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Sample records for ground-based gps tec

  1. Mapping the East African Ionosphere Using Ground-based GPS TEC Measurements

    Science.gov (United States)

    Mengist, Chalachew Kindie; Kim, Yong Ha; Yeshita, Baylie Damtie; Workayehu, Abyiot Bires

    2016-03-01

    The East African ionosphere (3°S-18°N, 32°E-50°E) was mapped using Total Electron Content (TEC) measurements from ground-based GPS receivers situated at Asmara, Mekelle, Bahir Dar, Robe, Arbaminch, and Nairobi. Assuming a thin shell ionosphere at 350 km altitude, we project the Ionospheric Pierce Point (IPP) of a slant TEC measurement with an elevation angle of >10° to its corresponding location on the map. We then infer the estimated values at any point of interest from the vertical TEC values at the projected locations by means of interpolation. The total number of projected IPPs is in the range of 24-66 at any one time. Since the distribution of the projected IPPs is irregularly spaced, we have used an inverse distance weighted interpolation method to obtain a spatial grid resolution of 1°×1° latitude and longitude, respectively. The TEC maps were generated for the year 2008, with a 2 hr temporal resolution. We note that TEC varies diurnally, with a peak in the late afternoon (at 1700 LT), due to the equatorial ionospheric anomaly. We have observed higher TEC values at low latitudes in both hemispheres compared to the magnetic equatorial region, capturing the ionospheric distribution of the equatorial anomaly. We have also confirmed the equatorial seasonal variation in the ionosphere, characterized by minimum TEC values during the solstices and maximum values during the equinoxes. We evaluate the reliability of the map, demonstrating a mean error (difference between the measured and interpolated values) range of 0.04-0.2 TECU (Total Electron Content Unit). As more measured TEC values become available in this region, the TEC map will be more reliable, thereby allowing us to study in detail the equatorial ionosphere of the African sector, where ionospheric measurements are currently very few.

  2. Observing Tsunamis in the Ionosphere Using Ground Based GPS Measurements

    Science.gov (United States)

    Galvan, D. A.; Komjathy, A.; Song, Y. Tony; Stephens, P.; Hickey, M. P.; Foster, J.

    2011-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following recent seismic events, including the Tohoku tsunami of March 11, 2011. We observe fluctuations correlated in time, space, and wave properties with this tsunami in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the Tohoku tsunami near the epicenter, at Hawaii, and near the west coast of North America. Disturbance magnitudes are 1-10% of the background TEC value. Observations near the epicenter are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement. The potential exists to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for future early warning systems.

  3. Seismo-traveling ionospheric disturbances of earthquake and tsunami waves observed by space- and ground-based GPS receivers

    Science.gov (United States)

    Liu, J. Y. G.; Chen, C. Y.; Lin, C. H.

    2015-12-01

    FORMOSAT-3/COSMIC (F3/C) is a constellation of six microsatellites launched on April 15, 2006 and has been orbiting with 72° inclination at 700 to 800 km above the earth since December 2007. The main payload of the F3/C is the GPS Occultation eXperiment (GOX) which carries out probing the radio occultation (RO) total electron content between GPS satellite and F3/C. Therefore, F3/C provides us an excellent opportunity to vertically scan ionospheric electron density from 100 up to 800 km altitude. On the other hand, worldwide ground-based GPS receivers can be employed to observe traveling ionospheric disturbances of the TEC. Here, we present the ionosphere response to seismic and tsunami waves by means of F3/C RO TEC and worldwide ground-based GPS TEC as well as existing data of infrasondes, magnetometers, and Doppler sounding systems during the 11 March 2011 M9.0 Tohoku earthquake.

  4. Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

    Science.gov (United States)

    Galvan, David A.; Komjathy, Attila; Hickey, Michael; Foster, James; Mannucci, Anthony J.

    2010-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

  5. Observing Traveling Ionospheric Disturbances Caused by Tsunamis Using GPS TEC Measurements

    Science.gov (United States)

    Galvan, David A.; Komjathy, Attila; Hickey, Michael; Foster, James; Mannucci, Anthony J.

    2010-01-01

    Ground-based Global Positioning System (GPS) measurements of ionospheric Total Electron Content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the American Samoa earthquake of September 29, 2009, and the Chile earthquake of February 27, 2010. Fluctuations in TEC correlated in time, space, and wave properties with these tsunamis were observed in TEC estimates processed using JPL's Global Ionospheric Mapping Software. These TEC estimates were band-pass filtered to remove ionospheric TEC variations with wavelengths and periods outside the typical range of internal gravity waves caused by tsunamis. Observable variations in TEC appear correlated with the tsunamis in certain locations, but not in others. Where variations are observed, the typical amplitude tends to be on the order of 1% of the background TEC value. Variations with amplitudes 0.1 - 0.2 TECU are observable with periods and timing affiliated with the tsunami. These observations are compared to estimates of expected tsunami-driven TEC variations produced by Embry Riddle Aeronautical University's Spectral Full Wave Model, an atmosphere-ionosphere coupling model, and found to be in good agreement in some locations, though there are cases when the model predicts an observable tsunami-driven signature and none is observed. These TEC variations are not always seen when a tsunami is present, but in these two events the regions where a strong ocean tsunami was observed did coincide with clear TEC observations, while a lack of clear TEC observations coincided with smaller tsunami amplitudes. There exists the potential to apply these detection techniques to real-time GPS TEC data, providing estimates of tsunami speed and amplitude that may be useful for early warning systems.

  6. Regional optimization of the IRI-2012 output (TEC, foF2) by using derived GPS-TEC

    Science.gov (United States)

    Ssessanga, Nicholas

    2016-07-01

    Accurate measurement and determination of the state of the ionosphere has become a key point as ground-based communication systems become more space dependent. However, due to limited infrastructure, a number of global models have been developed with extensive interpolation techniques to comprehensively describe ionospheric dynamics. As a result, most global models do not perform adequately in regions with a paucity of ionospheric measurements. In this paper, the most recent International Reference Ionosphere (IRI-2012) model output, Total Electron Content (TEC) and F2 layer critical frequency (foF2), are optimized (over a range of 120 ° E-150 ° E and 20 ° N-50 ° N in longitude and latitude, respectively). To obtain the optimal solution, we adjust two input parameters, the 12-month running mean sun spot number (R12) and the ionospheric index (IG12), in relation to the derived Global Positioning System (GPS) vertical TEC (VTEC). The results are compared to the measured TEC and foF2 from GPS receivers and ionosondes, respectively. The analysis shows that the modified IRI-2012 model is more accurate at estimating both the TEC and the foF2 values than the original model during days of geomagnetic quiet and disturbance.

  7. Latitudinal characteristics of GPS derived ionospheric TEC: a comparative study with IRI 2012 model

    Directory of Open Access Journals (Sweden)

    Monti Chakraborty

    2014-10-01

    Full Text Available The present study investigates the variation of Total Electron Content (TEC using Global Positioning System (GPS satellites from four equatorial to mid-latitudes stations over a period of one year. The stations are Port Blair (11.63°N, 92.70°E, Agartala (23.75°N, 91.25°E, Lhasa (29.65°N, 91.10°E and Urumqi (43.46°N, 87.16°E. The diurnal, monthly and seasonal variations of TEC have been explored to study its latitudinal characteristics. Analysis of TEC data from these stations reveals the characteristics of latitudinal variation of Equatorial Ionospheric Anomaly (EIA. To validate the latest IRI 2012 model, the monthly and seasonal variations of GPS-TEC at all the four stations have been compared with the model for three different topside options of electron density, namely, NeQuick, IRI-01-corr and IRI-2001. TEC predictions from IRI-2001 top side electron density option using IRI 2012 model overestimates the observed TEC especially at the low latitudes. TEC from IRI- NeQuick and IRI-01-corr options shows a tendency to underestimate the observed TEC during the day time particularly in low latitude region in the high solar activity period. The agreement between the model and observed values are reasonable in mid latitude regions. However, a discrepancy between IRI 2012 derived TEC with the ground based observations at low latitude regions is found. The discrepancy appears to be higher in low-latitude regions in comparison to mid latitude regions. It is concluded that largest discrepancy in TEC occur as a result of poor estimation of the hmF2 and foF2 from the coefficients.

  8. Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Ground-Based Global Positioning System (GPS) Meteorology Integrated Precipitable Water Vapor (IPW) data set measures atmospheric water vapor using ground-based...

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

    Directory of Open Access Journals (Sweden)

    E. Zuccheretti

    1997-06-01

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

  10. Comparison of Ionospheric TEC Derived from GPS and IRI 2012 Model during Geomagnetic Storms at Indonesia

    Science.gov (United States)

    Marlia, Dessi; Wu, Falin

    2016-07-01

    This paper investigates the variations of vertical Total Electron Content (VTEC) at Manado, Indonesia (geographic coordinates : lat 1.34 ° S and long 124.82 ° E) for period 2013. The GPS measured TEC is compared with the TEC derived from the IRI (International Reference Ionosphere) 2012 model. Vertical TEC measurements obtained from dual frequency GPS receiver that is GISTM (GPS Ionospheric Scintillations and TEC monitor). Variation of TEC validate to IRI 2012 model at Manado station has been compared with the model for three different topside of electron density namely NeQuick, IRI-01-Corr and IRI2001.There is a need to investigation on diurnal, seasonal variations, solar activity dependence of TEC and including effects of space weather related events to TEC and modeling of TEC. In this paper, diurnal and seasonal variations of VTEC and the effect of VTEC due to space weather events like Geomagnetic storms are analyzed. The result show that the TEC prediction using IRI-2001 model overestimated the GPS TEC measurements, while IRI-NeQuick and IRI-01-corr show a tendency to underestimates the observed TEC during the day time particularly in low latitude region in the maximum solar activity period (2013). The variations of VTEC during 17th March, 2013, 29th June, 2013 storms are analyzed. During 17th March,2013 storm enhancement in VTEC with Kp value 6 and Disturbance storm index (DST) -132 nT. During 29th June, 2013 storm VTEC depletion with value 7 and DST -98 nT. Significant deviations in VTEC during the main phase of the storms are observed. It is found that the response of ionospheric TEC consist of effects of both enhancement and depletions in ionospheric structures (positive and negative storm). Keywords: TEC ionosphere, GPS, GISTM, IRI 2012 model, solar activity, geomagnetic storm

  11. Preliminary results and analyses of using IGS GPS data to determine global ionospheric TEC

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Using the spherical harmonic (SH) function model and the dual frequency GPS data of 139 International GPS Service (IGS) stations for July 15 of 2000, the global ionospheric total electron content (TEC) is calculated and the basic method is investigated. Here, preliminary results are reported and the problems and difficulties to be solved for using GPS data to determine the global ionospheric TEC are discussed.

  12. Global Three-Dimensional Ionospheric Data Assimilation Model Using Ground-based GPS and Radio Occultation Total Electron Content

    Science.gov (United States)

    Jann-Yenq Liu, Tiger; Lin, Chi-Yen; Matsuo, Tomoko; Lin, Charles C. H.; Tsai, Ho-Fang; Chen, Chao-Yen

    2017-04-01

    An ionospheric data assimilation approach presented here is based on the Gauss-Markov Kalman filter with International Reference Ionosphere (IRI) as the background model and designed to assimilate the total electron content (TEC) observed from ground-based GPS receivers and space-based radio occultation (RO) of FORMOSAT-3/COSMIC (F3/C) or FORMOSAT-7/COSMIC-2 (F7/C2). The Kalman filter consists of the forecast step according to Gauss-Markov process and measurement update step. Observing System Simulation Experiments (OSSEs) show that the Gauss-Markov Kalman filter procedure can increase the accuracy of the data assimilation analysis over the procedure consisting of the measurement update step alone. Moreover, in comparing to F3/C, the dense F7/C2 RO observation can further increase the model accuracy significantly. Validating the data assimilation results with the vertical TEC in Global Ionosphere Maps and that derived from ground-based GPS measurements, as well as the ionospheric F2-peak height and electron density sounded by ionosondes is also carried out. Both the OSSE results and the observation validations confirm that the developed data assimilation model can be used to reconstruct the three-dimensional electron density in the ionosphere satisfactorily.

  13. Modeling and analysis of GPS-TEC low latitude climatology during the 24th solar cycle using empirical orthogonal functions

    Science.gov (United States)

    Dabbakuti, J. R. K. Kumar; Venkata Ratnam, D.

    2017-10-01

    The Total Electron Content (TEC) is an essential component describing the temporal and spatial characteristics of the ionosphere. In this paper, an empirical orthogonal function (EOF) model is constructed by using ground based Global Navigational Satellite System (GNSS) TEC observation data at the Bangalore International GNSS Service (IGS) station (geographic - 13.02° N, 77.57° E; geomagnetic latitude 4.4° N) during an extended period (2009-2016) in the 24th solar cycle. EOF model can be decomposed into base functions and its corresponding coefficients. These decomposed modes well represented the influence of solar and geomagnetic activity towards TEC. The first three EOFs modes constitute about 98% of the total variance of the observed data sets. The Fourier Series Analysis (FSA) is carried out to characterize the solar-cycle, annual and semi-annual dependences by modulating the first three EOF coefficients with solar (F10.7) and geomagnetic (Ap and Dst) indices. The TEC model is validated during daytime and nighttime conditions as well as under different solar activity and geomagnetic conditions. A positive correlation (0.85) of averaged daily GPS-TEC with averaged daily F10.7 strongly supports those time-varying characteristics of the ionosphere features depends on the solar activity. Further, the validity and reliability of EOF model is verified by comparing with the GPS-TEC data, and standard global ionospheric models (International Reference Ionosphere, IRI2016 and Standard Plasmasphere-Ionosphere Model, SPIM). The performances of the standard ionospheric models are marked to be relatively better during High Solar Activity (HSA) periods as compared to the Low Solar Activity (LSA) periods.

  14. Estimation Method of Ionospheric TEC Distribution using Single Frequency Measurements of GPS Signals

    Directory of Open Access Journals (Sweden)

    Win Zaw Hein

    2016-12-01

    Full Text Available The satellite-to-ground communications are influenced by ionospheric plasma which varies depending on solar and geomagnetic activities as well as regions and local times. With the expansion of use of the space, continuous monitoring of the ionospheric plasma has become an important issue. In Global Positioning System (GPS, the ionospheric delay, which is proportional to ionospheric total electron content (TEC along the propagation path, is the largest error in signal propagation. The TEC has been observed from dual frequency GPS signals because only the ionospheric delay has frequency dependences. Costs of multi-frequency receivers are, however, much higher than those of single frequency ones. In the present study, an estimation method of TEC distribution map from single frequency GPS measurements was developed. The developed method was evaluated by comparing its results with those from dual frequency measurements. The method makes it possible to expand ionospheric TEC observation networks easily.

  15. Ground Based GPS Phase Measurements for Atmospheric Sounding

    Science.gov (United States)

    2016-06-14

    based GPS observations for the correction of radar observations. 6 REFERENCES Alber, C., R. Ware, C. Rocken, and J. Braun, A new method for sensing ...rocken@ucar.edu Award #: N00014-97-1-0258 LONG-TERM GOAL The goal is to develop GPS remote sensing techniques to determine atmospheric signal delay and...agrees best with the observations in a least squares sense is selected. The corresponding refractivity profile is then selected. • We tested this

  16. REMOTE SENSING OF WATER VAPOR CONTENT USING GROUND-BASED GPS DATA

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Spatial and temporal resolution of water vapor content is useful in improving the accuracy of short-term weather prediction.Dense and continuously tracking regional GPS arrays will play an important role in remote sensing atmospheric water vapor content.In this study,a piecewise linear solution method was proposed to estimate the precipitable water vapor (PWV) content from ground-based GPS observations in Hong Kong.To evaluate the solution accuracy of the water vapor content sensed by GPS,the upper air sounding data (radiosonde) that are collected locally was used to calculate the precipitable water vapor during the same period.One-month results of PWV from both ground-based GPS sensing technique and radiosonde method are in agreement within 1~2 mm.This encouraging result will motivate the GPS meteorology application based on the establishment of a dense GPS array in Hong Kong.

  17. Storm induced large scale TIDs observed in GPS derived TEC

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    C. Borries

    2009-04-01

    Full Text Available This work is a first statistical analysis of large scale traveling ionospheric disturbances (LSTID in Europe using total electron content (TEC data derived from GNSS measurements. The GNSS receiver network in Europe is dense enough to map the ionospheric perturbation TEC with high horizontal resolution. The derived perturbation TEC maps are analysed studying the effect of space weather events on the ionosphere over Europe.

    Equatorward propagating storm induced wave packets have been identified during several geomagnetic storms. Characteristic parameters such as velocity, wavelength and direction were estimated from the perturbation TEC maps. Showing a mean wavelength of 2000 km, a mean period of 59 min and a phase speed of 684 ms−1 in average, the perturbations are allocated to LSTID. The comparison to LSTID observed over Japan shows an equal wavelength but a considerably faster phase speed. This might be attributed to the differences in the distance to the auroral region or inclination/declination of the geomagnetic field lines.

    The observed correlation between the LSTID amplitudes and the Auroral Electrojet (AE indicates that most of the wave like perturbations are exited by Joule heating. Particle precipitation effects could not be separated.

  18. Evaluation of Real-Time Ground-Based GPS Meteorology

    Science.gov (United States)

    Fang, P.; Bock, Y.; Gutman, S.

    2003-04-01

    We demonstrate and evaluate a system to estimate zenith tropospheric delays in real time (5-10 minute latency) based on the technique of instantaneous GPS positioning as described by Bock et al. [2000] using data from the Orange County Real Time GPS Network. OCRTN is an upgrade of a sub-network of SCIGN sites in southern California to low latency (1-2 sec), high-rate (1 Hz) data streaming. Currently, ten sites are streaming data (Ashtech binary MBEN format) by means of dedicated, point-to-point radio modems to a network hub that translates the asynchronous serial data to TCP/IP and onto a PC workstation residing on a local area network. Software residing on the PC allows multiple clients to access the raw data simultaneously though TCP/IP. One of the clients is a Geodetics RTD server that receives and archives (1) the raw 1 Hz network data, (2) estimates of instantaneous positions and zenith tropospheric delays, and (3) RINEX data to decimated to 30 seconds. The network is composed of ten sites. The distribution of nine of the sites approximates a right triangle with two 60 km legs, and a tenth site on Catalina Island a distance of about 50 km (over water) from the hypotenuse of the triangle. Relative zenith delays are estimated every second with a latency less than a second. Median values are computed at a user-specified interval (e.g., 10 minutes) with outliers greater than 4 times the interquartile range rejected. We describe the results with those generated by our operational system using the GAMIT software, with a latency of 30-60 minutes. Earlier results (from a similar network) comparing 30-minute median RTD values to GAMIT 30-minute estimates indicate that the two solutions differ by about 1 cm. We also describe our approach to determining absolute zenith delays. If an Internet connection is available we will present a real-time demonstration. [Bock, Y., R. Nikolaidis, P. J. de Jonge, and M. Bevis, Instantaneous resolution of crustal motion at medium

  19. Ionospheric data assimilation with thermosphere-ionosphere-electrodynamics general circulation model and GPS-TEC during geomagnetic storm conditions

    Science.gov (United States)

    Chen, C. H.; Lin, C. H.; Matsuo, T.; Chen, W. H.; Lee, I. T.; Liu, J. Y.; Lin, J. T.; Hsu, C. T.

    2016-06-01

    The main purpose of this paper is to investigate the effects of rapid assimilation-forecast cycling on the performance of ionospheric data assimilation during geomagnetic storm conditions. An ensemble Kalman filter software developed by the National Center for Atmospheric Research (NCAR), called Data Assimilation Research Testbed, is applied to assimilate ground-based GPS total electron content (TEC) observations into a theoretical numerical model of the thermosphere and ionosphere (NCAR thermosphere-ionosphere-electrodynamics general circulation model) during the 26 September 2011 geomagnetic storm period. Effects of various assimilation-forecast cycle lengths: 60, 30, and 10 min on the ionospheric forecast are examined by using the global root-mean-squared observation-minus-forecast (OmF) TEC residuals. Substantial reduction in the global OmF for the 10 min assimilation-forecast cycling suggests that a rapid cycling ionospheric data assimilation system can greatly improve the quality of the model forecast during geomagnetic storm conditions. Furthermore, updating the thermospheric state variables in the coupled thermosphere-ionosphere forecast model in the assimilation step is an important factor in improving the trajectory of model forecasting. The shorter assimilation-forecast cycling (10 min in this paper) helps to restrain unrealistic model error growth during the forecast step due to the imbalance among model state variables resulting from an inadequate state update, which in turn leads to a greater forecast accuracy.

  20. Extracting Regional Ionospheric TEC Measurements from Dense GPS (GNSS) Networks in Areas of High Seismic Risk

    Science.gov (United States)

    Reuveni, Y.; Bock, Y.; Geng, J.; Tong, X.; Moore, A. W.

    2013-12-01

    The ionosphere structure and peak electron density vary strongly with time, geographic location, and certain solar and geomagnetic disturbances, causing it to be dynamically variable, and hence, one of the main sources of GPS errors. Since ionospheric delays are a key limitation to successful GPS integer-cycle phase ambiguity resolution and point positioning accuracy, it is useful to estimate these delays on regional scales when using dense GPS networks. When estimating the Total Electron Content (TEC), one has to take into account the inner delay differences between the two frequencies, which are also known as the Differential Code Biases (DCBs), and can cause errors of several meters if they are ignored. Although DCB estimates for GNSS satellites and IGS ground receivers are provided on a regular basis by the International GNSS Service (IGS) analysis centers (such as CODE, JPL, and ESA), the DCBs for regional and local network receivers are not provided, and some of the IGS ground receiver estimates are not available from all analysis centers. Additionally, the DCB estimates vary between different GNSS satellites and ground receivers, where the majority of the DCBs values are based on the assumption that they are constant over 1 day or 1 month for any given GPS satellite or receiver. However, this assumption is far from being valid, since in fact the DCB values often vary diurnally or semi-diurnally. Developing and implementing regional ionospheric TEC models can be used in real-time to reduce errors in precise point positioning for dense real-time GPS networks. In addition, regional TEC maps extracted from GPS ionospheric path delays can be used, along with tropospheric delays, for mitigating errors in Interferometric Synthetic Aperture Radar (InSAR) images, especially for the L-band signals. The regional ionospheric TEC maps can also be used for the detection and characterization of ionospheric perturbations, which is valuable for both telluric natural hazards

  1. GPS scintillation and TEC depletion near the northern crest of equatorial anomaly over South China

    Science.gov (United States)

    Deng, Baichang; Huang, Jiang; Liu, Weifeng; Xu, Jie; Huang, Lingfeng

    2013-02-01

    This study presents a statistical analysis of GPS L-band scintillation with data observed from July 2008 to March 2012 at the northern crest of equatorial anomaly stations in Guangzhou and Shenzhen of South China. The variations of the scintillation with local time, season, solar activity and duration of scintillation patches were investigated. The relationship between the scintillation and TEC depletion was also reported. Our results revealed that GPS scintillation occurred from 19:30 LT (pre-midnight) to 03:00 LT (post-midnight). During quiet solar activity years, the scintillation was only observed in pre-midnight hours of equinox months and patches durations were mostly less than 60 min. During high solar activity years, more scintillation occurred in the pre-midnight hours of equinox and winter months; and GPS scintillation started to occur in the post-midnight hours of summer and winter. The duration of scintillation patches extended to 180 min in high solar activity years. Solar activity had a larger effect to strong scintillations (S4 > 0.6) than to weak scintillations (0.6 ⩾ S4 > 0.2). Strong scintillations were accompanied by TEC depletion especially in equinox months. We also discussed the relationship between TEC depletion and plasma bubble.

  2. CASES: A Novel Low-Cost Ground-based Dual-Frequency GPS Software Receiver

    Science.gov (United States)

    Haacke, B.; Crowley, G.; Reynolds, A.; Bust, G. S.; Kintner, P. M.; Psaiki, M.; Humphreys, T. E.; Powell, S.; O'Hanlon, B.

    2010-12-01

    GPS receivers can be used for monitoring space weather events such as TEC variations and scintillation. The new CASES GPS sensor developed by ASTRA, Cornell and UTAustin represents a revolutionary advance in dual frequency GPS space-weather monitoring. CASES is a paperback-novel-sized dual-frequency GPS software receiver with robust dual-frequency tracking performance, stand-alone capability, and complete software upgradability. This sensor measures and calculates TEC with a relative accuracy of a few 0.01 TECU at a cadence of up to 100 Hz. It measures amplitude and phase at up to 100 Hz on both L1 and L2, for up to 12 satellites in view. It calculates the scintillation severity indicators S4, τ0, and σφ at a cadence that is user defined. It is able to track through scintillation with {S4, τ0, amplitude} combinations as severe as {0.8, 0.8 seconds, 43 dB-Hz (nominal)} (i.e., commensurate with vigorous post-sunset equatorial scintillation) with a mean time between cycle slips greater than 240 seconds and with a mean time between frequency-unlock greater than 1 hour. Other capabilities and options include: Various data interface solutions; In-receiver and network-wide calibration of biases, and detection and mitigation of multipath; Network-wide automated remote configuration of receivers, quality control, re-processing, archiving and redistribution of data in real-time; Software products for data-processing and visualization. The low price of the sensor means that many more instruments can be purchased on a fixed budget, which will lead to new kinds of opportunities for monitoring and scientific study, including networked applications. Other uses for CASES receivers include geodetic and seismic monitoring, measurement of precipitable water vapor in the troposphere at meso-scale resolution, and educational outreach.

  3. Precipitable Water Vapor Estimates in the Australian Region from Ground-Based GPS Observations

    Directory of Open Access Journals (Sweden)

    Suelynn Choy

    2015-01-01

    Full Text Available We present a comparison of atmospheric precipitable water vapor (PWV derived from ground-based global positioning system (GPS receiver with traditional radiosonde measurement and very long baseline interferometry (VLBI technique for a five-year period (2008–2012 using Australian GPS stations. These stations were selectively chosen to provide a representative regional distribution of sites while ensuring conventional meteorological observations were available. Good agreement of PWV estimates was found between GPS and VLBI comparison with a mean difference of less than 1 mm and standard deviation of 3.5 mm and a mean difference and standard deviation of 0.1 mm and 4.0 mm, respectively, between GPS and radiosonde measurements. Systematic errors have also been discovered during the course of this study, which highlights the benefit of using GPS as a supplementary atmospheric PWV sensor and calibration system. The selected eight GPS sites sample different climates across Australia covering an area of approximately 30° NS/EW. It has also shown that the magnitude and variation of PWV estimates depend on the amount of moisture in the atmosphere, which is a function of season, topography, and other regional climate conditions.

  4. Receiver DCB estimation and GPS vTEC study at a low latitude station in the South Pacific

    Science.gov (United States)

    Prasad, Ramendra; Kumar, Sushil; Jayachandran, P. T.

    2016-11-01

    The statistical estimation of receiver differential code bias (DCB) of the GSV4004B receiver at a low latitude station, Suva (lat. 18.15°S, long. 178.45°E, Geomag. Lat. 21.07°S), Fiji, and the subsequent behaviour of vTEC, are presented. By means of least squares linear regression fitting technique, the receiver DCB was determined using the GPS vTEC data recorded during the year 2010, CODE TEC and IRI-2012 model for 2010. To substantiate the results, minimization of the standard deviation (SD) method was also used for GPS vTEC data. The overall monthly DCB was estimated to be in the range of 62.6 TECU. The vTEC after removing the resultant monthly DCB was consistent with other low latitude observations. The GPS vTEC 2010 data after eliminating the resultant DCB were lower in comparison to Faraday rotation vTEC measurements at Suva during 1984 primarily due to higher solar activity during 1984 as compared to 2010. Seasonally, vTEC was maximum during summer and minimum during winter. The winter showed least vTEC variability whereas equinox showed the largest daytime variability. The geomagnetic disturbances effect showed that both vTEC and its variability were higher on magnetically disturbed days as compared to quiet days with maximum variability in the daytime. Two geomagnetic storms of moderate strengths with main phases in the local daytime showed long duration (∼52 h) increase in vTEC by 33-67% which can be accounted by changes in E×B drifts due to prompt penetration of storm-time auroral electric field in the daytime and disturbance dynamo electric field in the nighttime to low latitudes.

  5. Study of the ionospheric TEC using GPS during the large solar flare burst on Nov.6,1997

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using the data from 15 global positioning system (GPS) stations scattered between 28° N-45° N and 90° W- 77° E,we obtained the total electron content (TEC) variations with time during a large solar flare.The results indicated that the flare makes the TEC of ionosphere increasing in a large spatial area.The amounts of the TEC enhancement are mainly determined by the local time of subionospheric point,and the largest TEC enhancement is about 2.5 TECU.It is also concluded that the TEC enhancement is not symmetrical about the local noon time,the TEC enhancement values during morning hours are larger than those of the afternoon hours.

  6. Analysis of traveling ionospheric disturbances (TIDs) in GPS TEC launched by the 2011 Tohoku earthquake

    Science.gov (United States)

    Crowley, Geoff; Azeem, Irfan; Reynolds, Adam; Duly, Timothy M.; McBride, Patrick; Winkler, Clive; Hunton, Don

    2016-05-01

    Traveling ionospheric disturbances (TIDs) have been detected using various measurement techniques, including HF sounders, incoherent scatter radars, in situ measurements, and optical techniques. However, observations of TIDs have tended to be sparse and there is a need for additional observations to provide new scientific insight into the geophysical source phenomenology and wave propagation physics. The dense network of GPS receivers around the globe offers a relatively new data source to observe and monitor TIDs. In this paper, we use total electron content (TEC) measurements from ~4000 GPS receivers throughout the continental United States to observe TIDs associated with the 11 March 2011 Tohoku tsunami. The tsunami propagated across the Pacific to the U.S. west coast over several hours, and we show that corresponding TIDs were observed in the US. Using this network of GPS receivers we present a 2D imaging of TEC perturbations and calculate various TID parameters, including horizontal wavelength, speed, and period. Well-formed, planar TIDs were detected over the west coast of the U.S. ~10 h after the earthquake. Fast Fourier transform analysis of the observed waveforms revealed that the period of the wave was 15.1 min with a horizontal wavelength of 194.8 km, phase velocity of 233.0 m/s, and an azimuth of 105.2° (propagating nearly due east in the direction of the tsunami wave). These results are consistent with the TID observations in airglow measurements from Hawaii earlier in the day and with other GPS TEC observations.

  7. Use of GPS TEC Maps for Calibrating Single Band VLBI Sessions

    Science.gov (United States)

    Gordon, David

    2010-01-01

    GPS TEC ionosphere maps were first applied to a series of K and Q band VLBA astrometry sessions to try to eliminate a declination bias in estimated source positions. Their usage has been expanded to calibrate X-band only VLBI observations as well. At K-band, approx.60% of the declination bias appears to be removed with the application of GPS ionosphere calibrations. At X-band however, it appears that up to 90% or more of the declination bias is removed, with a corresponding increase in RA and declination uncertainties of approx.0.5 mas. GPS ionosphere calibrations may be very useful for improving the estimated positions of the X-only and S-only sources in the VCS and RDV sessions.

  8. Comparison of GPS-TEC measurements with IRI-2007 and IRI-2012 modeled TEC at an equatorial latitude station, Bangkok, Thailand

    Science.gov (United States)

    Arunpold, Sanit; Tripathi, Nitin K.; Rajesh Chowdhary, V.; Raju, Durairaju Kumaran

    2014-09-01

    This paper presents the first vertical total electron content (VTEC) data derived from a dual-frequency GPS receiver installed at the Asian Institute of Technology in Bangkok, as part of project SCINDA (Scintillation Network and Decision Aid) with a magnetic dip latitude of 14°N, The diurnal, monthly, and seasonal variation in TEC, measured between August 2010 and July 2012, was compared with values derived from two International Reference Ionosphere (IRI) models: the IRI-2007 and the recently released IRI-2012. The highest diurnal TEC always occurred between 08:00 and 12:00 Universal Time (UT). The diurnal pattern of GPS-TEC reached its maximum values during equinoctial months (March, April, September, and October) and minimum values during solstice months (June, July, December, and January), which can be attributed to the solar extreme ultra-violet ionization coupled with the upward vertical E×B drift. The modeled TEC was underestimated in 2010 and 2011 and overestimated in 2012, especially with the IRI-2007 model. The measured values were better correlated with the IRI-2012 model, especially in 2012. However, neither of the IRI models responded to geomagnetic activity, despite the selection of the “storm” option, generally showing a smooth curve and underestimating TEC during a storm. To verify this phenomenon, the impacts of geomagnetic storms were considered.

  9. Assimilative Modeling of Ionospheric Disturbances with FORMOSAT-3/COSMIC and Ground-Based GPS Measurements

    Directory of Open Access Journals (Sweden)

    Xiaoqing Pi

    2009-01-01

    Full Text Available The four-dimensional Global Assimilative Ionospheric Model (GAIM is applied to a study of ionospheric disturbances. The investigation is focused on disturbance features, particularly in the altitude and latitude dimensions, at low latitudes during a geomagnetic storm on 7 August 2006, under solar minimum conditions. The modeling of storm-time ionospheric state (electron density is conducted by assimilating an unprecedented volume of line-of-sight TEC data collected by the Global Positioning System (GPS occultation receivers on board six FORMOSAT-3/COSMIC satellites and geodetic-quality GPS receivers at two hundred globally-distributed ground tracking stations.With a band-limited Kalman filter technique to update the ionospheric state, the assimilative modeling reveals a pronounced enhancement in the equatorial anomaly in the East Asia sector during dusk and evening hours. The disturbance characteristics, obtained by comparing with the quiet conditions prior to the storm also modeled in this study through data assimilation, include lifted F layer and reduced electron density in the equatorial region, enhanced density at the magnetically conjugate anomaly latitudes, and tilted feature of density increase towards higher altitudes at lower latitudes. The characteristics are attributed to the enhanced plasma fountain effect driven by an enhanced eastward zonal electric field. These results enable us to distinguish the storm-time electric field perturbations clearly from other sources during the storm. The possible origins of electric field perturbations are also discussed, including penetration of the magnetospheric electric field and wind dynamo disturbances.

  10. Geocenter Coordinates from a Combined Processing of LEO and Ground-based GPS Observations

    Science.gov (United States)

    Männel, Benjamin; Rothacher, Markus

    2017-04-01

    The GPS observations provided by the global IGS (International GNSS Service) tracking network play an important role for the realization of a unique terrestrial reference frame that is accurate enough to allow the monitoring of the Earth's system. Combining these ground-based data with GPS observations tracked by high-quality dual-frequency receivers on-board Low Earth Orbiters (LEO) might help to further improve the realization of the terrestrial reference frame and the estimation of the geocenter coordinates, GPS satellite orbits and Earth rotation parameters (ERP). To assess the scope of improvement, we processed a network of 50 globally distributed and stable IGS-stations together with four LEOs (GRACE-A, GRACE-B, OSTM/Jason-2 and GOCE) over a time interval of three years (2010-2012). To ensure fully consistent solutions the zero-difference phase observations of the ground stations and LEOs were processed in a common least-square adjustment, estimating GPS orbits, LEO orbits, station coordinates, ERPs, site-specific tropospheric delays, satellite and receiver clocks and ambiguities. We present the significant impact of the individual LEOs and a combination of all four LEOs on geocenter coordinates derived by using a translational approach (also called network shift approach). In addition, we present geocenter coordinates derived from the same set of GPS observations by using a unified approach. This approach combines the translational and the degree-one approach by estimating translations and surface deformations simultaneously. Based on comparisons against each other and against geocenter time series derived by other techniques the effect of the selected approach is assessed.

  11. The dynamics and spectral characteristics of the GPS TEC wave packets excited by the solar terminator

    Science.gov (United States)

    Afraimovich, E. L.; Edemsky, I. K.; Voeykov, S. V.; Yasukevich, Y. V.; Zhivetiev, I. V.

    2009-04-01

    The great variety of solar terminator (ST) -linked phenomena in the atmosphere gave rise to a num¬ber of studies on the analysis of ionosphere parameter variations obtained by different ionosphere sounding methods. Main part of experimental data was obtained using methods for analyzing the spectrum of ionosphere parameter variations in separate local points. To identify ST-generated wave disturbances it is necessary to measure the dynamic and spectral characteristics of the wave disturbances and to compare it with spatial-temporal characteristics of ST. Using TEC measurements from the dense network of GPS sites GEONET (Japan), we have obtained the first GPS-TEC image of the space structure of medium-scale traveling wave packets (MS TWP) excited by the solar terminator. We use two known forms of the 2D GPS-TEC image for our presentation of the space structure of ST-generated MS TWP: 1) - the diagram "distance-time"; 2) - the 2D-space distribution of the values of filtered TEC series dI (λ, φ, t) on the latitude φ and longitude λ for each 30-sec TEC counts. We found that the time period and wave-length of ST-generated wave packets are about 10-20 min and 200-300 km, respectively. Dynamic images analysis of dI (λ, φ, t) gives precise estimation of velocity and azimuth of TWP wave front propagation. We use the method of determining velocity of traveling ionosphere disturbances (SADM-GPS), which take into account the relative moving of subionosphere points. We found that the velocity of the TWP phase front, traveling along GEONET sites, varies in accordance with the velocity of the ST line displacement. The space image of MS TWP manifests itself in pronounced anisotropy and high coherence over a long distance of about 2000 km. The TWP wave front extends along the ST line with the angular shift of about 20°. The hypothesis on the connection between the TWP generation and the solar terminator can be tested in the terminator local time (TLT) system: d

  12. Geocenter variations derived from a combined processing of LEO- and ground-based GPS observations

    Science.gov (United States)

    Männel, Benjamin; Rothacher, Markus

    2017-08-01

    GNSS observations provided by the global tracking network of the International GNSS Service (IGS, Dow et al. in J Geod 83(3):191-198, 2009) play an important role in the realization of a unique terrestrial reference frame that is accurate enough to allow a detailed monitoring of the Earth's system. Combining these ground-based data with GPS observations tracked by high-quality dual-frequency receivers on-board low earth orbiters (LEOs) is a promising way to further improve the realization of the terrestrial reference frame and the estimation of geocenter coordinates, GPS satellite orbits and Earth rotation parameters. To assess the scope of the improvement on the geocenter coordinates, we processed a network of 53 globally distributed and stable IGS stations together with four LEOs (GRACE-A, GRACE-B, OSTM/Jason-2 and GOCE) over a time interval of 3 years (2010-2012). To ensure fully consistent solutions, the zero-difference phase observations of the ground stations and LEOs were processed in a common least-squares adjustment, estimating all the relevant parameters such as GPS and LEO orbits, station coordinates, Earth rotation parameters and geocenter motion. We present the significant impact of the individual LEO and a combination of all four LEOs on the geocenter coordinates. The formal errors are reduced by around 20% due to the inclusion of one LEO into the ground-only solution, while in a solution with four LEOs LEO-specific characteristics are significantly reduced. We compare the derived geocenter coordinates w.r.t. LAGEOS results and external solutions based on GPS and SLR data. We found good agreement in the amplitudes of all components; however, the phases in x- and z-direction do not agree well.

  13. Topside-plasmasphere electron density profiles model by using AIS ionosonde measurements and calibrates GPS TEC data

    Science.gov (United States)

    Cesaroni, Claudio; Scotto, Carlo; Ippolito, Alessandro; Ciraolo, Luigi

    2013-04-01

    The Upper Atmosphere Physics group at INGV (Istituto Nazionale di Geofisica e Vulcanologia) developed Autoscala, a computer program for automatic scaling of the critical frequency foF2 and other ionospheric parameters derived from ionograms. Autoscala includes a routine that automatically estimates the electron density profile below F layer peak height hmF2, by adjusting the parameters of a model according to the recorded ionogram [Scotto (2009)]. By integrating this profile we can estimate bottom-side total electron content (bTEC). By means of a calibration technique [Ciraolo et al. (2007)], we are able to obtain calibrated vertical TEC (vTEC) values from GPS measurements over a receiver station. This method permits to estimate biases of the received signal due to transmitter-receiver hardware configuration. These biases must be eliminated from the GPS data in order to calibrate the experimental slant total electron content (sTEC) along the satellite-receiver line-of-sight (LoS). The difference between vTEC and bottom-side TEC (bTEC) permits to evaluate electron content of the topside ionospheric region (tTEC). Starting from tTEC, bottom-side parameters (foF2, hmF2, scale height at hmF2) obtained by ionosonde and O+ - H+ transition level, we can solve a system of equations based on different ionospheric profiler (Chapman, sech-squared and exponential) the solution of which provides ion scale height [Stankov et al. (2003)]. This last factor is sufficient to establish the vertical distribution of electrons in topside and plasmasphere regions. Obtained vertical profiles could be used to develop a new model for real time estimation of TEC and topside electron density distribution. References: Scotto, C. (2009). Electron density profile calculation technique for Autoscala ionogram analysis. Advances in Space Research, 44(6), 756-766. doi:10.1016/j.asr.2009.04.037 Ciraolo, L., et al. "Calibration errors on experimental slant total electron content (TEC) determined with

  14. Identification of ionospheric GPS TEC anomalies prior to earthquake in Sumatra between 2007-2012 using correlation technique

    Science.gov (United States)

    Vita, Aprilia Nur; Putra, Shandy Yogaswara Surya; Subakti, Hendri; Muslim, Buldan

    2017-07-01

    The occurrence of great earthquake as natural disaster is unavoidable and resulting a great loss in economy and human lives. So earthquake mitigation is a must to avoid greater loss in future. Past studies showed that there was ionospheric perturbation due to earthquake occurrence. This study analyzed the ionospheric Total Electron Content (TEC) before earthquake using Global Positioning System (GPS) data from Sumatran GPS Array (SuGAR) within 27 days using correlation technique. Correlation technique with anomaly threshold value was conducted to identify ionospheric variation related with earthquake preparation. From September 2007 until September 2012, 12 earthquakes occurred with magnitude > 6.0 over Sumatra, Indonesia. In result, ten of them preceded by TEC anomaly 1 to 24 days before earthquakes hit. The anomaly of TEC value is considered as effect of earthquake preparation activity after geomagnetic data validation.

  15. A recurrent neural network approach to quantitatively studying solar wind effects on TEC derived from GPS; preliminary results

    Directory of Open Access Journals (Sweden)

    J. B. Habarulema

    2009-05-01

    Full Text Available This paper attempts to describe the search for the parameter(s to represent solar wind effects in Global Positioning System total electron content (GPS TEC modelling using the technique of neural networks (NNs. A study is carried out by including solar wind velocity (Vsw, proton number density (Np and the Bz component of the interplanetary magnetic field (IMF Bz obtained from the Advanced Composition Explorer (ACE satellite as separate inputs to the NN each along with day number of the year (DN, hour (HR, a 4-month running mean of the daily sunspot number (R4 and the running mean of the previous eight 3-hourly magnetic A index values (A8. Hourly GPS TEC values derived from a dual frequency receiver located at Sutherland (32.38° S, 20.81° E, South Africa for 8 years (2000–2007 have been used to train the Elman neural network (ENN and the result has been used to predict TEC variations for a GPS station located at Cape Town (33.95° S, 18.47° E. Quantitative results indicate that each of the parameters considered may have some degree of influence on GPS TEC at certain periods although a decrease in prediction accuracy is also observed for some parameters for different days and seasons. It is also evident that there is still a difficulty in predicting TEC values during disturbed conditions. The improvements and degradation in prediction accuracies are both close to the benchmark values which lends weight to the belief that diurnal, seasonal, solar and magnetic variabilities may be the major determinants of TEC variability.

  16. The mapping of ionospheric TEC for central Russian and European regions on the base of GPS and GLONASS measurements

    Science.gov (United States)

    Shagimuratov, Irk; Cherniak, Iurii; Zakharenkova, Irina; Ephishov, Ivan; Krankowski, Andrzej; Radievsky, Alexander

    2014-05-01

    The total electron content (TEC) is a key parameter not only for space radio communication but also for addressing the fundamental problems of the ionosphere physics and near Earth space. Currently, the main sources of information on the TEC in the global scale are GNSS signals measurements. The spatial-temporal behavior of the ionosphere can be most effectively analyzed using TEC maps. To date, global IGS global ionospheric maps with a resolution of 2.5 degree in latitude and 5 in longitude and a time resolution of 2 h are most widely used. To study the detailed structure of the ionospheric gradients and rapid process as well as for precise positioning task it is necessary to use more precise regional TEC maps. The Regional TEC maps are currently constructed by different research groups for different regions: USA, Europe, Japan etc. The West Department of IZMIRAN research group is a one in Russia who works on the task of regional ionosphere mapping since 2000. It was developed the methodology for obtaining information on the spatial TEC distribution, TEC maps of the ionosphere on the basis of the algorithm for multi-station processing of GNSS observations. Using a set of algorithms and programs, regional TEC maps with a spatial resolution of 1° and a time resolution up to 15 min can be produced. Here is developed the approach to establish the regular online internet service for regional ionosphere mapping of the Western Russia and Eastern Europe. Nowadays the development of GLONASS navigation system is completely finished and it consists of a constellation of more than 24 satellites. It is good perspective for investigations of the ionosphere structure and dynamics on the base of the simultaneous observations of GPS and GLONASS systems. The GLONASS satellites have the inclination about 64 degrees as against GPS satellites with 56. So the GLONASS provides opportunity to study the high latitude ionosphere. The different scale electron density irregularities

  17. Assessment of NASA Airborne Laser Altimetry Data Using Ground-Based GPS Data near Summit Station, Greenland

    Science.gov (United States)

    Brunt, Kelly M.; Hawley, Robert L.; Lutz, Eric R.; Studinger, Michael; Sonntag, John G.; Hofton, Michelle A.; Andrews, Lauren C.; Neumann, Thomas A.

    2017-01-01

    A series of NASA airborne lidars have been used in support of satellite laser altimetry missions. These airbornelaser altimeters have been deployed for satellite instrument development, for spaceborne data validation, and to bridge the data gap between satellite missions. We used data from ground-based Global Positioning System (GPS) surveys of an 11 km long track near Summit Station, Greenland, to assess the surface elevation bias and measurement precision of three airborne laser altimeters including the Airborne Topographic Mapper (ATM), the Land, Vegetation, and Ice Sensor (LVIS), and the Multiple Altimeter Beam Experimental Lidar (MABEL). Ground-based GPS data from the monthly ground-based traverses, which commenced in 2006, allowed for the assessment of nine airborne lidar surveys associated with ATM and LVIS between 2007 and 2016. Surface elevation biases for these altimeters over the flat, ice-sheet interior are less than 0.12 m, while assessments of measurement precision are 0.09 m or better. Ground-based GPS positions determined both with and without differential post-processing techniques provided internally consistent solutions. Results from the analyses of ground-based and airborne data provide validation strategy guidance for the Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) elevation and elevation-change data products.

  18. Atmospheric Water Monitoring by Using Ground-Based GPS during Heavy Rains Produced by TPV and SWV

    Directory of Open Access Journals (Sweden)

    Guoping Li

    2013-01-01

    Full Text Available The time series of precipitable water (PW in 30 min intervals has been determined through experimentation and operational application of a ground-based global positioning system (GPS network in Chengdu Plain, which is used for precise and reliable meteorological research. This study is the first to apply PW to the southwest vortex (SWV and heavy rain events by using the data from an intensive SWV experiment conducted in summer 2010. The PW derived from the local ground-based GPS network was used in the monitoring and analysis of heavy rain caused by the SWV and the Tibetan Plateau vortex (TPV. Results indicate that an increase in GPS precipitable water (GPS-PW occurs prior to the development of the TPV and SWV; rainfall occurs mainly during high levels of GPS-PW. The evolution features of GPS-PW in rainfall process caused by different weather systems over the Tibetan Plateau (TP also differ. These results indicate the reference values for operational applications of GPS-PW data in short-term forecasting and nowcasting of high-impact weather in addition to further investigation of heavy rain caused by the TPV, SWV, and other severe weather systems over the TP.

  19. Application of IRI-Plas in Ionospheric Tomography and HF Communication Studies with Assimilation of GPS-TEC

    Science.gov (United States)

    Arikan, Feza; Gulyaeva, Tamara; Sezen, Umut; Arikan, Orhan; Toker, Cenk; Hakan Tuna, MR.; Erdem, Esra

    2016-07-01

    International Reference Ionosphere is the most acknowledged climatic model of ionosphere that provides electron density profile and hourly, monthly median values of critical layer parameters of the ionosphere for a desired location, date and time between 60 to 2,000 km altitude. IRI is also accepted as the International Standard Ionosphere model. Recently, the IRI model is extended to the Global Positioning System (GPS) satellite orbital range of 20,000 km. The new version is called IRI-Plas and it can be obtained from http://ftp.izmiran.ru/pub/izmiran /SPIM/. A user-friendly online version is also provided at www.ionolab.org as a space weather service. Total Electron Content (TEC), which is defined as the line integral of electron density on a given ray path, is an observable parameter that can be estimated from earth based GPS receivers in a cost-effective manner as GPS-TEC. One of the most important advantages of IRI-Plas is the possible input of GPS-TEC to update the background deterministic ionospheric model to the current ionospheric state. This option is highly useful in regional and global tomography studies and HF link assessments. IONOLAB group currently implements IRI-Plas as a background model and updates the ionospheric state using GPS-TEC in IONOLAB-CIT and IONOLAB-RAY algorithms. The improved state of ionosphere allows the most reliable 4-D imaging of electron density profiles and HF and satellite communication link simulations.This study is supported by TUBITAK 115E915 and joint TUBITAK 114E092 and AS CR 14/001.

  20. GPS based TEC measurements for a period August 2008–December 2009 near the northern crest of Indian equatorial ionospheric anomaly region

    Indian Academy of Sciences (India)

    S P Karia; K N Pathak

    2011-10-01

    In recent years, measurements of total electron content (TEC) have gained importance with increasing demand for the GPS-based navigation applications in trans-ionospheric communications. To study the variation in ionospheric TEC, we used the data obtained from GPS Ionospheric Scintillation and TEC monitoring (GISTM) system which is in operation at SVNIT, Surat, India (21.16°N, 72.78°E) located at the northern crest of equatorial anomaly region. The data collected (for the low sunspot activity period from August 2008–December 2009) were used to study the diurnal, monthly, seasonal semi-annual and annual variations of TEC at Surat. It was observed that the diurnal variation at the region reaches its maximum value between 13:00 and 16:00 IST. The monthly average diurnal variations showed that the TEC maximizes during the equinox months followed by the winter months, and are lowest during the summer months. The ionospheric range delay to TEC for the primary GPS signal is 0.162 m per TECU. The diurnal variation in TEC shows a minimum to maximum variation of about 5 to 50 TECU (in current low sunspot activity periods). These TEC values correspond to range delay variations of about 1 to 9 m at Surat. These variations in the range delay will certainly increase in high sunspot activity periods. Detected TEC variations are also closely related to space weather characterizing quantities such as solar wind and geomagnetic activity indices.

  1. Invesion of tsunami height using GPS TEC data. The case of the 2012 Haida Gwaii tsunami and Earthquake.

    Science.gov (United States)

    Rakoto, V.; Lognonne, P. H.; Rolland, L. M.

    2015-12-01

    Large earthquakes (i.eM>6) and tsunamis associated are responsible for ionospheric perturbations. These perturbations can be observed in the total electron content (TEC) measured from multi- frequency Global Navigation Satellite systems (GNSS) data (e.g GPS). We will focus on the studies of the Haïda Gwaii earthquake and tsunami case. It happened the 28 october 2012 along the Queen Charlotte fault of the Canada Western Coast. First, we compare GPS data of perturbation TEC to our model. We model the TEC perturbation in several steps. (1) First, we compute tsunami normal modes modes in atmosphere in using PREM model with 4.7km of oceanic layer. (2) We sum all the tsunami modes to obtain the neutral displacement. (3) We couple the ionosphere with the neutral atmosphere. (4) We integrate the perturbed electron density along each satellite station line of sight. At last, we present first results of TEC inversion in order to retrieve the waveform of the tsunami. This inversion has been done on synthetics data assuming Queen Charlotte Earthquake and Tsunami can be considered as a point source in far field.

  2. Variation of TEC and related parameters over the Indian EIA region from ground and space based GPS observations during the low solar activity period of May 2007-April 2008

    Science.gov (United States)

    Chakravarty, S. C.; Nagaraja, Kamsali; Jakowski, N.

    2017-03-01

    The annual variations of ionospheric Total Electron Content (TEC), F-region peak ionisation (NmF2) and the ionospheric slab thickness (τ) over the Indian region during the low solar activity period of May 2007-April 2008 have been studied. For this purpose the ground based TEC data obtained from GAGAN measurements and the space based data from GPS radio occultation technique using CHAMP have been utilised. The results of these independent measurements are combined to derive additional parameters such as the equivalent slab thickness of the total and the bottom-side ionospheric regions (τT and τB). The one year hourly average values of all these parameters over the ionospheric anomaly latitude region (10-26°N) are presented here along with the statistical error estimates. It is expected that these results are potentially suited to be used as base level values during geomagnetically quiet and undisturbed solar conditions.

  3. Ionospheric disturbances triggered by the 25 April, 2015 M7.8 Gorkha earthquake, Nepal: Constraints from GPS TEC measurements

    Science.gov (United States)

    Catherine, J. K.; Uma Maheshwari, D.; Gahalaut, V. K.; Roy, P. N. S.; Khan, P. K.; Puviarasan, N.

    2017-01-01

    The ionosphere response to the April 11, 2015 (Mw 7.8) Gorkha earthquake, occurring in the Himalayan arc, is analysed using GPS Total Electron Content (TEC) measurements, from GPS sites in Nepal and India, situated both close to and far from the epicentre. In the near field, the Coseismic Ionospheric disturbance (CID) following the earthquake rupture propagation arrive east of the epicentre, within 5-7 min with a propagation velocity of 980 m/s, equal to the speed of the shock acoustic waves at the ionospheric heights, and on to the west with a reduced speed of 650 m/s, within 8-11 min, after the earthquake occurrence. The phenomenon of CID splitting into two modes, east and west of the epicentre is observed. In the far-field region, up to epicentral distances of 2200 km, Rayleigh wave induced ionospheric disturbance are recorded with a propagation speed of 2.6 km/s. Higher TEC amplitude of 0.2-1.5 TECU is observed east of the epicentre compared to the west with 0.1-0.3 TECU. The characteristics of this dip-slip earthquake are well projected in the TEC waveforms. The ambient magnetic field in the mid-latitudes prohibited the propagation of ionospheric disturbance in the northward direction. In the present study the observed primary CID is essentially in congruence with the rupture propagation of the earthquake in E-SE direction.

