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Sample records for altimeter system glas

  1. 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.

  2. 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.

  3. 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

  4. Testing of the Geoscience Laser Altimeter System (GLAS) Prototype Loop Heat Pipe

    Science.gov (United States)

    Douglas, Donya; Ku, Jentung; Kaya, Tarik

    1998-01-01

    This paper describes the testing of the prototype loop heat pipe (LHP) for the Geoscience Laser Altimeter System (GLAS). The primary objective of the test program was to verify the loop's heat transport and temperature control capabilities under conditions pertinent to GLAS applications. Specifically, the LHP had to demonstrate a heat transport capability of 100 W, with the operating temperature maintained within +/-2K while the condenser sink was subjected to a temperature change between 273K and 283K. Test results showed that this loop heat pipe was more than capable of transporting the required heat load and that the operating temperature could be maintained within +/-2K. However, this particular integrated evaporator-compensation chamber design resulted in an exchange of energy between the two that affected the overall operation of the system. One effect was the high temperature the LHP was required to reach before nucleation would begin due to inability to control liquid distribution during ground testing. Another effect was that the loop had a low power start-up limitation of approximately 25 W. These Issues may be a concern for other applications, although it is not expected that they will cause problems for GLAS under micro-gravity conditions.

  5. 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.

  6. Retrievals of Thick Cloud Optical Depth from the Geoscience Laser Altimeter System (GLAS) by Calibration of Solar Background Signal

    Science.gov (United States)

    Yang, Yuekui; Marshak, Alexander; Chiu, J. Christine; Wiscombe, Warren J.; Palm, Stephen P.; Davis, Anthony B.; Spangenberg, Douglas A.; Nguyen, Louis; Spinhirne, James D.; Minnis, Patrick

    2008-01-01

    Laser beams emitted from the Geoscience Laser Altimeter System (GLAS), as well as other space-borne laser instruments, can only penetrate clouds to a limit of a few optical depths. As a result, only optical depths of thinner clouds (thick clouds using solar background light and treating GLAS as a solar radiometer. To do so we first calibrate the reflected solar radiation received by the photon-counting detectors of GLAS' 532 nm channel, which is the primary channel for atmospheric products. The solar background radiation is regarded as a noise to be subtracted in the retrieval process of the lidar products. However, once calibrated, it becomes a signal that can be used in studying the properties of optically thick clouds. In this paper, three calibration methods are presented: (I) calibration with coincident airborne and GLAS observations; (2) calibration with coincident Geostationary Operational Environmental Satellite (GOES) and GLAS observations of deep convective clouds; (3) calibration from the first principles using optical depth of thin water clouds over ocean retrieved by GLAS active remote sensing. Results from the three methods agree well with each other. Cloud optical depth (COD) is retrieved from the calibrated solar background signal using a one-channel retrieval. Comparison with COD retrieved from GOES during GLAS overpasses shows that the average difference between the two retrievals is 24%. As an example, the COD values retrieved from GLAS solar background are illustrated for a marine stratocumulus cloud field that is too thick to be penetrated by the GLAS laser. Based on this study, optical depths for thick clouds will be provided as a supplementary product to the existing operational GLAS cloud products in future GLAS data releases.

  7. A sample design for globally consistent biomass estimation using lidar data from the Geoscience Laser Altimeter System (GLAS

    Directory of Open Access Journals (Sweden)

    Healey Sean P

    2012-10-01

    Full Text Available Abstract Background Lidar height data collected by the Geosciences Laser Altimeter System (GLAS from 2002 to 2008 has the potential to form the basis of a globally consistent sample-based inventory of forest biomass. GLAS lidar return data were collected globally in spatially discrete full waveform “shots,” which have been shown to be strongly correlated with aboveground forest biomass. Relationships observed at spatially coincident field plots may be used to model biomass at all GLAS shots, and well-established methods of model-based inference may then be used to estimate biomass and variance for specific spatial domains. However, the spatial pattern of GLAS acquisition is neither random across the surface of the earth nor is it identifiable with any particular systematic design. Undefined sample properties therefore hinder the use of GLAS in global forest sampling. Results We propose a method of identifying a subset of the GLAS data which can justifiably be treated as a simple random sample in model-based biomass estimation. The relatively uniform spatial distribution and locally arbitrary positioning of the resulting sample is similar to the design used by the US national forest inventory (NFI. We demonstrated model-based estimation using a sample of GLAS data in the US state of California, where our estimate of biomass (211 Mg/hectare was within the 1.4% standard error of the design-based estimate supplied by the US NFI. The standard error of the GLAS-based estimate was significantly higher than the NFI estimate, although the cost of the GLAS estimate (excluding costs for the satellite itself was almost nothing, compared to at least US$ 10.5 million for the NFI estimate. Conclusions Global application of model-based estimation using GLAS, while demanding significant consolidation of training data, would improve inter-comparability of international biomass estimates by imposing consistent methods and a globally coherent sample frame. The

  8. Geoscience Laser Altimeter System (GLAS) Instrument: Flight Loop Heat Pipe (LHP) Acceptance Thermal Vacuum Test

    Science.gov (United States)

    Baker, Charles; Butler, Dan; Ku, Jentung; Grob, Eric; Swanson, Ted; Nikitkin, Michael; Powers, Edward I. (Technical Monitor)

    2001-01-01

    Two loop heat pipes (LHPs) are to be used for tight thermal control of the Geoscience Laser Altimeter System (GLAS) instrument, planned for flight in late 2001. The LHPs are charged with Propylene as a working fluid. One LHP will be used to transport 110 W from a laser to a radiator, the other will transport 160 W from electronic boxes to a separate radiator. The application includes a large amount of thermal mass in each LHP system and low initial startup powers. The initial design had some non-ideal flight design compromises, resulted in a less than ideal charge level for this design concept with a symmetrical secondary wick. This less than ideal charge was identified as the source of inadequate performance of the flight LHPs during the flight thermal vacuum test in October of 2000. We modified the compensation chamber design, re-built and charged the LHPs for a final LHP acceptance thermal vacuum test. This test performed March of 2001 was 100% successful. This is the last testing to be performed on the LHPs prior to instrument thermal vacuum test. This sensitivity to charge level was shown through varying the charge on a Development Model Loop Heat Pipe (DM LHP) and evaluating performance at various fill levels. At lower fills similar to the original charge in the flight units, the same poor performance was observed. When the flight units were re-designed and filled to the levels similar to the initial successful DM LHP test, the flight units also successfully fulfilled all requirements. This final flight Acceptance test assessed performance with respect to startup, low power operation, conductance, and control heater power, and steady state control. The results of the testing showed that both LHPs operated within specification. Startup on one of the LHPs was better than the other LHP because of the starter heater placement and a difference in evaporator design. These differences resulted in a variation in the achieved superheat prior to startup. The LHP with

  9. Geoscience Laser Altimeter System (GLAS): Final Test Report of DM LHP TV Testing. Revised

    Science.gov (United States)

    Baker, Charles

    2000-01-01

    The Demonstration Model (DM) Loop Heat Pipe (LHP) was tested at Goddard Space Flight Center (GSFC) during September and October, 1999. The LHP system was placed in the Dynavac 36 in. chamber in Building 4. The test lasted for about 6 weeks. The LHP was built, designed, and manufactured at Dynatherm Corporation, Inc. In Hunt Valley, MD according to GSFC specifications. The purpose of the test was to evaluate the performance of a propylene LHP for the Geoscience Laser Altimetry System (GLAS) instrument application.

  10. 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.

  11. 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.

  12. Receiver Design, Performance Analysis, and Evaluation for Space-Borne Laser Altimeters and Space-to-Space Laser Ranging Systems

    Science.gov (United States)

    Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

    1996-01-01

    This progress report consists of two separate reports. The first one describes our work on the use of variable gain amplifiers to increase the receiver dynamic range of space borne laser altimeters such as NASA's Geoscience Laser Altimeter Systems (GLAS). The requirement of the receiver dynamic range was first calculated. A breadboard variable gain amplifier circuit was made and the performance was fully characterized. The circuit will also be tested in flight on board the Shuttle Laser Altimeter (SLA-02) next year. The second report describes our research on the master clock oscillator frequency calibration for space borne laser altimeter systems using global positioning system (GPS) receivers.

  13. 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

  14. 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.

  15. 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.

  16. National Forest Aboveground Biomass Mapping from ICESat/GLAS Data and MODIS Imagery in China

    Directory of Open Access Journals (Sweden)

    Hong Chi

    2015-05-01

    Full Text Available Forest aboveground biomass (AGB was mapped throughout China using large footprint LiDAR waveform data from the Geoscience Laser Altimeter System (GLAS onboard NASA’s Ice, Cloud, and land Elevation Satellite (ICESat, Moderate Resolution Imaging Spectro-radiometer (MODIS imagery and forest inventory data. The entire land of China was divided into seven zones according to the geographic characteristics of the forests. The forest AGB prediction models were separately developed for different forest types in each of the seven forest zones at GLAS footprint level from GLAS waveform parameters and biomass derived from height and diameter at breast height (DBH field observation. Some waveform parameters used in the prediction models were able to reduce the effects of slope on biomass estimation. The models of GLAS-based biomass estimates were developed by using GLAS footprints with slopes less than 20° and slopes ≥ 20°, respectively. Then, all GLAS footprint biomass and MODIS data were used to establish Random Forest regression models for extrapolating footprint AGB to a nationwide scale. The total amount of estimated AGB in Chinese forests around 2006 was about 12,622 Mt vs. 12,617 Mt derived from the seventh national forest resource inventory data. Nearly half of all provinces showed a relative error (% of less than 20%, and 80% of total provinces had relative errors less than 50%.

  17. Thermal Vacuum Test of GLAS Propylene Loop Heat Pipe Development Model

    Science.gov (United States)

    Baker, Charles; Butler, Dan; Ku, Jentung; Kaya, Tarik; Nikitkin, Michael

    2000-01-01

    This paper presents viewgraphs on Thermal Vacuum Tests of the GLAS (Geoscience Laser Altimeter System) Propylene Loop Heat Pipe Development Model. The topics include: 1) Flight LHP System (Laser); 2) Test Design and Objectives; 3) DM (Development Model) LHP (Loop Heat Pipe) Test Design; 4) Starter Heater and Coupling Blocks; 5) CC Control Heaters and PRT; 6) Heater Plates (Shown in Reflux Mode); 7) Startup Tests; 8) CC Control Heater Power Tests for CC Temperature Control; and 9) Control Temperature Stability.

  18. A novel approach to estimate canopy height using ICESat/GLAS data : a case study in the New Forest National Park, UK

    NARCIS (Netherlands)

    Iqbal, I.A.; Dash, J.; Ullah, S.; Ahmad, G.

    2013-01-01

    The Geoscience Laser Altimeter System (GLAS) aboard Ice, Cloud and land Elevation Satellite (ICESat) is a spaceborne LiDAR sensor. It is the first LiDAR instrument which can digitize the backscattered waveform and offer near global coverage. Among others, scientific objectives of the mission include

  19. Vegetation height products between 60° S and 60° N from ICESat GLAS data

    Science.gov (United States)

    Los, S. O.; Rosette, J. A. B.; Kljun, N.; North, P. R. J.; Suárez, J. C.; Hopkinson, C.; Hill, R. A.; Chasmer, L.; van Gorsel, E.; Mahoney, C.; Berni, J. A. J.

    2011-09-01

    We present a new method to obtain coarse resolution (0.5° × 0.5°) vegetation height and vegetation-cover fraction data sets between 60° S and 60° N for use in climate models and ecological models. The data sets are derived from the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat), which is the only LiDAR instrument that provides close to global coverage when all data collected for 2003-2009 are combined. Filters are applied to the GLAS data to identify and eliminate spurious observations, e.g. data that are affected by clouds, atmosphere and terrain and as such result in erroneous estimates of vegetation height or vegetation cover. GLAS vegetation height estimates are aggregated in histograms from 0 to 70 m in 0.5 m intervals. The GLAS vegetation height product is evaluated in four ways. First, unfiltered and filtered individual GLAS vegetation height measurements are compared with aircraft LiDAR measurements of the same from seven sites in the Americas, Europe, and Australia. Application of filters increases the correlation with aircraft data from r = 0.36 to r = 0.67 and decreases the root-mean-square error by a factor 3. Second, the global aggregated GLAS vegetation height product is tested for sensitivity towards the choice of data quality filters; areas with frequent cloud cover and areas with steep terrain are the most sensitive to the choice of thresholds for the filters. Thirdly, the GLAS global vegetation height product is compared with two other global vegetation height products and is believed to produce more realistic characteristics: dominant vegetation height for tropical forests between 30 and 60 m versus 20 and 40 m in existing products. Finally, the GLAS bare soil cover fraction is compared globally with the MODIS bare soil fraction (r = 0.55) and with the FASIR bare soil cover fraction estimates (r = 0.58); the correlation between GLAS and MODIS tree-cover fraction was (r = 0.76). The evaluation

  20. 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...

  1. Slope Estimation from ICESat/GLAS

    Directory of Open Access Journals (Sweden)

    Craig Mahoney

    2014-10-01

    Full Text Available We present a novel technique to infer ground slope angle from waveform LiDAR, known as the independent slope method (ISM. The technique is applied to large footprint waveforms (\\(\\sim\\ mean diameter from the Ice, Cloud and Land Elevation Satellite (ICESat Geoscience Laser Altimeter System (GLAS to produce a slope dataset of near-global coverage at \\(0.5^{\\circ} \\times 0.5^{\\circ}\\ resolution. ISM slope estimates are compared against high resolution airborne LiDAR slope measurements for nine sites across three continents. ISM slope estimates compare better with the aircraft data (R\\(^{2}=0.87\\ and RMSE\\(=5.16^{\\circ}\\ than the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM inferred slopes (R\\(^{2}=0.71\\ and RMSE\\(=8.69^{\\circ}\\ ISM slope estimates are concurrent with GLAS waveforms and can be used to correct biophysical parameters, such as tree height and biomass. They can also be fused with other DEMs, such as SRTM, to improve slope estimates.

  2. 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.

  3. 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...

  4. The GLAS Algorithm Theoretical Basis Document for Precision Attitude Determination (PAD)

    Science.gov (United States)

    Bae, Sungkoo; Smith, Noah; Schutz, Bob E.

    2013-01-01

    The Geoscience Laser Altimeter System (GLAS) was the sole instrument for NASAs Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry mission. The primary purpose of the ICESat mission was to make ice sheet elevation measurements of the polar regions. Additional goals were to measure the global distribution of clouds and aerosols and to map sea ice, land topography and vegetation. ICESat was the benchmark Earth Observing System (EOS) mission to be used to determine the mass balance of the ice sheets, as well as for providing cloud property information, especially for stratospheric clouds common over polar areas.

  5. Applying ICESat/GLAS data to estimate forest aboveground biomass on Hokkaido, Japan

    Science.gov (United States)

    Hayashi, M.; Saigusa, N.; Oguma, H.; Yamao, Y.; Yamagata, Y.; Takao, G.

    2013-12-01

    Spaceborne Light Detection And Ranging (LiDAR) has an ability to measure forest resources with high accuracy, therefore, it will contribute to evaluating global carbon cycle or addressing climate change. We then evaluated the potential of spaceborne LiDAR to measure forest resources, and used Geoscience Laser Altimeter System (GLAS) data obtained with the Ice, Cloud, and land Elevation Satellite (ICESat) to develop an estimation methodology for forest biomass. The study area was the island of Hokkaido, Japan. We compared two estimation methods: (i) a direct method that uses some of the GLAS waveform parameters to estimate aboveground biomass (AGB) directly, and (ii) an allometric method that uses an allometric equation to estimate AGB from the canopy height estimated from the GLAS waveform. We used two kinds of ground truth data: (i) field survey data in situ measurements of AGB by the Bitterlich method at 106 points within GLAS footprints, and (ii) airborne LiDAR data from maximum canopy height measurements at 481 points within GLAS footprints. We then used the field survey data to develop the AGB estimation equation of the direct method by carrying out a multiple regression analysis that related GLAS waveform parameters to AGB. For the allometric method, we also carried out a multiple regression analysis using the airborne LiDAR data to estimate canopy height from GLAS data. Two parameters were used as the explanatory variables: a 'terrain index' calculated from the ground elevation difference within a GLAS footprint, and a 'GLAS waveform extent'. The root mean square error (RMSE) of the canopy height estimates was 4.1 m. We used the allometric equation determined from the field survey data to relate canopy height to AGB and then estimated the AGB from the GLAS estimates of canopy height. The accuracy of the AGB estimates obtained by these two estimation methods was determined by comparison with the field survey data. The RMSEs of the direct and allometric

  6. Glas Spacecraft Attitude Determination Using CCD Star Tracker and 3-AXIS Gyros

    Science.gov (United States)

    Bae, Sungkoo

    The main purpose of the Geoscience Laser Altimeter System (GLAS) is to determine the mass balance of the polar ice-sheets and their contributions to global sea level change. For the mission, the required accuracy for the laser altimeter height measurements is 10 cm. In this case, the direction in which the altimeter beam is pointing relative to the Terrestrial Reference Frame must be known to an accuracy of 1.5 arcseconds assuming the average slope of the ice-sheet surface is one degree. The laser pointing direction will be determined relative to the star field measured by a star tracker in the GLAS spacecraft (ICESAT). Thus, the specification of one arcsecond pointing accuracy requires that the spacecraft attitude determination has comparable accuracy. A Charge Coupled Device (CCD) star tracker and gyros will be installed in an optical bench of ICESAT to determine the spacecraft attitude. Each star position measurement from the CCD star tracker contains approximately five arcseconds position uncertainty depending on the magnitude of the observed stars. Furthermore, gyro output accuracy is corrupted by measurement noise and bias. The main purpose of this dissertation was to investigate the ability to determine the attitude to better than one arcsecond (1σ) using developed estimation algorithms. Extended Kalman Filters and a Batch method were developed and used to estimate the simulated GLAS attitude. The determined attitude showed that the root sum square of roll and pitch errors, which directly affect the laser beam pointing error, reduced to about 0.5 arcsecond (1σ), far better than one arcsecond. In order to support the study result, actual attitude data obtained from the X-ray Timing Explorer spacecraft, were processed with some of algorithms developed for this research. As a part of the generation of the measurement data, a star identification algorithm was developed.

  7. The GLAS Standard Data Products Specification-Data Dictionary, Version 1.0. Volume 15

    Science.gov (United States)

    Lee, Jeffrey E.

    2013-01-01

    The Geoscience Laser Altimeter System (GLAS) is the primary instrument for the ICESat (Ice, Cloud and Land Elevation Satellite) laser altimetry mission. ICESat was the benchmark Earth Observing System (EOS) mission for measuring ice sheet mass balance, cloud and aerosol heights, as well as land topography and vegetation characteristics. From 2003 to 2009, the ICESat mission provided multi-year elevation data needed to determine ice sheet mass balance as well as cloud property information, especially for stratospheric clouds common over polar areas. It also provided topography and vegetation data around the globe, in addition to the polar-specific coverage over the Greenland and Antarctic ice sheets.This document contains the data dictionary for the GLAS standard data products. It details the parameters present on GLAS standard data products. Each parameter is defined with a short name, a long name, units on product, type of variable, a long description and products that contain it. The term standard data products refers to those EOS instrument data that are routinely generated for public distribution. These products are distributed by the National Snow and Ice Data Center (NSDIC).

  8. The GLAS Algorithm Theoretical Basis Document for Precision Orbit Determination (POD)

    Science.gov (United States)

    Rim, Hyung Jin; Yoon, S. P.; Schultz, Bob E.

    2013-01-01

    The Geoscience Laser Altimeter System (GLAS) was the sole instrument for NASA's Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry mission. The primary purpose of the ICESat mission was to make ice sheet elevation measurements of the polar regions. Additional goals were to measure the global distribution of clouds and aerosols and to map sea ice, land topography and vegetation. ICESat was the benchmark Earth Observing System (EOS) mission to be used to determine the mass balance of the ice sheets, as well as for providing cloud property information, especially for stratospheric clouds common over polar areas. The GLAS instrument operated from 2003 to 2009 and provided multi-year elevation data needed to determine changes in sea ice freeboard, land topography and vegetation around the globe, in addition to elevation changes of the Greenland and Antarctic ice sheets. This document describes the Precision Orbit Determination (POD) algorithm for the ICESat mission. The problem of determining an accurate ephemeris for an orbiting satellite involves estimating the position and velocity of the satellite from a sequence of observations. The ICESatGLAS elevation measurements must be very accurately geolocated, combining precise orbit information with precision pointing information. The ICESat mission POD requirement states that the position of the instrument should be determined with an accuracy of 5 and 20 cm (1-s) in radial and horizontal components, respectively, to meet the science requirements for determining elevation change.

  9. Model Effects on GLAS-Based Regional Estimates of Forest Biomass and Carbon

    Science.gov (United States)

    Nelson, Ross F.

    2010-01-01

    Ice, Cloud, and land Elevation Satellite (ICESat) / Geosciences Laser Altimeter System (GLAS) waveform data are used to estimate biomass and carbon on a 1.27 X 10(exp 6) square km study area in the Province of Quebec, Canada, below the tree line. The same input datasets and sampling design are used in conjunction with four different predictive models to estimate total aboveground dry forest biomass and forest carbon. The four models include non-stratified and stratified versions of a multiple linear model where either biomass or (biomass)(exp 0.5) serves as the dependent variable. The use of different models in Quebec introduces differences in Provincial dry biomass estimates of up to 0.35 G, with a range of 4.94 +/- 0.28 Gt to 5.29 +/-0.36 Gt. The differences among model estimates are statistically non-significant, however, and the results demonstrate the degree to which carbon estimates vary strictly as a function of the model used to estimate regional biomass. Results also indicate that GLAS measurements become problematic with respect to height and biomass retrievals in the boreal forest when biomass values fall below 20 t/ha and when GLAS 75th percentile heights fall below 7 m.

  10. Vegetation height and cover fraction between 60° S and 60° N from ICESat GLAS data

    Science.gov (United States)

    Los, S. O.; Rosette, J. A. B.; Kljun, N.; North, P. R. J.; Chasmer, L.; Suárez, J. C.; Hopkinson, C.; Hill, R. A.; van Gorsel, E.; Mahoney, C.; Berni, J. A. J.

    2012-03-01

    We present new coarse resolution (0.5° × 0.5°) vegetation height and vegetation-cover fraction data sets between 60° S and 60° N for use in climate models and ecological models. The data sets are derived from 2003-2009 measurements collected by the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat), the only LiDAR instrument that provides close to global coverage. Initial vegetation height is calculated from GLAS data using a development of the model of Rosette et al. (2008) with with further calibration on desert sites. Filters are developed to identify and eliminate spurious observations in the GLAS data, e.g. data that are affected by clouds, atmosphere and terrain and as such result in erroneous estimates of vegetation height or vegetation cover. Filtered GLAS vegetation height estimates are aggregated in histograms from 0 to 70 m in 0.5 m intervals for each 0.5° × 0.5°. The GLAS vegetation height product is evaluated in four ways. Firstly, the Vegetation height data and data filters are evaluated using aircraft LiDAR measurements of the same for ten sites in the Americas, Europe, and Australia. Application of filters to the GLAS vegetation height estimates increases the correlation with aircraft data from r = 0.33 to r = 0.78, decreases the root-mean-square error by a factor 3 to about 6 m (RMSE) or 4.5 m (68% error distribution) and decreases the bias from 5.7 m to -1.3 m. Secondly, the global aggregated GLAS vegetation height product is tested for sensitivity towards the choice of data quality filters; areas with frequent cloud cover and areas with steep terrain are the most sensitive to the choice of thresholds for the filters. The changes in height estimates by applying different filters are, for the main part, smaller than the overall uncertainty of 4.5-6 m established from the site measurements. Thirdly, the GLAS global vegetation height product is compared with a global vegetation height product

  11. Estimating forest aboveground biomass using HJ-1 Satellite CCD and ICESat GLAS waveform data

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The ecosystem in northeastern China and the Russian Far East is a hotspot of scientific research into the global carbon balance.Forest aboveground biomass(AGB) is an important component in the land surface carbon cycle.In this study,using forest inventory data and forest distribution data,the AGB was estimated for forest in Daxinganlin in northeastern China by combining charge-coupled device(CCD) data from the Small Satellite for Disaster and Environment Monitoring and Forecast(HJ-1) and Geoscience Laser Altimeter System(GLAS) waveform data from the Ice,Cloud and land Elevation Satellite(ICESat).The forest AGB prediction models were separately developed for different forest types in the research area at GLAS footprint level from GLAS waveform parameters and field survey plot biomass in the Changqing(CQ) Forest Center,which was calculated from forest inventory data.The resulted statistical regression models have a R2=0.68 for conifer and R2=0.71 for broadleaf forests.These models were used to estimate biomass for all GLAS footprints of forest located in the study area.All GLAS footprint biomass coupled with various spectral reflectivity parameters and vegetation indices derived from HJ-1 satellite CCD data were used in multiple regression analyses to establish biomass prediction models(R2=0.55 and R2=0.52 for needle and broadleaf respectively).Then the models were used to produce a forest AGB map for the whole study area using the HJ-1 data.Biomass data obtained from forest inventory data of the Zhuanglin(ZL) Forest Center were used as independent field measurements to validate the AGB estimated from HJ-1 CCD data(R2=0.71).About 80% of biomass samples had an error less than 20 t ha-1,and the mean error of all validation samples is 5.74 t ha-1.The pixel-level biomass map was then stratified into different biomass levels to illustrate the AGB spatial distribution pattern in this area.It was found that HJ-1 wide-swath data and GLAS waveform data can be combined to

  12. MARA (Multimode Airborne Radar Altimeter) system documentation. Volume 1: MARA system requirements document

    Science.gov (United States)

    Parsons, C. L. (Editor)

    1989-01-01

    The Multimode Airborne Radar Altimeter (MARA), a flexible airborne radar remote sensing facility developed by NASA's Goddard Space Flight Center, is discussed. This volume describes the scientific justification for the development of the instrument and the translation of these scientific requirements into instrument design goals. Values for key instrument parameters are derived to accommodate these goals, and simulations and analytical models are used to estimate the developed system's performance.

  13. 14 CFR Appendix E to Part 43 - Altimeter System Test and Inspection

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Altimeter System Test and Inspection E Appendix E to Part 43 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT MAINTENANCE, PREVENTIVE MAINTENANCE, REBUILDING, AND ALTERATION Pt. 43, App. E Appendix E to...

  14. 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.

  15. Performance of the GLAS Onboard Surface Detection Algorithm

    Science.gov (United States)

    McGarry, Jan F.; Saba, Jack L.; Sun, Xiaoli; Abshire, James B.; Yi, Donghui; Brenner, Anita C.

    2003-01-01

    The Geoscience Laser Altimeter System (GLAS) determines the range from the satellite to the Earth's surface from the time of flight of the instrument's 1064 nm laser pulses, which are generated at a rate of 40 Hz. The time of flight is defined as the difference between the laser transmit time and the time of return of the surface echo. The detector output is digitized with a 1 ns sampling interval, starting before the laser fires and ending well after any possible surface return, for a total of 5.4 million points. Because there is not enough downlink bandwidth for the entire waveform, the algorithm must extract both the transmit and surface echo waveforms from the 5.4 million digitized points, and pass these waveforms on to be included in the science data packets. Results from orbit show the algorithm to be effective at finding the surface echoes. A few features of the algorithm, however, require post-launch modification. One is that cloud cover tends to cause the algorithm to raise the gain, which then causes saturation of surface echoes from clear regions immediately following the clouds. Details of the algorithm, along with specific examples and recent modifications, will be presented.

  16. 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.

  17. Height and Biomass of Mangroves in Africa from ICEsat/GLAS and SRTM

    Science.gov (United States)

    Fatoyinbo, Temilola E.; Simard, Marc

    2012-01-01

    The accurate quantification of forest 3-D structure is of great importance for studies of the global carbon cycle and biodiversity. These studies are especially relevant in Africa, where deforestation rates are high and the lack of background data is great. Mangrove forests are ecologically significant and it is important to measure mangrove canopy heights and biomass. The objectives of this study are to estimate: 1. The total area, 2. Canopy height distributions and 3. Aboveground biomass of mangrove forests in Africa. To derive mangrove 3-D structure and biomass maps, we used a combination of mangrove maps derived from Landsat ETM+, LiDAR canopy height estimates from ICEsat/GLAS (Ice, Cloud, and land Elevation Satellite/Geoscience Laser Altimeter System) and elevation data from SRTM (Shuttle Radar Topography Mission) for the African continent. More specifically, we extracted mangrove forest areas on the SRTM DEM using Landsat based landcover maps. The LiDAR (Light Detection and Ranging) measurements from the large footprint GLAS sensor were used to derive local estimates of canopy height and calibrate the Interferometric Synthetic Aperture Radar (InSAR) data from SRTM. We then applied allometric equations relating canopy height to biomass in order to estimate above ground biomass (AGB) from the canopy height product. The total mangrove area of Africa was estimated to be 25 960 square kilometers with 83% accuracy. The largest mangrove areas and greatest total biomass was 29 found in Nigeria covering 8 573 km2 with 132 x10(exp 6) Mg AGB. Canopy height across Africa was estimated with an overall root mean square error of 3.55 m. This error also includes the impact of using sensors with different resolutions and geolocation error which make comparison between measurements sensitive to canopy heterogeneities. This study provides the first systematic estimates of mangrove area, height and biomass in Africa. Our results showed that the combination of ICEsat/GLAS and

  18. Circular Microstrip Patch Array Antenna for C-Band Altimeter System

    Directory of Open Access Journals (Sweden)

    Asghar Keshtkar

    2008-01-01

    Full Text Available The purpose of this paper is to discuss the practical and experimental results obtained from the design, construction, and test of an array of circular microstrip elements. The aim of this antenna construction was to obtain a gain of 12 dB, an acceptable pattern, and a reasonable value of SWR for altimeter system application. In this paper, the cavity model was applied to analyze the patch and a proper combination of ordinary formulas; HPHFSS software and Microwave Office software were used. The array includes four circular elements with equal sizes and equal spacing and was planed on a substrate. The method of analysis, design, and development of this antenna array is explained completely here. The antenna is simulated and is completely analyzed by commercial HPHFSS software. Microwave Office 2006 software has been used to initially simulate and find the optimum design and results. Comparison between practical results and the results obtained from the simulation shows that we reached our goals by a great degree of validity.

  19. ICESat GLAS Elevation Changes and ALOS PALSAR InSAR Line-Of-Sight Changes on the Continuous Permafrost Zone of the North Slope, Alaska

    Science.gov (United States)

    Muskett, Reginald

    2016-04-01

    Measuring centimeter-scale and smaller surface changes by satellite-based systems on the periglacial terrains and permafrost zones of the northern hemisphere is an ongoing challenge. We are investigating this challenge by using data from the NASA Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (ICESat GLAS) and the JAXA Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) on the continuous permafrost zone of the North Slope, Alaska. Using the ICESat GLAS exact-repeat profiles in the analysis of ALOS PALSAR InSAR Line-Of-Sight (LOS) changes we find evidence of volume scattering over much of the tundra vegetation covered active-layer and surface scattering from river channel/banks (deposition and erosion), from rock outcropping bluffs and ridges. Pingos, ice-cored mounds common to permafrost terrains can be used as benchmarks for assessment of LOS changes. For successful InSAR processing, topographic and tropospheric phase cannot be assumed negligible and must be removed. The presence of significant troposphere phase in short-period repeat interferograms renders stacking ill suited for the task of deriving verifiable centimeter-scale surface deformation phase and reliable LOS changes. Ref.: Muskett, R.R. (2015), ICESat GLAS Elevation Changes and ALOS PALSAR InSAR Line-Of-Sight Changes on the Continuous Permafrost Zone of the North Slope, Alaska. International Journal of Geosciences, 6 (10), 1101-1115. doi:10.4236/ijg.2015.610086 http://www.scirp.org/Journal/PaperDownload.aspx?paperID=60406

  20. Mapping growing stock at 1-km spatial resolution for Spanish forest areas from ground forest inventory data and GLAS canopy height

    Science.gov (United States)

    Sánchez-Ruiz, S.; Chiesi, M.; Maselli, F.; Gilabert, M. A.

    2016-10-01

    National forest inventories provide measurements of forest variables (e.g. growing stock) that can be used for the estimation of above ground biomass (AGB). Mapping growing stock brings knowledge about spatial distribution and temporal dynamics of ABG, which is necessary for carbon cycle analysis. Several studies have been conducted on the integration of ground and optical remote sensing data to map forest biomass over Europe. Nevertheless, more direct information on forest biomass could be obtained by LiDAR techniques, which directly assess vertical forest structure by measuring the distance between the sensor and the scattering elements located inside the canopy volume. Thus, global 1-km maps of forest canopy height have been recently obtained from the Geoscience Laser Altimeter System (GLAS). The current study aims to produce a forest growing stock map in Spain. Five different forest type areas were identified in three provinces along a North - South gradient accounting for different ecosystems and climatic conditions. Growing stock ground data from the Third Spanish National Forest Inventory were assigned to each forest type and aggregated to 1-km spatial resolution. GLAS-derived canopy height was extracted for the locations of selected ground data. A relationship between inventory growing stock and satellite canopy height was found for each class. The obtained relationships were then extended all over Spain. The accuracy of the resulting growing stock map was assessed at province level against the Third Spanish National Forest Inventory growing stock estimations (R = 0.85, RMSE = 21 m3 ha-1).

  1. Advanced topographic laser altimeter system (ATLAS) receiver telescope assembly (RTA) and transmitter alignment and test

    Science.gov (United States)

    Hagopian, John; Bolcar, Matthew; Chambers, John; Crane, Allen; Eegholm, Bente; Evans, Tyler; Hetherington, Samuel; Mentzell, Eric; Thompson, Patrick L.; Ramos-Izquierdo, Luis; Vaughnn, David

    2016-09-01

    The sole instrument on NASA's ICESat-2 spacecraft shown in Figure 1 will be the Advanced Topographic Laser Altimeter System (ATLAS)1. The ATLAS is a Light Detection and Ranging (LIDAR) instrument; it measures the time of flight of the six transmitted laser beams to the Earth and back to determine altitude for geospatial mapping of global ice. The ATLAS laser beam is split into 6 main beams by a Diffractive Optical Element (DOE) that are reflected off of the earth and imaged by an 800 mm diameter Receiver Telescope Assembly (RTA). The RTA is composed of a 2-mirror telescope and Aft Optics Assembly (AOA) that collects and focuses the light from the 6 probe beams into 6 science fibers. Each fiber optic has a field of view on the earth that subtends 83 micro Radians. The light collected by each fiber is detected by a photomultiplier and timing related to a master clock to determine time of flight and therefore distance. The collection of the light from the 6 laser spots projected to the ground allows for dense cross track sampling to provide for slope measurements of ice fields. NASA LIDAR instruments typically utilize telescopes that are not diffraction limited since they function as a light collector rather than imaging function. The more challenging requirements of the ATLAS instrument require better performance of the telescope at the ¼ wave level to provide for improved sampling and signal to noise. NASA Goddard Space Flight Center (GSFC) contracted the build of the telescope to General Dynamics (GD). GD fabricated and tested the flight and flight spare telescope and then integrated the government supplied AOA for testing of the RTA before and after vibration qualification. The RTA was then delivered to GSFC for independent verification and testing over expected thermal vacuum conditions. The testing at GSFC included a measurement of the RTA wavefront error and encircled energy in several orientations to determine the expected zero gravity figure, encircled

  2. Estimation of Snow Depth in the Uinta Mountains using ICESat/GLAS Observations

    Science.gov (United States)

    Stoll, J.; Jasinski, M. F.

    2012-12-01

    Snow depth and water equivalent (SWE) are critical drivers of regional scale water processes, particularly in areas of complex mountainous terrain and deep snowpack. Because sparse in situ gages can not characterize all the spatial heterogeneity of these regions, high resolution remotely sensed observations offer a potential opportunity for future watershed-scale estimates of snow depth. In the current study, the capability of a satellite lidar altimetry for estimating snow depth was tested using surface elevations retrieved by the Geoscience Laser Altimeter Sensor (GLAS) flown on board the Ice, Cloud, and land Elevation Satellite from 2003-2009. By utilizing the instrument's database of seasonally repeated observations during snow on and snow off conditions, it is possible to evaluate the feasibility of estimating snow depth in mountainous terrain using space-based laser altimetry. The evaluation includes the analysis of GLAS waveforms, applying atmospheric and geophysical filtering criteria, and the testing and development of various methods of snow surface elevation estimation. This type of ICESat analysis was recently completed in the Uinta Mountains of NE Utah using several repeated GLAS tracks from 2005-2007 and compared to available regional SNOTEL data.

  3. 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.

  4. Latest technologies at Moerdijk Heye-Glas beer bottle factory; Dernieres technologies a l`usine de bouteilles Heye-Glas de Moerdijk

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    1999-04-01

    Having taken just nine months to build, the last HEYE-GLAS works of Moerdijk near Rotterdam is considered as Europe`s most modern hollow glass factory. It entered service on schedule in May 1988 and uses only the very latest equipment: a broken glass mill; a new oxy-fuel melter with heat recovery; and the largest IS machine. The extreme demands of this project led Heye-Glas to use a new state-of-the-art process control system for instrumentation and control. (author)

  5. Evaluation of GLAS Demonstration Model Loop Heat Pipe Thermal Vacuum Performance with Various Fluid Charges

    Science.gov (United States)

    Baker, Charles; Butler, Dan; Ku, Jentung; Grob, Eric; Swanson, Ted; Nikitkin, Michael; Paquin, Krista C. (Technical Monitor)

    2001-01-01

    Two loop heat pipes (LHPs) are to be used for tight thermal control of the Geoscience Laser Altimeter System (GLAS) instrument, planned for flight in late 2001. The LHPs are charged with Propylene as a working fluid. One LHP will be used to transport 110 W from a laser a radiator, the other will transport 190 W from electronic boxes to a separate radiator. The application includes a large amount of thermal mass in each LHP system and low initial startup powers. This along with some non-ideal flight design compromises, such as a less than ideal charge level for this design concept with a symmetrical secondary wick, lead to inadequate performance of the flight LHPs during the flight thermal vacuum test in October of 2000. This presentation focuses on identifying; the sources of the flight test difficulties by modifying the charge and test setup of the successfully tested Development Model Loop Heat Pipe (DM LHP). While very similar to the flight design, the DM L14P did have several significant difference in design and method of testing. These differences were evaluated for affect on performance by conforming the DM LHP to look more like the flight units. The major difference that was evaluated was the relative fill level of the working fluid within the concentrically design LHP compensation chamber. Other differences were also assessed through performance testing including starter heater size and "hot biasing" of major interior components. Performance was assessed with respect to startup, low power operation, conductance, and control heater power. The results of the testing showed that performance improves as initial charge increases, and when the starter heater is made smaller. The "hot biasing" of the major components did not appear to have a detrimental effect. As a result of test results of the DM LHP, modifications are being made to the flight units to increase the fluid charge and increase the watt-density of the starter heater.

  6. 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

  7. 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

  8. Canopy Height Estimation in French Guiana with LiDAR ICESat/GLAS Data Using Principal Component Analysis and Random Forest Regressions

    Directory of Open Access Journals (Sweden)

    Ibrahim Fayad

    2014-11-01

    Full Text Available Estimating forest canopy height from large-footprint satellite LiDAR waveforms is challenging given the complex interaction between LiDAR waveforms, terrain, and vegetation, especially in dense tropical and equatorial forests. In this study, canopy height in French Guiana was estimated using multiple linear regression models and the Random Forest technique (RF. This analysis was either based on LiDAR waveform metrics extracted from the GLAS (Geoscience Laser Altimeter System spaceborne LiDAR data and terrain information derived from the SRTM (Shuttle Radar Topography Mission DEM (Digital Elevation Model or on Principal Component Analysis (PCA of GLAS waveforms. Results show that the best statistical model for estimating forest height based on waveform metrics and digital elevation data is a linear regression of waveform extent, trailing edge extent, and terrain index (RMSE of 3.7 m. For the PCA based models, better canopy height estimation results were observed using a regression model that incorporated both the first 13 principal components (PCs and the waveform extent (RMSE = 3.8 m. Random Forest regressions revealed that the best configuration for canopy height estimation used all the following metrics: waveform extent, leading edge, trailing edge, and terrain index (RMSE = 3.4 m. Waveform extent was the variable that best explained canopy height, with an importance factor almost three times higher than those for the other three metrics (leading edge, trailing edge, and terrain index. Furthermore, the Random Forest regression incorporating the first 13 PCs and the waveform extent had a slightly-improved canopy height estimation in comparison to the linear model, with an RMSE of 3.6 m. In conclusion, multiple linear regressions and RF regressions provided canopy height estimations with similar precision using either LiDAR metrics or PCs. However, a regression model (linear regression or RF based on the PCA of waveform samples with waveform

  9. Concept selection and design considerations for compression facilities for FPSO Glas Dowr

    NARCIS (Netherlands)

    Roos, J. de; Eijk, A.; Gillis, J.

    2005-01-01

    As part of the modification of the Floating Production Storage and Offloading Unit (FPSO) Glas Dowr for operation on the Sable Field (offshore South Africa), a new gas compression system was installed. Associated gas is compressed for use as lift gas and re-injection back into the reservoir for pres

  10. 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

  11. Dimensionering af glas i klimaskærmen

    DEFF Research Database (Denmark)

    Munch-Andersen, Jørgen

    Denne anvisning berhandler dimensionering af glas som udfyldende element i klimaskærmen, det vil sige vinduer, facader og tage. Den indeholder de informationer, man normalt vil finde i en norm, men også andre oplysninger, der kan være nyttige ved dimensionering af glas. Anvisningen er udarbejdet ...

  12. Changes in the Earth's largest surge glacier system from satellite and airborne altimetry and imagery

    Science.gov (United States)

    Trantow, T.; Herzfeld, U. C.

    2015-12-01

    The Bering-Bagley Glacier System (BBGS), Alaska, one of the largest ice systems outside of Greenland and Antarctica, has recently surged (2011-2013), providing a rare opportunity to study the surge phenomenon in a large and complex system. Understanding fast-flowing glaciers and accelerations in ice flow, of which surging is one type, is critical to understanding changes in the cryosphere and ultimately changes in sea level. It is important to distinguish between types of accelerations and their consequences, especially between reversible or quasi-cyclic and irreversible forms of glacial acceleration, but current icesheet models treat all accelerating ice identically. Additionally, the surge provides an exceptional opportunity to study the influence of surface roughness and water content on return signals of altimeter systems. In this presentation, we analyze radar and laser altimeter data from CryoSat-2, NASA's Operation IceBridge (OIB), the ICESat Geoscience Laser Altimeter System (GLAS), ICESat-2's predecessor the Multiple Altimeter Beam Experimental Lidar (MABEL), and airborne laser altimeter and imagery campaigns by our research group. These measurements are used to study elevation, elevation change and crevassing throughout the glacier system. Analysis of the imagery from our airborne campaigns provides comprehensive characterizations of the BBGS surface over the course of the surge. Results from the data analysis are compared to numerical modeling experiments.

  13. Recent Data Campaigns and Results from the Laser Vegetation Imaging Sensor (LVIS): An Airborne, Medium-Footprint, Full-Waveform, Swath Mapping Laser Altimeter System

    Science.gov (United States)

    Blair, J. B.; Hofton, M. A.; Rabine, D. L.; Luthcke, S. B.; Greim, H.

    2005-12-01

    The Laser Vegetation Imaging Sensor (LVIS) is an airborne, medium-sized footprint laser altimeter system. By digitally recording the shape of the returning laser pulse (waveform), LVIS provides a precise and accurate view of the vertical structure within each footprint/pixel including both the sub-canopy and canopy-top topography. Applications of LVIS data include biomass estimation for a wide variety of forest types, ground surface change detection for tectonic studies, mapping sea surface topography to assist in coastal hazard assessment, and hydrology studies utilizing sub-canopy topography in densely forested regions. Since 1998, LVIS data have been collected in various areas of New Hampshire, Maine, Massachusetts, California, Maryland, Panama and Costa Rica. The data calibration and geolocation processing system utilizes a formal Bayesian least-squares-estimation of pointing, ranging and timing parameters based on a batch reduction of altimeter range residuals. Data are released publicly on the LVIS website at http://lvis.gsfc.nasa.gov. Results show data precisions of landcover type and study site location. Comparisons between LVIS and ICESat will also be presented.

  14. Assimilation of Altimeter Data into a Quasigeostrophic Model of the Gulf Stream System. Part 1; Dynamical Considerations

    Science.gov (United States)

    Capotondi, Antonietta; Malanotte-Rizzoli, Paola; Holland, William R.

    1995-01-01

    The dynamical consequences of constraining a numerical model with sea surface height data have been investigated. The model used for this study is a quasigeostrophic model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging technique. Nudging has been implemented in such a way as to achieve a high degree of convergence of the surface model fields toward the observations. The assimilation of the surface data is thus equivalent to the prescription of a surface pressure boundary condition. The authors analyzed the mechanisms of the model adjustment and the characteristics of the resultant equilibrium state when the surface data are assimilated. Since the surface data are the superposition of a mean component and an eddy component, in order to understand the relative role of these two components in determining the characteristics of the final equilibrium state, two different experiments have been considered: in the first experiment only the climatological mean field is assimilated, while in the second experiment the total surface streamfunction field (mean plus eddies) has been used. It is shown that the model behavior in the presence of the surface data constraint can be conveniently described in terms of baroclinic Fofonoff modes. The prescribed mean component of the surface data acts as a 'surface topography' in this problem. Its presence determines a distortion of the geostrophic contours in the subsurface layers, thus constraining the mean circulation in those layers. The intensity of the mean flow is determined by the inflow/outflow conditions at the open boundaries, as well as by eddy forcing and dissipation.

  15. Assimilation of Altimeter Data into a Quasigeostrophic Model of the Gulf Stream System. Part 2; Assimilation Results

    Science.gov (United States)

    Capotondi, Antonietta; Holland, William R.; Malanotte-Rizzoli, Paola

    1995-01-01

    The improvement in the climatological behavior of a numerical model as a consequence of the assimilation of surface data is investigated. The model used for this study is a quasigeostrophic (QG) model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height that have been obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging technique. Nudging has been implemented in such a way as to achieve a high degree of convergence of the surface model fields toward the observations. Comparisons of the assimilation results with available in situ observations show a significant improvement in the degree of realism of the climatological model behavior, with respect to the model in which no data are assimilated. The remaining discrepancies in the model mean circulation seem to be mainly associated with deficiencies in the mean component of the surface data that are assimilated. On the other hand, the possibility of building into the model more realistic eddy characteristics through the assimilation of the surface eddy field proves very successful in driving components of the mean model circulation that are in relatively good agreement with the available observations. Comparisons with current meter time series during a time period partially overlapping the Geosat mission show that the model is able to 'correctly' extrapolate the instantaneous surface eddy signals to depths of approximately 1500 m. The correlation coefficient between current meter and model time series varies from values close to 0.7 in the top 1500 m to values as low as 0.1-0.2 in the deep ocean.

