the rate of biomass consumption and the rate of smoke aerosol emission. Indeed, (1) a combustion factor (Fc), which relates FRE to burned biomass was established, and (2) a FRE-based emission coefficient (Ce), which is a simple coefficient to convert FRP (or FRE) to smoke aerosol emissions was derived for different parts of the world. The results obtained from satellite have been reproduced in the laboratory, and the ingestion of FRP in models is now being tested using the Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. Although MODIS has been in operation since the last 6 years, regrettably, this rare but formidable data resource it provides (FRP) has been left largely unutilized. In this presentation, we will show the preliminary results of using FRP to improve the

  1. Crossover Analysis of CHANG'E-1 Laser Altimeter Data

    Science.gov (United States)

    Hu, W.; Yue, Z.; Di, K.

    2011-08-01

    This paper presents a preliminary result of crossover analysis and adjustment of Chang'E-1(CE-1) Laser Altimeter (LAM) data of the Moon for global and regional mapping applications. During the operation of Chang'E-1 from November 28, 2007 to December 4, 2008, the laser altimeter acquired 1400 orbital profiles with about 9.12 million altimetric points. In our experiment, we derived more than 1.38 million crossovers from 1395 ground tracks covering the entire lunar surface after eliminating outliers of orbits and altimetric points. A method of least-squares crossover adjustment with a series of basis functions of time (trigonometric functions and polynomials) is developed to reconcile the LAM data by minimizing the crossover residuals globally. The normal equations are very large but sparse; therefore they are stored and solved using sparse matrix technique. In a test area (0°N~60°N, 50°W~0°W), the crossover residuals are reduced from 62.1m to 32.8m, and the quality of the DEM generated from the adjusted LAM data is improved accordingly. We will optimize the method for the global adjustment to generate a high precision consistent global DEM, which can be used as absolute control for lunar mapping with orbital images.

  2. The BepiColombo Laser Altimeter BELA: Instrument Description

    Science.gov (United States)

    Seiferlin, K.; Thomas, N.; Spohn, T.; Oberst, J.; Michaelis, H.; Gunderson, K.; Whitby, J. A.

    2005-12-01

    The BepiColombo Laser Altimeter (BELA) is among the instruments that have been selected for flight aboard the MPO of ESA's BepiColombo mission to Mercury. A consortium led by Physikalisches Institut Universitaet Bern, Switzerland) and Institut für Planetenforschung (DLR, Berlin, Germany) will develop the first European laser altimeter for planetary exploration. The instrument follows the classical principle of direct detection of the returned laser light using a 200 mm telescope. The receiver telescope is made of electroformed nickel in order to save mass. The transmitter is based on a longitudinally pumped ND:YAG laser with 50 mJ pulses and about 5 ns pulse duration, operating at 10 Hz. The range finding and pulse detection uses digital filtering of return pulse shapes. Operation is possible on the dayside as well as on the night side of Mercury, but limited to about 1200 km altitude. We will present the instrument concept as well as the set-up of new test, verification and calibration facilities that are required for this type of instrument.

  3. Large-scale Gulf Stream frontal study using GEOS 3 radar altimeter data

    Science.gov (United States)

    Huang, N. E.; Leitao, C. D.; Parra, C. G.

    1978-01-01

    From data obtained by the GEOS 3 radar altimeter, sea surface heights are found by both editing and filtering the raw sea surface height measurements and then referencing these processed data to a 5 foot by 5 foot geoid. Any trend between the processed data and the geoid is removed by subtracting out a linear fit to the residuals in the open ocean. Data from individual passes are further processed by applying a minimum variance technique at the subsatellite crossing points to produce surface topography maps for the 6 months and an overall mean map which reveal important details about the Gulf Stream system. The differences between the monthly mean and the overall mean are calculated for each of the 6 months to show the temporal and spatial changes of the Gulf Stream front and spawned eddies. The standard deviation map is even more informative and shows preferred locations of Gulf Stream meanders.

  4. Geoscience Laser Altimeter System (GLAS) Loop Heat Pipes: An Eventual First Year On-Orbit

    Science.gov (United States)

    Grob, E.; Baker, C.; McCarthy, T.

    2004-01-01

    Goddard Space Flight Center's Geoscience Laser Altimeter System (GLAS) is the sole scientific instrument on the Ice, Cloud and land Elevation Satellite (ICESat) that was launched on January 12, 2003 from Vandenberg AFB. A thermal control architecture based on propylene Loop Heat Pipe technology was developed to provide selectable/stable temperature control for the lasers and other electronics over the widely varying mission environment. Following a nominal LHP and instrument start-up, the mission was interrupted with the failure of the first laser after only 36 days of operation. During the 5-month failure investigation, the two GLAS LHPs and the electronics operated nominally, using heaters as a substitute for the laser heat load. Just prior to resuming the mission, following a seasonal spacecraft yaw maneuver, one of the LHPs deprimed and created a thermal runaway condition that resulted in an emergency shutdown of the GLAS instrument. This paper presents details of the LHP anomaly, the resulting investigation and recovery, along with on-orbit flight data during these critical events.

  5. Validation of ACE-FTS satellite data in the upper troposphere/lower stratosphere (UTLS using non-coincident measurements

    Directory of Open Access Journals (Sweden)

    M. I. Hegglin

    2007-09-01

    Full Text Available CO, O3, and H2O data in the upper troposphere/lower stratosphere (UTLS measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS on Canada's SCISAT-1 satellite are validated using aircraft measurements. In the UTLS, validation of chemical trace gas measurements is a challenging task due to small-scale variability in the tracer fields, strong gradients of the tracers across the tropopause, and scarcity of measurements suitable for validation purposes. Two alternative methods for the validation of the satellite data are introduced, which avoid the usual need for coincident measurements: tracer-tracer correlations, and vertical profiles relative to the tropopause height. Both largely reduce geophysical variability and thereby provide an "instantaneous climatology", allowing measurement comparison with non-coincident data which yields information about the precision, and a statistically meaningful error-assessment of the ACE-FTS satellite data. We found that the ACE-FTS CO and lower stratospheric O3 agree with the aircraft measurements within ±10% and ±5%, respectively. The ACE-FTS O3 in the UT exhibits a high bias of up to 40%. H2O indicates a low bias with relative differences of around 20% in the LS and 40% in the UT, respectively. When taking into account the smearing effect of the vertically limited spacing between measurements of the ACE-FTS instrument, the errors decrease by 5–15% around the tropopause. The ACE-FTS instrument hence offers unprecedented precision and vertical resolution in the UTLS, that will allow a new global perspective on UTLS tracer distributions.