  4. Synthesis Analysis of One Severe Convection Precipitation Event in Jiangsu Using Ground-Based GPS Technology

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2015-07-01

    Full Text Available Global positioning system (GPS detection technology has several advantageous characteristics (i.e., all-weather applications, high accuracy, high spatial and temporal resolution, and low cost, and GPS tracking and monitoring techniques for water vapor have developed rapidly in recent years. The GPS-precipitable water vapor (GPS-PWV, obtained through inversion using this technology can reflect the water vapor inflow and outflow in a vertical air column above a certain area in nearly real-time, which is especially important for areas of severe water vapor variation. In this paper, we studied the relationship between GPS-PWV variation and actual precipitation. The specific aim was to identify the underlying physical mechanisms driving the variation and to further strengthen the utility of GPS-PWV in forecasts and warnings of severe convection weather. We concluded that (1 rapid rise in the GPS-PWV in the long-term low-level data predicted the arrival of precipitation and was therefore useful in weather forecasts; (2 the GPS-PWV variation was closely related with the movement of the water vapor transfer belt; (3 the atmosphere showed an unstable energy structure before the GPS-PWV increase; and (4 local motion was strongly related with the development and maintenance of precipitation.

  5. Longitudinal Variation in GPS -TEC and Topside Electron Density Associated with the Wave Number Four Structures over South American Sector

    Science.gov (United States)

    Nogueira, P. A.; Abdu, M. A.; Souza, J. R.; Bailey, G. J.; Shume, E. B.; Denardini, C. M.

    2012-12-01

    Recent observations of the low-latitude ionospheric electron density have revealed a longitudinal structure in the Equatorial Ionization Anomaly (EIA) intensity, which is characterized by a wave number-four pattern when plotted at a constant-local-time frame. It has been proposed that neutral wind driven dynamo electric fields from the E-region due to non migrating tidal modes are responsible for this pattern. In the present work we have used measurements from the Defense Meteorological Satellite Program (DMSP) to investigate the four peaks structure in the topside electron density of the low latitude ionosphere. We also compare the climatology of the Total Electron Content (TEC) as observed by GPS receivers in two equatorial stations over South America, São Luís (2.33 S, 315.8E, declination = -19 degree) in Brazil and Arequipa (16.5S, 288.5E, declination = 0.5 degree) in Peru. TEC variations for three solar activity levels (high, moderate and low) have been analyzed. TEC values over São Luís are found to be larger than that ones over Arequipa independent of the season, local time and solar cycle conditions. We estimated the vertical plasma drifts over these stations using magnetometer data during daytime and using ionosonde data for evening hours. We fed the Sheffield University Plasmasphere Ionosphere Model (SUPIM) with this drifts in an attempt to partially explain the differences in the TEC over these stations. The SUPIM was also used to evaluate the effect of thermospheric wind to cause the four peaks structure in the plasma density. Therefore, we analyze the equatorial ionospheric response to combined effects of thermospheric neutral winds and zonal electric field causing the longitudinal variation in TEC observed in the South American longitude sector.

  6. Open-loop GPS signal tracking at low elevation angles from a ground-based observation site

    Science.gov (United States)

    Beyerle, Georg; Zus, Florian

    2017-01-01

    A 1-year data set of ground-based GPS signal observations aiming at geometric elevation angles below +2° is analysed. Within the "GLESER" measurement campaign about 2600 validated setting events were recorded by the "OpenGPS" open-loop tracking receiver at an observation site located at 52.3808° N, 13.0642° E between January and December 2014. The measurements confirm the feasibility of open-loop signal tracking down to geometric elevation angles of -1 to -1.5° extending the corresponding closed-loop tracking range by up to 1°. The study is based on the premise that observations of low-elevation events by a ground-based receiver may serve as test cases for space-based radio occultation measurements, even if the latter proceed at a significantly faster temporal scale. The results support the conclusion that the open-loop Doppler model has negligible influence on the derived carrier frequency profile for strong signal-to-noise density ratios above about 30 dB Hz. At lower signal levels, however, the OpenGPS receiver's dual-channel design, which tracks the same signal using two Doppler models differing by 10 Hz, uncovers a notable bias. The repeat patterns of the GPS orbit traces in terms of azimuth angle reveal characteristic signatures in both signal amplitude and Doppler frequency with respect to the topography close to the observation site. Mean vertical refractivity gradients, extracted from ECMWF meteorological fields, correlate weakly to moderately with observed signal amplitude fluctuations at geometric elevation angles between +1 and +2°. Results from multiple phase screen simulations support the interpretation that these fluctuations are at least partly produced by atmospheric multipath; at negative elevation angles diffraction at the ground surface seems to contribute.

  7. Precipitable water vapor and its relationship with the Standardized Precipitation Index: ground-based GPS measurements and reanalysis data

    Science.gov (United States)

    Bordi, Isabella; Zhu, Xiuhua; Fraedrich, Klaus

    2016-01-01

    Monthly means of ground-based GPS measurements of precipitable water vapor (PWV) from six stations in the USA covering the period January 2007-December 2012 are analyzed to investigate their usefulness for monitoring meteorological wet/dry spells. For this purpose, the relationship between PWV and the Standardized Precipitation Index (SPI) on 1-month timescale is investigated. The SPI time series at grid points close to the stations are computed using gridded precipitation records from the NOAA Climate Prediction Center (CPC) unified precipitation dataset (January 1948-April 2012). GPS measurements are first verified against PWV data taken from the latest ECMWF reanalysis ERA-Interim; these PWV reanalysis data, which extend back to 1979, are then used jointly with CPC precipitation to compute precipitation efficiency (PE), defined as the percentage of total water vapor content that falls onto the surface as measurable precipitation in a given time period. The overall results suggest that (i) PWV time series are dominated by the seasonal cycle with maximum values during summer months, (ii) the comparison between GPS and ERA-Interim PWV monthly data shows good agreement with differences less than 4 mm, (iii) at all stations and for almost all months, PWV is only poorly correlated with recorded precipitation and the SPI, while PE correlates highly with the SPI, providing an estimate of the water availability at a given location and useful information on wet/dry spell occurrence, and (iv) long data records would allow, for each month of the year, the identification of PE thresholds associated with different SPI classes that, in turn, have potential for forecasting meteorological wet/dry spells. Thus, it is through PE that ground-based GPS measurements appear of relevance for assessing wet/dry spells, although there is not a direct relationship between PWV and SPI.

  8. Integrated water vapor from IGS ground-based GPS observations. Initial results from a global 5-min data set

    Energy Technology Data Exchange (ETDEWEB)

    Heise, S.; Dick, G.; Gendt, G.; Schmidt, T.; Wickert, J. [GFZ German Research Centre for Geosciences, Potsdam (Germany). Dept. 1 Geodesy and Remote Sensing

    2009-07-01

    Ground based GPS zenith path delay (ZPD) measurements are well established as a powerful tool for integrated water vapor (IWV) observation. The International GNSS Service (IGS) provides ZPD data of currently more than 300 globally distributed GPS stations. To derive IWV from these data, meteorological information (ground pressure and mean temperature above the station) are needed. Only a limited number of IGS stations is equipped with meteorological ground sensors up to now. Thus, meteorological data for IWV conversion are usually derived from nearby ground meteorological observations (ground pressure) and meteorological analyses (mean temperature). In this paper we demonstrate for the first time the applicability of ground pressure data from ECMWF meteorological analysis fields in this context. Beside simplified data handling (no single station data and quality control) this approach allows for IWV derivation if nearby meteorological stations are not available. Using ECMWF ground pressure and mean temperature data the new IGS 5-min ZPD data set has been converted to IWV for the first time. We present initial results from selected stations with ground meteorological sensors including pressure and temperature comparisons between ECMWF and local measurements. The GPS IWV is generally validated by comparison with ECMWF IWV. The ECMWF derived station meteorological data are compared with local measurements at all accordingly equipped stations. Based on this comparison, the mean error (in terms of standard deviation) introduced by time interpolation of the 6-hourly ECMWF data is estimated below 0.2 mm IWV. (orig.)

  9. Data assimilation of plasmasphere and upper ionosphere using COSMIC/GPS slant TEC measurements

    Science.gov (United States)

    Wu, M. J.; Guo, P.; Xu, T. L.; Fu, N. F.; Xu, X. S.; Jin, H. L.; Hu, X. G.

    2015-11-01

    Increasing total electron content (TEC) measurements from the low Earth orbiting satellites to Global Positioning System satellites flourish the exploration of the ionosphere and plasmasphere for decades. This paper indicates a method that 3-D Var is applied to assimilate precise orbit determination antenna TEC measurements of Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites into the background global core plasma model (GCPM). The slant TEC data archived in the COSMIC Data Analysis and Archive Center from 500 km to 20,200 km are used to reconstruct a new electron density model. This model has a temporal resolution of 2 h and spatial resolutions of 2.5° in geomagnetic latitude, 5° in longitude, 50 km in the upper ionosphere, and several hundred kilometers in the plasmasphere. Preliminary results show that the data assimilation modifies the initial GCPM forecast to be better coincident with actual COSMIC measurements in internal quality check. Furthermore, independent validation with upper ionosphere-retrieved electron density and TEC of global ionosphere maps implies a reasonable improvement in the estimation of plasmaspheric electron density after the assimilation.

  10. Open-loop GPS signal tracking at low elevation angles from a ground-based observation site

    Science.gov (United States)

    Beyerle, Georg; Zus, Florian

    2016-04-01

    For more than a decade space-based global navigation satellite system (GNSS) radio occultation (RO) observations are used by meteorological services world-wide for their numerical weather prediction models. In addition, climate studies increasingly rely on validated GNSS-RO data sets of atmospheric parameters. GNSS-RO profiles typically cover an altitude range from the boundary layer up to the upper stratosphere; their highest accuracy and precision, however, are attained at the tropopause level. In the lower troposphere, multipath ray propagation tend to induce signal amplitude and frequency fluctuations which lead to the development and implementation of open-loop signal tracking methods in GNSS-RO receiver firmwares. In open-loop mode the feed-back values for the carrier tracking loop are derived not from measured data, but from a Doppler frequency model which usually is extracted from an atmospheric climatology. In order to ensure that this receiver-internal parameter set, does not bias the carrier phase path observables, dual-channel open-loop GNSS-RO signal tracking was suggested. Following this proposal the ground-based "GLESER" (GPS low-elevation setting event recorder) campaign was established. Its objective was to disproof the existence of model-induced frequency biases using ground-based GPS observations at very low elevation angles. Between January and December 2014 about 2600 validated setting events, starting at geometric elevation angles of +2° and extending to -1°… - 1.5°, were recorded by the single frequency "OpenGPS" GPS receiver at a measurement site located close to Potsdam, Germany (52.3808°N, 13.0642°E). The study is based on the assumption that these ground-based observations may be used as proxies for space-based RO measurements, even if the latter occur on a one order of magnitude faster temporal scale. The "GLESER" data analysis shows that the open-loop Doppler model has negligible influence on the derived frequency profile

  11. Three methods to retrieve slant total electron content measurements from ground-based GPS receivers and performance assessment

    Science.gov (United States)

    Zhang, Baocheng

    2016-07-01

    The high sampling rate along with the global coverage of ground-based receivers makes Global Positioning System (GPS) data particularly ideal for sensing the Earth's ionosphere. Retrieval of slant total electron content measurements (TECMs) constitutes a key first step toward extracting various ionospheric parameters from GPS data. Within the ionospheric community, the interpretation of TECM is widely recognized as the slant total electron content along the satellite receiver line of sight, biased by satellite and receiver differential code biases (DCBs). The Carrier-to-Code Leveling (CCL) has long been used as a geometry-free method for retrieving TECM, mainly because of its simplicity and effectiveness. In fact, however, the CCL has proven inaccurate as it may give rise to TECM very susceptible to so-called leveling errors. With the goal of attaining more accurate TECM retrieval, we report in this contribution two other methods than the CCL, namely, the Precise Point Positioning (PPP) and the Array-aided PPP (A-PPP). The PPP further exploits the International GPS Service (IGS) orbit and clock products and turns out to be a geometry-based method. The A-PPP is designed to retrieve TECM from an array of colocated receivers, taking advantage of the broadcast orbit and clock products. Moreover, A-PPP also takes into account the fact that the ionospheric effects measured from one satellite to all colocated receivers ought to be the same, thus leading to the estimability of interreceiver DCB. We perform a comparative study of the formal precision and the empirical accuracy of the TECM that are retrieved, respectively, by three methods from the same set of GPS data. Results of such a study can be used to assess the actual performance of the three methods. In addition, we check the temporal stability in A-PPP-derived interreceiver DCB estimates over time periods ranging from 1 to 3 days.

  12. Comparison of GPS-TEC variation during quiet and disturbed period using the Holt-Winter method and IRI-2012 model over Malaysia

    Science.gov (United States)

    Ahmed Ismail, Nouf Abd Emunim; Abdullah, Mardina; Hasbi, Alina Marie

    2016-07-01

    Total Electron Content (TEC) is the main parameter in the ionosphere that has significant effects on radio wave; it changes the speed and direction of the signal propagation, causing the delay of the Global Positioning System (GPS) signals. Therefore, it is crucial to validate the performance of the ionospheric model to reveal the variety of ionospheric behaviour during quiet and disturbed period. This research presents the performance evaluation of the statistical Holt-Winter method and IRI-2012 model using three topside electron density options: IRI-2001, IRI01-corr and NeQuick with the observed GPS-TEC during quiet and disturbed period. The GPS-TEC data were derived from the dual frequency GPS receiver at JUPEM (Department of Survey and Mapping Malaysia), from the UUMK station (north Peninsular Malaysia) at geographic coordinates of 6.46°N-100.50°E and geomagnetic coordinates of 3.32°S-172.99°E and TGPG station (south Peninsular Malaysia) at geographic coordinates of 1.36°N-104.10°E and geomagnetic coordinates of 8.43°S -176.53°E, during March of 2013. The maximum value of the GPS-TEC was at the post noon time at 17:00 LT and the minimum was in the early morning from 6:00-7:00 LT. During the quiet period, the maximum GPS-TEC at the UUMK station was 52 TECU while at the TGPG station, it was 60 TECU. During the disturbed period, when intense geomagnetic storm occurred on 17 March 2013, the maximum GPS-TEC recorded was 58 TECU and 65 TECU in UUMK and TGPG station, respectively. The diurnal hourly variation during the quiet period indicated that IRI-2001, IRI01-corr, and NeQuick had overestimation agreement during the day hours except for the time between 11:00-19:00 LT when IRI01-corr and NeQuick showed underestimation, while during 13:00-20:00 LT, IRI-2001 showed slight underestimation whereas the Holt-Winter method showed good agreement with GPS-TEC. During the disturbed period, IRI-2001 showed overestimation agreement for all hours, while the IRI01-corr

  13. Ionospheric GPS TEC Anomalies and M >= 5.9 Earthquakes in Indonesia during 1993 - 2002

    Directory of Open Access Journals (Sweden)

    Sarmoko Saroso

    2008-01-01

    Full Text Available Indonesia is one of the most seismically active regions in the world, containing numerous active volcanoes and subject to frequent earthquakes with epicenters distributed along the same regions as volcanoes. In this paper, a case study is carried out to investigate pre-earthquake ionospheric anomalies in total electron content (TEC during the Sulawesi earthquakes of 1993 - 2002, and the Sumatra-Andaman earthquake of 26 December 2004, the largest earthquake in the world since 1964. It is found that the ionospheric TECs remarkably decrease within 2 - 7 days before the earthquakes, and for the very powerful Sumatra-Andaman earthquake, the anomalies extend up to about 1600 km from the epicenter.

  14. Evaluating multimodel variability of humidity over Europe using long term GPS network and ground base datasets

    Science.gov (United States)

    Bastin, Sophie; Bock, Olivier; Parracho, Ana

    2016-04-01

    Thanks to efforts made to reanalyse observed data to produce long-term homogenized datasets of new parameters or multi-parameters in recent years, we can better characterize, evaluate and analyse the water cycle in models at different scales. In this paper, a few MED-CORDEX simulations covering the ERA-interim period are evaluated against reprocessed IWV from GPS datasets over the European domain, from 1995 to 2008. The humidity is an important component of the water cycle, and models often have difficulties representing it. The high quality, consistent, long-term IWV dataset recently produced from GPS at more than 100 stations over Europe, with about half of the stations having nearly 15 years of data over the period from 1995 to 2010 is therefore used to evaluate the simulated IWV at seasonal, interannual and possibly diurnal time scales. Regional features are then identified, corresponding to different climate regimes. Other datasets, such as reanalysis of multi-parameters observed at one site (SIRTA, Palaiseau, France) over more than 10 years, or more regional networks are used to explain the dispersion of IWV among the different models and their biases against observations. The relationship between IWV and surface temperature is also evaluated locally to assess how much the sources of humidity from advection or surface fluxes are enough to reach the total capacity of the atmosphere in humidity when temperature increases. Over arid areas, this relation can depart from the Clausius-Clapeyron relation when temperature becomes too high. The ability of models to reproduce this relation during present climate is of high importance to estimate future climate.

  15. Vertical profiling of atmospheric refractivity using GPS STD data from a single ground-based station: Simulations and applications

    Science.gov (United States)

    Zus, F.; Dick, G.; Heise, S.; Wickert, J.; Ramatschi, M.

    2013-12-01

    We developed a ray-tracing operator to compute the signal travel time delay due to the neutral atmosphere, known as Slant Total Delay (STD), between a GPS satellite and a ground-based receiving station. Having developed a rapid and precise forward operator we constructed the tangent-linear (adjoint) operator to estimate refractivity in the vicinity of a single station. The refractivity retrievals potentially complement refractivity retrievals from radio occultation data and can be considered a valuable input for Numerical Weather Prediction. In a first experiment (simulation) we study the feasibility for vertical profiling of refractivity using STDs from a single station. The simulation cycle consists of the computation of STDs given a refractivity profile, the addition of noise to mimic observation errors and the retrieval of a refractivity profile from the artificial STDs by a non-linear least-square analysis. Clearly, besides the noise level, the elevation range plays an important role regarding the quality of the refractivity retrieval; near-horizon STDs corrupted by noise allow a significantly better refractivity retrieval than STDs close to the zenith without any noise. The simulation study suggests that near-horizon STDs provide additional information when compared to Zenith Total Delays (ZTDs). In a second experiment (application) we replace the artificial STDs in the simulation by STDs retrieved from GPS phase-observations. The procedure is repeated station-by-station for 200 stations in Germany. We do not find a significant benefit from STDs over ZTDs in the retrieved refractivity profile since near-horizon STDs are rarely available and representative errors due to asymmetry are non-negligable. We attempt to mitigate the latter problem by the additional estimation of horizontal gradients, and indeed, we find strong evidence that STDs retrieved from GPS phase-observations contain asymmetric information. The former problem still poses a serious limitation

  16. PW Characteristics during the 2013 Colorado Flood using Ground-Based GPS Measurements

    Science.gov (United States)

    Huelsing, H. K.; Wang, J.

    2016-12-01

    During September 9-16, 2013, the Front Range region of Colorado experienced heavy rainfall that resulted in severe flooding. Precipitation totals for the event exceeded 450mm, damages to public and private properties were estimated to be over $2 billion, and 9 lives were lost. This study analyzes the characteristics of precipitable water (PW) surrounding the event using 10-years of high-resolution GPS PW data in Boulder, Colorado, which was located within the region of maximum rainfall. The characteristics examined include the temporal variability and abnormality of PW as well as the sources of moisture for the event. The temporal variability for PW in Boulder is dominated by seasonal variability with an average summertime maximum of 36mm. In 2013, the seasonal PW maximum extended into early September due to the occurrence of the flooding event. A closer examination of the temporal variability of PW surrounding this event showed that PW rapidly increased from 22mm to 32mm over the course of 1 day and values remained around 30mm for the entire event. When examining the abnormality of PW during the event, the atmosphere over Boulder was found to be near to saturation for the duration of the event and the monthly-averaged PW for September of 2013 was 25% higher than the long-term climatology. Also, the frequency distribution of September PW for Boulder is typically Gaussian, or normal, but in 2013 the distribution for September was bimodal, representing a shift in atmospheric conditions from climatology. This shift was the result of large-scale moisture transport into Colorado from the eastern tropical Pacific and the Gulf of Mexico. This moisture transport was the product of a stagnating, cutoff low over the southwestern United States working in conjunction with an anticyclone located over the southeastern United States. A blocking ridge located over the Canadian Rocky Mountains kept both of the synoptic features in place over the course of several days, which helped

  17. Characterisation of GPS-TEC in the African equatorial and low latitude region and the regional evaluation of the IRI model

    Science.gov (United States)

    Adebiyi, S. J.; Adimula, I. A.; Oladipo, O. A.

    2016-06-01

    With the increasing application of Global Navigation Satellite System (GNSS) products and services, knowledge of the Total Electron Content (TEC) variation is vital, particularly in historically under-sampled regions. The ionospheric induced-error, which is the largest and most variable error source of GNSS applications, is proportional to TEC along the satellite-receiver path. Simultaneous Global Positioning System (GPS) measurements from six African equatorial and low latitude stations in the southern hemisphere are used to investigate the latitudinal variation of TEC over the region during the year 2013, a year of moderate solar activity. The analysis reveals some detailed features of seasonal, month-to-month and solar activity dependence of TEC. The seasonal variation of TEC revealed that the daytime and the pre-midnight values of TEC for stations located close to the geographic equator is considerably higher in equinoxes and June solstice compared to stations farther from the equator, however, the difference is insignificant during the December solstice. The month-to-month variation of TEC shows semi-annual symmetry/asymmetry in TEC values for stations closer/farther from the equator. TEC sensitivity to solar activity shows significant seasonal and latitudinal characteristics. Generally, a relatively good correlation exists between TEC and F10.7 for stations around the Equatorial Ionization Anomaly (EIA) region compared to those found at stations close to the equator. Beyond the EIA region, the correlation coefficients drop in all seasons. TEC predicted by the three topside options of the International Reference Ionosphere (IRI) 2012 model [i.e. the NeQuick (NeQ), IRI-2001 Corrected (IRI-01 Corr) and the IRI-2001 (IRI-01) options] exhibits latitudinal and seasonal characteristics. The NeQ option performed better than the other two options at stations located within the equatorial region in most of the months and seasons. Outside the EIA region, the IRI-01 Corr

  18. Statistical characteristics of seismo-ionospheric GPS TEC disturbances prior to global Mw ≥ 5.0 earthquakes (1998-2014)

    Science.gov (United States)

    Shah, Munawar; Jin, Shuanggen

    2015-12-01

    Pre-earthquake ionospheric anomalies are still challenging and unclear to obtain and understand, particularly for different earthquake magnitudes and focal depths as well as types of fault. In this paper, the seismo-ionospheric disturbances (SID) related to global earthquakes with 1492 Mw ≥ 5.0 from 1998 to 2014 are investigated using the total electron content (TEC) of GPS global ionosphere maps (GIM). Statistical analysis of 10-day TEC data before global Mw ≥ 5.0 earthquakes shows significant enhancement 5 days before an earthquake of Mw ≥ 6.0 at a 95% confidence level. Earthquakes with a focal depth of less than 60 km and Mw ≥ 6.0 are presumably the root of deviation in the ionospheric TEC because earthquake breeding zones have gigantic quantities of energy at shallower focal depths. Increased anomalous TEC is recorded in cumulative percentages beyond Mw = 5.5. Sharpness in cumulative percentages is evident in seismo-ionospheric disturbance prior to Mw ≥ 6.0 earthquakes. Seismo-ionospheric disturbances related to strike slip and thrust earthquakes are noticeable for magnitude Mw6.0-7.0 earthquakes. The relative values reveal high ratios (up to 2) and low ratios (up to -0.5) within 5 days prior to global earthquakes for positive and negative anomalies. The anomalous patterns in TEC related to earthquakes are possibly due to the coupling of high amounts of energy from earthquake breeding zones of higher magnitude and shallower focal depth.

  19. Assessment of Modeling Capability for Reproducing Storm Impacts on TEC

    Science.gov (United States)

    Shim, J. S.; Kuznetsova, M. M.; Rastaetter, L.; Bilitza, D.; Codrescu, M.; Coster, A. J.; Emery, B. A.; Foerster, M.; Foster, B.; Fuller-Rowell, T. J.; Huba, J. D.; Goncharenko, L. P.; Mannucci, A. J.; Namgaladze, A. A.; Pi, X.; Prokhorov, B. E.; Ridley, A. J.; Scherliess, L.; Schunk, R. W.; Sojka, J. J.; Zhu, L.

    2014-12-01

    During geomagnetic storm, the energy transfer from solar wind to magnetosphere-ionosphere system adversely affects the communication and navigation systems. Quantifying storm impacts on TEC (Total Electron Content) and assessment of modeling capability of reproducing storm impacts on TEC are of importance to specifying and forecasting space weather. In order to quantify storm impacts on TEC, we considered several parameters: TEC changes compared to quiet time (the day before storm), TEC difference between 24-hour intervals, and maximum increase/decrease during the storm. We investigated the spatial and temporal variations of the parameters during the 2006 AGU storm event (14-15 Dec. 2006) using ground-based GPS TEC measurements in the selected 5 degree eight longitude sectors. The latitudinal variations were also studied in two longitude sectors among the eight sectors where data coverage is relatively better. We obtained modeled TEC from various ionosphere/thermosphere (IT) models. The parameters from the models were compared with each other and with the observed values. We quantified performance of the models in reproducing the TEC variations during the storm using skill scores. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

  20. Empirical model for mean temperature for Indian zone and estimation of precipitable water vapor from ground based GPS measurements

    Directory of Open Access Journals (Sweden)

    C. Suresh Raju

    2007-10-01

    Full Text Available Estimation of precipitable water (PW in the atmosphere from ground-based Global Positioning System (GPS essentially involves modeling the zenith hydrostatic delay (ZHD in terms of surface Pressure (Ps and subtracting it from the corresponding values of zenith tropospheric delay (ZTD to estimate the zenith wet (non-hydrostatic delay (ZWD. This further involves establishing an appropriate model connecting PW and ZWD, which in its simplest case assumed to be similar to that of ZHD. But when the temperature variations are large, for the accurate estimate of PW the variation of the proportionality constant connecting PW and ZWD is to be accounted. For this a water vapor weighted mean temperature (Tm has been defined by many investigations, which has to be modeled on a regional basis. For estimating PW over the Indian region from GPS data, a region specific model for Tm in terms of surface temperature (Ts is developed using the radiosonde measurements from eight India Meteorological Department (IMD stations spread over the sub-continent within a latitude range of 8.5°–32.6° N. Following a similar procedure Tm-based models are also evolved for each of these stations and the features of these site-specific models are compared with those of the region-specific model. Applicability of the region-specific and site-specific Tm-based models in retrieving PW from GPS data recorded at the IGS sites Bangalore and Hyderabad, is tested by comparing the retrieved values of PW with those estimated from the altitude profile of water vapor measured using radiosonde. The values of ZWD estimated at 00:00 UTC and 12:00 UTC are used to test the validity of the models by estimating the PW using the models and comparing it with those obtained from radiosonde data. The region specific Tm-based model is found to be in par with if not better than a

  1. Using the IRI, the MAGIC model, and the co-located ground-based GPS receivers to study ionospheric solar eclipse and storm signatures on July 22, 2009

    Science.gov (United States)

    Lin, Chi-Yen; Liu, Jann-Yenq; Lin, Chien-Hung; Sun, Yang-Yi; Araujo-Pradere, Eduardo A.; Kakinami, Yoshihiro

    2012-06-01

    The longest total solar eclipse in the 21st century occurred in Southeast Asia on 22 July 2009 from 00:55 to 04:15 UT, and was accompanied by a moderate magnetic storm starting at 03:00 UT with a D st reduction of -78 nT at 07:00 UT. In this study, we use the ionospheric reference model IRI, the data assimilation model MAGIC, and ground-based GPS receivers to simulate and examine the ionospheric solar eclipse and geomagnetic storm signatures in Taiwan and Japan. Cross-comparisons between the two model results and observations show that IRI fails to simulate the two signatures while MAGIC partially reproduces the storm features. It is essential to include ground-based GPS measurements to improve the IRI performance.

  2. Comparison of standard TEC models with a Neural Network based TEC model using multistation GPS TEC around the northern crest of Equatorial Ionization Anomaly in the Indian longitude sector during the low and moderate solar activity levels of the 24th solar cycle

    Science.gov (United States)

    Sur, D.; Paul, A.

    2013-09-01

    The highest Total Electron Content (TEC) values in the world normally occur at Equatorial Ionization Anomaly (EIA) region resulting in largest ionospheric range delay values observed for any potential Space Based Augmentation System (SBAS). Reliable forecasting of TEC is crucial for satellite based navigation systems. The day to day variability of the location of the anomaly peak and its intensity is very large. This imposes severe limitations on the applicability of commonly used ionospheric models to the low latitude regions. It is necessary to generate a mathematical ionospheric forecasting and mapping model for TEC based on physical ionospheric influencing parameters. A model, IRPE-TEC, has been developed based on real time low latitude total electron content data using GPS measurements from a number of stations situated around the northern crest of the EIA during 2007 through 2011 to predict the vertical TEC values during the low and moderate solar activity levels of the 24th solar cycle. This model is compared with standard ionospheric models like International Reference Ionosphere (IRI) and Parameterized Ionospheric Model (PIM) to establish its applicability in the equatorial region for accurate predictions.

  3. Quantitative Evaluation of Ionosphere Models for Reproducing Regional TEC During Geomagnetic Storms

    Science.gov (United States)

    Shim, J. S.; Kuznetsova, M.; Rastaetter, L.; Bilitza, D.; Codrescu, M.; Coster, A. J.; Emery, B.; Foster, B.; Fuller-Rowell, T. J.; Goncharenko, L. P.; Huba, J.; Mitchell, C. N.; Ridley, A. J.; Fedrizzi, M.; Scherliess, L.; Schunk, R. W.; Sojka, J. J.; Zhu, L.

    2015-12-01

    TEC (Total Electron Content) is one of the key parameters in description of the ionospheric variability that has influence on the accuracy of navigation and communication systems. To assess current TEC modeling capability of ionospheric models during geomagnetic storms and to establish a baseline against which future improvement can be compared, we quantified the ionospheric models' performance by comparing modeled vertical TEC values with ground-based GPS TEC measurements and Multi-Instrument Data Analysis System (MIDAS) TEC. The comparison focused on North America and Europe sectors during selected two storm events: 2006 AGU storm (14-15 Dec. 2006) and 2013 March storm (17-19 Mar. 2013). The ionospheric models used for this study range from empirical to physics-based, and physics-based data assimilation models. We investigated spatial and temporal variations of TEC during the storms. In addition, we considered several parameters to quantify storm impacts on TEC: TEC changes compared to quiet time, rate of TEC change, and maximum increase/decrease during the storms. In this presentation, we focus on preliminary results of the comparison of the models performance in reproducing the storm-time TEC variations using the parameters and skill scores. This study has been supported by the Community Coordinated Modeling Center (CCMC) at the Goddard Space Flight Center. Model outputs and observational data used for the study will be permanently posted at the CCMC website (http://ccmc.gsfc.nasa.gov) for the space science communities to use.

  4. Temporal and spatial variations in TEC using simultaneous measurements from the Indian GPS network of receivers during the low solar activity period of 2004–2005

    Directory of Open Access Journals (Sweden)

    D. S. V. V. D. Prasad

    2006-12-01

    Full Text Available With the recent increase in the satellite-based navigation applications, the ionospheric total electron content (TEC and the L-band scintillation measurements have gained significant importance. In this paper we present the temporal and spatial variations in TEC derived from the simultaneous and continuous measurements made, for the first time, using the Indian GPS network of 18 receivers located from the equator to the northern crest of the equatorial ionization anomaly (EIA region and beyond, covering a geomagnetic latitude range of 1° S to 24° N, using a 16-month period of data for the low sunspot activity (LSSA years of March 2004 to June 2005. The diurnal variation in TEC at the EIA region shows its steep increase and reaches its maximum value between 13:00 and 16:00 LT, while at the equator the peak is broad and occurs around 16:00 LT. A short-lived day minimum occurs between 05:00 to 06:00 LT at all the stations from the equator to the EIA crest region. Beyond the crest region the day maximum values decrease with the increase in latitude, while the day minimum in TEC is flat during most of the nighttime hours, i.e. from 22:00 to 06:00 LT, a feature similar to that observed in the mid-latitudes. Further, the diurnal variation in TEC show a minimum to maximum variation of about 5 to 50 TEC units, respectively, at the equator and about 5 to 90 TEC units at the EIA crest region, which correspond to range delay variations of about 1 to 8 m at the equator to about 1 to 15 m at the crest region, at the GPS L1 frequency of 1.575 GHz. The day-to-day variability is also significant at all the stations, particularly during the daytime hours, with maximum variations at the EIA crest regions. Further, similar variations are also noticed in the corresponding equatorial electrojet (EEJ strength, which is known to be one of the major contributors for the observed day-to-day variability in TEC. The seasonal variation in TEC maximizes during the equinox

  5. Altitudinal variation of midlatitude localized TEC enhancement from ground- and space-based measurements

    Science.gov (United States)

    Datta-Barua, S.; Mannucci, A. J.; Walter, T.; Enge, P.

    2008-10-01

    We present terrestrial and space-based dual-frequency observations of a region of enhanced total electron content (TEC) over the southeastern United States at local nighttime during the geomagnetic storm of 29-31 October 2003. The apparently localized, large-amplitude, and nearly Earth-fixed midlatitude ionosphere disturbance contained about 10 m higher delay at Global Positioning System (GPS) L1 frequency than the nighttime background ionosphere TEC. Using the dual-frequency altimeter on board the Jason satellite, we show evidence that nearly all of the electron content was below its orbital altitude of 1300 km at 0000 local time on 31 October 2003. Dual frequency GPS measurements from the receiver on board the SAC-C satellite indicate that some portion of the electron content existed above the 700 km orbit altitude of SAC-C. We develop a horizontally piecewise constant regional model of the enhancement. We compare the model prediction of TEC with the SAC-C satellite GPS data to constrain the altitude of this enhanced TEC region. Our model indicates that the peak density of the anomalous region is at slightly higher altitude and greater in amplitude than that of the background. The TEC enhancement provides a concrete case study of an extreme scenario that both space-based and ground-based GPS augmentation systems must take into account in order to offer high-accuracy, high-integrity corrections to GPS for safety-of-life applications.

  6. Monitoring Seasonal Variations of Ionospheric TEC Using GPS Measurements%利用GPS观测值监测电离层TEC的季节性变化

    Institute of Scientific and Technical Information of China (English)

    蔡昌盛

    2007-01-01

    The regional ionospheric model is adopted to determine satellite-plus-receiver differential delay. The satellite-plus-receiver differential delay is estimated as constant values for each day. Dual-frequency GPS pseudo-ranges observables are used to compute vertical TEC (VTEC). All the monthly mean VTEC profiles are represented by graphs using GPS data of the Beijing IGS site between 2000 and 2004. The monthly averaged values and amplitudes of VTEC are also represented by graphs. The results indicate that the VTEC has seasonal dependency. The monthly averaged values and amplitudes of VTEC in 2000 are about 2 times larger than that in 2004. The maximum VTEC values are observed in March and April, while the minimum VTEC values are observed in December. The seasonal variations trend is found to be similar after polynomial fitting between 2000 and 2004.

  7. A study of El Niño-Southern oscillation impacts to the South China Sea region using ground-based GPS receiver

    Science.gov (United States)

    Suparta, Wayan; Iskandar, Ahmad; Singh Jit Singh, Mandeep; Alauddin Mohd Ali, Mohd; Yatim, Baharudin; Tangang, Fredolin

    2013-04-01

    We observe an ENSO activity by using ground-based GPS receiver as an effort to study the effects of global warming and climate change in the tropical region. The precipitable water vapor (PWV) derived from Global Positioning System (GPS) meteorology in line with the sea surface temperature anomaly (SSTa) is used to indicate their response on ENSO activities. The PWV data used in this study was taken from the station at Universiti Malaysia Sabah, Kota Kinabalu (UMSK) over 2011, together with NTUS station (in the Singapore), PIMO (in Philippines) and BAKO (in Indonesia) are also compared. The relationship between PWV and SSTa at all stations on weekly basis exhibited modest with correlation coefficients between -0.30 and -0.78 significantly at the 99% confidence level. The negative correlation indicates that during a La Niña phase, the PWV is increased when the sea surface temperatures getting cold causes warm air mass in the central Pacific moved to west Pacific. The increased of PWV causes the GPS signals will be getting slower.

  8. Rapid Retrieval and Assimilation of Ground Based GPS-Met Observations at the NOAA Forecast Systems Laboratory: Impact on Weather Forecasts

    Science.gov (United States)

    Gutman, S.

    2003-04-01

    This year, 2003, marks the tenth anniversary of ground-based Global Positioning System meteorology. GPS-Met as we now know it started in 1992 with the definition of the essential techniques to retrieve integrated (total column) precipitable water vapor (IPW) from zenith-scaled neutral atmospheric signal delays (Bevis et al., 1992). It culminated with the GPS/Storm experiment in 1993, which demonstrated the ability to make IPW measurements with about the predicted accuracy under warm-weather conditions (Rocken et al., 1995). Since then, most of the major advances in GPS-Met data processing have been in the form of improved mapping functions (Niell, 1996), the estimation of GPS signal delays in an absolute (Duan et al., 1996) versus a relative sense (Rocken et al., 1993), and improved GPS satellite orbit accuracy with reduced latency (Fang et al., 1998). Experiments with other GPS-Met data processing techniques, such as the estimation of line-of-sight GPS signal delays using a double-difference to zero-difference technique described by Alber et al. (2000) and Braun et al. (2001) are noted, but lingering questions about the validity of this approach (Gutman, 2002), and not the potential value of a slant-path measurements per se, (as enumerated by MacDonald and Xie, 2001 or Ha et al., 2002) have thus far precluded its routine implementation at the National Oceanic and Atmospheric Administration Forecast Systems Laboratory (NOAA/FSL). Since 1994, NOAA/FSL has concentrated on evaluating the scientific and engineering bases of ground-based GPS-Met and assessing its utility for operational weather forecasting, climate monitoring, satellite calibration and validation, and improved differential GPS positioning and navigation. The term “rapid” in the title of this paper is defined as “available in time to be used for a specific application.” The requirement for high accuracy GPS-Met retrievals with lower latency is primarily driven by two factors: the trend toward

  9. Latitudinal variation in the occurrence of GPS L-band scintillations associated with the day-to-day changes in TEC, h′F and the E×B drift velocity and their impact on GPS satellite signals

    Indian Academy of Sciences (India)

    K Venkatesh; P V S Rama Rao; Gopi K Seemala; D S V V D Prasad

    2015-04-01

    The present study describes the day-to-day variations in the occurrence of GPS L-band scintillations from equator to the anomaly crest location associated with the changes in TEC, h′F and E×B drift velocities. The GPS–TEC and S4 index data from an equatorial station, Trivandrum (8.47°N, 76.91°E), a low latitude station, Waltair (17.7°N, 83.3°E) and an anomaly crest location Kolkata (22.6°N, 88.4°E) during the low solar activity years of 2004 and 2005 are used. It is observed that the day-time ambient TEC is higher during scintillation days compared to that during the days on which there are no scintillations at the three different locations mentioned above. Further, the diurnal variation of TEC shows a rapid decay during 1700–2000 hr LT over the three different locations during scintillation days which is observed to be comparatively much less during no scintillation days. The average height of the F-layer in the post-sunset hours over Trivandrum is found to be higher, around 350 km during scintillation days while it is around 260 km during the days on which there is no scintillation activity. The average pre-reversal E×B drift velocity observed around 19:00 hr LT is higher (20 m/s) during scintillation days, whereas during no scintillation days, it is found to be much less (7 m/s). Further, it is observed that the GPS receivers lose their locks whenever the S4 index exceeds 0.5 (>10 dB power level) and these loss of lock events are observed to be more around the anomaly crest location (Kolkata). It may be inferred from the present observations that the level of ambient ionization around noon-time, and a fast decay (collapse) of the ionization during afternoon hours followed by rapid increase in the height of the F-layer contributes significantly to the occurrence of scintillations. The present study further indicates that the S4 index at L-band frequencies increases with an increase in latitude maximizing around the crest of the equatorial ionization

  10. Assessment of the NeQuick Model at Mid-latitudes using GPS TEC and Ionosonde Data

    OpenAIRE

    2007-01-01

    The ionosphere plays a crucial role in GNSS accuracy. In extreme cases, this electrically charged part of the atmosphere can lead to errors in positioning exceeding 100m. At first approximation, the ionospheric effect depends on the frequency of the incident signal and on the total content in free electrons of the ionosphere (“total electron content”, TEC) which is the integral of the electron density on the path between the satellite and the receiver. The modelling of this parameter reve...

  11. A Ground-Based Near Infrared Camera Array System for UAV Auto-Landing in GPS-Denied Environment

    Directory of Open Access Journals (Sweden)

    Tao Yang

    2016-08-01

    Full Text Available This paper proposes a novel infrared camera array guidance system with capability to track and provide real time position and speed of a fixed-wing Unmanned air vehicle (UAV during a landing process. The system mainly include three novel parts: (1 Infrared camera array and near infrared laser lamp based cooperative long range optical imaging module; (2 Large scale outdoor camera array calibration module; and (3 Laser marker detection and 3D tracking module. Extensive automatic landing experiments with fixed-wing flight demonstrate that our infrared camera array system has the unique ability to guide the UAV landing safely and accurately in real time. Moreover, the measurement and control distance of our system is more than 1000 m. The experimental results also demonstrate that our system can be used for UAV automatic accurate landing in Global Position System (GPS-denied environments.

  12. A Ground-Based Near Infrared Camera Array System for UAV Auto-Landing in GPS-Denied Environment.

    Science.gov (United States)

    Yang, Tao; Li, Guangpo; Li, Jing; Zhang, Yanning; Zhang, Xiaoqiang; Zhang, Zhuoyue; Li, Zhi

    2016-08-30

    This paper proposes a novel infrared camera array guidance system with capability to track and provide real time position and speed of a fixed-wing Unmanned air vehicle (UAV) during a landing process. The system mainly include three novel parts: (1) Infrared camera array and near infrared laser lamp based cooperative long range optical imaging module; (2) Large scale outdoor camera array calibration module; and (3) Laser marker detection and 3D tracking module. Extensive automatic landing experiments with fixed-wing flight demonstrate that our infrared camera array system has the unique ability to guide the UAV landing safely and accurately in real time. Moreover, the measurement and control distance of our system is more than 1000 m. The experimental results also demonstrate that our system can be used for UAV automatic accurate landing in Global Position System (GPS)-denied environments.

  13. A Ground-Based Near Infrared Camera Array System for UAV Auto-Landing in GPS-Denied Environment

    Science.gov (United States)

    Yang, Tao; Li, Guangpo; Li, Jing; Zhang, Yanning; Zhang, Xiaoqiang; Zhang, Zhuoyue; Li, Zhi

    2016-01-01

    This paper proposes a novel infrared camera array guidance system with capability to track and provide real time position and speed of a fixed-wing Unmanned air vehicle (UAV) during a landing process. The system mainly include three novel parts: (1) Infrared camera array and near infrared laser lamp based cooperative long range optical imaging module; (2) Large scale outdoor camera array calibration module; and (3) Laser marker detection and 3D tracking module. Extensive automatic landing experiments with fixed-wing flight demonstrate that our infrared camera array system has the unique ability to guide the UAV landing safely and accurately in real time. Moreover, the measurement and control distance of our system is more than 1000 m. The experimental results also demonstrate that our system can be used for UAV automatic accurate landing in Global Position System (GPS)-denied environments. PMID:27589755

  14. Wavelet analysis of the ionospheric response at Mid-latitudes during the april 2000 storm using magnetograms and vTEC from GPS

    Directory of Open Access Journals (Sweden)

    L. I Fernández

    2012-12-01

    Full Text Available In this work we pursue the idea of computing a parameter that allows us to estimate the local ionospheric response to a geospheric event that triggers an ionospheric storm. For that, wavelet technique has been chosen because of its ability to analyze non-stationary signals. The advantage of the time-frequency analysis method called Wavelet Transform resides in providing information not only about the frequencies of the event but also about its location in the time series. Specifically, we compute the Scale Average Wavelet Power (SAWP of two parameters that describe the local geomagnetic field variation at the Earth surface caused by a geospheric storm and ionospheric response to the storm event. In particular, we propose the time delay between the maximum values of SAWP applied to the vTEC (vertical Total Electron Content and the horizontal component of the geomagnetic field (H variations as parameters to characterize the local behavior of the ionospheric storm. We applied the parameter to the geomagnetic and ionospheric disturbances caused by a coronal mass ejection (CME that took place on April 4, 2000. We used vTEC values computed from GPS observations and H at the surface of the Earth, measured in stations near to each GPS station chosen. The vTEC values used came from the GPS permanent stations belonging to the global IGS (International GNSS Service network. We chose stations located at magnetic mid-latitudes. Moreover, three-longitude bands representing the ionospheric behavior at different local times (LT were studied. Because the April 2000 storm has been extensively studied for many authors, the results are compared with those in the literature and we found a very good agreement as expected.En este trabajo perseguimos la idea de estimar un parámetro que nos permita calcular la respuesta ionosférica local a un evento geosférico desencadenante de una tormenta ionosférica. Para ello, se eligió la aplicación de la técnica ondeleta

  15. A global assessment of NASA AIRS v6 and EUMETSAT IASI v6 precipitable water vapor using ground-based GPS SuomiNet stations

    Science.gov (United States)

    Roman, Jacola; Knuteson, Robert; August, Thomas; Hultberg, Tim; Ackerman, Steve; Revercomb, Hank

    2016-08-01

    Satellite remote sensing of precipitable water vapor (PWV) is essential for monitoring moisture in real time for weather applications, as well as tracking the long-term changes in PWV for climate change trend detection. This study assesses the accuracies of the current satellite observing system, specifically the National Aeronautics and Space Administration (NASA) Atmospheric Infrared Sounder (AIRS) v6 PWV product and the European Organization for the Exploitation of Meteorological Satellite Studies (EUMETSAT) Infrared Atmospheric Sounding Interferometer (IASI) v6 PWV product, using ground-based SuomiNet Global Positioning System (GPS) network as truth. Elevation-corrected collocated matchups to each SuomiNet GPS station in North America and around the world were created, and results were broken down by station, ARM region, climate zone, and latitude zone. The greatest difference, exceeding 5%, between IASI and AIRS retrievals occurred in the tropics. Generally, IASI and AIRS fall within a 5% error in the PWV range of 20-40 mm (a mean bias less than 2 mm), with a wet bias for extremely low PWV values (less than 5 mm) and a dry bias for extremely high PWV values (greater than 50 mm). The operational IR satellite products are able to capture the mean PWV but degrade in the extreme dry and wet regimes.

  16. Estimating the contribution from different ionospheric regions to the TEC response to the solar flares using data from the international GPS network

    Directory of Open Access Journals (Sweden)

    L. A. Leonovich

    Full Text Available This paper proposes a new method for estimating the contribution from different ionospheric regions to the response of total electron content variations to the solar flare, based on data from the international network of two-frequency multichannel receivers of the navigation GPS system. The method uses the effect of partial "shadowing" of the atmosphere by the terrestrial globe. The study of the solar flare influence on the atmosphere uses GPS stations located near the boundary of the shadow on the ground in the nightside hemisphere. The beams between the satellite-borne transmitter and the receiver on the ground for these stations pass partially through the atmosphere lying in the region of total shadow, and partially through the illuminated atmosphere. The analysis of the ionospheric effect of a powerful solar flare of class X5.7/3B that was recorded on 14 July 2000 (10:24 UT, N22 W07 in quiet geomagnetic conditions (Dst = -10 nT has shown that about 75% of the TEC increase corresponds to the ionospheric region lying below 300 km and about 25% to regions lying above 300 km.

    Key words. Ionosphere (solar radiation and cosmic ray effects; instruments and techniques – Solar physics, astrophysics and astronomy (ultraviolet emissions

  17. 成都地区地基GPS观测网遥感大气可降水量的初步实验%Experiment on Driving Precipitable Water Vapor from Ground-Based GPS Network in Chengdu Plain

    Institute of Scientific and Technical Information of China (English)

    李国平; 黄丁发; 刘碧全; 陈娇娜

    2007-01-01

    The estimates of total zenith delay are derived using Bernese GPS Software V4. 2 based on GPS data every 30 s from the first measurement experiment of a ground-based GPS network in Chengdu Plain of Southwest China during the period from July to September 2004. Then the estimates of 0.5 hourly precipitable water vapor (PWV) derived from global positioning system (GPS) are obtained using meteorological data from automatic weather stations (AWS). The comparison of PWV derived from GPS and those from radiosonde observations is given for the Chengdu station, with RMS (root mean square)differences of 3.09m. The consistency of precipitabie water vapor derived from GPS to those from radiosonde is good. It is concluded that Bevis' empirical formula for estimating the weighted atmospheric mean temperature Can be applicable in Chengdu area because the relationship of GPS PWV with Bevis' formula and GPS PWV with radiosonde method shows a high correlation. The result of this GPS measurement experiment is helpful both for accumulating the study of precipitable water vapor derived from GPS in Chengdu areas located at the eastern side of the Tibetan Plateau and for studying spatial-temporal variations of regional atmospheric water vapor through many disciplines cooperatively.

  18. Moisture Analysis of a Squall Line Case Based on Precipitable Water Vapor Data from a Ground-Based GPS Network in the Yangtze River Delta

    Institute of Scientific and Technical Information of China (English)

    DING Jincai; YANG Yinming; YE Qixin; HUANG Yan; MA Xiaoxing; MA Leiming; Y.R.GUO

    2007-01-01

    A squall line swept eastward across the area of the Yangtze River Delta and produced gusty winds and heavy rain from the afternoon to the evening of 24 August 2002. In this paper, the roles of moisture in the genesis and development of the squall line were studied. Based on the precipitable water vapor (PWV) data from a ground-based GPS network over the Yangtze River Delta in China, plus data from a Pennsylvania State University/National Atmospheric Center (PSU/NCAR) mesoscale model (MM5) simulation, initialized by three-dimensional variational (3D-VAR) assimilation of the PWV data, some interesting features are revealed. During the 12 hours prior to the squall line arriving in the Shanghai area, a significant increase in PWV indicates a favorable moist environment for a squall line to develop. The vertical profile of the moisture illustrates that it mainly increased in the middle levels of the troposphere, and not at the surface. Temporal variation in PWV is a better precursor for squall line development than other surface meteorological parameters. The characteristics of the horizontal distribution of PWV not only indicated a favorable moist environment, but also evolved a cyclonic wind field for a squall line genesis and development. The "+2 mm" contours of the three-hourly PWV variation can be used successfully to predict the location of the squall line two hours later.

  19. Impact of Ionization DEPLETIONS/TEC Bite-Outs of Equatorial Plasma Structures on Transionospheric Satellite Signals Using Global Positioning System (GPS)

    Science.gov (United States)

    Das, Tanmay

    2016-07-01

    This paper represents the impact of ionization depletions/TEC bite-outs of equatorial plasma structures on transionospheric satellite signals received from Calcutta (latitude: 22.58oN, longitude: 88.38oE geographic; 32oN magnetic dip) is situated near the northern crest of the equatorial ionization anomaly (EIA) in the Indian longitude sector, using Global Positioning System (GPS) during the equinoctial months of February-April 2011, August-October, 2011 and February-April 2012. It is observed that when a bubble moves across a satellite link, scintillations and ionization are usually encountered. The apparent duration of the bite-outs may be different from the true east-west duration, as observed with geostationary links, because of the presence of a relative velocity between the irregularity cloud and the satellite. The trajectory of a GPS satellite plays a vital role in observing the bubble characteristics. The distributions of amplitude and the parameters characterizing the ionization depletions, namely, the duration, depth and the leading and trailing edge slopes of the bubbles have been obtained during the same equinoctial months of 2011 and 2012. It is evident that the range error, extent of the bubble and ionization gradients measured in these equinoctial months of the equatorial region provides the worst case figures for system designers. The high range error (~ 3-4 m) is observed during these equinoctial months. The statistical distribution of the TEC depletions showed some significant results. Out of 29 bite-outs in February-April, 2011 equinox, the maximum amplitude was found to be about 23.25 TECU with a median depletion of about 5.92 TECU. The maximum amplitude corresponds to a range error of about 3.7 m at GPS L1 frequency. The majority of the bubbles were found to have observed duration between 10-20 minutes with a maximum of 28.14 minutes. The median value of actual duration 2.37 minutes translates to nearly 150sec of possible satellite signal

  20. A robust TEC depletion detector algorithm for satellite based navigation in Indian zone and depletion analysis for GAGAN

    Science.gov (United States)

    Dashora, Nirvikar

    2012-07-01

    require an immediate solution to attack this problem. Hence, an alternative approach is chosen in which TEC-depletions are ignored for GIVE estimation. This approach requires further attention to accommodate it in the processing software for a near real time solution for the concerned user in Indian zone. But, nonetheless, as a prime concern, to precluding a particular satellite-link affected by TEC depletion, a reference receiver or user requires an algorithm that can compute the TEC and detect the depletion in TEC in near real time. To answer it, a novel TEC depletion detector algorithm and software has been developed which can be used for any SBAS in India. The algorithm is initially tested for recorded data from ground based dual frequency GPS receivers of GAGAN project. Data from 18-20 stations with 30 second sampling interval was obtained for year 2004 and 2005. The algorithm has been tuned to Indian ionosphere and show a great success in detecting TEC depletions with minimum false alarm. This is because of a specific property of this algorithm that it rejects the smooth fall in TEC in post sunset ionosphere. The depletions in TEC are characterized by a sudden fall and immediate recovery in level of TEC for a given line of sight. Since our algorithm extracts only such signatures and hence minimize the false alarms it may reduce burden on operational systems. We present this algorithm in detail. Another important facet of this algorithm is about its scientific use in automatic analysis of large amount of continuous GPS data. We have analyzed the aforementioned data by a MATLAB based script and obtained significant statistical results. The temporal duration and depth of TEC depletions is obtained for all over Indian region which provide a new insight over the phenomenon called EPBs and TEC depletions.

  1. Review and perspectives: Understanding natural-hazards-generated ionospheric perturbations using GPS measurements and coupled modeling

    Science.gov (United States)

    Komjathy, Attila; Yang, Yu-Ming; Meng, Xing; Verkhoglyadova, Olga; Mannucci, Anthony J.; Langley, Richard B.