  16. Historical note: Jules Séglas on language in dementia.

    Science.gov (United States)

    Obler, L K; Albert, M L

    1985-03-01

    In his book Des troubles du language chez les aliénés (1892) Séglas applied the model of language processing of his teacher, Charcot, to analyze the language disorders of various groups of mentally ill, including patients considered to suffer from dementia. Among the language phenomena he described from dementia are logorrhea, neologisms, embolalia, near-mutism, angophrasia, automatic speech, alexia, and agraphia. Séglas must be credited for his early descriptions of how language behaviors cluster in various psychiatric and dementing diseases.

  17. 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.

  18. Automated system for near-real time modelling and prediction of altimeter-derived sea level anomalies

    Science.gov (United States)

    Niedzielski, Tomasz; Miziński, Bartłomiej

    2013-08-01

    This paper serves as a presentation of a novel geoinformation system and a dedicated service, jointly named as Prognocean and based at the University of Wrocław (Poland), that aim to predict Sea Level Anomaly (SLA) maps and publish them online. The system works in near-real time and is updated daily. The data are provided by the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO), and the time series processed by Prognocean is delivered by various altimetric satellites. The emphasis is put on gridded SLA maps, also known as MSLA, which are provided as Delayed Time (DT) and Near-Real Time (NRT) daily products. The daily sampling interval, however, does not coincide with typical repeat cycles of altimetric satellites and is obtained through reprocessing produced by AVISO. The two-module infrastructure forms the system. The first module is responsible for the near-real time communication with AVISO to download the most recent MSLA data and acquire the corrected data when the geophysical corrections have been available. The second module forms the main engine which does data processing, modelling, forecasting, statistical quality control and finally generates products as maps. The online service, however, publishes the products online every day. The above-mentioned components and infrastructure are described in detail. The performance of the system was evaluated using at least 150 predicted MSLA maps, available after half year of computations carried out in near-real time. We identified a few regions of imperfect performance of our prognoses and found that they spatially correspond to the mouth of the Amazon River and locations of key mesoscale eddies, the vast majority of which being nonlinear and hence unmodelled in our experiment.

  19. 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.

  20. 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.

  1. Case studies of major DST-6 sounding impacts with the GLAS model

    Science.gov (United States)

    Atlas, R.

    1979-01-01

    Two case studies of DST-6 sounding impacts are presented. In each of these cases, major improvements to the GLAS model's forecasts of specific synoptic features resulted from including satellite-sounding data in the initial analysis.

  2. De teelt van witte rammenas (rettich) onder glas (Raphanus sativus L.)

    NARCIS (Netherlands)

    Janssen, G.A.J.

    1979-01-01

    Informatie over teelt van witte rammenas (rettich), waarbij aandacht voor de rassen, de teelt onder glas, bemesting, zaadkwaliteit en opkweek, oogsten, sorteren en verpakken, ziekten en ziektebestrijding en recepten.

  3. Design of Altimeter and Barometer Module Monitor System Based on CC2430%一种大气压力传感器数据采集系统的研究

    Institute of Scientific and Technical Information of China (English)

    侯小华; 胡文东; 张利利

    2011-01-01

    To monitor the work ability of pilot in the sky in real time, it detects the work environment of pilot, including of altimeter and barometer. It builds a system with CC2430 chip and SMD500 chip. It gets the altimeter and barometer parameters and writes to Micro SD card successfully. It also builds more date to research the work ability of pilot. Furthermore, it will be used to outdoors navigation, sports, weather forecast and so on.%为了实时监控飞行人员的工作能力状态,对飞行人员的工作环境参数进行实时检测;以Chipcon公司的CC2430单片机为主控制芯片,采用大容量存储设备,设计了实时监测大气压力及海拔高度的低功耗测量系统;给出了该控制器的功能和硬件结构以及软件流程设计;该系统在低压舱中模拟海拔高度为2400m的高空环境,测得气压数值为755hP,对应海拔高度为2413m,误差0.5%.实验结果表明,该系统可以成功的采集数据,并储存在MicroSD卡上.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Hoe hoger de haze bij diffuus glas, hoe hoger de meerproductie (interview met Jan Janse en Sonny Moerenhout)

    NARCIS (Netherlands)

    Kierkels, T.; Janse, J.; Moerenhout, S.

    2012-01-01

    Een vroege komkommerteelt onder diffuus glas gaf vanaf het begin een grotere opbrengst dan onder gewoon glas. Jan Janse van Wageningen UR Glastuinbouw durft na de reeks proeven in de afgelopen jaren de conclusie te trekken: hoe hoger de haze, hoe hoger de meerproductie. Dus ook in een vroege teelt.

  10. 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...

  11. Baseline Design and Performance Analysis of Laser Altimeter for Korean Lunar Orbiter

    Science.gov (United States)

    Lim, Hyung-Chul; Neumann, Gregory A.; Choi, Myeong-Hwan; Yu, Sung-Yeol; Bang, Seong-Cheol; Ka, Neung-Hyun; Park, Jong-Uk; Choi, Man-Soo; Park, Eunseo

    2016-09-01

    Korea’s lunar exploration project includes the launching of an orbiter, a lander (including a rover), and an experimental orbiter (referred to as a lunar pathfinder). Laser altimeters have played an important scientific role in lunar, planetary, and asteroid exploration missions since their first use in 1971 onboard the Apollo 15 mission to the Moon. In this study, a laser altimeter was proposed as a scientific instrument for the Korean lunar orbiter, which will be launched by 2020, to study the global topography of the surface of the Moon and its gravitational field and to support other payloads such as a terrain mapping camera or spectral imager. This study presents the baseline design and performance model for the proposed laser altimeter. Additionally, the study discusses the expected performance based on numerical simulation results. The simulation results indicate that the design of system parameters satisfies performance requirements with respect to detection probability and range error even under unfavorable conditions.

  12. 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.

  13. 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.

  14. 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.

  15. Data Fusion of Barometric Altimeter Enhanced GPS Integrated Navigation System%气压高度表增强GPS组合导航系统数据融合

    Institute of Scientific and Technical Information of China (English)

    杨朝斌; 牛强军; 徐其东

    2012-01-01

    An integrated navigation system for improving the vertical positioning accuracy of barometric altimeter enhanced GPS was proposed.The state and observation equations were established based on the location error of GPS,height error of BA and their "current" statistic model.The data fusion algorithm was given by iterative Kalman filtering(IKF).The theoretical analysis simulation and test results indicated that the vertical positioning accuracy,performance,reality and availability are improved more efficiently by the IKF algorithm than Kalman filter.The safety and reliability of airplane in the process of near-enter is guaranded by the algorithm which can be used as a guide system for precision approaching and landing.%针对在精密进场着陆阶段GPS信号易受干扰及高度准确性较差,气压高度表对气压及温度敏感的特点,提出了一种提高垂直方向定位精度的组合导航系统。基于GPS定位误差、气压高度表误差以及其"当前"统计模型,建立了系统的状态方程和观测方程,给出了采用迭代Kalman滤波的数据融合算法。理论分析仿真和实验结果表明,迭代Kalman滤波算法提高了垂直方向上的定位精度与实时性,改善可用性,性能优于Kalman滤波,保证了飞机在进近阶段的安全性和可靠性,可以作为精密进近阶段的着陆引导系统。

  16. Within-footprint roughness measurements using ICESat/GLAS waveform and LVIS elevation

    Science.gov (United States)

    Li, Xiaolu; Xu, Kai; Xu, Lijun

    2016-12-01

    The surface roughness is an important characteristic over an ice sheet or glacier, since it is an identification of boundary-layer meteorology and is an important limiter on the accuracy of surface-height measurements. In this paper, we propose a simulation method to derive the within-footprint roughness (called simulation-derived roughness) using ICESat/GLAS echo waveform, laser vegetation imaging sensor (LVIS) elevations, and laser profile array (LPA) images of ICESat/GLAS. By dividing the within-footprint surface into several elements, a simulation echo waveform can be obtained as the sum of the elementary pulses reflected from each surface element. The elevation of the surface elements, which is utilized to get the return time of the elementary pulses, is implemented based on an LVIS interpolated elevation using a radial basis function (RBF) neural network. The intensity of the elementary pulses can be obtained from the thresholded LPA images. Based on the return time and the intensity of the elementary pulses, we used the particle swarm optimization (PSO) method to approximate the simulation waveform to the ICESat/GLAS echo waveform. The full width at half maximum) (FWHM) of the elementary pulse was extracted from the simulation waveform for estimating the simulation-derived roughness. By comparing with the elevation-derived roughness (derived from the elevation) and the waveform-derived roughness (derived from the ICESat/GLAS waveform), the proposed algorithm can exclude the slope effect from waveform width broadening for describing the roughness of the surface elements.

  17. 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

  18. 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.

  19. Waveform model of a laser altimeter for an elliptical Gaussian beam.

    Science.gov (United States)

    Yue, Ma; Mingwei, Wang; Guoyuan, Li; Xiushan, Lu; Fanlin, Yang

    2016-03-10

    The current waveform model of a laser altimeter is based on the Gaussian laser beam of the fundamental mode, whose cross section is a circular spot, whereas some of the cross sections of Geoscience Laser Altimeter System lasers are closer to elliptical spots. Based on the expression of the elliptical Gaussian beam and the waveform theory of laser altimeters, the primary parameters of an echo waveform were derived. In order to examine the deduced expressions, a laser altimetry waveform simulator and waveform processing software were programmed and improved under the circumstance of an elliptical Gaussian beam. The result shows that all the biases between the theoretical and simulated waveforms were less than 0.5%, and the derived model of an elliptical spot is universal and can also be used for the conventional circular spot. The shape of the waveforms is influenced by the ellipticity of the laser spot, the target slope, and the "azimuth angle" between the major axis and the slope direction. This article provides the waveform theoretical basis of a laser altimeter under an elliptical Gaussian beam.

  20. Assessment of an ensemble system that assimilates Jason-1/Envisat altimeter data in a probabilistic model of the North Atlantic ocean circulation

    Directory of Open Access Journals (Sweden)

    G. Candille

    2014-12-01

    Full Text Available A realistic circulation model of the North Atlantic ocean at 1/4° resolution (NATL025 NEMO configuration has been adapted to explicitly simulate model uncertainties. This is achieved by introducing stochastic perturbations in the equation of state to represent the effect of unresolved scales on the model dynamics. The main motivation for this work is to develop ensemble data assimilation methods, assimilating altimetric data from past missions JASON-1 and ENVISAT. The assimilation experiment is designed to better control the Gulf Stream circulation for years 2005/06, focusing on frontal regions which are predominantly affected by unresolved dynamical scales. An ensemble based on such stochastic perturbations is first produced and evaluated using along-track altimetry observations. The Incremental Analysis Update (IAU scheme is applied in order to obtain an ensemble of continuous trajectories all over the 2005/06 assimilation period. These three elements – stochastic parameterization, ensemble simulation and 4-D observation operator – are then used together to perform a 4-D analysis of along-track altimetry over 10 day windows. Finally, the results of this experiment are objectively evaluated using the standard probabilistic approach developed for meteorological applications (Toth et al., 2003; Candille et al., 2007. The results show that the free ensemble – before starting the assimilation process – correctly reproduces the statistical variability over the Gulf Stream area: the system is then pretty reliable but not informative (null probabilistic resolution. Updating the free ensemble with altimetric data leads to a better reliability with an information gain around 30% (for 10 day forecasts of the SSH variable. Diagnoses on fully independent data (i.e. data that are not assimilated, like temperature and salinity profiles provide more contrasted results when the free and updated ensembles are compared.

  1. 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.

  2. Energy-related renovation in the world heritage. Retrofitting 'Glas-Hoffmann' buildings, Berlin; Energetische Sanierung im Weltkulturerbe. Sanierung 'Glas-Hoffmann'-Bauten, Berlin

    Energy Technology Data Exchange (ETDEWEB)

    Brensing, Christian

    2012-11-01

    Between 1955 and 1959, the housing estate at the Schiller park in Berlin-Wedding (Federal Republic in Germany) established in the 1920ies was expanded by four-storey house lines, the so-called Glas-Hoffmann buildings. Since 2008, this ensemble belongs to the Unesco World Heritage. In improving the thermal insulation of the building envelope and the adaptation of the building services to today's standards, therefore the architectural aesthetics of these buildings should not be endangered. The retrofitting was a pilot project of the research project ''Monument and energy - Postwar Modernism''.

  3. 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.

  4. Glas Journal: Deep Mappings of a Harbour or the Charting of Fragments, Traces and Possibilities

    Directory of Open Access Journals (Sweden)

    Silvia Loeffler

    2015-09-01

    Full Text Available With reference to a hybrid ethnographic project entitled Glas Journal (2014–2016, this article invites readers to reflect on the cultural mapping of spaces we intimately inhabit. Developed with the participation of local inhabitants of Dún Laoghaire Harbour, Ireland, Glas Journal seeks to explore the maritime environment as a liminal space, whereby the character of buildings and an area’s economic implications determine our relationship to space as much as our daily spatial rhythms and feelings of safety. Deep mapping provides the methodological blueprint for Glas Journal. In order to create a heteroglossic narrative of place and belonging, I will contextualise the project with references to seminal works in the visual arts, literature, film and geography that emotionally map spaces. Chronotopes of the threshold will be used to elaborate on spatial and cultural phenomena that occur when crossings from public to private and interior to exterior take place. Touching upon questions such as “What is a space of protection?”, “Who am I in it?”, and “Who is the Other?”, this article traces forms of liquid mapping that do not strive to conquer but rather to gain insight into the inner landscapes that are reflected in outer space.

  5. Interpretations of GLAS LiDAR for the Tapajos National Forest, Brazil

    Science.gov (United States)

    Hunter, M. O.; Keller, M.; Lefsky, M.; Espà­Rito-Santo, F.

    2007-12-01

    LiDAR remote sensing has proven to be a valuable source of information for characterization of forest structure. We conducted a study at the Tapajós National Forest (TNF) in the state of Pará, Brazil (centered at 3.56S 55.06W) to understand how forest structural properties interpreted from GLAS derived forest heights compared to a more traditional forest classification. The vegetation classification map was based on forest surveys, topography, soils, and interpretation of Landsat data. The original map groups TNF into 16 vegetation classifications. Using approximately 1500 GLAS waveform height predictions (Lefsky, ICESat Vegetation Product, heights ver.0.2) we calculated the 10th and 90th percentile values of distributions. These were interpreted as signals of disturbance and potential forest stand height respectively. We found no clear agreement on an area by area basis though general coherent patterns were observed. Areas close to human populations and those with high water-table depths showed a lower 10th percentile signal indicative of frequent recent disturbance. High plateau areas on clay soils had the greatest 90th percentile values. Our data suggests that statistical interpretation of GLAS may be valuable for comprehensive analyses of forest structure.

  6. Study on wave energy resource assessing method based on altimeter data—A case study in Northwest Pacific

    Institute of Scientific and Technical Information of China (English)

    WAN Yong; ZHANG Jie; MENG Junmin; WANG Jing; DAI Yongshou

    2016-01-01

    Wave energy resource is a very important ocean renewable energy. A reliable assessment of wave energy resources must be performed before they can be exploited. Compared with wave model, altimeter can provide more accuratein situ observations for ocean wave which can be as a novel method for wave energy assessment. The advantage of altimeter data is to provide accurate significant wave height observations for wave. In order to develop characteristic and advantage of altimeter data and apply altimeter data to wave energy assessment, in this study, we established an assessing method for wave energy in local sea area which is dedicated to altimeter data. This method includes three parts including data selection and processing, establishment of evaluation indexes system and criterion of regional division. Then a case study of Northwest Pacific was performed to discuss specific application for this method. The results show that assessing method in this paper can assess reserves and temporal and spatial distribution effectively and provide scientific references for the siting of wave power plants and the design of wave energy convertors.

  7. [Estimating forest canopy cover by combining spaceborne ICESat-GLAS waveforms and mul- tispectral Landsat-TM images].

    Science.gov (United States)

    2015-06-01

    The spatial distribution of forest canopy cover is a critical indicator for evaluating the forest productivity and decomposition rates. With the Wangqing Forest Region in Jilin Province of China as the study area, this study first estimated the forest canopy cover using spaceborne LiDAR IC- ESat-GLAS waveforms and Landsat-TM multispectral images, respectively, and then GLAS data and TM images were combined to further estimate forest canopy cover by using multiple linear regression and BP neural network. The results showed that when the forest canopy cover was estimated with single data source, the determination coefficient of model was 0.762 for GLAS data and 0.598 for TM data. When the forest canopy cover was estimated by combining GLAS data and TM data, the determination coefficient of model was 0.841 for multiple linear regression, and the simulation precision was 0.851 for BP neural network. The study indicated that the combination of ICESat-GLAS data and Landsat-TM images could exploit the advantages of multi-source remote sensing data and improve the estimating accuracy of forest canopy cover, and it was expected to provide a promising way for spatially continuous mapping of forest canopy cover in future.

  8. ICESat—GLAS测高数据在长江中下游湖泊水位变化监测中的应用%Monitoring Lake Water Level Changes in the Middle and Lower Yangtze River Basin Based on ICESat-GLAS Altimetry Data

    Institute of Scientific and Technical Information of China (English)

    吴红波; 郭忠明; 毛瑞娟

    2012-01-01

    Changes in lakes because of global climate change has become a national and international issue. We selected six typical lakes in China and analysed ICESat-GLAS data (ice, cloud, and land elevation satellite-geoscience laser altimeter system) to extract lake water elevations for 2003-2009. ICESat-GLAS altimeter waveform data were denoised by a Gaussian filter and used to distinguish between water and land. Lake boundaries were extracted from pre-processed Landsat TM imageries using a Fusion algorithm. Water level values within lake boundaries were used to construct inter-annual and annual water level time-variation curves. We found that the spatial accuracy of lake boundary data extracted from Landsat TM imageries is 10 m. The mean accuracy of measured ICESat altimeter data in the vicinity of Jiangba station at Hongze Lake, Chenglingji station at Dongting Lake, Xingzi and Changdu stations at Poyang Lake, Xishan station at Tai Lake, Zha station at Chao Lake and Gaoyou station at Gaoyou Lake are validated and assessed by observation data, and mean accuracy was -3.9 cm, -8.3 cm, -9.0 cm, -2.5 cm,-3.1 cm and-4.1 cm, respectively. Lake water levels in the middle and lower reaches of the Yangtze River basin show periodic fluctuation, and compared with historical observation data, the mean water level has decreased slightly. Lake water levels have been affected by regulation of the Three Gorges Project since October 2006. The relationship between lake water levels in the middle and lower Yangtze River basin and annual precipitation was correlated. Average water level changes for Hongze and Tai Lakes in 2006 fluctuated significantly. The average water level of Dongting, Poyang, Chaohu and Gaoyou Lakes peaked from June to October 2006.%在全球气候变暖的背景下湖泊变化已是国内外地学界关注的环境问题,并日益受到各国政府和研究机构的重视。本文以长江中下游的6个典型湖泊为研究对象,基于2003年-2009

  9. 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).

  10. 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.

  11. Los delirios de negación según Cotard y Séglas.

    Directory of Open Access Journals (Sweden)

    José María Álvarez Martínez

    2009-01-01

    Full Text Available Como señalan Haustgen y Bourgeois, hace algo más de un siglo el joven alienista parisino J. Séglas (1856-1939 publicó a lo largo de pocos años una serie de obras magistrales, destinadas a establecer de forma perdurable en Francia los cuadros de la clínica psiquiátrica. A los Trastornos del lenguaje en los alienados sucedieron tres años más tarde las Lecciones clínicas sobre las enfermedades mentales y nerviosas. Sólo dos años después apareció la famosa monografía sobre El delirio de negación. El colofón de toda esta obra fue el capítulo «Semiología de las afecciones mentales» del Tratado de Gilbert Ballet. En el intervalo, un número impresionante de artículos (se ha estimado que totalizan ciento treinta fue publicado por Séglas, tocando los más diversos terrenos de la clínica. Sin embargo, a pesar de que su nombre es muy frecuentemente citado por sus contemporáneos, esos trabajos y monografías no han sido reeditados, y hasta 1950 no comienzan a aparecer artículos un poco consecuentes sobre

  12. 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.

  13. On the recent elevation changes at the Flade Isblink Ice Cap, northern Greenland

    NARCIS (Netherlands)

    Rinne, E.J.; Shepherd, A.; Palmer, S.; van den Broeke, M.R.; Muir, A.; Ettema, J.; Wingham, D.

    2011-01-01

    We have used Radar Altimeter 2 (RA‐2) onboard ESA’s EnviSAT and Geosciences Laser Altimeter System (GLAS) onboard NASA’s ICESat to map the elevation change of the Flade Isblink Ice Cap (FIIC) in northern Greenland. Based on RA‐2 data we show that the mean surface elevation change of the FIIC has bee

  14. 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

  15. 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

  16. Antjie Krog se vertaling van Henk van Woerden se roman Een mond vol glas

    Directory of Open Access Journals (Sweden)

    H.P. van Coller

    2002-08-01

    Full Text Available Antjie Krog’s translation of Henk van Woerden’s novel Een mond vol glas (A mouth full of glass Against a historical backdrop several critical approaches to translational theory are explicated. Traditional criticism seems to imply positioning between the Source Text (ST and the Target Text (TT. A functionalist approach (as propagated among others by Snell-Hornby, Nord and Naaijkens is a descriptive rather than a normative approach that focuses almost exclusively on the ST. This approach is consequently adopted in the evaluation of Krog’s translation; yet even within this more relativistic paradigm, a comparison between ST and TT should not be evaded. In the case of Krog’s translation, this comparison leads to the identification of scores of lexical, grammatical and stylistic errors.

  17. GlasKon `99 - 7th Innovation Forum for Glass, Architecture, and Technology from January 18 to 23, 1999; GlasKon `99: 7. Innovations-Forum Glas, Architektur, Technik - Kongress und Ausstellung in Verbindung mit der Bau `99; GlasKon `99 - 7th Innovation Forum for Glass, Architecture, and Technology from January 18 to 23, 1999

    Energy Technology Data Exchange (ETDEWEB)

    Krewinkel, H.W.; Seger, P.E.; Achenbach, J. [comps.

    1999-10-01

    Thanks to its basic properties, i.e. transparency, weather resistance, and easy recyclability, glass is very well suited as a ``solar radiation-trapping`` building material. This congress and exhibition report presents, amongst other things, a solar glass of variable light and energy transmission, possibilities of passivsolar energy recovery in non-transparent facades, glazing for intelligent daylight utilisation, and innovative facades with photovoltaics. Four contributions have been abstracted individually for the Energy Database. [Deutsch] Der Baustoff Glas mit seinen grundlegenden Eigenschaften - Transparenz, Wetterbestaendigkeit sowie problemlose Recyclebarkeit dient auch als `` solare Strahlenfalle``. Im Folgenden werden ein Sonnenschutzglas mit veraenderbarer Licht-und Energietransmission, Moeglichkeiten der passiven solaren Energiegewinnung im nicht-transparentern Fassadenbereich, Verglasungen fuer die intelligente Tageslichtnutzung sowie innovative Fassaden mit Photovoltaik vorgestellt. Fuer die Datenbank Energy wurden vier Beitraege einzeln aufgenommen.

  18. Los delirios de negación según Cotard y Séglas.

    OpenAIRE

    2009-01-01

    Como señalan Haustgen y Bourgeois, hace algo más de un siglo el joven alienista parisino J. Séglas (1856-1939) publicó a lo largo de pocos años una serie de obras magistrales, destinadas a establecer de forma perdurable en Francia los cuadros de la clínica psiquiátrica. A los Trastornos del lenguaje en los alienados sucedieron tres años más tarde las Lecciones clínicas sobre las enfermedades mentales y nerviosas. Sólo dos años después apareció la famosa monografía sobre El delirio de negación...

  19. Continental Scale Vegetation Structure Mapping Using Field Calibrated Landsat, ALOS Palsar And GLAS ICESat

    Science.gov (United States)

    Scarth, P.; Phinn, S. R.; Armston, J.; Lucas, R.

    2015-12-01

    Vertical plant profiles are important descriptors of canopy structure and are used to inform models of biomass, biodiversity and fire risk. In Australia, an approach has been developed to produce large area maps of vertical plant profiles by extrapolating waveform lidar estimates of vertical plant profiles from ICESat/GLAS using large area segmentation of ALOS PALSAR and Landsat satellite image products. The main assumption of this approach is that the vegetation height profiles are consistent across the segments defined from ALOS PALSAR and Landsat image products. More than 1500 field sites were used to develop an index of fractional cover using Landsat data. A time series of the green fraction was used to calculate the persistent green fraction continuously across the landscape. This was fused with ALOS PALSAR L-band Fine Beam Dual polarisation 25m data and used to segment the Australian landscapes. K-means clustering then grouped the segments with similar cover and backscatter into approximately 1000 clusters. Where GLAS-ICESat footprints intersected these clusters, canopy profiles were extracted and aggregated to produce a mean vertical vegetation profile for each cluster that was used to derive mean canopy and understorey height, depth and density. Due to the large number of returns, these retrievals are near continuous across the landscape, enabling them to be used for inventory and modelling applications. To validate this product, a radiative transfer model was adapted to map directional gap probability from airborne waveform lidar datasets to retrieve vertical plant profiles Comparison over several test sites show excellent agreement and work is underway to extend the analysis to improve national biomass mapping. The integration of the three datasets provide options for future operational monitoring of structure and AGB across large areas for quantifying carbon dynamics, structural change and biodiversity.

  20. The inversion of average vegetation height using ICESat GLAS and MODIS data: a case study of three provinces in Northeastern China

    Science.gov (United States)

    Cheng, Feng; Wang, Cheng; Jiang, Xiaoguang

    2010-09-01

    The average vegetation height can be accurately extracted from ICESat GLAS data, however, a certain spatial interval exist in laser strips and dots reduces the mapping accuracy of average canopy height after the interpolation of the GLAS data. The MODIS-BRDF/albedo data consist of canopy structural data, such as LAI, canopy height etc. So the combination of ICESat GLAS and MODIS data can be obtained more accurate distribution of average canopy height and achieve the distribution of continuous canopy height. In this paper, the GLAS / MODIS data were collected in forest-rich three provinces in northeastern China. We firstly filtered GLAS waveform data and get the average vegetation height, and then selected the optional MODIS-BRDF / albedo bands to retrieve the average vegetation height. An artificial neural networks model was esTablelished by training the MODIS BRDF data, and finally obtained the average vegetation height over the whole three provinces. The fusion method between GLAS data and optical remote sensing image was proposed to make up for their shortages and obtained a continuous distribution of average vegetation height. It increases the analysis dimensions of forest ecosystem and produces more accurate data for forest biomass and carbon storage estimates.

  1. Passion at the threshold: Doctor Glas the flaneur in the films of Rune Carlstén and Mai Zetterling

    Directory of Open Access Journals (Sweden)

    Tytti Soila

    2010-11-01

    Full Text Available This article explores tropes of modernity in film adaptations of the 1905 novel Doctor Glas written by the Swedish author Hjalmar Söderberg. Drawing on Walter Benjamin and Miriam Hansen among others, the article attempts to show that certain expressive categories perceived as mutually exclusive by the contemporary audiences, in fact co-operate in order to constitute certain “points of impossibility” in the narrative and visual flow, where modern (gender identities mutate and manifest themselves.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. A Generalized Algorithm Deriving Vegetation Height from ICESat/GLAS Waveforms

    Science.gov (United States)

    Green, G. M.; Ni-Meister, W.; Lee, S.

    2010-12-01

    A location-insensitive geometric algorithm for extracting vegetation height from ICESat/GLAS waveform data has recently been developed and validated in a deciduous broadleaf biome with promising results. The current study extends the validation to different biomes using globally-available input data. Airborne lidar was used to evaluate the accuracy of the height algorithm in boreal, chaparral, temperate/deciduous, arctic, and urban settings, in preparation for applying the algorithm globally. The model is dependent on surface slope and on the extent of the transmitted and received waveforms. Different sources of slope information (SRTM, NED, airborne lidar) were compared for their effects on the slope term of the model. Non-vegetated flat surfaces isolated the effect of the transmit waveform, and suggested adjustments to the corresponding term. Accuracy of the waveform extent was found to be dependent on the quality of shots used, and an algorithm for filtering noisy waveforms based on waveform shape was developed. The choice of digital elevation model affected the slope term, and we found that SRTM yielded usable results when compared to NED and small-footprint lidar.

  9. 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...

  10. 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.

  11. Findings of, and reflections on, the Gender, Lifelong Learning and Social Class (GLAS project. A UK partnership based perspective.

    Directory of Open Access Journals (Sweden)

    Sue Betts

    2014-06-01

    Full Text Available This paper describes the main findings of GLAS, a two-year, EC co-funded project to address potential barriers to lifelong learning. In considering the genesis of the project, its structure and partnership, we will discuss findings from the perspective of UK partners, Linking London. We will show that tackling complex issues of social inclusion requires the creative use of processes and strategies which already exist within higher education, and conclude by making recommendations for future research and action.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Seasat altimeter observations of dynamic topography in the Gulf Stream region

    Science.gov (United States)

    Cheney, R. E.; Marsh, J. G.

    1981-01-01

    A straightforward approach to altimeter data analysis in the Gulf Stream system is presented, using a detailed geoid model to remove the gravitational component. The resulting sea surface height profiles compare remarkably well with independent oceanographic observations. Specific features such as cold rings, warm rings, and no anomaly regions are analyzed and it is shown that known positions of cyclonic and anticyclonic rings correspond with depressions and elevations, respectively, with amplitudes as large as 95 cm. The apparent fluctuation of the Gulf Stream is indicated by the results, as in the finding that on time scales of a few days, surface transport indicated by the sea surface height difference across the stream varied by nearly 30%

  20. Mapping lake level changes using ICESat/GLAS satellite laser altimetry data: a case study in arid regions of central Asia

    Science.gov (United States)

    Li, JunLi; Fang, Hui; Yang, Liao

    2011-12-01

    Lakes in arid regions of Central Asia act as essential components of regional water cycles, providing sparse but valuable water resource for the fragile ecological environments and human lives. Lakes in Central Asia are sensitive to climate change and human activities, and great changes have been found since 1960s. Mapping and monitoring these inland lakes would improve our understanding of mechanism of lake dynamics and climatic impacts. ICESat/GLAS satellite laser altimetry provides an efficient tool of continuously measuring lake levels in these poorly surveyed remote areas. An automated mapping scheme of lake level changes is developed based on GLAS altimetry products, and the spatial and temporal characteristics of 9 typical lakes in Central Asia are analyzed to validate the level accuracies. The results show that ICESat/GLAS has a good performance of lake level monitoring, whose patterns of level changes are the same as those of field observation, and the max differences between GLAS and field data is 3cm. Based on the results, it is obvious that alpine lakes are increasing greatly in lake levels during 2003-2009 due to climate change, while open lakes with dams and plain endorheic lakes decrease dramatically in water levels due to human activities, which reveals the overexploitation of water resource in Central Asia.

  1. Nieuwe soorten glas, anti-reflectie coatings en alternatieve krijtschermen: Volop keuze om zonlicht diffuus te maken en reflectie te verminderen

    NARCIS (Netherlands)

    Staalduinen, van J.; Hemming, S.

    2011-01-01

    Glas- en coatingproducenten hebben in de afgelopen paar jaar veel werk gemaakt van de ontwikkeling van diffuse kasdekmaterialen en dito schermen voor de glastuinbouw. Het aanbod is hierdoor sterk verbreed. Silke Hemming van Wageningen UR Glastuinbouw houdt de nieuwe materialen tegen het licht en maa

  2. 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

  3. 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.

  4. Building with green and glass. Innovations in the horticulture for living and working; Bouwen met groen en glas. Innovaties uit de glastuinbouw voor wonen en werken

    Energy Technology Data Exchange (ETDEWEB)

    Bergs, J.; Ter Haar, H.; Huisman, S.; Kristinsson, J.; Kruseman, I.; Oei, P.

    2007-07-01

    New technologies and insights from greenhouses, space technology and psychology are used for innovative applications in the building sector. Use is made of daylight, solar heat and vegetation. Architects can thus realize a clean, healthy and comfortable indoor climate in houses, school buildings, offices, health care centers, and also reduce the consumption of energy for cooling and heating. In particular attention is paid to the use of glass. [Dutch] Glastuinbouw, ruimtevaart en psychologie. Drie boeiende vakgebieden die op het eerste gezicht weinig met elkaar te maken hebben. Bouwen met groen en glas bewijst het tegendeel door gebruik te maken van nieuwe technieken en inzichten uit deze vakgebieden. Het concept maakt optimaal gebruik van daglicht, zonnewarmte en de weldaad van groen. Het toont de vele mogelijkheden die architecten met groen en glas kunnen aanboren. Waarom zou een architect dat doen? Omdat Bouwen met groen en glas de kern raakt van een uiterst actueel en tevens tijdloos thema: een schoon, gezond en prettig binnenklimaat in woningen, scholen, kantoren en zorginstellingen, gecombineerd met een substantieel lager energieverbruik voor koelen en verwarmen. Nieuwe technieken uit de glastuinbouw bieden nieuwe oplossingen. Bijvoorbeeld, in de zomer warmte oogsten en opslaan om die in de winter weer aan te boren. Veel glas stimuleert ook de toepassing van groen. Planten zijn meer dan versiering. Ze reinigen de lucht, zorgen voor bevochtiging en bieden mensen aangename omstandigheden om in te leren en te werken. Bouwen met groen en glas pleit dan ook voor gebouwen met een eigen ecosysteem, met planten als integraal onderdeel van het gebouw en de technische installaties.

  5. Toward variational assimilation of SARAL/Altika altimeter data in a North Atlantic circulation model at eddy-permitting resolution: assessment of a NEMO-based 4D-VAR system

    Science.gov (United States)

    Bouttier, Pierre-Antoine; Brankart, Jean-Michel; Candille, Guillem; Vidard, Arthur; Blayo, Eric; Verron, Jacques; Brasseur, Pierre

    2015-04-01

    In this project, the response of a variational data assimilation system based on NEMO and its linear tangent and adjoint model is investigated using a 4DVAR algorithm into a North-Atlantic model at eddy-permitting resolution. The assimilated data consist of Jason-2 and SARAL/AltiKA dataset collected during the 2013-2014 period. The main objective is to explore the robustness of the 4DVAR algorithm in the context of a realistic turbulent oceanic circulation at mid-latitude constrained by multi-satellite altimetry missions. This work relies on two previous studies. First, a study with similar objectives was performed based on academic double-gyre turbulent model and synthetic SARAL/AltiKA data, using the same DA experimental framework. Its main goal was to investigate the impact of turbulence on variational DA methods performance. The comparison with this previous work will bring to light the methodological and physical issues encountered by variational DA algorithms in a realistic context at similar, eddy-permitting spatial resolution. We also have demonstrated how a dataset mimicking future SWOT observations improves 4DVAR incremental performances at eddy-permitting resolution. Then, in the context of the OSTST and FP7 SANGOMA projects, an ensemble DA experiment based on the same model and observational datasets has been realized (see poster by Brasseur et al.). This work offers the opportunity to compare efficiency, pros and cons of both DA methods in the context of KA-band altimetric data, at spatial resolution commonly used today for research and operational applications. In this poster we will present the validation plan proposed to evaluate the skill of variational experiment vs. ensemble assimilation experiments covering the same period using independent observations (e.g. from Cryosat-2 mission).

  6. Estimating Canopy Gap Fraction Using ICESat GLAS within Australian Forest Ecosystems

    Directory of Open Access Journals (Sweden)

    Craig Mahoney

    2017-01-01

    Full Text Available Spaceborne laser altimetry waveform estimates of canopy Gap Fraction (GF vary with respect to discrete return airborne equivalents due to their greater sensitivity to reflectance differences between canopy and ground surfaces resulting from differences in footprint size, energy thresholding, noise characteristics and sampling geometry. Applying scaling factors to either the ground or canopy portions of waveforms has successfully circumvented this issue, but not at large scales. This study develops a method to scale spaceborne altimeter waveforms by identifying which remotely-sensed vegetation, terrain and environmental attributes are best suited to predicting scaling factors based on an independent measure of importance. The most important attributes were identified as: soil phosphorus and nitrogen contents, vegetation height, MODIS vegetation continuous fields product and terrain slope. Unscaled and scaled estimates of GF are compared to corresponding ALS data for all available data and an optimized subset, where the latter produced most encouraging results (R2 = 0.89, RMSE = 0.10. This methodology shows potential for successfully refining estimates of GF at large scales and identifies the most suitable attributes for deriving appropriate scaling factors. Large-scale active sensor estimates of GF can establish a baseline from which future monitoring investigations can be initiated via upcoming Earth Observation missions.

  7. 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.

  8. 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...

  9. The simulation of transient statistics of the Southern Hemispheric circulation by the GLAS seasonal cycle model: Preliminary results

    Science.gov (United States)

    Straus, D. M.; Shukla, J.

    1984-01-01

    The general circulation of the Southern Hemisphere is quite different from that of the Northern Hemisphere in many important ways. These include the barotropic nature of the stationary waves and the presence of a strong barotropic component to the mean zonal wind, the lack of a strong seasonal dependence of the transient eddies, and the dominant role played by eddies with periods less than 10 days compared to longer period fluctuations. Such differences attest to the importance of the altered nature of the orographic and thermal land-sea forcings in the Southern Hemisphere compared to the Northern Hemisphere. Some of the important features of the Southern Hemisphere circulation as simulated by the GLAS Seasonal Cycle Model (SCM) are presented. The geographical patterns of local variability and their seasonal shifts in the SCM are discussed and compared to observations.

  10. 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.

  11. 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.

  12. Extraction of the tidal amplitude from synthetic topography data of the BepiColombo laser altimeter in the polar regions of Mercury

    Science.gov (United States)

    Koch, Ch.; Christensen, U. R.; Kallenbach, R.

    2008-09-01

    ABSTRACT BepiColombo is one of the cornerstone missions of ESA to investigate Mercury which is the least investigated planet in the Solar System. The weak magnetic field observed by Mariner 10 in 1974 can be explained by a partly liquid core. The tidal Love number h2 reveals information on the thickness of the liquid outer core. The BepiColombo laser altimeter (BELA) on board the MPO spacecraft will map the entire surface of Mercury and should in principle allow for the retrieval of the tidal elevation of order one meter caused by solar gravitation. The highest density of BELA data are to be expected in the polar regions of Mercury because MPO orbits Mercury on a nearly polar trajectory. In previous simulations, we have tested whether it is possible to retrieve the tidal Love number h2 simultaneously with a spherical harmonic analysis of the global static topography of Mercury. Here, the analysis of orbit crossing points is presented. This analysis contains three main sources of uncertainty: a) instrumental and spacecraft positioning uncertainties, b) uncertainties due to the small-scale topography between two laser altimeter measurements, and c) uncertainties from the interpolation between laser altimeter measurement points. It can be shown that the uncertainty of the Love number can be reduced to about 3% using the crossing-point method. This is sufficient to test present theoretical models on the interior structure of Mercury.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. On the recovery of gravity anomalies from high precision altimeter data

    Science.gov (United States)

    Lelgemann, D.

    1976-01-01

    A model for the recovery of gravity anomalies from high precision altimeter data is derived which consists of small correction terms to the inverse Stokes' formula. The influence of unknown sea surface topography in the case of meandering currents such as the Gulf Stream is discussed. A formula was derived in order to estimate the accuracy of the gravity anomalies from the known accuracy of the altimeter data. It is shown that for the case of known harmonic coefficients of lower order the range of integration in Stokes inverse formula can be reduced very much.

  18. High-quality seamless DEM generation blending SRTM-1, ASTER GDEM v2 and ICESat/GLAS observations

    Science.gov (United States)

    Yue, Linwei; Shen, Huanfeng; Zhang, Liangpei; Zheng, Xianwei; Zhang, Fan; Yuan, Qiangqiang

    2017-01-01

    The absence of a high-quality seamless global digital elevation model (DEM) dataset has been a challenge for the Earth-related research fields. Recently, the 1-arc-second Shuttle Radar Topography Mission (SRTM-1) data have been released globally, covering over 80% of the Earth's land surface (60°N-56°S). However, voids and anomalies still exist in some tiles, which has prevented the SRTM-1 dataset from being directly used without further processing. In this paper, we propose a method to generate a seamless DEM dataset blending SRTM-1, ASTER GDEM v2, and ICESat laser altimetry data. The ASTER GDEM v2 data are used as the elevation source for the SRTM void filling. To get a reliable filling source, ICESat GLAS points are incorporated to enhance the accuracy of the ASTER data within the void regions, using an artificial neural network (ANN) model. After correction, the voids in the SRTM-1 data are filled with the corrected ASTER GDEM values. The triangular irregular network based delta surface fill (DSF) method is then employed to eliminate the vertical bias between them. Finally, an adaptive outlier filter is applied to all the data tiles. The final result is a seamless global DEM dataset. ICESat points collected from 2003 to 2009 were used to validate the effectiveness of the proposed method, and to assess the vertical accuracy of the global DEM products in China. Furthermore, channel networks in the Yangtze River Basin were also extracted for the data assessment.

  19. Aboveground forest biomass estimation using ICESat GLAS in Yunnan, China%基于ICESat GLAS的云南省森林地上生物量反演

    Institute of Scientific and Technical Information of China (English)

    黄克标; 庞勇; 舒清态; 付甜

    2013-01-01

    结合机载、星载激光雷达对GLAS(地球科学激光测高系统)光斑范围内的森林地上生物量进行估测,并利用MODIS植被产品以及MERIS土地覆盖产品进行了云南省森林地上生物量的连续制图.机载LiDAR扫描的260个训练样本用于构建星载GLAS的森林地上生物量估测模型,模型的决定系数(R2)为0.52,均方根误差(RMSE)为31 Mg/ha.研究结果显示,云南省总森林地上生物量为12.72亿t,平均森林地上生物量为94 Mg/ha.估测的森林地上生物量空间分布情况与实际情况相符,森林地上生物量总量与基于森林资源清查数据的估测结果相符,表明了利用机载LiDAR与星载ICESatGLAS结合进行大区域森林地上生物量估测的可靠性.%Accurate estimates of forest aboveground biomass (AGB) could reduce uncertainties in the characterization of terrestrial carbon fluxes. Light Detection and Ranging (LiDAR) provides an accurate measure of canopy height and vertical structure and information for the estimation of aboveground biomass of vegetation. Spaceborne large footprint LiDAR (ICESat GLAS) acquires over 250 million observations over forest regions globally and has been used successfully for forest height and biomass estimation in various sites. In this paper, airborne LiDAR and ICESat GLAS data were used to estimate aboveground biomass of forest at footprint level in Yunnan, China. Vegetation products from EOS MODIS and ENVISAT MERIS were used to expand these discrete estimations from GLAS data to a wall-to-wall map. The R2 between ICESat GLAS waveform parameters and airborne LiDAR estimated forest AGB is 0.52 after training with 260 footprints. Results showed that the total forest AGB in Yunnan Province was 1272 million ton and the average was 94 Mg/ha. The amount and distribution of predicted aboveground biomass were in good agreement with the reference data. The results showed that the predict model using GLAS data could be used to estimate

  20. 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.

  1. 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.

  2. 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.

  3. 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

    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...

  4. 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.

  5. NODC Standard Product: US Navy Geosat altimeter geophysical data records (GDRs) for the Geodetic Mission (NODC Accession 0053782)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains a complete copy of an NODC four CD-ROM product set containing all of NOAA's geophysical data records (GDRs) for the Geosat altimeter data...

  6. 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.

  7. 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.

  8. ASSIMILATION OF ALTIMETER WIND DATA IN MESOSCALE NUMERICAL MODEL (MM5)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Making use of altimeter wind data and standard sounding data in a mesoscale numerical model of PSU/NCAR (MM5), we test four-dimensional data assimilation scheme based on nudging. The purpose of this paper is to determine what meteorological fields and what assimilation method have positive effect on typhoon sea surface wind by simulating two typhoon cases in MM5. We perform seven experiments for 9608 Typhoon (Case 1): one control experiment, three analysis nudging experiments, two observation nudging experiments and one analysis and observation nudging experiment; we perform one control experiment and one analysis nudging experiment for 9711 Typhoon (Case 2). The results show assimilating wind-thermal fields can effectively improve simulation accuracy of the model; the experiment combining standard sounding data and surface observations can improve greatly the simulation accuracy of the model; the altimeter data contain lots of sea surface information and also have positive impact on typhoon sea surface wind.

  9. 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.

  10. 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.

  11. 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

  12. 无线电/激光高度表复合测高技术研究%Research into Composite Altimetry Technology Based on Radio/Laser Altimeter

    Institute of Scientific and Technical Information of China (English)

    毕开波; 姚申茂; 谢春思

    2016-01-01

    无线电高度表和激光高度表是巡航导弹上用于探测地形高度的2种主要传感器,激光高度表具有探测精度高、抗电磁干扰能力强的优点;而无线电高度表不受天气和环境的影响,可全天候使用。因而,将无线电高度表与激光高度表进行复合探测,有利于提高地形探测精度,并增强系统抗干扰能力。在高度表测量方程的基础上,基于卡尔曼滤波公式和简单融合算法,给出了无线电/激光多传感器的滤波及融合模型;并利用M atlab对多传感器融合效果进行了仿真。仿真结果表明:基于多传感器融合的高度测量系统的精度比单个传感器的测量精度要高,且系统的稳定性和可靠性更强,所设计的基于无线电/激光高度表多传感器数据融合的高度测量算法是有效的。%Radio altimeter and laser altimeter are two main sensors which is applied to detect terrain altitude of the cruise missiles .Laser altimeter has high detection precision ,strong anti-electromag-netism-jamming ability .However radio altimeter can work under the condition of all-weather , which is immune for weather and environment .Detection system combining radio altimeter with la-ser altimeter can improve terrain detection precision and anti-jamming ability .On the basis of altim-eter measuring equation ,this paper presents radio/laser multi-sensor filtering model and fusion model based on Kalman filtering formula and simple fusion arithmetic ;simulates the fusion effect of multi-sensor by means of Matlab .The simulation results show that the altimetry system based on multi-sensor fusion has higher detection precision than single sensor ,and has good stability and re-liability ,the multi-sensor data fusion altimetry arithmetic based on radio altimeter/laser is effec-tive .