  6. Mean sea surface and geoid gradient comparisons with TOPEX altimeter data

    Science.gov (United States)

    Rapp, Richard H.; Yi, Yuchan; Wang, Yan Ming

    1994-01-01

    Cycles 4 to 54 of TOPEX data have been analyzed through comparisons with the mean sea surface given on the disturbed geophysical data record (GDR). Two inverted barometer correction procedures were considered for the data reduction. One used a constant atmospheric pressure for all data while the one adopted for use, for most computations, introduced a cycle average pressure. The maximum difference between the two estimates was 3.0 cm with a clear annual signal. With the modified correction the TOPEX sea surface was compared to The Ohio State University (OSU) mean sea surface, given on the GDR, to estimate three translations ( delta x = -2.3 cm; delta y = 25.0 cm; delta z = -0.3 cm) and a bias (43.3 cm) between the two surfaces. The only significant translation is delta y which indicates the reference frame of the TOPEX system differs from that used in the OSU mean sea surface system. The bias between the TOPEX mean sea surface and the OSU mean sea surface was used to estimate an equatorial radius of 6,378,136.55 m based on an 18-cm biased estimate of the TOPEX altimeter. Examination of the average difference, by cycle, between the TOPEX sea surface and the OSU mean sea surface suggested a bias change of 3.1 +/- 2.2 mm/yr with a positive sign indicating the average ocean surface is rising or the altimeter measured distance is decreasing. Models were implemented that solved directly for a bias, bias rate annual/semiannual, and tide correction terms. The computations indicated that a simultaneous solution for this bias, bias rate, and annual/semiannual terms gave the most accurate results. Nonsimultaneous solutions led to slightly different bias rate values. The root mean square difference between the TOPEX sea surface and OSU sea surface, after translation and bias correction, was +/- 17 cm for a typical cycle. Some locations were indentified where the difference could reach 2.3 cm and were repeated over several cycles indicating errors in the mean sea surface. Most

  7. Assessment of the global monthly mean surface insolation estimated from satellite measurements using global energy balance archive data

    Science.gov (United States)

    Li, Zhanqing; Whitlock, Charles H.; Charlock, Thomas P.

    1995-01-01

    Global sets of surface radiation budget (SRB) have been obtained from satellite programs. These satellite-based estimates need validation with ground-truth observations. This study validates the estimates of monthly mean surface insolation contained in two satellite-based SRB datasets with the surface measurements made at worldwide radiation stations from the Global Energy Balance Archive (GEBA). One dataset was developed from the Earth Radiation Budget Experiment (ERBE) using the algorithm of Li et al. (ERBE/SRB), and the other from the International Satellite Cloud Climatology Project (ISCCP) using the algorithm of Pinker and Laszlo and that of Staylor (GEWEX/SRB). Since the ERBE/SRB data contain the surface net solar radiation only, the values of surface insolation were derived by making use of the surface albedo data contained GEWEX/SRB product. The resulting surface insolation has a bias error near zero and a root-mean-square error (RMSE) between 8 and 28 W/sq m. The RMSE is mainly associated with poor representation of surface observations within a grid cell. When the number of surface observations are sufficient, the random error is estimated to be about 5 W/sq m with present satellite-based estimates. In addition to demonstrating the strength of the retrieving method, the small random error demonstrates how well the ERBE derives from the monthly mean fluxes at the top of the atmosphere (TOA). A larger scatter is found for the comparison of transmissivity than for that of insolation. Month to month comparison of insolation reveals a weak seasonal trend in bias error with an amplitude of about 3 W/sq m. As for the insolation data from the GEWEX/SRB, larger bias errors of 5-10 W/sq m are evident with stronger seasonal trends and almost identical RMSEs.

  8. Satellite Imagery Measures of the Astronomically Aligned Megalithis at Nabta Playa.

    Science.gov (United States)

    Brophy, T.; Rosen, P.

    The Nabta Playa megalithic complex consists of two types of features: first are the large stones, many of them shaped, placed on or in the sediments of an ancient seasonal lake bed that is now hyper-ariad, second are large sculpted bedrocks features underneath the sediments and associated with the surface megaliths (Wendorf et al. 1992). The astronomically aligned surface megalithic structures described in field reports (Wendorf and Malville, 2001) are identified in recent georectified 60cm panchromatic satellite imagery of Nabta Playa, Southern Egypt. The satellite images allow refinement, often significant of the reported locations of the megaliths (Malville et al 1998, and Wendorf and Malville 2001). The report that a primary megalithic alignment was constructed to point to the bright star Sirius, circa 4820BC, is reconsidered in light of the satellite data, new field, data, radiocarbon, lithostratigraphic and geochronological data, and the playa sedimentation history. Other possible archaeoastronomical interpretations are considered for that alignment, including the three star asterism (of Alnitak, Alniham and Mintaka) circa 6270BC that is also implicated in the small Nebta Playa "calendar circle". Signatures of other possible features apparent in the satellite imagery and a recent field study are also considered. Only a small number of the subsurface bedrock sculptures have been excavated. We recommend the use of ground penetrating imaging methods to illuminate the known but not yet excavated subsurface features. The problem of determining the astronomical intent of the builders of the megalithic structures is approached by considering the complex of features as a whole.

  9. Next-generation satellite gravimetry for measuring mass transport in the Earth system

    NARCIS (Netherlands)

    Teixeira Encarnação, J.

    2015-01-01

    The main objective of the thesis is to identify the optimal set-up for future satellite gravimetry missions aimed at monitoring mass transport in the Earth’s system.The recent variability of climatic patterns, the spread of arid regions and associ- ated changes in the hydrological cycle, and vigorou

  10. Validity of satellite measurements used for the monitoring of UV radiation risk on health

    Directory of Open Access Journals (Sweden)

    F. Jégou

    2011-06-01

    Full Text Available In order to test the validity of ultraviolet index (UVI satellite products and UVI model simulations for general public information, intercomparison involving three satellite instruments (SCIAMACHY, OMI and GOME-2, the Chemistry and Transport Model, Modélisation de la Chimie Atmosphérique Grande Echelle (MOCAGE, and ground-based instruments was performed in 2008 and 2009. The intercomparison highlighted a systematic high bias of ~1 UVI in the OMI clear-sky products compared to the SCIAMACHY and TUV model clear-sky products. The OMI and GOME-2 all-sky products are close to the ground-based observations with a low 6 % positive bias, comparable to the results found during the satellite validation campaigns. This result shows that OMI and GOME-2 all-sky products are well appropriate to evaluate the UV-risk on health. The study has pointed out the difficulty to take into account either in the retrieval algorithms or in the models, the large spatial and temporal cloud modification effect on UV radiation. This factor is crucial to provide good quality UV information. OMI and GOME-2 show a realistic UV variability as a function of the cloud cover. Nevertheless these satellite products do not sufficiently take into account the radiation reflected by clouds. MOCAGE numerical forecasts show good results during periods with low cloud covers, but are actually not adequate for overcast conditions; this is why Météo-France currently uses human-expertised cloudiness (rather than direct outputs from Numerical Prediction Models together with MOCAGE clear-sky UV indices for its operational forecasts. From now on, the UV monitoring could be done using free satellite products (OMI, GOME-2 and operational forecast for general public by using modelling, as long as cloud forecasts and the parametrisation of the impact of cloudiness on UV radiation are adequate.