    2016-07-01

    Natural hazards including earthquakes, volcanic eruptions, and tsunamis have been significant threats to humans throughout recorded history. Global navigation satellite systems (GNSS; including the Global Positioning System (GPS)) receivers have become primary sensors to measure signatures associated with natural hazards. These signatures typically include GPS-derived seismic deformation measurements, coseismic vertical displacements, and real-time GPS-derived ocean buoy positioning estimates. Another way to use GPS observables is to compute the ionospheric total electron content (TEC) to measure, model, and monitor postseismic ionospheric disturbances caused by, e.g., earthquakes, volcanic eruptions, and tsunamis. In this paper, we review research progress at the Jet Propulsion Laboratory and elsewhere using examples of ground-based and spaceborne observation of natural hazards that generated TEC perturbations. We present results for state-of-the-art imaging using ground-based and spaceborne ionospheric measurements and coupled atmosphere-ionosphere modeling of ionospheric TEC perturbations. We also report advancements and chart future directions in modeling and inversion techniques to estimate tsunami wave heights and ground surface displacements using TEC measurements and error estimates. Our initial retrievals strongly suggest that both ground-based and spaceborne GPS remote sensing techniques could play a critical role in detection and imaging of the upper atmosphere signatures of natural hazards including earthquakes and tsunamis. We found that combining ground-based and spaceborne measurements may be crucial in estimating critical geophysical parameters such as tsunami wave heights and ground surface displacements using TEC observations. The GNSS-based remote sensing of natural-hazard-induced ionospheric disturbances could be applied to and used in operational tsunami and earthquake early warning systems.

  2. A simplified traveling ionospheric disturbance (TID) specification model based on TID Detector Built In Texas (TIDDBIT) and GPS total electron content (TEC) measurements.

    Science.gov (United States)

    Duly, T. M.; Crowley, G.; Azeem, I.

    2015-12-01

    There is currently a great deal of interest in Traveling Ionospheric Disturbances (TIDs) from both an observational and modeling perspective, especially as they apply to operational systems that rely on nowcasting the ionospheric state. ASTRA has developed a new observational system to measure TID characteristics called TIDDBIT (TID Detector Built in Texas). TIDDBIT is a fully digital HF Doppler sounder that uses CW signals across a spaced array. TIDDBIT systems have been deployed in Texas, Virginia, Florida, Hawaii, and Peru. TIDDBIT measures the entire wave packet, including the horizontal and vertical phase propagation speeds as a function of TID period from the acoustic (1-min) to the gravity wave (10-90 min) part of the spectrum. It is desirable to be able to use these data to specify the TID structure not only at the measurement height, but to extend it in 3D to greater and lower heights, and beyond the immediate vicinity of the TIDDBIT system. We present a simplified model to specify TIDs based on the ion continuity equation for plasma density (Hooke 1970). Linearity of the neutral wind perturbations is assumed, and the different spectral components of the measured TID perturbations are added linearly. We use TID observations from the TIDDBIT sounder in Virginia and Peru as input into the model, and develop a 4D regional specification (spanning ~500 x 500 km in the horizontal direction and 90-1000 km altitude range) of both the perturbed electron density and the perturbed neutral wind from the corresponding atmospheric gravity wave (AGW). The model is also applied to TID measurements derived by GPS TEC measurements from the continental United States during the 11 March 2011 Tohoku Earthquake to study the theoretical launch angle of AGWs from the west coast of the United States.

  3. Latitudinal variations of TEC over Europe obtained from GPSobservations

    Directory of Open Access Journals (Sweden)

    P. Wielgosz

    2004-01-01

    Full Text Available GPS technique has opened broad possibilities to study the TEC distribution on a regular basis. In this paper, the latitudinal dependence of TEC over Europe for geographic latitudes ranging from 40°N to 75°N is presented. We discuss the day-to-day variations of the latitudinal TEC profiles for a period of 1999 to 2001 for both quiet and disturbed magnetic conditions. More than 4300 TEC profiles were created from the TEC maps with a one-hour interval. GPS data from 65 European permanent stations were used to produce the TEC maps. The comparison of GPS-derived TEC profiles with the IRI model is also discussed.

    Key words. Ionosphere (mid-latitude ionosphere; ionospheric disturbances

  4. Recent Progress in Understanding Natural-Hazards-Generated TEC Perturbations: Measurements and Modeling Results

    Science.gov (United States)

    Komjathy, A.; Yang, Y. M.; Meng, X.; Verkhoglyadova, O. P.; Mannucci, A. J.; Langley, R. B.

    2015-12-01

    Natural hazards, including earthquakes, volcanic eruptions, and tsunamis, have been significant threats to humans throughout recorded history. The Global Positioning System satellites have become primary sensors to measure signatures associated with such natural hazards. These signatures typically include GPS-derived seismic deformation measurements, co-seismic vertical displacements, and real-time GPS-derived ocean buoy positioning estimates. Another way to use GPS observables is to compute the ionospheric total electron content (TEC) to measure and monitor post-seismic ionospheric disturbances caused by earthquakes, volcanic eruptions, and tsunamis. Research at the University of New Brunswick (UNB) laid the foundations to model the three-dimensional ionosphere at NASA's Jet Propulsion Laboratory by ingesting ground- and space-based GPS measurements into the state-of-the-art Global Assimilative Ionosphere Modeling (GAIM) software. As an outcome of the UNB and NASA research, new and innovative GPS applications have been invented including the use of ionospheric measurements to detect tiny fluctuations in the GPS signals between the spacecraft and GPS receivers caused by natural hazards occurring on or near the Earth's surface.We will show examples for early detection of natural hazards generated ionospheric signatures using ground-based and space-borne GPS receivers. We will also discuss recent results from the U.S. Real-time Earthquake Analysis for Disaster Mitigation Network (READI) exercises utilizing our algorithms. By studying the propagation properties of ionospheric perturbations generated by natural hazards along with applying sophisticated first-principles physics-based modeling, we are on track to develop new technologies that can potentially save human lives and minimize property damage. It is also expected that ionospheric monitoring of TEC perturbations might become an integral part of existing natural hazards warning systems.

  5. Construction and Application about the Monitoring System of Water Vapor Derived from Ground-based GPS in Chengdu%成都地基的GPS水汽监测系统建设与应用

    Institute of Scientific and Technical Information of China (English)

    王皓; 李国平

    2011-01-01

    Water vapor plays a very important role in weather and climate changes. Though water vapor is very little in the atmosphere, but its change, in the atmosphere, is very obvious. Water vapor is also an important kind of greenhouse gas in the atmosphere whose spatial distribution is extremely uneven and time variation is very fast. It is not only the main driving force of weather and climate changes, but also an important formation and evolution reason for disastrous weather, especially medium or small scale disastrous weather. In satellite geodesy, GPS positioning accuracy was primarily affected by water vapor.Therefore, people learn from the elimination of noise in the measurement process, gradually to develop out of a new discipline—GPS meteorology (GPS/MET). Along with the development of GPS meteorology, people start to utilize ground-based GPS technology in order to effectively compensate for the defects of traditional detection technologies spatially and temporally and obtain water vapor information with high-precision, high-capacity and high space-time resolution ratio through ground-based GPS water vapor monitoring network. How to measure water vapor content in the atmosphere, to monitor the distribution of water vapor and its trends, which have an important practical significance to meteorological department, especially in monitoring and forecasting disastrous weather on a medium or small scale. The main content of this paper is to launch the development of ground-based GPS water vapor monitoring system;the purpose is to make this system fill in the blank of the application of GPS inversion water vapor technology in Sichuan and even the southwest areas of China, and also enhance the capacities of meteorological department on forecasting and monitoring of medium or small scale disastrous weather, as well as promote the work of many related meteorological operations.%水汽尽管在大气中的含量很少,但是其在大气中的变化却十分剧烈.其空

  6. Wenchuan earthquake ionosphere TEC anomaly detected by GPS%基于GPS探测汶川地震电离层TEC的异常

    Institute of Scientific and Technical Information of China (English)

    林剑; 吴云; 祝芙英; 乔学军; 周义炎

    2009-01-01

    利用球谐模型和中国地壳运动观测网络及IGS(International GNSS Service)基准站的GPS观测数据,分别计算了中国区域及全球电离层电子总含量(Total Electron Content,TEC),采用了不同的统计分析方法,对汶川震中上空及邻近区域的TEC进行检查.结果发现:震前后一个星期,孕震区上空连续出现电离层异常扰动,其异常形态具有共轭结构,且呈现向磁赤道漂移趋势.

  7. ERA-Interim应用于中国地区地基GPS/PWV计算的精度评估%Accuracy Assessment of Applying ERA-Interim Reanalysis Data to Calculate Ground-based GPS/PWV over China

    Institute of Scientific and Technical Information of China (English)

    赵静旸; 宋淑丽; 朱文耀

    2014-01-01

    由于中国绝大多数地基GPS网观测时未作气象观测,致使已积累的大量GPS观测数据无法在气象领域发挥作用.针对这一情况,研究和分析了利用ERA-Interim再分析产品获取中国地区气象资料和计算GPS/PWV的方法.以全国分布的24个气象观测站2006、2007年的气压、温度和相对湿度的实测资料为标准,评估了中国地区ERA-Interim再分析资料提取这三个参数和计算GPS/PWV所能达到的精度,并进行了精度评估.

  8. GNSS ionospheric scintillation and TEC at high latitudes: INGV monitoring and studies

    Science.gov (United States)

    Alfonsi, L.; de Franceschi, G.; Spogli, L.; Romano, V.

    2009-12-01

    The Istituto Nazionale di Geofisica e Vulcanologia (INGV) is monitoring the high latitude ionospheric irregularities causing GNSS signals corruption since 2003 when a GISTM receiver (GPS Ionospheric Scintillation and TEC Monitor) was deployed in Ny Alesund (Svalbard). Currently, INGV manages three GISTMs at Svalbard (two in Ny Alesund, another one in Longyearbyen) and two receivers in Antarctica at Concordia and Mario Zucchelli Stations. The GISTM receivers consist of NovAtel OEM4 dual-frequency receivers with special firmware specifically able to compute in near real time the amplitude and the phase scintillation from the GPS L1 frequency signals, and the ionospheric TEC (Total Electron Content) from the GPS L1 and L2 carrier phase signals. From this ground-based network, we are able to capture the dynamics of ionospheric plasma in a wide latitudinal range, from auroral to cusp/cap regions, considering the contribution of both hemispheres, in a bi-polar framework. The data collected are structured and archived in a dedicated database: www.eswua.ingv.it. The INGV activities in the field of the observation and the investigation of the ionospheric irregularities are included in several international collaborations addressing scientific issues as well as technological applications. This paper would like to give an overview of our recent activities about polar ionospheric imaging, scintillation climatology and scintillation mitigation matured also under the umbrella of the SCAR ICESTAR community and, currently, part of the initiatives of the SCAR Action Group “GPS Weather and Space Weather Forecast”chaired by INGV.

  9. 利用GPS TEC探测2015年尼泊尔地震激发的电离层扰动%Ionospheric Disturbances Triggered by 2015 Nepal Earthquake Detected by GPS TEC

    Institute of Scientific and Technical Information of China (English)

    李哲; 唐龙; 张小红

    2016-01-01

    利用尼泊尔周边区域6个IGS GPS跟踪站数据,对2015-04-25尼泊尔地震激发的电离层扰动进行分析.结果表明,地震发生后,尼泊尔上空电离层总电子含量(total electron content,TEC)存在不同频率的电离层扰动,扰动中心频率约为3 mHz和4 mHz.前者发生在震中附近1 000 km左右的范围,后者范围达2 000km,推断其分别为地震破裂产生的声重波信号以及瑞利波向上传播到电离层所激发的异常扰动信号.联合两个频率扰动信号,根据观测的扰动位置以及经验扰动速度反演震中位置,结果与实际情况符合较好.

  10. Towards the Implementation of GPS-based Tsunami Early Warning System Using Ionospheric Measurements

    Science.gov (United States)

    Yang, Y. M.; Komjathy, A.; Meng, X.; Verkhoglyadova, O. P.; Mannucci, A. J.

    2014-12-01

    Natural hazards and solid Earth events, such as earthquakes, tsunamis and volcanic eruptions are actual sources that may trigger acoustic and gravity waves resulting in traveling ionospheric disturbances (TIDs) in the upper atmosphere. Trans-ionospheric radio wave measurements sense the total electron content (TEC) along the signal propagation path. In this research, we introduce a novel GPS-based detection and estimation technique for remote sensing of atmospheric wave-induced TIDs including space weather phenomena induced by major natural hazard events, using TEC time series collected from worldwide ground-based dual-frequency GNSS receiver networks. We will demonstrate the ability of using ground-based dual-frequency GPS measures to detect and monitor tsunami wave propagations from previous great earthquake and tsunami events including: 2011 Tohoku and 2010 Chile earthquakes and tsunamis. Two major TIDs with different propagation speeds and wavelengths were identified through analysis of the GPS remote sensing observations. Dominant physical characteristics of atmospheric wave-induced TIDs are found to be associated with specific tsunami propagations and oceanic Rayleigh waves. We compared GPS-based observations, corresponding model simulations and other geophysical measurements. Our results lead to a better understanding of the tsunami-induced ionosphere responses. In addition, we investigate ionospheric signatures caused by the 1964 Great Alaska Earthquake and tsunami using the GPS-based method. Based on current distribution of Plate Boundary Observatory (PBO) GPS stations, the simulated results indicate that tsunami-induced TIDs may be detected about 60 minutes prior to tsunamis arriving at the US west coast. It is expected that this GPS-based technology becomes an integral part of future early-warning systems.

  11. Traveling Wave Packets of Total Electron Content Disturbances As Deduced From Global GPS Network Data

    Science.gov (United States)

    Afraimovich, E.; Lesyuta, O.; Lipko, Yu.; Perevalova, N.; Voyeikov, S.; Vodyannikov, V.; Yakovets, A.; Jacobi, Ch.

    This report discusses the experimental research results on the morphology and physi- cal origin of total electron content (TEC) pulsations as measured using the data from the global GPS network. Periodic electron density oscillations of the type of wave packets were investigated previously in terms of the hypothesis of their association with geomagnetic field (GP) pulsations. The greater part of evidence of the association between GP ad periodic electron density oscillations in the ionosphere was obtained by recording the frequency Doppler shift if the ionosphere-reflected radio signal and TEC variations measured using signals from geostationary satellites. However, many years of investigations have not yet provided thorough insight into the mechanisms ac- counting for the linkage between GP and ionospheric variations. One reason for that is the difficulty associated with obtaining statistically significant sets of experimental data. The use of the international ground-based network of two-frequency receivers of the navigation GPS system which comprised no less than 900 site as of August 2001 and is currently placing the data on the Internet, opens up a new era of a global, con- tinuous and fully computerized monitoring of ionospheric disturbances of a different class. This report presents a global morphology of TEC pulsations for 50 days with a different level of geomagnetic activity and the number of stations of the global GPS network from 100 to 300. A total number of the "receiver - GPS satellites" radio paths used in the analysis is about 500,000. Quasi-periodic TEC variations in the range of periods from 10 to 20 min are investigated, which is dictated by the fact that the data from the global GPS network are placed on the Internet with a standard temporal res- olution of 30 s. Most often, the observed TEC pulsations represent wave packets with a duration on the order of 1 hour. It was found that such TEC pulsations are a rela- tively rare event and are

  12. Investigation of ionospheric TEC over China based on GNSS data

    Science.gov (United States)

    Xiong, Bo; Wan, Weixing; Yu, You; Hu, Lianhuan

    2016-09-01

    In this paper, the ionospheric total electron content (TEC) is derived from 250 Global Navigation Satellite Systems (GNSS) receivers over China. The GNSS TEC data are utilized to study the diurnal and day-to-day variability of ionosphere, ionospheric east-west differences and to construct regional ionospheric map. The GNSS-TEC curves clearly show sunrise and sunset enhancements in the diurnal variation. The peak value of TEC is lower in January 2015 than in May 2014. There is 2 h difference in the occurrence time of TEC maximum/minimum between May and January. Compared with the observations of Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS), the measurements from the Geostationary Earth Orbit (GEO) satellites of BeiDou Navigation Satellite System (BDS) clearly present the ionospheric day-to-day variability and east-west differences in a region with small longitude differences (3.52-11.31°). The east-west differences in TEC are more obvious in larger longitude differences at 11:30 local time on 23 January 2015. The maximum east-west difference in TEC is about 7 total electron content unit (TECU, 1 TECU = 1016 el m-2) in longitude difference of 11.31°. Our analysis shows that the TEC for east-west small longitude differences may be associated with the east-west gradient of geomagnetic declination. Based on 250 GNSS stations, a regional TEC map constructed by Kriging method can well capture the main spatial structure of ionosphere in China. A comparison between TEC maps obtained by Kriging method and provided by Jet Propulsion Laboratory displays that there are large deviations in the North of China, which is mainly caused by the difference in the number of used GNSS stations. In addition, comprehensive investigation presents that GNSS has more advantages over GPS and GLONASS in the ionosphere research over China.

  13. Research of remote sensing technology of atmospheric water vapor by using ground-based GPS and application system of meteorological operations%地基GPS水汽监测技术及气象业务化应用系统的研究

    Institute of Scientific and Technical Information of China (English)

    李国平

    2011-01-01

    本研究建立了川渝地区地基GPS(global positioning system,全球定位系统)遥感水汽的本地化计算模型,开发出GPS遥感水汽的计算软件包,开展了局域地基GPS观测网遥感大气水汽的试验及业务应用,反演出30 min间隔的高时间分辨率GPS可降水量序列。评估了反演精度,研究了GPS水汽产品在气象业务应用的可行性。研发了可搭建在MICAPS(meteorological information comprehensive analysis and process system)平台上的地基G%This study established local computing model of remote sensing water vapor by using ground-based GPS(global positioning system) in the region of Sichuan-Chongqing,and developed computing software packages of GPS remote sensing water vapor.Then the experiment and operational application of remote sensing water vapor by using ground-based GPS in this local network was done,by which the high time resolution GPS precipitable water vapor(PWV) sequence of 30 min intervals was derived.This paper also gives the assessment of the retrieval accuracy,as well as the feasibility of meteorological operations application of GPS water vapor products.The major results of this study include developing the operations application system of remote sensing atmospheric water vapor by using ground-based GPS,which can be build on the MICAPS(meteorological information comprehensive analysis and process system) as an operational application system,and realizing the real-time transmission,data solution,deriving of PWV by a local ground-based GPS network and visualization of GPS water vapor products.This meteorological operations system played a unique role in the heavy rain,blizzard and other severe weather forecast in its trial-run.Systematical study of the temporal variation,horizontal distribution of GPS-PWV was done by our research group.Furthermore,the relationship between PWV derived by GPS among surface air temperature,pressure,specific humidity,solar radiation

  14. Application of Kalman filter in detecting pre-earthquake ionospheric TEC anomaly

    Directory of Open Access Journals (Sweden)

    Zhu Fuying

    2011-05-01

    Full Text Available : As an attempt, the Kalman filter was used to study the anomalous variations of ionospheric Total Electron Content (TEC before and after Wenchuan Ms8.0 earthquake, these TEC data were calculated from the GPS data observed by the Crustal Movement Observation Network of China. The result indicates that this method is reasonable and reliable in detecting TEC anomalies associated with large earthquakes.

  15. The new IGS ionospheric product - TEC fluctuation maps and their scientific application

    Science.gov (United States)

    Krankowski, Andrzej; Cherniak, Iurii; Zakharenkova, Irina

    2017-04-01

    The GPS signals fading due to presence of the plasma irregularities in the ionosphere can decrease an operational availability of navigation systems. This effect can be estimated by measuring its impact on phase of the received GPS signal. The new IGS ionospheric fluctuation maps product is based on estimates of the TEC rapid changes. For an overall representation of the spatial evolution of the ionospheric irregularities, which caused the GPS signal fluctuations over the Northern Hemisphere in middle and high latitudes, a daily map of the ROTI index is produced basing on data derived from a representative set of 700 permanent GPS stations. We use the corrected geomagnetic (CGM) coordinates with DGRF/IGRF models. For daily ROTI maps, we averaged and binned all ROTI values collected during 00-24 UT period of a considered day. The grid size is 8 min MLT by 2° MLAT, with the latter covering 50° - 90°. The averaged ROTI value in each MLAT-MLT bin corresponds to probability of the GPS signals phase fluctuations caused by passing of radio signals through the ionospheric irregularities. The resulted ionospheric fluctuation product is represented in the ASCII IONEX-like data format and can be visualized. This data format is described in details. We demonstrate the IGS ionospheric fluctuation map product performance for scientific research application on set of test-cases (geomagnetic storms occurred in the years 2013-2015) for comparative analysis of the resulted daily ROTI maps for quiet and geomagnetically disturbed periods. The intense phase scintillations depicted in the diurnal ROTI maps can provide an important information about development of the severe storm-induced gradients in the ionospheric plasma density, both caused by auroral particle precipitation and plasma flows. It is possible to conclude that IGS ionospheric fluctuation maps product can be effectively used for monitoring of the plasma irregularities with different origin. The independent ground-based

  16. Investigation of TEC variations over the magnetic equatorial and equatorial anomaly regions of the African sector

    Science.gov (United States)

    Oryema, B.; Jurua, E.; D'ujanga, F. M.; Ssebiyonga, N.

    2015-11-01

    This paper presents the annual, seasonal and diurnal variations in ionospheric TEC along the African equatorial region. The study also investigated the effects of a geomagnetic storm on ionospheric TEC values. Dual-frequency GPS derived TEC data obtained from four stations within the African equatorial region for the high solar activity year 2012 were used in this study. Annual variations showed TEC having two peaks in the equinoctial months, while minima values were observed in the summer and winter solstices. The diurnal pattern showed a pre-dawn minimum, a steady increase from about sunrise to an afternoon maximum and then a gradual fall after sunset to attain a minimum just before sunrise. Nighttime enhancements of TEC were observed mostly in the equinoctial months. There was comparably higher percentage TEC variability during nighttime than daytime and highest during equinoxes, moderate in winter and least during summer solstice. TEC was observed to exhibit a good correlation with geomagnetic storm indices.

  17. TEC enhancement immediately before M9 mega-thrust earthquakes

    Science.gov (United States)

    Heki, Kosuke

    2012-07-01

    Earthquakes are often preceded by electromagnetic precursors, e.g. electric currents in the ground and propagation anomalies of radio waves. By monitoring the differences of the L1 and L2 carrier phases from GPS satellites, we can infer ionospheric Total Electron Content (TEC). Here I report that positive anomalies of ionospheric TEC appeared immediately before the 2011 Tohoku-Oki (Mw9.0), 2010 Chile (Maule) (Mw8.8), 2007 Bengkulu (Mw8.6), and 2004 Sumatra-Andaman (Mw9.2) earthquakes. Coseismic vertical movements of the surface excite acoustic and internal gravity waves, causing coseismic ionospheric disturbances (CID), and GPS-TEC data showed that they occurred about ten minutes after these earthquakes. In addition to them, positive TEC anomalies were found to start 60-40 minutes before these earthquakes above the focal regions, and to last until the onsets of CID. In the Tohoku-Oki case, the anomaly was reached about one tenth of the background TEC immediately before the earthquake. TEC enhancements often occur irrespective of earthquakes, for example, sudden increase of TEC due to solar flares and large-scale traveling ionospheric disturbances (LSTID) propagating from the auroral oval to mid-latitude regions. These disturbances can be distinguished by carefully observing their spatial extents and movements. Geomagnetic activities were relatively high in the 2004 Sumatra-Andaman and 2011 Tohoku-Oki events, but were low in the 2007 Bengkulu and 2010 Chile events. For the Tohoku-Oki and the Bengkulu earthquakes, we analyzed the TEC time series of the same satellite and receiver pair over 120 days before and after the earthquakes, and confirmed that the precursory anomalies of the earthquakes were the largest in these periods. We also investigated three M8 class earthquakes, the 1994 Hokkaido-Toho-Oki (Mw8.3), 2006 Kuril (Mw8.2), and the 2003 Tokachi-Oki (Mw8.0) earthquakes. However, only weak precursory TEC anomalies were seen in the 1994 event, and not in the 2003

  18. The estimation of the ionosphere state over Mexico region based on TEC data

    Science.gov (United States)

    Sergeeva, Maria; Maltseva, Olga; Mejia-Ambriz, Julio-Cesar; Gonzalez-Esparza, Americo; De La Luz-Rodriguez, Victor Hugo; Romero-Hernández, Esmeralda

    2016-07-01

    In recent years, increasing interest toward Space Weather (SW) issues comes not only from researches but the general public as well because SW events can influence unfavorably all aspects of human life and technology. To prevent negative impacts the constant monitoring of the near-Earth space is required based on radio methods and with the help of satellites, magnetometers, all-sky imagers, other ground-based instruments, including Total Electron Content (TEC) studies and modeling. In October of 2014 the Mexican Space Weather Service (SCiESMEX) was established. The objectives of this new service include the study, analysis and forecast of changes in the ionosphere over the Mexican region (geographic latitudes 14º - 32º N, geomagnetic latitudes 23º - 38º N). From the beginning of September 2015 the continuous monitoring of TEC variations over Mexico is performed to monitor the Space Weather conditions. The traditional parameters describing these conditions in the ionosphere are the critical frequency of the F2-layer foF2 and its maximum height hmF2 measured by ground ionosondes. Since Mexico at the moment has no ionosonde in operation but has a rather dense network of GPS receivers the present paper discusses the possibility of evaluating the ionosphere state with use of the vertical total electron content (vTEC) reconstructed using the data of GPS receivers. To verify such prospect the comparison was made between the results for Mexico and for the adjacent regions having ionosondes. Three problems are being solved: (1) comparison of two options to obtain TEC values (global ionospheric maps and values from local receivers calculated on the base of software complex provided by Institute of Solar-Terrestrial Physics, Siberian Branch, Russian Academy of Sciences) based on daily and seasonal variations of monthly medians, (2) comparison of instantaneous values during disturbances, (3) determination of foF2 from observational values of TEC using the medians of the

  19. Latitudinal and Seasonal Investigations of Storm-Time TEC Variation

    Science.gov (United States)

    Adimula, I. A.; Oladipo, O. A.; Adebiyi, S. J.

    2016-07-01

    The ionosphere responds markedly and unpredictably to varying magnetospheric energy inputs caused by solar disturbances on the geospace. Knowledge of the impact of the space weather events on the ionosphere is important to assess the environmental effect on the operations of ground- and space-based technologies. Thus, global positioning system (GPS) measurements from the international GNSS service (IGS) database were used to investigate the ionospheric response to 56 geomagnetic storm events at six different latitudes comprising the northern and southern hemispheres in the Afro-European sector. Statistical distributions of total electron content (TEC) response show that during the main phase of the storms, enhancement of TEC is more pronounced in most of the seasons, regardless of the latitude and hemisphere. However, a strong seasonal dependence appears in the TEC response during the recovery phase. Depletion of TEC is majorly observed at the high latitude stations, and its appearance at lower latitudes is seasonally dependent. In summer hemisphere, the depletion of TEC is more pronounced in nearly all the latitudinal bands. In winter hemisphere, enhancement as well as depletion of TEC is observed over the high latitude, while enhancement is majorly observed over the mid and low latitudes. In equinoxes, the storm-time TEC distribution shows a fairly consistent characteristic with the summer distribution, particularly in the northern hemisphere.

  20. Ionospheric TEC Weather Map Over South America

    Science.gov (United States)

    Takahashi, H.; Wrasse, C. M.; Denardini, C. M.; Pádua, M. B.; de Paula, E. R.; Costa, S. M. A.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. Galera; Ivo, A.; Sant'Anna, N.

    2016-11-01

    Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Contínuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total 140 sites, have been used. TECMAPs with a time resolution of 10 min are produced in 12 h time delay. Spatial resolution of the map is rather low, varying between 50 and 500 km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1 TECU = 1016 el m-2 (TECU) 80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

  1. Reconstruction of the ionospheric 3D electron density distribution by assimilation of ionosonde measurements and operational TEC estimations

    Science.gov (United States)

    Gerzen, Tatjana; Wilken, Volker; Jakowski, Norbert; Hoque, Mainul M.

    2013-04-01

    New methods to generate maps of the F2 layer peak electron density of the ionosphere (NmF2) and to reconstruct the ionospheric 3D electron density distribution will be presented. For validation, reconstructed NmF2 maps will be compared with peak electron density measurements from independent ionosonde stations. The ionosphere is the ionized part of the upper Earth's atmosphere lying between about 50 km and 1000 km above the Earth's surface. From the applications perspective the electron density, Ne, is certainly one of the most important parameters of the ionosphere because of its strong impact on radio signal propagation. Especially the critical frequency, foF2, which is related to the F2 layer peak electron density, NmF2, according to the equation NmF2-m3 = 1.24 ? 1010(foF2-MHz)2 and builds the lower limit for the maximum usable frequency MUF, is of particular interest with regard to the HF radio communication applications. In a first order approximation the ionospheric delay of transionospheric radio waves of frequency f is proportional to 1-f2 and to the integral of the electron density (total electron content - TEC) along the ray path. Thus, the information about the total electron content along the receiver-to-satellite ray path can be obtained from the dual frequency measurements permanently transmitted by GNSS satellites. As data base for our reconstruction approaches we use the vertical sounding measurements of the ionosonde stations providing foF2 and routinely generated TEC maps in SWACI (http://swaciweb.dlr.de) at DLR Neustrelitz. The basic concept of our approach is the following one: To reconstruct NmF2 maps we assimilate the ionosonde data into the global Neustrelitz F2 layer Peak electron Density Model (NPDM) by means of a successive corrections method. The TEC maps are produced by assimilating actual ground based GPS measurements providing TEC into an operational version of Neustrelitz TEC Model (NTCM). Finally, the derived NmF2 and TEC maps in

  2. TEC variations over Europe during the solar eclipse of March 20, 2015 using GLONASS observations

    Science.gov (United States)

    Shagimuratov, Irk; Cherniak, Iurii; Krankowski, Andrzej; Zakharenkova, Irina; Yakimova, Galina; Tepenitzina, Nadezhda

    2016-07-01

    We report the features of the ionospheric TEC variations derived from the GLONASS measurements during the partial solar eclipse of March 20, 2015. Over Europe the maximal phase of the eclipse was observed around 10 UT. The eclipse took place during period when the ionosphere changed from night to day conditions. This eclipse occurred on the recovery phase of the strong geomagnetic storm of March 17, 2015. The effect of the eclipse was detected in diurnal variations of TEC over the individual GNSS stations as a trough-like variation with a gradual decrease and a succeeding increase of TEC at the time of the eclipse. The eclipse effect on the TEC distribution was observed more distinctly along individual satellite passes. Over the Kaliningrad GNSS station (54N, 20E) we registered the maximal TEC depression of about 4-6 TECU along several satellite passes. We should note that analysis of the ionospheric effects of the solar eclipse was complicated by the geomagnetic storm of March 17. The superposition of the storm and the eclipse make it difficult to separate the absolute TEC changes caused by the eclipse. At the same time the strong changes of the spatial structure of the TEC distribution were registered on the TEC maps. To analyze the spatial TEC distribution during the eclipse the TEC maps with high spatial-temporal resolution were produced. We used the GLONSS measurements derived from 150-180 stations of the dense European GNSS network. Dynamics of the ionospheric plasma density was analyzed using the mixture GLONASS-GPS TEC maps produced with 5 min sampling rate. The spatial structure of the ionosphere changed essentially during the eclipse comparing with the control days. The occurred TEC gradients were quite different comparing with previous and subsequent days. The complex pattern in the spatial-temporal TEC distribution highlights the important role of the dynamic processes in the ionosphere during the eclipse.

  3. 利用双频GPS观测量对高原地区(昆明)电离层TEC的研究%Study on Ionosphere TEC in Altiplano Zone(Kunming)by Double Frequency GPS Observation

    Institute of Scientific and Technical Information of China (English)

    朱勇; 杨忠祥

    2009-01-01

    采用双频GPS观测值,在顾及GPS系统硬件延迟情况下,通过伪距与载波相位观测值联合解出TEC,并将其投影至高原(昆明地区)上空约350kin的某一假想薄层上,从而导出接收站附近垂直TEC.这种方法得到的垂直TEC为天顶周围一锥角内的平均值,通过离散度的统计,并结合昆明站采集得到的高精度数据计算了该地区电离层2007年6~8月的电离层电子浓度总含量的逐日时间序列值,在此基础上对照昆明市连续运行参考站COILS描绘出了对于处在双驼峰区里该地区TEC日变化的特性.

  4. C/NOFS satellite observations of equatorial ionospheric plasma structures supported by multiple ground-based diagnostics in October 2008

    Science.gov (United States)

    Nishioka, M.; Basu, Su.; Basu, S.; Valladares, C. E.; Sheehan, R. E.; Roddy, P. A.; Groves, K. M.

    2011-10-01

    In early October 2008, the C/NOFS satellite orbited near the magnetic equator at its perigee altitude of ˜400 km at dusk in the Peruvian sector. This provided an ideal opportunity for a comparison, under the current very low solar flux condition, of equatorial ionospheric disturbances observed with the Communication/Navigation Outage Forecasting System (C/NOFS) in situ measurements and ground-based observations available near Jicamarca Observatory. The primary objective was the comparison of plasma density disturbances measured by a Planar Langmuir Probe (PLP) instrument on the C/NOFS satellite with VHF scintillation activity at Ancon near Jicamarca for this period. Here we discuss in detail two extreme cases: one in which severe in situ disturbances were accompanied by mild scintillation on a particular day, namely, 10 October while there was little in situ disturbance with strong scintillation on 5 October. This apparent contradiction was diagnosed further by a latitudinal ground-based GPS network at Peruvian longitudes, a Digisonde, and the incoherent scatter radar (ISR) at Jicamarca. The crucial distinction was provided by the behavior of the equatorial ionization anomaly (EIA). The EIA was well-developed on the day having severe in situ disturbances (10 Oct). This led to lower equatorial plasma density and total electron content (TEC) at the equator and consequently reduced the scintillations detected at Ancon. On the other hand, on the day with severe scintillations (5 Oct), the EIA was not so well developed as on 10 October, leading to relatively higher equatorial plasma density and TEC. Consequently the severe scintillations at Ancon were likely caused by ionospheric structure located below the altitude of C/NOFS. The NRL SAMI2 model was utilized to gain a greater understanding of the role of neutral winds and electric fields in reproducing the TEC as a function of latitude for both classes of irregularities. Spectral studies with high resolution in situ

  5. Ionospheric Disturbances Observed during Earthquakes and Solar Eclipses at Tashkent and Kitab GPS Stations

    Science.gov (United States)

    Ahmedov, Bobomurat

    2016-07-01

    Since the Global Positioning System (GPS) data can be used to measure the ionospheric TEC, the technique has received our attention as a potential tool to detect ionospheric perturbations related to the earthquakes and we mainly analysed GPS derived TEC disturbances from two GPS stations located in Tashkent and Kitab, for possible earthquake ionospheric precursors. This talk reports the ionospheric anomalies observed during strong local earthquakes (M greater than 5.0) which occurred mostly in and around Uzbekistan in seismically active zones, during years 2010 to 2015 within 1000 km from the observing GPS stations located in Tashkent and Kitab. The solar and geomagnetic conditions were quiet during occurrence of the selected more than 30 earthquakes. We produced TEC time series over both sites and apply them to detect anomalous TEC signals preceding or accompanying the earthquakes. The results show anomalous enhancements which are examined in the earthquakes. In general the anomalies occurred 1-6 days before the earthquakes as ionospheric electromagnetic precursors. To identify the anomalous values of TEC we calculated differential TEC (dTEC). dTEC is obtained by subtracting 15 days backward running mean of vTEC from the values of observed vTEC at each epoch. This procedure removes normal variations in TEC. For a detail study of the data, we have calculated dTEC values for all the months and examined the anomalous TEC variations before the earthquakes. A thorough analysis of the data shows abnormal variations in TEC and ionospheric anomalies, such as variations in the electron density few days before the earthquakes, may play a role of one of the electromagnetic precursory signals of earthquakes. TEC decrease during the solar eclipses is also obtained from data at GPS station in Tashkent and Kitab. During the solar flares occurrence the amplitude of TEC is amplified with compare to the nondisturbed initial monthly mean background value after the flare.

  6. Maps of Ionospheric F2-Layer Characteristics Derived from GPS Radio Occultation Observations

    Directory of Open Access Journals (Sweden)

    Lung-Chih Tsai

    2009-01-01

    Full Text Available The Global Positioning System (GPS radio occultation (RO technique has been used to receive multi-channel GPS carrier phase signals from low Earth or biting (LEO satellites and demon strate active limb sounding of the Earth¡¦s ionosphere. Apply ing Abel inversion through compen sated total electron content (TEC values, the GPS RO observations can obtainion o spheric electron density (ne profiles and then scale F2-layer characteristics including foF2 and hmF2, especially, hmF2 that can not be directly deduced from ionosonde observations. From the GPS/MET and FS3/COS MIC mis sions, we can col lect on average two hundred and eighteen hundred vertical neprofiles, respectively, within one day. The retrieved foF2 and hmF2 re sults have been used to produce numerical maps representing complex prop erties on a world-wide scale. This paperpresents aphysically appeal ing represen tation of foF2 and hmF2 medians based on GPS RO data. The derived numerical maps have also been examined by ground-based ionosonde data.

  7. GPS scintillations and total electron content climatology in the southern low, middle and high latitude regions

    Directory of Open Access Journals (Sweden)

    Luca Spogli

    2013-06-01

    Full Text Available In recent years, several groups have installed high-frequency sampling receivers in the southern middle and high latitude regions, to monitor ionospheric scintillations and the total electron content (TEC changes. Taking advantage of the archive of continuous and systematic observations of the ionosphere on L-band by means of signals from the Global Positioning System (GPS, we present the first attempt at ionospheric scintillation and TEC mapping from Latin America to Antarctica. The climatology of the area considered is derived through Ground-Based Scintillation Climatology, a method that can identify ionospheric sectors in which scintillations are more likely to occur. This study also introduces the novel ionospheric scintillation 'hot-spot' analysis. This analysis first identifies the crucial areas of the ionosphere in terms of enhanced probability of scintillation occurrence, and then it studies the seasonal variation of the main scintillation and TEC-related parameters. The results produced by this sophisticated analysis give significant indications of the spatial/ temporal recurrences of plasma irregularities, which contributes to the extending of current knowledge of the mechanisms that cause scintillations, and consequently to the development of efficient tools to forecast space-weather-related ionospheric events.

  8. Ionospheric TEC Estimations with the Signals of Various Geostationary Navigational Satellites

    Science.gov (United States)

    Kurbatov, G. A.; Padokhin, A. M.; Kunitsyn, V.; Yasyukevich, Y.

    2015-12-01

    The development of GNSS and SBAS systems provides the possibility to retrieve ionospheric TEC from the dual frequency observations from a number of geostationary satellites using the same approach as for dual frequency GPS/GLONASS observations. In this connection, the quality of geostationary data, first of all the level of noise in TEC estimations is of great interest and importance. In this work we present the results of the comparison of the noise patterns in TEC estimations using signals of geostationary satellites of augumentation systems - indian GAGAN, european EGNOS and american WAAS, as well as the signals of chinees COMPASS/Beidou navigational system. We show that among above mentioned systems geostationary COMPASS/Beidou satellites provide best noise level in TEC estimations (RMS~0.1TECU), which corresponds to those of GPS/GLONASS, while GAGAN and WAAS TEC RMS could reach up to 1.5 TECU with typical values of 0.25-0.5 TECU which is up to one order greater than for common GPS/GLONASS observations. EGNOS TEC estimations being even more noisy (TEC RMS up to 10TECU) than WAAS and GAGAN ones at present time are not suitable for ionospheric studies. We also present geostationary TEC response to increasing solar X-Ray and EUV ionizing radiation during several recent X-class flares. Good correlation was found between TEC and EUV flux for the stations at the sunlit hemisphere. We also present geostationary TEC response to geomagnetic field variations during strong and moderate geomagnetic storms (including G4 St. Patricks Day Storm of 2015) showing examples of both positive and negative TEC anomalies of order of tens of TECU during main storm phase. Our results show the capability of geostationary GNSS and SBAS observations for continuous monitoring of ionospheric TEC. Intensively growing networks of dedicated receivers (for example MGEX network) and increasing number of dual-frequency geostationary satellites in SBAS and GNSS constellations potentially make it a

  9. Latitudinal GRBR-TEC estimation in Southeast Asia region based on the two-station method

    Science.gov (United States)

    Watthanasangmechai, Kornyanat; Yamamoto, Mamoru; Saito, Akinori; Tsugawa, Takuya; Yokoyama, Tatsuhiro; Supnithi, Pornchai; Yatini, Clara Yono

    2014-10-01

    Total electron content (TEC) is an important parameter for revealing latitudinal ionospheric structures, such as the equatorial ionization anomaly (EIA) in Southeast Asia. Understanding the EIA is beneficial for studying equatorial spread F. To reveal the structures, the absolute TEC as a function of latitude must be accurately determined. In early 2012, we expanded a GNU Radio Beacon Receiver (GRBR) network to provide latitudinal coverage in the Thailand-Indonesia sector. We employed the GRBR network to receive VHF and UHF signals from polar low-Earth-orbit satellites. The TEC offset is an unknown parameter in the absolute TEC estimation process. We propose a new technique based on the two-station method to estimate the offset for the latitudinal TEC estimation, and it works better than the original method for a sparse network. The TEC estimation system requires two iterations to minimize the root-mean-square error (RMSE). Once the RMSE reaches the global minimum, the absolute TECs are estimated simultaneously over five GRBR stations. GPS-TECs from local stations are used as the initial guess of the offset estimation. The height of the ionospheric pierce point is determined from the ionosonde hmF2. As a result, the latitudinal GRBR-TEC was successfully estimated from the polar orbit satellites. The two EIA humps were clearly captured by the GRBR-TEC. The result was well verified with the TEC reconstructed from the C/NOFS density data and the ionosonde bottomside data. This is a significant step showing that the GRBR is a useful tool for the study of low-latitude ionospheric features.

  10. The estimation method of GPS instrumental biases

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A model of estimating the global positioning system (GPS) instrumental biases and the methods to calculate the relative instrumental biases of satellite and receiver are presented. The calculated results of GPS instrumental biases, the relative instrumental biases of satellite and receiver, and total electron content (TEC) are also shown. Finally, the stability of GPS instrumental biases as well as that of satellite and receiver instrumental biases are evaluated, indicating that they are very stable during a period of two months and a half.

  11. Study of TEC fluctuation via stochastic models and Bayesian inversion

    Science.gov (United States)

    Bires, A.; Roininen, L.; Damtie, B.; Nigussie, M.; Vanhamäki, H.

    2016-11-01

    We propose stochastic processes to be used to model the total electron content (TEC) observation. Based on this, we model the rate of change of TEC (ROT) variation during ionospheric quiet conditions with stationary processes. During ionospheric disturbed conditions, for example, when irregularity in ionospheric electron density distribution occurs, stationarity assumption over long time periods is no longer valid. In these cases, we make the parameter estimation for short time scales, during which we can assume stationarity. We show the relationship between the new method and commonly used TEC characterization parameters ROT and the ROT Index (ROTI). We construct our parametric model within the framework of Bayesian statistical inverse problems and hence give the solution as an a posteriori probability distribution. Bayesian framework allows us to model measurement errors systematically. Similarly, we mitigate variation of TEC due to factors which are not of ionospheric origin, like due to the motion of satellites relative to the receiver, by incorporating a priori knowledge in the Bayesian model. In practical computations, we draw the so-called maximum a posteriori estimates, which are our ROT and ROTI estimates, from the posterior distribution. Because the algorithm allows to estimate ROTI at each observation time, the estimator does not depend on the period of time for ROTI computation. We verify the method by analyzing TEC data recorded by GPS receiver located in Ethiopia (11.6°N, 37.4°E). The results indicate that the TEC fluctuations caused by the ionospheric irregularity can be effectively detected and quantified from the estimated ROT and ROTI values.

  12. Relationships between GPS-signal propagation errors and EISCAT observations

    Directory of Open Access Journals (Sweden)

    N. Jakowski

    Full Text Available When travelling through the ionosphere the signals of space-based radio navigation systems such as the Global Positioning System (GPS are subject to modifications in amplitude, phase and polarization. In particular, phase changes due to refraction lead to propagation errors of up to 50 m for single-frequency GPS users. If both the L1 and the L2 frequencies transmitted by the GPS satellites are measured, first-order range error contributions of the ionosphere can be determined and removed by difference methods. The ionospheric contribution is proportional to the total electron content (TEC along the ray path between satellite and receiver. Using about ten European GPS receiving stations of the International GPS Service for Geodynamics (IGS, the TEC over Europe is estimated within the geographic ranges -20°≤ λ ≤40°E and 32.5°≤ Φ ≤70°N in longitude and latitude, respectively. The derived TEC maps over Europe contribute to the study of horizontal coupling and transport proces- ses during significant ionospheric events. Due to their comprehensive information about the high-latitude ionosphere, EISCAT observations may help to study the influence of ionospheric phenomena upon propagation errors in GPS navigation systems. Since there are still some accuracy limiting problems to be solved in TEC determination using GPS, data comparison of TEC with vertical electron density profiles derived from EISCAT observations is valuable to enhance the accuracy of propagation-error estimations. This is evident both for absolute TEC calibration as well as for the conversion of ray-path-related observations to vertical TEC. The combination of EISCAT data and GPS-derived TEC data enables a better understanding of large-scale ionospheric processes.

  13. Regional TEC model under quiet geomagnetic conditions and low-to-moderate solar activity based on CODE GIMs

    Science.gov (United States)

    Feng, Jiandi; Jiang, Weiping; Wang, Zhengtao; Zhao, Zhenzhen; Nie, Linjuan

    2017-08-01

    Global empirical total electron content (TEC) models based on TEC maps effectively describe the average behavior of the ionosphere. However, the accuracy of these global models for a certain region may not be ideal. Due to the number and distribution of the International GNSS Service (IGS) stations, the accuracy of TEC maps is geographically different. The modeling database derived from the global TEC maps with different accuracy is likely one of the main reasons that limits the accuracy of the new models. Moreover, many anomalies in the ionosphere are geographic or geomagnetic dependent, and as such the accuracy of global models can deteriorate if these anomalies are not fully incorporated into the modeling approach. For regional models built in small areas, these influences on modeling are immensely weakened. Thus, the regional TEC models may better reflect the temporal and spatial variations of TEC. In our previous work (Feng et al., 2016), a regional TEC model TECM-NEC is proposed for northeast China. However, this model is only directed against the typical region of Mid-latitude Summer Nighttime Anomaly (MSNA) occurrence, which is meaningless in other regions without MSNA. Following the technique of TECM-NEC model, this study proposes another regional empirical TEC model for other regions in mid-latitudes. Taking a small area BeiJing-TianJin-Tangshan (JJT) region (37.5°-42.5° N, 115°-120° E) in China as an example, a regional empirical TEC model (TECM-JJT) is proposed using the TEC grid data from January 1, 1999 to June 30, 2015 provided by the Center for Orbit Determination in Europe (CODE) under quiet geomagnetic conditions. The TECM-JJT model fits the input CODE TEC data with a bias of 0.11TECU and a root mean square error of 3.26TECU. Result shows that the regional model TECM-JJT is consistent with CODE TEC data and GPS-TEC data.

  14. TEC variations and IRI-2012 performance at equatorial latitudes over Africa during low solar activity

    Science.gov (United States)

    Olawepo, A. O.; Adeniyi, J. O.; Oluwadare, E. J.

    2017-04-01

    GPS-TEC data obtained from Asmara (Geomag. Lat 11.42N, Long. 113.31E), Bahir Dar (Geomag. Lat. 8.04N, Long. 111.19E), and Eldoret (Geomag. Lat. 2.71S, Long. 107.30E), three stations in the equatorial region of the African sector, have been used to study the variations in the vertical total electron content (vTEC) and to investigate the performance of the three topside options in the IRI-2012 during the year 2010, a year of low solar activity (Rz = 16). The results revealed that TEC exhibits diurnal, seasonal and latitudinal characteristics. TEC values over the three stations are minimum during the sunrise hour of 0600LT and maximum around 1200LT-1500LT irrespective of the season. Daytime peak is followed by a steady decay in TEC which continues into the mid-night. TEC values during the equinoxes are observed to be greater than those of the solstices. TEC values during March equinox are higher than those of September equinox for the stations in the northern hemisphere. June solstices exhibit the lowest values for all the stations. For the station in the southern hemisphere, TEC values during December solstice values are slightly higher than those of September equinox. The three topside options in IRI-2012 reproduce the morphology of TEC at the three stations with correlation coefficient ranging between 0.97 and 0.99. The performance of NeQuick option at predicting TEC at these stations is observed to be the best compared to the other two options irrespective of the season.

  15. Temporal and spatial distributions of TEC depletions with scintillations and ROTI over south China

    Science.gov (United States)

    Deng, Baichang; Huang, Jiang; Kong, Debao; Xu, Jie; Wan, Dehuan; Lin, Guoguo

    2015-01-01

    This study investigated the temporal and spatial distributions of TEC depletions with scintillations and ROTI over south China. Data were collected from two GPS receiver stations in south China from 2011 to 2012. Our results revealed that maxima of distribution of TEC depletions were observed in vernal and autumnal equinox months. During pre-midnight hours and in the region of northern crest of equatorial anomaly, deep TEC depletions (approximately 20 TECU) well coincided with the occurrences of intense scintillations (S4 > 0.5) and large ROTI (approximately 2). But around midnight hours or at the outer edge of northern anomaly crest, only shallow TEC depletions (China could be considered as a representative of the evolution phase of the plasma bubbles during post-sunset hours.

  16. Validation of the TEC2F2 model over the African equatorial region

    Science.gov (United States)

    Ssessanga, Nicholas

    2016-06-01

    In this paper a statistical method, TEC2F2, of estimating critical F2 layer frequency (foF2) from Global Positioning System (GPS) Vertical Total Electron content (VTEC) is extended from Africa's mid-latitudes to the equatorial region, and the results validated. The equatorial region is one of the most dynamic yet under-represented over Africa in ionospheric studies. The TEC2F2 method was first considered for the South African region (mid-latitudes). This region is covered by a network of ionosondes that provided a validation platform for the TEC2F2 method before being applied to other parts of Africa. The results show that over the African equatorial region, the TEC2F2 method is a potential candidate in more accurately estimating the foF2 parameter than the most recent version of the International Reference Ionosphere (IRI-2012) model.

  17. Ground based materials science experiments

    Science.gov (United States)

    Meyer, M. B.; Johnston, J. C.; Glasgow, T. K.

    1988-01-01

    The facilities at the Microgravity Materials Science Laboratory (MMSL) at the Lewis Research Center, created to offer immediate and low-cost access to ground-based testing facilities for industrial, academic, and government researchers, are described. The equipment in the MMSL falls into three categories: (1) devices which emulate some aspect of low gravitational forces, (2) specialized capabilities for 1-g development and refinement of microgravity experiments, and (3) functional duplicates of flight hardware. Equipment diagrams are included.

  18. Ground based materials science experiments

    Science.gov (United States)

    Meyer, M. B.; Johnston, J. C.; Glasgow, T. K.

    1988-01-01

    The facilities at the Microgravity Materials Science Laboratory (MMSL) at the Lewis Research Center, created to offer immediate and low-cost access to ground-based testing facilities for industrial, academic, and government researchers, are described. The equipment in the MMSL falls into three categories: (1) devices which emulate some aspect of low gravitational forces, (2) specialized capabilities for 1-g development and refinement of microgravity experiments, and (3) functional duplicates of flight hardware. Equipment diagrams are included.

  19. Adult thymic epithelial cell (TEC) progenitors and TEC stem cells: Models and mechanisms for TEC development and maintenance.

    Science.gov (United States)

    Hamazaki, Yoko

    2015-11-01

    The thymus is the primary lymphoid organ for generating self-restricted and self-tolerant functional T cells. Its two distinct anatomical regions, the cortex and the medulla, are involved in positive and negative selection, respectively. Thymic epithelial cells (TECs) constitute the framework of this tissue and function as major stromal components. Extensive studies for more than a decade have revealed how TECs are generated during organogenesis; progenitors specific for medullary TECs (mTECs) and cortical TECs (cTECs) as well as bipotent progenitors for both lineages have been identified, and the signaling pathways required for the development and maturation of mTECs have been elucidated. However, little is known about the initial commitment of mTECs and cTECs during ontogeny, and how regeneration of both lineages is sustained in the postnatal/adult thymus. Recently, stem cell activities in TECs have been demonstrated, and TEC progenitors have been identified in the postnatal thymus. In this review, recent advances in studying the development and maintenance of TECs are summarized, and the possible mechanisms of thymic regeneration and involution are discussed.

  20. Seismo-Ionospheric Precursor in the GIM TEC of the 24 August 2014 M6 Napa Earthquake

    Science.gov (United States)

    Wu, T. Y.; Liu, T. J. Y.; Liu, J. Y.

    2015-12-01

    This study examines seismo-ionospheric precursors (SIPs) in the global ionosphere map (GIM) of the total electron content (TEC) associated with the 24 August 2014 M6 South Napa earthquake and statistical evidence of SIPs of the GPS TEC in western USA during 2000-2014. The temporal SIP in the GIM TEC around the epicenter significantly decreasing (negative anomaly) on 22 August. To discriminate the global effect, such as solar flares, magnetic storms, etc., and the local effect, such as earthquakes, 5183 lattices on the GIM are employed to conduct a global search of the SIP distribution. Anomalies of both GIM TEC and associated gradients specifically and continuously appearing over the epicenter suggest that the SIP relate to the 2014 South Napa earthquake. A simulation is further carried out to produce the SIP in GIM TEC before the earthquake. Results indicate that the eastward electric field generated over the epicenter area during the earthquake preparation period to be essential.

  1. The TEC Web-Umbrella

    NARCIS (Netherlands)

    Krom, J. G.; Korten, M.; Koslowski, H. R.; Kramer-Flecken, A.; Manduchi, G.; Niderost, B. U.; Oosterbeek, J. W.; Schorn, R. P.; Wijnoltz, F.; Becks, B.; Biel, W.; Evrard, M. P.; van Gorkom, J. C.; von Hellermann, M. G.

    2002-01-01

    The TEC community operates the TEXTOR device and in doing so collects and stores data from a number of different front-end acquisition systems, processing codes and analysis systems. Due to the evolution of these systems in the past, different, distributed data storage technologies were used to

  2. Precursory TEC enhancement immediately before the 2011 Tohoku-Oki earthquake

    Science.gov (United States)

    Heki, K.