  13. Design of in-situ detector applied to aircraft radio altimeter%一种飞机无线电高度表原位检测仪的设计

    Institute of Scientific and Technical Information of China (English)

    赵波; 魏俊淦; 田建学

    2015-01-01

    To realize the in-situ detection of the aircraft radio altimeter in out-field,the in-situ detector for the altimeter was developed by taking the industrial personal computer(IPC)PC104 and embedded processor STM32 as the system core,in which the design thoughts of the functional block diagram and each module,software functional partitioning and architecture are provided. The detector can implement the altimeter signal isolation and the voltage conversion,generate the altitude simulation signal and analog signal of the indicator,and provide the check signal of the altimeter to indicate the normal signal and alarm trip signal,and to measure the linear and nonlinear altitude voltage. The design has realized the simple and friendly human-com-puter interaction,and has been used and verified in the aviation test.%基于飞机外场原位检查无线电高度表的目的,采用PC104工控机和STM32嵌入式处理器为系统核心研制了高度表原位检测仪,包括功能框图、各模块的设计思路,软件功能划分和体系结构,实现高度表信号隔离和电平转换,产生高度模拟信号、指示器模拟信号、提供高度表检查信号,对正常、告警跳闸信号进行指示,对线性高度电压、非线性高度电压进行测量,该设计实现了简便友好的人机交互,已经在航空检测中使用验证.

  14. Low Altitude Target Detection Technique Based on Signal Detection of Radar Altimeter%基于雷达高度表信号的低空目标检测技术

    Institute of Scientific and Technical Information of China (English)

    韩兴斌; 颜坤玉; 冯富强

    2015-01-01

    针对低空目标突袭的威胁,根据低空目标普遍携带雷达高度表的特征,提出了基于雷达高度表信号探测的低空目标检测技术。针对海面飞行环境,根据双基地雷达的原理,对海面雷达散射信号进行了理论计算,从功率角度对低空目标检测可行性进行了分析,并给出了将侦察系统升空探测低空目标所携雷达高度表信号的方法,达到了对低空突防目标预警探测的要求。%A Low altitude target detection technique based on signal detection of radar altimeter is proposed to resolve the problem of low altitude target attack, as low altitude targets widely take radar altimeter. The method of heightening reconnaissance system to detect radar altimeter signal of low altitude target is proposed in environment of sea surface, which can satisfy the de-sire of warning detect of low altitude targets.

  15. The simulation of the seasonal cycle of the Southern Hemispheric circulation by the GLAS Seasonal Cycle Model and a comparison to observations

    Science.gov (United States)

    Straus, D. M.; Shukla, J.

    1983-01-01

    The general circulation of the Southern Hemisphere is quite different from that of the Northern Hemisphere in many important ways. These include the barotropic nature of the stationary waves and the presence of a strong barotropic component to the mean zonal wind, the lack of a strong seasonal dependence of the transient eddies, and the dominant role played by eddies with periods less than 10 days compared to longer period fluctuations. Such differences attest to the importance of the altered nature of the orographic and thermal land-sea forcings in the Southern Hemisphere compared to the Northern Hemisphere. Some of the important features of the Southern Hemisphere circulation as simulated by the GLAS Seasonal Cycle Model (SCM) are presented. The geographical patterns of local variability and their seasonal shifts in the SCM are discussed and compared to observations.

  16. Active gust load alleviation system for flexible aircraft: Mixed feedforward/feedback approach

    DEFF Research Database (Denmark)

    Alam, Mushfiqul; Hromcik, Martin; Hanis, Tomas

    2015-01-01

    Lightweight flexible blended-wing-body (BWB) aircraft concept seems as a highly promising configuration for future high capacity airliners which suffers from reduced stiffness for disturbance loads such as gusts. A robust feedforward gust load alleviation system (GLAS) was developed to alleviate ...

  17. Solfanger med antirefleksionsbehandlet glas

    DEFF Research Database (Denmark)

    Vejen, Niels Kristian

    The purpose of this work is to determine the improvement of the solar collector efficiency of a flat plate collector, at incident angles between 0° and 90°, by adding an antireflective coating to its normal low iron glass cover. And to determine the transmittance, at incident angles between 0...... will be tested in the same test facility. First with the normal low iron glass cover and afterwards with the glass with the antireflective coating. The solar collector efficiency for the solar collector with the two covers will be measured at different angles of incidence.The improvement of the solar...... transmittance by adding an antireflective coating to a normal low iron glass will be shown at different angles of incidence.The improvement of the solar collector efficiency for a flat plate solar collector by changing the normal low iron glass cover to a normal low iron glass with antireflective coating...

  18. Video Altimeter and Obstruction Detector for an Aircraft

    Science.gov (United States)

    Delgado, Frank J.; Abernathy, Michael F.; White, Janis; Dolson, William R.

    2013-01-01

    Video-based altimetric and obstruction detection systems for aircraft have been partially developed. The hardware of a system of this type includes a downward-looking video camera, a video digitizer, a Global Positioning System receiver or other means of measuring the aircraft velocity relative to the ground, a gyroscope based or other attitude-determination subsystem, and a computer running altimetric and/or obstruction-detection software. From the digitized video data, the altimetric software computes the pixel velocity in an appropriate part of the video image and the corresponding angular relative motion of the ground within the field of view of the camera. Then by use of trigonometric relationships among the aircraft velocity, the attitude of the camera, the angular relative motion, and the altitude, the software computes the altitude. The obstruction-detection software performs somewhat similar calculations as part of a larger task in which it uses the pixel velocity data from the entire video image to compute a depth map, which can be correlated with a terrain map, showing locations of potential obstructions. The depth map can be used as real-time hazard display and/or to update an obstruction database.

  19. 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.

  20. 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.

  1. 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

  2. The paratympanic organ: a barometer and altimeter in the middle ear of birds?

    Science.gov (United States)

    von Bartheld, Christopher S; Giannessi, Francesco

    2011-09-15

    A century has passed since the discovery of the paratympanic organ (PTO), a mechanoreceptive sense organ in the middle ear of birds and other tetrapods. This luminal organ contains a sensory epithelium with typical mechanosensory hair cells and may function as a barometer and altimeter. The organ is arguably the most neglected sense organ in living tetrapods. The PTO is believed to be homologous to a lateral line sense organ, the spiracular sense organ of nonteleostean fishes. Our review summarizes the current state of knowledge of the PTO and draws attention to the astounding lack of information about the unique and largely unexplored sensory modality of barometric perception.

  3. Mean sea surface and gravity investigations using TOPEX/Poseidon altimeter data

    Science.gov (United States)

    Rapp, Richard H.

    1991-01-01

    From a broad point of view, we will be concerned with studying global ocean circulation patterns on the basis of ocean surface determinations with geoid undulation information. In addition, we will study local variations of the gravity field implied by the altimeter data. These general goals are reflected in the title of our investigation. To meet our general goal, we have defined a number of specific objectives: (1) sea surface topography representation; (2) mean sea surface determination; (3) development of local geoid models; (4) mean sea surface comparisons; (5) sea surface topographic files; and (6) gravity anomaly determination.

  4. Comparison of retrieving methods of ocean wave periods from satellite altimeter with buoy measurements

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    For validating the results of retrieved mean wave period, four empirical algorithms established previously are introduced. Based on the data of over five years derived from TOPEX satellite altimeter for the entire East China Sea, ocean wave periods were calculated and statistical comparison among them was performed. The retrieved mean wave period obtained with our new distribution parameters showed better agreement with the wave period TB measured by buoy than that calculated by other three algorithms. The difference between the mean values of and that of TB is 0.16 s and the RMSE (root mean square error) of is the lowest value (0.48).

  5. 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....

  6. 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...

  7. 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.

  8. Altimeter data assimilation in the tropical Indian Ocean using water property conserving scheme

    Indian Academy of Sciences (India)

    Bhasha M Mankad; Rashmi Sharma; Sujit Basu; P K Pal

    2012-02-01

    Altimeter data have been assimilated in an ocean general circulation model using the water property conserving scheme. Two runs of the model have been conducted for the year 2004. In one of the runs, altimeter data have been assimilated sequentially, while in another run, assimilation has been suppressed. Assimilation has been restricted to the tropical Indian Ocean. An assessment of the strength of the scheme has been carried out by comparing the sea surface temperature (SST), simulated in the two runs, with in situ derived as well as remotely sensed observations of the same quantity. It has been found that the assimilation exhibits a significant positive impact on the simulation of SST. The subsurface effect of the assimilation could be judged by comparing the model simulated depth of the 20°C isotherm (hereafter referred to as D20), as a proxy of the thermocline depth, with the same quantity estimated from ARGO observations. In this case also, the impact is noteworthy. Effect on the dynamics has been judged by comparison of simulated surface current with observed current at a moored buoy location, and finally the impact on model sea level forecast in a free run after assimilation has been quantified in a representative example.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. The BepiColombo Laser Altimeter (BeLA) power converter module (PCM): Concept and characterisation

    Science.gov (United States)

    Rodrigo, J.; Gasquet, E.; Castro, J.-M.; Herranz, M.; Lara, L.-M.; Muñoz, M.; Simon, A.; Behnke, T.; Thomas, N.

    2017-03-01

    This paper presents the principal considerations when designing DC-DC converters for space instruments, in particular for the power converter module as part of the first European space laser altimeter: "BepiColombo Laser Altimeter" on board the European Space Agency-Japan Aerospace Exploration Agency (JAXA) mission BepiColombo. The main factors which determine the design of the DC-DC modules in space applications are printed circuit board occupation, mass, DC-DC converter efficiency, and environmental-survivability constraints. Topics included in the appropriated DC-DC converter design flow are hereby described. The topology and technology for the primary and secondary stages, input filters, transformer design, and peripheral components are discussed. Component selection and design trade-offs are described. Grounding, load and line regulation, and secondary protection circuitry (under-voltage, over-voltage, and over-current) are then introduced. Lastly, test results and characterization of the final flight design are also presented. Testing of the inrush current, the regulated output start-up, and the switching function of the power supply indicate that these performances are fully compliant with the requirements.

  14. Interest of Integrating Spaceborne LiDAR Data to Improve the Estimation of Biomass in High Biomass Forested Areas

    Directory of Open Access Journals (Sweden)

    Mohammad El Hajj

    2017-02-01

    Full Text Available Mapping forest AGB (Above Ground Biomass is of crucial importance to estimate the carbon emissions associated with tropical deforestation. This study proposes a method to overcome the saturation at high AGB values of existing AGB map (Vieilledent’s AGB map by using a map of correction factors generated from GLAS (Geoscience Laser Altimeter System spaceborne LiDAR data. The Vieilledent’s AGB map of Madagascar was established using optical images, with parameters calculated from the SRTM Digital Elevation Model, climatic variables, and field inventories. In the present study, first, GLAS LiDAR data were used to obtain a spatially distributed (GLAS footprints geolocation estimation of AGB (GLAS AGB covering Madagascar forested areas, with a density of 0.52 footprint/km2. Second, the difference between the AGB from the Vieilledent’s AGB map and GLAS AGB at each GLAS footprint location was calculated, and additional spatially distributed correction factors were obtained. Third, an ordinary kriging interpolation was thus performed by taking into account the spatial structure of these additional correction factors to provide a continuous correction factor map. Finally, the existing and the correction factor maps were summed to improve the Vieilledent’s AGB map. The results showed that the integration of GLAS data improves the precision of Vieilledent’s AGB map by approximately 7 t/ha. By integrating GLAS data, the RMSE on AGB estimates decreases from 81 t/ha (R2 = 0.62 to 74.1 t/ha (R2 = 0.71. Most importantly, we showed that this approach using LiDAR data avoids underestimating high biomass values (new maximum AGB of 650 t/ha compared to 550 t/ha with the first approach.

  15. 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.

  16. Effects of surface roughness on sea ice freeboard retrieval with an Airborne Ku-Band SAR radar altimeter

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    2010-01-01

    airborne radar and laser altimeters. We find regional variable penetration of the radar signal at late spring conditions, where the difference of the radar and the reference laser range measurement never agrees with the expected snow thickness. In addition, a rough surface can lead to biases...

  17. High-accuracy topographical information extraction based on fusion of ASTER stereo-data and ICESat/GLAS data in Antarctica

    Institute of Scientific and Technical Information of China (English)

    Wang DongChen; SHEN Qiang; XU Ying; CHEN Gang

    2009-01-01

    In order to better support Antarctic Inland ice sheet expedition from Zhongshan Station to Dome A, the topographic data are necessary. At present, although the entire Antarctic DEM provided by RAMP (Ra-daraat Antarctic Mapping Project) was estimated at the highest horizontal (spatial) resolution of about 200 m, the real horizontal resolution of the DEM varies from place to place depending on the density and scale of the original source data. For ice shelves and the inland ice sheet, the horizontal resolution is about 5 km; the vertical accuracy is estimated to be ±50 m in interior East Antarctic ice sheet and away from the mountain ranges. Therefore, more accurate topographic data are unavailable in Antarc-tica. In order to meet the requirements of high-accuracy topographic information for further researches, this paper mainly addresses a fusion study of ASTER stereo pairs and ICESat/GLAS altimetry data for extraction of high-accuracy DEM in East Antarctica, based on the high horizontal resolution (15 m) of ASTER and vertical accuracy (13.8 cm) of ICESat/GLAS. First, some altimetry data were selected as vertical control points to reduce errors of image correlation matching during the extraction of ASTER-based DEM. Second, ice sheet altimetry data derived from ICESat were used to generate DEM ranging from 75° to 81°S because existing ASTER data do not cover this area and high density of the coverage of ICESat altimetry data. Finally, the DEM in coverage of the expedition route was produced. The analysis of result reveals that the DEM accuracy is improved significantly. The absolute vertical accuracy of DEM is higher than 15 m in some cases and higher than 30 m for all the areas along the expedition route except from the 009-001 scene; the interior accuracy is higher than 15 m and higher than 7 m in some cases. It can meet the requirements of topographic map at 1 : 50000 scale, which is an economic and advantageous method to produce the topographic products.

  18. Regional glacier mass loss estimated by ICESat-GLAS data and SRTM digital elevation model in the West Kunlun Mountains, Tibetan Plateau, 2003-2009

    Science.gov (United States)

    Wu, Hongbo; Wang, Ninglian; Guo, Zhongming; Wu, Yuwei

    2014-01-01

    The Ice, Cloud and land Elevation Satellite (ICESat) altimetry and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data are used to estimate glacier mass loss changes in the West Kunlun Mountains, Tibetan Plateau (TP), 2003 to 2009. We integrated Landsat thematic mapper (TM)/enhanced TM images and GIS spatial analysis to map glacier surface elevation changes during 2003 to 2009. The ICESat-GLAS data can be used as baselines for surface elevation changes in altimetry as well as for TM imagery changes for depicting glacier area. Least-squares regression of an ICESat-derived thickness series shows the regional glacier mass decreased at an average rate of 1.41±0.23 km3/year water equivalent from 2003 to 2009, during the period of 2003 to 2009, the trend in thickness change became weaker. The ICESat-GLAS and SRTM DEM elevation differences between February 2003 and October 2009 show that the glacier surface elevations were decreasing below 5800 m but increased by 1.1±0.7 m above 6000 m a.s.l. region over that period. Thickness changes in the lower reaches of the glaciers indicate that the glacier ice ablation was mainly due to the summer temperature increases of 0.23°C and the summer precipitation decreases of 47.8 mm as measured at four stations, as well as the effects of sand and dust sources from the Tarim Basin. Meanwhile, in the upper parts of the glaciers (above 5800 m a.s.l.), ice surface elevation was increasing even though the Hetian station summer temperature at the 500 hPa level showed an obvious decrease of 0.78°C compared to 2003. In the upper part of the glacier-covered region, firn compaction and surface density should be taken into account. The glacier surges and bedrock movement may also lead to an underestimate of the volume loss due to the reduced mass conversion.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Waveform Retracking and Emulation Experiment Analysis of Synthetic Aperture Radar Altimeter

    Directory of Open Access Journals (Sweden)

    ZHAI Zhenhe

    2017-02-01

    Full Text Available Based on the synthetic aperture radar(SAR convolution model, the convolution computation formula about the derivative of three parameters of time migration, rise time and amplitude are deduced. The SAR waveform retracking is completed using numerical integration and Fourier transform. Besides, the echo waveform under SAR model is generated using the simulation orbit, troposphere, ionosphere and tide model. The comparison shows that the shape of echo waveform under SAR model is the same as that of CryoSat-2 1 Hz SAR. The experiments show that the accuracy of SAR altimeter retracking is about 5 cm under the 20 Hz data(about 350 m resolution, which are improved compared with that of the traditional model.

  4. 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.

  5. 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

  6. 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.

  7. Detecting volcanic resurfacing of heavily cratered terrain: Flooding simulations on the Moon using Lunar Orbiter Laser Altimeter (LOLA) data

    Science.gov (United States)

    Whitten, Jennifer L.; Head, James W.

    2013-09-01

    Early extrusive volcanism from mantle melting marks the transition from primary to secondary crust formation. Detection of secondary crust is often obscured by the high impact flux early in solar system history. To recognize the relationship between heavily cratered terrain and volcanic resurfacing, this study documents how volcanic resurfacing alters the impact cratering record and models the thickness, area, and volume of volcanic flood deposits. Lunar Orbiter Laser Altimeter (LOLA) data are used to analyze three different regions of the lunar highlands: the Hertzsprung basin; a farside heavily cratered region; and the central highlands. Lunar mare emplacement style is assumed to be similar to that of terrestrial flood basalts, involving large volumes of material extruded from dike-fed fissures over relatively short periods of time. Thus, each region was flooded at 0.5 km elevation intervals to simulate such volcanic flooding and to assess areal patterns, thickness, volumes, and emplacement history. These simulations show three primary stages of volcanic flooding: (1) Initial flooding is largely confined to individual craters and deposits are thick and localized; (2) basalt flows breach crater rim crests and are emplaced laterally between larger craters as thin widespread deposits; and (3) lateral spreading decreases in response to regional topographic variations and the deposits thicken and bury intermediate-sized and larger craters. Application of these techniques to the South Pole-Aitken basin shows that emplacement of ∼1-2 km of cryptomaria can potentially explain the paucity of craters 20-64 km in diameter on the floor of the basin relative to the distribution in the surrounding highlands.

  8. 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.

  9. 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.

  10. Monthly Maps of Sea Surface Height in the North Atlantic and Zonal Indices for the Gulf Stream Using TOPEX/Poseidon Altimeter Data

    Science.gov (United States)

    Singh, Sandipa; Kelly, Kathryn A.

    1997-01-01

    Monthly Maps of sea surface height are constructed for the North Atlantic Ocean using TOPEX/Poseidon altimeter data. Mean sea surface height is reconstructed using a weighted combination of historical, hydrographic data and a synthetic mean obtained by fitting a Gaussian model of the Gulf Stream jet to altimeter data. The resultant mean shows increased resolution over the hydrographic mean, and incorporates recirculation information that is absent in the synthetic mean. Monthly maps, obtained by adding the mean field to altimeter sea surface height residuals, are used to derive a set of zonal indices that describe the annual cycle of meandering as well as position and strength of the Gulf Stream.

  11. 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.

  12. 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.

  13. Geosat altimeter derived sea surface wind speeds and significant wave heights for the north Indian Ocean and their comparison with in situ data

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.; Vaithiyanathan, R.; Almeida, A.M.; Santanam, K.; Rao, L.V.G.; Sarkar, A.; Kumar, R.; Gairola, R.M.; Gohil, B.S.

    Geosat altimeter data for the period November 1986-October 1987 over the north Indian Ocean have been processed to retrieve wind speeds and significant wave heights. Smoothed Brown algorithm is used to retrieve wind speeds from back...

  14. Observing System Evaluations Using GODAE Systems

    Science.gov (United States)

    2009-09-01

    Journal of Marine Systems 35...dimensional temperature fields: A first approach based on simulated observations. Journal of Marine Systems 46:85-98. Langland, R.H., and N.L. Baker...capabilities of multisatellite altimeter missions: First results with real data in the Mediterranean Sea. Journal of Marine Systems 65:190-211.

  15. 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.

  16. 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.

  17. Comparison of Thermal Performance Characteristics of Ammonia and Propylene Loop Heat Pipes

    Science.gov (United States)

    Kaya, Tarik; Baker, Charles; Ku, Jentung

    2000-01-01

    In this paper, experimental work performed on a breadboard Loop Heat Pipe (LHP) is presented. The test article was built by DCI for the Geoscience Laser Altimeter System (GLAS) instrument on the ICESat spacecraft. The thermal system requirements of GLAS have shown that ammonia cannot be used as the working fluid in this LHP because GLAS radiators could cool to well below the freezing point of ammonia. As a result, propylene was proposed as an alternative LHP working fluid since it has a lower freezing point than ammonia. Both working fluids were tested in the same LHP following a similar test plan in ambient conditions. The thermal performance characteristics of ammonia and propylene LHP's were then compared. In general, the propylene LHP required slightly less startup superheat 5nd less control heater power than the ammonia LHP, The thermal conductance values for the propylene LHP were also lower than the ammonia LHP. Later, the propylene LHP was tested in a thermal vacuum chamber. These tests demonstrated that propylene could meet the GLAS thermal design requirements. Design guidelines were proposed for the next flight-like Development Model (DM) LHP for thermal control of the GLAS instrument.

  18. 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.

  19. TIDAL FEATURES IN THE CHINA SEAS AND THEIR ADJACENT SEA AREAS AS DERIVED FROM TOPEX/POSEIDON ALTIMETER DATA

    Institute of Scientific and Technical Information of China (English)

    胡建宇; HiroshiKAWAMURA; 洪华生; FumiakiKOBASHI; 谢强

    2001-01-01

    Some important tidal features of 8 major tidal constituents (M2, S2, K1, O1, P1,Sa, N2 and K2 ) in the china Seas and their adjacent sea areas were obtained using six years' TOPEX/POSEIDON altimeter data. The results showed that the obtained co-tidal and co-range charts for these major tidal constituents agreed well with those of previous researches using observational data from coastal tidal gauge stations and numerical models.

  20. DUACS DT2014: the new multi-mission altimeter data set reprocessed over 20 years

    Science.gov (United States)

    Pujol, Marie-Isabelle; Faugère, Yannice; Taburet, Guillaume; Dupuy, Stéphanie; Pelloquin, Camille; Ablain, Michael; Picot, Nicolas

    2016-09-01

    The new DUACS DT2014 reprocessed products have been available since April 2014. Numerous innovative changes have been introduced at each step of an extensively revised data processing protocol. The use of a new 20-year altimeter reference period in place of the previous 7-year reference significantly changes the sea level anomaly (SLA) patterns and thus has a strong user impact. The use of up-to-date altimeter standards and geophysical corrections, reduced smoothing of the along-track data, and refined mapping parameters, including spatial and temporal correlation-scale refinement and measurement errors, all contribute to an improved high-quality DT2014 SLA data set. Although all of the DUACS products have been upgraded, this paper focuses on the enhancements to the gridded SLA products over the global ocean. As part of this exercise, 21 years of data have been homogenized, allowing us to retrieve accurate large-scale climate signals such as global and regional MSL trends, interannual signals, and better refined mesoscale features.An extensive assessment exercise has been carried out on this data set, which allows us to establish a consolidated error budget. The errors at mesoscale are about 1.4 cm2 in low-variability areas, increase to an average of 8.9 cm2 in coastal regions, and reach nearly 32.5 cm2 in high mesoscale activity areas. The DT2014 products, compared to the previous DT2010 version, retain signals for wavelengths lower than ˜ 250 km, inducing SLA variance and mean EKE increases of, respectively, +5.1 and +15 %. Comparisons with independent measurements highlight the improved mesoscale representation within this new data set. The error reduction at the mesoscale reaches nearly 10 % of the error observed with DT2010. DT2014 also presents an improved coastal signal with a nearly 2 to 4 % mean error reduction. High-latitude areas are also more accurately represented in DT2014, with an improved consistency between spatial coverage and sea ice edge

  1. 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.

  2. Observations of the north polar region of Mars from the Mars orbiter laser altimeter

    Science.gov (United States)

    Zuber, M. T.; Smith, D. E.; Solomon, S. C.; Abshire, J. B.; Afzal, R. S.; Aharonson, O.; Fishbaugh, K.; Ford, P. G.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Ivanov, A. B.; Johnson, C. L.; Muhleman, D. O.; Neumann, G. A.; Pettengill, G. H.; Phillips, R. J.; Sun, X.; Zwally, H. J.; Banerdt, W. B.; Duxbury, T. C.

    1998-01-01

    Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

  3. Martian Polar Region Impact Craters: Geometric Properties From Mars Orbiter Laser Altimeter (MOLA) Observations

    Science.gov (United States)

    Garvin, J. B.; Sakimoto, S. E. H.; Frawley, J. J.; Matias, A.

    1998-01-01

    The Mars Orbiter Laser Altimeter (MOLA) instrument onboard the Mars Global Surveyor (MGS) spacecraft has so far observed approximately 100 impact landforms in the north polar latitudes (>60 degrees N) of Mars. Correlation of the topography with Viking Orbiter images indicate that many of these are near-center profiles, and for some of the most northern craters, multiple data passes have been acquired. The northern high latitudes of Mars may contain substantial ground ice and be topped with seasonal frost (largely CO2 with some water), forming each winter. We have analyzed various diagnostic crater topologic parameters for this high-latitude crater population with the objective of characterizing impact features in north polar terrains, and we explore whether there is evidence of interaction with ground ice, frost, dune movement, or other polar processes. We find that there are substantial topographic variations from the characteristics of midlatitude craters in the polar craters that are not readily apparent from prior images. The transition from small simple craters to large complex craters is not well defined, as was observed in the midlatitude MOLA data (transition at 7-8 km). Additionally, there appear to be additional topographic complexities such as anomalously large central structures in many polar latitude impact features. It is not yet clear if these are due to target-induced differences in the formation of the crater or post-formation modifications from polar processes.

  4. Summary of the results from the lunar orbiter laser altimeter after seven years in lunar orbit

    Science.gov (United States)

    Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Lemoine, Frank G.; Head, James W., III; Lucey, Paul G.; Aharonson, Oded; Robinson, Mark S.; Sun, Xiaoli; Torrence, Mark H.; Barker, Michael K.; Oberst, Juergen; Duxbury, Thomas C.; Mao, Dandan; Barnouin, Olivier S.; Jha, Kopal; Rowlands, David D.; Goossens, Sander; Baker, David; Bauer, Sven; Gläser, Philipp; Lemelin, Myriam; Rosenburg, Margaret; Sori, Michael M.; Whitten, Jennifer; Mcclanahan, Timothy

    2017-02-01

    In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.

  5. A New Lunar Digital Elevation Model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera

    Science.gov (United States)

    Barker, M. K.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Haruyama, J.; Smith, D. E.

    2015-01-01

    We present an improved lunar digital elevation model (DEM) covering latitudes within +/-60 deg, at a horizontal resolution of 512 pixels per degree ( approx.60 m at the equator) and a typical vertical accuracy approx.3 to 4 m. This DEM is constructed from approx.4.5 ×10(exp 9) geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1 deg×1 deg) from the SELENE Terrain Camera (TC) ( approx.10(exp 10) pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of < 5 m compared to approx.50% prior to co-registration. We use the co-registered TC data to estimate and correct orbital and pointing geolocation errors from the LOLA altimetric profiles (typically amounting to < 10 m horizontally and < 1 m vertically). By combining both co-registered datasets, we obtain a near-global DEM with high geodetic accuracy, and without the need for surface interpolation. We evaluate the resulting LOLA + TC merged DEM (designated as "SLDEM2015") with particular attention to quantifying seams and crossover errors.

  6. Stream-coordinate structure of oceanic jets based on merged altimeter data

    Institute of Scientific and Technical Information of China (English)

    SUN Che; ZHANG Linlin; YAN Xiaomei

    2011-01-01

    The jet structure of the Southern Ocean front south of Australia is studied in stream-coordinate with a new altimeter product--Absolute Dynamic Topography (ADT) from AVISO. The accuracy of the ADT data is validated with the mooring data from a two-year subantarctic-front experiment. It is demonstrated that the ADT is consistent with in-situ measurements and captures the meso-scale activity of the Antarctic Circumpolar Current (ACC). Stream-coordinate analysis of ADT surface geostrophic flows finds that ACC jets exhibit large spatio-temporal variability and do not correspond to particular streamfunction values. In the circumpolar scope ACC jets display a transient fragmented pattern controlled by topographic features. The poleward shift of jet in streamfunction space, as revealed by a streamwise correlation method, indicates the presence of meridional fluxes of zonal momentum. Such cross-stream eddy fluxes concentrate the broad ACC baroclinic flow into narrow jets. Combined with a recent discovery of gravest empirical mode (GEM) in the thermohaline fields, the study clarifies the interrelationship among front, jet and streamfunction in the Southern Ocean.

  7. A modified method to estimate eddy diffusivity in the North Pacific using altimeter eddy statistics

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhiwei; LI Yaru; TIAN Jiwei

    2013-01-01

    The method proposed by Stammer (1998) is modified using eddy statistics from altimeter observation to obtain more realistic eddy diffusivity (K) for the North Pacific.Compared with original estimates,the modified K has remarkably reduced values in the Kuroshio Extension (KE) and North Equatorial Counter Current (NECC) regions,but slightly enhanced values in the Subtropical Counter Current (STCC) region.In strong eastward flow areas like the KE and NECC,owing to a large difference between mean flow velocity and propagation velocity of mesoscale eddies,tracers inside the mesoscale eddies are transported outside rapidly by advection,and mixing length L is hence strongly suppressed.The low eddy probability (P) is also responsible for the reduced K in the NECC area.In the STCC region,however,L is mildly suppressed and P is very high,so K there is enhanced.The zonally-averaged K has two peaks with comparable magnitudes,in the latitude bands of the STCC and KE.In the core of KE,because of the reduced values of P and L,the zonally-averaged K is a minimum.Zonally-integrated eddy heat transport in the KE band,calculated based on the modified K,is much closer to the results of previous independent research,indicating the robustness of our modified K.The map of modified K provides useful information for modeling studies in the North Pacific.

  8. Estimates of global M2 internal tide energy fluxes using TOPEX/POSEIDON altimeter data

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yanwei; LIANG Xinfeng; TIAN Jiwei; YANG Lifen

    2009-01-01

    TOPEX/POSEIDON altimeter data from October 1992 to June 2002 are used to calculate the global barotropic M2 tidal currents using long-term tidal harmonic analysis. The tides calculated agree well with ADCP data obtained from the South China Sea (SCS). The maximum tide velocities along the semi-major axis and semi-minor axis can be computed from the tidal ellipse. The global distribution of M2 internal tide vertical energy flux from the sea bottom is calculated based on a linear internal wave generation model. The global vertical energy flux of M2 internal tide is 0.96 TW, with 0.36 TW in the Pacific, 0.31 TW in the Atlantic and 0.29 TW in the Indian Ocean, obtained in this study. The total horizontal energy flux of M2 internal tide radiating into the open ocean from the lateral boundaries is 0.13 TW, with 0.06 TW in the Pacific, 0.04TW in the Atlantic, and 0.03 TW in the Indian Ocean. The result shows that the principal lunar semi-diurnal tide M2 provides enough energy to maintain the large-scale thermohaline circulation of the ocean.

  9. A new lunar digital elevation model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera

    Science.gov (United States)

    Barker, M. K.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Haruyama, J.; Smith, D. E.

    2016-07-01

    We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512 pixels per degree (∼60 m at the equator) and a typical vertical accuracy ∼3 to 4 m. This DEM is constructed from ∼ 4.5 ×109 geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1° × 1°) from the SELENE Terrain Camera (TC) (∼1010 pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of profiles (typically amounting to <10 m horizontally and <1 m vertically). By combining both co-registered datasets, we obtain a near-global DEM with high geodetic accuracy, and without the need for surface interpolation. We evaluate the resulting LOLA + TC merged DEM (designated as "SLDEM2015") with particular attention to quantifying seams and crossover errors.

  10. 倍骼生在Ⅱ度根分叉病变治疗中的临床应用%Clinic Study of PerioGlas in the Treatment of Grade Ⅱ Furcation Involvement

    Institute of Scientific and Technical Information of China (English)

    梁晓敏; 李春阳

    2011-01-01

    Objective To observe the clinical effects of PerioGlas in the treatment of Grade Ⅱ furcation involvement.Methods Thirty-six teeth with Grade Ⅱ furcation involvement of 28 patients were selected. Four weeks after an initial therapy, they were randomly divided into two groups: PerioGlas group were treated with open flap debridement and graft of PerioGlas, and control group were treated with simple open flap debridement (OFD). Clinical indicators of periodontal were examinated before operation and 3, 6, 1 2 months after operation. At the same time, standardized reproducible periapical films were taken. Results In PerioGlas group, significant improvements of all indexes can be observed in the 3 months (P <0. 05 ), even the 6 and 12 months after operation ( P < 0. 001 ). In control group, PD, AL had significant difference (P <0. 05) at 3, 6 and 12 months after operation, HPD had improved, but without statistically significance (P>0.05). Comparing the two groups after operation, PD, AL and HPD in different time points had significant difference (P < 0. 05, P < 0. 001 ). Conclusion Better clinical efficacy was available when using PerioGlas in the treatment of Grade Ⅱ furcation involvement.%目的 探讨倍骼生在Ⅱ度根分叉病变治疗中的疗效.方法 28例经过牙周基础治疗患者的36颗Ⅱ度根分叉病变患牙,随机分为:试验组18颗,行翻瓣术联合倍骼生植入术;对照组18颗,单纯行翻瓣术.术前及术后3、 6、 12个月检查牙周临床指标并进行定位根尖片检查.结果 试验组牙周袋探诊深度(probing depth,PD)、附着丧失(attachment loss,AL)、根分叉水平探诊深度(horizontal probing depth,HPD)与基线比较,术后3个月(P0.05).2组术后各时间点比较,PD(P<0.05)、AL(P<0.05)和HPD(P<0.001)差异均有统计学意义.结论 应用倍骼生治疗Ⅱ度根分叉病变可获得比单纯翻瓣刮治更好的治疗效果.

  11. 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

  12. 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

  13. 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.

  14. Wind-driven circulation in the subarctic north Pacific using altimeter data

    Indian Academy of Sciences (India)

    Osamu Isoguchi; Hiroshi Kawamura

    2002-09-01

    Time-dependent wind-driven circulation in the subarctic north Pacific is investigated by using Topex/Poseidon (T/P) altimeter data and European Centre for Medium-Range Weather Forecasts (ECMWF) wind data for about 6 years. The first empirical orthogonal function (EOF) of the T/P- derived sea level anomaly (SLA) without the variation related to the steric height change (SLA1) and the first EOF of the ECMWF-based wind stress curl fields represent basin-sized south-north oscillations and their time series agree well with a correlation of 0.49. They appear to express the spin-up and spin-down of the subarctic gyre. The third EOF of SLA (SLA3) and the second EOF of the wind stress curl are also related to the variation of the subarctic gyre. Though the correlation of their time series is 0.27, drastic changes in early winter coincide well. The two EOF pairs can be considered to mean that the SLA variation followed by the latitudinal migration of the Aleutian low is separated into two standing oscillation patterns, that is, the sea level variation combined with SLA1 and SLA3 expresses seasonal variations of the wind-driven circulation of the subarctic gyre. The interannual SLAs constructed by subtracting the SLA1 and SLA3 components clearly show trans-pacific westward propagation even in the high-latitudes. The time series of SLA1 is in agreement with that of in situ SLAs measured with the tide gauge at Petropavlovsk (53-01N, 158-38E), which implies the possibility to monitor the subarctic circulation using tide gauge data.

  15. The development of the CHANG'`E-1 lunar explorer laser altimeter

    Science.gov (United States)

    Shu, R.; Wang, J. Y.; Hu, Y. H.; Jia, J. J.

    According to Chinese fable CHANG prime E is the name of a peri who lives in the moon with a white rabbit The CHANG prime E-1 lunar explorer will be launched in April 2007 The Lunar Explorer Laser Altimeter LELA is one of the 6 payloads in Chang prime E-1 which is developed by Shanghai Institute of Technical Physics Chinese Academy of Sciences The data of LELA will be used with the Optical Imager for acquiring the three dimension image of the moon surface The LELA transmits laser pulses determines their round trip times to the surface of the moon using a time interval counter and measures ranges between CHANG prime E-1 lunar explorer and the lunar surface in the nadir direction with 5m accuracy every 1 second for 1 year s mission period The acquired range data are transformed to the topography of the moon with the aid of position and attitude data of the CHANG prime E-1 lunar explorer obtained from the ground-based tracking and on board star sensor respectively The mean distances between Chang prime E-1 and the surface of moon is 200Km The LELA utilizes a laser diode LD pumped Q-switched Nd YAG laser that has a wavelength of 1064nm a pulse width of 10ns The output beam divergence is improved to 0 6mrad by Galileo refractor-type collimator which resulted in a moon surface spot size foot print of 120m The return pulses are captured by Cassegrain-type reflector and detected by Si-APD detector The prototype began from 2003 Until now the engineering model had been finished

  16. 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.

  17. 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

  18. 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....

  19. 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).

  20. Lunar phase function at 1064 nm from Lunar Orbiter Laser Altimeter passive and active radiometry

    Science.gov (United States)

    Barker, M. K.; Sun, X.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.

    2016-07-01

    We present initial calibration and results of passive radiometry collected by the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter over the course of 12 months. After correcting for time- and temperature-dependent dark noise and detector responsivity variations, the LOLA passive radiometry measurements are brought onto the absolute radiance scale of the SELENE Spectral Profiler. The resulting photometric precision is estimated to be ∼5%. We leverage the unique ability of LOLA to measure normal albedo to explore the 1064 nm phase function's dependence on various geologic parameters. On a global scale, we find that iron abundance and optical maturity (quantified by FeO and OMAT) are the dominant controlling parameters. Titanium abundance (TiO2), surface roughness on decimeter to decameter scales, and soil thermophysical properties have a smaller effect, but the latter two are correlated with OMAT, indicating that exposure age is the driving force behind their effects in a globally-averaged sense. The phase function also exhibits a dependence on surface slope at ∼300 m baselines, possibly the result of mass wasting exposing immature material and/or less space weathering due to reduced sky visibility. Modeling the photometric function in the Hapke framework, we find that, relative to the highlands, the maria exhibit decreased backscattering, a smaller opposition effect (OE) width, and a smaller OE amplitude. Immature highlands regolith has a higher backscattering fraction and a larger OE width compared to mature highlands regolith. Within the maria, the backscattering fraction and OE width show little dependence on TiO2 and OMAT. Variations in the phase function shape at large phase angles are observed in and around the Copernican-aged Jackson crater, including its dark halo, a putative impact melt deposit. Finally, the phase function of the Reiner Gamma Formation behaves more optically immature than is typical for its composition and OMAT

  1. Lunar Phase Function at 1064 Nm from Lunar Orbiter Laser Altimeter Passive and Active Radiometry

    Science.gov (United States)

    Barker, M. K.; Sun, X.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.

    2016-01-01

    We present initial calibration and results of passive radiometry collected by the Lunar Orbiter Laser Altimeter onboard the Lunar Reconnaissance Orbiter over the course of 12 months. After correcting for time- and temperature-dependent dark noise and detector responsivity variations, the LOLA passive radiometry measurements are brought onto the absolute radiance scale of the SELENE Spectral Profiler. The resulting photometric precision is estimated to be 5%. We leverage the unique ability of LOLA to measure normal albedo to explore the 1064 nm phase function's dependence on various geologic parameters. On a global scale, we find that iron abundance and optical maturity (quantified by FeO and OMAT) are the dominant controlling parameters. Titanium abundance (TiO2), surface roughness on decimeter to decameter scales, and soil thermo- physical properties have a smaller effect, but the latter two are correlated with OMAT, indicating that exposure age is the driving force behind their effects in a globally-averaged sense. The phase function also exhibits a dependence on surface slope at approximately 300 m baselines, possibly the result of mass wasting exposing immature material and/or less space weathering due to reduced sky visibility. Modeling the photometric function in the Hapke framework, we find that, relative to the highlands, the maria exhibit decreased backscattering, a smaller opposition effect (OE) width, and a smaller OE amplitude. Immature highlands regolith has a higher backscattering fraction and a larger OE width compared to mature highlands regolith. Within the maria, the backscattering fraction and OE width show little dependence on TiO2 and OMAT. Variations in the phase function shape at large phase angles are observed in and around the Copernican-aged Jackson crater, including its dark halo, a putative impact melt deposit. Finally, the phase function of the Reiner Gamma Formation behaves more optically immature than is typical for its composition

  2. Analysis of global static and time-dependent topography from laser altimeter data records using a rectangular-grid method

    Science.gov (United States)

    Koch, Ch.; Christensen, U. R.; Kallenbach, R.

    2008-09-01

    ABSTRACT BepiColombo is one of the cornerstone missions of ESA to investigate Mercury. The mission consists of two orbiters, one for studying Mercury's magnetosphere (MMO) and the other for investigating the planet itself (MPO). MPO includes the laser altimeter BELA whose main goals are the mapping of the long-wavelength topography and retrieving time-dependent variations of Mercury's surface. Due to its proximity to the Sun tidal elevations ofMercury's surface of order one meter are likely, if the planet's core is partly liquid. The tidal amplitude is characterized by the tidal Love number h2. Its quantity reveals information on the interior structure of Mercury such as the thickness of the liquid outer core. In previous simulations, Mercury's topography data from synthetic laser altimeter records have directly been decomposed into a spherical harmonic expansion. In this work, we test a decomposition of the data using a rectangular grid. In latitudinal direction, the basis functions are simple step functions which are only non-zero for a particular grid cell. In longitudinal direction, the basis functions are either step functions, linear functions, or more sophisticated interpolations. This choice of basis functions is well suited for the nearly polar orbit of MPO which makes laser shots very dense in latitudinal direction but less dense in longitudinal direction. We show first results on the extraction of the global topography and the tidal Love number h2.

  3. NODC Standard Product: US Navy Geosat altimeter T2 Geophysical Data Records for the Exact Repeat Mission (6 disc set) (NODC Accession 0053521)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This accession contains a copy of the NODC CD-ROM product titled US Navy Geosat altimeter T2 GDRs for the Exact Repeat Mission for the time period of November 08,...

  4. The Reflectivity of Mars at 1064 nm: Derivation from Mars Orbiter Laser Altimeter Data and Application to Climatology and Meteorology

    CERN Document Server

    Heavens, Nicholas G

    2016-01-01

    The Mars Orbiter Laser Altimeter (MOLA) on board Mars Global Surveyor (MGS) made $\\gg 10^{8}$ measurements of the reflectivity of Mars at 1064 nm ($R_{1064}$) by both active sounding and passive radiometry. Past studies of $R_{1064}$ neglected the effects of atmospheric opacity and viewing geometry on both active and passive measurements and also identified a potential calibration issue with passive radiometry. Therefore, as yet, there exists no acceptable reference $R_{1064}$ to derive a column opacity product from surface returns during active sounding for the purposes of atmospheric studies. Here, such a reference $R_{1064}$ is derived by seeking $R^{M,N}_{1064}$: a Minnaert-corrected normal albedo under clear conditions and assuming minimal phase angle dependence. Over darker surfaces, $R^{M,N}_{1064}$ and the absolute level of atmospheric opacity were estimated from active sounding. Over all surfaces, the opacity derived from active sounding were used to filter out the cloudiest passive radiometry measur...

  5. 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

  6. Low-amplitude topographic features and textures on the Moon: Initial results from detrended Lunar Orbiter Laser Altimeter (LOLA) topography

    Science.gov (United States)

    Kreslavsky, Mikhail A.; Head, James W.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.

    2017-02-01

    Global lunar topographic data derived from ranging measurements by the Lunar Oribter Laser Altimeter (LOLA) onboard LRO mission to the Moon have extremely high vertical precision. We use detrended topography as a means for utilization of this precision in geomorphological analysis. The detrended topography was calculated as a difference between actual topography and a trend surface defined as a median topography in a circular sliding window. We found that despite complicated distortions caused by the non-linear nature of the detrending procedure, visual inspection of these data facilitates identification of low-amplitude gently-sloping geomorphic features. We present specific examples of patterns of lava flows forming the lunar maria and revealing compound flow fields, a new class of lava flow complex on the Moon. We also highlight the identification of linear tectonic features that otherwise are obscured in the images and topographic data processed in a more traditional manner.

  7. Detailed 1 x 1 deg gravimetric Indian Ocean geoid and comparison with GEOS-3 radar altimeter geoid profiles

    Science.gov (United States)

    Kahle, H.-G.; Chapman, M.; Talwani, M.

    1978-01-01

    A new set of 1 x 1 deg mean free-air anomalies in the Indian Ocean is determined on the basis of previously published free-air anomaly maps (Talwani and Kahle, 1975) and the most recent Lamont surface ship gravity measurements. The data are then used to compute a (total) 1 x 1 deg gravimetric Indian Ocean geoid. The computation is carried out by combining the Goddard Space Flight Center (GSFC) GEM-6 geoid and a difference geoid that corresponds to the differences between the set of 1 x 1 deg surface gravity values and the GEM-6 gravity anomalies. The difference geoid is highest over the Madagascar Ridge (+20 m) and lowest over the Timor Trough (-30 m). The total geoid is compared with GEOS-3 radar altimeter-derived geoid profiles, and geophysical implications are discussed.

  8. 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.

  9. GFO and JASON Altimeter Engineering Assessment Report. Update: GFO--Acceptance to December 27, 2007, JASON--Acceptance to December 26, 2007. Version 1: June 2008

    Science.gov (United States)

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

    2008-01-01

    The purpose of this document is to present and document GEOSAT Follow-On (GFO) performance analyses and results. This is the eighth Assessment Report since the initial report. This report extends the performance assessment since acceptance to 27 December 2007. Since launch, a variety of GFO performance studies have been performed: 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 theTOPEX altimeter. With the end of the TOPEX mission, we developed methods to report on JASON as it relates to GFO.

  10. 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.