  11. Method for validating cloud mask obtained from satellite measurements using ground-based sky camera.

    Science.gov (United States)

    Letu, Husi; Nagao, Takashi M; Nakajima, Takashi Y; Matsumae, Yoshiaki

    2014-11-01

    Error propagation in Earth's atmospheric, oceanic, and land surface parameters of the satellite products caused by misclassification of the cloud mask is a critical issue for improving the accuracy of satellite products. Thus, characterizing the accuracy of the cloud mask is important for investigating the influence of the cloud mask on satellite products. In this study, we proposed a method for validating multiwavelength satellite data derived cloud masks using ground-based sky camera (GSC) data. First, a cloud cover algorithm for GSC data has been developed using sky index and bright index. Then, Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data derived cloud masks by two cloud-screening algorithms (i.e., MOD35 and CLAUDIA) were validated using the GSC cloud mask. The results indicate that MOD35 is likely to classify ambiguous pixels as "cloudy," whereas CLAUDIA is likely to classify them as "clear." Furthermore, the influence of error propagations caused by misclassification of the MOD35 and CLAUDIA cloud masks on MODIS derived reflectance, brightness temperature, and normalized difference vegetation index (NDVI) in clear and cloudy pixels was investigated using sky camera data. It shows that the influence of the error propagation by the MOD35 cloud mask on the MODIS derived monthly mean reflectance, brightness temperature, and NDVI for clear pixels is significantly smaller than for the CLAUDIA cloud mask; the influence of the error propagation by the CLAUDIA cloud mask on MODIS derived monthly mean cloud products for cloudy pixels is significantly smaller than that by the MOD35 cloud mask.

  12. Evapotranspiration Estimation over Yangtze River Basin from GRACE satellite measurement and in situ data

    Science.gov (United States)

    Li, Qiong; Luo, Zhicai; Zhong, Bo; Wang, Haihong; Zhou, Zebing

    2016-04-01

    As the critical component of hydrologic cycle, evapotranspiration (ET) plays an important role in global water exchanges and energy flow across the hydrosphere, atmosphere and biosphere. Influenced by the Asian monsoon, the Yangtze River Basin (YRB) suffer from the several severe floods and droughts over the last decades due to the significant difference between temporal and spatial distribution terrestrial water storages. As an indispensable part, it is practically important to assessment ET in the YRB accompany with increased population and rapid economic and agriculture development. Average ET over the YRB is computed as the residual of terrestrial water budget using the Gravity Recovery and Climate Experiment (GRACE) satellite-based measurements and the ground-based observations. The GRACE-based ET were well coincidence with the ET from MODIS, with the correlation coefficient of 0.853, and the correlation coefficient is 0.696 while comparing with the ET ground-based observation. The mean monthly average of ET from these various estimates is 56.9 mm/month over the whole YRB, and peak between June and August. Monthly variations of ET reach a maximum in Wujiang with 69.11 mm/month and a minimum in Jinshajiang with 39.01 mm/month. Based on the correlation between ET and independent estimates of near-surface temperature and soil moisture, it is showed that as the temperature increased, the ET of the seven sub-catchment were rising except for the Poyang Lake and Donting Lake. And we also can infer that the midstream of YRB is significant correlated with ESON especially in the Hanjiang basin. The Surface Humidity Index over the YRB was gradually decreased and its variations in each sub-catchment showed a significant decreasing trend in Jinshajiang and Mingjiang. This research has important potential for use in large-scale water budget assessments and intercomparison studies. Acknowledgements: This research is supported by the National Natural Science Foundation of

  13. Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

    Directory of Open Access Journals (Sweden)

    S. Schweitzer

    2011-10-01

    Full Text Available LEO-LEO infrared-laser occultation (LIO is a new occultation technique between Low Earth Orbit (LEO satellites, which applies signals in the short wave infrared spectral range (SWIR within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO method that enables to retrieve thermodynamic profiles (pressure, temperature, humidity and altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss these influences, assessing effects from refraction, trace species absorption, aerosol extinction and Rayleigh scattering in detail, and addressing clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation as well. We show that the influence of refractive defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle with a close frequency spacing of LIO absorption and reference signals within 0.5%. The influences of Rayleigh scattering and terrestrial thermal radiation are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions, but this influence can be made negligible by a close time spacing (within 5 ms of interleaved laser-pulse and background signals. Cloud extinction loss generally blocks SWIR signals, except very thin or sub-visible cirrus clouds, which can be addressed by retrieving a cloud layering profile and exploiting it in the trace species retrieval. Wind can have a small influence on the trace species absorption, which can be made negligible by using a simultaneously retrieved or a moderately accurate background wind speed profile. We

  14. Comparative Analysis of Satellite Measurements Calculation Results Using the Postprocessing Services: Asg-Eupos (Poland), Apps (USA) and CSRS (Canada)

    Science.gov (United States)

    Mika, Monika; Kudach, Jakub

    2014-06-01

    The publication has a cognitive research character. It presents a comparative analysis of free Internet services in Poland and abroad, used to adjust the data obtained using satellite measurement techniques. The main aim of this work is to describe and compare free tools for satellite data processing and to examine them for possible use in the surveying works in Poland. Among the many European and global services three of them dedicated to satellite measurements were selected: ASG-EUPOS (Poland), APPS (USA) and CSRS (Canada). The publication contains the results of calculations using these systems. Calculations were based on RINEX files obtained via postprocessing service (ASG-EUPOS network) POZGEO D for 12 reference stations in the South Poland. In order to examine differences in results between the ASG-EUPOS, APPS and CSRS the transformation points coordinate to a single coordinate system ETRF 2000 (in force in Poland) was made. Studies have shown the possibility of the calculation in Poland (in postprocessing mode) using the analyzed applications with global coverage.

  15. Investigating the error budget of tropical rainfall accumulations derived from combined passive microwave and infrared satellite measurements

    Science.gov (United States)

    Roca, R.; Chambon, P.; jobard, I.; Viltard, N.