    2011-12-01

    Earthquakes are often preceded by electromagnetic precursors, and we have been searching for them in, e.g. electric currents in the ground and propagation anomalies of radio waves. Here I report that a positive anomaly of ionospheric Total Electron Content (TEC) appeared immediately before the 2011 Tohoku-Oki earthquake (Mw9.0). Microwave signals from GPS satellites experience delays inversely proportional to the square of the frequency as they propagate through the ionosphere. By monitoring the differences of the L1 and L2 carrier phases with the dense GPS array, we can infer 2-D distribution of TEC above Japan. Coseismic vertical crustal movements excite acoustic waves, and they arrive at the ionosphere in ~10 minutes and cause coseismic ionospheric disturbances (CID). Raw TEC time series on March 11 show such CID in addition to slow background variations due to the changes in elevation and diurnal variation of vertical TEC (VTEC). We modeled the VTEC over the studied time window of ~5 hours with a cubic polynomial of time, and defined the departure from the model as TEC anomalies. Positive anomaly was found to start ~40 minutes before the earthquake in data of four GPS satellites 9, 15, 26, 27. The anomaly was larger at points closer to the epicenter, and reached ~1/10 of the background TEC immediately before the earthquake. The anomaly disappeared after the passage of CID. TEC increases often occur irrespective of earthquakes. For example, enhanced UV flux due to solar flares causes sudden increase of TEC. This, however, occurs on the whole sun-lit hemisphere, and never localizes above the focal region. Large-scale traveling ionospheric disturbances (LSTID) excited in the auroral oval often propagate southward and reach Japan. This can be distinguished by carefully observing their movements. I analyzed the TEC time series of satellite 15 observed at 93009 over 120 days from January to April, 2011. The precursory anomaly on March 11 showed the largest departure

  3. Preseismic TEC Changes for Tohoku-Oki Earthquake: Comparisons Between Simulations and Observations

    Directory of Open Access Journals (Sweden)

    Cheng-Ling Kuo

    2015-01-01

    Full Text Available Heki (2011 reported that the Japanese Global Positioning System (GPS dense network detected a precursory positive total electron content anomaly (TEC, with ΔTEC ~3 TECU, ~40 minutes before the Tohoku-Oki earthquake (Mw 9.0. Similar preseismic TEC anomalies were also observed in the 2010 Chile earthquake (Mw 8.8, 2004 Sumatra-Andaman (Mw 9.2 and the 1994 Hokkaido-Toho-Oki (Mw 8.3. In this paper we apply our improved lithosphere-atmosphere-ionosphere (LAI coupling model to compute the TEC variations and compare the simulation results with the reported TEC observations. For the Tohoku-Oki earthquake simulations we assumed that the stressed associated current started ~40 minutes before the earthquake, linearly increased and reached its maximum magnitude at the time of the earthquake main shock. It is suggested that a dynamo current density of ~25 nA m-2 is required to produce the observed ΔTEC ~3 TECU.

  4. TEC – Thin Environmental Cladding

    Directory of Open Access Journals (Sweden)

    Alan Tomasi

    2015-05-01

    Full Text Available Permasteelisa Group developed with Fiberline Composites a new curtain wall system (Thin Environmental Cladding or TEC, making use of pultruded GFRP (Glass Fiber Reinforced Polymer material instead of traditional aluminum. Main advantages using GFRP instead of aluminum are the increased thermal performance and the limited environmental impact. Selling point of the selected GFRP resin is the light transmission, which results in pultruded profiles that allow the visible light to pass through them, creating great aesthetical effects. However, GFRP components present also weaknesses, such as high acoustic transmittance (due to the reduced weight and anisotropy of the material, low stiffness if compared with aluminum (resulting in higher facade deflection and sensible fire behavior (as combustible material. This paper will describe the design of the TEC-facade, highlighting the functional role of glass within the facade concept with regards to its acoustic, structural, aesthetics and fire behavior.

  5. Geomagnetic storm effects on GPS based navigation

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2009-05-01

    Full Text Available The energetic events on the sun, solar wind and subsequent effects on the Earth's geomagnetic field and upper atmosphere (ionosphere comprise space weather. Modern navigation systems that use radio-wave signals, reflecting from or propagating through the ionosphere as a means of determining range or distance, are vulnerable to a variety of effects that can degrade the performance of the navigational systems. In particular, the Global Positioning System (GPS that uses a constellation of earth orbiting satellites are affected due to the space weather phenomena.

    Studies made during two successive geomagnetic storms that occurred during the period from 8 to 12 November 2004, have clearly revealed the adverse affects on the GPS range delay as inferred from the Total Electron Content (TEC measurements made from a chain of seven dual frequency GPS receivers installed in the Indian sector. Significant increases in TEC at the Equatorial Ionization anomaly crest region are observed, resulting in increased range delay during the periods of the storm activity. Further, the storm time rapid changes occurring in TEC resulted in a number of phase slips in the GPS signal compared to those on quiet days. These phase slips often result in the loss of lock of the GPS receivers, similar to those that occur during strong(>10 dB L-band scintillation events, adversely affecting the GPS based navigation.

  6. Study of the TEC data obtained from the DORIS stations in relation to seismic activity

    Directory of Open Access Journals (Sweden)

    M. Parrot

    2007-06-01

    Full Text Available Ionospheric data obtained from the DORIS system are used in this paper. The DORIS system is composed of several ground-based beacons which emit at two frequencies (400 MHz and 2 GHz and of receivers on board several satellites (currently SPOT2, SPOT4, SPOT5, Topex-Poseidon, Jason1 and Envisat. Thanks to the density of its network coverage (?50 stations, DORIS provides information on the ionosphere. The TEC (Total Electron Content parameter which is the electron density integrated over the vertical could be obtained from DORIS measurements. In a first step, the paper describes the way to obtain the TEC data from the DORIS ionospheric measurements, and comparisons of the results are done with the IRI2001 model. In a second step, TEC values are used to search for correlation between ionospheric perturbations and seismic activity. Earthquakes of magnitude larger than 5 are chosen close to the ground-based DORIS stations. Among other results, the statistics show that, during the night time and at geomagnetic latitude close to the equator (<10°, TEC amplitude fluctuates at the time of the earthquakes as it is expected, but also 2 days and 5 days before.

  7. Anomalous variations in ionospheric TEC prior to the 2011 Japan Ms9. 0 earthquake

    Directory of Open Access Journals (Sweden)

    Zhu Fuying

    2011-08-01

    Full Text Available The ionospheric total-electron-content (TEC data provided by the International GNSS Service (IGS network and the VTEC data from the GPS reference stations of Crustal Movement Observational Network of China(CMONC were processed and statistically analyzed to search for earthquake-related TEC anomalies prior to the 2011 magnitude 9.0 earthquake in Japan. Preliminary results showed that anomalous variations occurred 6 – 11 days and 0 – 4 days prior to the earthquake. After considering solar activity, geomagnetic conditions, and proximity in space and time to the earthquake, we tentatively concluded that the anomalous increase on March 5 may be related to the earthquake.

  8. Ionospheric Response to the Total Solar Eclipse of 22 July 2009 as Deduced from VLBI and GPS Data

    Science.gov (United States)

    Guo, L.; Shu, F. C.; Zheng, W. M.; Kondo, T.; Ichikawa, R.; Hasegawa, S.; Sekido, M.

    2010-01-01

    A total solar eclipse occurred over China at latitudes of about 30 N on the morning of 22 July 2009, providing a unique opportunity to investigate the influence of the sun on the earth's upper ionosphere. GPS observations from Shanghai GPS Local Network and VLBI observations from stations Shanghai, Urumqi, and Kashima were used to observe the response of TEC to the total solar eclipse. From the GPS data reduction, the sudden decrease of TEC at the time of the eclipse, amounting to 2.8 TECU, and gradual increase of TEC after the eclipse were found by analyzing the diurnal variations. More distinctly, the variations of TEC were studied along individual satellite passes. The delay in reaching the minimum level of TEC with the maximum phase of eclipse was 5-10 min. Besides, we also compared the ionospheric activity derived from different VLBI stations with the GPS results and found a strong correlation between them.

  9. Determinations of ionosphere and plasmasphere electron content for an African chain of GPS stations

    Science.gov (United States)

    Mazzella, Andrew J., Jr.; Bosco Habarulema, John; Yizengaw, Endawoke

    2017-05-01

    The confluence of recent instrumentation deployments in Africa with developments for the determination of plasmasphere electron content using Global Positioning System (GPS) receivers has provided new opportunities for investigations in that region. This investigation, using a selected chain of GPS stations, extends the method (SCORPION) previously applied to a chain of GPS stations in North America in order to separate the ionosphere and plasmasphere contributions to the total electron content (TEC) during a day (24 July) in 2011. The results span latitudes from the southern tip of Africa, across the Equator, to the southern Arabian Peninsula, providing a continuous latitudinal profile for both the ionosphere and plasmasphere during this day.The peak diurnal vertical ionosphere electron content (IEC) increases from about 14 TEC units (1 TEC unit = 1016 electrons m-2) at the southernmost station to about 32 TEC units near the geographic equator, then decreases to about 28 TEC units at the Arabian Peninsula. The peak diurnal slant plasmasphere electron content (PEC) varies between about 4 and 7 TEC units among the stations, with a local latitudinal profile that is significantly influenced by the viewing geometry at the station location, relative to the magnetic field configuration. In contrast, the peak vertical PEC varies between about 1 and 6 TEC units among the stations, with a more uniform latitudinal variation.Comparisons to other GPS data analyses are also presented for TEC, indicating the influence of the PEC on the determination of latitudinal TEC variations and also on the absolute TEC levels, by inducing an overestimate of the receiver bias. The derived TEC latitudinal profiles, in comparison to global map profiles, tend to differ from the map results only about as much as the map results differ among themselves. A combination of ionosonde IEC and alternative GPS TEC measurements, which in principle permits a PEC determination through their difference, was

  10. Storm-Time Ionospheric Disturbances Monitored by GPS Beacon Measurements

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Total Electron Content (TEC) during three great storms, from April to August 2000, was collected by means of a GPS receiver located in Jingzhou (30. 4° N, 112. 2° E). The time-latitude-dependent features of ionospheric storms are identified using TEC difference images based on the deviations of TEC during storm relative to quiet time. The responses of ionospheric TEC to magnetic storms were analyzed. The results show that: 1) In middle and low latitude, ionospheric storms effects are more apparent in local day time than at night; 2) Ionospheric storm effects are more dominant near the hump of the equatorial anomaly region than in other regions of TEC measurements; 3) The positive effects during the main phase of iono spheric storm may be caused by electric fields in low latitude; 4) During the recovery period of ionospheric storm, the negative phase of storm may be due to the perturbation of the neutral gas composition.

  11. The GPS Radio Occultation and Ultraviolet Photometry—Colocated (GROUP-C) Experiment on the ISS

    Science.gov (United States)

    Budzien, Scott A.; Powell, Steven P.; Psiaki, Mark; O'Hanlon, Brady; Stephan, Andrew W.; Bishop, Rebecca L.

    2015-04-01

    The GPS Radio Occultation and Ultraviolet Photometry—Colocated (GROUP-C) Experiment is an ionospheric remote sensing experiment manifested to fly on the International Space Station in early 2016. GROUP-C will operate aboard the Space Test Program Houston 5 (STP-H5) experiment pallet and provide ionospheric measurements in real-time. GROUP-C includes two sensors: the Fast Orbital TEC, Observables, and Navigation (FOTON) L1/L2 GPS receiver, which provides vertical electron density profiles and scintillation; and the Tiny Ionospheric Photometer (TIP), a far-ultraviolet photometer for measuring horizontal ionosphere gradients. The FOTON receiver includes a capability for multipath mitigation using a multi-antenna array. The TIP photometer is similar to the photometers aboard the COSMIC satellites with minor improvements in optical performance.Ionospheric irregularities, also known as ionospheric bubbles, are transient features of the low and middle latitude ionosphere with important implications for operational systems. Understanding irregularity formation, development, and evolution is vital for efforts within NASA and DoD to forecast scintillation. Irregularity structures have been studied primarily using ground-based systems, though some spaced-based remote and in-situ sensing has been performed. In combination with GROUP-C, the Limb-imaging Ionospheric and Thermospheric Extreme-ultraviolet Spectrograph (LITES) experiment on STP-H5 will serve as an interactive ionospheric observatory on the ISS. These experiments would provide new capability to study low- and mid-latitude ionospheric structures on a global scale. By combining for the first time high-sensitivity in-track photometry with vertical ionospheric airglow spectrographic imagery, and simultaneous GPS TEC and scintillation measurements, high-fidelity optical tomographic reconstruction of bubbles can be performed from the ISS. Ground-based imagery can supplement the tomography by providing all-sky images of

  12. TEC – Thin Environmental Cladding

    Directory of Open Access Journals (Sweden)

    Alan Tomasi

    2014-06-01

    Full Text Available Corresponding author: Alan Tomasi, Group R&D Project Manager, Permasteelisa S.p.A., viale E. Mattei 21/23 | 31029 Vittorio Veneto, Treviso, Italy. Tel.: +39 0438 505207; E-mail: a.tomasi@permasteelisagroup.com; www.permasteelisagroup.com Permasteelisa Group developed with Fiberline Composites a new curtain wall system (Thin Environmental Cladding or TEC, making use of pultruded GFRP (Glass Fiber Reinforced Polymer material instead of traditional aluminum. Main advantages using GFRP instead of aluminum are the increased thermal performance and the limited environmental impact. Selling point of the selected GFRP resin is the light transmission, which results in pultruded profiles that allow the visible light to pass through them, creating great aesthetical effects. However, GFRP components present also weaknesses, such as high acoustic transmittance (due to the reduced weight and anisotropy of the material, low stiffness if compared with aluminum (resulting in higher facade deflection and sensible fire behavior (as combustible material. This paper will describe the design of the TEC-facade, highlighting the functional role of glass within the facade concept with regards to its acoustic, structural, aesthetics and fire behavior.

  13. Ground-based observations of exoplanet atmospheres

    NARCIS (Netherlands)

    Mooij, Ernst Johan Walter de

    2011-01-01

    This thesis focuses on the properties of exoplanet atmospheres. The results for ground-based near-infrared secondary eclipse observations of three different exoplanets, TrES-3b, HAT-P-1b and WASP-33b, are presented which have been obtained with ground-based telescopes as part of the GROUSE project.

  14. Ground-based observations of exoplanet atmospheres

    NARCIS (Netherlands)

    Mooij, Ernst Johan Walter de

    2011-01-01

    This thesis focuses on the properties of exoplanet atmospheres. The results for ground-based near-infrared secondary eclipse observations of three different exoplanets, TrES-3b, HAT-P-1b and WASP-33b, are presented which have been obtained with ground-based telescopes as part of the GROUSE project.

  15. Detection of Natural Hazards Generated TEC Perturbations and Related New Applications

    Science.gov (United States)

    Komjathy, A.; Yang, Y.; Langley, R. B.

    2013-12-01

    Natural hazards, including earthquakes, volcanic eruptions, and tsunamis, have been significant threats to humans throughout recorded history. The Global Positioning System satellites have become primary sensors to measure signatures associated with such natural hazards. These signatures typically include GPS-derived seismic deformation measurements, co-seismic vertical displacements, and real-time GPS-derived ocean buoy positioning estimates. Another way to use GPS observables is to compute the ionospheric total electron content (TEC) to measure and monitor post-seismic ionospheric disturbances caused by earthquakes, volcanic eruptions, and tsunamis. Research at the University of New Brunswick (UNB) laid the foundations to model the three-dimensional ionosphere at NASA's Jet Propulsion Laboratory by ingesting ground- and space-based GPS measurements into the state-of-the-art Global Assimilative Ionosphere Modeling (GAIM) software. As an outcome of the UNB and NASA research, new and innovative GPS applications have been invented including the use of ionospheric measurements to detect tiny fluctuations in the GPS signals between the spacecraft and GPS receivers caused by natural hazards occurring on or near the Earth's surface. This continuing research is expected to provide early warning for tsunamis, earthquakes, volcanic eruptions, and meteor impacts, for example, using GPS and other global navigation satellite systems. We will demonstrate new and upcoming applications including recent natural hazards and artificial explosions that generated TEC perturbations to perform state-of-the-art imaging and modeling of earthquakes, tsunamis and meteor impacts. By studying the propagation properties of ionospheric perturbations generated by natural hazards along with applying sophisticated first-principles physics-based modeling, we are on track to develop new technologies that can potentially save human lives and minimize property damage.

  16. Performance evaluation of linear time-series ionospheric Total Electron Content model over low latitude Indian GPS stations

    Science.gov (United States)

    Dabbakuti, J. R. K. Kumar; Venkata Ratnam, D.

    2017-10-01

    Precise modeling of the ionospheric Total Electron Content (TEC) is a critical aspect of Positioning, Navigation, and Timing (PNT) services intended for the Global Navigation Satellite Systems (GNSS) applications as well as Earth Observation System (EOS), satellite communication, and space weather forecasting applications. In this paper, linear time series modeling has been carried out on ionospheric TEC at two different locations at Koneru Lakshmaiah University (KLU), Guntur (geographic 16.44° N, 80.62° E; geomagnetic 7.55° N) and Bangalore (geographic 12.97° N, 77.59° E; geomagnetic 4.53° N) at the northern low-latitude region, for the year 2013 in the 24th solar cycle. The impact of the solar and geomagnetic activity on periodic oscillations of TEC has been investigated. Results confirm that the correlation coefficient of the estimated TEC from the linear model TEC and the observed GPS-TEC is around 93%. Solar activity is the key component that influences ionospheric daily averaged TEC while periodic component reveals the seasonal dependency of TEC. Furthermore, it is observed that the influence of geomagnetic activity component on TEC is different at both the latitudes. The accuracy of the model has been assessed by comparing the International Reference Ionosphere (IRI) 2012 model TEC and TEC measurements. Moreover, the absence of winter anomaly is remarkable, as determined by the Root Mean Square Error (RMSE) between the linear model TEC and GPS-TEC. On the contrary, the IRI2012 model TEC evidently failed to predict the absence of winter anomaly in the Equatorial Ionization Anomaly (EIA) crest region. The outcome of this work will be useful for improving the ionospheric now-casting models under various geophysical conditions.

  17. GPS Separator

    CERN Multimedia

    2016-01-01

    Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.

  18. Hacking GPS

    CERN Document Server

    Kingsley-Hughes, Kathie

    2005-01-01

    * This is the "user manual" that didn't come with any of the 30 million GPS receivers currently in use, showing readers how to modify, tweak, and hack their GPS to take it to new levels!* Crazy-cool modifications include exploiting secret keycodes, revealing hidden features, building power cords and cables, hacking the battery and antenna, protecting a GPS from impact and falls, making a screen protector, and solar-powering a GPS* Potential power users will take the function and performance of their GPS to a whole new level by hacking into the firmware and hacking into a PC connection with a GPS* Fear not! Any potentially dangerous mod (to the device) is clearly labeled, with precautions listed that should be taken* Game time! Readers can check out GPS games, check into hacking geocaching, and even use a GPS as a metal detector

  19. The study of variability of TEC over mid-latitude American regions during the ascending phase of solar cycle 24 (2009-2011)

    Science.gov (United States)

    Asmare Tariku, Yekoye

    2016-08-01

    This paper deals with the pattern of the variability of the Global Positioning System vertical total electron content (GPS VTEC) and the modeled vertical total electron content (IRI 2012 TEC) over American mid-latitude regions during the rising phase of solar cycle 24 (2009-2011). This has been conducted employing ground-based dual frequency GPS receiver installed at Mississippi County Airport (geographic lat. 36.85°N and long. 270.64°E). In this work, the monthly and seasonal variations in the measured VTEC have been analyzed and compared with the VTEC inferred from IRI-2012 model. It has been shown that the monthly and seasonal mean VTEC values get decreased mostly between 05:00 and 10:00 UT and reach their minimal nearly at around 10:00 UT for both the experimental and the model. The VTEC values then get increased and reach the peak values at around 20:00 UT and decrease again. Moreover, it is depicted that the model better estimates both the monthly and seasonal mean hourly VTEC values mostly between 15:00 and 20:00 UT. The modeled monthly and seasonal VTEC values are smaller than the corresponding measured values as the solar activity decreases when all options for the topside electron density are used. However, as the Sun goes from a very low to a high solar activity, the overestimation performance of the VTEC values derived from the model increases. The overall results show that it is generally better to use the model with IRI-2000 option for the topside electron density in estimating the monthly and seasonal VTEC variations, especially when the activity of the Sun decreases.

  20. GPS Metric Tracking Unit

    Science.gov (United States)

    2008-01-01

    As Global Positioning Satellite (GPS) applications become more prevalent for land- and air-based vehicles, GPS applications for space vehicles will also increase. The Applied Technology Directorate of Kennedy Space Center (KSC) has developed a lightweight, low-cost GPS Metric Tracking Unit (GMTU), the first of two steps in developing a lightweight, low-cost Space-Based Tracking and Command Subsystem (STACS) designed to meet Range Safety's link margin and latency requirements for vehicle command and telemetry data. The goals of STACS are to improve Range Safety operations and expand tracking capabilities for space vehicles. STACS will track the vehicle, receive commands, and send telemetry data through the space-based asset, which will dramatically reduce dependence on ground-based assets. The other step was the Low-Cost Tracking and Data Relay Satellite System (TDRSS) Transceiver (LCT2), developed by the Wallops Flight Facility (WFF), which allows the vehicle to communicate with a geosynchronous relay satellite. Although the GMTU and LCT2 were independently implemented and tested, the design collaboration of KSC and WFF engineers allowed GMTU and LCT2 to be integrated into one enclosure, leading to the final STACS. In operation, GMTU needs only a radio frequency (RF) input from a GPS antenna and outputs position and velocity data to the vehicle through a serial or pulse code modulation (PCM) interface. GMTU includes one commercial GPS receiver board and a custom board, the Command and Telemetry Processor (CTP) developed by KSC. The CTP design is based on a field-programmable gate array (FPGA) with embedded processors to support GPS functions.

  1. Climatology characterization of equatorial plasma bubbles using GPS data

    Science.gov (United States)

    Magdaleno, Sergio; Herraiz, Miguel; Altadill, David; de la Morena, Benito A.

    2017-01-01

    The climatology of equatorial plasma bubbles (EPBs) for the period 1998-2008 was studied using slant total electron content (sTEC) derived from global positioning system (GPS) data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS) stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA). EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS) application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu). The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.

  2. Climatology characterization of equatorial plasma bubbles using GPS data

    Directory of Open Access Journals (Sweden)

    Magdaleno Sergio

    2017-01-01

    Full Text Available The climatology of equatorial plasma bubbles (EPBs for the period 1998–2008 was studied using slant total electron content (sTEC derived from global positioning system (GPS data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA. EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu. The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.

  3. Characterization of GPS total electron content (GPS-TEC in Antarctica from 2004 to 2011

    Directory of Open Access Journals (Sweden)

    Emília Correia

    2013-06-01

    Full Text Available The vertical total electron content (VTEC obtained from 2004 to 2011 at Comandante Ferraz Brazilian Antarctic Station (62.1°S, 58.4°W is analyzed to study the mean diurnal, seasonal and annual variations. The maximum daytime VTEC had an annual variation that decreased from 2004 to 2008, and then starting to increase in 2009, which followed the variation of the solar activity. The daily VTEC shows good linear correlation with solar radiation intensity, which is also dependent on the solar zenithal angle. The mean diurnal VTEC shows a semiannual variation, with larger peaks in equinoxes for all years; no winter anomaly was observed, and in summer, there was no clear diurnal variation. The semiannual variation of the VTEC is also modulated by solar activity, with larger VTEC peaks when the solar activity was higher.

  4. Fresnel zones for ground-based antennas

    DEFF Research Database (Denmark)

    Andersen, J. Bach

    1964-01-01

    The ordinary Fresnel zone concept is modified to include the influence of finite ground conductivity. This is important for ground-based antennas because the influence on the radiation pattern of irregularities near the antenna is determined by the amplitude and phase of the groundwave. A new...

  5. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement unce...

  6. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Yordanova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement unce...

  7. A Ground-Based Array to Observe Geospace Electrodynamics During Adverse Space Weather Conditions

    Science.gov (United States)

    Sojka, J. J.; Eccles, J. V.; Rice, D.

    2004-05-01

    Geomagnetic Storms occur with surprising frequency and create adverse space weather conditions. During these periods, our knowledge and ability to specify or forecast in adequate detail for user needs is negligible. Neither experimental observations nor theoretical developments have made a significant new impact on the problem for over two decades. Although we can now map Total Electron Content (TEC) in the ionosphere over a continent with sufficient resolution to see coherent long-lived structures, these do not provide constraints on the geospace electrodynamics that is at the heart of our lack of understanding. We present arguments for the need of a continental deployment of ground-based sensors to stepwise advance our understanding of the geospace electrodynamics when it is most adverse from a space weather perspective and also most frustrating from an understanding of Magnetosphere-Ionosphere coupling. That a continental-scale deployment is more productive at addressing the problem than a realizable global distribution is shown. Each measurement is discussed from the point-of-view of either providing new knowledge or becoming a key for future real-time specification and forecasting for user applications. An example of a storm database from one mid-latitude station for the 31 March 2002 is used as a conceptual point in a ground-based array. The presentation focuses on scientific questions that have eluded a quantitative solution for over three decades and view a ground-based array as an "IGY" type of catalyst for answering these questions.

  8. Space and Ground-Based Infrastructures

    Science.gov (United States)

    Weems, Jon; Zell, Martin

    This chapter deals first with the main characteristics of the space environment, outside and inside a spacecraft. Then the space and space-related (ground-based) infrastructures are described. The most important infrastructure is the International Space Station, which holds many European facilities (for instance the European Columbus Laboratory). Some of them, such as the Columbus External Payload Facility, are located outside the ISS to benefit from external space conditions. There is only one other example of orbital platforms, the Russian Foton/Bion Recoverable Orbital Capsule. In contrast, non-orbital weightless research platforms, although limited in experimental time, are more numerous: sounding rockets, parabolic flight aircraft, drop towers and high-altitude balloons. In addition to these facilities, there are a number of ground-based facilities and space simulators, for both life sciences (for instance: bed rest, clinostats) and physical sciences (for instance: magnetic compensation of gravity). Hypergravity can also be provided by human and non-human centrifuges.

  9. Development of Ground-Based Plant Sentinels

    Science.gov (United States)

    2007-11-02

    plants in response to different strains of Pseudomonas syringae. Planta . 217:767-775. De Moraes CM, Schultz JC, Mescher MC, Tumlinson JH. (2004...09-30-2004 Final Technical _ April 2001 - April 2003 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Developing Plants as Ground-based Sentinels 5b. GRANT...SUPPLEMENTARY NOTES 14. ABSTRACT 9 "Z Plants emit volatile mixes characteristic of exposure to both plant and animal (insect) pathogens (bacteria and fungi). The

  10. Illumination compensation in ground based hyperspectral imaging

    Science.gov (United States)

    Wendel, Alexander; Underwood, James

    2017-07-01

    Hyperspectral imaging has emerged as an important tool for analysing vegetation data in agricultural applications. Recently, low altitude and ground based hyperspectral imaging solutions have come to the fore, providing very high resolution data for mapping and studying large areas of crops in detail. However, these platforms introduce a unique set of challenges that need to be overcome to ensure consistent, accurate and timely acquisition of data. One particular problem is dealing with changes in environmental illumination while operating with natural light under cloud cover, which can have considerable effects on spectral shape. In the past this has been commonly achieved by imaging known reference targets at the time of data acquisition, direct measurement of irradiance, or atmospheric modelling. While capturing a reference panel continuously or very frequently allows accurate compensation for illumination changes, this is often not practical with ground based platforms, and impossible in aerial applications. This paper examines the use of an autonomous unmanned ground vehicle (UGV) to gather high resolution hyperspectral imaging data of crops under natural illumination. A process of illumination compensation is performed to extract the inherent reflectance properties of the crops, despite variable illumination. This work adapts a previously developed subspace model approach to reflectance and illumination recovery. Though tested on a ground vehicle in this paper, it is applicable to low altitude unmanned aerial hyperspectral imagery also. The method uses occasional observations of reference panel training data from within the same or other datasets, which enables a practical field protocol that minimises in-field manual labour. This paper tests the new approach, comparing it against traditional methods. Several illumination compensation protocols for high volume ground based data collection are presented based on the results. The findings in this paper are

  11. Ground based spectroscopy of hot Jupiters

    Science.gov (United States)

    Waldmann, Ingo

    2010-05-01

    It has been shown in recent years with great success that spectroscopy of exoplanetary atmospheres is feasible using space based observatories such as the HST and Spitzer. However, with the end of the Spitzer cold-phase, space based observations in the near to mid infra-red are limited, which will remain true until the the onset of the JWST. The importance of developing methods of ground based spectroscopic analysis of known hot Jupiters is therefore apparent. In the past, various groups have attempted exoplanetary spectroscopy using ground based facilities and various techniques. Here I will present results using a novel spectral retrieval method for near to mid infra-red emission and transmission spectra of exoplanetary atmospheres taken from the ground and discuss the feasibility of future ground-based spectroscopy in a broader context. My recently commenced PhD project is under the supervision of Giovanna Tinetti (University College London) and in collaboration with J. P. Beaulieu (Institut d'Astrophysique de Paris), Mark Swain and Pieter Deroo (Jet Propulsion Laboratory, Caltech).

  12. Expanding the PhysTEC Coalition

    Science.gov (United States)

    Stein, Fredrick

    2003-04-01

    The Physics Teacher Education Coalition (PhysTEC) is a community of physics departments representing scientists and educators at institutions dedicated to improving the science preparation of future K-12 teachers. Now in its second year, PhysTEC requires physics and education faculty to work together to provide an education for future teachers that emphasizes interactive engagement and a student-centered approach to learning science. The first six Coalition members are the physics departments at Ball State University, Oregon State University, University of Arizona, University of Arkansas, Western Michigan University, and Xavier University of Louisiana. PhysTEC is creating a broad, active Coalition of physics departments that have implemented or are interested in implementing one or more of the PhysTEC Program Components. · A long-term, active collaboration among the physics department, the department of education, and the local schools. · A Teacher-in-Residence (TIR) program that provides for a full-time participant in assisting faculty in course revisions. · The redesign of physics courses based on results from physics education research. · The redesign of elementary and secondary science methods courses with an emphasis on inquiry-based teaching and learning. · The establishment of a mentoring program to provide a valuable induction experience for novice science teachers. · The participation of physics faculty in the improvement and expansion of school experiences. www.phystec.org

  13. Solar activity indices as a proxy for the variation of ionospheric Total Electron Content (TEC) over Bahir Dar, Ethiopia during the year 2010-2014

    Science.gov (United States)

    Kassa, Tsegaye; Tilahun, Samson; Damtie, Baylie

    2017-09-01

    This paper was aimed at investigating the solar variations of vTEC as a function of solar activity parameters, EUV and F10.7 radio flux. The daily values of ionospheric vertical Total Electron Content (vTEC) were observed using a dual frequency GPS receiver deployed at Bahir Dar (11.6°N and 37.36°E), Ethiopia. Measurements were taken during the period of 2010-2014 for successive five years and analysis was done on only quiet day observations. A quadratic fit was used as a model to describe the daily variation of vTEC in relation to solar parameters. Linear and non-linear coefficients of the vTEC variations were calculated in order to capture the trend of the variation. The variation of vTEC have showed good agreement with the trend of solar parameters in almost all of the days we consider during the period of our observations. We have explicitly observed days with insignificant TECU deviation (eg. modeling with respect to EUV, DOY = 49 in 2010 and modeling with respect to F10.7, DOY = 125 in 2012 and the like) and days with maximum deviation (about 50 TECU). A maximum deviation were observed, on average, during months of equinox whereas minimum during solstice months. This implies that there is a need to consider more parameters, including EUV and F10.7, that can affect the variation of vTEC during equinox seasons. Relatively, small deviations was observed in modeling vTEC as a function of EUV compared to that of the variation due to F10.7 cm flux. This may also tell us that EUV can be more suitable in modeling the solar variation of vTEC especially for longterm trends. Even though, the linear trend of solar variations of vTEC was frequently observed, significant saturation and amplification trends of the solar variations of vTEC were also observed to some extent across the months of the years we have analyzed. This mixed trend of the solar variation of vTEC implies the need for thorough investigation on the effect of solar parameters on TEC. However, based on

  14. GPS & Roadpricing

    DEFF Research Database (Denmark)

    Zabic, Martina

    2005-01-01

    I denne artikel præsenteres analysemetoderne og resultaterne fra et eksamensprojekt omhandlende en analyse af GPS kvaliteten i forhold til roadpricing i København. Denne undersøgelse af GPS kvaliteten i forbindelse med roadpricing, er foretaget i tilknytning til det danske AKTA forsøg (www.......akta-kbh.dk), hvor GPS data er indsamlet for 500 biler over en 2-årig periode (2001-2003). Artiklen præsenterer således en analyse af GPS nøjagtigheden med henblik på at undersøge om kvalitet og pålidelighed er tilstrækkelig, til et GPS-baseret roadpricingssystem i København. Ved GPS-baseret roadpricing, udstyres...... med henblik på enhedsomkostningerne skulle være økonomisk realisable til brug i et så omfattende roadpricingssystem. Endvidere vanskeliggøres positionerings forholdene, idet bilen der ønskes positionsbestemt er i bevægelse. Når både satellitterne og GPS modtageren er i bevægelse, reduceres...

  15. GPS & Roadpricing

    DEFF Research Database (Denmark)

    Zabic, Martina

    2005-01-01

    I denne artikel præsenteres analysemetoderne og resultaterne fra et eksamensprojekt omhandlende en analyse af GPS kvaliteten i forhold til roadpricing i København. Denne undersøgelse af GPS kvaliteten i forbindelse med roadpricing, er foretaget i tilknytning til det danske AKTA forsøg (www.......akta-kbh.dk), hvor GPS data er indsamlet for 500 biler over en 2-årig periode (2001-2003). Artiklen præsenterer således en analyse af GPS nøjagtigheden med henblik på at undersøge om kvalitet og pålidelighed er tilstrækkelig, til et GPS-baseret roadpricingssystem i København. Ved GPS-baseret roadpricing, udstyres...... med henblik på enhedsomkostningerne skulle være økonomisk realisable til brug i et så omfattende roadpricingssystem. Endvidere vanskeliggøres positionerings forholdene, idet bilen der ønskes positionsbestemt er i bevægelse. Når både satellitterne og GPS modtageren er i bevægelse, reduceres...

  16. A new method for estimation of TEC from GNSS receivers during multiple cycle slips and data loss due to ionospheric irregularities

    Science.gov (United States)

    Dashora, Nirvikar

    2012-07-01

    Estimation of total electron content (TEC) is a must to utilize the GNSS signal for ionospheric research. The estimation of absolute ionospheric TEC from raw GNSS data itself is a lengthy and complex task and requires knowledge of sophisticated computer programming skills, satellite orbital geometry and many other aspects like GNSS signal structure, satellite and receiver specific information etc. Not many software are available that automatize the complex task of cycle slip detection and correction. The estimation of satellite and receiver biases is one more step left before getting true TEC. In equatorial and low latitudes, where the nighttime ionospheric irregularities are oft-occurring phenomena, estimation of TEC becomes a challenge. This is because, during TEC depletions and scintillations, the loss of lock in the receiver results either in data loss or sharp gradients in the recorded delays; more often for phase than code. Raw data in form of accumulated phase in radians and total code-range in meters show random occurrences of multiple cycle slips and data loss of several minutes in the data file. Thus, such phase and code data has to be corrected first before processing it to obtain TEC. Almost all available software/algorithms suggest flagging such data for no further use. Hence, TEC cannot be estimated during multiple cycle slip events within few minutes from raw GPS data. But, for ionospheric research the time of occurrence, evolution and drift of depletions are very useful. This paper details a complete new software for pre-processing the raw RINEX (receiver independent exchange format) data and retrieval of TEC using code and carrier-phase measurements from an stand alone dual frequency GPS receiver. We use modified and new sets of algorithms a GNSS receiver. It is significant to note that we are able to retrieves almost all the the corrupted TEC data points due to random multiple cycle slip events which are oft-occurring phenomena during ESF in

  17. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  18. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of a test of a ground-based lidar of other type. The test was performed at DTU’s test site for large wind turbines at Høvsøre, Denmark. The result as an establishment of a relation between the reference wind speed measurements with measurement uncertainties provided...... by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The comparison of the lidar measurements of the wind direction with that from the wind vanes is also given....

  19. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Yordanova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  20. Calibration of Ground-based Lidar instrument

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Gómez Arranz, Paula

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  1. Calibration of Ground -based Lidar instrument

    DEFF Research Database (Denmark)

    Villanueva, Héctor; Georgieva Yankova, Ginka

    This report presents the result of the lidar calibration performed for the given Ground-based Lidar at DTU’s test site for large wind turbines at Høvsøre, Denmark. Calibration is here understood as the establishment of a relation between the reference wind speed measurements with measurement...... uncertainties provided by measurement standard and corresponding lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from wind vanes...

  2. Comparison of temporal fluctuations in the total electron content estimates from EISCAT and GPS along the same line of sight

    Directory of Open Access Journals (Sweden)

    B. Forte

    2013-04-01

    Full Text Available The impact of space weather events on satellite-based technologies (e.g. satellite navigation and precise positioning is typically quantified on the basis of the total electron content (TEC and temporal fluctuations associated with it. GNSS (global navigation satellite systems TEC measurements are integrated over a long distance and thus may include contributions from different regions of the ionised atmosphere which may prevent the resolution of the mechanisms ultimately responsible for given observations. The purpose of the experiment presented here was to compare TEC estimates from EISCAT and GPS measurements. The EISCAT measurements were obtained along the same line of sight of a given GPS satellite observed from Tromsø. The present analyses focussed on the comparison of temporal fluctuations in the TEC between aligned GPS and EISCAT measurements. A reasonably good agreement was found between temporal fluctuations in TEC observed by EISCAT and those observed by a co-located GPS ionospheric monitor along the same line of sight, indicating a contribution from structures at E and F altitudes mainly to the total TEC in the presence of ionisation enhancements possibly caused by particle precipitation in the nighttime sector. The experiment suggests the great potential in the measurements to be performed by the future EISCAT_3D system, limited only in the localised geographic region to be covered.

  3. Investigation of TEC and VLF space measurements associated to L'Aquila (Italy earthquakes

    Directory of Open Access Journals (Sweden)

    G. Stangl

    2011-04-01

    Full Text Available In this study, we report on Total Electron Content (TEC and Very Low Frequency (VLF space measurements derived from Global Positioning System (GPS and DEMETER satellites, respectively. These measurements are associated with the earthquake (EQ of a magnitude of 6.3, which occurred on 6 April 2009, in L'Aquila (Italy. Anomaly features are derived from the analysis of TEC and VLF observations recorded two weeks before and after the seismic event occurrence. A TEC map with an interpolated regional pixel resolution of 1° × 1° × 15 min in latitude, longitude and time was generated, allowing for the checking of a possible presence of disturbances over the L'Aquila region. This analysis is combined with the study of the time profile associated to the VLF flux density variations recorded by the Instrument Champ Electrique (ICE experiment on-board DEMETER satellite. We discuss, on the one hand, the combination efficiency of the electronic density and the VLF electromagnetic measurements and, on the other hand, the difficulty to distinguish between global effects and regional ones related to the earthquake.

  4. An ensemble average method to estimate absolute TEC using radio beacon-based differential phase measurements: Applicability to regions of large latitudinal gradients in plasma density

    Science.gov (United States)

    Thampi, Smitha V.; Bagiya, Mala S.; Chakrabarty, D.; Acharya, Y. B.; Yamamoto, M.

    2014-12-01

    A GNU Radio Beacon Receiver (GRBR) system for total electron content (TEC) measurements using 150 and 400 MHz transmissions from Low-Earth Orbiting Satellites (LEOS) is fabricated in house and made operational at Ahmedabad (23.04°N, 72.54°E geographic, dip latitude 17°N) since May 2013. This system receives the 150 and 400 MHz transmissions from high-inclination LEOS. The first few days of observations are presented in this work to bring out the efficacy of an ensemble average method to convert the relative TECs to absolute TECs. This method is a modified version of the differential Doppler-based method proposed by de Mendonca (1962) and suitable even for ionospheric regions with large spatial gradients. Comparison of TECs derived from a collocated GPS receiver shows that the absolute TECs estimated by this method are reliable estimates over regions with large spatial gradient. This method is useful even when only one receiving station is available. The differences between these observations are discussed to bring out the importance of the spatial differences between the ionospheric pierce points of these satellites. A few examples of the latitudinal variation of TEC during different local times using GRBR measurements are also presented, which demonstrates the potential of radio beacon measurements in capturing the large-scale plasma transport processes in the low-latitude ionosphere.

  5. GPS Composite Clock Analysis

    OpenAIRE

    Wright, James R.

    2008-01-01

    The GPS composite clock defines GPS time, the timescale used today in GPS operations. GPS time is illuminated by examination of its role in the complete estimation and control problem relative to UTC/TAI. The phase of each GPS clock is unobservable from GPS pseudorange measurements, and the mean phase of the GPS clock ensemble (GPS time) is unobservable. A new and useful observability definition is presented, together with new observability theorems, to demonstrate explicitly that GPS time is...

  6. GENESIS: GPS Environmental and Earth Science Information System

    Science.gov (United States)

    Hajj, George

    1999-01-01

    This presentation reviews the GPS ENvironmental and Earth Science Information System (GENESIS). The objectives of GENESIS are outlined (1) Data Archiving, searching and distribution for science data products derived from Space borne TurboRogue Space Receivers for GPS science and other ground based GPS receivers, (2) Data browsing using integrated visualization tools, (3) Interactive web/java-based data search and retrieval, (4) Data subscription service, (5) Data migration from existing GPS archived data, (6) On-line help and documentation, and (7) participation in the WP-ESIP federation. The presentation reviews the products and services of Genesis, and the technology behind the system.

  7. Analysis of meteorological variables in the Australasian region using ground- and space-based GPS techniques

    Science.gov (United States)

    Kuleshov, Yuriy; Choy, Suelynn; Fu, Erjiang Frank; Chane-Ming, Fabrice; Liou, Yuei-An; Pavelyev, Alexander G.

    2016-07-01

    Results of analysis of meteorological variables (temperature and moisture) in the Australasian region using the global positioning system (GPS) radio occultation (RO) and GPS ground-based observations verified with in situ radiosonde (RS) data are presented. The potential of using ground-based GPS observations for retrieving column integrated precipitable water vapour (PWV) over the Australian continent has been demonstrated using the Australian ground-based GPS reference stations network. Using data from the 15 ground-based GPS stations, the state of the atmosphere over Victoria during a significant weather event, the March 2010 Melbourne storm, has been investigated, and it has been shown that the GPS observations has potential for monitoring the movement of a weather front that has sharp moisture contrast. Temperature and moisture variability in the atmosphere over various climatic regions (the Indian and the Pacific Oceans, the Antarctic and Australia) has been examined using satellite-based GPS RO and in situ RS observations. Investigating recent atmospheric temperature trends over Antarctica, the time series of the collocated GPS RO and RS data were examined, and strong cooling in the lower stratosphere and warming through the troposphere over Antarctica has been identified, in agreement with outputs of climate models. With further expansion of the Global Navigation Satellite Systems (GNSS) system, it is expected that GNSS satellite- and ground-based measurements would be able to provide an order of magnitude larger amount of data which in turn could significantly advance weather forecasting services, climate monitoring and analysis in the Australasian region.

  8. Validation of GOME-2/Metop total column water vapour with ground-based and in situ measurements

    Science.gov (United States)

    Kalakoski, Niilo; Kujanpää, Jukka; Sofieva, Viktoria; Tamminen, Johanna; Grossi, Margherita; Valks, Pieter

    2016-04-01

    The total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde observations and global positioning system (GPS) retrievals. The validation is performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The time periods for the validation are January 2007-July 2013 (GOME-2A) and December 2012-July 2013 (GOME-2B). The radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by the National Climatic Data Center (NCDC). The ground-based GPS observations from the COSMIC/SuomiNet network are used as the second independent data source. We find a good general agreement between the GOME-2 and the radiosonde/GPS data. The median relative difference of GOME-2 to the radiosonde observations is -2.7 % for GOME-2A and -0.3 % for GOME-2B. Against the GPS, the median relative differences are 4.9 % and 3.2 % for GOME-2A and B, respectively. For water vapour total columns below 10 kg m-2, large wet biases are observed, especially against the GPS retrievals. Conversely, at values above 50 kg m-2, GOME-2 generally underestimates both ground-based observations.

  9. Investigations of the Nature and Behavior of Plasma Density Disturbances That May Impact GPS and Other Transionospheric Systems

    Science.gov (United States)

    2006-05-31

    maintained and enhanced in association with the High-frequency Active Auroral Research Program ( HAARP ). In addition to a classic riometer and a GPS Total...Electron Content (TEC) sensor previously operating at the HAARP site, NWRA also operates a set of Transit receivers for measurements of TEC and...scintillation at VHF and UHF, supplementing the receiver at HAARP with a receiver north of the site and an additional receiver installed south of the HAARP site.

  10. Code and codeless ionospheric measurements with NASA's Rogue GPS Receiver

    Science.gov (United States)

    Srinivasan, Jeff M.; Meehan, Tom K.; Young, Lawrence E.

    1989-01-01

    The NASA/JPL Rogue Receiver is an 8-satellite, non-multiplexed, highly digital global positioning system (GPS) receiver that can obtain dual frequency data either with or without knowledge of the P-code. In addition to its applications for high accuracy geodesy and orbit determination, the Rogue uses GPS satellite signals to measure the total electron content (TEC) of the ionosphere along the lines of sight from the receiver to the satellites. These measurements are used by JPL's Deep Space Network (DSN) for calibrating radiometric data. This paper will discuss Rogue TEC measurements, emphasizing the advantages of a receiver that can use the P-code, when available, but can also obtain reliable dual frequency data when the code is encrypted.

  11. The structure of mid- and high-latitude ionosphere during September 1999 storm event obtained from GPS observations

    Directory of Open Access Journals (Sweden)

    I. I. Shagimuratov

    Full Text Available TEC data, obtained from over 60 GPS stations, were used to study the ionospheric effects of the 12–16 September 1999 magnetic storm over Europe. The spatial and temporal changes of the ionosphere were analysed as a time series of TEC maps, which present 15 min averages of TEC. The data set consisting of GPS observations, collected by a dense network of European stations, with sampling rate of 30 s, enable the creation of TEC maps with high spatial and temporal resolution. The storm included the positive as well as the negative phase. The positive phase took place during the first storm day of 12 September 1999. The short-lived daytime TEC enhancement was observed at all latitudes. The maximal enhancement reached a factor of 1.3–1.5. On the second and third days, the negative phase of the storm developed. The TEC decrease was registered regardless of time of the day. The TEC depression exceeded 70% relative to quiet days. On the following days (15 and 16 September, a significant daytime enhancement of TEC was observed once again. The complex occurrence of the ionospheric storm was probably related to the features of development of the magnetic storm. We found out that during the storm the large and medium-scale irregularities developed in the high-latitude ionosphere. The multi-stations technique, employed to create TEC maps, was particularly successful while studying the mid-latitude ionospheric trough. We found out that the essential changes of TEC during the storm, which were registered at the auroral and sub-auroral ionosphere, were connected with the effect of the trough and its dynamics, which depends on geomagnetic activity.

    Key words. Ionosphere (ionospheric disturbances; auroral ionosphere; mid-latitude ionosphere

  12. Performance evaluation of GNSS-TEC estimation techniques at the grid point in middle and low latitudes during different geomagnetic conditions

    Science.gov (United States)

    Abe, O. E.; Otero Villamide, X.; Paparini, C.; Radicella, S. M.; Nava, B.; Rodríguez-Bouza, M.

    2017-04-01

    Global Navigation Satellite Systems (GNSS) have become a powerful tool use in surveying and mapping, air and maritime navigation, ionospheric/space weather research and other applications. However, in some cases, its maximum efficiency could not be attained due to some uncorrelated errors associated with the system measurements, which is caused mainly by the dispersive nature of the ionosphere. Ionosphere has been represented using the total number of electrons along the signal path at a particular height known as Total Electron Content (TEC). However, there are many methods to estimate TEC but the outputs are not uniform, which could be due to the peculiarity in characterizing the biases inside the observables (measurements), and sometimes could be associated to the influence of mapping function. The errors in TEC estimation could lead to wrong conclusion and this could be more critical in case of safety-of-life application. This work investigated the performance of Ciraolo's and Gopi's GNSS-TEC calibration techniques, during 5 geomagnetic quiet and disturbed conditions in the month of October 2013, at the grid points located in low and middle latitudes. The data used are obtained from the GNSS ground-based receivers located at Borriana in Spain (40°N, 0°E; mid latitude) and Accra in Ghana (5.50°N, 0.20°E; low latitude). The results of the calibrated TEC are compared with the TEC obtained from European Geostationary Navigation Overlay System Processing Set (EGNOS PS) TEC algorithm, which is considered as a reference data. The TEC derived from Global Ionospheric Maps (GIM) through International GNSS service (IGS) was also examined at the same grid points. The results obtained in this work showed that Ciraolo's calibration technique (a calibration technique based on carrier-phase measurements only) estimates TEC better at middle latitude in comparison to Gopi's technique (a calibration technique based on code and carrier-phase measurements). At the same time

  13. NASA's GPS tracking system for Aristoteles

    Science.gov (United States)

    Davis, E. S.; Hajj, G.; Kursinski, E. R.; Kyriacou, C.; Meehan, T. K.; Melbourne, William G.; Neilan, R. E.; Young, L. E.; Yunck, Thomas P.

    1991-12-01

    NASA 's Global Positioning System (GPS) tracking system for Artistoteles receivers and a GPS flight receiver aboard Aristoteles is described. It will include a global network of GPS ground receivers and a GPS flight receiver aboard Aristoteles. The flight receiver will operate autonomously; it will provide real time navigation solutions for Aristoteles and tracking data needed by ESOC for operational control of the satellite. The GPS flight and ground receivers will currently and continuously track all visible GPS satellites. These observations will yield high accuracy differential positions and velocities of Aristoteles in a terrestrial frame defined by the locations of the globally distributed ground work. The precise orbits and tracking data will be made available to science investigators as part of the geophysical data record. The characteristics of the GPS receivers, both flight and ground based, that NASA will be using to support Aristoteles are described. The operational aspects of the overall tracking system, including the data functions and the resulting data products are summarized. The expected performance of the tracking system is compared to Aristoteles requirements and the need to control key error sources such as multipath is identified.

  14. The Synthesis of Ternary Acetylides with Tellurium: Li2TeC2 and Na2TeC2

    OpenAIRE

    Nemeth, Karoly; Unni, Aditya K.; Kalnmals, Christopher; Segre, Carlo U.; Kaduk, James

    2015-01-01

    The synthesis of ternary acetylides Li2TeC2 and Na2TeC2 is presented as the first example of ternary acetylides with metalloid elements instead of transition metals. The synthesis was carried out by the direct reaction of the corresponding bialkali acetylides with tellurium powder in liquid ammonia. Alternatively, the synthesis of Na2TeC2 was also carried out by the direct reaction of tellurium powder and two equivalents of NaC2H in liquid ammonia leading to Na2TeC2 and acetylene gas through ...

  15. Detection of ionospheric signatures from GPS-derived total electron content maps

    OpenAIRE

    Durgonics T.; Prates G.; Berrocoso M.

    2014-01-01

    The processing of measurement data from satellite constellations such as Global Navigation Satellite Systems (GNSS), including the well-known Global Positioning System (GPS), have been successfully applied to virtually all areas of geophysical sciences. In this work, a method is described where Geographical Information Systems (GIS) are employed to build hourly ionospheric Total Electron Content (TEC) maps for 2011 over the southern Iberian Peninsula. The maps used GPS...

  16. A method for separating seismo-ionospheric TEC outliers from heliogeomagnetic disturbances by using nu-SVR

    Energy Technology Data Exchange (ETDEWEB)

    Pattisahusiwa, Asis [Bandung Institute of Technology (Indonesia); Liong, The Houw; Purqon, Acep [Earth physics and complex systems research group, Bandung Institute of Technology (Indonesia)

    2015-09-30

    Seismo-Ionospheric is a study of ionosphere disturbances associated with seismic activities. In many previous researches, heliogeomagnetic or strong earthquake activities can caused the disturbances in the ionosphere. However, it is difficult to separate these disturbances based on related sources. In this research, we proposed a method to separate these disturbances/outliers by using nu-SVR with the world-wide GPS data. TEC data related to the 26th December 2004 Sumatra and the 11th March 2011 Honshu earthquakes had been analyzed. After analyzed TEC data in several location around the earthquake epicenter and compared with geomagnetic data, the method shows a good result in the average to detect the source of these outliers. This method is promising to use in the future research.

  17. Global Ionospheric Perturbations Monitored by the Worldwide GPS Network

    Science.gov (United States)

    Ho, C. M.; Mannucci, A. T.; Lindqwister, U. J.; Pi, X. Q.

    1996-01-01

    Based on the delays of these (Global Positioning System-GPS)signals, we have generated high resolution global ionospheric TEC (Total Electronic Changes) maps at 15-minute intervals. Using a differential method comparing storm time maps with quiet time maps, we find that the ionopshere during this time storm has increased significantly (the percentage change relative to quiet times is greater than 150 percent) ...These preliminary results (those mentioned above plus other in the paper)indicate that the differential maping method, which is based on GPS network measurements appears to be a useful tool for studying the global pattern and evolution process of the entire ionospheric perturbation.

  18. INEGI's Network of GPS permanent stations in Mexico

    Science.gov (United States)

    Gonzalez Franco, G. A.

    2013-05-01

    The Active National Geodetic Network administered by INEGI (Instituto Nacional de Estadística y Geografía) is a set of 24 GPS permanent stations in Mexico that was established in 1993 for a national rural cadastral project, its has been mainly used for geodetic surveys through Mexico including international borders, and has been progressing to contribute to national, regional and international reference frames through the delivering of GPS data or coordinate solutions from INEGI Processing Center to SIRGAS and NAREF. Recently GAMIT/GLOBK Processing of permanent stations in Mexico was realized from 2007-2011 to determine station's velocity. Related to natural hazards, a subset of INEGI network contributes to the project Real Time Integrated Atmosferic Water Wapor and TEC from GPS. The GPS network planned evolution consider changing to a GNSS network, adding stations to IGS, maintain the services of the present, and contribute to multidisciplinary geodetic studies through data publicly available.