  11. 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

  12. Validating NASA's Airborne Multikilohertz Microlaser Altimeter (Microaltimeter) by Direct Comparison of Data Taken Over Ocean City, Maryland Against an Existing Digital Elevation Model

    Science.gov (United States)

    Abel, Peter

    2003-01-01

    NASA's Airborne Multikilohertz Microlaser Altimeter (Microaltimeter) is a scanning, photon-counting laser altimeter, which uses a low energy (less than 10 microJuoles), high repetition rate (approximately 10 kHz) laser, transmitting at 532 nm. A 14 cm diameter telescope images the ground return onto a segmented anode photomultiplier, which provides up to 16 range returns for each fire. Multiple engineering flights were made during 2001 and 2002 over the Maryland and Virginia coastal area, all during daylight hours. Post-processing of the data to geolocate the laser footprint and determine the terrain height requires post- detection Poisson filtering techniques to extract the actual ground returns from the noise. Validation of the instrument's ability to produce accurate terrain heights will be accomplished by direct comparison of data taken over Ocean City, Maryland with a Digital Elevation Model (DEM) of the region produced at Ohio State University (OSU) from other laser altimeter and photographic sources. The techniques employed to produce terrain heights from the Microaltimeter ranges will be shown, along with some preliminary comparisons with the OSU DEM.

  13. 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.

  14. 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...

  15. GRAVSAT error analysis by means of global spectral analyses of the marine geoid from SEASAT altimeter data

    Science.gov (United States)

    1982-01-01

    The geographical variability of short wavelength geoid power spectra (geoid roughness), was mapped for the world's oceans between latitudes 72 deg N and 72 deg S. A spectral analysis of SEASAT altimeter data, reduced to sea surface heights, was performed at 2 minute intervals for 15 consecutive days of the 3-day repeat orbit. The geoid roughness represented by these spectra for wavelengths shorter than about 220 km is separated from the total sea height variance and is displayed in the form of a global contour map. The global average geoid roughness is 32 cm RMS, varying from a high in excess of 2 m RMS near deep ocean trenches to a low of 2 cm RMS in the southeast Pacific near the East Pacific Rise. This average value agrees well with previous estimates based on gravimetry and GEOS-3 altimetry. In general, the smoothest areas in the marine geoid overlie relatively young seafloor adjacent mid-ocean spreading centers, where even short-wavelength topographic variations tend to be isostatically compensated.

  16. 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.

  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. 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.

  19. Characterizing Leaf Area Index (LAI and Vertical Foliage Profile (VFP over the United States

    Directory of Open Access Journals (Sweden)

    H. Tang

    2015-08-01

    Full Text Available Leaf area index (LAI and vertical foliage profile (VFP are among the important canopy structural variables. Recent advances in lidar remote sensing technology have demonstrated the capability of accurately mapping LAI and VFP over large areas. The primary objective of this study was to derive and validate a LAI and VFP product over the contiguous United States using spaceborne waveform lidar data. This product was derived at the footprint level from the Geoscience Laser Altimeter System (GLAS using a biophysical model. We validated GLAS derived LAI and VFP across major forest biomes using airborne waveform lidar. The comparison results showed that GLAS retrievals of total LAI were generally accurate with little bias (r2 = 0.67, bias = −0.13, RMSE = 0.75. The derivations of GLAS retrievals of VFP within layers was not as accurate overall (r2 = 0.36, bias = −0.04, RMSE = 0.26, and these varied as a function of height, increasing from understory to overstory −0 to 5 m layer: r2 = 0.04, bias = 0.09, RMSE = 0.31; 10 to 15 m layer: r2 = 0.53, bias = −0.08, RMSE = 0.22; and 15 to 20 m layer: r2 = 0.66, bias =−0.05, RMSE = 0.20. Significant relationships were also found between GLAS LAI products and different environmental factors, in particular elevation and annual precipitation. In summary, our results provide a unique insight into vertical canopy structure distribution across North American ecosystems. This data set is a first step towards a baseline of canopy structure needed for evaluating climate and land use induced forest changes at continental scale in the future and should help deepen our understanding of the role of vertical canopy structure on terrestrial ecosystem processes across varying scales.

  20. Characterizing leaf area index (LAI) and vertical foliage profile (VFP) over the United States

    Science.gov (United States)

    Tang, H.; Ganguly, S.; Zhang, G.; Hofton, M. A.; Nelson, R. F.; Dubayah, R.

    2016-01-01

    Leaf area index (LAI) and vertical foliage profile (VFP) are among the important canopy structural variables. Recent advances in lidar remote sensing technology have demonstrated the capability of accurately mapping LAI and VFP over large areas. The primary objective of this study was to derive and validate a LAI and VFP product over the contiguous United States (CONUS) using spaceborne waveform lidar data. This product was derived at the footprint level from the Geoscience Laser Altimeter System (GLAS) using a biophysical model. We validated GLAS-derived LAI and VFP across major forest biomes using airborne waveform lidar. The comparison results showed that GLAS retrievals of total LAI were generally accurate with little bias (r2 = 0.67, bias = -0.13, RMSE = 0.75). The derivations of GLAS retrievals of VFP within layers were not as accurate overall (r2 = 0.36, bias = -0.04, RMSE = 0.26), and these varied as a function of height, increasing from understory to overstory - 0 to 5 m layer: r2 = 0.04, bias = 0.09, RMSE = 0.31; 10 to 15 m layer: r2 = 0.53, bias = -0.08, RMSE = 0.22; and 15 to 20 m layer: r2 = 0.66, bias = -0.05, RMSE = 0.20. Significant relationships were also found between GLAS LAI products and different environmental factors, in particular elevation and annual precipitation. In summary, our results provide a unique insight into vertical canopy structure distribution across North American ecosystems. This data set is a first step towards a baseline of canopy structure needed for evaluating climate and land use induced forest changes at the continental scale in the future, and should help deepen our understanding of the role of vertical canopy structure in terrestrial ecosystem processes across varying scales.

  1. 激光雷达GLAS与ETM联合反演森林地上生物量研究%Estimation of Forest Aboveground Biomass by Integrating GLAS and ETM Data

    Institute of Scientific and Technical Information of China (English)

    董立新; 吴炳方; 唐世浩

    2011-01-01

    在实现大脚印激光雷达GLAS森林冠顶高度反演算法基础上,建立了复杂地形条件下森林地上生物量神经网络反演模型,制作了研究区森林地上生物量分布图。总体上,激光雷达GLAS森林冠顶高度和地上生物量估算精度较高。森林冠顶高度针叶林精度最好(R^2=0.692);阔叶林次之(R^2=0.5062);地上生物量反演结果与实测结果十分接近,在空间分布上与土地覆盖分布特征非常一致。更多还原%Based on the algorithm of forest canopy height for GLAS data,the neural net model of above ground biomass in complex terrain conditions was established.The map of forest aboveground biomass from BP neural net model was produced.Overall,forest canopy height and aboveground biomass have higher accuracy.The result of forest canopy height of needle-leaf forest has highest accuracy(R2=0.692).The result of broadleaf forest has higher accuracy(R2=0.5062).The results of forest aboveground biomass are very close to the fields measured results,and are consistent with land cover data in the spatial distribution.

  2. The global structure of the annual and semiannual sea surface height variability from Geosat altimeter data

    Science.gov (United States)

    Jacobs, Gregg A.; Born, George H.; Parke, Mike E.; Allen, Patrick C.

    1992-01-01

    Two years of data from the Geosat Exact Repeat Mission are employed to study the annual and semiannual variability of sea-surface height on a global basis. The data are treated with atmospheric corrections and interpolations, and the orbit error of about 40 cm RMS is purged. The spatial variability of the Geosat data is constructed for particular frequencies, and the estimate of the M2 tidal error indicates that the error is aliased to 1.15 cycles/yr and has an unusual spatial pattern. Sine and cosine coefficients are derived for the annual and semiannual frequencies by means of a least squares fit yielding the amplitude and phase of the changes in sea-surface height. A 180-deg phase difference is noted between the Northern and Southern Hemispheres for the annual variability, and large-scale westward propagating waves are identified. The Geosat data also indicate the phase relationships between major current systems and the systems of variations at work in the Intertropical Convergence Zone.

  3. The turnstile mechanism across the Kuroshio current: analysis of dynamics in altimeter velocity fields

    Science.gov (United States)

    Mendoza, C.; Mancho, A. M.; Rio, M.-H.

    2010-03-01

    In this article we explore the utility of dynamical systems tools for visualizing transport in oceanic flows described by data sets measured from satellites. In particular we have found the geometrical skeleton of some transport processes in the Kuroshio region. To this end we have computed the special hyperbolic trajectories, and identified them as distinguished hyperbolic trajectories, that act as organizing centres of the flow. We have computed their stable and unstable manifolds, and they reveal that the turnstile mechanism is at work during several spring months in the year 2003 across the Kuroshio current. We have found that near the hyperbolic trajectories takes place a filamentous transport front-cross the current that mixes waters from both sides.

  4. High-Speed Radiation Tolerant Avalanche Photodiodes Based on InGaN for Space Altimeter Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High-performance, radiation-tolerant detectors are required for the time-of-flight laser based rangefinders. Avalanche photodiodes (APDs) are conventionally chosen...

  5. Sealing of ceramic SOFC-components with glass seals; Fuegen von keramischen Komponenten der Hochtemperatur-Brennstoffzellen mittels Glas- und Glaskeramikloten

    Energy Technology Data Exchange (ETDEWEB)

    Schillig, Cora

    2012-07-10

    The solid oxide fuel cell (SOFC) converts chemical energy of a fuel directly into electrical energy. However, for the implementation of SOFC-technology in competition to conventional power plants costs have to be reduced. The use of an alternative tubular cell design without closed end would allow reducing costs during cell manufacturing. However, this change in design makes a gastight sealing inside the generator near the gas inlet necessary. Different ceramic materials with varying coefficients of thermal expansion have to be sealed gastight and electrical insulating at temperatures between 850 C and 1000 C to prevent the gases from mixing and an electrical shortcut between the cells. This work comprises analysis of commercially available glass and glass-ceramic systems manufactured by Schott Electronic Packaging, Areva T and D and Ferro Corporation. Additionally new developed sealing glass and glass-ceramic systems were investigated and all systems were characterized fundamentally for the use as sealing material in SOFC generators. Therefore different test assemblies and series were conducted. Essential characteristics of a suitable sealing system are a thermal expansion coefficient between 9,5 and 12 . 10{sup -6}K{sup -1}, a viscosity in the range between 10{sup 4} to 10{sup 6} dPa{sup *}s and a wetting angle smaller than 90 during the sealing process. Also unwanted chemical side reactions between the sealing partners must be prevented, because a change in the phase composition or the creation of new phases in the sealing material could endanger the stability of the seal. Heat cycles, particularly those during generator operation, cause deterioration of the sealing material and subsequent reduction in its ability to prevent mixing of the gases. Sealant leaks can drastically impact efficiency of the generator. In order to ensure optimum operation low leak rates around 2,3 . 10{sup -4} mbar l/sec/cm{sup 2} must be maintained. Especially glass and glass

  6. ICESat-Derived Elevation Changes on the Lena Delta and Laptev Sea, Siberia

    Science.gov (United States)

    Muskett, Reginald

    2014-05-01

    We employ elevation data from the Ice, Cloud, and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) to investigate surface changes across the Lena Delta and sea ice of the coastal Laptev Sea, Siberia during winters of 2003 through 2008. We compare ICESat GLAS-derived elevation changes on sea ice and the Bykovskaya and Sardakhskaya Channels with datum-corrected tide gauge height measurements from Danai, Sannikova and Tiksi stations. We find the coastal sea ice and large inland ice covered channels elevation changes are in phase with the tide-height changes on a same-month-year and datum controlled basis. Furthermore, we find elevation change on tundra drained lake basins to be +0.03 +/- 0.02 m, on average. These findings indicate ICESat GLAS is capable of detection of tide fluxes of ice covered coastal rivers and with a small error range is suitable for investigations of active-layer and permafrost dynamics associated with seasonal freezing (heave) and thawing (subsidence) using repeat-location profiles. Ref.: Muskett, R.R., "ICESat-Derived Elevation Changes on the Lena Delta and Laptev Sea, Siberia," Open Journal of Modern Hydrology, 4 (1), pp. 1-9, 2014. http://www.scirp.org/journal/PaperDownload.aspx?paperID=41709.

  7. Comparison of TOPEX/POSEIDON altimeter derived wave period with ocean buoy data in the East China Sea and South China Sea

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Altimeter wave period data obtained from continental shelf seas are analyzed in this paper.Empirical models are introduced for zero up-crossing and peak wave period calculation with TOPEX/POSEIDON data. Their performances are assessed using independent validation dataset in four sites in the open ocean of China. To provide more accurate wave period estimation, new coefficients are applied to reliable in situ data. Comparison of our estimated the wave periods with new linear calibrations based on independent data of Seapac 2100 deployed in the East China Sea and South China Sea showed that the accuracy was improved over estimates determined from earlier empirical models. Regional analysis indicated that the wave period model works better under wind sea condition.

  8. Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment

    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

    New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.

  9. Study on Multipath Suppressing Algorithm of Phase-coded Modulation Radar Altimeter%伪码调相雷达高度表中多径信号抑制算法研究

    Institute of Scientific and Technical Information of China (English)

    郭通; 廉保旺; 赵恒斌

    2011-01-01

    Multipath error is one of the most important errors in phase - coded modulation radar altimeter. In order to improve the measurement accuracy of system, this paper presents a code tracking loop model based on strobe correlator, and it also provides the block diagram of this model. The correlation of multipath parameters and the pseudo - code tracking error is analyzed when considering single multi - path signals, and some simulations of the code tracking loop performance are given in the Matlab environment. Simulation results show that the strobe correlator can effectively reduce the tracking error caused by multipath, and the performance is better than narrow correlator. This method is propitious to implement in hardware, because it needs less correlators.%多径误差是伪码调相雷达高度表中重要的误差源之一,为了提高系统的测距精度,建立了采用strobe相关器的伪码跟踪环数学模型,给出了其实现的结构框图;在考虑单路多径信号的基础上分析了多径信号的参数对伪码跟踪环的跟踪误差的影响,并在Matlab环境下对伪码跟踪环的跟踪性能进行了仿真;仿真结果表明在相同的多径参数条件下,strobe相关器可以有效地减小多径引起的跟踪误差,性能优于窄相关器,运算量较多径估计延迟锁定环要小,易于在硬件上实时实现,具有实际应用价值.

  10. Potential for Using Satellite Lidar for Seasonal Snow Depth Estimation

    Science.gov (United States)

    Jasinski, M. F.; Stoll, J.; Harding, D. J.; Fassnacht, S. R.; Carabajal, C. C.; Markus, T.

    2013-12-01

    This study evaluates the potential for estimating snow depth in complex mountainous terrain using high resolution satellite lidar. For over three decades, satellite remote sensing of snow depth and water equivalent has relied primarily on passive microwave sensors with an approximately 25 km footprint. While successfully employed in many global water balance analyses, their large footprints, necessary to capture the natural emission of the surface, are too coarse to define the spatial heterogeneity of mountain watershed-scale snow due to variable topography and vegetation. In this study, the capability of satellite lidar altimetry for estimating snow depth was evaluated primarily using surface elevations observed by the Geoscience Laser Altimeter Sensor (GLAS) flown on board the Ice, Cloud, and land Elevation Satellite from 2003-2009, with a footprint size of ~70m. The evaluation includes the analysis of GLAS waveforms at near-repeat locations during snow-off and snow on conditions, using several snow depth estimation approaches, focusing on the Uinta Mountains of NE Utah. Also presented is the concept for the ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS), currently set to launch in July 2016, and its potential capability for characterizing snow depth. The opportunity for partnering through NASA's Early Adopter Program using prototype aircraft observations also is presented.

  11. Global trends and vulnerabilities of mangrove forests

    Science.gov (United States)

    Simard, M.; Fatoyinbo, T. E.; Rivera-Monroy, V. H.; Castaneda, E.; Roy Chowdhury, R.

    2015-12-01

    Mangrove forests are located along Earth's coastlines and estuaries within tropical and subtropical latitudes. They provide numerous services functioning as an extraordinary carbon sequestration system and serving as habitat and nursery for fish, crustaceans and amphibians. To coastal populations, they provide livelihood, food, lumber and act as an effective protection against tsunamis, storm surges and hurricanes. Their vulnerability to sea level rise is strongly related to their extraordinary ability to accumulate soils, which is in part related to their productivity and therefore canopy structure. As a first step to understand their vulnerability, we seek to understand mangrove dependencies on environmental and geophysical setting. To achieve this, we mapped mangrove canopy height and above ground biomass (AGB) at the Global scale. To identify mangrove forests, existing maps derived from a collection of Landsat data around the 2000 era were used. Using the Shuttle Radar Topography Mission elevation data collected in February of 2000, we produced a Global map of mangrove canopy height. The estimated heights were validated with the ICESat/Geoscience Altimeter System (GLAS) and in situ field data. Most importantly, field data were also used to derive relationships between canopy height and AGB. While the geographical coverage of in situ data is limited, ICESat/GLAS data provided extensive geographical coverage with independent estimates of maximum canopy height. These estimates were used to calibrate SRTM-estimates of height at the Global scale. We found the difference between GLAS RH100 and SRTM resulted from several sources of uncertainty that are difficult to isolate. These include natural variations of canopy structure with time, system errors from GLAS and SRTM, geo-location errors and discrepancies in spatial resolution. The Global canopy height map was trnasormed into AGB using the field-derived allometry. Depending on the scale of analysis and geographical

  12. Døden på glas

    DEFF Research Database (Denmark)

    Meyer, Ion

    2008-01-01

    Artiklen beskriver den eneste danske samling af præparerede fostre og børn, og hvorfor den blev fremstillet. Den var en del af Museum Saxtorphianum og artiklen diskuterer hvordan disse fostre blev til præparater. Musealiseringen, overgangen fra medicinske studieobjekter til museumsgenstande med s...

  13. The transition from complex crater to peak-ring basin on the Moon: New observations from the Lunar Orbiter Laser Altimeter (LOLA) instrument

    Science.gov (United States)

    Baker, David M. H.; Head, James W.; Fassett, Caleb I.; Kadish, Seth J.; Smith, Dave E.; Zuber, Maria T.; Neumann, Gregory A.

    2011-08-01

    Impact craters on planetary bodies transition with increasing size from simple, to complex, to peak-ring basins and finally to multi-ring basins. Important to understanding the relationship between complex craters with central peaks and multi-ring basins is the analysis of protobasins (exhibiting a rim crest and interior ring plus a central peak) and peak-ring basins (exhibiting a rim crest and an interior ring). New data have permitted improved portrayal and classification of these transitional features on the Moon. We used new 128 pixel/degree gridded topographic data from the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter, combined with image mosaics, to conduct a survey of craters >50 km in diameter on the Moon and to update the existing catalogs of lunar peak-ring basins and protobasins. Our updated catalog includes 17 peak-ring basins (rim-crest diameters range from 207 km to 582 km, geometric mean = 343 km) and 3 protobasins (137-170 km, geometric mean = 157 km). Several basins inferred to be multi-ring basins in prior studies (Apollo, Moscoviense, Grimaldi, Freundlich-Sharonov, Coulomb-Sarton, and Korolev) are now classified as peak-ring basins due to their similarities with lunar peak-ring basin morphologies and absence of definitive topographic ring structures greater than two in number. We also include in our catalog 23 craters exhibiting small ring-like clusters of peaks (50-205 km, geometric mean = 81 km); one (Humboldt) exhibits a rim-crest diameter and an interior morphology that may be uniquely transitional to the process of forming peak rings. A power-law fit to ring diameters ( Dring) and rim-crest diameters ( Dr) of peak-ring basins on the Moon [ Dring = 0.14 ± 0.10( Dr) 1.21±0.13] reveals a trend that is very similar to a power-law fit to peak-ring basin diameters on Mercury [ Dring = 0.25 ± 0.14( Drim) 1.13±0.10] [Baker, D.M.H. et al. [2011]. Planet. Space Sci., in press]. Plots of ring

  14. 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.

  15. The meandering Gulf Stream as seen by the Geosat altimeter - Surface transport, position, and velocity variance from 73 deg to 46 deg W

    Science.gov (United States)

    Kelly, Kathryn A.

    1991-01-01

    Results are presented of an analysis of the surface geostrophic velocity field for the Gulf Stream region for the position, structure, and surface transport of the Gulf Stream for 2.5 yr of the Geosat altimeter Exact Repeat Mission. Synthetic data using a Gaussian velocity profile were generated and fit to the sea surface residual heights to create a synthetic mean sea surface height field and profiles of absolute geostrophic currents. An analysis of the model parameters and the actual geostrophic velocity profiles revealed two different flow regimes for the Gulf Stream connected by a narrow transition region coincident with the New England Seamount Chain. The upstream region was found to exhibit relatively straight Gulf Stream paths, long Eulerian time scales, and eastward propagating meanders. The downstream region had more large meanders, no consistent propagation direction, and shorter Eulerian time scales. A 25-percent reduction in surface transport occurred in the transition region, with a corresponding reduction in current speed and no change in Gulf Stream width.

  16. Global air-sea surface carbon dioxide transfer velocity and flux estimated using 17 a altimeter data and a new algorithm

    Institute of Scientific and Technical Information of China (English)

    YU Tan; HE Yijun; YAN Xiaohai

    2013-01-01

    The global distributions of the air-sea CO2 transfer velocity and flux are retrieved from TOPEX/Poseidon and Jason altimeter data from October 1992 to December 2009 using a combined algorithm. The 17 a average global, area-weighted, Schmidt number-corrected mean gas transfer velocity is 21.26 cm/h, and the full exploration of the uncertainty of this estimate awaits further data. The average total CO2 flux (calculated by carbon) from atmosphere to ocean during the 17 a was 2.58 Pg/a. The highest transfer velocity is in the circumpolar current area, because of constant high wind speeds and currents there. This results in strong CO2 fluxes. CO2 fluxes are strong but opposite direction in the equatorial east Pacific Ocean, because the air-sea CO2 partial pressure difference is the largest in the global oceans. The results differ from the previous studies calculated using the wind speed. It is demonstrated that the air-sea transfer velocity is very important for estimating air-sea CO2 flux. It is critical to have an accurate estimation for improving calculation of CO2 flux within climate change studies.

  17. Use of high frequency radiometer and altimeter on board AMSU-B, AMSR-E and Altika/SARAL for observations of the Antarctic ice sheet surface.

    Science.gov (United States)

    Adodo, Fifi; Picard, Ghislain; Remy, Frederique

    2016-04-01

    Snow surface properties quickly evolved according to local weather conditions, therefore are climate change indicator. These snow surface properties such as grain size, density, accumulation rate etc... are very important for evaluation and monitoring of the impact of global warming on the polar ice sheet. In order to retrieve these snowpack properties, we explore the high frequency microwave radiometer variable( Brightness Temperature (Tb)) on the Antarctic ice sheet on-board AMSU-B , AMSR-E in combination with the ALTIKA altimeter (37GHz) waveform parameters (Backscatter coefficient, Trailing edge Slope(TeS) and Leading edge Width(LeW)). We compare the radiometer brightness temperature to calculations with the DMRT- ML radiative transfer model which simulates brightness temperature in vertical and horizontal polarizations. With some assumptions, this combination allows a good retrieval of snowpack properties. We showed positive trend of the grains size on the Antarctic plateau especially at Dome C during the two last decades. This work will provide a higher accuracy of the estimation of snowpack surfaces properties and contribute to monitoring the ice sheet surface mass balance, well constraining of meteorological and glaciological models.

  18. 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.

  19. TOPEX高度计数据反演北太平洋海浪周期%Retrieving wave period of the North Pacific with TOPEX altimeter

    Institute of Scientific and Technical Information of China (English)

    李静凯; 周良明; 李水清

    2012-01-01

    利用TOPEX高度计和NDBC浮标同步观测数据,对7种高度计海浪周期反演模型进行了系统的比较分析,从反演模式的精度、反演周期整体分布、周期-波高的联合分布等方面对反演模型做出了评价,并根据墨西哥湾和夏威夷海域反演结果对模型的区域适应性进行了验证,结合Hasselmann风浪充分成长关系分析了不同海浪成分下模型的反演效果.分析发现,Mackay等于2008年提出的算法(简称M08)相对于其他算法精度最高,且在不同海域和不同海浪成分下精度没有明显差异.利用M08算法反演了北太平洋海域的海浪平均周期分布,讨论其空间分布特征和季节变化特征如下:北太平洋海域的平均周期在墨西哥湾、西里伯斯海等沿岸地区较小,在西风带海域为较大,并存在明显的地形、纬度差异和季节性变化特征.%This paper uses a collocated data set of the TOPEX altimeter and buoy measurements from NDBC to analyze the accuracy of seven models of wave period retrieval by altimeter up to the present and it compares these models with each other in the period distribution, period-significant wave height distribution and other aspects. And this paper also takes the effect of swell into consideration by comparing the precision between Gulf of Mexico and Hawaii sea area, between the upper part and under part of the wind-wave relation of fully developed sea line proposed by Hasselmann (1998) when using these models to retrieve zero up-cross wave period. In general, the accuracy of M08 algorithm of which RMS is only about 5.7s,higher than those of other algorithms and M08 algorithm also shows no obvious differences on different areas and situations. Then,this paper uses M08 algorithm to retrieve the mean wave period of the North Pacific and discusses its special distribution features and seasonal distribution features. Generally,the mean wave period of coastal areas of the North Pacific,such as the Gulf

  20. 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.

  1. Lessons Learned from Assimilating Altimeter Data into a Coupled General Circulation Model with the GMAO Augmented Ensemble Kalman Filter

    Science.gov (United States)

    Keppenne, Christian; Vernieres, Guillaume; Rienecker, Michele; Jacob, Jossy; Kovach, Robin

    2011-01-01

    Satellite altimetry measurements have provided global, evenly distributed observations of the ocean surface since 1993. However, the difficulties introduced by the presence of model biases and the requirement that data assimilation systems extrapolate the sea surface height (SSH) information to the subsurface in order to estimate the temperature, salinity and currents make it difficult to optimally exploit these measurements. This talk investigates the potential of the altimetry data assimilation once the biases are accounted for with an ad hoc bias estimation scheme. Either steady-state or state-dependent multivariate background-error covariances from an ensemble of model integrations are used to address the problem of extrapolating the information to the sub-surface. The GMAO ocean data assimilation system applied to an ensemble of coupled model instances using the GEOS-5 AGCM coupled to MOM4 is used in the investigation. To model the background error covariances, the system relies on a hybrid ensemble approach in which a small number of dynamically evolved model trajectories is augmented on the one hand with past instances of the state vector along each trajectory and, on the other, with a steady state ensemble of error estimates from a time series of short-term model forecasts. A state-dependent adaptive error-covariance localization and inflation algorithm controls how the SSH information is extrapolated to the sub-surface. A two-step predictor corrector approach is used to assimilate future information. Independent (not-assimilated) temperature and salinity observations from Argo floats are used to validate the assimilation. A two-step projection method in which the system first calculates a SSH increment and then projects this increment vertically onto the temperature, salt and current fields is found to be most effective in reconstructing the sub-surface information. The performance of the system in reconstructing the sub-surface fields is particularly

  2. Mesoscale ocean variability signal recovered from altimeter data in the SW Atlantic Ocean: a comparison of orbit error correction in three Geosat data sets

    Directory of Open Access Journals (Sweden)

    Gustavo Goni

    1995-01-01

    Full Text Available Orbit error is one of the largest sources of uncertainty in studies of ocean dynamics using satellite altimeters. The sensitivity of GEOSAT mesoscale ocean variability estimates to altimeter orbit precision in the SW Atlantic is analyzed using three GEOSAT data sets derived from different orbit estimation methods: (a the original GDR data set, which has the lowest orbit precision, (b the GEM-T2 set, constructed from a much more precise orbital model, and (c the Sirkes-Wunsch data set, derived from additional spectral analysis of the GEM-T2 data set. Differences among the data sets are investigated for two tracks in dynamically dissimilar regimes of the Southwestern Atlantic Ocean, by comparing: (a distinctive features of the average power density spectra of the sea height residuals and (b space-time diagrams of sea height residuals. The variability estimates produced by the three data sets are extremely similar in both regimes after removal of the time-dependent component of the orbit error using a quadratic fit. Our results indicate that altimeter orbit precision with appropriate processing plays only a minor role in studies of mesoscale ocean variability.Erro orbital tem sido a principal fonte de incerteza no processamento de dados altimétricos. Recentes conjuntos de dados, baseados em modelos de predição orbital mais avançados c em novas metodologias de correção de erro, já foram capazes de reduzir o erro orbital de ate uma ordem de magnitude em comparação com os GDRs originais. Ncslc trabalho nós avaliamos os resultados dessas melhores eslimativas na descrição da variabilidade "meso- escalar" na parte sudoeste do oceano Atlântico Sul. Comparamos resultados obtidos cm tres conjuntos de dados: os GDRs originais c os conjuntos de dados GEM-T2 c Sirkes-Wunsch. Para garantir a "sensibilidade" das estimativas dc variabilidade mcso-cscalar quanto às mudanças na precisão orbital, utilizamos as mesmas "correções ambientais" c o

  3. Aboveground biomass mapping in French Guiana by combining remote sensing, forest inventories and environmental data

    Science.gov (United States)

    Fayad, Ibrahim; Baghdadi, Nicolas; Guitet, Stéphane; Bailly, Jean-Stéphane; Hérault, Bruno; Gond, Valéry; El Hajj, Mahmoud; Tong Minh, Dinh Ho

    2016-10-01

    Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (>150 Mg/ha, and >300 Mg/ha for P-band), which are commonly found in tropical forests. Studies have mapped the rough variations in AGB by combining optical and environmental data at regional and global scales. Nevertheless, these maps cannot represent local variations in AGB in tropical forests. In this paper, we hypothesize that the problem of misrepresenting local variations in AGB and AGB estimation with good precision occurs because of both methodological limits (signal saturation or dilution bias) and a lack of adequate calibration data in this range of AGB values. We test this hypothesis by developing a calibrated regression model to predict variations in high AGB values (mean >300 Mg/ha) in French Guiana by a methodological approach for spatial extrapolation with data from the optical geoscience laser altimeter system (GLAS), forest inventories, radar, optics, and environmental variables for spatial inter- and extrapolation. Given their higher point count, GLAS data allow a wider coverage of AGB values. We find that the metrics from GLAS footprints are correlated with field AGB estimations (R2 = 0.54, RMSE = 48.3 Mg/ha) with no bias for high values. First, predictive models, including remote-sensing, environmental variables and spatial correlation functions, allow us to obtain "wall-to-wall" AGB maps over French Guiana with an RMSE for the in situ AGB estimates of ∼50 Mg/ha and R2 = 0.66 at a 1-km grid size. We conclude that a calibrated regression model based on GLAS with dependent environmental data can produce good AGB predictions even for high AGB values if the calibration data fit the AGB range. We also demonstrate that small temporal and spatial mismatches between field data and GLAS

  4. Study on global average colinear sea surface height based on Satelite Altimeter%基于卫星高度计的全球平均共线海表面高度研究

    Institute of Scientific and Technical Information of China (English)

    王鑫; 苗洪利

    2015-01-01

    Satelite altimeter can measure global ocean dynamic environment around the clock.The important data product is the sea surface height (SSH). In this paper we compute the SSH of al the points based on the satelite altimeter data. Then we use the reference orbit to colinear processing with SSH and average the result. Finaly we get the mean sea surface height (MSSH). This method can get the sea surface height information of different time ranges in a short period of time. And it can provide the data support for the long term change of sea level.%卫星高度计可以实现全球范围的全天候海洋动力环境测量,其中重要的数据产品为海表面高度(SSH)。本文基于高度计测量数据,计算出每个测量点的海表面高度。利用参考轨道对数据采用共线处理得到全球的平均共线海表面高度。这一方法可以在短时间内获得全球范围的不同时间尺度下的海表面高度信息,能够为海平面长期变化研究提供数据支持。

  5. Diode-pumped laser altimeter

    Science.gov (United States)

    Welford, D.; Isyanova, Y.

    1993-01-01

    TEM(sub 00)-mode output energies up to 22.5 mJ with 23 percent slope efficiencies were generated at 1.064 microns in a diode-laser pumped Nd:YAG laser using a transverse-pumping geometry. 1.32-micron performance was equally impressive at 10.2 mJ output energy with 15 percent slope efficiency. The same pumping geometry was successfully carried forward to several complex Q-switched laser resonator designs with no noticeable degradation of beam quality. Output beam profiles were consistently shown to have greater than 90 percent correlation with the ideal TEM(sub 00)-order Gaussian profile. A comparison study on pulse-reflection-mode (PRM), pulse-transmission-mode (PTM), and passive Q-switching techniques was undertaken. The PRM Q-switched laser generated 8.3 mJ pulses with durations as short as 10 ns. The PTM Q-switch laser generated 5 mJ pulses with durations as short as 5 ns. The passively Q-switched laser generated 5 mJ pulses with durations as short as 2.4 ns. Frequency doubling of both 1.064 microns and 1.32 microns with conversion efficiencies of 56 percent in lithium triborate and 10 percent in rubidium titanyl arsenate, respectively, was shown. Sum-frequency generation of the 1.064 microns and 1.32 microns radiations was demonstrated in KTP to generate 1.1 mJ of 0.589 micron output with 11.5 percent conversion efficiency.

  6. Precise GPS/GNSS Positioning Solution for Airborne Data Acquisition Systems

    Institute of Scientific and Technical Information of China (English)

    B. G. Gerlach; D. Gondy

    2003-01-01

    The precise positioning of aircrafts during flights belongs to the great challenges with respect to the development of airborne data acquisition systems. Satellite positioning systems like GPS offers a unique capability for precise positioning but requires in depth knowledge of GPS in airborne applications, e.g.GPS for high dynamic application, integration of GPS with other sensors, dynamic behaviour of aircrafts or antenna location. For its positioning reference system of Flight Inspection systems Aerodata AG has developed a robust GPS carrier phase ambiguity solution P-DGPS, Precise Differential GPS combined with complementary sensors like INS, barometers, radio altimeters or laser altimeters as well as laser trackers. Using recorded data during the flight the algorithm offers also the capability to calculate more accurate positions in post-processing. The presented sensor fusion algorithm using GPS without differential corrections (SGPS, standalone GPS) offers a precise height reference solution for approach calibration based only on aircraft-based sensors. SGPS data are combined in post-processing with inertial, pressure, radio and laser altimeter data. Flight trials with a Bombardier "Global Express" at Braunschweig Airport on May 2002 shows the achieved accuracies of the height reference solution calculated by SGPS in comparison to P-DGPS. The SGPS solution for precise height calculation of special mission aircrafts provides accuracies in the order of 5 m and at the runway's threshold in the order of 30 cm.

  7. ASPIS, A Flexible Multispectral System for Airborne Remote Sensing Environmental Applications

    Directory of Open Access Journals (Sweden)

    Riccardo Valentini

    2008-05-01

    Full Text Available Airborne multispectral and hyperspectral remote sensing is a powerful tool for environmental monitoring applications. In this paper we describe a new system (ASPIS composed by a 4-CCD spectral sensor, a thermal IR camera and a laser altimeter that is mounted on a flexible Sky-Arrow airplane. A test application of the multispectral sensor to estimate durum wheat quality is also presented.

  8. Instruments and Methods: A Low-Cost Glacier-Mapping System

    DEFF Research Database (Denmark)

    Christensen, Erik Lintz; Reeh, Niels; Forsberg, René;

    2000-01-01

    the capability of acquiring accurate data on location and ice-surface elevation, and adequate-quality data on ice thickness. The system has been applied successfully in mapping the Nioghalvfjerdsfjorden glacier, northeast Greenland, in spite of the difficult conditions with melting water on the glacier surface....... The measurements from the floating part of the glacier have been evaluated by comparison of radar data with laser-altimeter and in situ measurements....

  9. Allometric Scaling and Resource Limitations Model of Tree Heights: Part 1. Model Optimization and Testing over Continental USA

    Directory of Open Access Journals (Sweden)

    Ramakrishna R. Nemani

    2013-01-01

    Full Text Available A methodology to generate spatially continuous fields of tree heights with an optimized Allometric Scaling and Resource Limitations (ASRL model is reported in this first of a multi-part series of articles. Model optimization is performed with the Geoscience Laser Altimeter System (GLAS waveform data. This methodology is demonstrated by mapping tree heights over forested lands in the continental USA (CONUS at 1 km spatial resolution. The study area is divided into 841 eco-climatic zones based on three forest types, annual total precipitation classes (30 mm intervals and annual average temperature classes (2 °C intervals. Three model parameters (area of single leaf, α, exponent for canopy radius, η, and root absorption efficiency, γ were selected for optimization, that is, to minimize the difference between actual and potential tree heights in each of the eco-climatic zones over the CONUS. Tree heights predicted by the optimized model were evaluated against GLAS heights using a two-fold cross validation approach (R2 = 0.59; RMSE = 3.31 m. Comparison at the pixel level between GLAS heights (mean = 30.6 m; standard deviation = 10.7 and model predictions (mean = 30.8 m; std. = 8.4 were also performed. Further, the model predictions were compared to existing satellite-based forest height maps. The optimized ASRL model satisfactorily reproduced the pattern of tree heights over the CONUS. Subsequent articles in this series will document further improvements with the ultimate goal of mapping tree heights and forest biomass globally.

  10. 基于星载激光雷达数据和支持向量分类机方法的森林类型识别1)%Forest Type Identification with Spaceborne LIDAR Data and C-Suppro t VectorC lassification

    Institute of Scientific and Technical Information of China (English)

    刘美爽; 邢艳秋; 李立存; 杨超; 王蕊

    2014-01-01

    InWangqing area of Changbai Mountains, the investigation was conducted to analyze the capability of the ICESat-GLAS (Ice, Cloud and Land Elevation Satellite-Geoscience Laser Altimeter System) data on the forest type identification. The original binary ICESat-GLAS data was processed to obtain waveforms by MATLAB and IDL.The GLAS waveform met-rics were derived as the input dataset of C-Support Vector Classification method (C-SVC) for forest type identification, and the kernel function selection was evaluated using K-fold cross-validation method.The C-SVC method is capable to classify broadleaf and coniferous forests with the accuracy of 85 .24%.%以长白山汪清林区为例,分析了星载激光雷达( ICESat-GLAS)数据在森林类型识别上的应用效果。采用软件Matlab和IDL对原始二进制数据进行处理,得到GLAS回波波形图;进一步提取与森林类型相关的波形特征参数,作为支持向量分类机( C-SVC)的输入量,进行森林类型识别,并采用K-折交叉验证方法对核函数选择进行评价。结果表明:C-SVC分类方法能够识别阔叶林和针叶林2种森林类型,识别精度达到85.24%。

  11. Climate and Edaphic Controls on Humid Tropical Forest Tree Height

    Science.gov (United States)

    Yang, Y.; Saatchi, S. S.; Xu, L.

    2014-12-01

    Uncertainty in the magnitude and spatial variations of forest carbon density in tropical regions is due to under sampling of forest structure from inventory plots and the lack of regional allometry to estimate the carbon density from structure. Here we quantify the variation of tropical forest structure by using more than 2.5 million measurements of canopy height from systematic sampling of Geoscience Laser Altimeter System (GLAS) satellite observations between 2004 to 2008 and examine the climate and edaphic variables influencing the variations. We used top canopy height of GLAS footprints (~ 0.25 ha) to grid the statistical mean and 90 percentile of samples at 0.5 degrees to capture the regional variability of large trees in tropics. GLAS heights were also aggregated based on a stratification of tropical regions using soil, elevation, and forest types. Both approaches provided consistent patterns of statistically dominant large trees and the least heterogeneity, both as strong drivers of distribution of high biomass forests. Statistical models accounting for spatial autocorrelation suggest that climate, soil and spatial features together can explain more than 60% of the variations in observed tree height information, while climate-only variables explains about one third of the first-order changes in tree height. Soil basics, including physical compositions such as clay and sand contents, chemical properties such as PH values and cation-exchange capacity, as well as biological variables such as organic matters, all present independent but statistically significant relationships to tree height variations. The results confirm other landscape and regional studies that soil fertility, geology and climate may jointly control a majority of the regional variations of forest structure in pan-tropics and influencing both biomass stocks and dynamics. Consequently, other factors such as biotic and disturbance regimes, not included in this study, may have less influence on

  12. Scaling estimates of vegetation structure in Amazonian tropical forests using multi-angle MODIS observations

    Science.gov (United States)

    Moura, Yhasmin Mendes de; Hilker, Thomas; Gonçalves, Fabio Guimarães; Galvão, Lênio Soares; dos Santos, João Roberto; Lyapustin, Alexei; Maeda, Eduardo Eiji; de Jesus Silva, Camila Valéria

    2016-10-01

    Detailed knowledge of vegetation structure is required for accurate modelling of terrestrial ecosystems, but direct measurements of the three dimensional distribution of canopy elements, for instance from LiDAR, are not widely available. We investigate the potential for modelling vegetation roughness, a key parameter for climatological models, from directional scattering of visible and near-infrared (NIR) reflectance acquired from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS). We compare our estimates across different tropical forest types to independent measures obtained from: (1) airborne laser scanning (ALS), (2) spaceborne Geoscience Laser Altimeter System (GLAS)/ICESat, and (3) the spaceborne SeaWinds/QSCAT. Our results showed linear correlation between MODIS-derived anisotropy to ALS-derived entropy (r2 = 0.54, RMSE = 0.11), even in high biomass regions. Significant relationships were also obtained between MODIS-derived anisotropy and GLAS-derived entropy (0.52 ≤ r2 ≤ 0.61; p < 0.05), with similar slopes and offsets found throughout the season, and RMSE between 0.26 and 0.30 (units of entropy). The relationships between the MODIS-derived anisotropy and backscattering measurements (σ0) from SeaWinds/QuikSCAT presented an r2 of 0.59 and a RMSE of 0.11. We conclude that multi-angular MODIS observations are suitable to extrapolate measures of canopy entropy across different forest types, providing additional estimates of vegetation structure in the Amazon.

  13. Impact of Cloud and Blowing Snow on Ice Sheet Altimetry: a Comparison between ICESat and ICESat-2

    Science.gov (United States)

    Yang, Y.; Marshak, A.; Palm, S. P.; Varnai, T.

    2015-12-01

    Clouds and blowing snow have long been a concern for lidar altimetry. Scattering inside the layer increases the photon path and makes the surface appear further away from the satellite. This effect is referred to as "atmospheric path delay". The ICESat and ICESat-2 missions' high accuracy requirement on the ice/snow surface elevation measurements makes understanding and quantifying this effect essential. We have developed a comprehensive framework that can simulate the analog waveform behavior of the Geoscience Laser Altimeter System (GLAS) onboard ICESat and the photon counting signal of the Advanced Topographic Laser Altimeter System (ATLAS) onboard ICESat-2. In this presentation, we will (1) review the cloud and blowing snow distributions over the polar ice sheets; (2) discuss how different factors affect the value of the atmospheric path delay, such as scattering layer height, optical thickness, and lidar field of view (FOV); (3) demonstrate that the delay is much less for ICESat-2 (centimeter level) compared to ICESat (decimeter level) due to the much smaller lidar FOV; (4) show the cloud detectability difference between ICESat and ICESat-2 and its implication to path delay corrections. The effect of cloud and blowing snow on first photon bias will also be discussed.

  14. Absolute and relative height-pixel accuracy of SRTM-GL1 over the South American Andean Plateau

    Science.gov (United States)

    Satge, Frédéric; Denezine, Matheus; Pillco, Ramiro; Timouk, Franck; Pinel, Sébastien; Molina, Jorge; Garnier, Jérémie; Seyler, Frédérique; Bonnet, Marie-Paule

    2016-11-01

    Previously available only over the Continental United States (CONUS), the 1 arc-second mesh size (spatial resolution) SRTM-GL1 (Shuttle Radar Topographic Mission - Global 1) product has been freely available worldwide since November 2014. With a relatively small mesh size, this digital elevation model (DEM) provides valuable topographic information over remote regions. SRTM-GL1 is assessed for the first time over the South American Andean Plateau in terms of both the absolute and relative vertical point-to-point accuracies at the regional scale and for different slope classes. For comparison, SRTM-v4 and GDEM-v2 Global DEM version 2 (GDEM-v2) generated by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) are also considered. A total of approximately 160,000 ICESat/GLAS (Ice, Cloud and Land Elevation Satellite/Geoscience Laser Altimeter System) data are used as ground reference measurements. Relative error is often neglected in DEM assessments due to the lack of reference data. A new methodology is proposed to assess the relative accuracies of SRTM-GL1, SRTM-v4 and GDEM-v2 based on a comparison with ICESat/GLAS measurements. Slope values derived from DEMs and ICESat/GLAS measurements from approximately 265,000 ICESat/GLAS point pairs are compared using quantitative and categorical statistical analysis introducing a new index: the False Slope Ratio (FSR). Additionally, a reference hydrological network is derived from Google Earth and compared with river networks derived from the DEMs to assess each DEM's potential for hydrological applications over the region. In terms of the absolute vertical accuracy on a global scale, GDEM-v2 is the most accurate DEM, while SRTM-GL1 is more accurate than SRTM-v4. However, a simple bias correction makes SRTM-GL1 the most accurate DEM over the region in terms of vertical accuracy. The relative accuracy results generally did not corroborate the absolute vertical accuracy. GDEM-v2 presents the lowest statistical

  15. Design of Vehicle Electronic Altitude System%车载电子海拔高度系统设计

    Institute of Scientific and Technical Information of China (English)

    唐钧山

    2014-01-01

    The electronic altitude altimeter is a new product produced along with the development of science and technology. Compared with the traditional mechanical altimeter, it has obvious advantages,such as better consistency, wider measuring range and temperature environment, high reliability,high sensitivity and high resolution. At the same time,the showing result is more intuitive, and has the advantages of low cost. Based on these characteristics, the use of electronic altimeter conforms to its technological development trend. This article details the design method of vehicle electronic altitude system.%电子海拔高度表,是一种随着科技发展而诞生的新兴产物。与传统的机械式高度表相比,具有明显优点,如一致性更好,测量范围和温度环境更宽,可靠性高、灵敏度和分辨率高等。同时,其显示结果更为直观,且具有成本低的优势。基于这些特点,采用电子式高度表更符合其技术发展趋势。本文详细介绍了车载用电子海拔高度系统的设计方法。

  16. Jezična analiza lista Naš glas

    OpenAIRE

    2015-01-01

    U radu se analizira jezik Našega glasa (list „Riviere“ – radne organizacije za ugostiteljstvo, turizam, trgovinu i proizvodnju) koji je izlazio u Poreču od 1969. do 1982. godine. Nakon kratkoga osvrta na strukturu, sadržaj i ulogu toga lista te njegov značaj za stanovništvo lokalne zajednice, slijedi prikaz jezičnih zbivanja u vrijeme njegova izlaženja. U žarištu su istraživanja pravopisne, morfološke, sintaktičke, tvorbene, leksičke i stilske karakteristike lista. Rezultati istraživanja poka...