    2012-04-01

    Measuring rainfall requires a high density of observations, which, over the whole tropical elt, can only be provided from space. For several decades, the availability of satellite observations has greatly increased; thanks to newly implemented missions like the Megha-Tropiques mission and the forthcoming GPM constellation, measurements from space become available from a set of observing systems. In this work, we focus on rainfall error estimations at the 1 °/1-day accumulated scale, key scale of meteorological and hydrological studies. A novel methodology for quantitative precipitation estimation is introduced; its name is TAPEER (Tropical Amount of Precipitation with an Estimate of ERrors) and it aims to provide 1 °/1-day rain accumulations and associated errors over the whole Tropical belt. This approach is based on a combination of infrared imagery from a fleet of geostationary satellites and passive microwave derived rain rates from a constellation of low earth orbiting satellites. A three-stage disaggregation of error into sampling, algorithmic and calibration errors is performed; the magnitudes of the three terms are then estimated separately. A dedicated error model is used to evaluate sampling errors and a forward error propagation approach is used for an estimation of algorithmic and calibration errors. One of the main findings in this study is the large contribution of the sampling errors and the algorithmic errors of BRAIN on medium rain rates (2 mm h-1 to 10 mm h-1) in the total error budget.

  16. Multi-decadal record of ice dynamics on Daugaard Jensen Gletscher, East Greenland, from satellite imagery and terrestrial measurements

    DEFF Research Database (Denmark)

    Stearns, L.A.; Hamilton, G.S.; Reeh, Niels

    2005-01-01

    The history of ice velocity and calving front position of Daugaard Jensen Gletscher, a large outlet glacier in East Greenland, is reconstructed from field measurements, aerial photography and satellite imagery for the period 1950-2001. The calving terminus of the glacier has remained...... in approximately the same position over the past similar to 50 years. There is no evidence of a change in ice motion between 1968 and 2001, based on a comparison of velocities derived from terrestrial surveying and feature tracking using sequential satellite images. Estimates of flux near the entrance to the fjord...... vs snow accumulation in the interior catchment show that Daugaard Jensen Gletscher has a small negative mass balance. This result is consistent with other mass-balance estimates for the inland region of the glacier....

  17. Validation of INSAT-3D sounder data with in situ measurements and other similar satellite observations over India

    Science.gov (United States)

    Venkat Ratnam, Madineni; Hemanth Kumar, Alladi; Jayaraman, Achuthan

    2016-11-01

    To date, several satellites measurements are available which can provide profiles of temperature and water vapour with reasonable accuracies. However, the temporal resolution has remained poor, particularly over the tropics, as most of them are polar orbiting. At this juncture, the launch of INSAT-3D (Indian National Satellite System) by the Indian Space Research Organization (ISRO) on 26 July 2013 carrying a multi-spectral imager covering visible to long-wave infrared made it possible to obtain profiles of temperature and water vapour over India with higher temporal and vertical resolutions and altitude coverage, besides other parameters. The initial validation of INSAT-3D data is made with the high temporal (3 h) resolution radiosonde observations launched over Gadanki (13.5° N, 79.2° E) during a special campaign and routine evening soundings obtained at 12:00 UTC (17:30 LT). We also compared INSAT-3D data with the radiosonde observations obtained from 34 India Meteorological Department stations. Comparisons were also made over India with data from other satellites like AIRS, MLS and SAPHIR and from ERA-Interim and NCEP reanalysis data sets. INSAT-3D is able to show better coverage over India with high spatial and temporal resolutions as expected. Good correlation in temperature between INSAT-3D and in situ measurements is noticed except in the upper tropospheric and lower stratospheric regions (positive bias of 2-3 K). There is a mean dry bias of 20-30 % in the water vapour mixing ratio. Similar biases are noticed when compared to other satellites and reanalysis data sets. INSAT-3D shows a large positive bias in temperature above 25° N in the lower troposphere. Thus, caution is advised when using these data for tropospheric studies. Finally it is concluded that temperature data from INSAT-3D are of high quality and can be directly assimilated for better forecasts over India.

  18. Comparison of horizontal winds from the LIMS satellite instrument with rocket measurements

    Science.gov (United States)

    Smith, A. K.; Bailey, P. L.

    1985-01-01

    Statistical results are given for a comparison between horizontal geostrophic winds computed from satellite height data and all available in situ rocket wind soundings during a 7-month period. The satellite data are the daily mapped fields from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument, which extend from 100 to 0.1 mbar. Results indicate that in both the tropics and the extratropical Northern Hemisphere, the average zonal and meridional wind speeds agree to within 2-4 m/s throughout the stratosphere. The rms differences are much larger, with values of 5-10 m/s in the lower stratosphere, increasing to 20-40 m/s in the lower mesosphere. Time series show that LIMS and rocketsonde zonal wind speeds show coherent variations with temporal periods of 1-2 weeks and more, and both exhibit irregular variations on time scales of less than one week.

  19. Satellite measurement of sulfur dioxide from the Redoubt eruptions of 1989 1990

    Science.gov (United States)

    Schnetzler, C. C.; Doiron, S. D.; Walter, L. S.; Krueger, A. J.

    1994-08-01

    The mass of SO 2 emitted by the 16 major explosive eruptions of Redoubt Volcano between December 1989 and April 1990 have been examined by the Total Ozone Mapping Spectrometer (TOMS) carried on the Nimbus 7 satellite. Because of low light levels during the winter months, TOMS could not detect SO 2 at high northern latitudes. Thus, the major eruptions from December through February could not be monitored unless winds brought the clouds to latitudes lower than about 58°N. Only two SO 2 clouds were observed in the satellite data — an approximately 100-kiloton (kt) cloud on December 16 over Nevada and eastern California, and a 10-kt cloud on March 9 directly over the volcano. We speculate that the major eruption on December 15 at 1015 hour produced the 100-kt cloud seen on December 16, and the mass of SO 2 injected into the atmosphere at that time was 175 ± 50 kt.

  20. Performance Measurements of the Submillimeter Wave Astronomy Satellite (SWAS) Solar Array Deployment System

    OpenAIRE

    Sneiderman, Gary

    1995-01-01

    This paper discusses some unique features of the solar array deployment system used on the Submillimeter Wave Astronomy Satellite (SWAS). The mechanism system is highly optimized, incorporates no single-use components, and is fully testable in a one-"g" environment. A single High Output Paraffin (HOP) linear actuator drives the mechanisms used to deploy and lock each wing of solar array panels. The solar arrays open slowly, requiring only enough force to overcome inefficiencies and friction. ...

  1. Search for Best Astronomical Observatory Sites in the MENA Region using Satellite Measurements

    Science.gov (United States)

    Abdelaziz, G.; Guebsi, R.; Guessoum, N.; Flamant, C.

    2017-06-01

    We perform a systematic search for astronomical observatory sites in the MENA (Middle-East and North Africa) region using space-based data for all the relevant factors, i.e. altitude (DEM), cloud fraction (CF), light pollution (NTL), precipitable water vapor (PWV), aerosol optical depth (AOD), relative humidity (RH), wind speed (WS), Richardson Number (RN), and diurnal temperature range (DTR). We look for the best locations overall even where altitudes are low (the threshold that we normally consider being 1,500 m) or where the combination of the afore-mentioned determining factors had previously excluded all locations in a given country. In this aim, we use the rich data that Earth-observing satellites provide, e.g. the Terra and Aqua multi-national NASA research satellites, with their MODIS (Moderate Resolution Imaging Spectroradiometer) and AIRS (Atmospheric Infrared Sounder) instruments, the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS), and other products from climate diagnostics archives (e.g. MERRA). We present preliminary results on the best locations for the region.