  19. Detection of ionospheric signatures from GPS-derived total electron content maps

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Prates, G.; Berrocoso, M.

    2014-01-01

    Geographical Information Systems (GIS) are employed to build hourly ionospheric Total Electron Content (TEC) maps for 2011 over the southern Iberian Peninsula. The maps used GPS-derived geometryfree linear combinations attained from station data from the Algarve, Alentejo (Portugal), Andalusia, Murcia...

  20. On a reported effect in ionospheric TEC around the time of the 6 April 2009 L'Aquila earthquake

    Science.gov (United States)

    Masci, Fabrizio; Thomas, Jeremy N.; Secan, James A.

    2017-09-01

    In a report published in Advances in Space Research, Nenovski et al. (2015) analyse ionospheric TEC (total electron content) data from GPS measurements around the time of the 6 April 2009 Mw 6. 1 L'Aquila (Italy) earthquake. According to the authors, TEC difference (DTEC) calculated from two GPS (Global Positioning System) receivers in central Italy shows a hump-like shape (an increase followed by a decrease) during the hours just before and shortly after the main shock. They maintain that the hump-like shape is anomalous and may be related to the earthquake. We show that the DTEC increase in the hours before the shock, as well as its subsequent slow decrease, does not have any characteristic that might support a possible relationship with the earthquake. We have also conducted our own independent analysis using the same GPS data analysed by Nenovski et al. (2015). We have found a diurnal variation in DTEC time series that shows hump-like shapes like that reported by Nenovski et al. (2015) throughout the investigated period. This demonstrates that the hump-like shape in DTEC close to the time of the 6 April earthquake is not anomalous and cannot be considered a possible earthquake-related effect.

  1. Ground-based Space Weather Monitoring with LOFAR

    Science.gov (United States)

    Wise, Michael; van Haarlem, Michiel; Lawrence, Gareth; Reid, Simon; Bos, Andre; Rawlings, Steve; Salvini, Stef; Mitchell, Cathryn; Soleimani, Manuch; Amado, Sergio; Teresa, Vital

    As one of the first of a new generation of radio instruments, the International LOFAR Telescope (ILT) will provide a number of unique and novel capabilities for the astronomical community. These include remote configuration and operation, dynamic real-time processing and system response, and the ability to provide multiple simultaneous streams of data to a community whose scientific interests run the gamut from lighting in the atmospheres of distant planets to the origins of the universe itself. The LOFAR (LOw Frequency ARray) system is optimized for a frequency range from 30-240 MHz and consists of multiple antenna fields spread across Europe. In the Netherlands, a total 36 LOFAR stations are nearing completion with an initial 8 international stations currently being deployed in Germany, France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR has the potential to achieve unparalleled sensitivity and spatial resolution in the low frequency radio regime. LOFAR will also be one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. As we discuss in this presentation, the same capabilities that make LOFAR a powerful tool for radio astronomy also provide an excellent platform upon which to build a ground-based monitoring system for space weather events. For example, the ability to monitor Solar activity in near real-time is one of the key scientific capabilities being developed for LOFAR. With only a fraction of its total observing capacity, LOFAR will be able to provide continuous monitoring of the Solar spectrum over the entire 10-240 MHz band down to microsecond timescales. Autonomous routines will scan these incoming spectral data for evidence of Solar flares and be

  2. GPS for land surveyors

    CERN Document Server

    Van Sickle, Jan

    2008-01-01

    The GPS SignalGlobal Positioning System (GPS) Signal StructureTwo ObservablesPseudorangingCarrier Phase RangingBiases and SolutionsThe Error BudgetDifferencingThe FrameworkTechnological ForerunnersVery Long Baseline InterferometryTransitNavstar GPSGPS Segment OrganizationGPS ConstellationThe Control SegmentReceivers and MethodsCommon Features of GPS ReceiversChoosing a GPS ReceiverSome GPS Surveying MethodsCoordinatesA Few Pertinent Ideas About Geodetic Datums for GPSState Plane CoordinatesHeightsGPS Surveying TechniquesStatic GPS SurveyingReal-Time Kinematic (RTK) and Differential GPS (DGPS)T

  3. Gravity wave activity observed in the mesosphere and ionosphere on September 16th 2015 by an all-sky imager and dTEC maps over Brazil

    Science.gov (United States)

    Wrasse, Cristiano M.; Gobbi, Delano; Buriti, Ricardo; Bageston, José Valentin; Medeiros, Amauri; Paulino, Igo; Cosme Alexandre Figueiredo, M.; Takahashi, Hisao; Azambuja, Rodrigo

    2016-07-01

    All-sky imager was used to observe the wave activity in the mesosphere and a ground network of GPS receivers were used to make detrended Total Electron Content (dTEC) maps to monitor the ionosphere. The wave activity was observed on September 16th 2015 over the southeast region in Brazil. The gravity wave characteristics and the atmospheric conditions for wave propagation will be presented and discussed. The gravity wave source was associated with strong tropospheric convection.

  4. Geomagnetic Storm Main Phase effect on the Equatorial Ionosphere as measured from GPS observations at Ile-Ife

    Science.gov (United States)

    Olabode, Ayomide; Ariyibi, Emmanuel

    2016-07-01

    The effect of the main phase of two intense geomagnetic storm events which occurred on August 5-6 and September 26-27, 2011 on the equatorial ionosphere have been investigated using Global Positioning System (GPS) data obtained from an Ile-Ife station (geomagnetic lat. 9.84°N, long. 77.25°E). The WinTEC-P and GPS-TEC analysis software programs were used to process the GPS data to obtain Total Electron Content (TEC) and Scintillation Index (S4). TEC profiles during the main phase of the two geomagnetically disturbed days were compared with quiet time average profiles to examine the response of the equatorial ionosphere. International Reference Ionosphere (IRI) 2012 TEC model was also obtained from Virtual Ionosphere, Thermosphere, Mesosphere Observatory (VITMO) and the extents of deviation from measured GPS-derived TEC were examined for the main phase of the storm events. The results showed that the intensity of both storm events during the main phase which occurred at night-time correlated well with a strong southward direction of the z-component of the Interplanetary Magnetic Field (IMF-Bz) and Solar Wind Speed (Vsw), with the Disturbance storm time (Dst) profile showing multiple step development. TEC depletion was observed during the main phase of the August 5-6, 2011 storm event with TEC recording a maximum value of 9.31 TECU. A maximum TEC value of 55.8 TECU was recorded during the main phase of the September 26-27, 2011 storm event depicting TEC enhancement. Significant scintillation index value of 0.57 was observed when the main phase started on August 5-6, 2011 followed by a prolonged suppression while there was less significant scintillation impact on September 26-27, 2011 with a maximum value of 0.33. The study concluded that the intensification of the ring current during the main phase of geomagnetic storm events was responsible for the intensity of the storm events causing large variations in TEC and significant scintillation phenomenon.

  5. Aerial Prefeeding Followed by Ground Based Toxic Baiting for More Efficient and Acceptable Poisoning of Invasive Small Mammalian Pests.

    Directory of Open Access Journals (Sweden)

    David Morgan

    Full Text Available Introduced brushtail possums (Trichosurus vulpecula and rat species (Rattus spp. are major vertebrate pests in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Aerial distribution of baits containing sodium fluoroacetate (1080 has been refined to maximise cost effectiveness and minimise environmental impact, but this method is strongly opposed by some as it is perceived as being indiscriminate. Although ground based control enables precise placement of baits, operations are often more than twice as costly as aerial control, mainly due to the high labour costs. We investigated a new approach to ground based control that combined aerial distribution of non-toxic 'prefeed' baits followed by sparse distribution of toxic baits at regular intervals along the GPS tracked prefeeding flight paths. This approach was tested in two field trials in which both 1080 baits and cholecalciferol baits were used in separate areas. Effectiveness of the approach, assessed primarily using 'chewcards', was compared with that of scheduled aerial 1080 operations that were conducted in outlying areas of both trials. Contractors carrying out ground based control were able to follow the GPS tracks of aerial prefeeding flight lines very accurately, and with 1080 baits achieved very high levels of kill of possums and rats similar to those achieved by aerial 1080 baiting. Cholecalciferol was less effective in the first trial, but by doubling the amount of cholecalciferol bait used in the second trial, few possums or rats survived. By measuring the time taken to complete ground baiting from GPS tracks, we predicted that the method (using 1080 baits would be similarly cost effective to aerial 1080 operations for controlling possums and rats, and considerably less expensive than typical current costs of ground based control. The main limitations to the use of the method will be access to, and size of, the operational

  6. Aerial Prefeeding Followed by Ground Based Toxic Baiting for More Efficient and Acceptable Poisoning of Invasive Small Mammalian Pests.

    Science.gov (United States)

    Morgan, David; Warburton, Bruce; Nugent, Graham

    2015-01-01

    Introduced brushtail possums (Trichosurus vulpecula) and rat species (Rattus spp.) are major vertebrate pests in New Zealand, with impacts on conservation and agriculture being managed largely through poisoning operations. Aerial distribution of baits containing sodium fluoroacetate (1080) has been refined to maximise cost effectiveness and minimise environmental impact, but this method is strongly opposed by some as it is perceived as being indiscriminate. Although ground based control enables precise placement of baits, operations are often more than twice as costly as aerial control, mainly due to the high labour costs. We investigated a new approach to ground based control that combined aerial distribution of non-toxic 'prefeed' baits followed by sparse distribution of toxic baits at regular intervals along the GPS tracked prefeeding flight paths. This approach was tested in two field trials in which both 1080 baits and cholecalciferol baits were used in separate areas. Effectiveness of the approach, assessed primarily using 'chewcards', was compared with that of scheduled aerial 1080 operations that were conducted in outlying areas of both trials. Contractors carrying out ground based control were able to follow the GPS tracks of aerial prefeeding flight lines very accurately, and with 1080 baits achieved very high levels of kill of possums and rats similar to those achieved by aerial 1080 baiting. Cholecalciferol was less effective in the first trial, but by doubling the amount of cholecalciferol bait used in the second trial, few possums or rats survived. By measuring the time taken to complete ground baiting from GPS tracks, we predicted that the method (using 1080 baits) would be similarly cost effective to aerial 1080 operations for controlling possums and rats, and considerably less expensive than typical current costs of ground based control. The main limitations to the use of the method will be access to, and size of, the operational site, along with

  7. Ground-based observations of Kepler asteroseismic targets

    DEFF Research Database (Denmark)

    Uyttterhoeven , K.; Karoff, Christoffer

    2010-01-01

    We present the ground-based activities within the different working groups of the Kepler Asteroseismic Science Consortium (KASC). The activities aim at the systematic characterization of the 5000+ KASC targets, and at the collection of ground-based follow-up time-series data of selected promising...

  8. Storm time spatial variations in TEC during moderate geomagnetic storms in extremely low solar activity conditions (2007-2009) over Indian region

    Science.gov (United States)

    Sunda, Surendra; Vyas, B. M.; Khekale, P. V.

    2013-07-01

    The total electron content (TEC) measurements from a network of GPS receivers were analyzed to investigate the storm time spatial response of ionosphere over the Indian longitude sector. The GPS receivers from the GPS Aided Geo Augmented Navigation (GAGAN) network which are uniquely located around the ˜77°E longitude are used in the present study so as to get the complete latitudinal coverage from the magnetic equator to low mid-latitude region. We have selected the most intense storms but of moderate intensity (-100 nT extremely low solar activity conditions in 2007-2009. Though the storms are of moderate intensity, their effects on equatorial to low mid-latitude ionosphere are found to be very severe as TEC deviations are more than 100% during all the storms studied. Interesting results in terms of spatial distribution of positive/negative effects during the main/early recovery phase of storms are noticed. The maximum effect was observed at crest region during two storms whereas another two storms had maximum effect near the low mid-latitude region. The associated mechanisms like equatorial electrodynamics and neutral dynamics are segregated and explained using the TIMED/GUVI and EEJ data during these storms. The TEC maps are generated to investigate the storm time development/inhibition of equatorial ionization anomaly (EIA).

  9. Movable Ground Based Recovery System for Reuseable Space Flight Hardware

    Science.gov (United States)

    Sarver, George L. (Inventor)

    2013-01-01

    A reusable space flight launch system is configured to eliminate complex descent and landing systems from the space flight hardware and move them to maneuverable ground based systems. Precision landing of the reusable space flight hardware is enabled using a simple, light weight aerodynamic device on board the flight hardware such as a parachute, and one or more translating ground based vehicles such as a hovercraft that include active speed, orientation and directional control. The ground based vehicle maneuvers itself into position beneath the descending flight hardware, matching its speed and direction and captures the flight hardware. The ground based vehicle will contain propulsion, command and GN&C functionality as well as space flight hardware landing cushioning and retaining hardware. The ground based vehicle propulsion system enables longitudinal and transverse maneuverability independent of its physical heading.

  10. Synthesis and chemical etching of Te/C nanocables

    Indian Academy of Sciences (India)

    Guang Sheng Cao; Yong Gang Liu; Wen Wu Yang; Chang Tan; Hui Li; Xiao Juan Zhang

    2011-10-01

    In this paper, Te/C nanocables were fabricated by a hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). The products were characterized in detail by multiform techniques: transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis and Fourier transform infrared (FTIR) spectroscopy. The results showed that the products were nanocables with lengths of several microns, core about 20 nm in diameter, and a surrounding sheath of about 60–80 nm in thickness. Te/C nanocables were tailored freely by chemical etching. Carbonaceous nanotubes and Te/C nanocables with fragmentary Te core were obtained by adjusting time of chemical etching.

  11. Seismo-ionospheric Precursors in the GPS Total Electron Content of the 16 October 1999 Mw7.1 Hector Mine Earthquake

    Science.gov (United States)

    Tsai, H.; Su, Y.; Liu, J. G.; Chen, S.; Chen, M.

    2013-12-01

    In this paper, temporal and spatial analyses are employed to detect seismo-ionospheric precursors (SIPs) in the ionospheric total electron content (TEC) during 16 October 1999 Mw7.1 Hector Mine earthquake. To discriminate anomalies caused by global effects, such as solar radiations, magnetic storms, etc., and local effects, such as earthquake, we cross-examine the GPS TECs and their gradients in the eastward and northward directions at epicenter/centers of the Hector Mine area and the other two reference areas at similar magnetic latitudes in Europe and Japan. Temporal variations of the northward TEC gradient suggest SIPs most likely appearing day 6-5 before the earthquake. A global search by using the TEC of GIM (global ionosphere map) shows that the TEC increase and decrease anomalies continuously and specifically appear around the epicenter day 5 before the earthquake.

  12. A comparison of TEC predicted by IRI-2012 with that measured at three different stations in low latitude Indian region for the years (2010-2012)

    Science.gov (United States)

    Karia, S. P.; Patel, N. C.; Pathak, K. N.

    2017-07-01

    The present study reports the comparison of GPS measured Total Electron Content (TEC) with that predicted by the latest IRI-2012 model at three different stations located within the Equatorial Ionization Anomaly region (EIA) in the Indian sector. The data used for the study are retrieved from three different stations, namely, Surat (geographic latitude 21.16°N, geographic longitude 72.78°E; geomagnetic latitude 12.90°N), Hyderabad (geographic latitude 17.25°N, geographic longitude 78.30°E; geomagnetic latitude 8.65°N) and Bangalore (geographic latitude 13.02°N, geographic longitude 77.57°E; geomagnetic latitude 4.58°N). The period of comparison is three years for rising solar activity from 2010 to 2012. Here it is to note that both Hyderabad and Bangalore are IGS station with the station code (HYDE and IISC respectively). The results for the comparison of seasonal variation shows a good agreement between the measured and modeled TEC for all seasons with deviation of (±15 TECU) for all three years at Surat and Bangalore and with a deviation of (±25 TECU) at Hyderabad. Both topside options NeQuick and IRI01-Corr derived nearly equal TEC at all three stations. It is observed that the GPS TEC data shows the EIA crest at (23.5°N) where as the IRI TEC predicts the EIA crest at (19.7°N) on an average for all the years 2010-2012.

  13. Thermo-ecological cost (TEC evaluation of metallurgical processes

    Directory of Open Access Journals (Sweden)

    W. Stanek

    2015-01-01

    Full Text Available Metallurgy represents a complex production system of fuel and mineral non-renewable resources transformation. The effectiveness of resource management in metallurgical chains depends on the applied ore grade and on the irreversibility of components of the system. TEC can be applied to measure the influence of metallurgy on the depletion of natural resources. The paper discusses the possibility of application of TEC in metallurgy and presents illustrative example concerning blast-furnace process.

  14. TEC protein tyrosine kinase is involved in the Erk signaling pathway induced by HGF

    Energy Technology Data Exchange (ETDEWEB)

    Li, Feifei; Jiang, Yinan [Department of Pathophysiology, Anhui Medical University, Hefei 230032 (China); Zheng, Qiping [Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, IL 60612 (United States); Yang, Xiaoming [Institute of Radiation Medicine, Academy of Military Medical Sciences, Beijing 100850 (China); Wang, Siying, E-mail: sywang@ahmu.edu.cn [Department of Pathophysiology, Anhui Medical University, Hefei 230032 (China)

    2011-01-07

    Research highlights: {yields} TEC is rapidly tyrosine-phosphorylated and activated by HGF-stimulation in vivo or after partial hepatectomy in mice. {yields} TEC enhances the activity of Elk and serum response element (SRE) in HGF signaling pathway in hepatocyte. {yields} TEC promotes hepatocyte proliferation through the Erk-MAPK pathway. -- Abstract: Background/aims: TEC, a member of the TEC family of non-receptor type protein tyrosine kinases, has recently been suggested to play a role in hepatocyte proliferation and liver regeneration. This study aims to investigate the putative mechanisms of TEC kinase regulation of hepatocyte differentiation, i.e. to explore which signaling pathway TEC is involved in, and how TEC is activated in hepatocyte after hepatectomy and hepatocyte growth factor (HGF) stimulation. Methods: We performed immunoprecipitation (IP) and immunoblotting (IB) to examine TEC tyrosine phosphorylation after partial hepatectomy in mice and HGF stimulation in WB F-344 hepatic cells. The TEC kinase activity was determined by in vitro kinase assay. Reporter gene assay, antisense oligonucleotide and TEC dominant negative mutant (TEC{sup KM}) were used to examine the possible signaling pathways in which TEC is involved. The cell proliferation rate was evaluated by {sup 3}H-TdR incorporation. Results: TEC phosphorylation and kinase activity were increased in 1 h after hepatectomy or HGF treatment. TEC enhanced the activity of Elk and serum response element (SRE). Inhibition of MEK1 suppressed TEC phosphorylation. Blocking TEC activity dramatically decreased the activation of Erk. Reduced TEC kinase activity also suppressed the proliferation of WB F-344 cells. These results suggest TEC is involved in the Ras-MAPK pathway and acts between MEK1 and Erk. Conclusions: TEC promotes hepatocyte proliferation and regeneration and is involved in HGF-induced Erk signaling pathway.

  15. 基于 GPSTk 的区域电离层 TEC 地图重构%The Regional Ionospheric TEC Map Reconstruction Based on GPSTk Sof tware

    Institute of Scientific and Technical Information of China (English)

    王志钢; 欧明

    2015-01-01

    Ionospheric delay is one of the most important resources in satellite navigation systems ,and TEC map reconstruction is the major way to eliminate the delay effect of the satellite navigation systems .As an important tool for GPS data processing ,GPSTk software can be used to fulfill the requirement of the T EC map reconstruction .Based on the analysis of the characteristic of GPSTk ,the principle of the TEC calculation ,the flowchart of the da‐ta processing and the operational approach of the GPSTk were demonstrated in this paper , which will be helpful in the development of the GPS‐based software for ionospheric data pro‐cessing .%电离层是影响卫星导航系统传输时延的重要因素之一,电离层总电子含量(TEC)地图重构是消除电离层传输时延的重要手段。GPSTk作为GPS数据处理的重要软件之一,可以满足区域电离层 TEC地图的重构要求。本文针对 GPSTk的特点,深入研究了GPSTk的电离层TEC计算原理、数据处理流程及具体的软件操作方法,该研究对基于GPS数据的电离层数据处理软件的研制具有一定的参考意义。

  16. CFD Extraction Tool for TecPlot From DPLR Solutions

    Science.gov (United States)

    Norman, David

    2013-01-01

    This invention is a TecPlot macro of a computer program in the TecPlot programming language that processes data from DPLR solutions in TecPlot format. DPLR (Data-Parallel Line Relaxation) is a NASA computational fluid dynamics (CFD) code, and TecPlot is a commercial CFD post-processing tool. The Tec- Plot data is in SI units (same as DPLR output). The invention converts the SI units into British units. The macro modifies the TecPlot data with unit conversions, and adds some extra calculations. After unit conversions, the macro cuts a slice, and adds vectors on the current plot for output format. The macro can also process surface solutions. Existing solutions use manual conversion and superposition. The conversion is complicated because it must be applied to a range of inter-related scalars and vectors to describe a 2D or 3D flow field. It processes the CFD solution to create superposition/comparison of scalars and vectors. The existing manual solution is cumbersome, open to errors, slow, and cannot be inserted into an automated process. This invention is quick and easy to use, and can be inserted into an automated data-processing algorithm.

  17. Comparison of ionospheric characteristic parameters obtained by GPS and ionosonde with IRI model over China

    Indian Academy of Sciences (India)

    Cheng Wang

    2016-06-01

    This paper presents a comparison of ionospheric characteristic parameters obtained by a GPS networkand three ionosondes at Mohe (122.4^◦E, 53.5^◦N, dip angle 70.983^◦N), Zuolingzhen (114.6^◦E, 30.5^◦N, dipangle 46.350^◦N), and Fuke (109.1^◦E, 19.5^◦N, dip angle 27.083^◦N) located in China with an IRI model inthe year 2011. Observed NmF2 and hmF2 values at the three stations are compared with IRI2007 andIRI2012 predictions, respectively. The results show that there are clear linear correlations between theobserved values and the IRI model predicted values. The IRI model gives overestimations at the threestations mostly in 2011. For the NmF2 and hmF2 values, most of the results show that the IRI2012predicted values are closer to the observed values compared with those of IRI2007. Additionally, theGPS TEC values derived from the Crustal Movement Observation Network of China (CMONOC) arecompared with the IRI2012 predictions. From the results, it is evident that the IRI2012 model predictionsfollow the normal trend of diurnal variation of GPS measured TEC monthly means but do not reproducethe measured data well. The IRI2012 model overestimates electron density in the latter part of spring aswell as the first half of autumn and winter and underestimates electron density in early spring and thelatter part of autumn. Referring to GPS TEC, the precision of the IRI2012 model predicted TEC valuesis ∼5 TECU over China. It may also be noted that there are two discontinuities of IRI-TEC monthlymeans appearing in November and December of the year 2011. This brings a bias of ∼3 TECU of TECvalues between two adjacent months.

  18. GPS Array as a Sensor of Lithosphere, Troposphere and Ionosphere

    Science.gov (United States)

    Heki, K.

    2011-12-01

    precipitable water vapor (PWV) of troposphere. After intense feasibility studies of GPS meteorology in 1990s, PWV information from GEONET has been routinely assimilated in the operational mesoscale model of the Japan Meteorological Agency since 2009. It is found useful in predicting localized heavy rainfalls that often attack Japan in summer. It is fairly easy to measure ionospheric total electron content (TEC) by using phase differences between L1 and L2 carriers from GPS satellites. Applications of GPS for upper atmospheric studies started for ionospheric disturbances of space weather origins. In 2003, clear coseismic ionospheric disturbances of the Tokachi-Oki earthquake were found, and the GPS-TEC technique has been extensively used to study ionospheric disturbances of solid earth origins, e.g. earthquakes and volcanic eruptions. There are also several recent examples of artificial ionospheric disturbances caused by rocket launches and passage of ballistic missiles from North Korea above NE Japan. In the last part of the lecture, I summarize what the GPS array saw before, during and after the 2011 Tohoku-Oki earthquake. The topic covers not only pre-, co- and postseismic crustal movements, but also results of high-rate sampling, and possible detection of precursory changes in ionospheric TEC immediately before the earthquake.

  19. Kalman filter-based algorithms for monitoring the ionosphere and plasmasphere with GPS in near-real time

    Science.gov (United States)

    Anghel, Adela; Carrano, Charles; Komjathy, Attila; Astilean, Adina; Letia, Tiberiu

    2009-01-01

    Data collected from a GPS receiver located at low latitudes in the American sector are used to investigate the performance of the WinTEC algorithm [Anghel et al., 2008a, Kalman filter-based algorithm for near realtime monitoring of the ionosphere using dual frequency GPS data. GPS Solutions, accepted for publication; for different ionospheric modeling techniques: the single-shell linear, quadratic, and cubic approaches, and the multi-shell linear approach. Our results indicate that the quadratic and cubic approaches perform much better than the single-shell and multi-shell linear approaches in terms of post-fit residuals. The performance of the algorithm for the cubic approach is then further tested by comparing the vertical TEC predicted by WinTEC and USTEC [Spencer et al., 2004. Ionospheric data assimilation methods for geodetic applications. In: Proceedings of IEEE PLANS, Monterey, CA, 26-29 April, pp. 510-517] at five North American stations. In addition, since the GPS-derived total electron content (TEC) contains contributions from both ionospheric and plasmaspheric sections of the GPS ray paths, in an effort to improve the accuracy of the TEC retrievals, a new data assimilation module that uses background information from an empirical plasmaspheric model [Gallagher et al., 1988. An empirical model of the Earth's plasmasphere. Advances in Space Research 8, (8)15-(8)24] has been incorporated into the WinTEC algorithm. The new Kalman filter-based algorithm estimates both the ionospheric and plasmaspheric electron contents, the combined satellite and receiver biases, and the estimation error covariance matrix, in a single-site or network solution. To evaluate the effect of the plasmaspheric component on the estimated biases and total TEC and to assess the performance of the newly developed algorithm, we compare the WinTEC results, with and without the plasmaspheric term included, at three GPS receivers located at different latitudes in the American sector, during

  20. Similarity and differences in morphology and mechanisms of the foF2 and TEC disturbances during the geomagnetic storms on 26-30 September 2011

    Science.gov (United States)

    Klimenko, Maxim V.; Klimenko, Vladimir V.; Zakharenkova, Irina E.; Ratovsky, Konstantin G.; Korenkova, Nina A.; Yasyukevich, Yury V.; Mylnikova, Anna A.; Cherniak, Iurii V.

    2017-08-01

    This study presents an analysis of the ground-based observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American) during geomagnetic storms that occurred on 26-30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC) and the ionospheric F2 peak critical frequency (foF2) during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800-20 000 km) at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O) / n(N2) enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

  1. Long-term ionospheric anomaly monitoring for ground based augmentation systems

    Science.gov (United States)

    Jung, Sungwook; Lee, Jiyun

    2012-08-01

    Extreme ionospheric anomalies can pose a potential integrity threat to ground-based augmentation of the Global Positioning System (GPS), and thus the development of ionospheric anomaly threat models for each region of operation is essential for system design and operation. This paper presents a methodology for automated long-term ionospheric anomaly monitoring, which will be used to build an ionospheric anomaly threat model, evaluate its validity over the life cycle of the system, continuously monitor ionospheric anomalies, and update the threat model if necessary. This procedure automatically processes GPS data collected from external networks and estimates ionospheric gradients at regular intervals. If ionospheric gradients large enough to be potentially hazardous to users are identified, manual data examination is triggered. This paper also develops a simplified truth processing method to create precise ionospheric delay estimates in near real-time, which is the key to automating the ionospheric monitoring procedure. The performance of the method is examined using data from the 20 November 2003 and 9 November 2004 ionospheric storms. These results demonstrate the effectiveness of simplified truth processing within long-term ionosphere monitoring. From the case studies, the automated procedure successfully identified extreme ionospheric anomalies, including the two worst ionospheric gradients observed and validated previously based on manual analysis. The automation of data processing enables us to analyze ionospheric data continuously going forward and to more accurately categorize ionospheric behavior under both nominal and anomalous conditions.

  2. Saved by Iridium? An Alternative to GPS

    Science.gov (United States)

    2012-05-17

    Groups of GPS Vulnerabilities Hostile Attacks Controllable Risks Other Vulnerabilities Direct or Kinetic Environmental Effects Self-Induced Directed...Constellation GONASS GALILEO BEIDOU-2 IRNSS GROUND BASED RADIO NAVIGATION LORAN LACATA VHF DME INS AUTOMATIC NAVIGATION TERCOM DESMAC PTAN Radio...0 0 1 0 1 LACATA 0 0 1 1 0 2 VHF 0 1 1 1 0 3 DME 0 1 1 1 0 3 INS 0 0 1 1 1 3 AUTOMATIC NAVIGATION TERCOM 0 0 1 1 1 3 DESMAC 0 0 1 1 1 3 PTAN 0

  3. GOCE gradiometer validation by GPS

    Science.gov (United States)

    Visser, P. N. A. M.

    The upcoming European Space Agency (ESA) Gravity Field and Steady-State Ocean Circular Explorer (GOCE) mission, foreseen to be launched in 2007 (status: July 2006) will carry a highly sensitive gradiometer, consisting of three orthogonal pairs of ultra-sensitive accelerometers. A challenging calibration procedure has been developed to calibrate the gradiometer not only pre-launch by a series of on-ground tests, but also after launch by making use of on-board cold-gas thrusters to provoke a long series of gradiometer shaking events which will provide observations for its calibration. In addition, a number of quick-look post-launch methods has been designed and will be implemented that aim at validating the calibration of the gradiometer instrument and at the same time support the operations of the satellite. These methods are based on (1) comparison with the best available global gravity field models, (2) upward continuation of high-precision ground-based gravity field data over certain geographical areas, and (3) use of GPS Satellite-to-Satellite Tracking (SST) observations. The focus of this paper is on the third method. An assessment has been made of how well the gradiometer observations can be validated by a combination with GPS tracking observations of GOCE. It was found by a detailed simulation study that the most important parameters, the scale factors of the diagonal gravity gradient components, can be determined with an accuracy better than 0.004, provided a nominal behavior of the gradiometer and GPS instruments.

  4. IONOSPHERIC CORRECTION METHOD FOR PRECISE POSITIONING WITH GPS ACTIVE NETWORK

    Institute of Scientific and Technical Information of China (English)

    GAOShan; CHENWu; HUCong-wei; CHENYong-qi; DINGXiao-li

    2005-01-01

    The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.

  5. Association of Total Electron Content (TEC and foF2 variations with earthquake events at the anomaly crest region

    Directory of Open Access Journals (Sweden)

    A. Depueva

    2004-06-01

    Full Text Available The paper attempts to identify ionospheric parameters in association with earthquake at anomaly crest station through VHF Radio Beacon data and ground based ionosonde measurements while the Total Electron Content(TEC parameters from RB observations are based mainly on data taken over Guwahati (26.2°N, 91.75° E, foF2 data used in the analysis were collected at Ahmadabad (23.01°N, 72.36°E. The paper describes methods and techniques adopted to examine modifications on these parameters if any, due to earthquake preparatory processes at equatorial anomaly crest stations. The mechanism of inducement of density changes in the ionosphere is sought through the generation of strong fountain effect possibly by the development of electric field during the earthquake preparatory process.

  6. GPS Separator HD

    CERN Multimedia

    2016-01-01

    Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.

  7. GPS Satellite Simulation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The GPS satellite simulation facility consists of a GPS satellite simulator controlled by either a Silicon Graphics Origin 2000 or PC depending upon unit under test...

  8. GPS Control Segment

    Science.gov (United States)

    2015-04-29

    Luke J. Schaub Chief, GPS Control Segment Division 29 Apr 15 GPS Control Segment Report Documentation Page Form ApprovedOMB No. 0704-0188...00-2015 4. TITLE AND SUBTITLE GPS Control Segment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT...Center, GPS Control Segment Division,Los Angeles AFB, El Segundo,CA,90245 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S

  9. GPS pseudolites: Theory, design, and applications

    Science.gov (United States)

    Cobb, H. Stewart

    Pseudolites (ground-based pseudo-satellite transmitters) can initialize carrier-phase differential GPS (CDGPS) navigation systems in seconds to perform real-time dynamic positioning with one-sigma errors as low as 1 cm. Previous CDGPS systems were rarely used due to cumbersome initialization procedures requiring up to 30 minutes; initialization of the carrier-phase integer ambiguities via pseudolite removes these constraints. This work describes pseudolites optimized for this application which cost two orders of magnitude less than previous pseudolites. Synchrolites (synchronized pseudolites) which derive their timing from individual Global Positioning System (GPS) satellites are also described. Synchrolites can replace the CDGPS reference station and datalink, while simultaneously serving to initialize CDGPS navigation. A cluster of well-placed synchrolites could enable CDGPS navigation even if only one GPS satellite signal is available. A prototype CDGPS system initialized by pseudolites and synchrolites was designed and tested. The goal of this system, known as the Integrity Beacon Landing System (IBLS), was to provide navigation accurate and reliable enough to land aircraft in bad weather. Flight test results for prototype pseudolite and synchrolite systems, including results from 110 fully automatic landings of a Boeing 737 airliner controlled by IBLS, are presented. Existing pseudolite applications are described, including simulation of the GPS constellation for indoor navigation experiments. Synchrolite navigation algorithms are developed and analyzed. New applications for pseudolites and synchrolites are proposed. Theoretical and practical work on the near/far problem is presented.

  10. GLOBAL POSITIONING SYSTEM (GPS

    Directory of Open Access Journals (Sweden)

    Celalettin Karaali

    1996-02-01

    Full Text Available Use of GPS is becoming more widespread on surveying engineering. Especially, preference to GPS is increased by getting accuracy of order of milimeter, making observation on every weather forecast, without requiring intervisibility between station. Besides, developing new observation techniques and technologies in GPS increased its use in deformation easurements, monitoring crustal movements, mapping precise geoid maps, detail surveying, etc.

  11. AUTOSCALA software improvements: topside-plasmasphere profiles and TEC model assisted by AIS ionosonde measurements

    Science.gov (United States)

    Cesaroni, C.; Ippolito, A.; Scotto, C.; Ciraolo, L.

    2012-12-01

    The group of Upper Atmosphere Physics at INGV (Istituto Nazionale di Geofisica e Vulcanologia) developed Autoscala, a computer program for automatic scaling of the critical frequency foF2 and other ionospheric parameters derived from ionograms. Autoscala includes a routine that automatically estimates the electron density profile below F layer peak height hmF2, by adjusting the parameters of a model according to the recorded ionogram [Scotto (2009)]. Recently we have introduced a new algorithm for modeling upper ionosphere and plasmasphere electron density profiles following the approach suggested by Kutiev et al. (2009). In particular, these model uses the parameters of F layer peak (foF2, hmF2, scale height at hmF2) to obtain scale heights that are useful to construct H- and O+ density profiles, and consequently N(h) profile (given as the sum of the former two). Integrating electron density profiles we are then able to obtain a real time TEC estimation above the considered ionospheric station. A first validation of the model is carried out for data measured at Rome ionospheric station (Italy, 41°54' N 12°28' E) using independent TEC measurements from GPS receivers. References: Scotto, C. (2009). Electron density profile calculation technique for Autoscala ionogram analysis. Advances in Space Research, 44(6), 756-766. doi:10.1016/j.asr.2009.04.037 Kutiev, I., Marinov, P., Belehaki, a., Reinisch, B., & Jakowski, N. (2009). Reconstruction of topside density profile by using the topside sounder model profiler and digisonde data. Advances in Space Research, 43(11), 1683-1687. doi:10.1016/j.asr.2008.08.017

  12. GLAST and Ground-Based Gamma-Ray Astronomy

    Science.gov (United States)

    McEnery, Julie

    2008-01-01

    The launch of the Gamma-ray Large Area Space Telescope together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.

  13. GLAST and Ground-Based Gamma-Ray Astronomy

    Science.gov (United States)

    McEnery, Julie

    2008-01-01

    The launch of the Gamma-ray Large Area Space Telescope together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.

  14. Representation of storms effects in IRI: NmF2, variability, TEC

    Science.gov (United States)

    Araujo-Pradere, Eduardo

    An improved understanding of the physics of the ionospheric response has enabled the recent success in the development of empirical models of the ionospheric behavior during geomagnetic disturbed conditions. One of them, the STORM Time Empirical Ionospheric Correction Model, has been included in the International Reference Ionosphere (IRI) since 2000. STORM, whose design includes the seasonal dependence in the migration of the composition bulge by the global wind field, and a non-linear dependence of the integrated time-history of ap, scales the quiettime F-layer critical frequency (peak concentration) to account for storm-time changes in the ionosphere. The successful insertion of STORM in IRI has been extensively validated, with improvement of up to 50 Advances in the understanding of the ionospheric variability under quiet and disturbed conditions have also been reached. However, IRI currently does not include estimates of the uncertainty (variability) surrounding the mean values. To address this void, an extensive ionosonde database covering a full solar cycle, similar to the one used to built the STORM model, was collected and binned by local time, latitude and season. For each bin, the mean, the standard deviation and the population distribution have been obtained for varying levels of magnetic activity. For periods where data were scarce or nonexistent, an estimated variability has been determined on the basis of expectations of the consequences of the physical processes. The information obtained from this approach could be the foundation for the development of an empirical variability model to be included in IRI. Although currently less well understood, the behavior of the Total Electron Content (TEC) is been examined by many groups, and some advances have already been made. With this purpose, GPS data over the contiguous US (CONUS), covering a series of 10-day storm periods with good seasonal coverage, was collected. The vertical TEC was extracted using a

  15. Solar activity variability in the IRI at high latitudes: Comparisons with GPS total electron content

    Science.gov (United States)

    Themens, David R.; Jayachandran, P. T.

    2016-04-01

    Total electron content (TEC) measurements from 10 dual-frequency GPS receivers in the Canadian High Arctic Ionospheric Network (CHAIN) are used to evaluate the performance of International Reference Ionosphere (IRI)-2007 within the Canadian sector. Throughout the region, we see systematic underestimation of daytime TEC, particularly at solar maximum, where summer and equinox root-mean-square errors reach as high as 14 total electron content units, 1 TECU = 1016 el m-2 (TECU). It is also shown that the use of a monthly IG index, in place of the IRI's standard IG12 index, leads to an improvement in TEC specification by up to 3 TECU in the polar cap and up to 6 TECU in the subauroral region during periods of short-term, large amplitude changes in solar activity. On diurnal timescales, variability in TEC is found to be underestimated by the IRI, during equinox periods, by up to 40% at subauroral latitudes and up to 70% in the polar cap region. During the winter, diurnal variations are overestimated by up to 40% in the subauroral region and are underestimated within the polar cap by up to 80%. Using collocated ionosonde data, we find IRI bottomside TEC to be within 1 TECU of observation with errors largest during the equinoxes. For the topside we find good agreement during the winter but significant underestimation of topside TEC by the IRI during summer and equinox periods, exceeding 6 TECU at times. By ingesting measured NmF2 into the IRI, we show that the topside thickness parameterization is the source of the bulk of the observed TEC errors.

  16. On a reported effect in ionospheric TEC around the time of the 6 April 2009 L'Aquila earthquake

    Directory of Open Access Journals (Sweden)

    F. Masci

    2017-09-01

    Full Text Available In a report published in Advances in Space Research, Nenovski et al. (2015 analyse ionospheric TEC (total electron content data from GPS measurements around the time of the 6 April 2009 Mw 6. 1 L'Aquila (Italy earthquake. According to the authors, TEC difference (DTEC calculated from two GPS (Global Positioning System receivers in central Italy shows a hump-like shape (an increase followed by a decrease during the hours just before and shortly after the main shock. They maintain that the hump-like shape is anomalous and may be related to the earthquake. We show that the DTEC increase in the hours before the shock, as well as its subsequent slow decrease, does not have any characteristic that might support a possible relationship with the earthquake. We have also conducted our own independent analysis using the same GPS data analysed by Nenovski et al. (2015. We have found a diurnal variation in DTEC time series that shows hump-like shapes like that reported by Nenovski et al. (2015 throughout the investigated period. This demonstrates that the hump-like shape in DTEC close to the time of the 6 April earthquake is not anomalous and cannot be considered a possible earthquake-related effect.

  17. GPS Scintillation Analysis.

    Science.gov (United States)

    2007-11-02

    Rev. 2-89) Prescribed by ANSI Std. Z39-1 298-102 TABLE OF CONTENTS 1. INTRODUCTION 1 2. GPS COMPARISON WITH ALL-SKY IMAGES OVER AGUA VERDE...Depletions from 1 October 1994 2 3. GPS data from Agua Verde, Chile on the night of 1 October 1994 3 4. PL-SCINDA display of GPS ionospheric...comparison of GPS measurements with GOES8 L-band scintillation data, are discussed. 2. GPS COMPARISON WITH ALL-SKY IMAGES OVER AGUA VERDE, CHILE As

  18. GPS Control Segment Improvements

    Science.gov (United States)

    2015-04-29

    Systems Center GPS Control Segment Improvements Mr. Tim McIntyre GPS Product Support Manager GPS Ops Support and Sustainment Division Peterson...DATE 29 APR 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE GPS Control Segment Improvements 5a. CONTRACT...ORGANIZATION NAME(S) AND ADDRESS(ES) Air Force Space Command,Space and Missile Systems Center, GPS Ops Support and Sustainment Division,Peterson AFB,CO,80916 8

  19. Global Empirical Model of the TEC Response to Geomagnetic Activity and Forcing from Below

    Science.gov (United States)

    2014-04-01

    AFRL-AFOSR-UK-TR-2014-0025 Global empirical model of the TEC response to geomagnetic activity and forcing from below Dora...April 2014 4. TITLE AND SUBTITLE Global empirical model of the TEC response to geomagnetic activity and forcing from below 5a. CONTRACT NUMBER...the global background TEC model c) Development of global empirical model of TEC response to geomagnetic activity d) On-line implementation of both

  20. GPS Modernization Update

    Science.gov (United States)

    2014-06-01

    space vehicles currently set healthy • 6 GPS IIA, 12 GPS IIR , 7 GPS IIR -M, 5 GPS IIF – 5 additional satellites in residual status, 1 in test status...Advisory Board Final.pptx S P A C E A N D M I S S I L E S Y S T E M S C E N T E R Legacy GPS IIA/ IIR • Single Frequency (L1) • Coarse...acquisition (C/A) code • Y-Code (L1Y & L2Y) GPS IIR -M • 2nd Civil Signal (L2C) • M-Code (L1M & L2M) GPS IIF • 3rd civil signal (L5) • 2 Rb + 1 Cs

  1. Ingestion of FORMOSAT-3/COSMIC GPS data into La Plata Ionospheric Model: A preliminary assessment

    Science.gov (United States)

    Conte, J. Federico; Brunini, Claudio

    2017-08-01

    La Plata Ionospheric Model (LPIM; Brunini et al., 2011) has been upgraded to a new stage enabling the ingestion of sTEC values retrieved from GPS receivers on board the FORMOSAT-3 Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites, in order to determine corrections to the global mean values of the ionosphere F2 layer critical frequency, fo F 2 (related to the peak density, Nm F 2) and the F2 layer peak height, hm F 2 .

  2. Industrial Maintenance Technology (IM-TEC). Student Manual.

    Science.gov (United States)

    Fusch, Gene E.

    This student manual explains an innovative strategy through which Bellingham Technical College's (Washington) evening Industrial Electrician and Millwright Apprenticeships were aggregated with workforce upgrade course offerings to form the college's first evening degree program in Industrial Maintenance Technology (IM-TEC). Section 1 contains a…

  3. V-TECS Guide for Bookkeeping/Accounting/Payroll Clerk.

    Science.gov (United States)

    Gregory, Margaret R.; Benson, Robert T.

    This guide, an extension of the Vocational-Technical Education Consortium of States (V-TECS) catalog, includes such considerations as background information, decision-making skills, attitudes, and learning methods surrounding the occupations of bookkeeper/accountant/payroll clerk. The guide provides job-relevant task, performance objectives,…

  4. C-TEC: Ohio's First All-Green School

    Science.gov (United States)

    Krall, Angie

    2009-01-01

    In Ohio's Licking County, the Career and Technology Education Centers (C-TEC) is a leader in the green movement. This eco-friendly school incorporates environmental sustainability in all aspects of its programming and is the first Leadership in Energy and Environmental Design (LEED)-certified public building in the state. While eco-friendly…

  5. Te/C nanocomposites for Li-Te Secondary Batteries

    National Research Council Canada - National Science Library

    Seo, Jeong-Uk; Seong, Gun-Kyu; Park, Cheol-Min

    2015-01-01

    ... (ca. 550 mA h cm(-3) at 5C rate). The mechanically reduced Te/C nanocomposite electrodes were found to be suitable for use as either the cathode in Li-Te secondary batteries or a high-potential anode in rechargeable Li-ion batteries...

  6. Te/C nanocomposites for Li-Te Secondary Batteries.

    Science.gov (United States)

    Seo, Jeong-Uk; Seong, Gun-Kyu; Park, Cheol-Min

    2015-01-22

    New battery systems having high energy density are actively being researched in order to satisfy the rapidly developing market for longer-lasting mobile electronics and hybrid electric vehicles. Here, we report a new Li-Te secondary battery system with a redox potential of ~1.7 V (vs. Li(+)/Li) adapted on a Li metal anode and an advanced Te/C nanocomposite cathode. Using a simple concept of transforming TeO2 into nanocrystalline Te by mechanical reduction, we designed an advanced, mechanically reduced Te/C nanocomposite electrode material with high energy density (initial discharge/charge: 1088/740 mA h cm(-3)), excellent cyclability (ca. 705 mA h cm(-3) over 100 cycles), and fast rate capability (ca. 550 mA h cm(-3) at 5C rate). The mechanically reduced Te/C nanocomposite electrodes were found to be suitable for use as either the cathode in Li-Te secondary batteries or a high-potential anode in rechargeable Li-ion batteries. We firmly believe that the mechanically reduced Te/C nanocomposite constitutes a breakthrough for the realization and mass production of excellent energy storage systems.

  7. Preliminary Results of 4-D Water Vapor Tomography in the Troposphere Using GPS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Slant-path water vapor amounts (SWV) from a station to all the GPS (Global Positioning System)satellites in view can be estimated by using a ground-based GPS receiver. In this paper, a tomographic method was utilized to retrieve the local horizontal and vertical structure of water vapor over a local GPS receiver network using SWV amounts as observables in the tomography. The method of obtaining SWV using ground-based GPS is described first, and then the theory of tomography using GPS is presented.A water vapor tomography experiment was made using a small GPS network in the Beijing region. The tomographic results were analyzed in two ways: (1) a pure GPS method, i.e., only using GPS observables as input to the tomography; (2) combining GPS observables with vertical constraints or a priori information,which come from average radiosonde measurements over three days. It is shown that the vertical structure of water vapor is well resolved with a priori information. Comparisons of profiles between radiosondes and GPS show that the RMS error of the tomography is about 1-2 mm. It is demonstrated that the tomography can monitor the evolution of tropospheric water vapor in space and time. The vertical resolution of the tomography is tested with layer thicknesses of 600 m, 800 m and 1000 m. Comparisons with radiosondes show that the result from a resolution of 800 m is slightly better than results from the other two resolutions in the experiment. Water vapor amounts recreated from the tomography field agree well with precipitable water vapor (PWV) calculated using GPS delays. Hourly tomographic results are also shown using the resolution of 800 m. Water vapor characteristics under the background of heavy rainfall development are analyzed using these tomographic results. The water vapor spatio-temporal structures derived from the GPS network show a great potential in the investigation of weather disasters.

  8. Ground-based Light Curves Two Pluto Days Before the New Horizons Passage

    Science.gov (United States)

    Bosh, A. S.; Pasachoff, J. M.; Babcock, B. A.; Durst, R. F.; Seeger, C. H.; Levine, S. E.; Abe, F.; Suzuki, D.; Nagakane, M.; Sickafoose, A. A.; Person, M. J.; Zuluaga, C.; Kosiarek, M. R.

    2015-12-01

    We observed the occultation of a 12th magnitude star, one of the two brightest occultation stars ever in our dozen years of continual monitoring of Pluto's atmosphere through such studies, on 29 June 2015 UTC. At Canterbury University's Mt. John University Observatory on the south island of New Zealand, in clear sky, we used our POETS frame-transfer CCD at 10 Hz with GPS timing on the 1-m McLellan telescope as well as an infrared camera on an 0.6-m telescope and three-color photometry at a slower cadence on a second 0.6-m telescope. The light curves show a central flash, indicating that we were close to the center of the occultation path, and allowing us to explore Pluto's atmosphere lower than usual. The light curves show that Pluto's atmosphere remained robust. Observations from 0.5- and 0.4-m telescopes at the Auckland Observatory gave the first half of the occultation before clouds came in. We coordinated our observations with aircraft observations with NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) and its High Speed Imaging Photometer for Occultations (HIPO). Our ground-based and airborne stellar-occultation effort came only just over two weeks of Earth days and two Pluto days (based on Pluto's rotational period) before the flyby of NASA's New Horizons spacecraft, meaning that the mission's exquisite snapshot of Pluto's atmosphere can be placed in the context of our series of ground-based occultation observations carried out on a regular basis since 2002 following a first Pluto occultation observed in 1988 from aloft. Our observations were supported by NASA Planetary Astronomy grants NNX12AJ29G to Williams College, NNX15AJ82G to Lowell Observatory, and NNX10AB27G to MIT, and by the National Research Foundation of South Africa. We thank Alan Gilmore, Pam Kilmartin, Robert Lucas, Paul Tristam, and Carolle Varughese for assistance at Mt. John.

  9. Maintenance Maneuver Automation for an Adapted Cylindrical Shape TEC

    Directory of Open Access Journals (Sweden)

    Rafael Morales

    2016-09-01

    Full Text Available Several manufacturers have developed devices with which to harness tidal/current power in areas where the depth does not exceed 40 m. These are the so-called first generation Tidal Energy Converters (TEC, and they are usually fixed to the seabed by gravity. When carrying out maintenance tasks on these devices it is, therefore, necessary to remove the nacelles from their bases and raise them to the surface of the sea. They must subsequently be placed back on their bases. These tasks require special high performance ships, signifying high maintenance costs. The automation of emersion and immersion maneuvers will undoubtedly lead to lower costs, given that ships with less demanding requirements will be required for the aforementioned maintenance tasks. This research presents a simple two degrees of freedom dynamic model that can be used to control a first generation TEC that has been conceived of to harness energy from marine currents. The control of the system is carried out by means of a water ballast system located inside the nacelle of the main power unit and is used as an actuator to produce buoying vertical forces. A nonlinear control law based on a decoupling term for the closed loop depth and/or orientation control is also proposed in order to ensure adequate behavior when the TEC performs emersion and immersion maneuvers with only hydrostatic buoyancy forces. The control scheme is composed of an inner loop consisting of a linear and decoupled input/output relationship and the vector of friction and compressibility terms and an outer loop that operates with the tracking error vector in order to ensure the asymptotically exponential stability of the TEC posture. Finally, the effectiveness of the dynamic model and the controller approach is demonstrated by means of numerical simulations when the TEC is carrying out an emersion maneuver for the development of general maintenance tasks and an emersion maneuver for blade-cleaning maintenance

  10. Ground-based observations of Kepler asteroseismic targets

    CERN Document Server

    Uytterhoeven, K; Southworth, J; Randall, S; Ostensen, R; Molenda-Zakowicz, J; Marconi, M; Kurtz, D W; Kiss, L; Gutierrez-Soto, J; Frandsen, S; De Cat, P; Bruntt, H; Briquet, M; Zhang, X B; Telting, J H; Steslicki, M; Ripepi, V; Pigulski, A; Paparo, M; Oreiro, R; Choong, Ngeow Chow; Niemczura, E; Nemec, J; Narwid, A; Mathias, P; Martin-Ruiz, S; Lehman, H; Kopacki, G; Karoff, C; Jackiewicz, J; Henden, A A; Handler, G; Grigachene, A; Green, E M; Garrido, R; Machado, L Fox; Debosscher, J; Creevey, O L; Catanzaro, G; Bognar, Z; Biazzo, K; Bernabei, S

    2010-01-01

    We present the ground-based activities within the different working groups of the Kepler Asteroseismic Science Consortium (KASC). The activities aim at the systematic characterization of the 5000+ KASC targets, and at the collection of ground-based follow-up time-series data of selected promising Kepler pulsators. So far, 35 different instruments at 30 telescopes on 22 different observatories in 12 countries are in use, and a total of more than 530 observing nights has been awarded. (Based on observations made with the Isaac Newton Telescope, William Herschel Telescope, Nordic Optical Telescope, Telescopio Nazionale Galileo, Mercator Telescope (La Palma, Spain), and IAC-80 (Tenerife, Spain). Also based on observations taken at the observatories of Sierra Nevada, San Pedro Martir, Vienna, Xinglong, Apache Point, Lulin, Tautenburg, Loiano, Serra la Nave, Asiago, McDonald, Skinakas, Pic du Midi, Mauna Kea, Steward Observatory, Bialkow Observatory of the Wroclaw University, Piszkesteto Mountain Station, Observato...

  11. Ground-based Nuclear Detonation Detection (GNDD) Technology Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Casey, Leslie A.

    2014-01-13

    This GNDD Technology Roadmap is intended to provide guidance to potential researchers and help management define research priorities to achieve technology advancements for ground-based nuclear explosion monitoring science being pursued by the Ground-based Nuclear Detonation Detection (GNDD) Team within the Office of Nuclear Detonation Detection in the National Nuclear Security Administration (NNSA) of the U.S. Department of Energy (DOE). Four science-based elements were selected to encompass the entire scope of nuclear monitoring research and development (R&D) necessary to facilitate breakthrough scientific results, as well as deliver impactful products. Promising future R&D is delineated including dual use associated with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Important research themes as well as associated metrics are identified along with a progression of accomplishments, represented by a selected bibliography, that are precursors to major improvements to nuclear explosion monitoring.

  12. Impact of GPS tracking data of LEO satellites on global GPS solutions

    Science.gov (United States)

    Rothacher, M.; Svehla, D.