  17. Eindrapportage gele rozeluis in de teelt van aardbei onder glas

    NARCIS (Netherlands)

    Bloemhard, C.M.J.; Linden, van der A.

    2008-01-01

    Van de vele soorten bladluizen die op aardbei kunnen voorkomen is de gele rozeluis Rhodobium porosum het moeilijkst chemisch te bestrijden. Dit onderzoek richt zich op de biologische bestrijding van de luis met natuurlijke vijanden als de sluipwespen, gaas en zweefvliegen en insectpathogene schimmel

  18. 用于月球着陆的激光高度计热控设计探讨%Optimization of thermal control design for laser altimeter used during lunar landing

    Institute of Scientific and Technical Information of China (English)

    宋馨; 张有为; 贾建军; 刘自军

    2014-01-01

    The Land-On-Moon Orbit has obvious transient characteristics. The optimization principle of the thermal control design plan for the laser equipment used on the Land-On-Moon Orbit is discussed through the thermal analysis. The best thermal control design plan is to use the heat capacity of the equipment, unless the laser equipment is required to operate for a long time. An application case is the thermal control design plan for the laser altimeter used on the Chang’e-3, which uses the heat capacity of the equipment. The remote measurement data show that the temperature restriction of the equipment is realized. The thermal control design method is shown to be practical.%文章对落月轨道的外热流进行了分析,比较了几种热控设计方案的优缺点,探讨了热控优化设计的原则,认为在落月轨道上激光设备的热控设计应首选热容热控方案,对于在其他飞行阶段有长期开机需求的情况再考虑散热面方案或热电致冷方案。“嫦娥三号”月面探测器激光高度计采用了热容热控设计,该设备热控设计能够满足不同阶段温度指标要求并且与热分析结果相一致,热控设计方案正确、优化原则合理可行。

  19. 高速铁路CPⅢ高程控制网测量方法研究%Methods to derive lunar DEM from Chang'E-1 laser altimeter data

    Institute of Scientific and Technical Information of China (English)

    李书亮; 刘成龙; 倪先桃; 徐小左

    2011-01-01

    本文分析高速铁路CPⅢ高程控制网建网时普遍采用的德国测量方法,指出其存在的不足,在此基础上提出了技术上更为合理又适合我国国情的矩形法测量方法.通过对矩形法相邻点高差相对中误差和最弱点高程中误差的估算以及实验验证,认为矩形法可以用于CPⅢ高程网的建网测量.研究结果对于目前高速铁路工程测量相关规范的制订和在建高速铁路CPⅢ高程网的测量具有重要的参照价值.%High-resolution digital elevation models (DEMs) based on data from Laser Altimeter (LAM) of Chinese Chang'E-1 mission provide geospatial characterizations of lunar topography. The primary LAM elevation data are two-dimensional topographic profiles. Developing three-dimensional DEMs from these profile data requires the elimination of gross errors and the interpolation of a confinuous surface. To detect and remove the error ( pseudo elevation) data from LAM observations the paper suggested an improved linear filter based on empirical formula which adapts the lunar surface feature. And the key parameters for this filter were discussed. In the second part, it tested eight different techniques of spatial interpolation with the filtered data. After comparing and analyzing these interpolation methods by their accuracies, shaded-relief visualizations and topographic profiles, it found the Kriging method worked better than other seven methods in deriving DEM grid. At last, an effective procedure for processing CE-1 elevation data was outlined, and the corresponding parameters were suggested.

  20. Extraction of Significant Wave Height and Its Accuracy Analysis Based on HY-2 Altimeter Calibration Flight Data%基于HY-2卫星高度计机载校飞数据的有效波高信息提取及初步分析

    Institute of Scientific and Technical Information of China (English)

    李秀仲; 张有广; 孟俊敏

    2012-01-01

    利用HY-2卫星雷达高度计校飞数据,开展了有效波高信息提取及精度比对研究.首先对其进行波形筛选、1 s平均和去噪,然后基于Hayne海面回波模型进行波形拟合,提取出波高均方根并得到有效波高,并与浮标和同轨迹的Jason-1卫星高度计有效波高进行了比较.结果表明,本次校飞其高度计测波精度存在系统偏差,初步分析可能是其数据未经仪器校正等原因导致.%Based on the HY-2 calibration flight data, the significant wave height (SWH) is retrieved and its accuracy is compared with those from buoys and Jason-1 altimeter. For the extraction of the root mean square (RMS) of the wave heights and hence to obtain the SWH, first is to carry out waveform screening, averaging over 1 second and destriping, and then to make waveform fitting according to the Hayne echo model. The significant wave heights thus obtained are compared with those from the buoys and the Jason-1 altimeter which runs along the same track as that of the HY-2 calibration flight. The results indicate that a systematic bias is present for the accuracy of the SWH resulted from the HY-2 altimeter. This bias is mainly due to the absence of instrumental correction.

  1. Lunar landing and launch facilities (Complex 39L): Guidance systems and propellant systems

    Science.gov (United States)

    1989-01-01

    After a general, overall definition of Complex 39L during the previous two years, the 1988-89 projects were chosen to focus on more specific aspects, specifically, guidance systems and propellant systems. Six teams or subtasks were formulated: cascade refrigeration for boil-off recovery of cryogenic storage vessels; lunar ground-based radar system to track space vehicles; microwave altimeter for spacecraft; development of a computational model for the determination of lunar surface and sub-surface temperatures; lunar cryogenic facility for the storage of fuels; and lunar lander fuel inventory tent for the storage of cryogenic vessels. At the present time, a cascade refrigeration system for a cryogenic boil-off recovery system has been designed. This is to serve as a baseline system. The ground-based tracking system uses existing technology to implement a reliable tracking radar for use on the lunar surface. A prototype has been constructed. The microwave altimeter is for use on lunar landers. It makes use of the Doppler effect to measure both altitude and the vertical velocity component of the spacecraft. A prototype has been constructed. A computational model that predicts the spatial and temporal temperature profiles of the lunar subsurface was formulated. Propellant storage vessels have been designed. A support for these vessels which minimizes heat leaks was also designed. Further work on the details of the Fuel Inventory Tent (FIT) was performed. While much design work on the overall Complex 39L remains to be done, significant new work has been performed in the subject areas.

  2. Simulation of UAV Systems

    Directory of Open Access Journals (Sweden)

    P. Kaňovský

    2005-01-01

    Full Text Available The study described in this paper deals with the issue of a design tool for the autopilot of an Unmanned Aerial Vehicle (UAV and the selection of the airdata and inertial system sensors. This project was processed in cooperation with VTUL a PVO o.z. [1]. The feature that distinguishes the autopilot requirements of a UAV (Figs. 1, 7, 8 from the flight systems of conventional manned aircraft is the paradox of controlling a high bandwidth dynamical system using sensors that are in harmony with the low cost low weight objectives that UAV designs are often expected to achieve. The principal function of the autopilot is flight stability, which establishes the UAV as a stable airborne platform that can operate at a precisely defined height. The main sensor for providing this height information is a barometric altimeter. The solution to the UAV autopilot design was realised with simulations using the facilities of Matlab® and in particular Simulink®[2]. 

  3. A high success rate full-waveform lidar echo decomposition method

    Science.gov (United States)

    Xu, Lijun; Li, Duan; Li, Xiaolu

    2016-01-01

    A full-waveform Light detection and ranging (LiDAR) echo decomposition method is proposed in this paper. In this method, the peak points are used to detect the separated echo components, while the inflection points are combined with corresponding peak points to detect the overlapping echo components. The detected echo components are then sorted according to their energies in a descending order. The sorted echo components are one by one added into the decomposition model according to their orders. For each addition, the parameters of all echo components already added into the decomposition model are iteratively renewed. After renewing, the amplitudes and full width at half maximums of the echo components are compared with pre-set thresholds to determine and remove the false echo components. Both simulation and experiment were carried out to evaluate the proposed method. In simulation, 4000 full-waveform echoes with different numbers and parameters of echo components were generated and decomposed using the proposed and three other commonly used methods. Results show that the proposed method is of the highest success rate, 91.43%. In experiment, 9549 Geoscience Laser Altimeter System (GLAS) echoes for Shennongjia forest district in south China were employed as test echoes. The test echoes were first decomposed using the four methods and the decomposition results were also compared with those provided by the National Snow and Ice Data Center. Comparison results show that the determination coefficient ({{R}2} ) of the proposed method is of the largest mean, 0.6838, and the smallest standard deviation, 0.3588, and the distribution of the number of the echo components decomposed from the GLAS echoes is the most satisfied with the situation of full-waveform echoes from the forest area, implying that the superposition of the echo components decomposed from a full-waveform echo by using the proposed method can best approximate the full-waveform echo.

  4. Snow and Ice Products from the Aqua, Terra, and ICESat Satellites at the National Snow and Ice Data Center

    Science.gov (United States)

    Meier, W. N.; Marquis, M.; Kaminski, M.; Armstrong, R.; Brodzik, M.

    2004-05-01

    The National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder - one of eight NASA Distributed Active Archive Centers (DAACs) - archives and distributes several products from sensors on the suite of NASA Earth Observing System (EOS) satellites. These include the sun-synchronous polar-orbiting Aqua (launched 4 May 2002) and Terra (launched 18 December 1999) platforms and the Ice, Cloud, and land Elevation Satellite (ICESat) (launched 12 January 2003). The Advanced Microwave Scanning Radiometer-EOS (AMSR-E) is a multi-channel passive microwave radiometer on Aqua (http://nsidc.org/daac/amsr/). AMSR-E Level 3 snow products are produced in EASE-Grid format for both the Northern and Southern Hemisphere and are available as daily, 5-day, and monthly fields. Daily AMSR-E Level 3 sea ice products are produced on a polar stereographic projection at gridded spatial resolutions of 6.25 km, 12.5 km and 25 km. Since April 2004, these products have been available for public distribution from NSIDC. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua is a 36-channel visible/infrared sensor that produces a consistent long-term time series of fully-automated, quality-controlled data. Level 2 swath products are available for both snow cover and sea ice. Daily and 8-day Level 3 gridded snow cover products are available with estimates of snow extent and albedo at 500m resolution, along with daily Level 3 gridded sea ice products with estimates for sea ice extent and ice surface temperature at 1 km resolution. These products are currently available from NSIDC (http://nsidc.org/daac/modis/). The Geoscience Laser Altimeter System (GLAS) is the sole instrument on ICESat. The standard GLAS Level 2 ice sheet altimetry product contains the ice sheet elevation and elevation distribution calculated from algorithms fine-tuned for ice sheet returns. The standard GLAS Level 2 sea ice altimetry product contains the sea ice freeboard and sea ice

  5. A desktop system of virtual morphometric globes for Mars and the Moon

    Science.gov (United States)

    Florinsky, I. V.; Filippov, S. V.

    2017-03-01

    Global morphometric models can be useful for earth and planetary studies. Virtual globes - programs implementing interactive three-dimensional (3D) models of planets - are increasingly used in geo- and planetary sciences. We describe the development of a desktop system of virtual morphometric globes for Mars and the Moon. As the initial data, we used 15'-gridded global digital elevation models (DEMs) extracted from the Mars Orbiter Laser Altimeter (MOLA) and the Lunar Orbiter Laser Altimeter (LOLA) gridded archives. For two celestial bodies, we derived global digital models of several morphometric attributes, such as horizontal curvature, vertical curvature, minimal curvature, maximal curvature, and catchment area. To develop the system, we used Blender, the free open-source software for 3D modeling and visualization. First, a 3D sphere model was generated. Second, the global morphometric maps were imposed to the sphere surface as textures. Finally, the real-time 3D graphics Blender engine was used to implement rotation and zooming of the globes. The testing of the developed system demonstrated its good performance. Morphometric globes clearly represent peculiarities of planetary topography, according to the physical and mathematical sense of a particular morphometric variable.

  6. Deriving Leaf Area Index (LAI) from multiple lidar remote sensing systems

    Science.gov (United States)

    Tang, H.; Dubayah, R.; Zhao, F.

    2012-12-01

    LAI is an important biophysical variable linking biogeochemical cycles of earth systems. Observations with passive optical remote sensing are plagued by saturation and results from different passive and active sensors are often inconsistent. Recently lidar remote sensing has been applied to derive vertical canopy structure including LAI and its vertical profile. In this research we compare LAI retrievals from three different types of lidar sensors. The study areas include the La Selva Biological Station in Costa Rica and Sierra Nevada Forest in California. We first obtain independent LAI estimates from different lidar systems including airborne lidar (LVIS), spaceborne lidar (GLAS) and ground lidar (Echidna). LAI retrievals are then evaluated between sensors as a function of scale, land cover type and sensor characteristics. We also assess the accuracy of these LAI products against ground measurements. By providing a link between ground observations, ground lidar, aircraft and space-based lidar we hope to demonstrate a path for deriving more accurate estimates of LAI on a global basis, and to provide a more robust means of validating passive optical estimates of this important variable.

  7. A multi-sensor lidar, multi-spectral and multi-angular approach for mapping canopy height in boreal forest regions

    Science.gov (United States)

    Selkowitz, David J.; Green, Gordon; Peterson, Birgit E.; Wylie, Bruce

    2012-01-01

    Spatially explicit representations of vegetation canopy height over large regions are necessary for a wide variety of inventory, monitoring, and modeling activities. Although airborne lidar data has been successfully used to develop vegetation canopy height maps in many regions, for vast, sparsely populated regions such as the boreal forest biome, airborne lidar is not widely available. An alternative approach to canopy height mapping in areas where airborne lidar data is limited is to use spaceborne lidar measurements in combination with multi-angular and multi-spectral remote sensing data to produce comprehensive canopy height maps for the entire region. This study uses spaceborne lidar data from the Geosciences Laser Altimeter System (GLAS) as training data for regression tree models that incorporate multi-angular and multi-spectral data from the Multi-Angle Imaging Spectroradiometer (MISR) and the Moderate Resolution Imaging SpectroRadiometer (MODIS) to map vegetation canopy height across a 1,300,000 km2 swath of boreal forest in Interior Alaska. Results are compared to in situ height measurements as well as airborne lidar data. Although many of the GLAS-derived canopy height estimates are inaccurate, applying a series of filters incorporating both data associated with the GLAS shots as well as ancillary data such as land cover can identify the majority of height estimates with significant errors, resulting in a filtered dataset with much higher accuracy. Results from the regression tree models indicate that late winter MISR imagery acquired under snow-covered conditions is effective for mapping canopy heights ranging from 5 to 15 m, which includes the vast majority of forests in the region. It appears that neither MISR nor MODIS imagery acquired during the growing season is effective for canopy height mapping, although including summer multi-spectral MODIS data along with winter MISR imagery does appear to provide a slight increase in the accuracy of resulting

  8. Methods to derive lunar DEM from Chang'E-1 laser altimeter data%利用嫦娥一号激光高度计数据制作月球DEM的方法研究

    Institute of Scientific and Technical Information of China (English)

    邹小端; 刘建军; 任鑫; 王文睿; 牟伶俐; 李春来

    2011-01-01

    High-resolution digital elevation models (DEMs) based on data from Laser Altimeter (LAM) of Chinese Chang'E-1 mission provide geospatial characterizations of lunar topography. The primary LAM elevation data are two-dimensional topographic profiles. Developing three-dimensional DEMs from these profile data requires the elimination of gross errors and the interpolation of a continuous surface. To detect and remove the error ( pseudo elevation) data from LAM observations the paper suggested an improved linear filter based on empirical formula which adapts the lunar surface feature. And the key parameters for this filter were discussed. In the second part, it tested eight different techniques of spatial interpolation with the filtered data. After comparing and analyzing these interpolation methods by their accuracies, shaded-relief visualizations and topographic profiles, it found the Kriging method worked better than other seven methods in deriving DEM grid. At last, an effective procedure for processing CE-1 elevation data was outlined, and the corresponding parameters were suggested.%本文结合嫦娥一号卫星(CE-1)激光高度计产品数据,研究卫星激光测距数据处理和数字高程模型(DEM)制作的方法.通过滤波实验分析,构造了符合月球地形特征的经验滤波器,并确定了适合LAM数据的滤波窗口大小和地形滤波参数.结合实验结果改进了滤波流程,并对实验区滤波.利用滤波后的数据对八种基本的插值方法进行实验,通过计算插值精度、比较地形晕渲图以及地形剖面细节,评价和比较各方法的插值结果,由此得到结论,克里金插值方法较其他七种方法更适用于月球地形规则格网的生成.最后结合月海和高地两个典型区数据,验证了该套DEM提取方案对不同地形特征区域的适用性.从而,为利用CE-1激光高度计数据开展月球科学研究的科研人员.提供一套行之有效的地形数据处理参考方案.

  9. CBSIT 2009: Airborne Validation of Envisat Radar Altimetry and In Situ Ice Camp Measurements Over Arctic Sea Ice

    Science.gov (United States)

    Connor, Laurence; Farrell, Sinead; McAdoo, David; Krabill, William; Laxon, Seymour; Richter-Menge, Jacqueline; Markus, Thorsten

    2010-01-01

    The past few years have seen the emergence of satellite altimetry as valuable tool for taking quantitative sea ice monitoring beyond the traditional surface extent measurements and into estimates of sea ice thickness and volume, parameters that arc fundamental to improved understanding of polar dynamics and climate modeling. Several studies have now demonstrated the use of both microwave (ERS, Envisat/RA-2) and laser (ICESat/GLAS) satellite altimeters for determining sea ice thickness. The complexity of polar environments, however, continues to make sea ice thickness determination a complicated remote sensing task and validation studies remain essential for successful monitoring of sea ice hy satellites. One such validation effort, the Arctic Aircraft Altimeter (AAA) campaign of2006. included underflights of Envisat and ICESat north of the Canadian Archipelago using NASA's P-3 aircraft. This campaign compared Envisat and ICESat sea ice elevation measurements with high-resolution airborne elevation measurements, revealing the impact of refrozen leads on radar altimetry and ice drift on laser altimetry. Continuing this research and validation effort, the Canada Basin Sea Ice Thickness (CBSIT) experiment was completed in April 2009. CBSIT was conducted by NOAA. and NASA as part of NASA's Operation Ice Bridge, a gap-filling mission intended to supplement sea and land ice monitoring until the launch of NASA's ICESat-2 mission. CBIST was flown on the NASA P-3, which was equipped with a scanning laser altimeter, a Ku-band snow radar, and un updated nadir looking photo-imaging system. The CB5IT campaign consisted of two flights: an under flight of Envisat along a 1000 km track similar to that flown in 2006, and a flight through the Nares Strait up to the Lincoln Sea that included an overflight of the Danish GreenArc Ice Camp off the coast of northern Greenland. We present an examination of data collected during this campaign, comparing airborne laser altimeter measurements

  10. 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.

  11. 基于多卫星融合数据的海平面特征分析%Global sea level change characteristics based on multi-altimeter data

    Institute of Scientific and Technical Information of China (English)

    陈美香; 王蕾; 左军成; 张国胜

    2012-01-01

    利用1993-2008年法国空间局的AVISO多卫星融合高度计资料,采用随机动态、EOF等方法分析全球海平面变化的长期趋势、变化幅度以及季节变化的空间分布特征.结果表明:(a) 1993-2008年间太平洋海平面呈西升东降的形态,印度洋绝大部分海区海平面呈上升趋势,大西洋除湾流流域外的其他海区海平面的长期趋势以上升为主;(b)全球海平面变化存在显著的年变化和半年变化等季节信号,无论是半球平均还是洋盆平均,北半球海平面季节变化的振幅明显大于南半球,中纬度海区季节变化的振幅最大;(c)北印度洋海平面季节变化的振幅高于同纬度带的北太平洋和北大西洋;(d)太平洋、印度洋、大西洋三大洋受西边界流、赤道流系等强流影响的海域海平面变化幅度大于周围海域;(e)赤道海域各大洋东、西边界和大洋内区海平面变化不同步,可能受赤道海洋波动的影响较大;(f)厄尔尼诺年,西太平洋暖池和赤道太平洋中部海平面明显降低,赤道东太平洋海域海平面明显升高,赤道印度洋海域东、西边界的海平面变化与其相反.%Based on the AVISO multi-altimeter data obtained by the Centre National d' Etudes Spatiales of France during the period from 1993 to 2008, the spatial distributions of long-term change and seasonal change of the global sea level were studied using the stochastic dynamic and EOF methods. The results show the following: (a) From 1993 to 2008, the Pacific sea level rose in the west and dropped in the east; the sea level of the Indian Ocean basically rose; and the Atlantic Ocean had a sea level rise in most areas except the Gulf Stream, (b) The global sea level change was characterized by significant seasonal (annual and semi-annual) variation, which was more significant in the Northern Hemisphere than in the Southern Hemisphere. The most significant seasonal variation occurred in the mid

  12. Spatially explicit forest characteristics of Europe through integrating Forest Inventory and Remotely sensed data

    Science.gov (United States)

    Moreno, Adam; Neumann, Mathias; Hasenauer, Hubert

    2015-04-01

    Carbon stock estimates are critical for any carbon trading scheme or climate change mitigation strategy. Understanding the carbon allocation and the structure of its ecosystem further help scientists and policy makers develop realistic plans for utilizing these systems. Forests play an important role in global carbon storage. Therefore it is imperative to include forests in any climate change mitigation and/or carbon trading scheme. Currently there is no estimate of forest carbon stocks and allocation nor forest structure maps throughout Europe. We compiled National Forest Inventory (NFI) data from 12 European countries. We integrated the NFI data with Net Primary Production data (NPP) from Moderate Resolution Imaging Spectroradiometer (MODIS), tree height data from Light Detection and Ranging (LIDAR) data from the Geosciences Laser Altimeter System (GLAS) instrument, and various other spatially explicit data sets. Through this process of integration of terrestrial and space based data we produced wall-to-wall forest characteristics maps of Europe. These maps include forest age, basal area, average diameter at breast height, total carbon, carbon allocation (stem, branches, leaves, roots), and other characteristics derived from forest inventory data. These maps cover Europe - including countries without terrestrial data - and give one coherent harmonized data set of current forest structure and carbon storage on a 16x16km resolution. The methodology presented here has the potential to be used world-wide in regions with data limitations or with limited access to data.

  13. systems

    Directory of Open Access Journals (Sweden)

    Alexander Leonessa

    2000-01-01

    Full Text Available A nonlinear robust control-system design framework predicated on a hierarchical switching controller architecture parameterized over a set of moving nominal system equilibria is developed. Specifically, using equilibria-dependent Lyapunov functions, a hierarchical nonlinear robust control strategy is developed that robustly stabilizes a given nonlinear system over a prescribed range of system uncertainty by robustly stabilizing a collection of nonlinear controlled uncertain subsystems. The robust switching nonlinear controller architecture is designed based on a generalized (lower semicontinuous Lyapunov function obtained by minimizing a potential function over a given switching set induced by the parameterized nominal system equilibria. The proposed framework robustly stabilizes a compact positively invariant set of a given nonlinear uncertain dynamical system with structured parametric uncertainty. Finally, the efficacy of the proposed approach is demonstrated on a jet engine propulsion control problem with uncertain pressure-flow map data.

  14. Height Change Detection in Antarctica Using ICESat Data Based on Kriging/Kalman Filtering Technique

    Science.gov (United States)

    Huang, H.

    2009-04-01

    Studies of the response of ice sheets to climate change require data sets with high accuracy and uniform ice sheet coverage. Measurements from the Geoscience Laser Altimeter System(GLAS) aboard NASA's ICESat satellite are used to estimate changes in the ice sheet surface heights and the secular change in Antarctic ice mass. Usually, the most common technique used in analyzing satellite altimetry data to study height change in the ice sheets is the dh/dt technique based on the cross-over geometry. However, this approach only uses less ten percent of the available data. So in this paper, Kriging is introduced as an alternative method, which will enable us to use all of the data and the data statistics to estimate height changes and other surface characteristics. Results of height change rate dh/dt in Antarctica for the years 2003-2005 produced using Kriging and cross-over analysis are compared. In the Amery Ice Shelf and in the West Antarctic coastal area and near latitude-81∘N , the difference in dh/dt between the two methods is statistically significant. Specifically, Kriging gives higher positive dh/dt at the Amery Ice Shelf, and does not show the pervasive negative dh/dt in the Pine Island/Thwaites Glaciers area. In addition, Kriging results also show a systematic positive difference of approximately 0.03

  15. Characterizing uncertainties of the national-scale forest gross aboveground biomass (AGB) loss estimate: a case study of the Democratic Republic of the Congo

    Science.gov (United States)

    Tyukavina, A.; Stehman, S.; Potapov, P.; Turubanova, S.; Baccini, A.; Goetz, S. J.; Laporte, N. T.; Houghton, R. A.; Hansen, M.

    2013-12-01

    Modern remote sensing techniques enable the mapping and monitoring of aboveground biomass (AGB) carbon stocks without relying on extensive in situ measurements. The Democratic Republic of the Congo (DRC) is among the countries where a national forest inventory (NFI) has yet to be established due to a lack of infrastructure and political instability. We demonstrate a method for producing national-scale gross AGB loss estimates and quantifying uncertainty of the estimates using remotely sensed-derived forest cover loss and biomass carbon density data. Forest cover type and loss were characterized using published Landsat-based data sets and related to LIDAR-derived biomass data from the Geoscience Laser Altimeter System (GLAS). We produced two gross AGB loss estimates for the DRC for the last decade (2000-2010): a conservative estimate accounting for classification errors in the 60-m resolution FACET forest cover change product, and a maximal estimate that also took into consideration omitted change at the 30m spatial resolution. Omitted disturbances were largely related to smallholder agriculture, the detection of which is scale-dependent. The use of LIDAR data as a substitute for NFI data to estimate AGB loss based on Landsat-derived activity data was demonstrated. Comparisons of our forest cover loss and AGB estimates with published studies raise the issue of scale in forest cover change mapping and its impact on carbon stock change estimation using remotely sensed data.

  16. Automatic Weather Station (AWS) Lidar

    Science.gov (United States)

    Rall, Jonathan A.R.; Abshire, James B.; Spinhirne, James D.; Smith, David E. (Technical Monitor)

    2000-01-01

    An autonomous, low-power atmospheric lidar instrument is being developed at NASA Goddard Space Flight Center. This compact, portable lidar will operate continuously in a temperature controlled enclosure, charge its own batteries through a combination of a small rugged wind generator and solar panels, and transmit its data from remote locations to ground stations via satellite. A network of these instruments will be established by co-locating them at remote Automatic Weather Station (AWS) sites in Antarctica under the auspices of the National Science Foundation (NSF). The NSF Office of Polar Programs provides support to place the weather stations in remote areas of Antarctica in support of meteorological research and operations. The AWS meteorological data will directly benefit the analysis of the lidar data while a network of ground based atmospheric lidar will provide knowledge regarding the temporal evolution and spatial extent of Type la polar stratospheric clouds (PSC). These clouds play a crucial role in the annual austral springtime destruction of stratospheric ozone over Antarctica, i.e. the ozone hole. In addition, the lidar will monitor and record the general atmospheric conditions (transmission and backscatter) of the overlying atmosphere which will benefit the Geoscience Laser Altimeter System (GLAS). Prototype lidar instruments have been deployed to the Amundsen-Scott South Pole Station (1995-96, 2000) and to an Automated Geophysical Observatory site (AGO 1) in January 1999. We report on data acquired with these instruments, instrument performance, and anticipated performance of the AWS Lidar.

  17. AltiKa: a Ka-band Altimetry Payload and System for Operational Altimetry during the GMES Period

    Directory of Open Access Journals (Sweden)

    Jacques Verron

    2006-03-01

    Full Text Available This paper describes the Ka-band altimetry payload and system that has beenstudied for several years by CNES, ALCATEL SPACE and some science laboratories.Altimetry is one of the major elements of the ocean observing system to be madesustainable through the GEOSS (Global Earth Observation System of Systems and GMES(Global Monitoring of the Environment and Security programs. A short review of somemission objectives to be fulfilled in terms of mesoscale oceanography in the frame of theGEOSS and GMES programs is performed. To answer the corresponding requirements, theapproach consisting in a constellation of nadir altimeter is discussed. A coupled Ka-bandaltimeter-radiometer payload is then described; technical items are detailed to explain howthis payload shall meet the science and operational requirements, and expectedperformances are displayed. The current status of the payload development and flightperspectives are given.

  18. SYSTEM

    Directory of Open Access Journals (Sweden)

    K. Swarnalatha

    2013-01-01

    Full Text Available Risk analysis of urban aquatic systems due to heavy metals turns significant due to their peculiar properties viz. persis tence, non-degradab ility, toxicity, and accumulation. Akkulam Veli (AV, an urba n tropical lake in south India is subjected to various environmental stresses due to multiple waste discharge, sand mining, developmental activities, tour ism related activitie s etc. Hence, a comprehensive approach is adopted for risk assessment using modified degree of contamination factor, toxicity units based on numerical sediment quality guidelines (SQGs, and potentialecological risk indices. The study revealed the presence of toxic metals such as Cr, C d, Pb and As and the lake is rated under ‘low ecological risk’ category.

  19. Sea Ice Mapping using Unmanned Aerial Systems

    Science.gov (United States)

    Solbø, S.; Storvold, R.

    2011-12-01

    Mapping of sea ice extent and sea ice features is an important task in climate research. Since the arctic coastal and oceanic areas have a high probability of cloud coverage, aerial platforms are superior to satellite measurements for high-resolution optical measurements. However, routine observations of sea ice conditions present a variety of problems using conventional piloted aircrafts. Specially, the availability of suitable aircrafts for lease does not cover the demand in major parts of the arctic. With the recent advances in unmanned aerial systems (UAS), there is a high possibility of establishing routine, cost effective aerial observations of sea ice conditions in the near future. Unmanned aerial systems can carry a wide variety of sensors useful for characterizing sea-ice features. For instance, the CryoWing UAS, a system initially designed for measurements of the cryosphere, can be equipped with digital cameras, surface thermometers and laser altimeters for measuring freeboard of ice flows. In this work we will present results from recent CryoWing sea ice flights on Svalbard, Norway. The emphasis will be on data processing for stitching together images acquired with the non-stabilized camera payload, to form high-resolution mosaics covering large spatial areas. These data are being employed to map ice conditions; including ice and lead features and melt ponds. These high-resolution mosaics are also well suited for sea-ice mechanics, classification studies and for validation of satellite sea-ice products.

  20. Analysis of different atmospheric physical parameterizations in COAWST modeling system for the Tropical Storm Nock-ten application

    DEFF Research Database (Denmark)

    Ren, Danqin; Du, Jianting; Hua, Feng;

    2016-01-01

    A coupled ocean–atmosphere–wave–sediment transport modeling system was applied to study the atmosphere and ocean dynamics during Tropical Storm Nock-ten. Different atmospheric physical parameterizations in WRF model were investigated through ten groups of numerical experiments. Results...... in terms of fitting coefficient, root-mean-square error, correlation coefficient and model performance, the recommended atmospheric physical parameterization in this coupled system, have been obtained......., they are not recommended for this study. Ocean parameters such as significant wave height, SST and current speed are more sensitive to Single-Moment 6-class microphysics scheme than to Eta microphysics scheme at the storm center. By analyzing modeled data with JASON-2 altimeter data, ERA-Interim data and HYCOM data...

  1. ATLAS LTCS Vertically Challenged System Lessons Learned

    Science.gov (United States)

    Patel, Deepak; Garrison, Matt; Ku, Jentung

    2014-01-01

    Re-planning of LTCS TVAC testing and supporting RTA (Receiver Telescope Assembly) Test Plan and Procedure document preparation. The Laser Thermal Control System (LTCS) is designed to maintain the lasers onboard Advanced Topographic Laser Altimeter System (ATLAS) at their operational temperatures. In order to verify the functionality of the LTCS, a thermal balance test of the thermal hardware was performed. During the first cold start of the LTCS, the Loop Heat Pipe (LHP) was unable to control the laser mass simulators temperature. The control heaters were fully on and the loop temperature remained well below the desired setpoint. Thermal analysis of the loop did not show these results. This unpredicted behavior of the LTCS was brought up to a panel of LHP experts. Based on the testing and a review of all the data, there were multiple diagnostic performed in order to narrow down the cause. The prevailing theory is that gravity is causing oscillating flow within the loop, which artificially increased the control power needs. This resulted in a replan of the LTCS test flow and the addition of a GSE heater to allow vertical operation.

  2. A cost effective and operational methodology for wall to wall Above Ground Biomass (AGB) and carbon stocks estimation and mapping: Nepal REDD+

    Science.gov (United States)

    Gilani, H., Sr.; Ganguly, S.; Zhang, G.; Koju, U. A.; Murthy, M. S. R.; Nemani, R. R.; Manandhar, U.; Thapa, G. J.

    2015-12-01

    Nepal is a landlocked country with 39% forest cover of the total land area (147,181 km2). Under the Forest Carbon Partnership Facility (FCPF) and implemented by the World Bank (WB), Nepal chosen as one of four countries best suitable for results-based payment system for Reducing Emissions from Deforestation and Forest Degradation (REDD and REDD+) scheme. At the national level Landsat based, from 1990 to 2000 the forest area has declined by 2%, i.e. by 1467 km2, whereas from 2000 to 2010 it has declined only by 0.12% i.e. 176 km2. A cost effective monitoring and evaluation system for REDD+ requires a balanced approach of remote sensing and ground measurements. This paper provides, for Nepal a cost effective and operational 30 m Above Ground Biomass (AGB) estimation and mapping methodology using freely available satellite data integrated with field inventory. Leaf Area Index (LAI) generated based on propose methodology by Ganguly et al. (2012) using Landsat-8 the OLI cloud free images. To generate tree canopy height map, a density scatter graph between the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud, and Land Elevation Satellite (ICESat) estimated maximum height and Landsat LAI nearest to the center coordinates of the GLAS shots show a moderate but significant exponential correlation (31.211*LAI0.4593, R2= 0.33, RMSE=13.25 m). From the field well distributed circular (750m2 and 500m2), 1124 field plots (0.001% representation of forest cover) measured which were used for estimation AGB (ton/ha) using Sharma et al. (1990) proposed equations for all tree species of Nepal. A satisfactory linear relationship (AGB = 8.7018*Hmax-101.24, R2=0.67, RMSE=7.2 ton/ha) achieved between maximum canopy height (Hmax) and AGB (ton/ha). This cost effective and operational methodology is replicable, over 5-10 years with minimum ground samples through integration of satellite images. Developed AGB used to produce optimum fuel wood scenarios using population and road

  3. Abiotic Controls on Macroscale Variations of Humid Tropical Forest Height

    Directory of Open Access Journals (Sweden)

    Yan Yang

    2016-06-01

    Full Text Available Spatial variation of tropical forest tree height is a key indicator of ecological processes associated with forest growth and carbon dynamics. Here we examine the macroscale variations of tree height of humid tropical forests across three continents and quantify the climate and edaphic controls on these variations. Forest tree heights are systematically sampled across global humid tropical forests with more than 2.5 million measurements from Geoscience Laser Altimeter System (GLAS satellite observations (2004–2008. We used top canopy height (TCH of GLAS footprints to grid the statistical mean and variance and the 90 percentile height of samples at 0.5 degrees to capture the regional variability of average and large trees globally. We used the spatial regression method (spatial eigenvector mapping-SEVM to evaluate the contributions of climate, soil and topography in explaining and predicting the regional variations of forest height. Statistical models suggest that climate, soil, topography, and spatial contextual information together can explain more than 60% of the observed forest height variation, while climate and soil jointly explain 30% of the height variations. Soil basics, including physical compositions such as clay and sand contents, chemical properties such as PH values and cation-exchange capacity, as well as biological variables such as the depth of organic matter, all present independent but statistically significant relationships to forest height across three continents. We found significant relations between the precipitation and tree height with shorter trees on the average in areas of higher annual water stress, and large trees occurring in areas with low stress and higher annual precipitation but with significant differences across the continents. Our results confirm other landscape and regional studies by showing that soil fertility, topography and climate may jointly control a significant variation of forest height and

  4. Umur glas eel (Anguilla spp. yang masuk muara Sungai Progo Yogyakarta

    Directory of Open Access Journals (Sweden)

    Agung Budiharjo

    2017-03-01

    Full Text Available The leptocephalus drift with sea currents and moving from spawning area into coastal area near mouth of Progo River. In thecoastal area, leptocephalus metamorfosed into glass eel, after that glass eel migrated to river. The aims of this research were to estimate glass eels age and predict hatching dates. Glass eels sampled on new moon during Februari 2007-Mei 2009 at mouth of Progo River.Glass eel ages estimated using their otolith micro structure. Hatching dates predicted with back calculation of glass eels age. We collected 1.082 glass eels. The ages of glass eel at recruit ranged from 58 to 190 days, and divided into 5 age groups. Glass eels are migrated to river hatched on a "new moon" from July to January. Glass eels are migrated to river during October-January hatched during July-October. Glass eels are migrated to river during February-Juny hatched during November-January.

  5. Premixing hydrogen burners for surface refinement of glass; Vormischende Wasserstoffbrenner zur Oberflaechenbearbeitung von Glas

    Energy Technology Data Exchange (ETDEWEB)

    Goerisch, Matthias [Linde AG, Linde Gas Deutschland, Nuernberg (Germany)

    2013-02-15

    As a result, inter alia, of unceasing globalisation, European glass producers in practically all sectors - flat glass, container glass, crystal glass and special glasses - are faced with ever tougher competition from Asia. In the 2012 to 2015 period and beyond, the principal focuses in the manufacture of glass products will again be on reducing overall production costs and increasing process efficiency wherever possible, on greater productivity and on enhanced product (surface) quality. To meet these challenges in the field of surface refinement and flame polishing of glass products as efficiently as possible, Linde AG/Linde Gases Division has developed premixing Hydropox {sup registered} burner technology for hydrogen/oxygen fuels. (orig.)

  6. GLAS/ICESat L2 Global Land Surface Altimetry Data V033

    Data.gov (United States)

    National Aeronautics and Space Administration — GLA14 contains the land elevation and elevation distribution corrected for geodetic and atmospheric affects calculated from algorithms fine-tuned for over land...

  7. GLAS/ICESat L2 Global Antarctic and Greenland Ice Sheet Altimetry Data V033

    Data.gov (United States)

    National Aeronautics and Space Administration — GLA12 contains the ice sheet elevation and elevation distribution corrected for geodetic and atmospheric affects calculated from algorithms fine-tuned for ice sheet...

  8. GLAS/ICESat L2 Sea Ice Altimetry Data (HDF5) V033

    Data.gov (United States)

    National Aeronautics and Space Administration — GLAH13 contains sea ice and open ocean elevations corrected for geodetic and atmospheric affects, calculated from algorithms fine-tuned for sea ice returns. Granules...

  9. Voorruiten van gelaagd en gehard glas. Consult in opdracht van de Rijksdienst voor het Wegverkeer.

    NARCIS (Netherlands)

    Kampen, L.T.B. van

    1981-01-01

    Windscreens of cars are mostly made of laminated or tempered glass. In this report the differences between the safety of laminated and tempered glass in case of collision are studied. It is shown that there is hardly any difference in the effect of the result of an accident for the vehicle occupant.

  10. Onderzoek naar de samenstelling van gescheiden ingezameld glas uit de glasbak

    NARCIS (Netherlands)

    Otte PF

    1993-01-01

    This report presents the results of sorting analyses of used glass derived from communal glass containers. Analyses took place in February 1993 in the framework of activities defined in an agreement between the Dutch Government and the packing industry, the so called 'Convenant Verpakkingen&ap

  11. GLAS/ICESat L1B Global Waveform-based Range Corrections Data V033

    Data.gov (United States)

    National Aeronautics and Space Administration — The level 1B waveform parameterization data will contain waveform-based range corrections and surface characteristics at the full 40 per second resolution. Data...

  12. GLAS/ICESat L2 Ocean Altimetry Data (HDF5) V033

    Data.gov (United States)

    National Aeronautics and Space Administration — GLAH15 contains the ocean elevation and small-scale roughness corrected for geodetic and atmospheric affects, calculated from algorithms fine-tuned for ocean...

  13. PerioGlasU acts on human stem cells isolated from peripheral blood

    Directory of Open Access Journals (Sweden)

    Vincenzo Sollazzo

    2010-01-01

    Conclusion : PG has a differentiation effect on mesenchymal stem cells derived from peripheral blood. The obtained results can be relevant to better understanding of the molecular mechanism of bone regeneration and as a model for comparing other materials with similar clinical effects.

  14. Estimating Digital Terrain Model in forest areas from TanDEM-X and Stereo-photogrammetric technique by means of Random Volume over Ground model

    Science.gov (United States)

    Lee, S. K.; Fatoyinbo, T. E.; Lagomasino, D.; Osmanoglu, B.; Feliciano, E. A.

    2015-12-01

    The Digital Terrain Model (DTM) in forest areas is invaluable information for various environmental, hydrological and ecological studies, for example, watershed delineation, vegetation canopy height, water dynamic modeling, forest biomass and carbon estimations. There are few solutions to extract bare-earth Digital Elevation Model information. Airborne lidar systems are widely and successfully used for estimating bare-earth DEMs with centimeter-order accuracy and high spatial resolution. However, expensive cost of operation and small image coverage prevent the use of airborne lidar sensors for large- or global-scale. Although IceSAT/GLAS (Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System) lidar data sets have been available for global DTM estimate with relatively lower cost, the large footprint size of 70 m and the interval of 172 m are insufficient for various applications. In this study we propose to extract higher resolution bare-earth DEM over vegetated areas from the combination of interferometric complex coherence from single-pass TanDEM-X (TDX) data at HH polarization and Digital Surface Model (DSM) derived from high-resolution WorldView (WV) images by means of random volume over ground (RVoG) model. The RVoG model is a widely and successfully used model for polarimetric SAR interferometry (Pol-InSAR) forest canopy height inversion. The bare-earth DEM is obtained by complex volume decorrelation in the RVoG model with the DSM estimated by stereo-photogrammetric technique. Forest canopy height can be estimated by subtracting the estimated bare-earth model from the DSM. Finally, the DTM from airborne lidar system was used to validate the bare-earth DEM and forest canopy height estimates.

  15. Impact of Altimeter Data Processing on Sea Level Studies

    Directory of Open Access Journals (Sweden)

    Clara Lázaro

    2006-03-01

    Full Text Available This study addresses the impact of satellite altimetry data processing on sea levelstudies at regional scale, with emphasis on the influence of various geophysical correctionsand satellite orbit on the structure of the derived interannual signal and sea level trend. Thework focuses on the analysis of TOPEX data for a period of over twelve years, for threeregions in the North Atlantic: Tropical (0o≤φ≤25o, Sub-Tropical (25o≤φ≤50o and Sub-Arctic (50o≤φ≤65o. For this analysis corrected sea level anomalies with respect to a meansea surface model have been derived from the GDR-Ms provided by AVISO by applyingvarious state-of-the-art models for the geophysical corrections. Results show that sea leveltrend determined from TOPEX altimetry is dependent on the adopted models for the majorgeophysical corrections. The main effects come from the sea state bias (SSB, and from theapplication or not of the inverse barometer (IB correction. After an appropriate modellingof the TOPEX A/B bias, the two analysed SSB models induce small variations in sea leveltrend, from 0.0 to 0.2 mm/yr, with a small latitude dependence. The difference in sea leveltrend determined by a non IB-corrected series and an IB-corrected one has a strong regionaldependence with large differences in the shape of the interannual signals and in the derivedlinear trends. The use of two different drift models for the TOPEX Microwave Radiometer(TMR has a small but non negligible effect on the North Atlantic sea level trend of about0.1 mm/yr. The interannual signals of sea level time series derived with the NASA and theCNES orbits respectively, show a small departure in the middle of the series, which has noimpact on the derived sea level trend. These results strike the need for a continuousimprovement in the modelling of the various effects that influence the altimetermeasurement.

  16. National-scale estimation of gross forest aboveground carbon loss: a case study of the Democratic Republic of the Congo

    Science.gov (United States)

    Tyukavina, A.; Stehman, S. V.; Potapov, P. V.; Turubanova, S. A.; Baccini, A.; Goetz, S. J.; Laporte, N. T.; Houghton, R. A.; Hansen, M. C.

    2013-12-01

    Recent advances in remote sensing enable the mapping and monitoring of carbon stocks without relying on extensive in situ measurements. The Democratic Republic of the Congo (DRC) is among the countries where national forest inventories (NFI) are either non-existent or out of date. Here we demonstrate a method for estimating national-scale gross forest aboveground carbon (AGC) loss and associated uncertainties using remotely sensed-derived forest cover loss and biomass carbon density data. Lidar data were used as a surrogate for NFI plot measurements to estimate carbon stocks and AGC loss based on forest type and activity data derived using time-series multispectral imagery. Specifically, DRC forest type and loss from the FACET (Forêts d’Afrique Centrale Evaluées par Télédétection) product, created using Landsat data, were related to carbon data derived from the Geoscience Laser Altimeter System (GLAS). Validation data for FACET forest area loss were created at a 30-m spatial resolution and compared to the 60-m spatial resolution FACET map. We produced two gross AGC loss estimates for the DRC for the last decade (2000-2010): a map-scale estimate (53.3 ± 9.8 Tg C yr-1) accounting for whole-pixel classification errors in the 60-m resolution FACET forest cover change product, and a sub-grid estimate (72.1 ± 12.7 Tg C yr-1) that took into account 60-m cells that experienced partial forest loss. Our sub-grid forest cover and AGC loss estimates, which included smaller-scale forest disturbances, exceed published assessments. Results raise the issue of scale in forest cover change mapping and validation, and subsequent impacts on remotely sensed carbon stock change estimation, particularly for smallholder dominated systems such as the DRC.