  2. The first estimates of global nucleation mode aerosol concentrations based on satellite measurements

    Directory of Open Access Journals (Sweden)

    M. Kulmala

    2011-11-01

    Full Text Available Atmospheric aerosols play a key role in the Earth's climate system by scattering and absorbing solar radiation and by acting as cloud condensation nuclei. Satellites are increasingly used to obtain information on properties of aerosol particles with a diameter larger than about 100 nm. However, new aerosol particles formed by nucleation are initially much smaller and grow into the optically active size range on time scales of many hours. In this paper we derive proxies, based on process understanding and ground-based observations, to determine the concentrations of these new particles and their spatial distribution using satellite data. The results are applied to provide seasonal variation of nucleation mode concentration. The proxies describe the concentration of nucleation mode particles over continents. The source rates are related to both regional nucleation and nucleation associated with more restricted sources. The global pattern of nucleation mode particle number concentration predicted by satellite data using our proxies is compared qualitatively against both observations and global model simulations.

  3. The Performance of Altimeter Waveform Retrackers at Lake Baikal

    Directory of Open Access Journals (Sweden)

    Yuchan Yi

    2013-01-01

    Full Text Available At each of five fixed locations along the ground tracks of JASON-1 and ENVISAT, a repeat-track analysis of 1-Hz sea surface height (SSH data has been conducted to assess the performance of waveform retrackers over Lake Baikal in Siberia, Russia. This simple analysis of time series at each point location is needed to minimize the effect of the range correction artifacts in current Geophysical Data Record (GDR data products of radar altimeters in in-land areas. Using the retracked data available in the GDRs as the baseline, two retrackers are evaluated in terms of the number of valid data points produced and the degree of agreement with in-situ data of water level record. The threshold retrackers that are based on the amplitude of the robust OCOG algorithm (Offset Center of Gravity are found to perform the best in Lake Baikal.

  4. Transport of NOx in East Asia identified by satellite and in situ measurements and Lagrangian particle dispersion model simulations

    Science.gov (United States)

    Lee, H.-J.; Kim, S.-W.; Brioude, J.; Cooper, O. R.; Frost, G. J.; Kim, C.-H.; Park, R. J.; Trainer, M.; Woo, J.-H.

    2014-03-01

    Nitrogen dioxide (NO2) columns observed from space have been useful in detecting the increase of nitrogen oxides (NOx) emissions in East Asia, particularly China, coinciding with rapid economic growth during the past several decades. NO2 columns retrieved above a particular location reflect a combination of local NOx emissions and transported NOx from upwind sources. In this study, we demonstrate the transport of NOx emitted in East Asia using satellite and surface in situ measurements and Lagrangian particle dispersion model simulations. Enhanced satellite NO2 columns in the Yellow Sea (between China and South Korea) and the East Sea (between South Korea and Japan), and different seasonal variations of NO2 in China, North and South Korea, and Japan, suggest the importance of NOx transport in understanding the local NOx budget. Lagrangian transport model simulations with tracers of different chemical lifetimes identify source-receptor relationships that explain high NO2 over the oceans and springtime peaks in Korea and Japan, with China being the most likely source region. Our results have important implications for studies using satellite NO2 retrievals to derive NOx emissions at local scales in regions adjacent to large sources, such as in East Asia, Europe, and the Eastern U.S.

  5. Development of the Laser Altimeter (LIDAR) for Hayabusa2

    Science.gov (United States)

    Mizuno, T.; Kase, T.; Shiina, T.; Mita, M.; Namiki, N.; Senshu, H.; Yamada, R.; Noda, H.; Kunimori, H.; Hirata, N.; Terui, F.; Mimasu, Y.

    2016-02-01

    Hayabusa2 was launched on 3 December 2014 on an H-IIA launch vehicle from the Tanegashima Space Center, and is, at the time of writing, cruising toward asteroid 162137 Ryugu ( 1999JU3). After reaching the asteroid, it will stay for about 1.5 years to observe the asteroid and collect surface material samples. The light detection and ranging (LIDAR) laser altimeter on Hayabusa2 has a wide dynamic range, from 25 km to 30 m, because the LIDAR is used as a navigation sensor for rendezvous, approach, and touchdown procedures. Since it was designed for use in planetary explorers, its weight is a low 3.5 kg. The LIDAR can serve not only as a navigation sensor, but also as observation equipment for estimating the asteroid's topography, gravity and surface reflectivity (albedo). Since Hayabusa2 had a development schedule of just three years from the start of the project to launch, minimizing development time was a particular concern. A key to shortening the development period of Hayabusa2's LIDAR system was heritage technology from Hayabusa's LIDAR and the SELENE lunar explorer's LALT laser altimeter. Given that the main role of Hayabusa2's LIDAR is to serve as a navigation sensor, we discuss its development from an engineering viewpoint. However, detailed information about instrument development and test results is also important for scientific analysis of LIDAR data and for future laser altimetry in lunar and planetary exploration. Here we describe lessons learned from the Hayabusa LIDAR, as well as Hayabusa2's hardware, new technologies and system designs based on it, and flight model evaluation results. The monolithic laser used in the laser module is a characteristic technology of this LIDAR. It was developed to solve issues with low-temperature storage that were problematic when developing the LIDAR system for the first Hayabusa mission. The new module not only solves such problems but also improves reliability and miniaturization by reducing the number of parts.

  6. A possible experiment with two counter-orbiting drag-free satellites to obtain a new test of Einstein's general theory of relativity and improved measurements in geodesy

    Science.gov (United States)

    Van Patten, R. A.; Everitt, C. W. F.

    1976-01-01

    In 1918, Lense and Thirring calculated that a moon in orbit around a massive rotating planet would experience a nodal dragging effect due to general relativity. We describe an experiment to measure this effect by means of two counter-orbiting drag-free satellites in polar orbit about the earth. For a 2-1/2 year experiment, the measurement should approach an accuracy of 1%. An independent measurement of the geodetic precession of the orbit plane due to the motion about the sun may also be possible to about 10% accuracy. In addition to precision tracking data from existing ground stations, satellite-to-satellite Doppler data are taken at points of passing near the poles to yield an accurate measurement of the separation distance between the two satellites. New geophysical information on both earth harmonics and tidal effects is inherent in this polar ranging data.