    Already at present quite a few Low Earth Orbiting (LEO) satellites (SAC-C, CHAMP, JASON-1, GRACE-1 and GRACE-2) are equipped with one or more GPS receivers for precise orbit determination or other applications (atmospheric sounding, gravity field recovery, . . . ). This trend will continue in the near future (e.g., with the GOCE and COSMIC missions) and we will soon have an entire "constellation" of LEO satellites tracked by GPS at our disposal. In this contribution we want to study the impact of LEO GPS measurements (from a single LEO satellite or from a LEO constellation) on global GPS solutions, where GPS satellite orbits and clocks, Earth rotation parameters (ERPs), station coordinates and troposphere zenith delays are determined simultaneously using the data of the global network of the International GPS Service (IGS). In order to assess the impact of the LEO GPS data on global IGS results, we have to perform a combined analysis of the space-borne and the ground-based GPS data. Such a combination may benefit on one hand from the differences between a ground station and a LEO, e.g., (1) the different tracking geometry (coverage of isolated geographical areas by LEOs, rapidly changing geometry, . . . ), (2) that LEOs connect all ground stations within 1-2 hours, (3) that baselines between LEO and ground stations may be longer than station-station baselines, (4) that no tropospheric delays have to be estimated for LEOs, and (5) that LEOs orbit the Earth within the ionosphere and may therefore contribute to global ionosphere models. On the other hand we have to deal with difficult aspects of precise orbit determination for the LEOs: only if we succeed to obtain very accurate dynamic or reduced-dynamic orbits for the LEOs, we will have a chance at all to improve the global GPS results. We present first results concerning the influence of LEO data on GPS orbits, ERPs, site coordinates, and troposphere zenith delays using both, variance-covariance analyses based on

  13. Ground-Based Calibration Of A Microwave Landing System

    Science.gov (United States)

    Kiriazes, John J.; Scott, Marshall M., Jr.; Willis, Alfred D.; Erdogan, Temel; Reyes, Rolando

    1996-01-01

    System of microwave instrumentation and data-processing equipment developed to enable ground-based calibration of microwave scanning-beam landing system (MSBLS) at distances of about 500 to 1,000 ft from MSBLS transmitting antenna. Ensures accuracy of MSBLS near touchdown point, without having to resort to expense and complex logistics of aircraft-based testing. Modified versions prove useful in calibrating aircraft instrument landing systems.

  14. Ground-Based Lidar for Atmospheric Boundary Layer Ozone Measurements

    Science.gov (United States)

    Kuang, Shi; Newchurch, Michael J.; Burris, John; Liu, Xiong

    2013-01-01

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than 10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  15. Ground-based lidar for atmospheric boundary layer ozone measurements.

    Science.gov (United States)

    Kuang, Shi; Newchurch, Michael J; Burris, John; Liu, Xiong

    2013-05-20

    Ground-based lidars are suitable for long-term ozone monitoring as a complement to satellite and ozonesonde measurements. However, current ground-based lidars are unable to consistently measure ozone below 500 m above ground level (AGL) due to both engineering issues and high retrieval sensitivity to various measurement errors. In this paper, we present our instrument design, retrieval techniques, and preliminary results that focus on the high-temporal profiling of ozone within the atmospheric boundary layer (ABL) achieved by the addition of an inexpensive and compact mini-receiver to the previous system. For the first time, to the best of our knowledge, the lowest, consistently achievable observation height has been extended down to 125 m AGL for a ground-based ozone lidar system. Both the analysis and preliminary measurements demonstrate that this lidar measures ozone with a precision generally better than ±10% at a temporal resolution of 10 min and a vertical resolution from 150 m at the bottom of the ABL to 550 m at the top. A measurement example from summertime shows that inhomogeneous ozone aloft was affected by both surface emissions and the evolution of ABL structures.

  16. Advanced GPS Technologies (AGT)

    Science.gov (United States)

    2015-05-01

    V Air Force Research Laboratory ••• Advanced GPS Technologies (AGT) Integrity *Service *Excellence 1 May 2015 Kevin Slimak Program Manager...2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Advanced GPS Technologies (AGT) 5a. CONTRACT NUMBER 5b...DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES Presented at the GPS Partnership

  17. GPS Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Global Positioning System (GPS) Test Facility Instrumentation Suite (GPSIS) provides great flexibility in testing receivers by providing operational control of...

  18. GPS phase scintillation at high latitudes during the geomagnetic storm of 17-18 March 2015

    DEFF Research Database (Denmark)

    Prikryl, P.; Ghoddousi-Fard, R.; Weygand, J. M.

    2016-01-01

    The geomagnetic storm of 17–18 March 2015 was caused by the impacts of a coronal mass ejection and a high-speed plasma stream from a coronal hole. The high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including GPS receivers, HF radars, ionosondes, riometers...

  19. 3 dimensional ionospheric electron density reconstruction based on GPS measurements

    Science.gov (United States)

    Stolle, C.; Schlüter, S.; Jacobi, C.; Jakowski, N.

    When radio waves as sended by the naviagtion system GPS are passing through the ionosphere they are subject to delays in phase, travel time and polarisation which is an effect of the free electrons. The measured integrated value of Total Electron Content can be utilised for three-dimensional reconstruction of electron density patterns in the ionosphere. Here a tomographic approach is represented. Scince the distribution of data is very sparse and patchy we decided for an algebraic iterative algorithm. The ground based GPS data collected by IGS receivers can be combined by space based GPS of radio limb sounding, incoherent scatter radar and ionosondes data. Hereby, radio occultation data improve beside the amount of available data especially the vertical resolution of electron density distribution. Ionosonde peack electron densities are taken as stop criteria determination for iteration. Reconstructed ionospheric scenarios and validations of the system by independent measurements are presented.

  20. Ionosphere Profile Estimation Using Ionosonde & GPS Data in an Inverse Refraction Calculation

    Science.gov (United States)

    Psiaki, M. L.

    2014-12-01

    A method has been developed to assimilate ionosonde virtual heights and GPS slant TEC data to estimate the parameters of a local ionosphere model, including estimates of the topside and of latitude and longitude variations. This effort seeks to better assimilate a variety of remote sensing data in order to characterize local (and eventually regional and global) ionosphere electron density profiles. The core calculations involve a forward refractive ray-tracing solution and a nonlinear optimal estimation algorithm that inverts the forward model. The ray-tracing calculations solve a nonlinear two-point boundary value problem for the curved ionosonde or GPS ray path through a parameterized electron density profile. It implements a full 3D solution that can handle the case of a tilted ionosphere. These calculations use Hamiltonian equivalents of the Appleton-Hartree magneto-plasma refraction index model. The current ionosphere parameterization is a modified Booker profile. It has been augmented to include latitude and longitude dependencies. The forward ray-tracing solution yields a given signal's group delay and beat carrier phase observables. An auxiliary set of boundary value problem solutions determine the sensitivities of the ray paths and observables with respect to the parameters of the augmented Booker profile. The nonlinear estimation algorithm compares the measured ionosonde virtual-altitude observables and GPS slant-TEC observables to the corresponding values from the forward refraction model. It uses the parameter sensitivities of the model to iteratively improve its parameter estimates in a way the reduces the residual errors between the measurements and their modeled values. This method has been applied to data from HAARP in Gakona, AK and has produced good TEC and virtual height fits. It has been extended to characterize electron density perturbations caused by HAARP heating experiments through the use of GPS slant TEC data for an LOS through the heated

  1. TEC, Trigger and Check, preparing LOFAR for Lunar observations

    Science.gov (United States)

    ter Veen, Sander; Mevius, Maaijke; Bonardi, Antonio; Buitink, Stijn; Corstanje, Arthur; Enriquez, J. Emilio; Falcke, Heino; Hörandel, Jörg R.; Mitra, Pragati; Mulrey, Katey; Nelles, Anna; Rachen, Jörg Paul; Rossetto, Laura; Schellart, Pim; Scholten, Olaf; Thoudam, Satyendra; Trinh, Gia; Winchen, Tobias

    2017-03-01

    One of the main ways to use radio to detect Ultra High Energy Neutrinos and Cosmic Rays is the Lunar Askaryan technique, that uses the Moon as a target and searches for nanosecond pulses with large radio telescopes. To use low frequency aperture arrays, such as LOFAR and the SKA, pose new challenges and possibilities in detection techniques of short radio pulses and to measure the Total Electron Content (TEC). As a prepatory work, we have used other measurements that use similar techniques, or that can answer a specific question, with the LOFAR radio telescope. This contribution reports on our work on triggering on short radio signals, post-event imaging of radio signals from buffered data and methods to determine the TEC-value.

  2. Global ionospheric TEC response to a strong magnetic storm

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The global characteristics of the ionospheric storm and irregularities as well as propagation of TEC (total electron content) disturbances during the strong mag-netic storm occurring in November 2004 were investigated by using the data of the IGS network. For the response of the global ionospheric TEC to this strong mag-netic storm, the following features are noticeable: 1) the maximum of the iono-spheric storm phase occurred around the main phase maximum of the magnetic storm; 2) the TEC response in equatorial and low latitudes was more remarkable than that in mid-high latitudes; 3) as a whole, the storm phase in the northern hemisphere was mainly positive, and it was negative in the southern hemisphere; 4) during the whole magnetic storm from November 7 to 11, the locations where the maxima of the positive and negative ionospheric storm phases occurred were nearly invariant to the Sun at low and equatorial latitudes, i.e. the 24-h recurrence. Analyzing results of TEC rate and its standard deviation showed that the iono-spheric irregularities and disturbances in the global mainly occurred around the main phase maximum of the storm, and they distributed in a large longitudinal re-gion for both day and night in mid-high latitudes and they generated and developed only after the sunset, and lasted out to the midnight in equatorial and low latitudes. The disturbance propagation parameters were also estimated by using the wavelet reconstruction and cross-correlation technologies for a set of spaced stations in the Northern America.

  3. Coastal GPS Altimetry for Eddy Monitoring

    Science.gov (United States)

    Cardellach, E.; Treuhaft, R. N.; Chao, Y.; Lowe, S. T.; Young, L. E.; Zuffada, C.

    2003-04-01

    Coastal zones (within approximately 20-30 km of the coast) are dominated by fast-changing (on the order of days) and small-scale (on the order of km or less) processes. The dynamics and thermodynamics associated with these coastal processes influence the physics, biogeochemistry and the associated carbon cycling in the coastal zones. To monitor these important processes at the highest possible resolution (both spatial and temporal) is therefore an integrated component of the Earth's observing system. Coastal processes are currently not adequately monitored from existing spaceborne observations. The infrared instruments can measure the sea surface temperature in coastal zones with a resolution of approximately 1km daily, but are heavily contaminated by clouds usually found in the land-sea boundaries. The conventional radar altimetry, even with the wide-swath (e.g., OSTM) configuration, can only provide measurements every 10 days, too long to resolve the fast-changing coastal processes, not mentioning the land contamination within the first few footprints (on the order of 20 km) away from the coast. Coastal GPS altimetry from cliffs or structures near the coastline provides a complementary way to measure these coastal processes. The precision of such ground-based grazing angle GPS measurements has been proven to be 2-cm over the smooth surface at Crater Lake [Treuhaft et al., 2001]. Nevertheless, the accuracy of the GPS altimetry over the open sea, significantly affected by roughness, has yet to be assessed. This poster aims to present a set of experiments and analyses to prove the coastal GPS altimetry concept with a few-cm accuracy goal. It includes the analysis of data gathered over the ocean from an oil platform, Platform Harvest, as well as simulations of the GPS reflected signal to identify and correct the effects of the sea roughness. The results of this research are planned to feed the design, execution and processing of an eddy monitoring experiment. It will

  4. TEC Longitude Difference Using GIMS and the IRI Model

    Science.gov (United States)

    Natali, Maria Paula; Meza, Amalia Margarita; Mendoza, Gastón

    2016-07-01

    The main geomagnetic field declination has a global distribution with positive and negative values showing maximum east-west differences over North America and Oceania and minimum differences over America and Asia. Several authors study one or more of these regions using TEC data derived from GNSS observations to describe variations in TEC. They reported a pronounced longitudinal variation respect to zero magnetic declination. One of the important factors that cause the longitude difference at mid-latitude is a combined effect of the longitude variations of magnetic declination and the variations of the zonal thermospheric winds with local time. We propose to study this effect using Global Ionospheric Maps (GIMs) and the respective TEC values generated from the International Reference Ionospheric (IRI) model, during a solar cycle, applying Principal Component Analysis (PCA). Our works is focused over different local times and regions at mid-latitude. PCA involves a mathematical procedure that transforms a number of correlated variables into a number of uncorrelated variables using the data itself. The spatial structure of the ionosphere variability and its temporal evolution, together are called modes, and there are ordered according to their percentage of the variability of data from highest to lowest. In this analysis the first mode has more than the 90 % of the variability, representing the nominal behavior of the ionosphere, and the second and third modes are the more important for our analysis, because they show the strong longitudinal variation in the different regions using either GIMs or the IRI model.

  5. Global structure of ionospheric TEC anomalies driven by geomagnetic storms

    Science.gov (United States)

    Pancheva, D.; Mukhtarov, P.; Andonov, B.

    2016-07-01

    This study examines the structure and variability of the ionospheric TEC anomalies driven by geomagnetic storms. For this purpose the CODE global ionospheric TEC data from four geomagnetically disturbed periods (29 October-1 November 2003, 7-10 November 2004, 14-15 December 2006, and 5-6 August 2011) have been considered. By applying the tidal analysis to the geomagnetically forced TEC anomalies we made an attempt to identify the tidal or stationary planetary wave (SPW) signatures that may contribute to the generation of these anomalies. It has been found that three types of positive anomalies with different origin and different latitudinal appearance are observed. These are: (i) anomalies located near latitudes of ±40° and related to the enhancement and poleward moving of the equatorial ionization anomaly (EIA) crests; (ii) anomalies located near latitudes of ±60° and seen predominantly in the night-side ionosphere, and (iii) very high latitude anomalies having mainly zonally symmetric structure and related to the auroral heating and thermospheric expansion. The decomposition analysis revealed that these anomalies can be reconstructed as a result of superposition of the following components: zonal mean (ZM), diurnal migrating (DW1), zonally symmetric diurnal (D0), and stationary planetary wave 1 (SPW1).

  6. Augmenting WFIRST Microlensing with a Ground-Based Telescope Network

    Science.gov (United States)

    Zhu, Wei; Gould, Andrew

    2016-06-01

    Augmenting the Wide Field Infrared Survey Telescope (WFIRST) microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable full two-dimensional (2-D) vector microlens parallax measurements for a substantial fraction of low-mass lenses as well as planetary and binary events that show caustic crossing features. For a significant fraction of the free-floating planet (FFP) events and all caustic-crossing planetary/binary events, these 2-D parallax measurements directly lead to complete solutions (mass, distance, transverse velocity) of the lens object (or lens system). For even more events, the complementary ground-based observations will yield 1-D parallax measurements. Together with the 1-D parallaxes from WFIRST alone, they can probe the entire mass range M > M_Earth. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. Other benefits of such a survey include improved understanding of binaries (particularly with low mass primaries), and sensitivity to distant ice-giant and gas-giant companions of WFIRST lenses that cannot be detected by WFIRST itself due to its restricted observing windows. Existing ground-based microlensing surveys can be employed if WFIRST is pointed at lower-extinction fields than is currently envisaged. This would come at some cost to the event rate. Therefore the benefits of improved characterization of lenses must be weighed against these costs.

  7. TEC MAX System. Operation and Maintenance Manual for the TEC Model 4005 MAX (Miniature Apparatus for X-Ray Diffraction System)

    Science.gov (United States)

    2005-03-31

    Model 4005) TEC has found that residual stress measurements can be made through thin layers of paint on steel surfaces (but not lead-based paints ...indicator lamp Operation and Maintenance Manual 5-11 TEC MAX System (Model 4005) 4005-OM-01 Revision 0, March 31, 2005 XRay Tube Status @ 0 20 40 60

  8. Relative amplitude of the variations of the total electron content according to the data of the GPS global network

    Science.gov (United States)

    Perevalova, N. P.; Afraimovich, E. L.; Zhivetiev, I. V.; Kosogorov, E. A.

    2007-04-01

    [1] A method is developed that makes it possible to estimate the relative amplitude dI/I of the variations of the total electron content (TEC) corresponding to the mean (MS) and intermediate (IS) scales of ionospheric irregularities (from 300 to 30 km). This method is based on the evaluation of TEC variations from the data of the global GPS network. The results of the analysis of the diurnal and latitudinal dependencies of dI/I and distribution probability P(dI/I) for 52 days with different level of geomagnetic activity are presented. The statistical estimates were obtained from the analysis of 106 samples of 2-hour-long TEC series. To obtain statistically significant results, we have chosen three latitudinal zones provided on the Web by the maximum number of GPS sites: high-latitudinal zone of the Northern America (50-80o N, 200-300o E; 59 stations), midlatitude zone of the Northern America (20-50o N, 200-300o E; 817 stations), and the equatorial zone (20o S-20o N, 0-360o E; 76 stations). It was found that on the average the relative amplitude of the TEC variations varies within the range 0-10% proportionally to the value of the Kp geomagnetic index. This dependence is best pronounced at high latitudes (the proportionality coefficient k = 0.37), is weaker at middle latitudes (k = 0.2), and is the weakest at the equator (kcardinal depletion of the slope of the power spectrum of TEC disturbances because of a decrease of the amplitude of the small-scale parts of the spectrum. The amplitude of TEC variations almost does not depend on solar activity index F 10.7. The obtained results do not always agree with the known mechanisms of generation and propagation of ionospheric irregularities at various latitudes and may be useful for development of the theory.

  9. The STACEE-32 Ground Based Gamma-ray Detector

    CERN Document Server

    Hanna, D S; Boone, L M; Chantell, M C; Conner, Z; Covault, C E; Dragovan, M; Fortin, P; Gregorich, D T; Hinton, J A; Mukherjee, R; Ong, R A; Oser, S; Ragan, K; Scalzo, R A; Schütte, D R; Theoret, C G; Tümer, T O; Williams, D A; Zweerink, J A

    2002-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment detector in its initial configuration (STACEE-32). STACEE is a new ground-based gamma ray detector using the atmospheric Cherenkov technique. In STACEE, the heliostats of a solar energy research array are used to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous detectors.

  10. The STACEE Ground-Based Gamma-Ray Detector

    CERN Document Server

    Gingrich, D M; Bramel, D; Carson, J; Covault, C E; Fortin, P; Hanna, D S; Hinton, J A; Jarvis, A; Kildea, J; Lindner, T; Müller, C; Mukherjee, R; Ong, R A; Ragan, K; Scalzo, R A; Theoret, C G; Williams, D A; Zweerink, J A

    2005-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) in its complete configuration. STACEE uses the heliostats of a solar energy research facility to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The light is concentrated onto an array of photomultiplier tubes located near the top of a tower. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous ground-based detectors. STACEE is being used to observe pulsars, supernova remnants, active galactic nuclei, and gamma-ray bursts.

  11. Research on target accuracy for ground-based lidar

    Science.gov (United States)

    Zhu, Ling; Shi, Ruoming

    2009-05-01

    In ground based Lidar system, the targets are used in the process of registration, georeferencing for point cloud, and also can be used as check points. Generally, the accuracy of capturing the flat target center is influenced by scanning range and scanning angle. In this research, the experiments are designed to extract accuracy index of the target center with 0-90°scan angles and 100-195 meter scan ranges using a Leica HDS3000 laser scanner. The data of the experiments are listed in detail and the related results are analyzed.

  12. Ionospheric response to the 17-18 March 2015 geomagnetic storm as seen from multiple TEC and NmF2 measurements along 100°E

    Science.gov (United States)

    Bhuyan, Pradip; Yokoyama, Tatsuhiro; Kalita, Bitap Raj; Seemala, G. K.; Hazarika, Rumajyoti; Komolmis, Tharadol; Yatini, Clara; Chakrabarty, Dibyendu; Supnithi, Pornchai

    2016-07-01

    The response of the ionosphere along 100°E to the strong geomagnetic storm of 17-18 March 2015 has been investigated combining TEC and NmF2 data from multiple stations spanning low latitudes in the northern and southern hemispheres to the equator. The GPS TEC data measured over Dibrugarh (27.4°N, 95°E), Kohima (25.6°N, 94.1°E) and Ahmedabad (23.0°N, 72.5°E) and NmF2 measured along a chain of ionosonde stations Dibrugarh (27.5°N, 95°E), Chiang Mai (18.76ºN, 98.93ºE), Chumphon (10.72ºN,99.37ºE), Kototabang (0.2ºS,100.32ºE) and Cocos Island (12.2ºS,96.8ºE ) were used to examine the signature of the storm around the low-mid latitude ionosphere in this sector. Nearly similar TEC variation has been observed over Dibrugarh and Kohima located at the northern edge of the EIA. The maximum TEC on 18 March over Dibrugarh and Kohima was reduced by more than ~80 TECU compared to that on the geomagnetically quiet day of 16 March 2015. In contrast to the substantial reduction in TEC over ~100°E TEC from the ~75°E longitude station Ahmedabad showed insignificant variations on the same day. Strong reduction in NmF2 at the crest of the anomaly in both northern and southern hemisphere (Dibrugarh, Ching Mai and Cocos Island) and enhancement near the equator (Cumphon and Kototbang) has been observed. The O/N2 ratio as obtained from the TIMED/GUVI reduced substantially along 100°E on 18 March compared to other longitude sectors. Equatorward meridional winds depleted the ionization at the crest region and enhanced the same near the equator. No L band scintillation was observed in the evening of 17 March at Dibrugarh and Kohima indicating absence of F region irregularity along this longitude while strong scintillations were observed at 75°E. The reversal of the IMF Bz from southward to northward direction in the dusk to evening sector inhibited the growth of the irregularity due to reversal of the PPEF at 100°E while the PPEF favoured generation and growth of Spread F

  13. Statistical Studies of Ground-Based Optical Lightning Signatures

    Science.gov (United States)

    Hunt, C. R.; Nemzek, R. J.; Suszcynsky, D. M.

    2005-12-01

    Most extensive optical studies of lightning have been conducted from orbit, and the statistics of events collected from earth are relatively poorly documented. The time signatures of optical power measured in the presence of clouds are inevitably affected by scattering,which can distort the signatures by extending and delaying the amplitude profile in time. We have deployed two all-sky photodiode detectors, one in New Mexico and one in Oklahoma, which are gathering data alongside electric field change monitors as part of the LANL EDOTX Great Plains Array. Preliminary results show that the photodiode is sensitive to approximately 50% or more of RF events detected at ranges of up to 30 km, and still has some sensitivity at ranges in excess of 60 km (distances determined by the EDOTX field-change array). The shapes of events within this range were assessed, with focus on rise time, width, peak power, and their correlation to corresponding electric field signatures, and these are being compared with published on-orbit and ground-based data. Initial findings suggest a mean characteristic width (ratio of total detected optical energy to peak power) of 291 +/- 12 microseconds and a mean delay between the RF signal peak and optical peak of 121 +/- 17 microseconds. These values fall between prior ground-based measurements of direct return stroke emissions, and scattering-dominated on-orbit measurements. This work will promote better understanding of the correspondence between radio and optical measurements of lightning.

  14. Study on the Ionospheric TEC Variations During the Total Solar Eclipse of July 22,2009%2009年7月22日日全食期间电离层总电子含量变化研究

    Institute of Scientific and Technical Information of China (English)

    莫晓华; 张东和; 覃健生; 叶锦凤; 萧佐

    2012-01-01

    Variations of the ionospheric Total Electron Content(TEC) during the total solar eclipse of July 22,2009 was investigated using GPS observed data obtained at five GPS stations(one is in total solar eclipse region,the others are in partial solar eclipse region) in China region.Results indicate that during the total solar eclipse,TEC experiences a decline and recovery process;the delay of a minimum level of TEC with respect to the maximum phase of the eclipse is about 1~10min;the Ionosphere Pierce Point(IPP) of minimum TEC is closer to total solar eclipse region,the decrease of TEC is larger,and during the total solar eclipse,the mean decay TEC compared to the TEC on reference date above WUHN station(114.35°E,30.53°N) is the maximum,reaching 4.58 TECU.%利用中国区域内五个GPS台站(一个台站处于日全食区域、四个台站处于日偏食区域)观测数据,研究2009年7月22日日全食期间电离层总电子含量(TEC)的变化,结果表明,日全食期间,电离层TEC值经历了下降和恢复的过程,最小TEC相对于最大食偏的时间延迟约为1~10 min;台站测得最小TEC的星下点(IPP)越靠近日全食带TEC下降量越大,在日食期间武汉站(114.35°E,30.53°N)TEC相对于各参考日期的TEC,其平均下降量最大,达到4.58TECU.

  15. Aircraft landing using GPS

    Science.gov (United States)

    Lawrence, David Gary

    The advent of the Global Positioning System (GPS) is revolutionizing the field of navigation. Commercial aviation has been particularly influenced by this worldwide navigation system. From ground vehicle guidance to aircraft landing applications, GPS has the potential to impact many areas of aviation. GPS is already being used for non-precision approach guidance; current research focuses on its application to more critical regimes of flight. To this end, the following contributions were made: (1) Development of algorithms and a flexible software architecture capable of providing real-time position solutions accurate to the centimeter level with high integrity. This architecture was used to demonstrate 110 automatic landings of a Boeing 737. (2) Assessment of the navigation performance provided by two GPS-based landing systems developed at Stanford, the Integrity Beacon Landing System, and the Wide Area Augmentation System. (3) Preliminary evaluation of proposed enhancements to traditional techniques for GPS positioning, specifically, dual antenna positioning and pseudolite augmentation. (4) Introduction of a new concept for positioning using airport pseudolites. The results of this research are promising, showing that GPS-based systems can potentially meet even the stringent requirements of a Category III (zero visibility) landing system. Although technical and logistical hurdles still exist, it is likely that GPS will soon provide aircraft guidance in all phases of flight, including automatic landing, roll-out, and taxi.

  16. Integration of the End Cap TEC+ of the CMS Silicon Strip Tracker

    CERN Document Server

    Adler, Volker; Ageron, Michel; Agram, Jean-Laurent; Atz, Bernd; Barvich, Tobias; Baulieu, Guillaume; Beaumont, Willem; Beissel, Franz; Bergauer, Thomas; Berst, Jean-Daniel; Blüm, Peter; Bock, E; Bogelsbacher, F; de Boer, Wim; Bonnet, Jean-Luc; Bonnevaux, Alain; Boudoul, Gaelle; Bouhali, Othmane; Braunschweig, Wolfgang; Bremer, R; Brom, Jean-Marie; Butz, Erik; Chabanat, Eric; Chabert, Eric Christian; Clerbaux, Barbara; Contardo, Didier; De Callatay, Bernard; Dehm, Philip; Delaere, Christophe; Della Negra, Rodolphe; Dewulf, Jean-Paul; D'Hondt, Jorgen; Didierjean, Francois; Dierlamm, Alexander; Dirkes, Guido; Dragicevic, Marko; Drouhin, Frédéric; Ernenwein, Jean-Pierre; Esser, Hans; Estre, Nicolas; Fahrer, Manuel; Feld, Lutz; Fernández, J; Florins, Benoit; Flossdorf, Alexander; Flucke, Gero; Flügge, Günter; Fontaine, Jean-Charles; Freudenreich, Klaus; Frey, Martin; Friedl, Markus; Furgeri, Alexander; Giraud, Noël; Goerlach, Ulrich; Goorens, Robert; Graehling, Philippe; Grégoire, Ghislain; Gregoriev, E; Gross, Laurent; Hansel, S; Haroutunian, Roger; Hartmann, Frank; Heier, Stefan; Hermanns, Thomas; Heydhausen, Dirk; Heyninck, Jan; Hosselet, J; Hrubec, Josef; Jahn, Dieter; Juillot, Pierre; Kaminski, Jochen; Karpinski, Waclaw; Kaussen, Gordon; Keutgen, Thomas; Klanner, Robert; Klein, Katja; König, Stefan; Kosbow, M; Krammer, Manfred; Ledermann, Bernhard; Lemaître, Vincent; De Lentdecker, Gilles; Linn, Alexander; Lounis, Abdenour; Lübelsmeyer, Klaus; Lumb, Nicholas; Maazouzi, Chaker; Mahmoud, Tariq; Michotte, Daniel; Militaru, Otilia; Mirabito, Laurent; Müller, Thomas; Neukermans, Lionel; Ollivetto, C; Olzem, Jan; Ostapchuk, Andrey; Pandoulas, Demetrios; Pein, Uwe; Pernicka, Manfred; Perriès, Stephane; Piaseki, C; Pierschel, Gerhard; Piotrzkowski, Krzysztof; Poettgens, Michael; Pooth, Oliver; Rouby, Xavier; Sabellek, Andreas; Schael, Stefan; Schirm, Norbert; Schleper, Peter; Schmitz, Stefan Antonius; Schultz von Dratzig, Arndt; Siedling, Rolf; Simonis, Hans-Jürgen; Stahl, Achim; Steck, Pia; Steinbruck, G; Stoye, Markus; Strub, Roger; Tavernier, Stefaan; Teyssier, Daniel; Theel, Andreas; Trocmé, Benjamin; Udo, Fred; Van der Donckt, M; Van der Velde, C; Van Hove, Pierre; Vanlaer, Pascal; Van Lancker, Luc; Van Staa, Rolf; Vanzetto, Sylvain; Weber, Markus; Weiler, Thomas; Weseler, Siegfried; Wickens, John; Wittmer, Bruno; Wlochal, Michael; De Wolf, Eddi A; Zhukov, Valery; Zoeller, Marc Henning

    2009-01-01

    The silicon strip tracker of the CMS experiment has been completed and inserted into the CMS detector in late 2007. The largest sub-system of the tracker is its end cap system, comprising two large end caps (TEC) each containing 3200 silicon strip modules. To ease construction, the end caps feature a modular design: groups of about 20 silicon modules are placed on sub-assemblies called petals and these self-contained elements are then mounted into the TEC support structures. Each end cap consists of 144 petals, and the insertion of these petals into the end cap structure is referred to as TEC integration. The two end caps were integrated independently in Aachen (TEC+) and at CERN (TEC--). This note deals with the integration of TEC+, describing procedures for end cap integration and for quality control during testing of integrated sections of the end cap and presenting results from the testing.

  17. Integration of the End Cap TEC+ of the CMS Silicon Strip Tracker

    CERN Document Server

    Adler, Volker; Ageron, Michel; Agram, Jean-Laurent; Atz, Bernd; Barvich, Tobias; Baulieu, Guillaume; Beaumont, Willem; Beissel, Franz; Bergauer, Thomas; Berst, Jean-Daniel; Blüm, Peter; Bock, E; Bogelsbacher, F; de Boer, Wim; Bonnet, Jean-Luc; Bonnevaux, Alain; Boudoul, Gaelle; Bouhali, Othmane; Braunschweig, Wolfgang; Bremer, R; Brom, Jean-Marie; Butz, Erik; Chabanat, Eric; Chabert, Eric Christian; Clerbaux, Barbara; Contardo, Didier; De Callatay, Bernard; Dehm, Philip; Delaere, Christophe; Della Negra, Rodolphe; Dewulf, Jean-Paul; D'Hondt, Jorgen; Didierjean, Francois; Dierlamm, Alexander; Dirkes, Guido; Dragicevic, Marko; Drouhin, Frédéric; Ernenwein, Jean-Pierre; Esser, Hans; Estre, Nicolas; Fahrer, Manuel; Feld, Lutz; Fernández, J; Florins, Benoit; Flossdorf, Alexander; Flucke, Gero; Flügge, Günter; Fontaine, Jean-Charles; Freudenreich, Klaus; Frey, Martin; Friedl, Markus; Furgeri, Alexander; Giraud, Noël; Goerlach, Ulrich; Goorens, Robert; Graehling, Philippe; Grégoire, Ghislain; Gregoriev, E; Gross, Laurent; Hansel, S; Haroutunian, Roger; Hartmann, Frank; Heier, Stefan; Hermanns, Thomas; Heydhausen, Dirk; Heyninck, Jan; Hosselet, J; Hrubec, Josef; Jahn, Dieter; Juillot, Pierre; Kaminski, Jochen; Karpinski, Waclaw; Kaussen, Gordon; Keutgen, Thomas; Klanner, Robert; Klein, Katja; König, Stefan; Kosbow, M; Krammer, Manfred; Ledermann, Bernhard; Lemaître, Vincent; De Lentdecker, Gilles; Linn, Alexander; Lounis, Abdenour; Lübelsmeyer, Klaus; Lumb, Nicholas; Maazouzi, Chaker; Mahmoud, Tariq; Michotte, Daniel; Militaru, Otilia; Mirabito, Laurent; Müller, Thomas; Neukermans, Lionel; Ollivetto, C; Olzem, Jan; Ostapchuk, Andrey; Pandoulas, Demetrios; Pein, Uwe; Pernicka, Manfred; Perriès, Stephane; Piaseki, C; Pierschel, Gerhard; Piotrzkowski, Krzysztof; Poettgens, Michael; Pooth, Oliver; Rouby, Xavier; Sabellek, Andreas; Schael, Stefan; Schirm, Norbert; Schleper, Peter; Schmitz, Stefan Antonius; Schultz von Dratzig, Arndt; Siedling, Rolf; Simonis, Hans-Jürgen; Stahl, Achim; Steck, Pia; Steinbruck, G; Stoye, Markus; Strub, Roger; Tavernier, Stefaan; Teyssier, Daniel; Theel, Andreas; Trocmé, Benjamin; Udo, Fred; Van der Donckt, M; Van der Velde, C; Van Hove, Pierre; Vanlaer, Pascal; Van Lancker, Luc; Van Staa, Rolf; Vanzetto, Sylvain; Weber, Markus; Weiler, Thomas; Weseler, Siegfried; Wickens, John; Wittmer, Bruno; Wlochal, Michael; De Wolf, Eddi A; Zhukov, Valery; Zoeller, Marc Henning

    2009-01-01

    The silicon strip tracker of the CMS experiment has been completed and inserted into the CMS detector in late 2007. The largest sub-system of the tracker is its end cap system, comprising two large end caps (TEC) each containing 3200 silicon strip modules. To ease construction, the end caps feature a modular design: groups of about 20 silicon modules are placed on sub-assemblies called petals and these self-contained elements are then mounted into the TEC support structures. Each end cap consists of 144 petals, and the insertion of these petals into the end cap structure is referred to as TEC integration. The two end caps were integrated independently in Aachen (TEC+) and at CERN (TEC--). This note deals with the integration of TEC+, describing procedures for end cap integration and for quality control during testing of integrated sections of the end cap and presenting results from the testing.

  18. GPS Activities at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Behrend, Dirk

    2002-11-19

    The Alignment Engineering Group of the Stanford Linear Accelerator Center (SLAC) started to use RTK (real-time kinematic) GPS equipment in order to perform structure mapping and GIS-related tasks on the SLAC campus. In a first step a continuously observing GPS station (SLAC M40) was set up. This station serves as master control station for all differential GPS activities on site and its coordinates have been determined in the well-defined global geodetic datum ITRF2000 at a given reference epoch. Some trials have been performed to test the RTK method. The tests have proven RTK to be very fast and efficient.

  19. Similarity and differences in morphology and mechanisms of the foF2 and TEC disturbances during the geomagnetic storms on 26–30 September 2011

    Directory of Open Access Journals (Sweden)

    M. V. Klimenko

    2017-08-01

    Full Text Available This study presents an analysis of the ground-based observations and model simulations of ionospheric electron density disturbances at three longitudinal sectors (eastern European, Siberian and American during geomagnetic storms that occurred on 26–30 September 2011. We use the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP to reveal the main mechanisms influencing the storm-time behavior of the total electron content (TEC and the ionospheric F2 peak critical frequency (foF2 during different phases of geomagnetic storms. During the storm's main phase the long-lasting positive disturbances in TEC and foF2 at sunlit mid-latitudes are mainly explained by the storm-time equatorward neutral wind. The effects of eastward electric field can only explain the positive ionospheric storm in the first few hours of the initial storm phase. During the main phase the ionosphere was more changeable than the plasmasphere. The positive disturbances in the electron content at the plasmaspheric heights (800–20 000 km at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2. The daytime positive disturbances in foF2 and TEC occurred at middle and low latitudes and at the Equator due to n(O ∕ n(N2 enhancement during later stage of the main phase and during the recovery phase of the geomagnetic storm. The plasma tube diffusional depletion and negative disturbances in electron and neutral temperature were the main formation mechanisms of the simultaneous formation of the positive disturbances in foF2 and negative disturbances in TEC at low latitudes during the storm's recovery phase.

  20. Evaluation of regional ionospheric grid model over China from dense GPS observations

    Directory of Open Access Journals (Sweden)

    Xin Zhao

    2016-09-01

    Full Text Available The current global or regional ionospheric models have been established for monitoring the ionospheric variations. However, the spatial and temporal resolutions are not enough to describe total electron content (TEC variations in small scales for China. In this paper, a regional ionospheric grid model (RIGM with high spatial-temporal resolution (0.5° × 0.5° and 10-min interval in China and surrounding areas is established based on spherical harmonics expansion from dense GPS measurements provided by Crustal Movement Observation Network of China (CMONOC and the International GNSS Service (IGS. The correlation coefficient between the estimated TEC from GPS and the ionosonde measurements is 0.97, and the root mean square (RMS with respect to Center for Orbit Determination in Europe (CODE Global Ionosphere Maps (GIMs is 4.87 TECU. In addition, the impact of different spherical harmonics orders and degrees on TEC estimations are evaluated and the degree/order 6 is better. Moreover, effective ionospheric shell heights from 300 km to 700 km are further assessed and the result indicates that 550 km is the most suitable for regional ionospheric modeling in China at solar maximum.

  1. Study of the March 31, 2001 magnetic storm effects on the ionosphere using GPS data

    Science.gov (United States)

    Fedrizzi, M.; de Paula, E. R.; Langley, R. B.; Komjathy, A.; Batista, I. S.; Kantor, I. J.

    Despite the fact that much has been learned about the Sun-Earth relationship during disturbed conditions, understanding the effects of magnetic storms on the neutral and ionized upper atmosphere is still one of the most challenging topics remaining in the physics of this atmospheric region. In order to investigate the magnetospheric and ionospheric-thermospheric coupling processes, many researchers are taking advantage of the dispersive nature of the ionosphere to compute total electron content (TEC) from global positioning system (GPS) dual-frequency data. Even though there are currently a large number of GPS receivers in continuous operation, they are unevenly distributed for ionosphere study purposes, being situated mostly in the Northern Hemisphere. The relatively smaller number of GPS receivers located in the Southern Hemisphere and, consequently, the reduced number of available TEC measurements, cause ionospheric modelling to be less accurate in this region. In the work discussed in this paper, the University of New Brunswick Ionospheric Modelling Technique (UNB-IMT) has been used to describe the local time and geomagnetic latitude dependence of the TEC during the March 31, 2001 magnetic storm with an emphasis on the effects in the Southern Hemisphere. Data collected from several GPS networks worldwide, including the Brazilian network for continuous monitoring, have been used along with ionosonde measurements to investigate the global ionospheric response to this severe storm. Data analysis revealed interesting ionospheric effects, which are shown to be dependent on the local time at the storm commencement and the magnetic conditions previous to and during the storm period. The southward turning of the interplanetary magnetic field during the recovery phase of the storm began a process of substorm activity and development and intensification of electrojet activity over broad regions. Observed effects on the ionosphere during that storm are analysed and the

  2. Reconstitution of Btk signaling by the atypical tec family tyrosine kinases Bmx and Txk.

    Science.gov (United States)

    Tomlinson, M G; Kurosaki, T; Berson, A E; Fujii, G H; Johnston, J A; Bolen, J B

    1999-05-07

    Bruton's tyrosine kinase (Btk) is mutated in X-linked agammaglobulinemia patients and plays an essential role in B cell receptor signal transduction. Btk is a member of the Tec family of nonreceptor protein-tyrosine kinases that includes Bmx, Itk, Tec, and Txk. Cell lines deficient for Btk are impaired in phospholipase C-gamma2 (PLCgamma2)-dependent signaling. Itk and Tec have recently been shown to reconstitute PLCgamma2-dependent signaling in Btk-deficient human cells, but it is not known whether the atypical Tec family members, Bmx and Txk, can reconstitute function. Here we reconstitute Btk-deficient DT40 B cells with Bmx and Txk to compare their function with other Tec kinases. We show that in common with Itk and Tec, Bmx reconstituted PLCgamma2-dependent responses including calcium mobilization, extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) activation, and apoptosis. Txk also restored PLCgamma2/calcium signaling but, unlike other Tec kinases, functioned in a phosphatidylinositol 3-kinase-independent manner and failed to reconstitute apoptosis. These results are consistent with a common role for Tec kinases as amplifiers of PLCgamma2-dependent signal transduction, but suggest that the pleckstrin homology domain of Tec kinases, absent in Txk, is essential for apoptosis.

  3. The STACEE Ground-Based Gamma-ray Observatory

    Science.gov (United States)

    Ragan, Ken

    2002-04-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground-based instrument designed to study astrophysical sources of gamma rays in the energy range from 50 to 500 GeV using an array of heliostat mirrors at the National Solar Thermal Test Facility in New Mexico. The mirrors collect Cherenkov light generated by gamma-ray air showers and concentrate it onto cameras composed of photomultiplier tubes. The STACEE instrument is now complete, and uses a total of 64 heliostats. Prototype instruments, using smaller numbers of heliostats, have previously detected gamma emission from both the Crab Nebula and the Active Galactic Nucleus Mrk421. The complete instrument has a lower threshold -- approximately 50 GeV -- than those prototypes due to superior triggering and electronics, including flash ADCs for every channel.We will discuss the performance of the complete instrument in its first full season of operation, and present preliminary results of selected observations.

  4. Atmospheric contamination for CMB ground-based observations

    CERN Document Server

    Errard, J; Akiba, Y; Arnold, K; Atlas, M; Baccigalupi, C; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Cukierman, A; Delabrouille, J; Dobbs, M; Ducout, A; Elleflot, T; Fabbian, G; Feng, C; Feeney, S; Gilbert, A; Goeckner-Wald, N; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Hill, C; Holzapfel, W L; Hori, Y; Inoue, Y; Jaehnig, G C; Jaffe, A H; Jeong, O; Katayama, N; Kaufman, J; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Jeune, M Le; Lee, A T; Leitch, E M; Leon, D; Linder, E; Matsuda, F; Matsumura, T; Miller, N J; Myers, M J; Navaroli, M; Nishino, H; Okamura, T; Paar, H; Peloton, J; Poletti, D; Puglisi, G; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K M; Schenck, D E; Sherwin, B D; Siritanasak, P; Smecher, G; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Tajima, O; Takakura, S; Tikhomirov, A; Tomaru, T; Whitehorn, N; Wilson, B; Yadav, A; Zahn, O

    2015-01-01

    Atmosphere is one of the most important noise sources for ground-based Cosmic Microwave Background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3d-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive an analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the POLARBEAR-I project first season data set. We compare our results to previous st...

  5. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    CERN Document Server

    Chen, Hsin-Yu; Vitale, Salvatore; Holz, Daniel E; Katsavounidis, Erik

    2016-01-01

    Ground-based interferometers are not perfectly all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean and, as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources' right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO's observations and electromagnetic follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over $80\\%$ of the localization probability, while mid-latitudes will access closer to $70\\%$. Facilities located near the two LIGO sites can obser...

  6. Progress in the ULTRA 1-m ground-based telescope

    Science.gov (United States)

    Romeo, Robert C.; Martin, Robert N.; Twarog, Bruce; Anthony-Twarog, Barbara; Taghavi, Ray; Hale, Rick; Etzel, Paul; Fesen, Rob; Shawl, Steve

    2006-06-01

    We present the technical status of the Ultra Lightweight Telescope for Research in Astronomy (ULTRA) program. The program is a 3-year Major Research Instrumentation (MRI) program funded by NSF. The MRI is a collaborative effort involving Composite Mirror Applications, Inc. (CMA), University of Kansas, San Diego State University and Dartmouth College. Objectives are to demonstrate the feasibility of carbon fiber reinforced plastic (CFRP) composite mirror technology for ground-based optical telescopes. CMA is spearheading the development of surface replication techniques to produce the optics, fabricating the 1m glass mandrel, and constructing the optical tube assembly (OTA). Presented will be an overview and status of the 1-m mandrel fabrication, optics development, telescope design and CFRP telescope fabrication by CMA for the ULTRA Telescope.

  7. Ground-based optical observation system for LEO objects

    Science.gov (United States)

    Yanagisawa, T.; Kurosaki, H.; Oda, H.; Tagawa, M.

    2015-08-01

    We propose a ground-based optical observation system for monitoring LEO objects, which uses numerous optical sensors to cover a vast region of the sky. Its potential in terms of detection and orbital determination were examined. About 30 cm LEO objects at 1000 km altitude are detectable using an 18 cm telescope, a CCD camera and the analysis software developed. Simulations and a test observation showed that two longitudinally separate observation sites with arrays of optical sensors can identify the same objects from numerous data sets and determine their orbits precisely. The proposed system may complement or replace the current radar observation system for monitoring LEO objects, like space-situation awareness, in the near future.

  8. Identification of rainy periods from ground based microwave radiometry

    Directory of Open Access Journals (Sweden)

    Ada Vittoria Bosisio

    2012-03-01

    Full Text Available In this paper the authors present the results of a study aiming at detecting rainy data in measurements collected by a dual band ground-based radiometer. The proposed criterion is based on the ratio of the brightness temperatures observed in the 20-30 GHz band without need of any ancillary information. A major result obtained from the probability density of the ratio computed over one month of data is the identification of threshold values between clear sky, cloudy sky and rainy sky, respectively. A linear fit performed by using radiometric data and concurrent rain gauge measurements shows a correlation coefficient equal to 0.56 between the temperature ratio and the observed precipitation.

  9. Optical vortex coronagraphs on ground-based telescopes

    CERN Document Server

    Jenkins, Charles

    2007-01-01

    The optical vortex coronagraph is potentially a remarkably effective device, at least for an ideal unobstructed telescope. Most ground-based telescopes however suffer from central obscuration and also have to operate through the aberrations of the turbulent atmosphere. This note analyzes the performance of the optical vortex in these circumstances and compares to some other designs, showing that it performs similarly in this situation. There is a large class of coronagraphs of this general type, and choosing between them in particular applications depends on details of performance at small off-axis distances and uniformity of response in the focal plane. Issues of manufacturability to the necessary tolerances are also likely to be important.

  10. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    Science.gov (United States)

    Chen, Hsin-Yu; Essick, Reed; Vitale, Salvatore; Holz, Daniel; Katsavounidis, Erik

    2017-01-01

    Ground-based interferometers are not perfectly all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean and, as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources' right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO's observations and electromagnetic follow-up. These effects can inform electromagnetic follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  11. Unique cell culture systems for ground based research

    Science.gov (United States)

    Lewis, Marian L.

    1990-01-01

    The horizontally rotating fluid-filled, membrane oxygenated bioreactors developed at NASA Johnson for spacecraft applications provide a powerful tool for ground-based research. Three-dimensional aggregates formed by cells cultured on microcarrier beads are useful for study of cell-cell interactions and tissue development. By comparing electron micrographs of plant seedlings germinated during Shuttle flight 61-C and in an earth-based rotating bioreactor it is shown that some effects of microgravity are mimicked. Bioreactors used in the UAH Bioreactor Laboratory will make it possible to determine some of the effects of altered gravity at the cellular level. Bioreactors can be valuable for performing critical, preliminary-to-spaceflight experiments as well as medical investigations such as in vitro tumor cell growth and chemotherapeutic drug response; the enrichment of stem cells from bone marrow; and the effect of altered gravity on bone and muscle cell growth and function and immune response depression.

  12. Spatial-angular modeling of ground-based biaxial lidar

    Science.gov (United States)

    Agishev, Ravil R.

    1997-10-01

    Results of spatial-angular LIDAR modeling based on an efficiency criterion introduced are represented. Their analysis shows that a low spatial-angular efficiency of traditional VIS and NIR systems is a main cause of a low S/BR ratio at the photodetector input. It determines the considerable measurements errors and the following low accuracy of atmospheric optical parameters retrieval. As we have shown, the most effective protection against intensive sky background radiation for ground-based biaxial LIDAR's consist in forming of their angular field according to spatial-angular efficiency criterion G. Some effective approaches to high G-parameter value achievement to achieve the receiving system optimization are discussed.

  13. Support vector machines for TEC seismo-ionospheric anomalies detection

    Directory of Open Access Journals (Sweden)

    M. Akhoondzadeh

    2013-02-01

    Full Text Available Using time series prediction methods, it is possible to pursue the behaviors of earthquake precursors in the future and to announce early warnings when the differences between the predicted value and the observed value exceed the predefined threshold value. Support Vector Machines (SVMs are widely used due to their many advantages for classification and regression tasks. This study is concerned with investigating the Total Electron Content (TEC time series by using a SVM to detect seismo-ionospheric anomalous variations induced by the three powerful earthquakes of Tohoku (11 March 2011, Haiti (12 January 2010 and Samoa (29 September 2009. The duration of TEC time series dataset is 49, 46 and 71 days, for Tohoku, Haiti and Samoa earthquakes, respectively, with each at time resolution of 2 h. In the case of Tohoku earthquake, the results show that the difference between the predicted value obtained from the SVM method and the observed value reaches the maximum value (i.e., 129.31 TECU at earthquake time in a period of high geomagnetic activities. The SVM method detected a considerable number of anomalous occurrences 1 and 2 days prior to the Haiti earthquake and also 1 and 5 days before the Samoa earthquake in a period of low geomagnetic activities. In order to show that the method is acting sensibly with regard to the results extracted during nonevent and event TEC data, i.e., to perform some null-hypothesis tests in which the methods would also be calibrated, the same period of data from the previous year of the Samoa earthquake date has been taken into the account. Further to this, in this study, the detected TEC anomalies using the SVM method were compared to the previous results (Akhoondzadeh and Saradjian, 2011; Akhoondzadeh, 2012 obtained from the mean, median, wavelet and Kalman filter methods. The SVM detected anomalies are similar to those detected using the previous methods. It can be concluded that SVM can be a suitable learning method

  14. Comparisons of IRI global TEC maps with CODE GIMs

    CERN Document Server

    Coisson, P; Radicella, S M

    2002-01-01

    The Global Ionospheric Maps (GIM) produced at CODE are used in this work as experimental reference to evaluate the performance of IRI in predicting global vertical TEC during a period of high solar activity. The analysis has been done for the four seasons of year 2001, comparing monthly median GIMs for 12 different UTs. The attention is focused on the correct reproduction of large scale features like the equatorial anomaly or behavior at high latitudes, to understand where and under which conditions the IRI model could present unexpectable features.

  15. Investigating Atmospheric Rivers using GPS PW from Ocean Transits

    Science.gov (United States)

    Almanza, V.; Foster, J. H.; Businger, S.

    2014-12-01

    Atmospheric Rivers (AR) can be described as a long narrow feature within a warm conveyor belt where anomalous precipitable water (PW) is transported from low to high latitudes. Close monitoring of ARs is heavily reliant on satellites, which are limited both in space and time, to capture the fluctuations PW particularly over the ocean. Ship-based Global Positioning System (GPS) receivers have been successful in obtaining millimeter PW accuracy within 100 km from the nearest ground-based reference receiver at a 30 second sampling rate. We extended this capability with a field experiment using ship-based GPS PW on board a cargo ship to traverse over the Eastern Pacific Ocean. In one 14-day cruise cycle, between the periods of February 3-16, 2014, the ship-based GPS captured PW spikes >50 mm during the early development of two ARs, which lead to moderate to heavy rainfall events for Hawaii and flood conditions along the West Coast of the United States. Comparisons between PW solutions processed using different GPS reference sites at distances 100-2000 km provided an internal validation for the ship-based GPS PW with errors typically less than 5 mm. Land-based observations provided an external validation and are in good agreement with ship-based GPS PW at distances GPS receivers offer an extremely cost-effective approach for acquiring continuous meteorological observations over the oceans, which can provide important calibration/validation data for satellite retrieval algorithms. Ship-based systems could be particularly useful for augmenting our meteorological observing networks to improve weather prediction and nowcasting, which in turn provide critical support for hazard response and mitigation efforts in coastal regions.

  16. Test of GBAS Integrity Monitoring System Using GPS Simulator

    Institute of Scientific and Technical Information of China (English)

    Yun Young-sun; Park Sung-min; Kee Chang-don

    2003-01-01

    In recent years, many countries are developing aircraft navigation systems using GNSS(Global Navigation Satellite System),because GNSS has many technical and economic benefits. International organizations as ICAO(International Civil Aviation Organization) and RTCA(Radio Technical Commission for Aeronautics) set up international standards of GBAS(Ground Based Augmentation System)using GNSS and recommend countries to develop GBAS that is based on the standards. To go with the international stream, Korea Airport Cooperation has also developed GBAS. For evaluating the system,KAC and Seoul National University have performed flight tests of the developed GBAS several times and have concluded that the system has good accuracy enough to be used in aircrafts. At that time, the purpose of tests was focused on accuracy of GBAS. But integrity of the system which is important for safety of aircrafts was not tested sufficiently,because it is impossible to make erroneous situations of real GPS signals. So, at this time, we used GPS simulator which can generate GPS signals with satellite failure scenarios. The GPS simulator used in this test generates GPS signals by the scenarios organized in advance.The scenarios can include pseudorange and carrier phase error, parity error and etc. So we organized several scenarios which can includes potential errors of GPS signals and many possible cases for testing the system effectively and accurately. And we tested integrity function of the GBAS system by using GPS signals generated by the simulator.This paper introduces the implemented integrity monitoring system and algorithms used in the tests. And it describes the scenarios of satellite failure. Finally, this paper shows the results of tests.

  17. Sumoylation of transcription factor Tec1 regulates signaling of mitogen-activated protein kinase pathways in yeast.

    Science.gov (United States)

    Wang, Yuqi; Abu Irqeba, Ameair; Ayalew, Mihretu; Suntay, Kristina

    2009-10-14

    Tec1 is a transcription factor in the yeast mitogen-activated protein kinase (MAPK) pathway that controls invasive growth. Previously we reported that a fraction of Tec1 protein is sumoylated on residue lysine 54 in normally growing cells. Here we describe regulation and functional consequences of Tec1 sumoylation. We found that activation of Kss1, the MAPK that directly activates Tec1, results in a decrease in Tec1 sumoylation and a concurrent increase of Tec1 transcriptional activity. Consistent with a role of sumoylation in inhibiting Tec1 activity, specifically increasing sumoylation of Tec1 by fusing it to the sumoylating enzyme Ubc9 leads to a dramatic decrease of Tec1 transcriptional activity. Invasive growth is also compromised in Tec1-Ubc9. In contrast, fusing sumoylation-site mutant Tec1, i.e., Tec1(K54R), to Ubc9 did not significantly alter transcriptional activation and had a less effect on invasive growth. Taken together, these findings provide evidence for regulated sumoylation as a mechanism to modulate the activity of Tec1 and validate Ubc9 fusion-directed sumoylation as a useful approach for studying protein sumoylation.