  17. Sensitivity of L-Band SAR Backscatter to Aboveground Biomass of Global Forests

    Directory of Open Access Journals (Sweden)

    Yifan Yu

    2016-06-01

    Full Text Available Synthetic Aperture Radar (SAR backscatter measurements are sensitive to forest aboveground biomass (AGB, and the observations from space can be used for mapping AGB globally. However, the radar sensitivity saturates at higher AGB values depending on the wavelength and geometry of radar measurements, and is influenced by the structure of the forest and environmental conditions. Here, we examine the sensitivity of SAR at the L-band frequency (~25 cm wavelength to AGB in order to examine the performance of future joint National Aeronautics and Space Administration, Indian Space Research Organisation NASA-ISRO SAR mission in mapping the AGB of global forests. For SAR data, we use the Phased Array L-Band SAR (PALSAR backscatter from the Advanced Land Observing Satellite (ALOS aggregated at a 100-m spatial resolution; and for AGB data, we use more than three million AGB values derived from the Geoscience Laser Altimeter System (GLAS LiDAR height metrics at about 0.16–0.25 ha footprints across eleven different forest types globally. The results from statistical analysis show that, over all eleven forest types, saturation level of L-band radar at HV polarization on average remains ≥100 Mg·ha−1. Fresh water swamp forests have the lowest saturation with AGB at ~80 Mg·ha−1, while needleleaf forests have the highest saturation at ~250 Mg·ha−1. Swamp forests show a strong backscatter from the vegetation-surface specular reflection due to inundation that requires to be treated separately from those on terra firme. Our results demonstrate that L-Band backscatter relations to AGB can be significantly different depending on forest types and environmental effects, requiring multiple algorithms to map AGB from time series of satellite radar observations globally.

  18. 南极查尔斯王子山脉1∶50 000基础地理信息获取方法%Acquisition Method for 1 ∶ 50 000 Fundamental Geographic Information in Prince Charles Mountains

    Institute of Scientific and Technical Information of China (English)

    谭继强; 詹庆明; 李占荣; 韩凉

    2016-01-01

    南极查尔斯王子山脉实地科学考察的顺利开展需要该区域1∶50 000基础地理信息数据作为支撑.国产高分辨率资源三号立体影像为基础地理信息数据的获取提供了必要的遥感数据支持.充分利用资源三号立体数据,在冰、云和陆地高程卫星(the ice,cloud,and land elevation satellite,ICESat)上的地学激光测高系统(Geoscience Laser Altimeter System,GLAS)等多源遥感信息的辅助下,制作了南极查尔斯王子山脉1∶50 000基础地理信息成果,并对其进行了精度分析.分析结果表明,数字高程模型(DEM)的高程精度优于5.31m,数字正射影像图(DOM)成果与南极洲陆地卫星影像镶嵌图比较的较差中误差为16.30 m.因此,在南极地区利用资源三号立体数据集成各种遥感数据制作1∶50 000基础地理信息成果是高效实用的.

  19. Blue Carbon distribution in mangrove forests of the Americas

    Science.gov (United States)

    Simard, M.; Rivera-Monroy, V.; Fatoyinbo, T. E.; Roy Chowdhury, R.

    2013-12-01

    Globally, coastal ecosystems are critical to maintaining human livelihood and biodiversity. These ecosystems including mangroves, salt marshes, and sea grasses provide essential ecosystem services, such as supporting fisheries by providing important spawning grounds, filtering pollutants and contaminants from coastal waters, and protecting coastal development and communities against storms, floods and erosion. Additionally, recent research indicates that these vegetated coastal ecosystems are highly efficient carbon sinks (i.e. 'Blue Carbon') and can potentially play a significant role in ameliorating the effect of increasing global climate change by capturing significant amounts of carbon into sediments and plant biomass. The term blue carbon indicates the carbon stored in coastal vegetated wetlands (i.e., mangroves, intertidal marshes, and seagrass meadows). As a result of rapid global changes in coastal regions, it is crucial that we improve our understanding of the current and future state of the remaining coastal ecosystems and associated ecosystem services and their vulnerability to global climate change. In this study, we present a continental scale study of mangrove distribution and assess patterns of forest structural development associated to latitude and geomorphological setting. We produced a baseline map of mangrove canopy height and biomass for all mangrove forests of the Americas using data from the Shuttle Radar Topography Mission (SRTM) and publicly available land cover maps (Figure 1). The resulting canopy height map was calibrated using ICEsat/Geoscience Laser Altimeter system (GLAS). Biomass was derived from field data and allometry. The maps were validated with field data and results in accuracies that vary spatially around 2 to 3m in height and 20% in biomass. Figure 1: Global distribution of mangrove forests (green) and SRTM elevation data. These data were used to produce large scale maps of mangrove canopy height and biomass.

  20. How essential are Argo observations to constrain a global ocean data assimilation system?

    Science.gov (United States)

    Turpin, V.; Remy, E.; Le Traon, P. Y.

    2016-02-01

    Observing system experiments (OSEs) are carried out over a 1-year period to quantify the impact of Argo observations on the Mercator Ocean 0.25° global ocean analysis and forecasting system. The reference simulation assimilates sea surface temperature (SST), SSALTO/DUACS (Segment Sol multi-missions dALTimetrie, d'orbitographie et de localisation précise/Data unification and Altimeter combination system) altimeter data and Argo and other in situ observations from the Coriolis data center. Two other simulations are carried out where all Argo and half of the Argo data are withheld. Assimilating Argo observations has a significant impact on analyzed and forecast temperature and salinity fields at different depths. Without Argo data assimilation, large errors occur in analyzed fields as estimated from the differences when compared with in situ observations. For example, in the 0-300 m layer RMS (root mean square) differences between analyzed fields and observations reach 0.25 psu and 1.25 °C in the western boundary currents and 0.1 psu and 0.75 °C in the open ocean. The impact of the Argo data in reducing observation-model forecast differences is also significant from the surface down to a depth of 2000 m. Differences between in situ observations and forecast fields are thus reduced by 20 % in the upper layers and by up to 40 % at a depth of 2000 m when Argo data are assimilated. At depth, the most impacted regions in the global ocean are the Mediterranean outflow, the Gulf Stream region and the Labrador Sea. A significant degradation can be observed when only half of the data are assimilated. Therefore, Argo observations matter to constrain the model solution, even for an eddy-permitting model configuration. The impact of the Argo floats' data assimilation on other model variables is briefly assessed: the improvement of the fit to Argo profiles do not lead globally to unphysical corrections on the sea surface temperature and sea surface height. The main conclusion

  1. Simulation development of a forward sensor-enhanced low-altitude guidance system

    Science.gov (United States)

    Zelenka, Richard E.; Swenson, Harry N.; Dearing, Munro G.; Hardy, Gordon H.

    1993-01-01

    The requirement to operate aircraft at low-altitude near the terrain is common in the military community and essential for helicopters. The risk and crew workload in this flight regime is severe, with navigation, guidance, and obstacle avoidance demanding high attention. A guidance system relying on digitized terrain elevation maps has been developed that employs airborne navigation, mission requirements, aircraft performance limits, and radar altimeter returns to generate a valley-seeking, low-altitude trajectory between waypoints for display to the pilot. This system has been flight demonstrated to 150 ft above ground level altitude, and is primarily limited by the ability of the pilot to perform obstacle detection and avoidance. In this study, a wide field of view forward sensor has been modeled and incorporated in the guidance system for the purpose of relieving the pilot of the obstacle avoidance duty. The results of a piloted, motion-based simulation of this enhanced low-altitude guidance system is presented. Simulated flights to 50 ft altitude in the presence of obstacles were demonstrated while maintaining situational awareness and close tracking of the guidance trajectory.

  2. The JAC airborne EM system: AEM-05

    Science.gov (United States)

    Leväniemi, H.; Beamish, D.; Hautaniemi, H.; Kurimo, M.; Suppala, I.; Vironmäki, J.; Cuss, R. J.; Lahti, M.; Tartaras, E.

    2009-03-01

    This paper describes the airborne electromagnetic (AEM) system operated by the Joint Airborne geoscience Capability (JAC), a partnership between the Finnish and British Geological Surveys. The system is a component of a 3-in-1, fixed-wing facility acquiring magnetic gradiometer and full spectrum radiometric data alongside the wing-tip, frequency-domain AEM measurements. The AEM system has recently (2005) been upgraded from 2 to 4 frequencies and now provides a bandwidth from 900 Hz to 25 kHz. The fixed-wing configuration of 4 dual vertical coplanar coils, offers a high signal/noise by virtue of the wingspan separation of the sensors. This unique configuration allows 3-in-1 surveys to be successfully performed at a variety of survey elevations when regulatory conditions are imposed. Its deployment on a twin-engine aircraft also permits low altitude surveying in countries, such as the UK, where this is a requirement. The development of the new AEM-05 system has been incremental and its history can be traced back over five decades. The AEM data acquired in the Finnish National Mapping project, and across northern Europe, have been used extensively in mineral exploration. More recent projects have investigated the application of the data to environmental, hydrogeological and land quality issues. These studies have been enhanced by reducing the flight line separation from 200 m (the national high-resolution scale) to 50 m. Our surveys also increasingly involve the application of AEM across populated areas often with extensive infrastructure. Additional secondary instrumentation has been introduced to provide an increased understanding of the data and the AEM responses observed. The secondary systems include an accurate, high sampling rate laser altimeter, a downward-looking digital camera to record the flight path, a 50/60 Hz power line monitor and a GPS gyroscope. The paper is intended as an overview and provides descriptions of the new AEM system, the secondary

  3. SpaceNav - A high accuracy navigation system for space applications

    Science.gov (United States)

    Evers, H.-H.

    The technology of the SpaceNav-system is based on research performed by the Institute of Flight Guidance and Control at the Technical University of Braunschweig, Germany. In 1989 this institute gave the worlds first public demonstration of a fully automatic landing of an aircraft, using inertial and satellite informations exclusively. The SpaceNav device components are: Acceleration-/Gyro Sensor Package; Global Positioning System (GPS) Receiver/optional more than one; Time Reference Unit; CPU; Telemetry (optional); and Differential GPS (DGPS) Receiver (optional). The coupling of GPS receivers with inertial sensors provides an extremely accurate navigation data set in real time applications even in phases with high dynamic conditions. The update rate of this navigation information is up to 100 Hz with the same accuracy in 3D-position, velocity, acceleration, attitude and time. SpaceNav is an integrated navigation system, which operates according to the principle of combining the longterm stability and accuracy of GPS, and the high level of dynamic precision of conventional inertial navigation system (INS) strapdown systems. The system's design allows other aiding sensors e.g. GLONASS satellite navigation system, distance measuring equipment (DME), altimeter (radar and/or barometric), flux valve etc. to be connected, in order to increase the redundancy of the system. The advantage of such an upgraded system is the availability of more sensor information than necessary for a navigation solution. The resulting redundancy in range measurement allows real-time detection and identification of sensor signals that are incompatible with the other information. As a result you get Receiver Autonomous Integrity Monitoring (RAIM) as described in 'A Multi-Sensor Approach to Assuring GPS Integrity', presented by Alison Brown in the March/April 1990 issue of 'GPS World'. In this paper the author presents information about the principles of the Satellite Navigation System GPS, and

  4. Lidar-Based Estimates of Above-Ground Biomass in the Continental US and Mexico Using Ground, Airborne, and Satellite Observations

    Science.gov (United States)

    Nelson, Ross; Margolis, Hank; Montesano, Paul; Sun, Guoqing; Cook, Bruce; Corp, Larry; Andersen, Hans-Erik; DeJong, Ben; Pellat, Fernando Paz; Fickel, Thaddeus; Kauffman, Jobriath; Prisley, Stephen

    2016-01-01

    Existing national forest inventory plots, an airborne lidar scanning (ALS) system, and a space profiling lidar system (ICESat-GLAS) are used to generate circa 2005 estimates of total aboveground dry biomass (AGB) in forest strata, by state, in the continental United States (CONUS) and Mexico. The airborne lidar is used to link ground observations of AGB to space lidar measurements. Two sets of models are generated, the first relating ground estimates of AGB to airborne laser scanning (ALS) measurements and the second set relating ALS estimates of AGB (generated using the first model set) to GLAS measurements. GLAS then, is used as a sampling tool within a hybrid estimation framework to generate stratum-, state-, and national-level AGB estimates. A two-phase variance estimator is employed to quantify GLAS sampling variability and, additively, ALS-GLAS model variability in this current, three-phase (ground-ALS-space lidar) study. The model variance component characterizes the variability of the regression coefficients used to predict ALS-based estimates of biomass as a function of GLAS measurements. Three different types of predictive models are considered in CONUS to determine which produced biomass totals closest to ground-based national forest inventory estimates - (1) linear (LIN), (2) linear-no-intercept (LNI), and (3) log-linear. For CONUS at the national level, the GLAS LNI model estimate (23.95 +/- 0.45 Gt AGB), agreed most closely with the US national forest inventory ground estimate, 24.17 +/- 0.06 Gt, i.e., within 1%. The national biomass total based on linear ground-ALS and ALS-GLAS models (25.87 +/- 0.49 Gt) overestimated the national ground-based estimate by 7.5%. The comparable log-linear model result (63.29 +/-1.36 Gt) overestimated ground results by 261%. All three national biomass GLAS estimates, LIN, LNI, and log-linear, are based on 241,718 pulses collected on 230 orbits. The US national forest inventory (ground) estimates are based on 119

  5. The 1/12 degree Global HYCOM Nowcast/Forecast System

    Science.gov (United States)

    Smedstad, O. M.; Cummings, J. A.; Metzger, E. J.; Hurlburt, H. E.; Wallcraft, A. J.; Franklin, D. S.; Shriver, J. F.; Thoppil, P. G.

    2010-05-01

    The 1/12 degree global HYbrid Coordinate Ocean Model (HYCOM) has been running daily since 22 December 2006. With ~7 km mid-latitude resolution (3-4 km near the poles), the system depicts the location of mesoscale features such as oceanic eddies and fronts and provides the three dimensional ocean temperature, salinity and current structure. An efficient assimilation scheme is necessary in order to run within the time constraints of an operational center. The Navy Coupled Ocean Data Assimilation (NCODA) system is used to assimilate available observations. An important component of the NCODA system is the quality control of the observations. NCODA uses a multivariate optimal interpolation scheme (MVOI) that assimilates surface observations from satellite altimeter tracks and available SST data. A 3 dimensional variational analysis scheme is in the process of being implemented as a replacement for MVOI. NCODA also assimilates in situ observations, including profile data from BT's and Argo floats. The daily run consists of a 5-day hindcast with an NCODA analysis each day and then a 5-day forecast. Over the last couple of years a series of validation tasks have been performed to evaluate the HYCOM/NCODA system. Independent observations are used whenever possible in the evaluation of assimilation system performance. A subset of these evaluations will be presented. The prediction system provides boundary conditions for higher resolution nested models. An accurate representation of the oceanographic fields at the open boundaries of a model is important for a successful ocean prediction system. Results from the global system can be viewed on the HYCOM web page http://www.hycom.org. The hindcast and the real time model output can also be accessed through this web page.

  6. Microfluidics: Functionality Integration for Proteomic Applications

    DEFF Research Database (Denmark)

    Petersen, Daria

    2006-01-01

    Interessen for miniaturiserede kemiske og biologiske analyser er voksende. I denne rapport er der set på design, fabrikation, og karakterisering af miniaturiserede analytiske systemer. Fokus er lagt på mikrochips fabrikeret i glas til kemiske analyser. Rapporten består af tre dele: 1) design, fab...

  7. GLAS/ICESat L2 Global Antarctic and Greenland Ice Sheet Altimetry Data (HDF5) V033

    Data.gov (United States)

    National Aeronautics and Space Administration — GLAH12 contains the ice sheet elevation and elevation distribution corrected for geodetic and atmospheric affects calculated from algorithms fine-tuned for ice sheet...

  8. Multi-Scale Mapping of Forest Growing Stock Volume Using Envisat ASAR, ALOS PALSAR Landsat, and ICESat GLAS

    Science.gov (United States)

    Cartus, Oliver; Santoro, Maurizio

    2016-08-01

    Multi-scale approaches for mapping aboveground biomass globally are evaluated that exploit the multi- temporal archive of low-resolution (1 km) ENVISAT ASAR C-band observations and ca. 30 m resolution ALOS PALSAR L-band and Landsat mosaics. The BIOMASAR algorithm, which was initially developed for ENVISAT ASAR C-band data and boreal forest [1], is deployed to map growing stock volume, a proxy for aboveground biomass, globally at 1 km resolution. We explore different options for improving ASAR based maps using high resolution data. Two approaches are pursued: 1) the BIOMASAR algorithm adopted for L- band, 2) a simple re-scaling of ASAR derived estimates of growing stock volume from 1 km pixel posting to 30 m using PALSAR and Landsat data [2]. The initial results for different forest ecosystems suggest that both approaches allow for improved estimates, albeit with the expected limitations in high biomass forests.

  9. The influence of tropical wind data on the analysis and forecasts of the GLAS GCM for the Global Weather Experiment

    Science.gov (United States)

    Paegle, J.; Baker, W. E.

    1985-01-01

    Several densities of tropical divergent wind data were included in a fourth-order GCM to examine the effects on the accuracy of the model predictions. The experiments covered assimilation of all available tropical wind data, no tropical wind data between 20 deg N and 20 deg S, only westerly tropical wind data and only easterly tropical wind data. The predictions were all made for the 200 mb upper troposphere. Elimination of tropical data produced excessively strong upper tropospheric westerlies which in turn amplified the globally integrated rotational flow kinetic energy by around 10 percent and doubled the global divergent flow kinetic energy. Retaining only easterly wind data, ameliorated most of the error. Inclusion of all the tropical wind data however, did not lead to overall positive effects, as the data were linked to tropical wave energetics and ageostrophic winds which were already assimilated in the model.

  10. Geoffrey Layton Slack OBE (Mil), CBE, TD, BDS DDS, FDSRCS, FDS Glas, FFDRCSI, Dip Bact (1912-1991).

    Science.gov (United States)

    Gelbier, Stanley

    2014-02-01

    It is with some pride that the author worked in Geoffrey Slack's department from 1963 to 1967 and even retained a working relationship with him after that time. Slack was Professor of Dental Surgery (1959-1976) and later Professor of Community Dental Health (1976-1977) at The London Hospital Medical College, within the University of London. The change in titles came about as a result of recognition of his contribution to developments in public health and community dental care and services, for many of which he was directly responsible. He was Dental Dean from 1965 until 1969. Upon retirement in 1977 he became Emeritus Professor. In addition, he was Dean of the Faculty of Dental Surgery at the Royal College of Surgeons of England from 1974 to 1977.

  11. GLAS/ICESat L1B Global Waveform-based Range Corrections Data (HDF5) V033

    Data.gov (United States)

    National Aeronautics and Space Administration — The level 1B waveform parameterization data will contain waveform-based range corrections and surface characteristics at the full 40 per second resolution. Data...

  12. Comparisons of observed seasonal climate features with a winter and summer numerical simulation produced with the GLAS general circulation model

    Science.gov (United States)

    Halem, M.; Shukla, J.; Mintz, Y.; Wu, M. L.; Godbole, R.; Herman, G.; Sud, Y.

    1979-01-01

    Results are presented from numerical simulations performed with the general circulation model (GCM) for winter and summer. The monthly mean simulated fields for each integration are compared with observed geographical distributions and zonal averages. In general, the simulated sea level pressure and upper level geopotential height field agree well with the observations. Well simulated features are the winter Aleutian and Icelandic lows, the summer southwestern U.S. low, the summer and winter oceanic subtropical highs in both hemispheres, and the summer upper level Tibetan high and Atlantic ridge. The surface and upper air wind fields in the low latitudes are in good agreement with the observations. The geographical distirbutions of the Earth-atmosphere radiation balance and of the precipitation rates over the oceans are well simulated, but not all of the intensities of these features are correct. Other comparisons are shown for precipitation along the ITCZ, rediation balance, zonally averaged temperatures and zonal winds, and poleward transports of momentum and sensible heat.

  13. The Fabrication and Characterisation of Low-k Cordierite-Based Glas s-Ceramics by Tape Casting

    Institute of Scientific and Technical Information of China (English)

    José; M; F; Ferreira

    2002-01-01

    Cordierite is a promising low-k material in mi cr oelectronic and packaging industries. When it is co-fired with the metal for re alising the multilayer circuits, temperature should be low enough to prevent the melting and/or oxidising of the metal. However, this temperature is usually too low to sinter cordierite. Low melting point glass, therefore, is added to the s toichiometric cordierite to lower the sintering temperature through a liquid-si ntering process. In this research work, cordierite-based g...

  14. Parameterization of Surface Roughness Based on ICESat/GLAS Full Waveforms: A Case Study on the Tibetan Plateau

    NARCIS (Netherlands)

    Shi, J.; Menenti, M.; Lindenbergh, R.

    2013-01-01

    Glaciers in the Tibetan mountains are expected to be sensitive to turbulent sensible and latent heat fluxes. One of the most significant factors of the energy exchange between the atmospheric boundary layer and the glacier is the roughness of the glacier surface. However, methods to parameterize thi

  15. Evaluation of real time and future global monitoring and forecasting systems at Mercator Océan

    Directory of Open Access Journals (Sweden)

    J.-M. Lellouche

    2012-03-01

    Full Text Available Since December 2010, the global analysis and forecast of the MyOcean system consists in the Mercator Océan NEMO global 1/4° configuration with a 1/12° "zoom" over the Atlantic and Mediterranean Sea. The zoom open boundaries come from the global 1/4° at 20° S and 80° N.

    The data assimilation uses a reduced order Kalman filter with a 3-D multivariate modal decomposition of the forecast error. It includes an adaptative error and a localization algorithm. A 3D-Var scheme corrects for the slowly evolving large-scale biases in temperature and salinity.

    Altimeter data, satellite temperature and in situ temperature and salinity vertical profiles are jointly assimilated to estimate the initial conditions for the numerical ocean forecasting.

    This paper gives a description of the recent systems. The validation procedure is introduced and applied to the current and future systems. This paper shows how the validation impacts on the quality of the systems. It is shown how quality check (in situ, drifters and data source (satellite temperature impacts as much as the systems design (model physics and assimilation parameters. The validation demonstrates the accuracy of the MyOcean global products. Their quality is stable in time. The future systems under development still suffer from a drift. This could only be detected with a 5 yr hindcast of the systems. This emphasizes the need for continuous research efforts in the process of building future versions of MyOcean2 forecasting capacities.

  16. Road grade quantification based on global positioning system data obtained from real-world vehicle fuel use and emissions measurements

    Science.gov (United States)

    Yazdani Boroujeni, Behdad; Frey, H. Christopher

    2014-03-01

    Real-world vehicle fuel use and emission rates depend on engine load, which is quantified in terms of Vehicle Specific Power (VSP). VSP depends on vehicle speed, acceleration, and road grade. There is not a standard method for measuring road grade from a moving vehicle. A method for quantifying grade is evaluated based on statistical analysis of multiple runs using low cost consumer grade Global Positioning System (GPS) receivers with in-built Barometric Altimeter (GPS/BA). The average grade precision is ±0.71, ±0.46, and ±0.31 percentage points, for sample sizes of 9, 18, and 36 GPS/BA runs, respectively, among 2213 individual 0.08 km road segments. In addition, 4 sets of repeated measurements were performed on the same routes using a high cost, high accuracy Differential GPS (DGPS). Both sets of GPS-based grade estimates compared well with those derived from LIght Detection And Ranging (LIDAR) data. GPS/BA and DGPS grade estimates were similar, except for high magnitude grades of 8-10 percent for which DGPS estimates are more accurate. DGPS is more sensitive to loss of signal; thus, a hybrid approach for substituting GPS/BA data for missing DGPS data at specific locations along a route is demonstrated. The local and overall effects of road grade on fuel use and emission rates are investigated for an example light duty gasoline vehicle.

  17. Inertial Navigation System Standardized Software Development. Volume 1. Introduction and Summary

    Science.gov (United States)

    1976-06-01

    the Loran receiver, the Tacan receiver, the Omega receiver, the satelite based instrumentation, the multimode radar, the star tracker and the visual...accelerometer scale factor, and the barometric altimeter bias. The accuracy (1o values) of typical navigation-aid measurements (other than satelite derived

  18. Developing a global mixed-canopy, height-variable vegetation structure dataset for estimating global vegetation albedo by a clumped canopy radiative transfer scheme in the NASA Ent Terrestrial Biosphere Model and GISS GCM

    Science.gov (United States)

    Montes, Carlo; Kiang, Nancy Y.; Ni-Meister, Wenge; Yang, Wenze; Schaaf, Crystal; Aleinov, Igor; Jonas, Jeffrey A.; Zhao, Feng; Yao, Tian; Wang, Zhuosen; Sun, Qingsong; Carrer, Dominique

    2016-04-01

    Processes determining biosphere-atmosphere coupling are strongly influenced by vegetation structure. Thus, ecosystem carbon sequestration and evapotranspiration affecting global carbon and water balances will depend upon the spatial extent of vegetation, its vertical structure, and its physiological variability. To represent this globally, Dynamic Global Vegetation Models (DGVMs) coupled to General Circulation Models (GCMs) make use of satellite and/or model-based vegetation classifications often composed by homogeneous communities. This work aims at developing a new Global Vegetation Structure Dataset (GVSD) by incorporating varying vegetation heights for mixed plant communities to be used as boundary conditions to the Analytical Clumped Two-Stream (ACTS) canopy radiative transfer scheme (Ni-Meister et al., 2010) incorporated into the NASA Ent Terrestrial Biosphere Model (TBM), the DGVM coupled to the NASA Goddard Institute for Space Studies (GISS) GCM. Information sources about land surface and vegetation characteristics obtained from a number of earth observation platforms and algorithms include the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and plant functional types (PFTs) (Friedl et al., 2010), soil albedo derived from MODIS (Carrer et al., 2014), along with vegetation height from the Geoscience Laser Altimeter System (GLAS) on board ICESat (Ice, Cloud, and land Elevation Satellite) (Simard et al., 2011; Tang et al., 2014). Three widely used Leaf Area Index (LAI) products are compared as input to the GVSD and ACTS forcing in terms of vegetation albedo: Global Data Sets of Vegetation (LAI)3g (Zhu et al. 2013), Beijing Normal University LAI (Yuan et al., 2011), and MODIS MOD15A2H product (Yang et al., 2006). Further PFT partitioning is performed according to a climate classification utilizing the Climate Research Unit (CRU; Harris et al., 2013) and the NOAA Global Precipitation Climatology Centre (GPCC; Scheider et al., 2014) data. Final

  19. System Budgets

    DEFF Research Database (Denmark)

    Jeppesen, Palle

    1996-01-01

    The lecture note is aimed at introducing system budgets for optical communication systems. It treats optical fiber communication systems (six generations), system design, bandwidth effects, other system impairments and optical amplifiers.......The lecture note is aimed at introducing system budgets for optical communication systems. It treats optical fiber communication systems (six generations), system design, bandwidth effects, other system impairments and optical amplifiers....

  20. High-Rate Data-Capture for an Airborne Lidar System

    Science.gov (United States)

    Valett, Susan; Hicks, Edward; Dabney, Philip; Harding, David

    2012-01-01

    A high-rate data system was required to capture the data for an airborne lidar system. A data system was developed that achieved up to 22 million (64-bit) events per second sustained data rate (1408 million bits per second), as well as short bursts (less than 4 s) at higher rates. All hardware used for the system was off the shelf, but carefully selected to achieve these rates. The system was used to capture laser fire, single-photon detection, and GPS data for the Slope Imaging Multi-polarization Photo-counting Lidar (SIMPL). However, the system has applications for other laser altimeter systems (waveform-recording), mass spectroscopy, xray radiometry imaging, high-background- rate ranging lidar, and other similar areas where very high-speed data capture is needed. The data capture software was used for the SIMPL instrument that employs a micropulse, single-photon ranging measurement approach and has 16 data channels. The detected single photons are from two sources those reflected from the target and solar background photons. The instrument is non-gated, so background photons are acquired for a range window of 13 km and can comprise many times the number of target photons. The highest background rate occurs when the atmosphere is clear, the Sun is high, and the target is a highly reflective surface such as snow. Under these conditions, the total data rate for the 16 channels combined is expected to be approximately 22 million events per second. For each photon detection event, the data capture software reads the relative time of receipt, with respect to a one-per-second absolute time pulse from a GPS receiver, from an event timer card with 0.1-ns precision, and records that information to a RAID (Redundant Array of Independent Disks) storage device. The relative time of laser pulse firings must also be read and recorded with the same precision. Each of the four event timer cards handles the throughput from four of the channels. For each detection event, a flag is

  1. The global Mercator Ocean analysis and forecasting high resolution system and its main future updates

    Science.gov (United States)

    Lellouche, Jean-Michel; Legalloudec, Olivier; Bourdallé-Badie, Romain; Garric, Gilles; Greiner, Eric; Drévillon, Marie; Regnier, Charly; Testut, Charles-Emmanuel; Benkiran, Mounir; Drillet, Yann

    2015-04-01

    In April 2013, Mercator Ocean has performed a major upgrade of the global 1/12° high resolution system. This system currently delivers daily services, and includes numerous improvements related to the ocean/sea-ice model and the assimilation scheme. Observations are assimilated by means of a reduced-order Kalman filter with a 3D multivariate modal decomposition of the forecast error. It includes an adaptive-error estimate and a localization algorithm. Altimeter data, satellite Sea Surface Temperature and in situ temperature and salinity vertical profiles are jointly assimilated to estimate the initial conditions for numerical ocean forecasting. A 3D-Var scheme provides a correction for the slowly-evolving large-scale biases in temperature and salinity. In April 2015, Mercator Ocean will open the Copernicus Marine Environment Monitoring Service and will be in charge of the global ocean at eddy resolving resolution. In this context, R&D activities conducted during the end of the MyOcean2 and MyOcean follow-on projects to deliver an improved version of the global system will continue throughout 2015. The main new updates we plan to integrate in the next version of the global system concern: 1) A new vertical mixing scheme k-epsilon: vertical physics has been explored with a special focus on the turbulent closure problem to improve the representation of temperature and salinity in the Mixed Layer Depth. 2) An adaptive tuning of observations errors: as the prescription of observation errors in the assimilation systems is often too approximate, some diagnostics have been developed. These diagnostics consist in the computation of the Desroziers ratio which is a function of observation errors, innovations and residuals. It helps to identify inconsistency on the specified observation errors and to tune an adaptive weight coefficient acting on the error of each assimilated observation. 3) The assimilation of sea-ice concentration observations: it is introduced in the

  2. Lidar remote sensing of savanna biophysical attributes

    Science.gov (United States)

    Gwenzi, David

    Although savanna ecosystems cover approximately 20 % of the terrestrial land surface and can have productivity equal to some closed forests, their role in the global carbon cycle is poorly understood. This study explored the applicability of a past spaceborne Lidar mission and the potential of future missions to estimate canopy height and carbon storage in these biomes. The research used data from two Oak savannas in California, USA: the Tejon Ranch Conservancy in Kern County and the Tonzi Ranch in Santa Clara County. In the first paper we used non-parametric regression techniques to estimate canopy height from waveform parameters derived from the Ice Cloud and land Elevation Satellite's Geoscience Laser Altimeter System (ICESat-GLAS) data. Merely adopting the methods derived for forests did not produce adequate results but the modeling was significantly improved by incorporating canopy cover information and interaction terms to address the high structural heterogeneity inherent to savannas. Paper 2 explored the relationship between canopy height and aboveground biomass. To accomplish this we developed generalized models using the classical least squares regression modeling approach to relate canopy height to above ground woody biomass and then employed Hierarchical Bayesian Analysis (HBA) to explore the implications of using generalized instead of species composition-specific models. Models that incorporated canopy cover proxies performed better than those that did not. Although the model parameters indicated interspecific variability, the distribution of the posterior densities of the differences between composition level and global level parameter values showed a high support for the use of global parameters, suggesting that these canopy height-biomass models are universally (large scale) applicable. As the spatial coverage of spaceborne lidar will remain limited for the immediate future, our objective in paper 3 was to explore the best means of extrapolating

  3. Differential GPS/inertial navigation approach/landing flight test results

    Science.gov (United States)

    Snyder, Scott; Schipper, Brian; Vallot, Larry; Parker, Nigel; Spitzer, Cary

    1992-01-01

    Results of a joint Honeywell/NASA-Langley differential GPS/inertial flight test conducted in November 1990 are discussed focusing on postflight data analysis. The test was aimed at acquiring a system performance database and demonstrating automatic landing based on an integrated differential GPS/INS with barometric and radar altimeters. Particular attention is given to characteristics of DGPS/inertial error and the magnitude of the differential corrections and vertical channel performance with and without altimeter augmentation. It is shown that DGPS/inertial integrated with a radar altimeter is capable of providing a precision approach and autoland guidance of manned return space vehicles within the Space Shuttle accuracy requirements.

  4. HYCOM Consortium for Data-Assimilation Ocean Modeling

    Science.gov (United States)

    2002-09-30

    for data assimilation in oceanography. Journal of Marine Systems , 16, 323-340. Wang, Y.M., 2000: The satellite altimeter data derived mean sea surface GSFC98, Geophysical Research Letters, 27, 701-704. 6

  5. Ku-Band radar penetration into Snow over Arctic Sea Ice

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    Sea ice freeboard measurements are of great interest for basin-scale ice mass balance monitoring. Typically, laser- and radar-altimeters are used for freeboard retrieval in operational systems such as aircrafts and satellites. For laser beams it can be assumed that the dominant reflector......, if radar altimeters are capable of measuring the distance to the snow-ice interface reliably. We present the results of aircraft campaigns in the Arctic with a scanning laser altimeter and the Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) of the European Space Agency. The elevation...... observations are converted into freeboard profiles, taking the different footprints into account when comparing the two systems. Based on the probability distribution of laser and radar freeboard we discuss the specific characteristics of both systems and the apparent radar penetration over sea ice...

  6. Air Data Calibration Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This facility is for low altitude subsonic altimeter system calibrations of air vehicles. Mission is a direct support of the AFFTC mission. Postflight data merge is...

  7. Assessment of wave modeling results with buoy and altimeter deep water waves for a summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Sudheesh, K.; Vethamony, P.; Babu, M.T.; Jayakumar, S.

    stream_size 63122 stream_content_type text/plain stream_name INCHOE_Proc_2004_1_184.pdf.txt stream_source_info INCHOE_Proc_2004_1_184.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 G49G56G52 G65G83... G83G69G83G83G77G69G78G84G32G79G70G32G87G65G86G69G32G77G79G68G69G76G73G78G71G32G82G69G83G85G76G84G83G32G87G73G84G72 G66G85G79G89G32G65G78G68G32G65G76G84G73G77G69G84G69G82G32G68G69G69G80G32G87G65G84G69G82G32G87G65G86G69G83G32G70G79G82G32G65 G83G85G77G...

  8. Long term changes of altimeter range and geophysical corrections at altimetry calibration sites

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Cheng, Yongcun; Pascal Willis

    2013-01-01

    Accurate sea level trend determination is fundamentally related to calibration of both the instrument as well as to investigate if there are linear trends in the set of standard geophysical and range corrections applied to the sea level observations. Long term changes in range corrections can leak...... trends in the sum of range corrections are found for the calibrations sites both for local scales (within 50km around the selected site) and for regional scales (within 300km). However, the geophysical corrections accounting for atmospheric pressure loading and high frequency sea level variations...

  9. Sensitivity, uncertainty analyses and algorithm selection for Sea Ice Thickness retrieval from Radar Altimeter

    CERN Document Server

    Djepa, Vera

    2013-01-01

    For accurate forecast of climate change, sea ice mass balance, ocean circulation and sea- atmosphere interactions is required to have long term records of Sea Ice Thickness (SIT). Different approaches have been applied to retrieve SIT and only satellite altimetry, radar or laser, have been proven to provide hemispheric estimates of SIT distribution over a sufficient thickness range. To simplify the algorithm for SIT retrieval from RA, constant ice density has been applied until now, which lead to different results for derived SIT and SID, in dependence on input information for sea ice density and snow depth. The purpose of this paper is to select algorithm for SID and SIT retrieval from RA, using statistical, sensitivity analyses and independent observations of SID from moored ULS, or on Submarine. The impact of ice density and snow depth on accuracy of the retrieved SIT has been examined, applying sensitivity analyses, and the propagated uncertainties have been summarised. Accuracy of algorithms for snow dep...

  10. 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.

    As bathymetry and geoid are highly correlated in the 50-300 km range, the satellite-derived geoid can be used in the mapping of bathymetry. An attempt has been made to assess the accuracy of predicting sea bottom topography/bathymetry through a...

  11. 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.

  12. 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.

  13. An improved wind speed algorithm for“Jason-1”altimeter under tropical cyclone conditions

    Institute of Scientific and Technical Information of China (English)

    QIN Bangyong; ZHOU Xuan; ZHANG Honglei; YANG Xiaofeng; LU Rong; YU Yang; SHI Lijian

    2014-01-01

    Rain effect and lack of in situ validation data are two main causes of tropical cyclone wind retrieval errors. The National Oceanic and Atmospheric Administration’s Climate Prediction Center Morphing technique (CMORPH) rain rate is introduced to a match-up dataset and then put into a rain correction model to re-move rain effects on“Jason-1”normalized radar cross section (NRCS);Hurricane Research Division (HRD) wind speed, which integrates all available surface weather observations, is used to substitute in situ data for establishing this relationship with“Jason-1”NRCS. Then, an improved“Jason-1”wind retrieval algorithm under tropical cyclone conditions is proposed. Seven tropical cyclones from 2003 to 2010 are studied to validate the new algorithm. The experimental results indicate that the standard deviation of this algorithm at C-band and Ku-band is 1.99 and 2.75 m/s respectively, which is better than the existing algorithms. In addition, the C-band algorithm is more suitable for sea surface wind retrieval than Ku-band under tropical cyclone conditions.

  14. Development and validation of a microchip pulsed laser for ESA space altimeters

    Science.gov (United States)

    Couto, Bruno; Abreu, Hernâni; Gordo, Paulo; Amorim, António

    2016-10-01

    The development and validation of small size laser sources for space based range finding is of crucial importance to the development of miniature LIDAR devices for European space missions, particularly for planet lander probes. In this context, CENTRA-SIM is developing a passively q-switched microchip laser in the 1.5μm wavelength range. Pulses in the order of 2 ns and 100μJ were found to be suitable for range finding for small landing platforms. Both glass and crystalline Yb-Er doped active media are commonly available. Crystalline media present higher thermal conductivity and hardness, which allows for higher pumping intensities. However, glass laser media present longer laser upper-state lifetime and 99% Yb-Er transfer efficiency make phosphate glasses the typically preferred host for this type of application. In addition to this, passively q-switched microchip lasers with Yb-Er doped phosphate glass have been reported to output >100μJ pulses while their crystalline host counterparts achieve a few tens of μJ at best. Two different types of rate equation models have been found: microscopic quantities based models and macroscopic quantities based models. Based on the works of Zolotovskaya et al. and Spühler et al, we have developed a computer model that further exploits the equivalence between the two types of approaches. The simulation studies, using commercial available components allowed us to design a compact laser emitting 80μJ pulses with up to 30kW peak power and 1 to 2 ns pulse width. We considered EAT14 Yb-Er doped glass as active medium and Co2+:MgAl2O4 as saturable absorber. The active medium is pumped by a 975nm semiconductor laser focused into a 200μm spot. Measurements on an experimental test bench to validate the numerical model were carried out. Several different combinations of, saturable absorber length and output coupling were experimented.

  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 bal

  16. Validation of the multi-mission altimeter data for the Baltic Sea region

    CERN Document Server

    Kudryavtseva, N A

    2016-01-01

    We present a complete cross-validation of Significant Wave Heights (SWH) extracted from altimetry data from all ten existing satellites with available in situ (buoy and echosounder) wave measurements for the Baltic Sea basin. The main purpose is to select an adequate altimetry data subset for a subsequent evaluation of the wave climate. The satellite measurements with the backscatter coefficients >13.5, errors in the SWH normalized standard deviation >0.5 m and snapshots with centroids closer than 0.2 degrees to the land are not reliable. The ice flag usually denotes the ice concentration of >50%. The presence of ice affects the SWH data starting from concentrations 10%, but substantial effects are only evident for concentrations >30%. The altimetry data selected based on these criteria have very good correspondence with in situ data, except for GEOSAT Phase 1 data (1985-1989) that could not be validated. The root-mean-square difference and bias of altimetry and in situ data are in the range of 0.23-0.37 and ...

  17. Impacts of altimeter corrections on local linear sea level trends around Taiwan

    DEFF Research Database (Denmark)

    Cheng, Yongcun; Andersen, Ole Baltazar

    2013-01-01

    .e. the inverted barometer correction, wet tropospheric correction, and sea state bias correction, have significant impacts on the determination of local LSLT. The trend of default corrections contribute more than 1.4 mm year-1 along the coastline of China mainland and 2.1 mm year-1 to local LSLT in the Taiwan...

  18. The Potential for Ocean Prediction and the Role of Altimeter Data

    Science.gov (United States)

    1984-01-01

    sateises that have nearly global coverage, but only at the sur- face. Satelites and atmospheric models provide the only clear prospects for flds with...stationany satelite measurements. In: Oreanography from Space. 3. F. R. Gower. -Ed. Plenum Press. New York. 201-206. Grammeltvedt. A. 1969. A survey of finite

  19. An Overview of the Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, M.; Hayes, A.; Lunine, J. I.; Poggiali, V.; Seu, R.; Hofgartner, J. D.; Lorenz, R. D.; Le Gall, A. A.

    2015-12-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's 91stflyby of Titan (T91), the instrument demonstrates its capabilities as a radar sounder, presenting a unique opportunity to constrain direct measurements of the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did return subsurface detections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the interrogated track of the sea. We will present an analysis of all three altimetric observations of Titan's mare, as well a re-analysis of altimetry data acquired over southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo based inversions. Finally, we will show that the estimates obtained from the direct measurements described above can be used along with the RADAR's active (i.e. Synthetic Aperture Radar) and passive (Radiometry) modes to generate bathymetry maps of areas not observed by altimetry.

  20. Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph

    2016-04-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's T91 flyby of Titan, the instrument demonstrated its capabilities as a radar sounder, presenting a unique opportunity to constraint the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did show subsurface reflections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the radar altimetry transect. Herein we present a re-analysis of altimetry data acquired over Ligeia Mare and, earlier in the Cassini mission (in December 2008 during T49), over the southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo-based inversions. Simulation is based on a two-layer model, where the surface is represented by a specular reflection and the seafloor is modeled using a facet-based synthetic surface, including thermal noise, speckle effects, analog to digital conversion (ADC), block adaptive quantization (BAQ), and allows for possible receiver saturation. This new analysis provides an update to the Ku-band attenuation (the Cassini RADAR operates at a wavelength of 2 cm) and results in a new estimate for loss tangent and composition. We found a value of specific attenuation of the liquid equal to 0.14±0.02 dB/m and 0.2±0.1 dB/m, which is equivalent to a loss tangent of 4.4±0.9x10^-5 and 7±3x10^-5 for Ligeia Mare and Ontario Lacus, respectively. Assuming that Titan's liquid bodies are composed by a ternary mixture of methane, ethane, and nitrogen, these values of loss tangent are consistent with a composition of 69% of methane (CH4), 14% of ethane (C2H6) and 17% nitrogen (N2) for Ligeia Mare and 47% of methane (CH4), 40% of ethane (C2H6) and 13% nitrogen (N2) for Ontario Lacus.

  1. On Eddy Viscosity, Energy Cascades, and the Horizontal Resolution of Gridded Satellite Altimeter Products

    Science.gov (United States)

    2013-02-01

    midlatitudes. The v = 0, FL = 0.4 experiment consists of densely packed vorti- ces (e.g., McWilliams 1984), in rough similarity to a typical snapshot of...acknowledge helpful discussions with Dudley Chelton, Joe LaCasce, Roger Samelson, Ted Shepherd, and Alan Wallcraft. BKA received support from Office...O., and M. E. Mclntyre, 2005: Wave capture and wave- vortex duality. J. Fluid Mech., 534, 67-95. Capet, X., J. C. McWilliams , M. J. Molemaker, and

  2. 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.

  3. Gradient systems and mechanical systems

    Institute of Scientific and Technical Information of China (English)

    Fengxiang Mei; Huibin Wu

    2016-01-01

    All types of gradient systems and their properties are discussed. Two problems connected with gradient sys-tems and mechanical systems are studied. One is the direct problem of transforming a mechanical system into a gradi-ent system, and the other is the inverse problem, which is transforming a gradient system into a mechanical system.

  4. Thermal systems; Systemes thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Lalot, S. [Valenciennes Univ. et du Hainaut Cambresis, LME, 59 (France); Lecoeuche, S. [Ecole des Mines de Douai, Dept. GIP, 59 - Douai (France)]|[Lille Univ. des Sciences et Technologies, 59 - Villeneuve d' Ascq (France); Ahmad, M.; Sallee, H.; Quenard, D. [CSTB, 38 - Saint Martin d' Heres (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Gascoin, N.; Gillard, P.; Bernard, S. [Laboratoire d' Energetique, Explosion, Structure, 18 - Bourges (France); Gascoin, N.; Toure, Y. [Laboratoire Vision et Robotique, 18 - Bourges (France); Daniau, E.; Bouchez, M. [MBDA, 18 - Bourges (France); Dobrovicescu, A.; Stanciu, D. [Bucarest Univ. Polytechnique, Faculte de Genie Mecanique (Romania); Stoian, M. [Reims Univ. Champagne Ardenne, Faculte des Sciences, UTAP/LTM, 51 (France); Bruch, A.; Fourmigue, J.F.; Colasson, S. [CEA Grenoble, Lab. Greth, 38 (France); Bontemps, A. [Universite Joseph Fourier, LEGI/GRETh, 38 - Grenoble (France); Voicu, I.; Mare, T.; Miriel, J. [Institut National des Sciences Appliquees (INSA), LGCGM, IUT, 35 - Rennes (France); Galanis, N. [Sherbrooke Univ., Genie Mecanique, QC (Canada); Nemer, M.; Clodic, D. [Ecole des Mines de Paris, Centre Energetique et Procedes, 75 (France); Lasbet, Y.; Auvity, B.; Castelain, C.; Peerhossaini, H. [Nantes Univ., Ecole Polytechnique, Lab. de Thermocinetiquede Nantes, UMR-CNRS 6607, 44 (France)

    2005-07-01

    This session about thermal systems gathers 26 articles dealing with: neural model of a compact heat exchanger; experimental study and numerical simulation of the thermal behaviour of test-cells with walls made of a combination of phase change materials and super-insulating materials; hydraulic and thermal modeling of a supercritical fluid with pyrolysis inside a heated channel: pre-dimensioning of an experimental study; energy analysis of the heat recovery devices of a cryogenic system; numerical simulation of the thermo-hydraulic behaviour of a supercritical CO{sub 2} flow inside a vertical tube; mixed convection inside dual-tube exchangers; development of a nodal approach with homogenization for the simulation of the brazing cycle of a heat exchanger; chaotic exchanger for the cooling of low temperature fuel cells; structural optimization of the internal fins of a cylindrical generator; a new experimental approach for the study of the local boiling inside the channels of exchangers with plates and fins; experimental study of the flow regimes of boiling hydrocarbons on a bundle of staggered tubes; energy study of heat recovery exchangers used in Claude-type refrigerating systems; general model of Carnot engine submitted to various operating constraints; the free pistons Stirling cogeneration system; natural gas supplied cogeneration system with polymer membrane fuel cell; influence of the CRN coating on the heat flux inside the tool during the wood unrolling process; transport and mixture of a passive scalar injected inside the wake of a Ahmed body; control of a laser welding-brazing process by infrared thermography; 2D self-adaptative method for contours detection: application to the images of an aniso-thermal jet; exergy and exergy-economical study of an 'Ericsson' engine-based micro-cogeneration system; simplified air-conditioning of telephone switching equipments; parametric study of the 'low-energy' individual dwelling; brief synthesis of

  5. Data Systems vs. Information Systems

    OpenAIRE

    Amatayakul, Margret K.