  7. Atmospheric influences on infrared-laser signals used for occultation measurements between Low Earth Orbit satellites

    Directory of Open Access Journals (Sweden)

    S. Schweitzer

    2011-05-01

    Full Text Available LEO-LEO infrared-laser occultation (LIO is a new occultation technique between Low Earth Orbit (LEO satellites, which applies signals in the short wave infrared spectral range (SWIR within 2 μm to 2.5 μm. It is part of the LEO-LEO microwave and infrared-laser occultation (LMIO method, recently introduced by Kirchengast and Schweitzer (2011, that enables to retrieve thermodynamic profiles (pressure, temperature, humidity and accurate altitude levels from microwave signals and profiles of greenhouse gases and further variables such as line-of-sight wind speed from simultaneously measured LIO signals. For enabling trace species retrieval based on differential transmission, the LIO signals are spectrally located as pairs, one in the centre of a suitable absorption line of a target species (absorption signal and one close by but outside of any absorption lines (reference signal. Due to the novelty of the LMIO method, detailed knowledge of atmospheric influences on LIO signals and of their suitability for accurate trace species retrieval did not yet exist. Here we discuss the atmospheric influences on the transmission and differential transmission of LIO signals. Refraction effects, trace species absorption (by target species, and cross-sensitivity to foreign species, aerosol extinction and Rayleigh scattering are studied in detail. The influences of clouds, turbulence, wind, scattered solar radiation and terrestrial thermal radiation are discussed as well. We show that the influence of defocusing, foreign species absorption, aerosols and turbulence is observable, but can be rendered small to negligible by use of the differential transmission principle and by a design with close frequency spacing of absorption and reference signals within 0.5 %. The influences of Rayleigh scattering and thermal radiation on the received signal intensities are found negligible. Cloud-scattered solar radiation can be observable under bright-day conditions but this

  8. Altimeter and Argo float data assimilation in the Black Sea

    Science.gov (United States)

    Grayek, Sebastian; Stanev, Emil; Schulz-Stellenfleth, Johannes

    2010-05-01

    We analyse the thermo-haline characteristics in the Black Sea during the period 2002-2009 derived from numerical model simulations assimilating different observation data with the aim to improve the model skills. The Nucleus of European Modelling of the Ocean (NEMO) framework is used. In the experiment OI-1 we assimilate satellite altimetry and AVHRR data. In the experiment OI-2 we add also in-situ measurements from ARGO floats. Data assimilation uses the SESAM code and an optimal interpolation approach based on the static covariance matrix derived from the preliminary free model run, which converters the observations into basin temperature and salinity fields. Main attention in the analysis of simulations is been paid to the dominating characteristics of physical fields at seasonal and inter-annual time scales. Empirical orthogonal function (EOF) analysis of steric heights from simulations and their consistence with the ones from satellite altimetry is used to analyse the general characteristics in the thermo-haline signals. Results indicate that the free model run reproduces reasonably well the seasonal variability of Rim Current and the cold intermediate water mass formation. The assimilation of remote sensing observations only (OI-1) improves significantly the dynamics of steric heights, in particular as seen in the analysis of higher degree EOF-modes. However, in this experiment the simulation of profiles needs an improvement. This improvement is ensured by the assimilation of ARGO profiles in OI-2. However, because in the Black Sea ARGO measurements are sparse the benefit of their assimilation has to be considered carefully and is done by an objective analysis on model skills in the entire basin.

  9. Joint Polar Satellite System (JPSS) Common Ground System (CGS) Technical Performance Measures of the Block 2 Architecture

    Science.gov (United States)

    Grant, K. D.; Panas, M.

    2016-12-01

    NOAA and NASA are jointly acquiring the next-generation civilian weather satellite system: the Joint Polar Satellite System (JPSS). JPSS replaced the afternoon orbit component and ground processing of NOAA's old POES system. JPSS satellites carry sensors that collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The ground processing system for JPSS is known as the JPSS Common Ground System (JPSS CGS). Developed and maintained by Raytheon Intelligence, Information and Services (IIS), the CGS is a globally distributed, multi-mission system serving NOAA, NASA and their national and international partners. The CGS has demonstrated its scalability and flexibility to incorporate multiple missions efficiently and with minimal cost, schedule and risk, while strengthening global partnerships in weather and environmental monitoring. The CGS architecture has been upgraded to Block 2.0 to satisfy several key objectives, including: "operationalizing" the first satellite, Suomi NPP, which originally was a risk reduction mission; leveraging lessons learned in multi-mission support, taking advantage of newer, more reliable and efficient technologies and satisfying constraints due of the continually evolving budgetary environment. To ensure the CGS meets these needs, we have developed 48 Technical Performance Measures (TPMs) across 9 categories: Data Availability, Data Latency, Operational Availability, Margin, Scalability, Situational Awareness, Transition (between environments and sites), WAN Efficiency, and Data Recovery Processing. This paper will provide an overview of the CGS Block 2.0 architecture, with particular focus on the 9 TPM categories listed above. We will describe how we ensure the deployed architecture meets these TPMs to satisfy our multi-mission objectives with the deployment of Block 2.0.

  10. Identification of tropospheric emissions sources from satellite observations: Synergistic use of HCHO, NO2, and SO2 trace gas measurements

    Science.gov (United States)

    Marbach, T.; Beirle, S.; Khokhar, F.; Platt, U.

    2005-12-01

    We present case studies for combined HCHO, NO2, and SO2 satellite observations, derived from GOME measurements. Launched on the ERS-2 satellite in April 1995, GOME has already performed continuous operations over 8 years providing global observations of the different trace gases. In this way, satellite observations provide unique opportunities for the identifications of trace gas sources. The satellite HCHO observations provide information concerning the localization of biomass burning (intense source of HCHO). The principal biomass burning areas can be observed in the Amazon basin region and in central Africa Weaker HCHO sources (south east of the United States, northern part of the Amazon basin, and over the African tropical forest), not correlated with biomass burning, could be due to biogenic isoprene emissions. The HCHO data can be compared with NO2 and SO2 results to identify more precisely the tropospheric sources (biomass burning events, human activities, additional sources like volcanic emissions). Biomass burning are important tropospheric sources for both HCHO and NO2. Nevertheless HCHO reflects more precisely the biomass burning as it appears in all biomass burning events. NO2 correlate with HCHO over Africa (grassland fires) but not over Indonesia (forest fires). In south America, an augmentation of the NO2 concentrations can be observed with the fire shift from the forest to grassland vegetation. So there seems to be a dependence between the NO2 emissions during biomass burning and the vegetation type. Other high HCHO, SO2, and NO2 emissions can be correlated with climatic events like the El Nino in 1997, which induced dry conditions in Indonesia causing many forest fires.