  18. Sumoylation of transcription factor Tec1 regulates signaling of mitogen-activated protein kinase pathways in yeast.

    Directory of Open Access Journals (Sweden)

    Yuqi Wang

    Full Text Available Tec1 is a transcription factor in the yeast mitogen-activated protein kinase (MAPK pathway that controls invasive growth. Previously we reported that a fraction of Tec1 protein is sumoylated on residue lysine 54 in normally growing cells. Here we describe regulation and functional consequences of Tec1 sumoylation. We found that activation of Kss1, the MAPK that directly activates Tec1, results in a decrease in Tec1 sumoylation and a concurrent increase of Tec1 transcriptional activity. Consistent with a role of sumoylation in inhibiting Tec1 activity, specifically increasing sumoylation of Tec1 by fusing it to the sumoylating enzyme Ubc9 leads to a dramatic decrease of Tec1 transcriptional activity. Invasive growth is also compromised in Tec1-Ubc9. In contrast, fusing sumoylation-site mutant Tec1, i.e., Tec1(K54R, to Ubc9 did not significantly alter transcriptional activation and had a less effect on invasive growth. Taken together, these findings provide evidence for regulated sumoylation as a mechanism to modulate the activity of Tec1 and validate Ubc9 fusion-directed sumoylation as a useful approach for studying protein sumoylation.

  19. The PhysTEC Teacher Education Program at FIU

    Science.gov (United States)

    Kramer, Laird

    2010-10-01

    The FIU PhysTEC Project is an integral component of the Physics Department's educational transformation that has led to more than a ten-fold increase in majors. The transformation seeks to increase the quality and quantity of physics majors and future physics teachers, including those from historically underrepresented groups. Elements of the efforts include transformed introductory physics courses, establishment of a physics research and learning community, engagement of stakeholders spanning high school through the university administration, and advocacy by a physics education research group. The PhysTEC Project supports future physics teachers through a Learning Assistant program coupled to newly revised secondary education programs. The Learning Assistant program is an experiential program that recruits new students into teaching careers while providing a mechanism for transforming courses - undergraduates experience the rewards and intellectual challenges of teaching through providing interactive engagement learning experiences for their peers in introductory physics courses. Students that continue in the program enroll in a multidisciplinary teacher preparation program and may receive significant financial support. FIU is a minority-serving urban public research institution in Miami, Florida serving over 39,000 students, of which 64% are Hispanic, 13% are Black, and 56% are women. Programmatic strategies and impacts of the program will be provided.

  20. Probing Pluto's Atmosphere Using Ground-Based Stellar Occultations

    Science.gov (United States)

    Sicardy, Bruno; Rio de Janeiro Occultation Team, Granada Team, International Occultation and Timing Association, Royal Astronomical Society New Zealand Occultation Section, Lucky Star associated Teams

    2016-10-01

    Over the last three decades, some twenty stellar occultations by Pluto have been monitored from Earth. They occur when the dwarf planet blocks the light from a star for a few minutes as it moves on the sky. Such events led to the hint of a Pluto's atmosphere in 1985, that was fully confirmed during another occultation in 1988, but it was only in 2002 that a new occultation could be recorded. From then on, the dwarf planet started to move in front of the galactic center, which amplified by a large factor the number of events observable per year.Pluto occultations are essentially refractive events during which the stellar rays are bent by the tenuous atmosphere, causing a gradual dimming of the star. This provides the density, pressure and temperature profiles of the atmosphere from a few kilometers above the surface up to about 250 km altitude, corresponding respectively to pressure levels of about 10 and 0.1 μbar. Moreover, the extremely fine spatial resolution (a few km) obtained through this technique allows the detection of atmospheric gravity waves, and permits in principle the detection of hazes, if present.Several aspects make Pluto stellar occultations quite special: first, they are the only way to probe Pluto's atmosphere in detail, as the dwarf planet is far too small on the sky and the atmosphere is far too tenuous to be directly imaged from Earth. Second, they are an excellent example of participative science, as many amateurs have been able to record those events worldwide with valuable scientific returns, in collaboration with professional astronomers. Third, they reveal Pluto's climatic changes on decade-scales and constrain the various seasonal models currently explored.Finally, those observations are fully complementary to space exploration, in particular with the New Horizons (NH) mission. I will show how ground-based occultations helped to better calibrate some NH profiles, and conversely, how NH results provide some key boundary conditions

  1. Independet Component Analyses of Ground-based Exoplanetary Transits

    Science.gov (United States)

    Silva Martins-Filho, Walter; Griffith, Caitlin Ann; Pearson, Kyle; Waldmann, Ingo; Biddle, Lauren; Zellem, Robert Thomas; Alvarez-Candal, Alvaro

    2016-10-01

    Most observations of exoplanetary atmospheres are conducted when a "Hot Jupiter" exoplanet transits in front of its host star. These Jovian-sized planets have small orbital periods, on the order of days, and therefore a short transit time, making them more ameanable to observations. Measurements of Hot Jupiter transits must achieve a 10-4 level of accuracy in the flux to determine the spectral modulations of the exoplanetary atmosphere. In order to accomplish this level of precision, we need to extract systematic errors, and, for ground-based measurements, the effects of Earth's atmosphere, from the signal due to the exoplanet, which is several orders of magnitudes smaller. Currently, the effects of the terrestrial atmosphere and the some of the time-dependent systematic errors are treated by dividing the host star by a reference star at each wavelength and time step of the transit. More recently, Independent Component Analyses (ICA) have been used to remove systematic effects from the raw data of space-based observations (Waldmann 2014,2012; Morello et al.,2015,2016). ICA is a statistical method born from the ideas of the blind-source separation studies, which can be used to de-trend several independent source signals of a data set (Hyvarinen and Oja, 2000). One strength of this method is that it requires no additional prior knowledge of the system. Here, we present a study of the application of ICA to ground-based transit observations of extrasolar planets, which are affected by Earth's atmosphere. We analyze photometric data of two extrasolar planets, WASP-1b and GJ3470b, recorded by the 61" Kuiper Telescope at Stewart Observatory using the Harris B and U filters. The presentation will compare the light curve depths and their dispersions as derived from the ICA analysis to those derived by analyses that ratio of the host star to nearby reference stars.References: Waldmann, I.P. 2012 ApJ, 747, 12, Waldamann, I. P. 2014 ApJ, 780, 23; Morello G. 2015 ApJ, 806

  2. Long-term analysis of ionospheric polar patches based on CHAMP TEC data

    DEFF Research Database (Denmark)

    Noja, M.; Stolle, Claudia; Park, J.

    2013-01-01

    Total electron content (TEC) from LEO satellites offers great possibility to sound the upper ionosphere and plasmasphere. This paper describes a method to derive absolute TEC observations aboard CHAMP considering multipath effects and receiver differential code bias. The long-term data set of 9...

  3. NMobTec-EnvEdu: M-Learning System for Environmental Education

    Science.gov (United States)

    Cavus, Nadire

    2008-01-01

    This paper introduced the implementation of a New Mobile Technologies and Environmental Education System (NMobTec-EnvEdu) designed for m-learning environments. The NMobTec-EnvEdu system has been developed to provide environmental education in a collaborative framework to undergraduate students through the Internet using mobile phones. The study…

  4. An assessment of the quality of GPS water vapour estimates and their use in operational meteorology and climate monitoring

    OpenAIRE

    2010-01-01

    The path delay between a GPS satellite and a ground based GPS receiver depends, after elimination of ionospheric effects using a combination of the two GPS frequencies, on the integral effect of the densities of dry air and water vapour along the signal path. The total delay in the signal from each satellite is known as the slant delay as the path is most likely to be non-azimuthal. The slant paths are then transferred into the vertical (or zenith) by an elevation mapping function, and this n...

  5. Tissue Engineering of Cartilage on Ground-Based Facilities

    Science.gov (United States)

    Aleshcheva, Ganna; Bauer, Johann; Hemmersbach, Ruth; Egli, Marcel; Wehland, Markus; Grimm, Daniela

    2016-06-01

    Investigations under simulated microgravity offer the opportunity for a better understanding of the influence of altered gravity on cells and the scaffold-free three-dimensional (3D) tissue formation. To investigate the short-term influence, human chondrocytes were cultivated for 2 h, 4 h, 16 h, and 24 h on a 2D Fast-Rotating Clinostat (FRC) in DMEM/F-12 medium supplemented with 10 % FCS. We detected holes in the vimentin network, perinuclear accumulations of vimentin after 2 h, and changes in the chondrocytes shape visualised by F-actin staining after 4 h of FRC-exposure. Scaffold-free cultivation of chondrocytes for 7 d on the Random Positioning Machine (RPM), the FRC and the Rotating Wall Vessel (RWV) resulted in spheroid formation, a phenomenon already known from spaceflight experiments with chondrocytes (MIR Space Station) and thyroid cancer cells (SimBox/Shenzhou-8 space mission). The experiments enabled by the ESA-CORA-GBF programme gave us an optimal opportunity to study gravity-related cellular processes, validate ground-based facilities for our chosen cell system, and prepare long-term experiments under real microgravity conditions in space

  6. Theoretical validation of ground-based microwave ozone observations

    Directory of Open Access Journals (Sweden)

    P. Ricaud

    Full Text Available Ground-based microwave measurements of the diurnal and seasonal variations of ozoneat 42±4.5 and 55±8 km are validated by comparing with results from a zero-dimensional photochemical model and a two-dimensional (2D chemical/radiative/dynamical model, respectively. O3 diurnal amplitudes measured in Bordeaux are shown to be in agreement with theory to within 5%. For the seasonal analysis of O3 variation, at 42±4.5 km, the 2D model underestimates the yearly averaged ozone concentration compared with the measurements. A double maximum oscillation (~3.5% is measured in Bordeaux with an extended maximum in September and a maximum in February, whilst the 2D model predicts only a single large maximum (17% in August and a pronounced minimum in January. Evidence suggests that dynamical transport causes the winter O3 maximum by propagation of planetary waves, phenomena which are not explicitly reproduced by the 2D model. At 55±8 km, the modeled yearly averaged O3 concentration is in very good agreement with the measured yearly average. A strong annual oscillation is both measured and modeled with differences in the amplitude shown to be exclusively linked to temperature fields.

  7. Models of ionospheric VLF absorption of powerful ground based transmitters

    Science.gov (United States)

    Cohen, M. B.; Lehtinen, N. G.; Inan, U. S.

    2012-12-01

    Ground based Very Low Frequency (VLF, 3-30 kHz) radio transmitters play a role in precipitation of energetic Van Allen electrons. Initial analyses of the contribution of VLF transmitters to radiation belt losses were based on early models of trans-ionospheric propagation known as the Helliwell absorption curves, but some recent studies have found that the model overestimates (by 20-100 dB) the VLF energy reaching the magnetosphere. It was subsequently suggested that conversion of wave energy into electrostatic modes may be responsible for the error. We utilize a newly available extensive record of VLF transmitter energy reaching the magnetosphere, taken from the DEMETER satellite, and perform a direct comparison with a sophisticated full wave model of trans-ionospheric propagation. Although the model does not include the effect of ionospheric irregularities, it correctly predicts the average total power injected into the magnetosphere within several dB. The results, particularly at nighttime, appear to be robust against the variability of the ionospheric electron density. We conclude that the global effect of irregularity scattering on whistler mode conversion to quasi-electrostatic may be no larger than 6 dB.

  8. Atmospheric Refraction Path Integrals in Ground-Based Interferometry

    CERN Document Server

    Mathar, R J

    2004-01-01

    The basic effect of the earth's atmospheric refraction on telescope operation is the reduction of the true zenith angle to the apparent zenith angle, associated with prismatic aberrations due to the dispersion in air. If one attempts coherent superposition of star images in ground-based interferometry, one is in addition interested in the optical path length associated with the refracted rays. In a model of a flat earth, the optical path difference between these is not concerned as the translational symmetry of the setup means no net effect remains. Here, I evaluate these interferometric integrals in the more realistic arrangement of two telescopes located on the surface of a common earth sphere and point to a star through an atmosphere which also possesses spherical symmetry. Some focus is put on working out series expansions in terms of the small ratio of the baseline over the earth radius, which allows to bypass some numerics which otherwise is challenged by strong cancellation effects in building the opti...

  9. Experiments on a Ground-Based Tomographic Synthetic Aperture Radar

    Directory of Open Access Journals (Sweden)

    Hoonyol Lee

    2016-08-01

    Full Text Available This paper presents the development and experiment of three-dimensional image formation by using a ground-based tomographic synthetic aperture radar (GB-TomoSAR system. GB-TomoSAR formulates two-dimensional synthetic aperture by the motion of antennae, both in azimuth and vertical directions. After range compression, three-dimensional image focusing is performed by applying Deramp-FFT (Fast Fourier Transform algorithms, both in azimuth and vertical directions. Geometric and radiometric calibrations were applied to make an image cube, which is then projected into range-azimuth and range-vertical cross-sections for visualization. An experiment with a C-band GB-TomoSAR system with a scan length of 2.49 m and 1.86 m in azimuth and vertical-direction, respectively, shows distinctive three-dimensional radar backscattering of stable buildings and roads with resolutions similar to the theoretical values. Unstable objects such as trees and moving cars generate severe noise due to decorrelation during the eight-hour image-acquisition time.

  10. A comparative study of satellite and ground-based phenology.

    Science.gov (United States)

    Studer, S; Stöckli, R; Appenzeller, C; Vidale, P L

    2007-05-01

    Long time series of ground-based plant phenology, as well as more than two decades of satellite-derived phenological metrics, are currently available to assess the impacts of climate variability and trends on terrestrial vegetation. Traditional plant phenology provides very accurate information on individual plant species, but with limited spatial coverage. Satellite phenology allows monitoring of terrestrial vegetation on a global scale and provides an integrative view at the landscape level. Linking the strengths of both methodologies has high potential value for climate impact studies. We compared a multispecies index from ground-observed spring phases with two types (maximum slope and threshold approach) of satellite-derived start-of-season (SOS) metrics. We focus on Switzerland from 1982 to 2001 and show that temporal and spatial variability of the multispecies index correspond well with the satellite-derived metrics. All phenological metrics correlate with temperature anomalies as expected. The slope approach proved to deviate strongly from the temporal development of the ground observations as well as from the threshold-defined SOS satellite measure. The slope spring indicator is considered to indicate a different stage in vegetation development and is therefore less suited as a SOS parameter for comparative studies in relation to ground-observed phenology. Satellite-derived metrics are, however, very susceptible to snow cover, and it is suggested that this snow cover should be better accounted for by the use of newer satellite sensors.

  11. Satellite Type Estination from Ground-based Photometric Observation

    Science.gov (United States)

    Endo, T.; Ono, H.; Suzuki, J.; Ando, T.; Takanezawa, T.

    2016-09-01

    The optical photometric observation is potentially a powerful tool for understanding of the Geostationary Earth Orbit (GEO) objects. At first, we measured in laboratory the surface reflectance of common satellite materials, for example, Multi-layer Insulation (MLI), mono-crystalline silicon cells, and Carbon Fiber Reinforced Plastic (CFRP). Next, we calculated visual magnitude of a satellite by simplified shape and albedo. In this calculation model, solar panels have dimensions of 2 by 8 meters, and the bus area is 2 meters squared with measured optical properties described above. Under these conditions, it clarified the brightness can change the range between 3 and 4 magnitudes in one night, but color index changes only from 1 to 2 magnitudes. Finally, we observed the color photometric data of several GEO satellites visible from Japan multiple times in August and September 2014. We obtained that light curves of GEO satellites recorded in the B and V bands (using Johnson filters) by a ground-base optical telescope. As a result, color index changed approximately from 0.5 to 1 magnitude in one night, and the order of magnitude was not changed in all cases. In this paper, we briefly discuss about satellite type estimation using the relation between brightness and color index obtained from the photometric observation.

  12. Ground-based measurements of UV Index (UVI at Helwan

    Directory of Open Access Journals (Sweden)

    H. Farouk

    2012-12-01

    Full Text Available On October 2010 UV Index (UVI ground-based measurements were carried out by weather station at solar laboratory in NRIAG. The daily variation has maximum values in spring and summer days, while minimum values in autumn and winter days. The low level of UVI between 2.55 and 2.825 was found in December, January and February. The moderate level of UVI between 3.075 and 5.6 was found in March, October and November. The high level of UVI between 6.7 and 7.65 was found in April, May and September. The very high level of UVI between 8 and 8.6 was found in June, July and August. High level of radiation over 6 months per year including 3 months with a very high level UVI. According to the equation {UVI=a[SZA]b} the UVI increases with decreasing SZA by 82% on a daily scale and 88% on a monthly scale. Helwan exposure to a high level of radiation over 6 months per year including 3 months with a very high level UVI, so it is advisable not to direct exposure to the sun from 11 am to 2:00 pm.

  13. Practical use technology of coal ash (Poz-O-Tec); Sekitanbai no yuko riyo gijutsu (POZ-O-TEC)

    Energy Technology Data Exchange (ETDEWEB)

    Konno, K. [Center for Coal Utilization, Japan, Tokyo (Japan); Saito, Y. [Mitsui Mining Co. Ltd., Tokyo (Japan); Nagaya, Y. [Mitsui Construction Co. Ltd., Tokyo (Japan)

    1996-09-01

    In order to utilize more effectively coal ash whose generation amount is increasing year after year, studies have been made on a technology to manufacture and utilize a high-strength substance solidified under normal temperature by utilizing hydration reaction of pozzolan system (Poz-O-Tec). The study works have been done as a subsidy operation of the Agency of Natural Resources and Energy, and were completed in fiscal 1995. Poz-O-Tec is a wet powder made of coal ash and stack gas desulfurization sludge (gypsum) added and mixed with lime and an adequate amount of water, which solidifies by hydration as pozzolan does. The same method as used for ordinary sands may be used as the basic application method. Because this is the material whose strength increases after construction, thickness of construction may be reduced smaller than in constructions using soils and sands. Test constructions of about sixty cases have been carried out to date, typically represented in use as a road bed material, banking, and a base material for water-barrier gutters. High-strength solid material which is stable under normal temperature may be obtained by adjusting calcium content. As a result of its effectiveness in practical use having been verified, a certificate of technological judgment has been issued for the material by the Civil Engineering Research Center. 3 refs., 11 figs., 2 tabs.

  14. Use of GPS network data for HF Doppler measurements interpretation

    CERN Document Server

    Petrova, Inna R; Latypov, Ruslan R

    2014-01-01

    The method of measurement of Doppler frequency shift of ionospheric signal - HF Doppler technique - is one of well-known and widely used methods of ionosphere research. It allows to research various disturbances in the ionosphere. There are some sources of disturbances in the ionosphere. These are geomagnetic storms, solar flashes, metrological effects, atmospheric waves. This method allows to find out the influence of earthquakes, explosions and other processes on the ionosphere, which occur near to the Earth. HF Doppler technique has the high sensitivity to small frequency variations and the high time resolution, but interpretation of results is difficult. In this work we make an attempt to use GPS data for Doppler measurements interpretation. Modeling of Doppler frequency shift variations with use of TEC allows to separate ionosphere disturbances of medium scale.

  15. GPS satellite surveying

    CERN Document Server

    Leick, Alfred; Tatarnikov, Dmitry

    2015-01-01

    THE MOST COMPREHENSIVE, UP-TO-DATE GUIDE ON GPS TECHNOLOGY FOR SURVEYING Three previous editions have established GPS Satellite Surveying as the definitive industry reference. Now fully updated and expanded to reflect the newest developments in the field, this Fourth Edition features cutting-edge information on GNSS antennas, precise point positioning, real-time relative positioning, lattice reduction, and much more. Expert authors examine additional tools and applications, offering complete coverage of geodetic surveying using satellite technologies. The past decade has seen a major evolut

  16. GPS, su datum vertical.

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available La introducción de la metodología GPS en aplicaciones topográficas y geodésicas pone en notoria evidencia la clásica separación de sistemas de referencia en horizontal y vertical. Con GPS el posicionamiento es tridimensional, pero el concepto de altura difiere del clásico. Si se desea utilizar la información altimétrica debe contemplarse la ondulación del geoide.

  17. Re-visit of ionosphere storm morphology with TEC data in the current solar cycle

    Science.gov (United States)

    Cander, Ljiljana R.

    2016-02-01

    This paper addresses the magnetosphere-ionosphere-thermosphere (M-I-T) storm effects, with emphasis on 15 major geomagnetic storms in the current solar cycle as far as May 2015. It is an ionosphere storm response-case analysis based on the vertical total electron content (VTEC) observations at mid-latitude Global Positioning System (GPS) ground-based station HERS (0.33°E, 50.86°N). The time dependent features of ionospheric storms are examined with ∆VTEC defined as the percent change of VTEC during storm time relative to quiet time represented by its monthly median value at the same UT. During a specific event of April 2010 storm, the F2 layer peak electron density (NmF2) data at collocated Chilton (358.67°E, 51.70°N) ionosonde station are used for comparison. The seasonal dependence of the storms is identified and the strength of both positive and negative storms phases is correlated with the intensity of the geomagnetic storms. The focus is on localized characteristics of these solar-terrestrial disturbances and the relative roles of inherent physical and chemical processes that appear to be so changeable from one event to the other generating significant variability in ionospheric responses. The implications of these results for the persistence, certainty and consequently predictability of ionosphric storms are discussed and conclusions drown.

  18. Observational Selection Effects with Ground-based Gravitational Wave Detectors

    Science.gov (United States)

    Chen, Hsin-Yu; Essick, Reed; Vitale, Salvatore; Holz, Daniel E.; Katsavounidis, Erik

    2017-01-01

    Ground-based interferometers are not perfect all-sky instruments, and it is important to account for their behavior when considering the distribution of detected events. In particular, the LIGO detectors are most sensitive to sources above North America and the Indian Ocean, and as the Earth rotates, the sensitive regions are swept across the sky. However, because the detectors do not acquire data uniformly over time, there is a net bias on detectable sources’ right ascensions. Both LIGO detectors preferentially collect data during their local night; it is more than twice as likely to be local midnight than noon when both detectors are operating. We discuss these selection effects and how they impact LIGO’s observations and electromagnetic (EM) follow-up. Beyond galactic foregrounds associated with seasonal variations, we find that equatorial observatories can access over 80% of the localization probability, while mid-latitudes will access closer to 70%. Facilities located near the two LIGO sites can observe sources closer to their zenith than their analogs in the south, but the average observation will still be no closer than 44° from zenith. We also find that observatories in Africa or the South Atlantic will wait systematically longer before they can begin observing compared to the rest of the world though, there is a preference for longitudes near the LIGOs. These effects, along with knowledge of the LIGO antenna pattern, can inform EM follow-up activities and optimization, including the possibility of directing observations even before gravitational-wave events occur.

  19. Ground-based Measurements of Next Generation Spectroradiometric Standard Stars

    Science.gov (United States)

    McGraw, John T.

    2013-01-01

    Accurate, radiometric standards are essential to the future of ground- and space-based astronomy and astrophysics. While astronomers tend to think of “standard stars” as available calibration sources, progress at NIST to accurately calibrate inexpensive, easy to use photodiode detectors as spectroradiometric standards from 200 nm to 1800 nm allows referencing astronomical measurements to these devices. Direction-, time-, and wavelength-dependent transmission of Earth’s atmosphere is the single largest source of error for ground-based radiometric measurement of astronomical objects. Measurements and impacts of atmospheric extinction - scattering and absorption - on imaging radiometric and spectroradiometric measurements are described. The conclusion is that accurate real-time measurement of extinction in the column of atmosphere through which standard star observations are made, over the spectral region being observed and over the field of view of the telescope are required. New techniques to directly and simultaneously measure extinction in the column of atmosphere through which observations are made are required. Our direct extinction measurement solution employs three small facility-class instruments working in parallel: a lidar to measure rapidly time variable transmission at three wavelengths with uncertainty of 0.25% per airmass, a spectrophotometer to measure rapidly wavelength variable extinction with sub-1% precision per nanometer resolution element from 350 to 1050nm, and a wide-field camera to measure angularly variable extinction over the field of view. These instruments and their operation will be described. We assert that application of atmospheric metadata provided by this instrument suite corrects for a significant fraction of systematic errors currently limiting radiometric precision, and provides a major step towards measurements that are provably dominated by random noise.

  20. Ozone profiles above Kiruna from two ground-based radiometers

    Science.gov (United States)

    Ryan, Niall J.; Walker, Kaley A.; Raffalski, Uwe; Kivi, Rigel; Gross, Jochen; Manney, Gloria L.

    2016-09-01

    This paper presents new atmospheric ozone concentration profiles retrieved from measurements made with two ground-based millimetre-wave radiometers in Kiruna, Sweden. The instruments are the Kiruna Microwave Radiometer (KIMRA) and the Millimeter wave Radiometer 2 (MIRA 2). The ozone concentration profiles are retrieved using an optimal estimation inversion technique, and they cover an altitude range of ˜ 16-54 km, with an altitude resolution of, at best, 8 km. The KIMRA and MIRA 2 measurements are compared to each other, to measurements from balloon-borne ozonesonde measurements at Sodankylä, Finland, and to measurements made by the Microwave Limb Sounder (MLS) aboard the Aura satellite. KIMRA has a correlation of 0.82, but shows a low bias, with respect to the ozonesonde data, and MIRA 2 shows a smaller magnitude low bias and a 0.98 correlation coefficient. Both radiometers are in general agreement with each other and with MLS data, showing high correlation coefficients, but there are differences between measurements that are not explained by random errors. An oscillatory bias with a peak of approximately ±1 ppmv is identified in the KIMRA ozone profiles over an altitude range of ˜ 18-35 km, and is believed to be due to baseline wave features that are present in the spectra. A time series analysis of KIMRA ozone for winters 2008-2013 shows the existence of a local wintertime minimum in the ozone profile above Kiruna. The measurements have been ongoing at Kiruna since 2002 and late 2012 for KIMRA and MIRA 2, respectively.

  1. Project management for complex ground-based instruments: MEGARA plan

    Science.gov (United States)

    García-Vargas, María. Luisa; Pérez-Calpena, Ana; Gil de Paz, Armando; Gallego, Jesús; Carrasco, Esperanza; Cedazo, Raquel; Iglesias, Jorge

    2014-08-01

    The project management of complex instruments for ground-based large telescopes is a challenge itself. A good management is a clue for project success in terms of performance, schedule and budget. Being on time has become a strict requirement for two reasons: to assure the arrival at the telescope due to the pressure on demanding new instrumentation for this first world-class telescopes and to not fall in over-costs. The budget and cash-flow is not always the expected one and has to be properly handled from different administrative departments at the funding centers worldwide distributed. The complexity of the organizations, the technological and scientific return to the Consortium partners and the participation in the project of all kind of professional centers working in astronomical instrumentation: universities, research centers, small and large private companies, workshops and providers, etc. make the project management strategy, and the tools and procedures tuned to the project needs, crucial for success. MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is a facility instrument of the 10.4m GTC (La Palma, Spain) working at optical wavelengths that provides both Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) capabilities at resolutions in the range R=6,000-20,000. The project is an initiative led by Universidad Complutense de Madrid (Spain) in collaboration with INAOE (Mexico), IAA-CSIC (Spain) and Universidad Politécnica de Madrid (Spain). MEGARA is being developed under contract with GRANTECAN.

  2. Impact of Uncertainty in Solar Forcing on TEC

    Science.gov (United States)

    Shim, Ja Soon; Fuller-Rowell, Tim; Codrescu, Mihail; Fedrizzi, Mariangel; Mays, M. Leila; Taktakishvilli, Aleksandre; Kuznetsova, Maria; Rastätter, Lutz

    2016-07-01

    The Community Coordinated Modeling Center (CCMC), which is an interagency partnership to enable, support and perform the research and development for next-generation space science and space weather models, has been leading community-wide model validation efforts for Ionosphere/Thermosphere (IT) models along with other models that cover different domains of the Sun-Earth system such as heliosphere and magnetosphere. Uncertainty quantification plays a critical role in model validation. As a preliminary study on uncertainty analysis, we investigate how uncertainty in external forcing such as the solar radio flux at 10.7 cm (F10.7 index) and the interplanetary magnetic field (IMF) impacts on the IT model results during geomagnetic storm times (e.g., 2013 Mar. event). For this study, CTIPe (Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics) model is used. In this paper, we focus on the impact of the uncertainty of the parameters (F10.7 and IMF) on regional TEC (North American sector).

  3. The Effects of the Ionosphere on Ground-based Detection of the Global 21 cm Signal from the Cosmic Dawn and the Dark Ages

    Science.gov (United States)

    Datta, Abhirup; Bradley, Richard; Burns, Jack O.; Harker, Geraint; Komjathy, Attila; Lazio, T. Joseph W.

    2016-11-01

    Detection of the global H i 21 cm signal from the Cosmic Dawn and the Epoch of Reionization is the key science driver for several ongoing ground-based and future ground-/space-based experiments. The crucial spectral features in the global 21 cm signal (turning points) occur at low radio frequencies ≲ 100 {{MHz}}. In addition to the human-generated radio frequency interference, Earth’s ionosphere drastically corrupts low-frequency radio observations from the ground. In this paper, we examine the effects of time-varying ionospheric refraction, absorption, and thermal emission at these low radio frequencies and their combined effect on any ground-based global 21 cm experiment. It should be noted that this is the first study of the effect of a dynamic ionosphere on global 21 cm experiments. The fluctuations in the ionosphere are influenced by solar activity with flicker noise characteristics. The same characteristics are reflected in the ionospheric corruption to any radio signal passing through the ionosphere. As a result, any ground-based observations of the faint global 21 cm signal are corrupted by flicker noise (or 1/f noise, where f is the dynamical frequency) which scales as {ν }-2 (where ν is the frequency of radio observation) in the presence of a bright galactic foreground (\\propto {ν }-s, where s is the radio spectral index). Hence, the calibration of the ionosphere for any such experiment is critical. Any attempt to calibrate the ionospheric effects will be subject to the inaccuracies in the current ionospheric measurements using Global Positioning System (GPS) ionospheric measurements, riometer measurements, ionospheric soundings, etc. Even considering an optimistic improvement in the accuracy of GPS-total electron content measurements, we conclude that Earth’s ionosphere poses a significant challenge in the absolute detection of the global 21 cm signal below 100 MHz.

  4. GNSS derived TEC data ingestion into IRI 2012

    Science.gov (United States)

    Migoya-Orué, Yenca; Nava, Bruno; Radicella, Sandro; Alazo-Cuartas, Katy

    2015-04-01

    Experimental vertical total electron content (VTEC) data given by Global Ionospheric Maps (GIM) has been ingested into the IRI version 2012, aiming to obtain grids of effective input parameter values that allow to minimize the difference between the experimental and modeled vertical TEC. Making use of the experience gained with the technique of model adaptation applied to NeQuick (Nava et al., 2005), it has been found possible to compute IRI world grids of effective ionosphere index parameters (IG). The IG grids thus obtained can be interpolated in space and time to calculate with IRI the 3D electron density at any location and also the TEC along any ground-to-satellite ray-path for a given epoch. In this study, the ingestion technique is presented and a posteriori validation, along with an assessment of the capability of the 'ingested' IRI to reproduce the ionosphere day-to-day foF2 variability during disturbed and quiet periods. The foF2 values retrieved are compared with data from about 20 worldwide ionosondes for selected periods of high (year 2000) and moderate to low solar activity (year 2006). It was found that the use of the ingestion scheme enhances the performance of the model when compared with its standard use based on solar activity drivers (R12 and F10.7), especially for high solar activity. As an example, the mean and standard deviation of the differences between experimental and reconstructed F2-peak values for April of year 2000 is 0.09 and 1.28 MHz for ingested IRI, compared to -0.81 and 1.27 MHz (IRI with R12 input) and -0.02 and 1.46 MHz (IRI with F10.7 input).

  5. Semantic enrichment of GPS trajectories

    NARCIS (Netherlands)

    Graaff, de Victor; Keulen, van Maurice; By, de Rolf

    2012-01-01

    Semantic annotation of GPS trajectories helps us to recognize the interests of the creator of the GPS trajectories. Automating this trajectory annotation circumvents the requirement of additional user input. To annotate the GPS traces automatically, two types of automated input are required: 1) a co

  6. Study of magnetic storm effects on the ionosphere using GPS data

    Science.gov (United States)

    Fedrizzi, M.; de Paula, E. R.; Kantor, I. J.; Batista, I. S.; Langley, R. B.; Komjathy, A.

    Despite the fact that much has been learned about Sun-Earth relationship during disturbed conditions, understanding the effects of magnetic storms on the neutral and ionized upper atmosphere is still one of the most challenging topics remaining in the physics of this atmospheric region. In order to investigate the magnetospheric and ionospheric-thermospheric coupling processes, many researchers are taking advantage of the dispersive nature of the ionosphere to compute total electron content (TEC) from Global Positioning System (GPS) dual-frequency data. Even though there are currently a large number of GPS receivers in continuous operation, they are unevenly distributed for ionosphere study purposes, being situated mostly in the Northern Hemisphere. The relatively smaller number of GPS receivers located in the Southern Hemisphere and, consequently, the reduced number of available TEC measurements, cause ionospheric modelling to be less accurate in this region. In this work, the University of New Brunswick (UNB) Ionospheric Modelling Technique, which applies a spatial linear approximation of the vertical TEC above each station using stochastic parameters in a Kalman filter estimation, has been used to describe the local time and geomagnetic latitude dependence of the TEC. Data collected from several GPS networks worldwide, including the Brazilian Network for Continuous Monitoring (RBMC), have been used along with ionosonde measurements to investigate the ionospheric response to a severe magnetic storm occurred on March 31, 2001. Data analysis revealed distinct ionospheric effects, which are shown to be dependent on the season, local time and magnetic conditions previous and during the storm period. During the March 31, 2001 storm, the global ionosphere showed a distinct behaviour over Australian/Asian and American regions, which are located at approximately opposite longitude sectors. The southward turning of the interplanetary magnetic field during the recovery

  7. Variability in GPS sources

    NARCIS (Netherlands)

    Jauncey, DL; King, EA; Bignall, HE; Lovell, JEJ; Kedziora-Chudczer, L; Tzioumis, AK; Tingay, SJ; Macquart, JP; McCulloch, PM

    2003-01-01

    Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, similar to10%, vary. Their variability falls

  8. Variability in GPS sources

    NARCIS (Netherlands)

    Jauncey, DL; King, EA; Bignall, HE; Lovell, JEJ; Kedziora-Chudczer, L; Tzioumis, AK; Tingay, SJ; Macquart, JP; McCulloch, PM

    2003-01-01

    Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, similar to10%, vary. Their variability falls

  9. Remote Sensing of Low and Mid-Latitude Ionospheric Disturbances During Solar Minimum Using CITRIS and CERTO Measurements of TEC and Radio Scintillation

    Science.gov (United States)

    Siefring, C. L.; Bernhardt, P. A.

    2010-12-01

    Unique data on ionospheric plasma disturbances from the Naval Research Laboratory CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) three-frequency beacons transmitting at 150/400/1067 MHz and 2) the French global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons transmitting at 401.25 and 2036.25 MHz. CITRIS was operated in a complementary fashion with the C/NOFS satellite during most of its first year of operations; C/NOFS carries CERTO beacon along with in-situ diagnostics. CITRIS and ground receivers can simultaneously measure TEC and scintillations on different paths using CERTO on C/NOFS. When C/NOFS is not in view, CITRIS makes measurements from DORIS beacons and other LEO satellites. Because of the orbits CITRIS will always make measurements at the same longitude within 48 min of C/NOFS. The ability to look at multiple paths is unique and useful for studying the spatial extent and time duration of disturbances. The combination of TEC and scintillation measurements provides information on a range of scale-sizes from >1 km to about 100 m. The joint data set on plasma structures at low-latitudes is a focus of our presentation, with the addition of comparisons to CITRIS data taken at mid-latitude. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. The data covers large portions of the Earth (including the Pacific, African and South American sectors) during an unusually quite portion of the most

  10. HDAC3 Is a Master Regulator of mTEC Development

    Directory of Open Access Journals (Sweden)

    Yael Goldfarb

    2016-04-01

    Full Text Available The thymus provides a unique microenvironment enabling development and selection of T lymphocytes. Medullary thymic epithelial cells (mTECs play a pivotal role in this process by facilitating negative selection of self-reactive thymocytes and the generation of Foxp3+ regulatory T cells. Although studies have highlighted the non-canonical nuclear factor κB (NF-κB pathway as the key regulator of mTEC development, comprehensive understanding of the molecular pathways regulating this process still remains incomplete. Here, we demonstrate that the development of functionally competent mTECs is regulated by the histone deacetylase 3 (Hdac3. Although histone deacetylases are global transcriptional regulators, this effect is highly specific only to Hdac3, as neither Hdac1 nor Hdac2 inactivation caused mTEC ablation. Interestingly, Hdac3 induces an mTEC-specific transcriptional program independently of the previously recognized RANK-NFκB signaling pathway. Thus, our findings uncover yet another layer of complexity of TEC lineage divergence and highlight Hdac3 as a major and specific molecular switch crucial for mTEC differentiation.

  11. Ground Based Investigation of Electrostatic Accelerometer in HUST

    Science.gov (United States)

    Bai, Y.; Zhou, Z.

    2013-12-01

    High-precision electrostatic accelerometers with six degrees of freedom (DOF) acceleration measurement were successfully used in CHAMP, GRACE and GOCE missions which to measure the Earth's gravity field. In our group, space inertial sensor based on the capacitance transducer and electrostatic control technique has been investigated for test of equivalence principle (TEPO), searching non-Newtonian force in micrometer range, and satellite Earth's field recovery. The significant techniques of capacitive position sensor with the noise level at 2×10-7pF/Hz1/2 and the μV/Hz1/2 level electrostatic actuator are carried out and all the six servo loop controls by using a discrete PID algorithm are realized in a FPGA device. For testing on ground, in order to compensate one g earth's gravity, the fiber torsion pendulum facility is adopt to measure the parameters of the electrostatic controlled inertial sensor such as the resolution, and the electrostatic stiffness, the cross couple between different DOFs. A short distance and a simple double capsule equipment the valid duration about 0.5 second is set up in our lab for the free fall tests of the engineering model which can directly verify the function of six DOF control. Meanwhile, high voltage suspension method is also realized and preliminary results show that the horizontal axis of acceleration noise is about 10-8m/s2/Hz1/2 level which limited mainly by the seismic noise. Reference: [1] Fen Gao, Ze-Bing Zhou, Jun Luo, Feasibility for Testing the Equivalence Principle with Optical Readout in Space, Chin. Phys. Lett. 28(8) (2011) 080401. [2] Z. Zhu, Z. B. Zhou, L. Cai, Y. Z. Bai, J. Luo, Electrostatic gravity gradiometer design for the advanced GOCE mission, Adv. Sp. Res. 51 (2013) 2269-2276. [3] Z B Zhou, L Liu, H B Tu, Y Z Bai, J Luo, Seismic noise limit for ground-based performance measurements of an inertial sensor using a torsion balance, Class. Quantum Grav. 27 (2010) 175012. [4] H B Tu, Y Z Bai, Z B Zhou, L Liu, L

  12. Ground-Based Observing Campaign of Briz-M Debris

    Science.gov (United States)

    Lederer, S. M.; Buckalew, B.; Frith, J.; Cowardin, H. M.; Hickson, P.; Matney, M.; Anz-Meador, P.

    2017-01-01

    In 2015, NASA's Orbital Debris Program Office (ODPO) completed the installation of the Meter Class Autonomous Telescope (MCAT) on Ascension Island. MCAT is a 1.3m optical telescope designed with a fast tracking capability for observing orbital debris at all orbital regimes (Low-Erath orbits to Geosyncronous (GEO) orbits) from a low latitude site. This new asset is dedicated year-round for debris observations, and its location fills a geographical gap in the Ground-based Electro Optical Space Surveillance (GEODSS) network. A commercial off the shelf (COTS) research grade 0.4m telescope (named the Benbrook telescope) will also be installed on Ascension at the end of 2016. This smaller version is controlled by the same master software, designed by Euclid Research, and can be tasked to work independently or in concert with MCAT. Like MCAT, it has a the same suite of filters, a similar field of view, and a fast-tracking Astelco mount, and is also capable of tracking debris at all orbital regimes. These assets are well suited for targeted campagins or surveys of debris. Since 2013, NASA's ODPO has also had extensive access to the 3.8m infrared UKIRT telescope, located on Mauna Kea. At nearly 14,000-ft, this site affords excellent conditions for collecting both photometery and spectroscopy at near-IR (0.9 - 2.5 micrometers SWIR) and thermal-IR (8 - 25 micrometers; LWIR) regimes, ideal for investigating material properties as well as thermal characteristics and sizes of debris. For the purposes of understanding orbital debris, taking data in both survey mode as well as targeting individual objects for more in-depth characterizations are desired. With the recent break-ups of Briz-M rocket bodies, we have collected a suite of data in the optical, near-infrared, and mid-infrared of in-tact objects as well as those classified as debris. A break-up at GEO of a Briz-M rocket occurred in January, 2016, well timed for the first remote observing survey-campaign with MCAT. Access to

  13. Indoor Positioning Using GPS Revisited

    DEFF Research Database (Denmark)

    Kjærgaard, Mikkel Baun; Blunck, Henrik; Godsk, Torben

    2010-01-01

    It has been considered a fact that GPS performs too poorly inside buildings to provide usable indoor positioning. We analyze results of a measurement campaign to improve on the understanding of indoor GPS reception characteristics. The results show that using state-of-the-art receivers GPS...... low signal-to-noise ratios, multipath phenomena or bad satellite constellation geometry. We have also measured the indoor performance of embedded GPS receivers in mobile phones which provided lower availability and accuracy than state-of-the-art ones. Finally, we consider how the GPS performance...

  14. Adaptive Missile Guidance Using GPS

    Directory of Open Access Journals (Sweden)

    Pallavi Sharad Rupnar

    2013-05-01

    Full Text Available The name adaptive means we can guide any missile using GPS in any critical conditions. GPS guided missiles, using the exceptional navigational and surveying abilities of GPS, after being launched, could deliver a warhead to any part of the globe via the interface of the onboard computer in the missile with the GPS satellite system.GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles and precision-guided munitions. Artillery projectiles with embedded GPS receivers able to withstand accelerations of 12,000 G have been developed for use in 155mm.GPS guided weapons, with their technological advances over previous, are the superior weapon of choice in modern days

  15. Optimization of GPS Interferometric Reflectometry for Remote Sensing

    Science.gov (United States)

    Chen, Qiang

    GPS Interferometric Reflectometry (GPS-IR), a passive microwave remote sensing technique utilizing GPS signal as a source of opportunity, characterizes the Earth's surface through a bistatic radar configuration. The key idea of GPS-IR is utilizing a ground-based antenna to coherently receive the direct, or line-of-sight (LOS), signal and the Earth's surface reflected signal simultaneously. The direct and reflected signals create an interference pattern of the Signal-to-Noise Ratio (SNR), which contains the information about the Earth's surface environment. GPS-IR has proven its utility in a variety of environmental remote sensing applications, including the measurements of near-surface soil moisture, coastal sea level, snow depth and snow water equivalent, and vegetation biophysical parameters. A major approach of the GPS-IR technique is using the SNR data provided by the global network of the geodetic GPS stations deployed for tectonic and surveying applications. The geodetic GPS networks provide wide spatial coverage and have no additional cost for this capability expansion. However, the geodetic GPS instruments have intrinsic limitations: the geodetic-quality GPS antennas are designed to suppress the reflected signals, which is counter to the requirement of GPS-IR. As a result, it is desirable to refine and optimize the instrument and realize the full potential of the GPS-IR technique. This dissertation first analyzes the signal characteristics of four available polarizations of the GPS signal, and then discusses how these characteristics are related to and can be used for remote sensing applications of GPS-IR. Two types of antennas, a half-wavelength dipole antenna and a patch antenna, are proposed and fabricated to utilize the desired polarizations. Four field experiments are conducted to assess the feasibility of the design criteria and the performance of the proposed antennas. Three experiments are focused on snow depth measurement. The Table Mountain

  16. Ground-based lidar and microwave radiometry synergy for high vertical resolution absolute humidity profiling

    Science.gov (United States)

    Barrera-Verdejo, María; Crewell, Susanne; Löhnert, Ulrich; Orlandi, Emiliano; Di Girolamo, Paolo

    2016-08-01

    Continuous monitoring of atmospheric humidity profiles is important for many applications, e.g., assessment of atmospheric stability and cloud formation. Nowadays there are a wide variety of ground-based sensors for atmospheric humidity profiling. Unfortunately there is no single instrument able to provide a measurement with complete vertical coverage, high vertical and temporal resolution and good performance under all weather conditions, simultaneously. For example, Raman lidar (RL) measurements can provide water vapor with a high vertical resolution, albeit with limited vertical coverage, due to sunlight contamination and the presence of clouds. Microwave radiometers (MWRs) receive water vapor information throughout the troposphere, though their vertical resolution is poor. In this work, we present an MWR and RL system synergy, which aims to overcome the specific sensor limitations. The retrieval algorithm combining these two instruments is an optimal estimation method (OEM), which allows for an uncertainty analysis of the retrieved profiles. The OEM combines measurements and a priori information, taking the uncertainty of both into account. The measurement vector consists of a set of MWR brightness temperatures and RL water vapor profiles. The method is applied to a 2-month field campaign around Jülich (Germany), focusing on clear sky periods. Different experiments are performed to analyze the improvements achieved via the synergy compared to the individual retrievals. When applying the combined retrieval, on average the theoretically determined absolute humidity uncertainty is reduced above the last usable lidar range by a factor of ˜ 2 with respect to the case where only RL measurements are used. The analysis in terms of degrees of freedom per signal reveal that most information is gained above the usable lidar range, especially important during daytime when the lidar vertical coverage is limited. The retrieved profiles are further evaluated using

  17. Suborbital Reusable Launch Vehicles as an Opportunity to Consolidate and Calibrate Ground Based and Satellite Instruments

    Science.gov (United States)

    Papadopoulos, K.

    2014-12-01

    XCOR Aerospace, a commercial space company, is planning to provide frequent, low cost access to near-Earth space on the Lynx suborbital Reusable Launch Vehicle (sRLV). Measurements in the external vacuum environment can be made and can launch from most runways on a limited lead time. Lynx can operate as a platform to perform suborbital in situ measurements and remote sensing to supplement models and simulations with new data points. These measurements can serve as a quantitative link to existing instruments and be used as a basis to calibrate detectors on spacecraft. Easier access to suborbital data can improve the longevity and cohesiveness of spacecraft and ground-based resources. A study of how these measurements can be made on Lynx sRLV will be presented. At the boundary between terrestrial and space weather, measurements from instruments on Lynx can help develop algorithms to optimize the consolidation of ground and satellite based data as well as assimilate global models with new data points. For example, current tides and the equatorial electrojet, essential to understanding the Thermosphere-Ionosphere system, can be measured in situ frequently and on short notice. Furthermore, a negative-ion spectrometer and a Faraday cup, can take measurements of the D-region ion composition. A differential GPS receiver can infer the spatial gradient of ionospheric electron density. Instruments and optics on spacecraft degrade over time, leading to calibration drift. Lynx can be a cost effective platform for deploying a reference instrument to calibrate satellites with a frequent and fast turnaround and a successful return of the instrument. A calibrated reference instrument on Lynx can make collocated observations as another instrument and corrections are made for the latter, thus ensuring data consistency and mission longevity. Aboard a sRLV, atmospheric conditions that distort remotely sensed data (ground and spacecraft based) can be measured in situ. Moreover, an

  18. Ground-based monitoring of solar radiation in Moldova

    Science.gov (United States)

    Aculinin, Alexandr; Smicov, Vladimir

    2010-05-01

    Integrated measurements of solar radiation in Kishinev, Moldova have been started by Atmospheric Research Group (ARG) at the Institute of Applied Physics from 2003. Direct, diffuse and total components of solar and atmospheric long-wave radiation are measured by using of the radiometric complex at the ground-based solar radiation monitoring station. Measurements are fulfilled at the stationary and moving platforms equipped with the set of 9 broadband solar radiation sensors overlapping wavelength range from UV-B to IR. Detailed description of the station can be found at the site http://arg.phys.asm.md. Ground station is placed in an urban environment of Kishinev city (47.00N; 28.56E). Summary of observation data acquired at the station in the course of short-term period from 2004 to 2009 are presented below. Solar radiation measurements were fulfilled by using CM11(280-3000 nm) and CH1 sensors (Kipp&Zonen). In the course of a year maximum and minimum of monthly sums of total radiation was ~706.4 MJm-2 in June and ~82.1MJm-2 in December, respectively. Monthly sums of direct solar radiation (on horizontal plane) show the maximum and minimum values of the order ~456.9 MJm-2 in July and ~25.5MJm-2 in December, respectively. In an average, within a year should be marked the predominance of direct radiation over the scattered radiation, 51% and 49%, respectively. In the course of a year, the percentage contribution of the direct radiation into the total radiation is ~55-65% from May to September. In the remaining months, the percentage contribution decreases and takes the minimum value of ~ 28% in December. In an average, annual sum of total solar radiation is ~4679.9 MJm-2. For the period from April to September accounts for ~76% of the annual amount of total radiation. Annual sum of sunshine duration accounts for ~2149 hours, which is of ~ 48% from the possible sunshine duration. In an average, within a year maximum and minimum of sunshine duration is ~ 304 hours in

  19. Biosensors for EVA: Improved Instrumentation for Ground-based Studies

    Science.gov (United States)

    Soller, B.; Ellerby, G.; Zou, F.; Scott, P.; Jin, C.; Lee, S. M. C.; Coates, J.

    2010-01-01

    During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared

  20. Biosensors for EVA: Improved Instrumentation for Ground-based Studies

    Science.gov (United States)

    Soller, B.; Ellerby, G.; Zou, F.; Scott, P.; Jin, C.; Lee, S. M. C.; Coates, J.

    2010-01-01

    During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared

  1. GPS scintillation and irregularities at the front of an ionization tongue in the nightside polar ionosphere

    CERN Document Server

    van der Meeren, Christer; Lorentzen, Dag; Moen, Jøran Idar; Romano, Vincenzo

    2016-01-01

    In this paper we study a tongue of ionization (TOI) on 31 October 2011 which stretched across the polar cap from the Canadian dayside sector to Svalbard in the nightside ionosphere. The TOI front arrived over Svalbard around 1930 UT. We have investigated GPS scintillation and irregularities in relation to this TOI front. This is the first study presenting such detailed multi-instrument data of scintillation and irregularities in relation to a TOI front. Combining data from an all-sky imager, the European Incoherent Scatter Svalbard Radar, the Super Dual Auroral Radar Network Hankasalmi radar, and three GPS scintillation and total electron content (TEC) monitors in Longyearbyen and Ny-{\\AA}lesund, we observe bursts of phase scintillation and no amplitude scintillation in relation to the leading gradient of the TOI. Spectrograms of 50 Hz phase measurements show highly localized and variable structuring of the TOI leading gradient, with no structuring or scintillation within the TOI or ahead of the TOI.

  2. Numerical analysis of thermal effects in semiconductor disk laser with TEC cooler

    Science.gov (United States)

    Zhu, Renjiang; Zhang, Peng; Jiang, Maohua

    2016-11-01

    Based on generalized heat transfer model of thermoelectric cooler(TEC), the heat management model of semiconductor disk laser with TEC cooler has been built. With finite element method, this article has calculated the temperature distribution characteristics, and studied the effects of TEC current, heat exchange coefficient, the heatsink and the pump laser for the maximum temperature of quantum wells. Calculations show that the heat transfer coefficient significantly affects the ability of the TEC temperature shift, cooling system performance which is nearly inversely proportional to the heatsink thermal conductivity is not sensitive to its the thickness variation, and the performance of oxygen-free copper with optimization of the area is close to diamond. Meanwhile the maximum temperature of the quantum well has a linear relationship with the pump power, and increasing the pump spot size is an effective way to increase the optical power output

  3. Tropospheric jet stream as a source of traveling ionospheric disturbances observed by GPS

    Science.gov (United States)

    Wautelet, Gilles; Warnant, René

    2014-05-01

    The integrity and the reliability of real-time precise positioning applications with Global Positioning System (GPS) are affected by the ionospheric variability with time and space. As a consequence, scientific community aims at describing, explaining and forecasting the occurrence and the amplitude of ionospheric irregularities observed by GPS. The use of the geometric-free combination of GPS dual frequency signals allows to retrieve the Total Electron Content (TEC) along the satellite-to-receiver path, which is the basic trans-ionospheric observable. Based on L1/L2 GPS phase measurements collected at a given station, the TEC high-frequency variability is isolated. A climatological study performed over 10 years in Western Europe shows that TEC irregularities are mostly observed daytime during quiet geomagnetic background in autumn and winter and correspond to classical Medium-Scale Traveling Ionospheric Disturbances (MSTIDs). The latter are generally understood as the ionospheric signature of Atmospheric Gravity Waves (AGWs), either generated in situ (solar terminator) or in the lower atmosphere and propagating upward. Because of its associated strong wind shears, the tropospheric jetstream, occurring mainly during autumn and winter months, constitutes an ideal candidate for AGW generation. This paper analyzes the spatial correlation between the presence of both MSTIDs and strong jetstream over Western Europe. This correlation is positive when the ionospheric pierce point of the satellite is located above regions of interest where wind shears are very large. In practice, we have selected regions for which wind speed is larger than 50 m/s. In addition, the propagation of AGWs up to the ionospheric layer is taken into account by assuming horizontal and vertical velocities of 200 and 50 m/s respectively. It comes that the region of interest of the correlation study is computed using an isotropic slant propagation of the AGW, which is supposed to be generated at a

  4. Comparison of Plateletpheresis on the Fenwal Amicus and Fresenius Com.Tec Cell Separators.

    Science.gov (United States)

    Altuntas, Fevzi; Sari, Ismail; Kocyigit, Ismail; Kaynar, Leylagul; Hacioglu, Sibel; Ozturk, Ahmet; Oztekin, Mehmet; Solmaz, Musa; Eser, Bulent; Cetin, Mustafa; Unal, Ali

    2008-01-01

    SUMMARY: BACKGROUND: A variety of apheresis devices are now available on the market for plateletapheresis. We compared two apheresis instruments (Fenwal Amicus and Fresenius COM.TEC) with regard to processing time, platelet (PLT) yield and efficiency, and white blood cell (WBC) content. MATERIAL AND METHODS: Donors undergoing plateletpheresis were randomly separated into two groups (either the Amicus or the COM.TEC cell separator). RESULTS: In the pre-apheresis setting, 32 plateletpheresis procedures performed with each instrument revealed no significant differences in donors' sex, age, weight, height and total blood volume between the two groups. However, the pre-apheresis PLT count was higher with the COM.TEC than with the Amicus (198 × 10(3)/μl vs. 223 × 10(3)/μl; p = 0.035). The blood volume processed to reach a target PLT yield of ≥3.3 × 10(11) was higher in the COM.TEC compared to the Amicus (3,481 vs. 2,850 ml; p COM.TEC than in the Amicus (61 vs. 44 min; p COM.TEC, respectively, had a PLT count of >3.3 × 10(11) (p = 0.325). All products obtained with both instruments had WBC counts lower than 5 ↔ 10(6), as required. There was no statistical difference with regard to collection efficiency between the devices (55 ± 15 vs. 57 ± 15%; p = 0.477). However, the collection rate was significantly higher with the Amicus compared to the COM.TEC instrument (0.077 ± 0.012 × 10(11) vs. 0.057 ± 0.008 × 10(11) PLT/min; p COM.TEC instrument, the Amicus reached the PLT target yield more quickly.