    1982-01-01

    This paper examines the current status of “hospital information systems” with respect to the distinction between data systems and information systems. It is proposed that the systems currently existing are incomplete data dystems resulting in ineffective information systems.

  6. Confidence-Based Robot Policy Learning from Demonstration

    Science.gov (United States)

    2009-03-05

    Hierarchical Task Models by Demonstration. Technical Report TR2003-01, Mitsubishi Electric Research Laboratories, 2003. [33] Dylan F. Glas, Takayuki...Journal of Advanced Robotic Systems, 2(4):301–308, 2005. [47] Chris Jones, Dylan Shell, Maja Matarić, and B. Gerkey. Principled approaches to the design of...and Jessica K Hodgins. Generalizing demonstrated manipulation tasks. In Workshop on the Algorithmic Foundations of Robotics, December 2002. [68] Bob

  7. Multibody Systems

    DEFF Research Database (Denmark)

    Wagner, Falko Jens

    1999-01-01

    Multibody Systems is one area, in which methods for solving DAEs are of special interst. This chapter is about multibody systems, why they result in DAE systems and what kind of problems that can arise when dealing with multibody systems and formulating their corresponding DAE system....

  8. Optimal Recovery Trajectories for Automatic Ground Collision Avoidance Systems (Auto GCAS)

    Science.gov (United States)

    2015-03-01

    Optimization Program PSM Pseudospectral Method RadAlt Radar Altimeter RBF Radial Basis Function REO Radar Electro Optical RMSE Root Mean Squared Error...method ( PSM ), also referred to as the Variable-Order Gaussian Quadrature Colloca- tion Method by Rao [69]. The PSM and the accompanying Legendre-Gauss...Radau collocation rule which will be used for this research are summarized here. The PSM is a direct method for solving optimal control problems using

  9. Verden går under mellem et glas mælk og en forsamling af frøer

    DEFF Research Database (Denmark)

    Andersen, Astrid Oberborbeck

    2015-01-01

    I Arequipa, Perus næststørste by, placeret på grænsen til Atacamaørkenen, mellem aktive vulkaner med afsmeltede gletsjere, er forudsigelser om vejr og om fremtid en central del af vejrdagen. Denne artikel udforsker forskellige måder hvorpå mennesker i Arequipa tyder tegn i deres omgivelser...

  10. Een glas-in-lood plafond? ‘De Vrouw 1813-1913’ en andere verbeeldingen van vrouwen, religie en emancipatie

    Directory of Open Access Journals (Sweden)

    Marjet Derks

    2015-06-01

    Full Text Available A Leaded-Glass Ceiling?: ‘Women 1813-1913’ and Other Visions of Women, Religion and EmancipationThe exhibition ‘Women 1813-1913’ was a key moment in the visibility of women’s religiosity in the public realm. However, it was so because it accentuated the feminist framework of women’s formal rights and projected it on the ecclesiastical domain. This one-sided representation, which excluded Catholic women among others, has remained unacknowledged in historiography. Focusing on motivations and aims of female subjects, this article addresses Catholic women’s attempts to gain an authoritative position and have a public voice in the religious realm, despite opposition. It analyses both their resentment of the formal rights discourse and their appropriations. By doing so, the article emphasises the historical diversity of female religious agency and the experience of empowerment, as well as the importance of religion as a category for identity. The last is typified as a source of difference rather than a unifying factor among women, both in 1813 and 1913 and in the twenty-first century. De tentoonstelling ‘De Vrouw 1813-1913’ was een scharnierpunt in dezichtbaarmaking van de religiositeit van vrouwen in de publieke sfeer, maar accentueerde het feministische denkkader van ‘formele rechten’ van vrouwen in de kerken. De geschiedschrijving heeft het eenzijdige karakter van deze representatie, die onder meer katholieke vrouwen uitsloot, niet onderkend. Vertrekkend vanuit de denkkaders van de vrouwelijke subjecten zélf, hun doelstellingen en motivatie, belicht deze bijdrage de pogingen van katholieke vrouwen (religieuze bewegingen, politica’s en feministisch theologen in de jaren ná 1913 om religieuze spreekpositiesin te nemen en de weerstanden die ze ontmoetten. Soms stonden de pogingenhaaks op het rechtendiscours, soms eigenden vrouwen zich dat toe. De bijdrage benadrukt de historische diversiteit van vrouwelijke religieuze agency en ervaringen van empowerment, alsmede het belang van religie voor identiteit. Religie komt erin naar voren als bron van verschil tussen vrouwen, zowel in 1813 en 1913 als een eeuw later.

  11. Glass hybrid elements with translucent interlayers for improving the energy efficiency of building fascades; Glas-Hybrid-Elemente mit transluzenten Zwischenschichten zur Verbesserung der Energieeffizienz von Gebaeudehuellen

    Energy Technology Data Exchange (ETDEWEB)

    Dimmig-Osburg, Andrea; Werner, Frank; Hildebrand, Joerg; Gypser, Alexander; Wittor, Bjoern; Wolf, Martina

    2011-07-01

    The use of daylight is an important issue in the architecture. Previously, the special emphasis was placed on design aspects and the visual comfort. The simultaneous achievement of thermal comfort in buildings often is a conflict of interests. Glass-plastic composite panels can minimize the energy consumption of a building while increasing the comfort. These glass-plastic sandwich elements form an important basic module for the strategic development of sustainable building envelopes. This basic module is based on the decoupling of energy consumption and indoor comfort. In the contribution under consideration, practically applicable elements are developed. These elements should have the necessary capacity for wall elements with wind loads or roof elements with wind loads or snow loads. These elements also should possess thermal insulating properties which make effective use in large-area applications.

  12. A cost-effective adverse-weather precision guidance system

    Energy Technology Data Exchange (ETDEWEB)

    Fellerhoff, R.; Burgett, S.

    1995-08-01

    This SAND report documents the results of an LDRD project undertaken to study the accuracy of terrain-aided navigation coupled with highly accurate topographic maps. A revolutionary new mapping technology, interferometric synthetic aperture radar (IFSAR), has the ability to make terrain maps of extremely high accuracy and spatial resolution, more than an order of magnitude better than currently available DMA map products. Using a laser altimeter and the Sandia Labs Twin Otter Radar Testbed, fix accuracies of less than 3 meters CEP were obtained over urban and natural terrain regions.

  13. Systems effectiveness

    CERN Document Server

    Habayeb, A R

    1987-01-01

    Highlights three principal applications of system effectiveness: hardware system evaluation, organizational development and evaluation, and conflict analysis. The text emphasizes the commonality of the system effectiveness discipline. The first part of the work presents a framework for system effectiveness, partitioning and hierarchy of hardware systems. The second part covers the structure, hierarchy, states, functions and activities of organizations. Contains an extended Appendix on mathematical concepts and also several project suggestions.

  14. 基于LabVIEW/Matlab的AUV半实物仿真系统设计%Design of AUV simulation system based on LabVIEW/Matlab

    Institute of Scientific and Technical Information of China (English)

    赵兴; 李健; 李一博

    2014-01-01

    In order to solve the problem of the establishment of actual experimental environment of large AUV(Autono-mous Underwater Vehicle), and for the testing need of different units of AUV control system, a new AUV semi-physical simulation system is designed based on LabVIEW/Matlab under Windows platform. The simulation system realizes the real-time calculation of AUV’s position and posture based on three-dimensional hydrodynamic model; meanwhile, it makes serial port and Ethernet communication with deck system and master control system by imitating Phins, GAPS, fixed high altimeter, obstacle avoidance sonar, and other sensors, which realizes AUV’s motion simulation and also pro-vides evidences for determining motion control strategy. Experimentation shows that the system model is reasonable, and the given software design is feasible. The established simulation system is flexible to be extended or reduced, which is used successfully in testing experiment of AUV’s control system.%为解决大型自主式水下航行器(Autonomous Underwater Vehicle,AUV)实际实验环境搭建的困难,以及AUV控制系统各单元功能测试的需要,设计了一套新的Windows平台下基于LabVIEW/Matlab的AUV半实物仿真系统。该仿真系统基于三维空间的水动力模型,来实时计算AUV的位置和姿态等信息;同时,模仿Phins、GAPS、定高高度计、避障声呐等传感器,和AUV甲板、主控以及运动控制单元进行串行和以太网络通信,实现了AUV的运动仿真,同时也为制定运动控制策略提供相关依据。大量实验表明,该系统模型较合理,软件设计可行,具有灵活的扩展性和伸缩性,在AUV控制系统测试实验中成功应用。

  15. Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

    Science.gov (United States)

    Ku, Jentung; Robinson, Franklin; Patel, Deepak; Ottenstein, Laura

    2013-01-01

    The second Ice, Cloud, and Land Elevation Satellite mission currently planned by National Aeronautics and Space Administration will measure global ice topography and canopy height using the Advanced Topographic Laser Altimeter System {ATLAS). The ATLAS comprises two lasers; but only one will be used at a time. Each laser will generate between 125 watts and 250 watts of heat, and each laser has its own optimal operating temperature that must be maintained within plus or minus 1 degree Centigrade accuracy by the Laser Thermal Control System (LTCS) consisting of a constant conductance heat pipe (CCHP), a loop heat pipe (LHP) and a radiator. The heat generated by the laser is acquired by the CCHP and transferred to the LHP, which delivers the heat to the radiator for ultimate rejection. The radiator can be exposed to temperatures between minus 71 degrees Centigrade and minus 93 degrees Centigrade. The two lasers can have different operating temperatures varying between plus 15 degrees Centigrade and plus 30 degrees Centigrade, and their operating temperatures are not known while the LTCS is being designed and built. Major challenges of the LTCS include: 1) A single thermal control system must maintain the ATLAS at 15 degrees Centigrade with 250 watts heat load and minus 71 degrees Centigrade radiator sink temperature, and maintain the ATLAS at plus 30 degrees Centigrade with 125 watts heat load and minus 93 degrees Centigrade radiator sink temperature. Furthermore, the LTCS must be qualification tested to maintain the ATLAS between plus 10 degrees Centigrade and plus 35 degrees Centigrade. 2) The LTCS must be shut down to ensure that the ATLAS can be maintained above its lowest desirable temperature of minus 2 degrees Centigrade during the survival mode. No software control algorithm for LTCS can be activated during survival and only thermostats can be used. 3) The radiator must be kept above minus 65 degrees Centigrade to prevent ammonia from freezing using no more

  16. Mountain Search and Rescue with Remotely Piloted Aircraft Systems

    Science.gov (United States)

    Silvagni, Mario; Tonoli, Andrea; Zenerino, Enrico; Chiaberge, Marcello

    2016-04-01

    Remotely Piloted Aircraft Systems (RPAS) also known as Unmanned Aerial Systems (UAS) are nowadays becoming more and more popular in several applications. Even though a complete regulation is not yet available all over the world, researches, tests and some real case applications are wide spreading. These technologies can bring many benefits also to the mountain operations especially in emergencies and harsh environmental conditions, such as Search and Rescue (SAR) and avalanche rescue missions. In fact, during last decade, the number of people practicing winter sports in backcountry environment is increased and one of the greatest hazards for recreationists and professionals are avalanches. Often these accidents have severe consequences leading, mostly, to asphyxia-related death, which is confirmed by the hard drop of survival probability after ten minutes from the burying. Therefore, it is essential to minimize the time of burial. Modern avalanche beacon (ARTVA) interface guides the rescuer during the search phase reducing its time. Even if modern avalanche beacons are valid and reliable, the seeking range influences the rescue time. Furthermore, the environment and morphologic conditions of avalanches usually complicates the rescues. The recursive methodology of this kind of searching offers the opportunity to use automatic device like drones (RPAS). These systems allow performing all the required tasks autonomously, with high accuracy and without exposing the rescuers to additional risks due to secondary avalanches. The availability of highly integrated electronics and subsystems specifically meant for the applications, better batteries, miniaturized payload and, in general, affordable prices, has led to the availability of small RPAS with very good performances that can give interesting application opportunities in unconventional environments. The present work is one of the outcome from the experience made by the authors in RPAS fields and in Mechatronics

  17. Intelligent Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — The autonomous systems (AS) project, led by NASA Ames, is developing software for system operation automation. AS technology will help astronauts make more decisions...

  18. Systemic Assurance

    Science.gov (United States)

    2015-07-31

    storage devices (such as disk drives and SSDs) as well as a wide range of embedded controls. This phenomenon has been labeled the Internet of Things ( IoT ...environment involves interlinking with other systems, working in coalitions, relying on civil infrastructure, and use of personal devices . • Modern systems...The system-of-system approach can also involve use of mobile devices , forward-deployed capabilities for managing and analyzing large amounts of data

  19. Expert System

    DEFF Research Database (Denmark)

    Hildebrandt, Thomas Troels; Cattani, Gian Luca

    2016-01-01

    An expert system is a computer system for inferring knowledge from a knowledge base, typically by using a set of inference rules. When the concept of expert systems was introduced at Stanford University in the early 1970s, the knowledge base was an unstructured set of facts. Today the knowledge b...

  20. Retrofitting Systems

    DEFF Research Database (Denmark)

    Rose, Jørgen

    1997-01-01

    This report gives an overview of the different retrofitting possibilities that are available today. The report looks at both external and internal systems for external wall constructions, roof constructions, floor constructions and foundations. All systems are described in detail in respect to use...... and methods, and the efficiency of the different systems are discussed....

  1. Systems Engineering

    Science.gov (United States)

    Pellerano, Fernando

    2015-01-01

    This short course provides information on what systems engineering is and how the systems engineer guides requirements, interfaces with the discipline leads, and resolves technical issues. There are many system-wide issues that either impact or are impacted by the thermal subsystem. This course will introduce these issues and illustrate them with real life examples.

  2. Operating systems

    CERN Document Server

    Tsichritzis, Dionysios C; Rheinboldt, Werner

    1974-01-01

    Operating Systems deals with the fundamental concepts and principles that govern the behavior of operating systems. Many issues regarding the structure of operating systems, including the problems of managing processes, processors, and memory, are examined. Various aspects of operating systems are also discussed, from input-output and files to security, protection, reliability, design methods, performance evaluation, and implementation methods.Comprised of 10 chapters, this volume begins with an overview of what constitutes an operating system, followed by a discussion on the definition and pr

  3. Cryogenic Systems

    Science.gov (United States)

    Hosoyama, Kenji

    2002-02-01

    In this lecture we discuss the principle of method of cooling to a very low temperature, i.e. cryogenic. The "gas molecular model" will be introduced to explain the mechanism cooling by the expansion engine and the Joule-Thomson expansion valve. These two expansion processes are normally used in helium refrigeration systems to cool the process gas to cryogenic temperature. The reverse Carnot cycle will be discussed in detail as an ideal refrigeration cycle. First the fundamental process of liquefaction and refrigeration cycles will be discussed, and then the practical helium refrigeration system. The process flow of the system and the key components; -compressor, expander, and heat exchanger- will be discussed. As an example of an actual refrigeration system, we will use the cryogenic system for the KEKB superconducting RF cavity. We will also discuss the liquid helium distribution system, which is very important, especially for the cryogenic systems used in accelerator applications. 1 Principles of Cooling and Fundamental Cooling Cycle 2 Expansion engine, Joule-Thomson expansion, kinetic molecular theory, and enthalpy 3 Liquefaction Systems 4 Refrigeration Systems 5 Practical helium liquefier/refrigeration system 6 Cryogenic System for TRISTAN Superconducting RF Cavity

  4. Evaluation of global monitoring and forecasting systems at Mercator Océan

    Directory of Open Access Journals (Sweden)

    J.-M. Lellouche

    2013-01-01

    Full Text Available Since December 2010, the MyOcean global analysis and forecasting system has consisted of the Mercator Océan NEMO global 1/4° configuration with a 1/12° nested model over the Atlantic and the Mediterranean. The open boundary data for the nested configuration come from the global 1/4° configuration at 20° S and 80° N.

    The data are assimilated by means of a reduced-order Kalman filter with a 3-D multivariate modal decomposition of the forecast error. It includes an adaptive-error estimate and a localization algorithm. A 3-D-Var scheme provides a correction for the slowly evolving large-scale biases in temperature and salinity. Altimeter data, satellite sea surface temperature and in situ temperature and salinity vertical profiles are jointly assimilated to estimate the initial conditions for numerical ocean forecasting. In addition to the quality control performed by data producers, the system carries out a proper quality control on temperature and salinity vertical profiles in order to minimise the risk of erroneous observed profiles being assimilated in the model.

    This paper describes the recent systems used by Mercator Océan and the validation procedure applied to current MyOcean systems as well as systems under development. The paper shows how refinements or adjustments to the system during the validation procedure affect its quality. Additionally, we show that quality checks (in situ, drifters and data sources (satellite sea surface temperature have as great an impact as the system design (model physics and assimilation parameters. The results of the scientific assessment are illustrated with diagnostics over the year 2010 mainly, assorted with time series over the 2007–2011 period. The validation procedure demonstrates the accuracy of MyOcean global products, whose quality is stable over time. All monitoring systems are close to altimetric observations with a forecast RMS difference of 7 cm. The update of the mean

  5. Haze-factor maakt plaats voor F-scatter

    NARCIS (Netherlands)

    Swinkels, G.L.A.M.

    2014-01-01

    Uitgelicht licht & scherming - Wageningen UR Glastuinbouw deed vorig jaar onderzoek naar een methode om de lichtspreiding onder diffuus glas te karakteriseren. dit resulteerde in een nieuwe waarde, de zogenaamde F-scatter voor voorwaartse lichtspreiding. Leveranciers van glas en schermdoekmateri

  6. Basic development of a small balloon-mounted telemetry and its operation system by university students

    Science.gov (United States)

    Yamamoto, Masa-yuki; Kakinami, Yoshihiro; Kono, Hiroki

    In Japan, the high altitude balloon for scientific observation has been continuously launched by JAXA. The balloon has a possibility to reach 50 km altitude without tight environmental condition for onboard equipments, operating with a cost lower than sounding rockets, however, development of the large-scale scientific observation balloons by university laboratories is still difficult. Being coupled with recent improvement of semiconductor sensors, laboratory-basis balloon experiments using small weather balloons has been becoming easily in these years. Owing to an advantage of wide land fields in continental regions, the launch of such small balloons has become to be carried out many times especially in continental countries (e.g. Near Space Ventures, Inc., 2013). Although the balloon is very small as its diameter of 6 feet, excluding its extra buoyancy and the weight of the balloon itself, it is expected that about 2 kg loading capacity is remained for payloads to send it up to about 35 km altitude. However, operation of such balloons in Japan is not in general because precise prediction of a landing area of the payload is difficult, thus high-risk situation for balloon releases is remained. In this study, we aim to achieve practical engineering experiments of weather balloons in Japan to be used for scientific observation within university laboratory level as an educational context. Here we report an approach of developing many devices for a small tethered balloon currently in progress. We evaluated an accuracy of altitude measurement by using a laboratory developed altitude data logger system that consists of a GPS-module and a barometric altimeter. Diameter of the balloon was about 1.4 m. Being fulfilled with about 1440 L helium, it produced buoyancy of about 15.7 N. Taking into account of total weight including the mooring equipments, available payload mass becomes to be about 1100 g. Applying an advantage of a 3D printer of FDM (Fused Deposition Modeling

  7. Material Systems

    DEFF Research Database (Denmark)

    Jensen, Mads Brath; Mortensen, Henrik Rubæk; Mullins, Michael;

    2009-01-01

    This paper describes and reflects upon the results of an investigative project which explores the setting up of a material system - a parametric and generative assembly consisting of and taking into consideration material properties, manufacturing constraints and geometric behavior. The project...... approaches the subject through the construction of a logic-driven system aiming to explore the possibilities of a material system that fulfills spatial, structural and performative requirements concurrently and how these are negotiated in situations where they might be conflicting....

  8. Recommender systems

    CERN Document Server

    Kembellec, Gérald; Saleh, Imad

    2014-01-01

    Acclaimed by various content platforms (books, music, movies) and auction sites online, recommendation systems are key elements of digital strategies. If development was originally intended for the performance of information systems, the issues are now massively moved on logical optimization of the customer relationship, with the main objective to maximize potential sales. On the transdisciplinary approach, engines and recommender systems brings together contributions linking information science and communications, marketing, sociology, mathematics and computing. It deals with the understan

  9. Energetic Systems

    Data.gov (United States)

    Federal Laboratory Consortium — The Energetic Systems Division provides full-spectrum energetic engineering services (project management, design, analysis, production support, in-service support,...

  10. Intelligent systems

    CERN Document Server

    Irwin, J David

    2011-01-01

    Technology has now progressed to the point that intelligent systems are replacing humans in the decision making processes as well as aiding in the solution of very complex problems. In many cases intelligent systems are already outperforming human activities. Artificial neural networks are not only capable of learning how to classify patterns, such images or sequence of events, but they can also effectively model complex nonlinear systems. Their ability to classify sequences of events is probably more popular in industrial applications where there is an inherent need to model nonlinear system

  11. Systemic darwinism.

    Science.gov (United States)

    Winther, Rasmus Grønfeldt

    2008-08-19

    Darwin's 19th century evolutionary theory of descent with modification through natural selection opened up a multidimensional and integrative conceptual space for biology. We explore three dimensions of this space: explanatory pattern, levels of selection, and degree of difference among units of the same type. Each dimension is defined by a respective pair of poles: law and narrative explanation, organismic and hierarchical selection, and variational and essentialist thinking. As a consequence of conceptual debates in the 20th century biological sciences, the poles of each pair came to be seen as mutually exclusive opposites. A significant amount of 21st century research focuses on systems (e.g., genomic, cellular, organismic, and ecological/global). Systemic Darwinism is emerging in this context. It follows a "compositional paradigm" according to which complex systems and their hierarchical networks of parts are the focus of biological investigation. Through the investigation of systems, Systemic Darwinism promises to reintegrate each dimension of Darwin's original logical space. Moreover, this ideally and potentially unified theory of biological ontology coordinates and integrates a plurality of mathematical biological theories (e.g., self-organization/structure, cladistics/history, and evolutionary genetics/function). Integrative Systemic Darwinism requires communal articulation from a plurality of perspectives. Although it is more general than these, it draws on previous advances in Systems Theory, Systems Biology, and Hierarchy Theory. Systemic Darwinism would greatly further bioengineering research and would provide a significantly deeper and more critical understanding of biological reality.

  12. Immune System

    NARCIS (Netherlands)

    Kuper, C.F.; Ruehl-Fehlert, C.; Elmore, S.A.; Parker, G.A.

    2013-01-01

    Cells of the immune system are found in every organ, from the classic lymphoid organs to tissues such as liver, mucosae, and omental adipose tissue. Toxicity to the immune system may be from a direct or indirect injury to lymphoid organs. The morphological responses range from lymphocyte depletion t

  13. Linear Systems.

    Science.gov (United States)

    The report documents a series of seminars at Rome Air Development Center with the content equivalent to an intense course in Linear Systems . Material...is slanted toward the practicing engineer and introduces some of the fundamental concepts and techniques for analyzing linear systems . Techniques for

  14. Caste System

    OpenAIRE

    Hoff, Karla

    2016-01-01

    In standard economics, individuals are rational actors and economic forces undermine institutions that impose large inefficiencies. The persistence of the caste system is evidence of the need for psychologically more realistic models of decision-making in economics. The caste system divides South Asian society into hereditary groups whose lowest ranks are represented as innately polluted. ...

  15. cardiovascular system

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    6.1 Cardiac arrhythmias 2006037 Electroanatomical systems guided circumferential pulmonary veins ablation for atrial fibrillation: initial experience from comparison between the EnSite -NavX and CARTO system LIU Xu(刘旭 ), et al. Dept Cardiol, Shanghai Chest Hosp, Shanghai, 200030, China. Chin J Cardiol 2005; 33 (22): 975 -978.

  16. Power system

    Science.gov (United States)

    Hickam, Christopher Dale

    2008-03-18

    A power system includes a prime mover, a transmission, and a fluid coupler having a selectively engageable lockup clutch. The fluid coupler may be drivingly connected between the prime mover and the transmission. Additionally, the power system may include a motor/generator drivingly connected to at least one of the prime mover and the transmission. The power-system may also include power-system controls configured to execute a control method. The control method may include selecting one of a plurality of modes of operation of the power system. Additionally, the control method may include controlling the operating state of the lockup clutch dependent upon the mode of operation selected. The control method may also include controlling the operating state of the motor/generator dependent upon the mode of operation selected.

  17. Reactive Systems

    DEFF Research Database (Denmark)

    Aceto, Luca; Ingolfsdottir, Anna; Larsen, Kim Guldstrand

    A reactive system comprises networks of computing components, achieving their goals through interaction among themselves and their environment. Thus even relatively small systems may exhibit unexpectedly complex behaviours. As moreover reactive systems are often used in safety critical systems......, the need for mathematically based formal methodology is increasingly important. There are many books that look at particular methodologies for such systems. This book offers a more balanced introduction for graduate students and describes the various approaches, their strengths and weaknesses, and when...... they are best used. Milner's CCS and its operational semantics are introduced, together with the notions of behavioural equivalences based on bisimulation techniques and with recursive extensions of Hennessy-Milner logic. In the second part of the book, the presented theories are extended to take timing issues...

  18. Physical Systems

    CERN Document Server

    Belkind, Ori

    2012-01-01

    Based on the concept of a physical system, this book offers a new philosophical interpretation of classical mechanics and the Special Theory of Relativity. According to Belkind's view the role of physical theory is to describe the motions of the parts of a physical system in relation to the motions of the whole. This approach provides a new perspective into the foundations of physical theory, where motions of parts and wholes of physical systems are taken to be fundamental, prior to spacetime, material properties and laws of motion. He defends this claim with a constructive project, deriving b

  19. Dynamical systems

    CERN Document Server

    Sternberg, Shlomo

    2010-01-01

    Celebrated mathematician Shlomo Sternberg, a pioneer in the field of dynamical systems, created this modern one-semester introduction to the subject for his classes at Harvard University. Its wide-ranging treatment covers one-dimensional dynamics, differential equations, random walks, iterated function systems, symbolic dynamics, and Markov chains. Supplementary materials offer a variety of online components, including PowerPoint lecture slides for professors and MATLAB exercises.""Even though there are many dynamical systems books on the market, this book is bound to become a classic. The the

  20. Avionics Systems

    Directory of Open Access Journals (Sweden)

    P.M. Soundar Rajan

    2013-03-01

    Full Text Available ‘Avionics’ systems, over the decades, have grown from simple communication radios and navigation equipments to complex integrated equipments primarily infiuenced by dominance of digital technology. Continuous growth in integrated circuit technology, functional integration of complete system on chip, very high speed communication channels and fault tolerant communication protocols have brought remarkable advancements in avionics systems. Further Mechanical and Pneumatic functional blocks are being replaced by digital systems progressively and decisively. New generation aircraft are being built around powerful avionics assets to provide stress free cockpit to the pilot.Defence Science Journal, 2013, 63(2, pp.129-130, DOI:http://dx.doi.org/10.14429/dsj.63.4269

  1. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

    This monograph presents a systematic analysis of bubble system mathematics, using the mechanics of two-phase systems in non-equilibrium as the scope of analysis. The author introduces the thermodynamic foundations of bubble systems, ranging from the fundamental starting points to current research challenges. This book addresses a range of topics, including description methods of multi-phase systems, boundary and initial conditions as well as coupling requirements at the phase boundary. Moreover, it presents a detailed study of the basic problems of bubble dynamics in a liquid mass: growth (dynamically and thermally controlled), collapse, bubble pulsations, bubble rise and breakup. Special emphasis is placed on bubble dynamics in turbulent flows. The analysis results are used to write integral equations governing the rate of vapor generation (condensation) in non-equilibrium flows, thus creating a basis for solving a number of practical problems. This book is the first to present a comprehensive theory of boil...

  2. AEG System -

    Data.gov (United States)

    Department of Transportation — The AEG System is used to create, revise, approve, and distribute text of the AEGS and Flight Standard Board (FSB)/Type Rating Report. The MMEL specifies under what...

  3. Recommender Systems

    CERN Document Server

    Lü, Linyuan; Yeung, Chi Ho; Zhang, Yi-Cheng; Zhang, Zi-Ke; Zhou, Tao

    2012-01-01

    The ongoing rapid expansion of the Internet greatly increases the necessity of effective recommender systems for filtering the abundant information. Extensive research for recommender systems is conducted by a broad range of communities including social and computer scientists, physicists, and interdisciplinary researchers. Despite substantial theoretical and practical achievements, unification and comparison of different approaches are lacking, which impedes further advances. In this article, we review recent developments in recommender systems and discuss the major challenges. We compare and evaluate available algorithms and examine their roles in the future developments. In addition to algorithms, physical aspects are described to illustrate macroscopic behavior of recommender systems. Potential impacts and future directions are discussed. We emphasize that recommendation has a great scientific depth and combines diverse research fields which makes it of interests for physicists as well as interdisciplinar...

  4. Systems failure.

    OpenAIRE

    Macleod, Anna

    1998-01-01

    Systems Failure A solo exhibition of new work by Anna Macleod developed in conversation with curator Liz Burns. The Dock, Carrick on Shannon, Co Leitrim. Ireland. 12th February – 17th April 2010. The works for the exhibition Systems Failure include drawings, prints and small constructions that examine the delicate balance that exists between need and aspects of failure rooted in the relationship between humanity and land use. The work seeks to question the relationship between scient...

  5. Nanorobotic Systems

    Directory of Open Access Journals (Sweden)

    Lixin Dong

    2008-11-01

    Full Text Available Two strategies towards the realization of nanotechnology have been presented, i.e., top-down and bottom up. The former one is mainly based on nanofabrication and includes technologies such as nano-lithography, nano-imprint, and etching. Presently, they are still 2D fabrication processes with low resolution. The later one is an assembly-based technique. At present, it includes such items as self-assembly, dip-pen lithography, and directed self-assembly. These techniques can generate regular nano patterns in large scales. To fabricate 3D complex nano devices there are still no effective ways by so far. Here we show our effort on the development of a nano laboratory, a prototype nanomanufacturing system, based on nanorobotic manipulations. In which, we take a hybrid strategy as shown in Fig. 1. In this system, nano fabrication and nano assembly can be performed in an arbitrary order to construct nano building blocks and finally nano devices. The most important feature in this system is that the products can be fed back into the system to shrink the system part by part leading to nanorobots. Property characterization can be performed in each intermediate process. Due to the nanorobotic manipulation system, dynamic measurement can be performed rather than conventional static observations.

  6. System-of-Systems Complexity

    Directory of Open Access Journals (Sweden)

    Hermann Kopetz

    2013-11-01

    Full Text Available The global availability of communication services makes it possible to interconnect independently developed systems, called constituent systems, to provide new synergistic services and more efficient economic processes. The characteristics of these new Systems-of-Systems are qualitatively different from the classic monolithic systems. In the first part of this presentation we elaborate on these differences, particularly with respect to the autonomy of the constituent systems, to dependability, continuous evolution, and emergence. In the second part we look at a SoS from the point of view of cognitive complexity. Cognitive complexity is seen as a relation between a model of an SoS and the observer. In order to understand the behavior of a large SoS we have to generate models of adequate simplicity, i.e, of a cognitive complexity that can be handled by the limited capabilities of the human mind. We will discuss the importance of properly specifying and placing the relied-upon message interfaces between the constituent systems that form an open SoS and discuss simplification strategies that help to reduce the cognitive complexity.

  7. Systems Studies

    Energy Technology Data Exchange (ETDEWEB)

    Graham, R.L.

    1998-03-17

    The Systems Studies Activity had two objectives: (1) to investigate nontechnical barriers to the deployment of biomass production and supply systems and (2) to enhance and extend existing systems models of bioenergy supply and use. For the first objective, the Activity focused on existing bioenergy markets. Four projects were undertaken: a comparative analysis of bioenergy in Sweden and Austria; a one-day workshop on nontechnical barriers jointly supported by the Production Systems Activity; the development and testing of a framework for analyzing barriers and drivers to bioenergy markets; and surveys of wood pellet users in Sweden, Austria and the US. For the second objective, two projects were undertaken. First, the Activity worked with the Integrated BioEnergy Systems (TBS) Activity of TEA Bioenergy Task XIII to enhance the BioEnergy Assessment Model (BEAM). This model is documented in the final report of the IBS Activity. The Systems Studies Activity contributed to enhancing the feedstock portion of the model by developing a coherent set of willow, poplar, and switchgrass production modules relevant to both the US and the UK. The Activity also developed a pretreatment module for switchgrass. Second, the Activity sponsored a three-day workshop on modeling bioenergy systems with the objectives of providing an overview of the types of models used to evaluate bioenergy and promoting communication among bioenergy modelers. There were nine guest speakers addressing different types of models used to evaluate different aspects of bioenergy, ranging from technoeconomic models based on the ASPEN software to linear programming models to develop feedstock supply curves for the US. The papers from this workshop have been submitted to Biomass and Bioenergy and are under editorial review.

  8. Systemic trauma.

    Science.gov (United States)

    Goldsmith, Rachel E; Martin, Christina Gamache; Smith, Carly Parnitzke

    2014-01-01

    Substantial theoretical, empirical, and clinical work examines trauma as it relates to individual victims and perpetrators. As trauma professionals, it is necessary to acknowledge facets of institutions, cultures, and communities that contribute to trauma and subsequent outcomes. Systemic trauma-contextual features of environments and institutions that give rise to trauma, maintain it, and impact posttraumatic responses-provides a framework for considering the full range of traumatic phenomena. The current issue of the Journal of Trauma & Dissociation is composed of articles that incorporate systemic approaches to trauma. This perspective extends conceptualizations of trauma to consider the influence of environments such as schools and universities, churches and other religious institutions, the military, workplace settings, hospitals, jails, and prisons; agencies and systems such as police, foster care, immigration, federal assistance, disaster management, and the media; conflicts involving war, torture, terrorism, and refugees; dynamics of racism, sexism, discrimination, bullying, and homophobia; and issues pertaining to conceptualizations, measurement, methodology, teaching, and intervention. Although it may be challenging to expand psychological and psychiatric paradigms of trauma, a systemic trauma perspective is necessary on both scientific and ethical grounds. Furthermore, a systemic trauma perspective reflects current approaches in the fields of global health, nursing, social work, and human rights. Empirical investigations and intervention science informed by this paradigm have the potential to advance scientific inquiry, lower the incidence of a broader range of traumatic experiences, and help to alleviate personal and societal suffering.

  9. Temporal and spatial changes of Laika Glacier, Canadian Arctic, since 1959, inferred from satellite remote sensing and mass-balance modelling

    Science.gov (United States)

    Huss, Matthias; Stöckli, Reto; Kappenberger, Giovanni; Blatter, Heinz

    The retreat of Laika Glacier (4.4 km2), part of a small ice cap situated on Coburg Island, Canadian Arctic Archipelago, is analyzed using field data, satellite remote sensing and mass-balance modelling. We present a methodology for merging various data types and numerical models and investigate the temporal and spatial changes of a remote glacier during the past five decades. A glacier mass-balance and surface-evolution model is run for the period 1959-2006, forced with in situ weather observations and climate re-analysis data (ERA-40, NARR). The model is calibrated using the ice-volume change observed between 1959 and 1971, and measured seasonal mass balances. Calculated glacier surface elevation is validated against ICESat GLAS altimeter data and ASTER-derived elevation. Landsat-derived glacier outlines are used to validate calculated ice extent. The piedmont tongue of Laika Glacier has retreated considerably and is in a state of disintegration. The modelled glacier mass balance between 1959 and 2006 was -0.41 m w.e.a-1, on average. Model results indicate a significant trend towards higher mass-balance gradients. A complete wastage of Laika Glacier by 2100 is predicted by model runs based on climate scenarios.

  10. Turbine system

    Energy Technology Data Exchange (ETDEWEB)

    McMahan, Kevin Weston; Dillard, Daniel Jackson

    2016-05-03

    A turbine system is disclosed. The turbine system includes a transition duct having an inlet, an outlet, and a passage extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The turbine system further includes a turbine section connected to the transition duct. The turbine section includes a plurality of shroud blocks at least partially defining a hot gas path, a plurality of buckets at least partially disposed in the hot gas path, and a plurality of nozzles at least partially disposed in the hot gas path. At least one of a shroud block, a bucket, or a nozzle includes means for withstanding high temperatures.

  11. Cognitive Systems

    DEFF Research Database (Denmark)

    user models and user interaction models. Research in cognitive information processing is inherently multi-disciplinary and involves natural science and technical disciplines, e.g., control, automation, and robot research, physics and computer science, as well as humanities such as social sciences......The tutorial will discuss the definition of cognitive systems as the possibilities to extend the current systems engineering paradigm in order to perceive, learn, reason and interact robustly in open-ended changing environments. I will also address cognitive systems in a historical perspective...... and its relation and potential over current artificial intelligence architectures. Machine learning models that learn from data and previous knowledge will play an increasingly important role in all levels of cognition as large real world digital environments (such as the Internet) usually are too complex...

  12. Microbiology System

    Science.gov (United States)

    1992-01-01

    Technology originating in a NASA-sponsored study of the measurement of microbial growth in zero gravity led to the development of Biomerieux Vitek, Inc.'s VITEK system. VITEK provides a physician with accurate diagnostic information and identifies the most effective medication. Test cards are employed to identify organisms and determine susceptibility to antibiotics. A photo-optical scanner scans the card and monitors changes in the growth of cells contained within the card. There are two configurations - VITEK and VITEK JR as well as VIDAS, a companion system that detects bacteria, viruses, etc. from patient specimens. The company was originally created by McDonnell Douglas, the NASA contractor.

  13. Lubrication system

    Energy Technology Data Exchange (ETDEWEB)

    Wadding, C.; Lagasse, N.L.; Milo, G.T.; Vankamerik, J.G.

    1986-02-11

    This patent describes a lubrication system for controlling the flow of lubricant as a function of the altitude at which a gas turbine engine is operating. This lubrication system is comprised of: 1.) A source of lubricant under pressure; 2.) A unit requiring lubrication; 3.) A movable valve in fluid communication with the source and with the unit for regulating the flow of lubricant from the source to the unit; and 4.) An altitude sensor associated with the movable valve for positioning the movable valve to control the flow of lubricant from the source to the unit, as a function of the altitude at which the engine is operating.

  14. System Description:

    DEFF Research Database (Denmark)

    Schürmann, Carsten; Poswolsky, Adam

    2009-01-01

    Delphin is a functional programming language [Adam Poswolsky and Carsten Schürmann. Practical programming with higher-order encodings and dependent types. In European Symposium on Programming (ESOP), 2008] utilizing dependent higher-order datatypes. Delphin's two-level type-system cleanly separates...... data from computation, allowing for decidable type checking. The data level is LF [Robert Harper, Furio Honsell, and Gordon Plotkin. A framework for defining logics. Journal of the Association for Computing Machinery, 40(1):143-184, January 1993], which allows for the specification of deductive systems...

  15. [Systemic scleroderma].

    Science.gov (United States)

    Hunzelmann, N

    2013-04-01

    Systemic scleroderma is a chronic autoimmune disease affecting the skin, internal organs and the musculoskeletal system. The presence of Raynaud phenomenon, anti-nuclear antibodies and pathologic capillaroscopy are early signs of the disease. Limited cutaneous SSc, diffuse cutaneous SSc and SSc-overlap syndromes are the main clinical subtypes. Multidisciplinary care is mandatory. Follow-up examinations should be performed at least annually in order to recognize in a timely fashion treatable organ involvement such as pulmonary arterial hypertension. Besides symptomatic treatment of organ involvement, immunosuppressive therapy is indicated for a progressive inflammatory course.

  16. Computer systems

    Science.gov (United States)

    Olsen, Lola

    1992-01-01

    In addition to the discussions, Ocean Climate Data Workshop hosts gave participants an opportunity to hear about, see, and test for themselves some of the latest computer tools now available for those studying climate change and the oceans. Six speakers described computer systems and their functions. The introductory talks were followed by demonstrations to small groups of participants and some opportunities for participants to get hands-on experience. After this familiarization period, attendees were invited to return during the course of the Workshop and have one-on-one discussions and further hands-on experience with these systems. Brief summaries or abstracts of introductory presentations are addressed.

  17. Numerical experiments of dynamical processes during the 2011-2013 surge of the Bering-Bagley Glacier System, using a full-Stokes finite element model

    Science.gov (United States)

    Trantow, Thomas

    The Bering-Bagley Glacial System (BBGS) is the largest glacier system outside of the Greenland and Antarctic ice sheets, and is the Earth's largest surge-type glacier. Surging is one of three types of glacial acceleration and the least understood one. Understanding glacial acceleration is paramount when trying to explain ice discharge to the oceans and the glacial contribution to sea-level rise, yet there are currently no numerical glacial models that account for surging. The recent 2011-2013 surge of the BBGS provides a rare opportunity to study the surge process through observations and the subsequent data analysis and numerical modeling. Using radar, altimeter, and image data collected from airborne and satellite missions, various descriptions of ice geometry are created at different times throughout the surge. Using geostatistical estimation techniques including variography and ordinary kriging, surface and bedrock Digital Elevation Maps (DEMs) are derived. A time series analysis of elevation change during the current surge is then conducted and validated using a complete error analysis along with airborne observations. The derived DEMs are then used as inputs to a computer simulated model of glacier dynamics in the BBGS. Using the Finite Element software Elmer/Ice, a full-Stokes simulation, with Glen's flow law for temperate ice, is created for numerical experiments. With consideration of free surface evolution, glacial hydrology and surface mass balance, the model is able to predict a variety of field variables including velocity, stress, strain-rate, pressure and surface elevation change at any point forward in time. These outputs are compared and validated using observational data such as CryoSat-2 altimetry, airborne field data, imagery and previous detailed analysis of the BBGS. Preliminary results reveal that certain surge phenomena such as surface elevation changes, surge progression and locations at which the surge starts, can be recreated using the

  18. Systems chemistry

    NARCIS (Netherlands)

    Ludlow, R. Frederick; Otto, Sijbren

    2008-01-01

    The study of complex mixtures of interacting synthetic molecules has historically not received much attention from chemists, even though research into complexity is well established in the neighbouring fields. However, with the huge recent interest in systems biology and the availability of modern a

  19. Solar system

    CERN Document Server

    Homer, Charlene

    2007-01-01

    Thrill young astronomers with a journey through our Solar System. Find out all about the Inner and Outer Planets, the Moon, Stars, Constellations, Asteroids, Meteors and Comets. Using simplified language and vocabulary, concepts such as planetary orbits, the asteroid belt, the lunar cycle and phases of the moon, and shooting stars are all explored.

  20. Transport system

    NARCIS (Netherlands)

    Drenth, K.F.

    1999-01-01

    The transport system comprises at least one road surface (2) and at least one vehicle (4) on wheels (6). The road surface (2) has a substantially bowl-shaped cross section and the vehicle (4) is designed so that the wheels (6) run directly on the road surface (2) while the road surface (2) acts as a

  1. Immune System

    Science.gov (United States)

    ... and mature there to become B cells or leave for the thymus gland, where they mature to become T cells. B lymphocytes and T lymphocytes have separate jobs to do: B lymphocytes are like the body's military intelligence system, seeking out their targets and sending defenses to ...

  2. System Dynamics

    Science.gov (United States)

    Morecroft, John

    System dynamics is an approach for thinking about and simulating situations and organisations of all kinds and sizes by visualising how the elements fit together, interact and change over time. This chapter, written by John Morecroft, describes modern system dynamics which retains the fundamentals developed in the 1950s by Jay W. Forrester of the MIT Sloan School of Management. It looks at feedback loops and time delays that affect system behaviour in a non-linear way, and illustrates how dynamic behaviour depends upon feedback loop structures. It also recognises improvements as part of the ongoing process of managing a situation in order to achieve goals. Significantly it recognises the importance of context, and practitioner skills. Feedback systems thinking views problems and solutions as being intertwined. The main concepts and tools: feedback structure and behaviour, causal loop diagrams, dynamics, are practically illustrated in a wide variety of contexts from a hot water shower through to a symphony orchestra and the practical application of the approach is described through several real examples of its use for strategic planning and evaluation.

  3. Irrigation System

    Science.gov (United States)

    1984-01-01

    Under contract with Marshall Space Flight Center, Midwest Research Institute compiled a Lubrication Handbook intended as a reference source for designers and manufacturers of aerospace hardware and crews responsible for maintenance of such equipment. Engineers of Lindsay Manufacturing Company learned of this handbook through NASA Tech Briefs and used it for supplemental information in redesigning gear boxes for their center pivot agricultural irrigation system.

  4. Immune System

    Science.gov (United States)

    A properly functioning immune system is essential to good health. It defends the body against infectious agents and in some cases tumor cells. Individuals with immune deficiencies resulting from genetic defects, diseases (e.g., AIDS, leukemia), or drug therapies are more suscepti...

  5. Jupiter Magnetospheric Orbiter and Trojan Asteroid Explorer in EJSM (Europa Jupiter System Mission)

    Science.gov (United States)

    Sasaki, Sho; Fujimoto, Masaki; Takashima, Takeshi; Yano, Hajime; Kasaba, Yasumasa; Takahashi, Yukihiro; Kimura, Jun; Tsuda, Yuichi; Funase, Ryu; Mori, Osamu

    2010-05-01

    thick. Currently we are studying a mission to Jupiter and one (or two) of Trojan asteroids using a large (100m-scale) solar power sail that can transfer large payload mass as far as Jupiter. Trojan asteroids are primitive bodies with information of the early solar system as well as raw solid materials of Jovian system. According to the mission plan, as the main spacecraft flies by Jupiter, it will deploy a JMO spinner around Jupiter. Proposed instruments on board Trojan spacecraft are cameras, IR spectrometers, XRS, a laser altimeter, and a surface vehicle (if rendezvous with the target is possible). An instrument for measuring cosmic background is also proposed. Currently JEO and JGO will be launched in 2020 and the Trojan spacecraft with JMO shall be launched at the same window. The mission (Trojan-JMO) will take 6 years to Jupiter and 5 years more to a Trojan asteroid around L4. The mission study team also includes J. Kawaguchi, Y. Kawakatsu, and M. Morimoto of JAXA.