  11. An automated fog monitoring system for the Indo-Gangetic Plains based on satellite measurements

    Science.gov (United States)

    Patil, Dinesh; Chourey, Reema; Rizvi, Sarwar; Singh, Manoj; Gautam, Ritesh

    2016-05-01

    Fog is a meteorological phenomenon that causes reduction in regional visibility and affects air quality, thus leading to various societal and economic implications, especially disrupting air and rail transportation. The persistent and widespread winter fog impacts the entire the Indo-Gangetic Plains (IGP), as frequently observed in satellite imagery. The IGP is a densely populated region in south Asia, inhabiting about 1/6th of the world's population, with a strong upward pollution trend. In this study, we have used multi-spectral radiances and aerosol/cloud retrievals from Terra/Aqua MODIS data for developing an automated web-based fog monitoring system over the IGP. Using our previous and existing methodologies, and ongoing algorithm development for the detection of fog and retrieval of associated microphysical properties (e.g. fog droplet effective radius), we characterize the widespread fog detection during both daytime and nighttime. Specifically, for the night time fog detection, the algorithm employs a satellite-based bi-spectral brightness temperature difference technique between two spectral channels: MODIS band-22 (3.9μm) and band-31 (10.75μm). Further, we are extending our algorithm development to geostationary satellites, for providing continuous monitoring of the spatial-temporal variation of fog. We anticipate that the ongoing and future development of a fog monitoring system would be of assistance to air, rail and vehicular transportation management, as well as for dissemination of fog information to government agencies and general public. The outputs of fog detection algorithm and related aerosol/cloud parameters are operationally disseminated via http://fogsouthasia.com/.

  12. Applications of asynoptic space - Time Fourier transform methods to scanning satellite measurements

    Science.gov (United States)

    Lait, Leslie R.; Stanford, John L.

    1988-01-01

    A method proposed by Salby (1982) for computing the zonal space-time Fourier transform of asynoptically acquired satellite data is discussed. The method and its relationship to other techniques are briefly described, and possible problems in applying it to real data are outlined. Examples of results obtained using this technique are given which demonstrate its sensitivity to small-amplitude signals. A number of waves are found which have previously been observed as well as two not heretofore reported. A possible extension of the method which could increase temporal and longitudinal resolution is described.

  13. Measurement of the gravitational redshift effect with RadioAstron satellite

    CERN Document Server

    Birukov, A V; Litvinov, D A; Porayko, N K; Rudenko, V N

    2015-01-01

    RadioAstron satellite admits in principle a testing the gravitational redshift effect with an accuracy of better than $10^{-5}$. It would surpass the result of Gravity Probe A mission at least an order of magnitude. However, RadioAstron's communications and frequency transfer systems are not adapted for a direct application of the non relativistic Doppler and troposphere compensation scheme used in the Gravity Probe A experiment. This leads to degradation of the redshift test accuracy approximately to the level 0.01. We discuss the way to overcome this difficulty and present preliminary results based on data obtained during special observing sessions scheduled for testing the new techniques.

  14. First comparison between ground-based and satellite-borne measurements of tropospheric nitrogen dioxide in the Po basin

    Science.gov (United States)

    Petritoli, Andrea; Bonasoni, Paolo; Giovanelli, Giorgio; Ravegnani, Fabrizio; Kostadinov, Ivan; Bortoli, Daniele; Weiss, Andrea; Schaub, Daniel; Richter, Andreas; Fortezza, Francesco

    2004-08-01

    In this paper we present in situ and tropospheric column measurements of NO2 in the Po river basin (northern Italy). The aim of the work is to provide a quantitative comparison between ground-based and satellite measurements in order to assess the validity of spaceborne measurements for estimating NO2 emissions and evaluate possible climatic effects. The study is carried out using in situ chemiluminescent instrumentation installed in the Po valley, a UV/Vis spectrometer installed at Mount Cimone (44.2°N, 10.7°E, 2165 m asl), and tropospheric column measurements obtained from the Global Ozone Monitoring Experiment (GOME) spectrometer. Results show that the annual cycle in surface concentrations and also some specific pollution periods observed by the air quality network are well reproduced by the GOME measurements. However, tropospheric columns derived from the surface measurements assuming a well-mixed planetary boundary layer (PBL) are much larger than the GOME columns and also have a different seasonal cycle. This is interpreted as indication of a smaller and less variable mixing height for NO2 in the boundary layer. Under particular meteorological conditions the agreement between UV/Vis tropospheric column observations and GOME measurements in the Mount Cimone area is good (R2 = 0.9) with the mixing properties of the atmosphere being the most important parameter for a valid comparison of the measurements. However, even when the atmospheric mixing properties are optimal for comparison, the ratio between GOME and ground-based tropospheric column data may not be unity. It is demonstrated that the values obtained (less than 1) are related to the fraction of the satellite ground pixel occupied by the NO2 hot spot.

  15. Oil Pollution Of The Southeastern Baltic Sea By Satellite Remote Sensing Data And In-Situ Measurements

    Directory of Open Access Journals (Sweden)

    Bulycheva Elena V.

    2015-12-01

    Full Text Available Results of operational satellite monitoring of oil pollution of the sea surface together with in-situ measurements of the oil products concentration in the water column for the first time allowed to establish relation between the surface pollution originated from ships, and the general characteristics of spatial and temporal distribution of oil products in the water column in the Southeastern Baltic Sea. Areas with heightened concentrations of oil products in the surface and bottom layers were determined for the study area. The main directions of the contamination propagation are agreed with the main direction of annual mean transport of substances in the Gdansk Basin.

  16. Fade measurements at L-band and UHF in mountainous terrain for land mobile satellite systems

    Science.gov (United States)

    Vogel, Wolfhard J.; Goldhirsh, Julius

    1988-01-01

    Fading results related to land mobile satellite communications at L-band (1502 MHz) and UHF (870 MHz) are described. These results were derived from an experiment performed in a series of canyon passes in the Boulder, Colorado region of the US. The experimental configuration involved a helicopter as the source platform, which maintained a relatively fixed geometry with a mobile van containing the receiver and data-acquisition system. An unobstructed line of sight between the radiating sources and the receiving van was, for the most part, also maintained. In this configuration, the dominant mechanism causing signal fading (or enhancement) is a result of multipath. The resulting fade distributions demonstrated that at the 1 percent and 5 percent levels, 5.5- and 2.6-dB fades were on the average exceeded at L-band and 4.8- and 2.4-dB at UHF, respectively, for a path elevation angle of 45 deg. The canyon results as compared with previous roadside-tree-shadowing results demonstrate that the deciding factor dictating fade margin for future land mobile satellite systems is tree shadowing rather than fades caused by multipath.