  6. Recent elevation changes on the Lambert-Amery system in East Antarctica from ICESat crossover analysis%基于ICESat轨道交叉点分析的东南极Lambert-Amery系统当前高程变化特征分析

    Institute of Scientific and Technical Information of China (English)

    沈强; 陈刚; 鄂栋臣; 周春霞

    2011-01-01

    南极冰盖物质平衡仍然是全球海平面变化估计的最大不确定因素.本文使用2003~2007年ICESat/GLAS获取的高精度冰盖测高数据,利用我们开发的高精度高程变化提取程序,首次获取了东南极最大冰流系统-Lambert-Amery地区在ICESat卫星轨道交叉点处的高程变化序列.依据冰川动力学原理,对该流域进行详细划分,并在此基础上利用回归模型研究各子区域内高程年际变化特征.对该区域的研究有以下新的认识:(1)除Amery冰架区域(AIS)外,其他区域高程年际变化呈正增长;(2)各子区域高程的年际变化特征呈现显著的区域变化特征,AIS和MGLup的年际变化分别为-6.1 cm/a和6.6 cm/a.(3)流域西侧的高程变化是东部的2~3倍.研究第一次以高密度和高时间分辨率获取了该区域高程变化的时间序列,并采用回归模型详细分析了各子区域高程的年际变化特征.%Mass balance of Antarctic ice sheet remains the largest source of uncertainty in estimation of global sea level change. Depending on our developed procedure on the basis of crossover analysis method, the current short-term rates of elevation change in Lambert-Amery system have been evaluated using ICESat/GLAS altimetry data over the period 2003 ~ 2007 comprising 10 ICESat observation periods. The interannual variability of elevation has been obtained in sub-regions of Lambert-Amery System (LAS), which are defined and calibrated on principle of glacier dynamics, using regression analysis method. We get the new conclusions shown as follows: (1) the elevations are almost increasing in all sub-regions except for AIS subregion; (2) It is very obvious that there are largely regional variations of elevation in the sub-regions, the largest interannual variability of elevation in AIS and MGLup are -6. 1 cm/a and 6. 6 cm/a respectively; (3)Interannual variation of elevation in western LAS is 2~3 times that of the eastern part. This is the

  7. [Systemic sclerosis].

    Science.gov (United States)

    Schinke, Susanne; Riemekasten, Gabriela

    2016-04-01

    Systemic sclerosis is a challenging and heterogeneous disease due to the involvement of multiple organs and the high impact on morbidity and quality of life. Lung fibrosis, pulmonary arterial hypertension, and cardiac manifestations are main causes of systemic sclerosis-related deaths. In addition, patients suffer from a various range of co-morbidities such as malnutrition, depression, osteoporosis, malignancies, which are increased in these patients and have to be identified and treated. Early assessment of organ damage is a key to therapeutic success. The discovery of pathogenic autoantibodies combined with increased evidence of effective immunosuppressive and vasoactive treatment strategies are major developments in the therapy of the disease. At present, several clinical studies are ongoing and some of the biological therapies are promising.

  8. Blackboard Systems.

    Science.gov (United States)

    1986-06-01

    article stated that although the importance of context, syntax, semantics, and phonological rules in the recognition of speech was accepted, no system had...of, from the lowest to the highest level: parametric, segmental, phonetic , phonemic, syllabic, lexical, phrasal, and conceptual levels (see Figure 3...from classification (classifying acoustic segments into phonetic classes), to recognition (recognizing words) to generation and 42SCe (25] for a

  9. Security system

    Science.gov (United States)

    Baumann, Mark J.; Kuca, Michal; Aragon, Mona L.

    2016-02-02

    A security system includes a structure having a structural surface. The structure is sized to contain an asset therein and configured to provide a forceful breaching delay. The structure has an opening formed therein to permit predetermined access to the asset contained within the structure. The structure includes intrusion detection features within or associated with the structure that are activated in response to at least a partial breach of the structure.

  10. Imaging System

    Science.gov (United States)

    1995-01-01

    The 1100C Virtual Window is based on technology developed under NASA Small Business Innovation (SBIR) contracts to Ames Research Center. For example, under one contract Dimension Technologies, Inc. developed a large autostereoscopic display for scientific visualization applications. The Virtual Window employs an innovative illumination system to deliver the depth and color of true 3D imaging. Its applications include surgery and Magnetic Resonance Imaging scans, viewing for teleoperated robots, training, and in aviation cockpit displays.

  11. Propulsion Systems

    Science.gov (United States)

    2011-03-31

    definition we are choosing x to be aligned with the direction of flight. Thus, accounting for the possible rotation of the axes, the acceleration in...Monopropellants. In a monopropellant system, like the name suggests, there is one propellant which decomposes exothermically as it passes through a catalytic...it comes into contact with the catalyst bed. Subsequently, the ammonia decomposes into nitrogen and hydrogen in an endothermic reaction lowering the

  12. 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.

    /Poseidon) information. Vertical sections of temperature from two contrasting seasons - south-west (SW) and north-east (NE) monsoons - when projected together are found to intersect offshore at 350-400 km from the coast along a transect in the eastern Arabian Sea during...

  13. Surface circulation off Somalia and western equatorial Indian Ocean during summer monsoon of 1988 from Geosat altimeter data

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, B.; RameshBabu, V.; Murty, V.S.N.; Rao, L.V.G.

    -clockwise rotation. During August, the prime eddy or the Great Whirl centred at 9.5 degrees N, 53.5 degrees E off northern Somalia and the southern gyre centred at 3 degrees N, 51.5 degrees E off southern Somalia, both are clearly identified with clockwise rotation...

  14. A reduced-dynamics variational approach for the assimilation of altimeter data into eddy-resolving ocean models

    Science.gov (United States)

    Yu, Peng; Morey, Steven L.; O'Brien, James J.

    A new method of assimilating sea surface height (SSH) data into ocean models is introduced and tested. Many features observable by satellite altimetry are approximated by the first baroclinic mode over much of the ocean, especially in the lower (but non-equatorial) and mid latitude regions. Based on this dynamical trait, a reduced-dynamics adjoint technique is developed and implemented with a three-dimensional model using vertical normal mode decomposition. To reduce the complexity of the variational data assimilation problem, the adjoint equations are based on a one-active-layer reduced-gravity model, which approximates the first baroclinic mode, as opposed to the full three-dimensional model equations. The reduced dimensionality of the adjoint model leads to lower computational cost than a traditional variational data assimilation algorithm. The technique is applicable to regions of the ocean where the SSH variability is dominated by the first baroclinic mode. The adjustment of the first baroclinic mode model fields dynamically transfers the SSH information to the deep ocean layers. The technique is developed in a modular fashion that can be readily implemented with many three-dimensional ocean models. For this study, the method is tested with the Navy Coastal Ocean Model (NCOM) configured to simulate the Gulf of Mexico.

  15. Global Geometric Properties of Martian Impact Craters: An Assessment from Mars Orbiter Laser Altimeter (MOLA) Digital Elevation Models

    Science.gov (United States)

    Garvin, J. B.; Frawley, J. J.; Sakimoto, S. E. H.; Schnetzler, C.

    2000-01-01

    Global geometric characteristics of topographically fresh impact craters have been assessed, for the first time, from gridded MOLA topography. Global trends of properties such as depth/diameter differ from previous estimates. Regional differences are observed.

  16. Seasonal and inter-annual sea surface height variations of the northern Indian Ocean from the TOPEX/POSEIDON altimeter

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Snaith, H.; Challenor, P.; Guymer, H.T.

    variations reflect the dominant seasonal signal such as the coastal currents, the upwelling zones along Somalia, Arabia and west coast of India, the Great Whirl and Southern Gyre, and eddies in the Bay of Bengal. Temporal evolution of the coastal circulation...

  17. Signatures of Kelvin and Rossby wave propagation in the northern Indian Ocean from TOPEX/POSEIDON Altimeter

    Digital Repository Service at National Institute of Oceanography (India)

    PrasannaKumar, S.; Unnikrishnan, A.S.; Muraleedharan, P.M.

    are comparable to the theoretical phase speeds of Rossby waves. Time-longitude plots of zonal wind stress, obtained from the FSU wind stress climatology for the same period as that of T/P data, shows that the eastward propagation in the sea level field...

  18. Multi-scale wavelet analysis of TOPEX/Poseidon altimeter significant wave height in eastern China seas

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The multi-scale characteristics of wave significant height (Hs) in eastern China seas were revealed by multi-scale wavelet analysis. In order to understand the relation between wave and wind, the TOPEX/Poseidon measurements of Hs and wind speed were analyzed. The result showed that Hs and wind speed change in multi-scale at one-, two-month, half-, one- and two-year cycles. But in a larger time scale, the variations in Hs and wind speed are different. Hs has a five-year cycle similar to the cycle of ENSO variation, while the wind speed has no such cycle. In the time domain, the correlation between Hs and ENSO is unclear.

  19. 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.

  20. Estimating discharge from the Godavari river using ENVISAT, Jason-2, and SARAL/AltiKa radar altimeters

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, T.; Sharma, Rashmi; Mehra, P.; Prasad, K.V.S.R.

    range from 0.15 to 0.40 m, quite within the acceptable accuracy of altimetry for hydrology/river applications. The root mean square error (RMSE) between ENVISAT and in situ discharge is 366 and 253 m3 s-1 at Yanam and Bhadrachalam...

  1. LIDAR ALTIMETER MEASUREMENTS OF CANOPY STRUCTURE: METHODS AND VALIDATION FOR CLOSED-CANOPY BROADLEAF FOREST. (R828309)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  2. South Pole-Aitken Basin: Evidence for Post-Basin Resurfacing from Lunar Orbiter Laser Altimeter (LOLA) Data

    Science.gov (United States)

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

    2010-12-01

    The lunar farside South Pole-Aitken Basin is the largest and oldest documented basin on the Moon and is thus of interest from the point of view of the scale of production of impact melt at large basin-event sizes and its ring structure and potential depth of sampling at such a large diameter. We used new LOLA data from the Lunar Reconnaissance Orbiter 1) to characterize the basin interior topography, 2) to assess the nature of the nearby and relatively pristine Orientale basin and compare it to the SPA interior, and 3) to compile a new global crater database of all lunar craters ≥20 km in diameter and to assess the population of impact craters superposed on the SPA interior and exterior. We find that impact crater size-frequency distribution plots show that the exterior of the SPA basin is similar to the most heavily cratered regions of the Moon, but that the interior of the basin has a deficiency of craters in the 20-64 km diameter crater range. One interpretation of these data is that some resurfacing process (or processes) has modified the superposed crater population. Among the candidates are 1) impact crater proximity weathering/degradation by adjacent (e.g., Apollo) and nearby (e.g., Orientale) impact basin ejecta, 2) volcanic resurfacing by early non-mare volcanism, cryptomaria and/or maria, and 3) viscous relaxation removing crater topography. We consider viscous relaxation of crater topography to be the least likely due to the wavelength dependence of the process (rim-crests should be preserved and thus detected in our crater counts). Careful analysis of the impact ejecta thickness radial decay suggests that it is an important resurfacing mechanism within a basin radius from the rim crest, but is unlikely to be sufficient to explain the observed deficiency. Morphometric analysis of impact craters, modeling, and simulations of volcanic flooding suggest that the deficiency may be related to the patchy distribution of cryptomaria, suspected from mineralogic remote sensing data to be present in parts of the SPA floor. Combined altimetry and mineralogy data suggest that these volcanic deposits are patchy in their distribution, and do not preclude the mafic melt sheet deposit making up a significant part of the exposed SPA basin floor.

  3. Altimeter-derived flow field over a newly identified coastal ocean boundary in the eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

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

    circulation. However, the flow is meridional within the new boundary and nearly zonal outside. The offshore limit of the meridional flow coincides with the offshore limit of the coastal boundary. As expected, the meridional flow is poleward during November...

  4. Law system and legislation system

    OpenAIRE

    Boshno, Svetlana

    2013-01-01

    This paper is a continuation of publication of the «Jurisprudence» textbook by Svetlana Vladimirovna Boshno. Law system is a key element of general theory of law. The major fundamentals of its construction are subject matter and method of legal regulation. Of great importance is the division of legal regulation methods into mandative and dispositive ones. The paper articulates the concepts of institute and branch of law demonstrated through various examples. An important classification of bra...

  5. Linear systems

    CERN Document Server

    Bourlès, Henri

    2013-01-01

    Linear systems have all the necessary elements (modeling, identification, analysis and control), from an educational point of view, to help us understand the discipline of automation and apply it efficiently. This book is progressive and organized in such a way that different levels of readership are possible. It is addressed both to beginners and those with a good understanding of automation wishing to enhance their knowledge on the subject. The theory is rigorously developed and illustrated by numerous examples which can be reproduced with the help of appropriate computation software. 60 exe

  6. Nuclear systems

    CERN Document Server

    Todreas, Neil E

    2011-01-01

    Principal Characteristics of Power ReactorsIntroductionPower CyclesPrimary Coolant SystemsReactor CoresFuel AssembliesAdvanced Water- and Gas-Cooled Reactors (Generation III And III+)Advanced Thermal and Fast Neutron Spectrum Reactors (Generation IV)ReferencesProblemsThermal Design Principles and ApplicationIntroductionOverall Plant Characteristics Influenced by Thermal Hydraulic ConsiderationsEnergy Production and Transfer ParametersThermal Design LimitsThermal Design MarginFigures of Merit for Core Thermal PerformanceThe Inverted Fuel ArrayThe Equivalent Annulus ApproximationReferencesProble

  7. Expert Systems: What Is an Expert System?

    Science.gov (United States)

    Duval, Beverly K.; Main, Linda

    1994-01-01

    Describes expert systems and discusses their use in libraries. Highlights include parts of an expert system; expert system shells; an example of how to build an expert system; a bibliography of 34 sources of information on expert systems in libraries; and a list of 10 expert system shells used in libraries. (Contains five references.) (LRW)

  8. Systemic Planning

    DEFF Research Database (Denmark)

    Leleur, Steen

    This book presents principles and methodology for planning in a complex world. It sets out a so-called systemic approach to planning, among other things, by applying “hard” and “soft” methodologies and methods in combination. The book is written for Ph.D and graduate students in engineering......, business and other fields, and it is useful for all professionals, across a wide range of employment areas, who share an interest in renewing planning practice. Such an endeavour is seen as both important and timely, recognising that many complex planning tasks necessitate organisations – be they public...... or private – to engage in planning to prepare proactive decision-making....

  9. Model Systems

    Directory of Open Access Journals (Sweden)

    Francisco Rodríguez-Trelles

    1998-12-01

    Full Text Available Current efforts to study the biological effects of global change have focused on ecological responses, particularly shifts in species ranges. Mostly ignored are microevolutionary changes. Genetic changes may be at least as important as ecological ones in determining species' responses. In addition, such changes may be a sensitive indicator of global changes that will provide different information than that provided by range shifts. We discuss potential candidate systems to use in such monitoring programs. Studies of Drosophila subobscura suggest that its chromosomal inversion polymorphisms are responding to global warming. Drosophila inversion polymorphisms can be useful indicators of the effects of climate change on populations and ecosystems. Other species also hold the potential to become important indicators of global change. Such studies might significantly influence ecosystem conservation policies and research priorities.

  10. Turbocompound system

    Energy Technology Data Exchange (ETDEWEB)

    Fox, L.D.

    1986-05-06

    A turbocompound system is described for improving the performance of an internal combustion engine without substantially increasing an end viewed profile of the engine to which it is mounted in use. The system consists of: (a) an exhaust driven turbocharger means having an exhaust manifold means extending in an axial direction for collecting exhaust gases from engine cylinders and delivering the gases to an outlet end thereof, exhaust turbine means for extracting energy from the exhaust gases, the exhaust turbine means being provided with an inlet connected to the outlet end of the manifold and an outlet for discharging the exhaust gases, compressor means coupled to the exhaust turbine means for providing a supply of charge air under pressure to an air outlet thereof for delivery to air intake means of an internal combustion engine in use; (b) a power turbine means for extracting additional energy from the exhaust gases, the power turbine means having an intake connected to the outlet of the exhaust turbine means, and mounting means on a side of the power turbine means facing in a direction parallel to the axial direction of the exhaust manifold means that is constructed for being mounted, in use, on an end of an engine adjacent one end of a crankshaft of the engine; and (c) coupling means connected to the power turbine means for transferring mechanical energy produced by the power turbine means, the coupling means extending from the power turbine means to a power take-off end in a direction parallel to the axial length of the exhaust manifold means by an amount that is sufficient for enabling the power take-off end to be connected, in use, to an opposite end of the engine crankshaft from the one end thereof in a manner for transferring the mechanical energy produced by the power turbine means adjacent the one end of the crankshaft to the opposite end of the crankshaft without having to pass therethrough.

  11. Systems engineering simplified

    CERN Document Server

    Cloutier, Robert; Bone, Mary Alice

    2015-01-01

    IntroductionOverviewDiscussion of Common TerminologyThe Case for Systems EngineeringA Brief History of Systems EngineeringSystem ExamplesSummaryThe System Life CycleManaging System Development-The Vee ModelSystem ProductionSystem Utilization and SupportSystem Retirement and DisposalOther Systems Engineering Development ModelsSpiral ModelAgile Model for Systems EngineeringSystem of InterestAbstraction and DecompositionIntegrationDeveloping and Managing RequirementsCyclone Requiremen

  12. Cardiovascular System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    7.1 Heart failure2007175 Effects of recombinant human brain natriuretic peptide on aldosterone and endothelin-1 in treatment of heart failure. FU Yao(付尧),et al. Dept Cardiol, 1st Affili Hosp, China Med Univ, Shenyang 110001. Chin Cir J 2007;22(1):35-37. Obiective To study the efficacy and the effects of recombinant human brain natriuretic peptide(rhBNP) on aldosterone and endothelin-1 in the treatment of congestive heart failure(CHF).Methods A randomized, open, controlled clinical trial was conducted in 35 patients with CHF. Eighteen received rhBNP and 17 were treated with nitroglycerin as controls. The changes hemodynamic indexes, the plasma concentrations of K+, Na+, aldo-sterone(ALD) and endothelin-1 (ET-1) in order to examine the efficacy and mechanism of rhBNP. Results Between experiment and control groups significant differences were found in the decreasing of PCWP, PAP and plasma concentration of Na+, ALD, ET-1, and in the increasing of plasma concentration of K+ (P<0.05~0.01). Conclusion The mechanism of rhBNP may be associated with the overactivation of renin-angiotension-aldosterone system, and the inhibited production of endothelin-1.

  13. System safety education focused on system management

    Science.gov (United States)

    Grose, V. L.

    1971-01-01

    System safety is defined and characteristics of the system are outlined. Some of the principle characteristics include role of humans in hazard analysis, clear language for input and output, system interdependence, self containment, and parallel analysis of elements.

  14. Respiratory System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    8.1 Respiratory failure2007204 Comparison of the effects of BiPAP ventilation combined with lung recruitment maneuvers and low tidal volume A/C ventilation in patients with acute respiratory distress syndrome. WANG Xiaozhi(王晓芝),et al. Dept Respir & Intensive Care Unit, Binzhou Med Coll, Binzhou 256603. Chin J Tuberc Respir Dis 2007;30(1):44-47. Objective To compare the effects of BiPAP ventilation combined with lung recruitment maneuvers(LRM) with low tidal volume A/C ventilation in patients with acute respiratory distress syndrome (ARDS). Methods A prospective, randomized comparison of BiPAP mechanical ventilation combined with lung recruitment maneuvers(test group) with low tidal volume A/C ventilation (control group) was conducted in 28 patients with ARDS. FiO2/PaO2 ratio, respiratory system compliance(Cs), central venous pressure (CVP), duration of ventilation support were recorded at 0 h, 48 h and 72 h separately. The ventilation associated lung injury and mortality at 28 d were also recorded. Results The FiO2/PaO2 ratio were (298±16) and (309±16) cm H2O, Cs were (38.4±2.2) and (42.0±1.3) ml/cm H2O, CVP were (13.8±0.8) and (11.6±0.7) cm H2O in the test group at 48 h and 72 h separately. In the control group, FiO2/PaO2 ratio were (212±12) and (246±17) cm H2O, Cs were (29.5±1.3) and (29.0±1.0) ml/cm H2O, CVP were 18.6±1.1 and (16.8±1.0) cm H2O. The results were better in the test group as compared with the control group (t=10.03-29. 68, all P<0.01). The duration of ventilation support in the test group was shorter than the control group [(14±3) d vs (19±3)d, t=4.80, P<0.01]. The mortality in 28 d and ventilation associated lung injury were similar in the two groups. Conclusion The results show that combination of LRM with BiPAP mode ventilation, as compared with the control group, contributes to the improved FiO2/PaO2 ratio, pulmonary compliance, stable homodynamic and shorter duration of ventilation support in patients with ARDs.

  15. An Integrated, Evidence-Based Approach to Transitioning to Operations: Specifications for Future Replacement Lights on ISS

    Science.gov (United States)

    Leveton, Lauren; Brainard, George; Whitmire, Alexandra; Kubey, Alan; Maida, Jim; Bowen, Charles; Johnston, Smith

    2010-01-01

    The International Space Station (ISS) currently uses General Luminaire Assemblies (GLAs) as its primary light source. These GLAs are composed of fluorescent lighting and are integrated into the electrical system on Station. Seventy seven of these units are distributed throughout the vehicle, and many of the lights, having reached their lifespan, are no longer functional; while backup panels are available on orbit, it is anticipated that the supplies of fluorescents on the station will be exhausted by 2015. The ISS vehicle office is therefore preparing to replace all of the GLAs, with Solid State Light Assemblies (SSLAs) composed of white Light Emitting Diodes (LEDs). In the Spring of 2010, an announcement for the replacement lights was released. The announcement specified that proposed lighting systems should use LED technology, given certain power draw restrictions and no changes to how the lights are currently controlled (a central on/off switch per node, and a dial to turn on/off and increase brightness on each lighting unit). The replacement lights are to follow current specifications for brightness levels (lux) and color temperature (degrees Kelvin, or K). Reportedly, the lighting on orbit is dim and suboptimal. The average brightness of the lights (given all lights within a node are operational) is 291 lux; by comparison, recommended office lighting ranges from 200 to 500 lux, and daylight ranges on a typical overcast day, consists of 10,000 to 25,000 lux. Representatives from NASA Behavioral Health and Performance Element (BHP) and Human Factors and Habitability identified that maintaining current brightness levels limits visual acuity, work space, and the use of light as a countermeasure for improving circadian entrainment, hastening phase shifting, evoking acute alertness and enhancing performance. Revised lighting specifications are therefore needed to optimize the replacement lights for the ISS.

  16. Quality management system

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Mu Sung

    2009-08-15

    This book deals with ISO9001 quality management system which includes summary of this system such as classification of quality, principle of quality management, and definition, requirement and procedure of quality management system, introduction of ISO9001 system like model of ISO9001 quality management system, ISO certificate system, structure of ISO9001 standard, requirement of ISO9001 quality management system, process approach and documentation of system, propel cases of ISO9001 quality management system.

  17. 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.

  18. Square conservation systems and Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    王斌; 曾庆存; 季仲贞

    1995-01-01

    The internal and external relationships between the square conservation scheme and the symplectic scheme are revealed by a careful study on the interrelation between the square conservation system and the Hamiltonian system in the linear situation, thus laying a theoretical basis for the application and extension of symplectic schemes to square conservations systems, and of those schemes with quadratic conservation properties to Hamiltonian systems.

  19. Systems theory of interconnected port contact systems

    NARCIS (Netherlands)

    Eberard, D.; Maschke, B.M.; Schaft, A.J. van der

    2005-01-01

    Port-based network modeling of a large class of complex physical systems leads to dynamical systems known as port-Hamiltonian systems. The key ingredient of any port-Hamiltonian system is a power-conserving interconnection structure (mathematically formalized by the geometric notion of a Dirac struc

  20. Protecting Information in Systems of Systems

    NARCIS (Netherlands)

    Trivellato, Daniel; Zannone, Nicola; Etalle, Sandro

    2011-01-01

    Systems of Systems (SoS) are dynamic, distributed coalitions of autonomous and heterogeneous systems that collaborate to achieve a common goal. While offering several advantages in terms of scalability and flexibility, the SoS paradigm has a strong impact on system interoperability and on the securi

  1. Understanding Patterns for System of Systems Integration

    DEFF Research Database (Denmark)

    Kazman, Rick; Schmid, Klaus; Nielsen, Claus Ballegård

    2013-01-01

    of systems integration patterns. These characteristics at the same time support the architecting process by highlighting important issues a SoS architect needs to consider. We discuss the consolidated template and illustrate it with an example pattern. We also discuss the integration of this novel pattern......Architecting systems of systems is well known to be a formidable challenge. A major aspect in this is defining the integration among the systems that constitute the system of systems. In this paper, we aim to support the SoS architect by systematically developing a way to characterize system...

  2. Concept and System of Personification Control System

    Institute of Scientific and Technical Information of China (English)

    Bai,Fengshuang; Yin,Yixin; Tu,Xuyan; Zhang,Ying

    2006-01-01

    This paper provides the system and conception of the Personification Control System (PCS) on the basis of Intelligent Control System based on Artificial life (ICS/AL), Artificial Emotion, Humanoid Control, and Intelligent Control System based on Field bus. According to system science and deciding of organize of biology, the Pyramid System of PCS are created. Then Pyramid System of PCS which is made up of PCS1/H, PCS1/S, PCS1/O, PCS1/C and PCS1/G is described.

  3. Networked control of microgrid system of systems

    Science.gov (United States)

    Mahmoud, Magdi S.; Rahman, Mohamed Saif Ur; AL-Sunni, Fouad M.

    2016-08-01

    The microgrid has made its mark in distributed generation and has attracted widespread research. However, microgrid is a complex system which needs to be viewed from an intelligent system of systems perspective. In this paper, a network control system of systems is designed for the islanded microgrid system consisting of three distributed generation units as three subsystems supplying a load. The controller stabilises the microgrid system in the presence of communication infractions such as packet dropouts and delays. Simulation results are included to elucidate the effectiveness of the proposed control strategy.

  4. D0 Cryo System Control System Autodialer

    Energy Technology Data Exchange (ETDEWEB)

    Urbin, J.; /Fermilab

    1990-04-17

    The DO cryogenic system is controlled by a TI565-PLC based control system. This allows the system to be unmanned when in steady state operation. System experts will need to be contacted when system parameters exceed normal operating points and reach alarm setpoints. The labwide FIRUS system provides one alarm monitor and communication link. An autodialer provides a second and more flexible alarm monitor and communication link. The autodialer monitors contact points in the control system and after receiving indication of an alarm accesses a list of experts which it calls until it receives an acknowledgement. There are several manufacturers and distributors of autodialer systems. This EN explains the search process the DO cryo group used to fmd an autodialer system that fit the cryo system's needs and includes information and specs for the unit we chose.

  5. CRUCIAL: Cryosat-2 Success over Inland Water and Land

    DEFF Research Database (Denmark)

    Moore, Philip; Berry, Philippa; Balmbra, Robert;

    2014-01-01

    of inland water, salar and ice surfaces has enabled Earth-orbiting satellite radar altimeters to be used for land surface applications including mapping and measurement of river and lake systems. Research with EnviSat Burst Echoes has shown that substantial high frequency information content is present...... at short spatial scales with a small bright reflecting patch at nadir, such as over inland water, able to dominate the returned echo. Onboard echo averaging of the previous generation of satellite radar altimeters therefore causes loss of significant amounts of information. The high along-track sampling...

  6. Freshwater systems; Frisch gezapft

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, J.P.

    2008-06-09

    Increasingly, providers of solar systems are also offering freshwater systems, although these are more costly than combined storage systems. The contribution discusses the pros and cons of these systems as well as the freshwater quality. (orig.)

  7. Integrated library systems.

    Science.gov (United States)

    Goldstein, C M

    1983-07-01

    The development of integrated library systems is discussed. The four major discussion points are (1) initial efforts; (2) network resources; (3) minicomputer-based systems; and (4) beyond library automation. Four existing systems are cited as examples of current systems.

  8. System design specification Brayton Isotope Power System (BIPS) Flight System (FS), and Ground Demonstration System (GDS)

    Energy Technology Data Exchange (ETDEWEB)

    1976-06-14

    The system design specification for ground demonstration, development, and flight qualification of a Brayton Isotope Power System (BIPS) is presented. The requirements for both a BIPS conceptual Flight System (FS) and a Ground Demonstration System (GDS) are defined.

  9. Commercial-Off-The-Shelf Microelectromechanical Systems (MEMS) Flow-Measurement Probes Fabricated And Assembled

    Science.gov (United States)

    Redding, Chip

    2002-01-01

    As an alternative to conventional tubing instrumentation for measuring airflow, designers and technicians at the NASA Glenn Research Center have been fabricating packaging components and assembling a set of unique probes using commercial-off-the-shelf microelectromechanical systems (MEMS) integrated circuits (computer chips). Using MEMS as an alternative has some compelling advantages over standard measurement devices. Sensor technologies have matured through high-production usage in industries such as automotive and aircraft manufacturers. Currently, MEMS are the choice in applications such as tire pressure monitors, altimeters, pneumatic controls, cable leak detectors, and consumer appliances. Conventional instrumentation uses tubing buried in the model aerodynamic surfaces or wind tunnel walls. The measurements are made when pressure is introduced at the tube opening. The pressure then must travel the tubing for lengths ranging from 20 to hundreds of feet before reaching an electronic signal conditioner. This condition causes a considerable amount of damping and requires measurements to be made only after the test rig has reached steady-state operation. The electronic MEMS pressure sensor is able to take readings continuously under dynamic states in nearly real time. The use of stainless steel tubing for pressure measurements requires many tubes to be cleaned, cut to length, carefully installed, and delicately deburred and spliced for use. A cluster of a few hundred 1/16-in.- (0.0625-in.-) diameter tubes (not uncommon in research testing facilities) can be several inches in diameter and may weigh enough to require two men to handle. Replacing hard tubing with electronic chips can eliminate much of the bulk. Each sensor would fit on the tip of the 1/16-in. tubing with room to spare. The P592 piezoresistive silicon pressure sensor (Lucas NovaSensor, Fremont, CA) was chosen for this project because of its cost, availability, and tolerance to extreme ambient

  10. Situation awareness with systems of systems

    CERN Document Server

    Tretmans, Jan; Borth, Michael

    2013-01-01

    This book discusses various aspects, challenges, and solutions for developing systems-of-systems for situation awareness, using applications in the domain of maritime safety and security.  Topics include advanced, multi-objective visualization methods for situation awareness, stochastic outlier selection, rule-based anomaly detection, an ontology-based event model for semantic reasoning, new methods for semi-automatic generation of adapters bridging communication gaps, security policies for systems-of-systems, trust assessment, and methods to deal with the dynamics of systems-of-systems in run-time monitoring, testing, and diagnosis. Architectural considerations for designing information-centric systems-of-systems such as situation awareness systems, and an integrated demonstrator implementing many of the investigated aspects, complete the book.

  11. Computer System Design System-on-Chip

    CERN Document Server

    Flynn, Michael J

    2011-01-01

    The next generation of computer system designers will be less concerned about details of processors and memories, and more concerned about the elements of a system tailored to particular applications. These designers will have a fundamental knowledge of processors and other elements in the system, but the success of their design will depend on the skills in making system-level tradeoffs that optimize the cost, performance and other attributes to meet application requirements. This book provides a new treatment of computer system design, particularly for System-on-Chip (SOC), which addresses th

  12. Smart electromechanical systems the central nervous system

    CERN Document Server

    Kurbanov, Vugar

    2017-01-01

    This book describes approaches to solving the problems of developing the central nervous system of robots (CNSR) based on smart electromechanical systems (SEMS) modules, principles of construction of the various modules of the central nervous system and variants of mathematical software CNSR in control systems for intelligent robots. It presents the latest advances in theory and practice at the Russian Academy of Sciences. Developers of intelligent robots to solve modern problems in robotics are increasingly addressing the use of the bionic approach to create robots that mimic the complexity and adaptability of biological systems. These have smart electromechanical system (SEMS), which are used in various cyber-physical systems (CPhS), and allow the functions of calculation, control, communications, information storage, monitoring, measurement and control of parameters and environmental parameters to be integrated. The behavior of such systems is based on the information received from the central nervous syst...

  13. Linking Political Systems and War Systems

    DEFF Research Database (Denmark)

    Harste, Gorm

    2009-01-01

    Decisive parts of the Western political system have demonstrated a seemingly surprising misinterpretation of military might. As Madelaine Albright has suggested, the mighty perceived themselves as "almighty". Political power seems to have invested in instrumental coercive power relations and found...... military coercion to be the appropriate mean. Using the system theory and the theory of systemic risks displayed by the German sociologist Niklas Luhmann the article demonstrates how military systems due to their own autonomy and autopoiesis do not fit into the idea of political government....... The Clausewitzian ideal of a political system that could continue its power games by means of war was moderated by Clausewitz' own analysis of "friction". How can a political system be so blind towards the possibilities of another system? What are the risks of systemic blind spots? The argument of the paper...

  14. Designing information systems

    CERN Document Server

    Blethyn, Stanley G

    2014-01-01

    Designing Information Systems focuses on the processes, methodologies, and approaches involved in designing information systems. The book first describes systems, management and control, and how to design information systems. Discussions focus on documents produced from the functional construction function, users, operators, analysts, programmers and others, process management and control, levels of management, open systems, design of management information systems, and business system description, partitioning, and leveling. The text then takes a look at functional specification and functiona

  15. LCLS XTOD Attenuator System System Concept Report

    Energy Technology Data Exchange (ETDEWEB)

    Kishiyama, K; Roeben, M; Trent, J; Ryutov, D; Shen, S

    2006-04-12

    The attenuator system for the Linac Coherent Light Source (LCLS) X-ray Transport, Optics and Diagnostics (XTOD) system has been configured and analyzed by the Lawrence Livermore National Laboratory's New Technologies Engineering Division (NTED) as requested by the SLAC/LCLS program. The system layout, performance analyses and selection of the vacuum components are presented in this System Conceptual Review (SCR) report. Also included are the plans for prototype, procurement, mechanical integration, and the cost estimates.

  16. Engine Auxiliary System Guideline: Lubricating Oil Systems

    OpenAIRE

    Linna, Joni

    2015-01-01

    This thesis was done for Wärtsilä Technical Services organization, the purpose of this work was to gather and structure information about the lubricating oil systems from the company’s internal databases, interviews with system specialists and from different literature sources covering Ship Power and Power Plant products. The outcome was a guideline, covering typical power plant and marine system descriptions, all components used in the lubricating oil system with their functional description...

  17. COMPARISON TRADITIONAL SYSTEMS OF TUNNEL FORMWORK SYSTEM

    OpenAIRE

    ERKAN, İbrahim Hakkı; Yılmaz, Ülkü Sultan; Türken, Hakan

    2011-01-01

    Tunnel formwork systems became the most widespread construction technology preferred in recent years in Turkey due to rapidity and economy. In this study, before all else, a brief information was given about the types and construction techniques of tunnel formwork systems. Then a reinforced concrete building sample was firstly modeled as it was constructed with the tunnel formwork system and secondly modeled as it was formed by a frame system with shear walls constructed by the traditional re...

  18. Modeling learning technology systems as business systems

    NARCIS (Netherlands)

    Avgeriou, Paris; Retalis, Symeon; Papaspyrou, Nikolaos

    2003-01-01

    The design of Learning Technology Systems, and the Software Systems that support them, is largely conducted on an intuitive, ad hoc basis, thus resulting in inefficient systems that defectively support the learning process. There is now justifiable, increasing effort in formalizing the engineering o

  19. The complement system in systemic autoimmune disease

    NARCIS (Netherlands)

    Chen, Min; Daha, Mohamed R.; Kallenberg, Cees G. M.

    2010-01-01

    Complement is part of the innate immune system. Its major function is recognition and elimination of pathogens via direct killing and/or stimulation of phagocytosis. Activation of the complement system is, however, also involved in the pathogenesis of the systemic autoimmune diseases. Activation via

  20. General Systems Theory and Instructional Systems Design.

    Science.gov (United States)

    Salisbury, David F.

    1990-01-01

    Describes basic concepts in the field of general systems theory (GST) and identifies commonalities that exist between GST and instructional systems design (ISD). Models and diagrams that depict system elements in ISD are presented, and two matrices that show how GST has been used in ISD literature are included. (11 references) (LRW)

  1. Optical system defect propagation in ABCD systems

    DEFF Research Database (Denmark)

    McKinley, W.G.; Yura, H.T.; Hanson, Steen Grüner

    1988-01-01

    We describe how optical system defects (tilt/jitter, decenter, and despace) propagate through an arbitrary paraxial optical system that can be described by an ABCD ray transfer matrix. A pedagogical example is given that demonstrates the effect of alignment errors on a typical optical system....... © 1988 Optical Society of America...

  2. Expert Systems for auditing management information systems

    Directory of Open Access Journals (Sweden)

    Gheroghe Popescu

    2007-05-01

    Full Text Available Expert systems are built with the help of: specialised programming languages or expert system generators (shell. But this structure was reached after tens of years of work and research, because expert systems are nothing but pragmatic capitalisation of the results of research carried out in artificial intelligence and theory of knowledge.

  3. Non linear system become linear system

    Directory of Open Access Journals (Sweden)

    Petre Bucur

    2007-01-01

    Full Text Available The present paper refers to the theory and the practice of the systems regarding non-linear systems and their applications. We aimed the integration of these systems to elaborate their response as well as to highlight some outstanding features.

  4. Operating System Security

    CERN Document Server

    Jaeger, Trent

    2008-01-01

    Operating systems provide the fundamental mechanisms for securing computer processing. Since the 1960s, operating systems designers have explored how to build "secure" operating systems - operating systems whose mechanisms protect the system against a motivated adversary. Recently, the importance of ensuring such security has become a mainstream issue for all operating systems. In this book, we examine past research that outlines the requirements for a secure operating system and research that implements example systems that aim for such requirements. For system designs that aimed to

  5. Psychology of system design

    CERN Document Server

    Meister, D

    2014-01-01

    This is a book about systems, including: systems in which humans control machines; systems in which humans interact with humans and the machine component is relatively unimportant; systems which are heavily computerized and those that are not; and governmental, industrial, military and social systems. The book deals with both traditional systems like farming, fishing and the military, and with systems just now tentatively emerging, like the expert and the interactive computer system. The emphasis is on the system concept and its implications for analysis, design and evaluation of these many di

  6. Biomedical signals and systems

    CERN Document Server

    Tranquillo, Joseph V

    2013-01-01

    Biomedical Signals and Systems is meant to accompany a one-semester undergraduate signals and systems course. It may also serve as a quick-start for graduate students or faculty interested in how signals and systems techniques can be applied to living systems. The biological nature of the examples allows for systems thinking to be applied to electrical, mechanical, fluid, chemical, thermal and even optical systems. Each chapter focuses on a topic from classic signals and systems theory: System block diagrams, mathematical models, transforms, stability, feedback, system response, control, time

  7. Autonomous photovoltaic lighting system

    OpenAIRE

    Ahmed A. A. Hafez; Montesinos Miracle, Daniel; Sudrià Andreu, Antoni

    2012-01-01

    This paper introduces a comparison between the conventional and Photovoltaic (PV) lighting systems. A simple sizing procedure for a PV stand-alone system was advised. The paper also proposes a novel PV lighting system. The proposed system is simple, compact and reliable. The system operation was investigated by thoroughly mathematical and simulation work.

  8. Lighting system with thermal management system

    Energy Technology Data Exchange (ETDEWEB)

    Arik, Mehmet; Weaver, Stanton Earl; Stecher, Thomas Elliot; Seeley, Charles Erklin; Kuenzler, Glenn Howard; Wolfe, Jr, Charles Franklin; Utturkar, Yogen Vishwas; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

    2016-10-11

    Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

  9. Lighting system with thermal management system

    Science.gov (United States)

    Arik, Mehmet; Weaver, Stanton; Stecher, Thomas; Seeley, Charles; Kuenzler, Glenn; Wolfe, Jr., Charles; Utturkar, Yogen; Sharma, Rajdeep; Prabhakaran, Satish; Icoz, Tunc

    2013-05-07

    Lighting systems having unique configurations are provided. For instance, the lighting system may include a light source, a thermal management system and driver electronics, each contained within a housing structure. The light source is configured to provide illumination visible through an opening in the housing structure. The thermal management system is configured to provide an air flow, such as a unidirectional air flow, through the housing structure in order to cool the light source. The driver electronics are configured to provide power to each of the light source and the thermal management system.

  10. Systems Measures of Water Distribution System Resilience

    Energy Technology Data Exchange (ETDEWEB)

    Klise, Katherine A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Murray, Regan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Walker, La Tonya Nicole [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Resilience is a concept that is being used increasingly to refer to the capacity of infrastructure systems to be prepared for and able to respond effectively and rapidly to hazardous events. In Section 2 of this report, drinking water hazards, resilience literature, and available resilience tools are presented. Broader definitions, attributes and methods for measuring resilience are presented in Section 3. In Section 4, quantitative systems performance measures for water distribution systems are presented. Finally, in Section 5, the performance measures and their relevance to measuring the resilience of water systems to hazards is discussed along with needed improvements to water distribution system modeling tools.

  11. Operating System Performance Analyzer for Embedded Systems

    Directory of Open Access Journals (Sweden)

    Shahzada Khayyam Nisar

    2011-11-01

    Full Text Available RTOS provides a number of services to an embedded system designs such as case management, memory management, and Resource Management to build a program. Choosing the best OS for an embedded system is based on the available OS for system designers and their previous knowledge and experience. This can cause an imbalance between the OS and embedded systems. RTOS performance analysis is critical in the design and integration of embedded software to ensure that limits the application meet at runtime. To select an appropriate operating system for an embedded system for a particular application, the OS services to be analyzed. These OS services are identified by parameters to establish performance metrics. Performance Metrics selected include context switching, Preemption time and interrupt latency. Performance Metrics are analyzed to choose the right OS for an embedded system for a particular application.

  12. Mapping biological systems to network systems

    CERN Document Server

    Rathore, Heena

    2016-01-01

    The book presents the challenges inherent in the paradigm shift of network systems from static to highly dynamic distributed systems – it proposes solutions that the symbiotic nature of biological systems can provide into altering networking systems to adapt to these changes. The author discuss how biological systems – which have the inherent capabilities of evolving, self-organizing, self-repairing and flourishing with time – are inspiring researchers to take opportunities from the biology domain and map them with the problems faced in network domain. The book revolves around the central idea of bio-inspired systems -- it begins by exploring why biology and computer network research are such a natural match. This is followed by presenting a broad overview of biologically inspired research in network systems -- it is classified by the biological field that inspired each topic and by the area of networking in which that topic lies. Each case elucidates how biological concepts have been most successfully ...

  13. Systems Architecture for a Nationwide Healthcare System.

    Science.gov (United States)

    Abin, Jorge; Nemeth, Horacio; Friedmann, Ignacio

    2015-01-01

    From a national level to give Internet technology support, the Nationwide Integrated Healthcare System in Uruguay requires a model of Information Systems Architecture. This system has multiple healthcare providers (public and private), and a strong component of supplementary services. Thus, the data processing system should have an architecture that considers this fact, while integrating the central services provided by the Ministry of Public Health. The national electronic health record, as well as other related data processing systems, should be based on this architecture. The architecture model described here conceptualizes a federated framework of electronic health record systems, according to the IHE affinity model, HL7 standards, local standards on interoperability and security, as well as technical advice provided by AGESIC. It is the outcome of the research done by AGESIC and Systems Integration Laboratory (LINS) on the development and use of the e-Government Platform since 2008, as well as the research done by the team Salud.uy since 2013.

  14. Calo trigger acquisition system

    CERN Multimedia

    Franchini, Matteo

    2016-01-01

    Calo trigger acquisition system - Evolution of the acquisition system from a multiple boards system (upper, orange cables) to a single board one (below, light blue cables) where all the channels are collected in a single board.

  15. What Are Expert Systems?

    Science.gov (United States)

    d'Agapeyeff, A.

    1986-01-01

    Intended for potential business users, this paper describes the main characteristics of expert systems; discusses practical use considerations; presents a taxonomy of the systems; and reviews several expert system development projects in business and industry. (MBR)

  16. for hybrid dynamical systems

    Directory of Open Access Journals (Sweden)

    Wassim M. Haddad

    2001-01-01

    Full Text Available In this paper we develop a unified dynamical systems framework for a general class of systems possessing left-continuous flows; that is, left-continuous dynamical systems. These systems are shown to generalize virtually all existing notions of dynamical systems and include hybrid, impulsive, and switching dynamical systems as special cases. Furthermore, we generalize dissipativity, passivity, and nonexpansivity theory to left-continuous dynamical systems. Specifically, the classical concepts of system storage functions and supply rates are extended to left-continuous dynamical systems providing a generalized hybrid system energy interpretation in terms of stored energy, dissipated energy over the continuous-time dynamics, and dissipated energy over the resetting events. Finally, the generalized dissipativity notions are used to develop general stability criteria for feedback interconnections of left-continuous dynamical systems. These results generalize the positivity and small gain theorems to the case of left-continuous, hybrid, and impulsive dynamical systems.

  17. Manned systems technology discipline

    Science.gov (United States)

    Bretoi, Remus

    1990-01-01

    Viewgraphs on manned systems technology discipline for Space Station Freedom are presented. Topics covered include: crew-systems interfaces and interactions; crew training; on-board systems maintenance and support; habitability and environment; and computational human factors.

  18. Bridge Management Systems

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In this paper bridge management systems are discussed with special emphasis on management systems for reinforced concrete bridges. Management systems for prestressed concrete bridges, steel bridges, or composite bridges can be developed in a similar way....

  19. Autonomic Nervous System Disorders

    Science.gov (United States)

    Your autonomic nervous system is the part of your nervous system that controls involuntary actions, such as the beating of your heart ... breathing and swallowing Erectile dysfunction in men Autonomic nervous system disorders can occur alone or as the result ...

  20. Brain and Nervous System

    Science.gov (United States)

    ... Your 1- to 2-Year-Old Brain and Nervous System KidsHealth > For Parents > Brain and Nervous System Print ... brain is quite the juggler. Anatomy of the Nervous System If you think of the brain as a ...