  17. Statistical interpolation of ozone measurements from satellite data (TOMS, SBUV and SAGE II) using the kriging method

    Energy Technology Data Exchange (ETDEWEB)

    Tranchant, B.J.S.; Vincent, A.P. [Montreal Univ., PQ (Canada). Dept. of Physics; Centre for Research on Computation and its Applications (CERCA), Montreal, PQ (Canada)

    2000-06-01

    This study demonstrates that ordinary kriging in spherical coordinates using experimental semivariograms provides highly usable results, especially near the pole in winter and/or where there could be data missing over large areas. In addition, kriging allows display of the spatial variability of daily ozone measurements at different pressure levels. Three satellite data sets were used: total ozone mapping spectrometer (TOMS) data, solar backscattered ultra violet (SBUV), and the stratospheric aerosol and gas experiment (SAGE II) ozone profiles. Since SBUV is a nadir-viewing instrument, measurements are only taken along the sun-synchronous polar orbits of the satellite. SAGE II is a limb-viewing solar occulation instrument, and measurements have high vertical resolution but poor daily coverage. TOMS has wider coverage with equidistant distribution of data (resolution 1 x 1.25 ) but provides no vertical information. Comparisons of the resulting SBUV-interpolated (column-integrated) ozone field with TOMS data are strongly in agreement, with a global correlation of close to 98%. Comparisons of SBUV-interpolated ozone profiles with daily SAGE II profiles are relatively good, and comparable to those found in the literature. The interpolated ozone layers at different pressure levels are shown. (orig.)

  18. Comparison of 7 years of satellite-borne and ground-based tropospheric NO2 measurements around Milan, Italy

    Science.gov (United States)

    OrdóñEz, C.; Richter, A.; Steinbacher, M.; Zellweger, C.; Nüß, H.; Burrows, J. P.; PréVôT, A. S. H.

    2006-03-01

    Tropospheric NO2 vertical column densities (VCDs) over the Lombardy region were retrieved from measurements of the Global Ozone Monitoring Experiment (GOME) spectrometer for the period 1996-2002 using a differential optical absorption method. This data set was compared with in situ measurements of NO2 at around 100 ground stations in the Lombardy region, northern Italy. The tropospheric NO2 VCDs are reasonably well correlated with the near-surface measurements under cloud-free conditions. However, the slope of the tropospheric VCDs versus ground measurements is higher in autumn-winter than in spring-summer. This effect is clearly reduced when the peroxyacetyl nitrate and nitric acid (HNO3) interferences of conventional NOx analyzers are taken into account. For a more quantitative comparison, the NO2 ground measurements were scaled to tropospheric VCDs using a seasonal NO2 vertical profile over northern Italy calculated by the Model of Ozone and Related Tracers 2 (MOZART-2). The tropospheric VCDs retrieved from satellite and those determined from ground measurements agree well, with a correlation coefficient R = 0.78 and a slope close to 1 for slightly polluted stations. GOME cannot reproduce the high NO2 amounts over the most polluted stations, mainly because of the large spatial variability in the distribution of pollution within the GOME footprint. The yearly and weekly cycles of the tropospheric NO2 VCDs are similar for both data sets, with significantly lower values in the summer months and on Sundays, respectively. Considering the pollution level and high aerosol concentrations of this region, the agreement is very good. Furthermore, uncertainties in the ground-based measurements, including the extrapolation to NO2 VCDs, might be as important as those of the NO2 satellite retrieval itself.

  19. Airborne Sunphotometer Measurements of Aerosol Optical Depth and Columnar Water Vapor During the Puerto Rico Dust Experiment, and Comparison with Land, Aircraft, and Satellite Measurements

    Science.gov (United States)

    Livingston, John M.; Russell, Philip B.; Reid, Jeffrey; Redemann, Jens; Schmid, Beat; Allen, Duane A.; Torres, Omar; Levy, Robert C.; Remer, Lorraine A.; Holben, Brent N.; Hipskind, R. Stephen (Technical Monitor)

    2002-01-01

    inversion. Finally, AATS-6 AOD values measured during low altitude aircraft traverses over the ocean are compared with corresponding AOD values retrieved over water from upwelling radiance measurements by the MODIS, TOMS, and GOES-8 Imager satellite sensors, with mixed results. These exercises highlight the need for continued satellite sensor comparison/validation studies to improve satellite AOD retrieval algorithms, and the usefulness of airborne sunphotometer measurements in the validation process.

  20. IceBridge Paroscientific L0 Pressure Altimeter Raw Air Pressure

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA IceBridge Paroscientific L0 Pressure Altimeter Raw Air Pressure (IAPRS0) data set contains air pressure readings taken over Antarctica using the...

  1. Satellite Altimetry and GRACE Gravimetry for Studies of Annual Water Storage Variations in Bangladesh

    Directory of Open Access Journals (Sweden)

    Ole Andersen

    2008-01-01

    Full Text Available Four different data sources have been compared with respect to observations of the annual water storage variations in the region of Bangladesh. Data from satellite altimeters and river gauges estimates the variation in surface water storage in the major rivers of Bangladesh.

  2. Studies on aerosol properties during ICARB–2006 campaign period at Hyderabad, India using ground-based measurements and satellite data

    Indian Academy of Sciences (India)

    K V S Badarinath; Shailesh Kumar Kharol

    2008-07-01

    Continuous and campaign-based aerosol field measurements are essential in understanding fundamental atmospheric aerosol processes and for evaluating their effect on global climate, environment and human life. Synchronous measurements of Aerosol Optical Depth (AOD), Black Carbon (BC) aerosol mass concentration and aerosol particle size distribution were carried out during the campaign period at tropical urban regions of Hyderabad, India. Daily satellite datasets of DMSP-OLS were processed for night-time forest fires over the Indian region in order to understand the additional sources (forest fires) of aerosol. The higher values in black carbon aerosol mass concentration and aerosol optical depth correlated well with forest fires occurring over the region. Ozone Monitoring Instrument (OMI) aerosol index (AI) variations showed absorbing aerosols over the region and correlated with ground measurements.

  3. A study of Asian dust plumes using satellite, surface, and aircraft measurements during the INTEX-B field experiment

    Science.gov (United States)

    Logan, Timothy; Xi, Baike; Dong, Xiquan; Obrecht, Rebecca; Li, Zhanqing; Cribb, Maureen

    2010-04-01

    Asian dust events occur frequently during the boreal spring season. Their optical properties have been analyzed by using a combination of source region (ground-based and satellite) and remote Pacific Ocean (aircraft) measurements during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) field campaign which lasted from 7 April to 15 May 2006. A strong dust event originating from the Gobi Desert and passing over the Xianghe surface site on 17 April 2006 has been extensively analyzed. The surface averaged aerosol optical depth (AOD) values increased from 0.17 (clear sky) to 4.0 (strong dust), and the Angström exponent (α) dropped from 1.26 (clear sky) to below 0.1. Its total downwelling SW flux over the Xianghe site (thousands of kilometers away from the dust source region) is only 46% of the clear-sky value with almost no direct transmission and nearly double the diffuse SW clear-sky value. This event was also captured 6 days later by satellite observations as well as the UND/NASA DC-8 aircraft over the eastern Pacific Ocean. The D