  5. GS-TEC: the Gaia Spectrophotometry Transient Events Classifier

    CERN Document Server

    Blagorodnova, Nadejda; Wyrzykowski, \\Lukasz; Irwin, Mike; Walton, Nicholas A

    2014-01-01

    We present an algorithm for classifying the nearby transient objects detected by the Gaia satellite. The algorithm will use the low-resolution spectra from the blue and red spectro-photometers on board of the satellite. Taking a Bayesian approach we model the spectra using the newly constructed reference spectral library and literature-driven priors. We find that for magnitudes brighter than 19 in Gaia $G$ magnitude, around 75\\% of the transients will be robustly classified. The efficiency of the algorithm for SNe type I is higher than 80\\% for magnitudes $G\\leq$18, dropping to approximately 60\\% at magnitude $G$=19. For SNe type II, the efficiency varies from 75 to 60\\% for $G\\leq$18, falling to 50\\% at $G$=19. The purity of our classifier is around 95\\% for SNe type I for all magnitudes. For SNe type II it is over 90\\% for objects with $G \\leq$19. GS-TEC also estimates the redshifts with errors of $\\sigma_z \\le$ 0.01 and epochs with uncertainties $\\sigma_t \\simeq$ 13 and 32 days for type SNe I and SNe II re...

  6. Analysis of a dryline-like feature in northern Germany detected by ground-based microwave profiling

    Energy Technology Data Exchange (ETDEWEB)

    Spaenkuch, Dietrich [Leibniz-Soziaetet der Wissenschaften zu Berlin e.V. (Germany); Gueldner, Juergen [Deutscher Wetterdienst, Lindenberg (Germany). Meteorologisches Observatorium Lindenberg - Richard-Assmann-Observatorium; Bender, Michael [Helmholtz-Zentrum Potsdam, Potsdam (DE). Deutsches GeoForschungsZentrum (GFZ); Steinhagen, Hans

    2011-08-15

    Two dryline-like humidity drops without considerable temperature change were detected by the ground-based microwave radiometer profiler (MWRP) at the Richard-Assmann-Observatory Lindenberg (52.21 N, 14.12 E) on April 28, 2007. The detailed analysis of these two events includes cloud radar and radar wind profiler measurements at the site as well as data from the surface synoptic network and from integrated water vapour (IWV) maps derived from GPS. The first more pronounced humidity drop is part of a roughly 200 km long line that meets the criterion of a classical dryline or dewpoint front, namely of a moisture gradient larger 3.5 g m{sup -3} per 100 km. This dewpoint front is ahead of an approaching cold front and is caused by strong downdraft induced by low tropospheric wind shear due to weakening of a midtropospheric high over Germany. It consisted in particular in two kernels of variable size depending on their stage. The fate of the kernels - migration, speed, unification and divorce - is described in detail. Their lifetime was a bit more than 9 hours. The second humidity drop at the site was observed after the passage of the cold front and was caused by dry advection behind the front. Both events are predicted by the numerical weather prediction model COSMO-EU of the German Weather Service to some extent.

  7. Flight Test Result for the Ground-Based Radio Navigation System Sensor with an Unmanned Air Vehicle.

    Science.gov (United States)

    Jang, Jaegyu; Ahn, Woo-Guen; Seo, Seungwoo; Lee, Jang Yong; Park, Jun-Pyo

    2015-11-11

    The Ground-based Radio Navigation System (GRNS) is an alternative/backup navigation system based on time synchronized pseudolites. It has been studied for some years due to the potential vulnerability issue of satellite navigation systems (e.g., GPS or Galileo). In the framework of our study, a periodic pulsed sequence was used instead of the randomized pulse sequence recommended as the RTCM (radio technical commission for maritime services) SC (special committee)-104 pseudolite signal, as a randomized pulse sequence with a long dwell time is not suitable for applications requiring high dynamics. This paper introduces a mathematical model of the post-correlation output in a navigation sensor, showing that the aliasing caused by the additional frequency term of a periodic pulsed signal leads to a false lock (i.e., Doppler frequency bias) during the signal acquisition process or in the carrier tracking loop of the navigation sensor. We suggest algorithms to resolve the frequency false lock issue in this paper, relying on the use of a multi-correlator. A flight test with an unmanned helicopter was conducted to verify the implemented navigation sensor. The results of this analysis show that there were no false locks during the flight test and that outliers stem from bad dilution of precision (DOP) or fluctuations in the received signal quality.

  8. Flight Test Result for the Ground-Based Radio Navigation System Sensor with an Unmanned Air Vehicle

    Directory of Open Access Journals (Sweden)

    Jaegyu Jang

    2015-11-01

    Full Text Available The Ground-based Radio Navigation System (GRNS is an alternative/backup navigation system based on time synchronized pseudolites. It has been studied for some years due to the potential vulnerability issue of satellite navigation systems (e.g., GPS or Galileo. In the framework of our study, a periodic pulsed sequence was used instead of the randomized pulse sequence recommended as the RTCM (radio technical commission for maritime services SC (special committee-104 pseudolite signal, as a randomized pulse sequence with a long dwell time is not suitable for applications requiring high dynamics. This paper introduces a mathematical model of the post-correlation output in a navigation sensor, showing that the aliasing caused by the additional frequency term of a periodic pulsed signal leads to a false lock (i.e., Doppler frequency bias during the signal acquisition process or in the carrier tracking loop of the navigation sensor. We suggest algorithms to resolve the frequency false lock issue in this paper, relying on the use of a multi-correlator. A flight test with an unmanned helicopter was conducted to verify the implemented navigation sensor. The results of this analysis show that there were no false locks during the flight test and that outliers stem from bad dilution of precision (DOP or fluctuations in the received signal quality.

  9. Standardization of GPS data processing

    Energy Technology Data Exchange (ETDEWEB)

    Park, Pil Ho

    2001-06-15

    A nationwide GPS network has been constructed with about 60 permanent GPS stations after late 1990s in Korea. For using the GPS in variety of application area like crustal deformation, positioning, or monitoring upper atmosphere, it is necessary to have ability to process the data precisely. Now Korea Astronomy Observatory has the precise GPS data processing technique in Korea because it is difficult to understand characteristics of the parameters we want to estimate, resolve the integer ambiguity, and analyze many errors. There are three reliable GPS data processing software in the world ; Bernese(University of Berne), GIPSY-OASIS(JPL), GAMIT(MIT). These software allow us to achieve millimeter accuracy in the horizontal position and about 1 cm accuracy vertically even for regional networks with a diameter of several thousand kilometers. But we established the standard of GPS data processing using Bernese as main tool and GIPSY{sub O}ASIS as side.

  10. Update on GPS Modernization Efforts

    Science.gov (United States)

    2015-06-02

    SPACE AND MISSILE SYSTEMS CENTER , GPS constellation consists of 24+ satellites orbiting the earth at - 10,900 nautical miles (Medium Earth Orbit , MEO...estimates instantaneous state of GPS constellation PUBLICALL Y RELEASABLE 4 Civil Cooperation • 1 + Bill ion civil & commercial users worldwide...Observatory • PNT EXCOMS • GPS Partnership Council Maintenance/Security Spectrum 38 Satellites I 31 Set Healthy Baseline Constellation : 24 Satellites

  11. Military GPS User Equipment (MGUE)

    Science.gov (United States)

    2015-04-29

    Space and Missile Systems Center Military GPS User Equipment (MGUE) Lt Col James “Mutt” Wilson Program Manager 29 Apr 15 Information contained in...SUBTITLE Military GPS User Equipment (MGUE) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK...SUPPLEMENTARY NOTES Presented at the GPS Partnership Council 2015 (GPSPC15), held April 29 to May 1, 2015, at the Los Angeles AFB, CA. 14. ABSTRACT

  12. Spread F, GPS phase fluctuations, and medium-scale traveling ionospheric disturbances over Wuhan during solar maximum

    Science.gov (United States)

    Chen, Wei-Sheng; Lee, Chien-Chih; Chu, Fang-Dar; Su, Shin-Yi

    2011-03-01

    This study employs a digisonde and a GPS receiver at Wuhan (30.5°N, 114.4°E), China to observe spread F, GPS phase fluctuations, and medium-scale traveling ionospheric disturbances (MSTIDs) at nighttime in 2000. The MSTIDs are derived from the perturbations of total electron content (TEC). In this study, we explored the seasonal and nighttime occurrence rates as well as the one-to-one correspondences for these phenomena. The results show that, for the seasonal variations, three phenomena all are highly active in summer, which confirms that irregularities over Wuhan mainly relate to MSTIDs. Moreover, all spread F types have a minor occurrence peak in winter but none for the MSTIDs and the GPS phase fluctuations. Besides, none of large GPS phase fluctuations event had occurred during observation periods, which indicates that the strength of irregularities related to MSTIDs are weaker than that of equatorial plasma bubbles. For the nighttime variations, the frequency spread F occurs earlier than other spread F types which implies that disturbances start at the altitude near the F-region peak. For the one-to-one correspondences, the occurrence rates of each spread F type and GPS phase fluctuations are low during MSTIDs occurred. This implies that smaller scale irregularities which are observed as spread F or GPS phase fluctuations may only appear in some phase of MSTIDs.

  13. Ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the destructive seismic activity of August and October 2016 in Central Italy

    Science.gov (United States)

    Contadakis, Michael E.; Arabelos, Demetrios N.; Vergos, George; Spatala, Spyrous; Skeberis, Christos; Xenos, Tomas D.; Biagi, Pierfrancesco; Scordilis, Emmanuel M.

    2017-04-01

    In this paper we investigate the ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the disastrous seismic activity of August and October 2016 in Central Italy . The Total Electron Content (TEC) data of 8 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations (Contadakis et al. 2009, Contadakis et al. 2012, Contadakis et al. 2015). The data acquired for VLF/LF signal observations are from the receiver of Thessaloniki(40.59N, 22,78E), Greece (Skeberis et al. 2015) which monitor the VLF/LF transmitters of the International Network for Frontier Research on Earthquake Precursors (INFREP). A method of normalization according to the distance between the receiver and the transmitter is applied on the above data and then they are processed by the Hilbert Huang Transform (HHT) to produce the corresponding spectra for visual analysis. The results of this investigation indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases as the site and the moment of the earthquake occurrence is approaching, pointing to the earthquake locus. In accordence ,the analyzed data from the receiver of INFREP network in Thessaloniki, Greece show that the signals from the two VLF European transmitters, Tavolara ( Italy) and Le Blanc (France), for wich the transmission path crosses the epicentral zones, indicate enhanced high frequency variations, the last ten days before the moment of the earthquake occurrence. We conclude that the LAIC mechanism through acoustic or gravity wave could explain this phenomenology. Reference Contadakis, M.E., Arabelos, D.N., Asteriadis, G., Spatalas, S.D., Pikridas, C. TEC variations over the Mediterranean during the seismic activity period of the last quarter of 2005 in the area of Greece, Nat. Hazards and Earth Syst. Sci., 8, 1267

  14. Longitude dependent response of the GPS derived ionospheric ROTI to geomagnetic storms

    Science.gov (United States)

    Tanna, H. J.; Pathak, K. N.

    2014-08-01

    The local time dependent effects of geomagnetic storm on the ionospheric TEC and Rate of change of TEC Index (ROTI) are studied here using the GPS data for four different low latitude stations: Ogaswara, Japan (24.29 °N, 153.91 °E; Geomagnetic: 17.21 °N, 136.16 °W); Surat, India (21.16 °N, 72.78 °E; Geomagnetic: 12.88 °N, 146.91 °E); Bogota, Colombia (4.64 °N, -74.09 °E; Geomagnetic: 14.42 °N, 1.67 °W); and Kokee park Waimea, Hawaii, US (22.12 °N, -159.67 °E; Geomagnetic: 22.13 °N, 91.19 °W). The solar wind velocity and geomagnetic indices: Dst, Kp and IMF Bz are utilized to validate the geomagnetic storms registered during the years 2011 and 2012. Using the GPS based TEC data and computed values of ROTI, the storm induced ionospheric irregularities generation and inhibition has been studied for all stations. The present study suggests that, the F-region irregularities of a scale length of few kilometers over the magnetic equator are locally affected by geomagnetic storms. This study also shows a good agreement (70-84 %) with the Aaron's criteria (Aarons, Radio Sci., 26:1131-1149, 1991; Biktash, Ann. Geophys., 19:731-739, 2004) as significant absence and enhancement of ROTI was found to be influenced by the local time of the negative peak of Dst index association.

  15. Climatological study of ionospheric irregularities over the European mid-latitude sector with GPS

    Science.gov (United States)

    Wautelet, Gilles; Warnant, René

    2014-03-01

    High-frequency variability of the ionosphere, or irregularities, constitutes the main threat for real-time precise positioning techniques based on Global Navigation Satellite Systems (GNSS) measurements. Indeed, during periods of enhanced ionospheric variability, GNSS users in the field—who cannot verify the integrity of their measurements—will experience positioning errors that can reach several decimeters, while the nominal accuracy of the technique is cm-level. In the frame of this paper, a climatological analysis of irregularities over the European mid-latitude region is presented. Based on a 10 years GPS dataset over Belgium, the work analyzes the occurrence rate (as a function of the solar cycle, season and local time) as well as the amplitude of ionospheric irregularities observed at a single GPS station. The study covers irregularities either due to space weather events (solar origin) or of terrestrial origin. If space weather irregularities are responsible for the largest effects in terms of ionospheric error, their occurrence rate highly depends on solar activity. Indeed, the occurrence rate of ionospheric irregularities is about 9 % during solar maximum, whereas it drops to about 0 % during medium or low solar activity periods. Medium-scale ionospheric disturbances (MSTIDs) occurring during daytime in autumn/winter are the most recurrent pattern of the time series, with yearly proportions slightly varying with the solar cycle and an amplitude of about 10 % of the TEC background. Another recurrent irregularity type, though less frequent than MSTIDs, is the noise-like variability in TEC observed during summer nighttime, under quiet geomagnetic conditions. These summer nighttime irregularities exhibit amplitudes ranging between 8 and 15 % of the TEC background.

  16. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    ZouYu-hua; XuJi-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, N~, from ground-based GPS beacon observations. After simplifying the relation between N. and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections. To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallelbeam tomogtTaphy is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Ne are obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demonstrate that imaging of the ionospheric electron density distribution from GPS beacon observations is reasonable in theor yand feasible in practice.

  17. Inversion of Ionospheric Electron Density from GPS Beacon Observations

    Institute of Scientific and Technical Information of China (English)

    Zou Yu-hua; Xu Ji-sheng

    2003-01-01

    This paper studies the mathematical foundation of time-dependent three-dimensional (3-D) computerized ionospheric tomography (CIT) for reconstructing ionospheric electron density, Ne, from ground-based GPS beacon observations. After simplifying the relation between Ne and time,the time-dependent 3-D inversion in consideration is reduced to a 3-D tomography with incomplete projections.To see clearly the effects of the incompleteness on the quality of reconstruction under 3-D condition, the formula of 3-D parallel-beam tomography is deduced theoretically. After establishing the mathematical foundation, simulations based on actual GPS ray paths with the help of the IRI-90 model are performed,and reasonable time-dependent 3-D distribution images of Neare obtained when taking proper layout of the network and allowing variable resolutions. The quality of the reconstruction is rather good when compared with the images from the IRI-90 model directly. Therefore, results in this paper demon-strate that imaging of the ionospheric electron density distri-bution from GPS beacon observations is reasonable in theory and feasible in practice.

  18. Ground-based Infrared Observations of Water Vapor and Hydrogen Peroxide in the Atmosphere of Mars

    Science.gov (United States)

    Encrenaz, T.; Greathouse, T. K.; Bitner, M.; Kruger, A.; Richter, M. J.; Lacy, J. H.; Bézard, B.; Fouchet, T.; Lefevre, F.; Forget, F.; Atreya, S. K.

    2008-11-01

    Ground-based observations of water vapor and hydrogen peroxide have been obtained in the thermal infrared range, using the TEXES instrument at the NASA Infrared Telescope Facility, for different times of the seasonal cycle.

  19. Informing hydrological models with ground-based time-lapse relative gravimetry: potential and limitations

    DEFF Research Database (Denmark)

    Bauer-Gottwein, Peter; Christiansen, Lars; Rosbjerg, Dan

    2011-01-01

    Coupled hydrogeophysical inversion emerges as an attractive option to improve the calibration and predictive capability of hydrological models. Recently, ground-based time-lapse relative gravity (TLRG) measurements have attracted increasing interest because there is a direct relationship between ...

  20. Changes in ground-based solar ultraviolet radiation during fire episodes: a case study

    CSIR Research Space (South Africa)

    Wright, CY

    2013-09-01

    Full Text Available about the relationship between fires and solar UVR without local high-quality column or ground-based ambient air pollution (particulate matter in particular) data; however, the threat to public health from fires was acknowledged....

  1. Ionospheric scintillation detection based on GPS observations, a case study over Iran

    Science.gov (United States)

    Sobhkhiz Miandehi, Sahar; Alizadeh Elizei, M. Mahdi; Schuh, Harald

    2017-04-01

    Global Positioning System (GPS) which is used extensively for various purposes such as navigation, surveying, remote sensing and telecommunication, is strongly affected by the earth's upper atmosphere, the ionosphere. Ionosphere is a highly variable region with complex physical characteristics in which the density of free electrons are large enough to have considerable effects on signals' propagation travelling through this dispersive medium. As GPS signals travel through the ionosphere, they may experience rapid amplitude fluctuations or unexpected phase changes. This is referred to as ionospheric scintillation. Ionospheric scintillation which is caused by small scale irregularities in the electron density, is one of the dominant propagation disturbances at radio frequency signals. These irregularities severely affect the accuracy and reliability of GPS measurements. Therefore it is necessary to investigate ionospheric scintillation and its effects on GPS observations. The focus of this paper is to detect ionospheric scintillations over Iran's region, during different periods of solar activity and to investigate these effects on GPS observations in more detail. Furthermore the effects of these irregularities on regional modeling of ionosphere over Iran is also investigated. The results show that effectiveness of this phenomenon depends on geographic location, local time and global geomagnetic storm index (kp index). The required data for this investigation are ground based measurements of permanent GPS stations over Iran, established by the National Cartographic Center of Iran (NCC).

  2. System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator

    Science.gov (United States)

    2006-08-01

    System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator Jae-Jun Kim∗ and Brij N. Agrawal † Department of...TITLE AND SUBTITLE System Identification and Automatic Mass Balancing of Ground-Based Three-Axis Spacecraft Simulator 5a. CONTRACT NUMBER 5b...and Dynamics, Vol. 20, No. 4, July-August 1997, pp. 625-632. 6Schwartz, J. L. and Hall, C. D., “ System Identification of a Spherical Air-Bearing

  3. Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009: external high speed stream drivers

    Directory of Open Access Journals (Sweden)

    O. P. Verkhoglyadova

    2013-02-01

    Full Text Available We study solar wind–ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23 – 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs. The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA events. The JPL Global Ionospheric Map (GIM software and the GPS total electron content (TEC database were used to calculate the vertical TEC (VTEC and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU near local noon (12:00 to 14:00 LT in 2008. In 2009 during the minimum geomagnetic activity (MGA interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10–22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU. The ionospheric VTEC changes during 2008–2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed.

    We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008–2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3

  4. Comparison of plateletpheresis on the Fenwal Amicus, Fresenius COM.TEC, and Trima Accel Cell separators.

    Science.gov (United States)

    Keklik, Muzaffer; Eser, Bulent; Kaynar, Leylagul; Sivgin, Serdar; Keklik, Ertugrul; Solmaz, Musa; Ozturk, Ahmet; Buyukoglan, Ruksan; Yay, Mehmet; Cetin, Mustafa; Unal, Ali

    2015-06-01

    Blood component donations by apheresis have become more common in modern blood transfusion practices. We compared three apheresis instruments (Fenwal Amicus, Fresenius COM.TEC, and Trima Accel) with regard to platelet (PLT) yield, collection efficiency (CE), and collection rate (CR). The single-needle or double-needle plateletpheresis procedures of the three instruments were compared in a retrospective, randomized study in 270 donors. The blood volume processed was higher in the COM.TEC compared with the Amicus and Trima. Also there was a significantly higher median volume of ACD used in collections on the COM.TEC compared with the Amicus and Trima. The PLT yield was significantly lower with the COM.TEC compared with the Amicus and Trima. Additionally, the CE was significantly lower with the COM.TEC compared with the Amicus and Trima. There was no significant difference in median separation time and CR between the three groups. When procedures were compared regarding CE by using Amicus device, it was significantly higher in single-needle than double-needle plateletpheresis. When double-needle Amicus system was compared with double-needle COM.TEC system, CE and PLT yield were significantly higher with Amicus system. When single-needle Amicus system was compared with single-needle Trima system, CE and PLT yield were significantly higher with Trima system. All instruments collected PLTs efficiently. However, the CE was lower with the COM.TEC compared with the Amicus and Trima. Also, we found Amicus single-needle system collected PLTs more efficiently compared with the double-needle system. CE and PLT yields were significantly higher with the single-needle Trima instrument compared with the single-needle Amicus device.

  5. Hastighedskort for Danmark vha. GPS

    DEFF Research Database (Denmark)

    Andersen, Ove; Lahrmann, Harry; Torp, Kristian

    2011-01-01

    Hastighed på vejnettet er en central metrik indenfor trafikplanlægning og trafikoptimering. I denne artikel beskrives, hvorledes et hastighedskort for hele Danmark er skabt udelukkende vha. GPS data. To tilgangsvinkler til at beregne hastigheder vha. GPS data er præsenteret. Dette er hhv. en punk...... foretages med et beskedent budget er uvist....

  6. 77 FR 19719 - Whirlpool Corporation Including On-Site Leased Workers From Career Solutions TEC Staffing, IBM...

    Science.gov (United States)

    2012-04-02

    ... Solutions TEC Staffing, IBM Corporation, TEK Systems Penske Logistics, Eurest, Canteen, Kelly Services, Inc..., Eurest, Canteen, Kelly Services, Inc., Prodriver, Arkansas Warehouse, Inc., and Andrews...

  7. GPS Position Time Series @ JPL

    Science.gov (United States)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  8. GPS Position Time Series @ JPL

    Science.gov (United States)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  9. Evidential recovery from GPS devices

    Directory of Open Access Journals (Sweden)

    Brian Cusack

    Full Text Available Global Positioning Systems (GPS have become more affordable, are now widely used in motor vehicles and in other frequently used applications. As a consequence GPS are increasingly becoming an important source of evidential data for digital forensic investigations. This paper acknowledges there are only disparate documents for the guidance of an investigator when extracting evidence form such systems. The focus of this paper is to provide the technical details of recovering artifacts from four GPS currently available to the New Zealand market. Navman brand GPS are used, following a forensically robust process. The steps of the process are described, results analysed and the associated risks are discussed. In addition, the paper discusses techniques related to the visual presentation of evidence suitable for Google Maps. Automation attempts to speed up the analysis to visualization steps are also included. The outcome is a road map that may assist digital forensic investigators develop GPS examination strategies for implementation in their own organizations.

  10. Influences of the day-night differences of ionosphere on the GPS DCB estimation

    Science.gov (United States)

    Zhang, Donghe; Zhang, Shunrong; Coster, Anthea; Hao, Yongqiang; Xiao, Zuo

    2016-04-01

    The estimation of differential code bias (DCB) of GPS system is one of the necessary steps for total electron content (TEC) derivation from GPS measurements. Usually, the method for estimating the GPS DCBs follows the assumption of the gentle temporal and spatial variation of the ionosphere, but this assumption is just an approximation because of the ionosphere's inherent variability. It has been indicated that the estimated GPS satellite DCBs are sometimes influenced by the ionospheric conditions. Here, we demonstrate a possible influence of ionospheric condition that differs between day and night on the estimated DCBs from measurements of a single GPS station. It is found that the average standard deviations (STDs) of the satellite DCBs estimated with daytime data are higher than that with the nighttime data. To reduce this day-night difference effect on GPS DCB determination, we use an improved estimation method based on the primary features of the ionospheric variability with local time. A local time dependent weighting function was introduced into the original least-squared DCBs estimation algorithm. A test with data for BJFS station (39.60°N, 115.89°E) in 2001 indicates that the STD of the DCBs decreases from 2.533 TECU to 2.308 TECU, or by 8.9%, after the improved method was applied. For comparison, another test for the same station in 2009 indicates that the STD decreases from 1.344TECU to 1.295 TECU. Reference Li, LX. DH. Zhang., SR. Zhang., et al. Influences of the day-night differences of ionospheric variability on the estimation of GPS differential code bias, Radio Science, 2015, DOI: 10.1002/2014RS005565 Zhang D H, Shi H, Jin Y Q, et al. The variation of the estimated GPS instrumental bias and its possible connection with ionospheric variability. Sci China Tech Sci, 2014, 57: 67-79, doi: 10.1007/s11431-013-5419-7 Zhang D H, Zhang W,Li Q., Accuracy analysis of the GPS instrumental bias estimated from observations in middle and low latitudes

  11. Analysis of the 2008 heavy snowfall over South China using GPS PWV measurements from the Tibetan Plateau

    Science.gov (United States)

    Xie, Y.; Wei, F.; Chen, G.; Zhang, T.; Hu, L.

    2010-06-01

    Four successive storms with freezing rain and snow blanketed South China from 10 January-2 February 2008, when the precipitation increased more than 200%-300% above the average for the corresponding period. The unusual atmospheric circulation associated with these disasters was caused by many complex physical processes, one of which was the active southern branch of currents over low latitude ocean areas which provided plenty of water vapor for South China. The ground-based GPS Precipitable Water Vapor (PWV) measurements on the Tibetan Plateau, supported by the China and Japan Intergovernmental Cooperation Program (JICA), has compensated for the lack of conventional observations of atmospheric water vapor in this area and provided a good opportunity to analyze the character of the water vapor transport in the four heavy precipitation processes. It was found that the GPS stations located on the southeastern Tibetan Plateau were on the route of the water vapor transport during 25 January-29 January and 31 January-2 February when two heavy precipitation events occurred over South China. The increasing trend from the one to two days pre-observation by the GPS stations was then associated with the heavy precipitation. Precipitation during 10 January-16 January and 18 January-22 January was significantly related to the abnormal variation of the one day pre-observation by the GPS stations located on the northeastern Tibetan Plateau. This research indicates that ground-based GPS measurements are applicable to data assimilation in operational numerical models.

  12. Analysis of the 2008 heavy snowfall over South China using GPS PWV measurements from the Tibetan Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Y. [Texas A and M Univ., College Station, TX (United States). Dept. of Atmospheric Sciences; Wei, F.; Chen, G.; Zhang, T. [Chinese Academy of Meteorological Sciences, Beijing (China). State Key Lab. of Severe Weather; Hu, L. [Texas A and M Univ., College Station, TX (United States). Dept. of Oceanography

    2010-07-01

    Four successive storms with freezing rain and snow blanketed South China from 10 January-2 February 2008, when the precipitation increased more than 200%- 300% above the average for the corresponding period. The unusual atmospheric circulation associated with these disasters was caused by many complex physical processes, one of which was the active southern branch of currents over low latitude ocean areas which provided plenty of water vapor for South China. The ground-based GPS Precipitable Water Vapor (PWV) measurements on the Tibetan Plateau, supported by the China and Japan Intergovernmental Cooperation Program (JICA), has compensated for the lack of conventional observations of atmospheric water vapor in this area and provided a good opportunity to analyze the character of the water vapor transport in the four heavy precipitation processes. It was found that the GPS stations located on the southeastern Tibetan Plateau were on the route of the water vapor transport during 25 January-29 January and 31 January-2 February when two heavy precipitation events occurred over South China. The increasing trend from the one to two days pre-observation by the GPS stations was then associated with the heavy precipitation. Precipitation during 10 January-16 January and 18 January-22 January was significantly related to the abnormal variation of the one day preobservation by the GPS stations located on the northeastern Tibetan Plateau. This research indicates that ground-based GPS measurements are applicable to data assimilation in operational numerical models. (orig.)

  13. Analysis of the 2008 heavy snowfall over South China using GPS PWV measurements from the Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    Y. Xie

    2010-06-01

    Full Text Available Four successive storms with freezing rain and snow blanketed South China from 10 January–2 February 2008, when the precipitation increased more than 200%–300% above the average for the corresponding period. The unusual atmospheric circulation associated with these disasters was caused by many complex physical processes, one of which was the active southern branch of currents over low latitude ocean areas which provided plenty of water vapor for South China. The ground-based GPS Precipitable Water Vapor (PWV measurements on the Tibetan Plateau, supported by the China and Japan Intergovernmental Cooperation Program (JICA, has compensated for the lack of conventional observations of atmospheric water vapor in this area and provided a good opportunity to analyze the character of the water vapor transport in the four heavy precipitation processes. It was found that the GPS stations located on the southeastern Tibetan Plateau were on the route of the water vapor transport during 25 January–29 January and 31 January–2 February when two heavy precipitation events occurred over South China. The increasing trend from the one to two days pre-observation by the GPS stations was then associated with the heavy precipitation. Precipitation during 10 January–16 January and 18 January–22 January was significantly related to the abnormal variation of the one day pre-observation by the GPS stations located on the northeastern Tibetan Plateau. This research indicates that ground-based GPS measurements are applicable to data assimilation in operational numerical models.

  14. De GPS al mapa

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available Las coordenadas Lambert obtenidas a partir de mediciones con equipos GPS de mano, llamados a veces navegadores, en ciertos casos confunden al usuario, por diferir claramente de su posición real al ser graficadas en un mapa del Instituto Geográfico Nacional (IGN: Esto puede resolverse con suficiente exactitud mediante una transformación de Molodensky, seguida de la correspondiente proyección cartográfica. Sin embargo, los tres parámetros necesarios para la transformación, supuestamente válidos para Costa Rica, se encuentran en muchas variantes y producen obviamente resultados diferentes. En este trabajo se analizan los fundamentos del problema y sus posibles soluciones, culminando con un estudio comparativo de ocho casos, que permite seleccionar los valores más adecuados para los parámetros.

  15. Response of equatorial and low latitude ionosphere to 2015 St. Patrick's Day super geomagnetic storm: Results from a chain of ground based observations over Indian region

    Science.gov (United States)

    Samireddipalle, Sripathi; Singh, Ram; Sreekumar, Sreeba; Suneel Kumar, Buduru

    2016-07-01

    In this paper, we present unique results of equatorial and low latitude ionosphere response to one of the major geomagnetic storms of the current solar cycle that occurred during 17-18 March 2015 where Dst reached its minimum of -228 nT. Here we utilized data from magnetometers, chain of ionosondes located at Tirunelveli (8.73°N, 77.70°E; geom: 0.320N), Hyderabad (17.360N, 78.470E; geom: 8.760N) and Allahabad (25.45°N, 81.85°E; geom: 16.50N) along with multi station GPS receivers over Indian sector. The observations showed a remarkable increase of h'F to as high as ~560 km over Tirunelveli (magnetic equator) with vertical drift of ~70 m/s at 13:30 UT due to direct penetration of storm time eastward electric fields which exactly coincided with the local time of Pre-Reversal Enhancement (PRE) and caused intense ESF irregularities in ionosondes and scintillations in GPS receivers at wide latitudes. Plasma irregularities are so intense that their signatures are seen in Allahabad/Lucknow. Stormtime thermospheric meridional winds as estimated using two ionosondes suggest the equatorward surge of gravity waves with period of ~2 hrs. Suppression of anomaly crest on the subsequent day of the storm suggests the complex role of disturbance dynamo electric fields and disturbance wind effects. Our results also show an interesting feature of Traveling Ionospheric Disturbances (TIDs) possibly associated with disturbance meridional wind surge during recovery phase. In addition, noteworthy observations are nighttime westward zonal drifts and PRE related TEC enhancements at anomaly crests during main phase and CEJ signatures during recovery phase.

  16. An empirical model of ionospheric total electron content (TEC near the crest of the equatorial ionization anomaly (EIA

    Directory of Open Access Journals (Sweden)

    Hajra Rajkumar

    2016-01-01

    Full Text Available We present a geomagnetic quiet time (Dst > −50 nT empirical model of ionospheric total electron content (TEC for the northern equatorial ionization anomaly (EIA crest over Calcutta, India. The model is based on the 1980–1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2 at the Haringhata (University of Calcutta, India: 22.58° N, 88.38° E geographic; 12.09° N, 160.46° E geomagnetic ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89–0.99 between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of ~50–100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400–0500 LT minimum and near-noon (1300–1400 LT maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-σ range from the observed mean values.

  17. An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)

    Science.gov (United States)

    Hajra, Rajkumar; Chakraborty, Shyamal Kumar; Tsurutani, Bruce T.; DasGupta, Ashish; Echer, Ezequiel; Brum, Christiano G. M.; Gonzalez, Walter D.; Sobral, José Humberto Andrade

    2016-07-01

    We present a geomagnetic quiet time (Dst > -50 nT) empirical model of ionospheric total electron content (TEC) for the northern equatorial ionization anomaly (EIA) crest over Calcutta, India. The model is based on the 1980-1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2) at the Haringhata (University of Calcutta, India: 22.58° N, 88.38° E geographic; 12.09° N, 160.46° E geomagnetic) ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz) signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89-0.99) between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of ~50-100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400-0500 LT) minimum and near-noon (1300-1400 LT) maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-σ range from the observed mean values.

  18. DKK1 mediated inhibition of Wnt signaling in postnatal mice leads to loss of TEC progenitors and thymic degeneration.

    Directory of Open Access Journals (Sweden)

    Masako Osada

    Full Text Available BACKGROUND: Thymic epithelial cell (TEC microenvironments are essential for the recruitment of T cell precursors from the bone marrow, as well as the subsequent expansion and selection of thymocytes resulting in a mature self-tolerant T cell repertoire. The molecular mechanisms, which control both the initial development and subsequent maintenance of these critical microenvironments, are poorly defined. Wnt signaling has been shown to be important to the development of several epithelial tissues and organs. Regulation of Wnt signaling has also been shown to impact both early thymocyte and thymic epithelial development. However, early blocks in thymic organogenesis or death of the mice have prevented analysis of a role of canonical Wnt signaling in the maintenance of TECs in the postnatal thymus. METHODOLOGY/PRINCIPAL FINDINGS: Here we demonstrate that tetracycline-regulated expression of the canonical Wnt inhibitor DKK1 in TECs localized in both the cortex and medulla of adult mice, results in rapid thymic degeneration characterized by a loss of DeltaNP63(+ Foxn1(+ and Aire(+ TECs, loss of K5K8DP TECs thought to represent or contain an immature TEC progenitor, decreased TEC proliferation and the development of cystic structures, similar to an aged thymus. Removal of DKK1 from DKK1-involuted mice results in full recovery, suggesting that canonical Wnt signaling is required for the differentiation or proliferation of TEC populations needed for maintenance of properly organized adult thymic epithelial microenvironments. CONCLUSIONS/SIGNIFICANCE: Taken together, the results of this study demonstrate that canonical Wnt signaling within TECs is required for the maintenance of epithelial microenvironments in the postnatal thymus, possibly through effects on TEC progenitor/stem cell populations. Downstream targets of Wnt signaling, which are responsible for maintenance of these TEC progenitors may provide useful targets for therapies aimed at

  19. 75 FR 8928 - Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800 Interface Control Working Group (ICWG...

    Science.gov (United States)

    2010-02-26

    ... Department of the Air Force Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800Interface Control Working Group... an Interface Control Working Group (ICWG) teleconference meeting for document/s IS-GPS-200E (NAVSTAR GPS Space Segment/Navigation User Interfaces), IS-GPS-705A (NAVSTAR GPS Space Segment/User Segment...

  20. Relations between Arctic large-scale TEC changes and scintillations over Greenland

    DEFF Research Database (Denmark)

    Durgonics, Tibor; Høeg, Per; von Benzon, Hans-Henrik

    The increasing dependence on GNSS-based methods and technologies for global or regionalnavigation and communication has raised concerns about the impact of space weather on thesesystems. Temporal and spatial ionosphere variations caused by driving forces, such as changes insolar radiation, solar...... wind, and the Earth’s magnetic field contribute to errors in satellite navigationpositioning and communication systems. In this study we will focus on the impact of space weatherin the Arctic region related to total electron content (TEC) and scintillation changes.Measurements from the GNSS network...... elements and parameters (such as the auroral oval and the auroralelectrojet), driving these changes in the Greenland TEC, S4 and σϕ distributions, in order to come upwith appropriate algorithms and tools for monitoring and predicting Arctic TEC and scintillationlarge-scale patterns....

  1. The theory of event coding (TEC as embodied-cognition framework

    Directory of Open Access Journals (Sweden)

    Bernhard eHommel

    2015-09-01

    Full Text Available The concept of embodied cognition attracts enormous interest but neither is the concept particularly well-defined nor is the related research guided by systematic theorizing. To improve this situation the Theory of Event Coding (TEC is suggested as a suitable theoretical framework for theorizing about cognitive embodiment—which however presupposes giving up the anti-cognitivistic attitude inherent in many embodiment approaches. The article discusses the embodiment-related potential of TEC, and the way and degree to which it addresses Wilson’s (2002 six meanings of the embodiment concept. In particular, it is discussed how TEC considers human cognition to be situated, distributed, and body-based, how it deals with time pressure, how it delegates work to the environment, and in which sense it subserves action.

  2. The theory of event coding (TEC) as embodied-cognition framework.

    Science.gov (United States)

    Hommel, Bernhard

    2015-01-01

    The concept of embodied cognition attracts enormous interest but neither is the concept particularly well-defined nor is the related research guided by systematic theorizing. To improve this situation the theory of event coding (TEC) is suggested as a suitable theoretical framework for theorizing about cognitive embodiment-which, however, presupposes giving up the anti-cognitivistic attitude inherent in many embodiment approaches. The article discusses the embodiment-related potential of TEC, and the way and degree to which it addresses Wilson's (2002) six meanings of the embodiment concept. In particular, it is discussed how TEC considers human cognition to be situated, distributed, and body-based, how it deals with time pressure, how it delegates work to the environment, and in which sense it subserves action.

  3. Time-dependent prediction degredation assessment of neural-networks-based TEC forecasting models

    Directory of Open Access Journals (Sweden)

    Th. D. Xenos

    2003-01-01

    Full Text Available An estimation of the difference in TEC prediction accuracy achieved when the prediction varies from 1 h to 7 days in advance is described using classical neural networks. Hourly-daily Faraday-rotation derived TEC measurements from Florence are used. It is shown that the prediction accuracy for the examined dataset, though degrading when time span increases, is always high. In fact, when a relative prediction error margin of ± 10% is considered, the population percentage included therein is almost always well above the 55%. It is found that the results are highly dependent on season and the dataset wealth, whereas they highly depend on the foF2 - TEC variability difference and on hysteresis-like effect between these two ionospheric characteristics.

  4. Climatology of vTEC at midnight over mid-latitude regions using PCA

    Science.gov (United States)

    Natali, M. Paula; Meza, Amalia

    2017-04-01

    At night the content of the electron density at mid-latitude is mainly controlled by loss processes, recombination and electron movement, which are related by the continuity equation. The vertical wind plays an important role in these processes. Global vertical Total Electron Content (vTEC) maps produced by the International Global Navigation Satellite System (GNSS) Service, the Horizontal Wind Model 2007 (HWM07) and the International Reference Ionosphere (IRI) 2012 model are used to describe the climatology at midnight over mid-latitude regions during 2000-2002. In particular, four regions were selected. They are approximately centered in zero magnetic declination, two in the northern hemisphere and two in southern hemisphere. They are located near and far from geomagnetic poles respectively. Principal Components Analysis (PCA) technique highlights the spatial-temporal variations to the overall vTEC variability which can be well represented by an orthogonal base. Indeed, we show for the four selected regions the contributions of the first three modes account for more than 95% of its variability. PCA results show that vTEC variability respond to vertical wind variation with decreasing values of about 10% -15% with the action of a vertical wind lasting for two hours. The Mid-latitude Summer Night Anomaly (MSNA), which is directly related with vertical wind, is present in regions far from geomagnetic poles. A remnant effect of the winter anomaly is also observed, in regions near geomagnetic poles. A longitudinal variation for mid-latitude ionospheric vTEC with maximum values in equinoxes, associated with negative and positive magnetic declination in all regions is observed. For the IRI model, PCA results, are quite similar but the mean values are lower than the obtained with the Global vTEC Maps. These data show the MSNA but not the remnant of the winter anomaly. In all regions the longitudinal variation is present with the same seasonal variation as Global vTEC Maps.

  5. Hastighedskort for Danmark vha. GPS

    DEFF Research Database (Denmark)

    Andersen, Ove; Lahrmann, Harry; Torp, Kristian

    2011-01-01

    Hastighed på vejnettet er en central metrik indenfor trafikplanlægning og trafikoptimering. I denne artikel beskrives, hvorledes et hastighedskort for hele Danmark er skabt udelukkende vha. GPS data. To tilgangsvinkler til at beregne hastigheder vha. GPS data er præsenteret. Dette er hhv. en....... Opsummeret anses den turbaseret for at beregne det mest akkurate estimat, men metoden er meget datakrævende. Det er derfor nødvendigt at have den punktbaserede at falde tilbage på. Generelt mangler metoder til beregning af hastigheder vha. GPS data at blive valideret. Hvordan en sådan validering kan...

  6. GPS observations of medium-scale traveling ionospheric disturbances over Europe

    Directory of Open Access Journals (Sweden)

    Y. Otsuka

    2013-02-01

    Full Text Available Two-dimensional structures of medium-scale traveling ionospheric disturbances (MSTIDs over Europe have been revealed, for the first time, by using maps of the total electron content (TEC obtained from more than 800 GPS receivers of the European GPS receiver networks. From statistical analysis of the TEC maps obtained 2008, we have found that the observed MSTIDs can be categorized into two groups: daytime MSTID and nighttime MSTID. The daytime MSTID frequently occurs in winter. Its maximum occurrence rate in monthly and hourly bin exceeds 70% at lower latitudes over Europe, whereas it is approximately 45% at higher latitudes. Since most of the daytime MSTIDs propagate southward, we speculate that they could be caused by atmospheric gravity waves in the thermosphere. The nighttime MSTIDs also frequently occur in winter but most of them propagate southwestward, in a direction consistent with the theory that polarization electric fields play an important role in generating the nighttime MSTIDs. The nighttime MSTID occurrence rate shows distinct latitudinal difference: The maximum of the occurrence rate in monthly and hourly bin is approximately 50% at lower latitudes in Europe, whereas the nighttime MSTID was rarely observed at higher latitudes. We have performed model calculations of the plasma density perturbations caused by a gravity wave and an oscillating electric field to reproduce the daytime and nighttime MSTIDs, respectively. We find that TEC perturbations caused by gravity waves do not show dip angle dependencies, while those caused by the oscillating electric field have a larger amplitude at lower latitudes. These dip angle dependencies of the TEC perturbation amplitude could contribute to the latitudinal variation of the MSTID occurrence rate. Comparing with previous studies, we discuss the longitudinal difference of the nighttime MSTID occurrence rate, along with the E- and F-region coupling processes. The seasonal variation, of the

  7. Equatorial ionospheric electrodynamics observations in the African sector using recently deployed magnetometer and GPS networks

    Science.gov (United States)

    Yizengaw, Endawoke

    Recent ground-and space-based observations have shown that geomagnetic storms can have dramatic longitudinal differences in equatorial ionospheric electrodynamics, such as enhanced generation of F-region plasma irregularities and super fountain effect at low latitudes. For example, satellite observations have shown very unique equatorial ionospheric density struc-tures in the African region. The African region is the longitude sector where the peak in large scale bubble activity (zonal width, depletion level, and spacing) is maximum. No other region in the globe shows similar characteristics. Most recent in situ density observations from C/NOFS also reveal similar maximal bubble activities in Africa. However, the dearth of ground-based in-strumentation in the region makes it impossible to confirm these unique equatorial ionospheric structures from the ground and that leads the investigation of the physics into speculative dead ends. This initiated several open questions, which include: What are the possible governing mechanisms that create unique equatorial structures in Africa? In order to answer such open questions, recently limited progress has been made and very few ground-based instruments, including AMBER magnetometers and ACORN GPS network, have been either deployed in the region or in process. Some of many objectives of AMBER magnetometers network, in coordination with ground-and space-based GPS receiver observations, is to understand the fundamental electrodynamics that govern equatorial ionospheric motion and the penetration of ULF Pc5 wave into equatorial latitudes and its impact on the equatorial electrodynamics. This paper presents initial results from AMBER magnetometer network. The initial electro-dynamics result in Africa is also compared with similar observations in the American sector. The electron density structure in response to the electrodynamics is also investigated using the available ground-based GPS receivers in the region as well as data

  8. TEC variations along an East Euro-African chain during 5th April 2010 geomagnetic storm

    Science.gov (United States)

    Shimeis, A.; Borries, C.; Amory-Mazaudier, C.; Fleury, R.; Mahrous, A. M.; Hassan, A. F.; Nawar, S.

    2015-05-01

    In this paper, we analyzed the variations of TEC along a latitudinal East Euro-African chain, during the storm of April 5, 2010. We observed a large asymmetry between the two hemispheres. We detected the presence of a TID in the Northern hemisphere on April 5. The propagation time of the TID from high to low latitudes and the speed of the TID was determined. On April 5, 6 and 7, we observed a decrease of the TEC and changes of the NO+ in the Northern hemisphere. This depletion is caused by the large-scale thermospheric wind disturbances due to Joule heating dissipation in the auroral zone.

  9. Reception Test of Petals for the End Cap TEC+ of the CMS Silicon Strip Tracker

    CERN Document Server

    Bremer, R; Klein, Katja; Schmitz, Stefan Antonius; Adler, Volker; Adolphi, Roman; Ageron, Michel; Agram, Jean-Laurent; Atz, Bernd; Barvich, Tobias; Baulieu, Guillaume; Beaumont, Willem; Beissel, Franz; Bergauer, Thomas; Berst, Jean-Daniel; Blüm, Peter; Bock, E; Bogelsbacher, F; de Boer, Wim; Bonnet, Jean-Luc; Bonnevaux, Alain; Boudoul, Gaelle; Bouhali, Othmane; Braunschweig, Wolfgang; Brom, Jean-Marie; Butz, Erik; Chabanat, Eric; Chabert, Eric Christian; Clerbaux, Barbara; Contardo, Didier; De Callatay, Bernard; Dehm, Philip; Delaere, Christophe; Della Negra, Rodolphe; Dewulf, Jean-Paul; D'Hondt, Jorgen; Didierjean, Francois; Dierlamm, Alexander; Dirkes, Guido; Dragicevic, Marko; Drouhin, Frédéric; Ernenwein, Jean-Pierre; Esser, Hans; Estre, Nicolas; Fahrer, Manuel; Fernández, J; Florins, Benoit; Flossdorf, Alexander; Flucke, Gero; Flügge, Günter; Fontaine, Jean-Charles; Freudenreich, Klaus; Frey, Martin; Friedl, Markus; Furgeri, Alexander; Giraud, Noël; Goerlach, Ulrich; Goorens, Robert; Graehling, Philippe; Grégoire, Ghislain; Gregoriev, E; Gross, Laurent; Hansel, S; Haroutunian, Roger; Hartmann, Frank; Heier, Stefan; Hermanns, Thomas; Heydhausen, Dirk; Heyninck, Jan; Hosselet, J; Hrubec, Josef; Jahn, Dieter; Juillot, Pierre; Kaminski, Jochen; Karpinski, Waclaw; Kaussen, Gordon; Keutgen, Thomas; Klanner, Robert; König, Stefan; Kosbow, M; Krammer, Manfred; Ledermann, Bernhard; Lemaître, Vincent; De Lentdecker, Gilles; Linn, Alexander; Lounis, Abdenour; Lübelsmeyer, Klaus; Lumb, Nicholas; Maazouzi, Chaker; Mahmoud, Tariq; Michotte, Daniel; Militaru, Otilia; Mirabito, Laurent; Müller, Thomas; Neukermans, Lionel; Ollivetto, C; Olzem, Jan; Ostapchuk, Andrey; Pandoulas, Demetrios; Pein, Uwe; Pernicka, Manfred; Perriès, Stephane; Piaseki, C; Pierschel, Gerhard; Piotrzkowski, Krzysztof; Poettgens, Michael; Pooth, Oliver; Rouby, Xavier; Sabellek, Andreas; Schael, Stefan; Schirm, Norbert; Schleper, Peter; Schultz von Dratzig, Arndt; Siedling, Rolf; Simonis, Hans-Jürgen; Stahl, Achim; Steck, Pia; Steinbruck, G; Stoye, Markus; Strub, Roger; Tavernier, Stefaan; Teyssier, Daniel; Theel, Andreas; Trocmé, Benjamin; Udo, Fred; Van der Donckt, M; Van der Velde, C; Van Hove, Pierre; Vanlaer, Pascal; Van Lancker, Luc; Van Staa, Rolf; Vanzetto, Sylvain; Weber, Markus; Weiler, Thomas; Weseler, Siegfried; Wickens, John; Wittmer, Bruno; Wlochal, Michael; De Wolf, Eddi A; Zhukov, Valery; Zoeller, Marc Henning

    2009-01-01

    The silicon strip tracker of the CMS experiment has been completed and was inserted into the CMS detector in late 2007. The largest sub system of the tracker are its end caps, comprising two large end caps (TEC) each containing 3200 silicon strip modules. To ease construction, the end caps feature a modular design: groups of about 20 silicon modules are placed on sub-assemblies called petals and these self-contained elements are then mounted onto the TEC support structures. Each end cap consists of 144 such petals, which were built and fully qualified by several institutes across Europe. From

  10. Approach to the Electro-circuit Experiments of PLD & CPLD Units on TEC-2000 & TEC-2000A Didactical Computers%在TEC-2000及TEC-2000A教学计算机上实现PLD及CPLD电子线路实验方法

    Institute of Scientific and Technical Information of China (English)

    赵丽梅

    2005-01-01

    为了较好完成实验中有关重置简单可编程PLD器件GAL20V8芯片及复杂可编程CPLD器件MACH中的内容实验,探寻了在TEC-2000及TEC-2000A教学计算机上在不改变硬布线情况下进行PLD及CPLD电子线路实验的技术路线及具体实现方法.

  11. Reception Test of Petals for the End Cap TEC+ of the CMS Silicon Strip Tracker

    CERN Document Server

    Bremer, R; Klein, Katja; Schmitz, Stefan Antonius; Adler, Volker; Adolphi, Roman; Ageron, Michel; Agram, Jean-Laurent; Atz, Bernd; Barvich, Tobias; Baulieu, Guillaume; Beaumont, Willem; Beissel, Franz; Bergauer, Thomas; Berst, Jean-Daniel; Blüm, Peter; Bock, E; Bogelsbacher, F; de Boer, Wim; Bonnet, Jean-Luc; Bonnevaux, Alain; Boudoul, Gaelle; Bouhali, Othmane; Braunschweig, Wolfgang; Brom, Jean-Marie; Butz, Erik; Chabanat, Eric; Chabert, Eric Christian; Clerbaux, Barbara; Contardo, Didier; De Callatay, Bernard; Dehm, Philip; Delaere, Christophe; Della Negra, Rodolphe; Dewulf, Jean-Paul; D'Hondt, Jorgen; Didierjean, Francois; Dierlamm, Alexander; Dirkes, Guido; Dragicevic, Marko; Drouhin, Frédéric; Ernenwein, Jean-Pierre; Esser, Hans; Estre, Nicolas; Fahrer, Manuel; Fernández, J; Florins, Benoit; Flossdorf, Alexander; Flucke, Gero; Flügge, Günter; Fontaine, Jean-Charles; Freudenreich, Klaus; Frey, Martin; Friedl, Markus; Furgeri, Alexander; Giraud, Noël; Goerlach, Ulrich; Goorens, Robert; Graehling, Philippe; Grégoire, Ghislain; Gregoriev, E; Gross, Laurent; Hansel, S; Haroutunian, Roger; Hartmann, Frank; Heier, Stefan; Hermanns, Thomas; Heydhausen, Dirk; Heyninck, Jan; Hosselet, J; Hrubec, Josef; Jahn, Dieter; Juillot, Pierre; Kaminski, Jochen; Karpinski, Waclaw; Kaussen, Gordon; Keutgen, Thomas; Klanner, Robert; König, Stefan; Kosbow, M; Krammer, Manfred; Ledermann, Bernhard; Lemaître, Vincent; De Lentdecker, Gilles; Linn, Alexander; Lounis, Abdenour; Lübelsmeyer, Klaus; Lumb, Nicholas; Maazouzi, Chaker; Mahmoud, Tariq; Michotte, Daniel; Militaru, Otilia; Mirabito, Laurent; Müller, Thomas; Neukermans, Lionel; Ollivetto, C; Olzem, Jan; Ostapchuk, Andrey; Pandoulas, Demetrios; Pein, Uwe; Pernicka, Manfred; Perriès, Stephane; Piaseki, C; Pierschel, Gerhard; Piotrzkowski, Krzysztof; Poettgens, Michael; Pooth, Oliver; Rouby, Xavier; Sabellek, Andreas; Schael, Stefan; Schirm, Norbert; Schleper, Peter; Schultz von Dratzig, Arndt; Siedling, Rolf; Simonis, Hans-Jürgen; Stahl, Achim; Steck, Pia; Steinbruck, G; Stoye, Markus; Strub, Roger; Tavernier, Stefaan; Teyssier, Daniel; Theel, Andreas; Trocmé, Benjamin; Udo, Fred; Van der Donckt, M; Van der Velde, C; Van Hove, Pierre; Vanlaer, Pascal; Van Lancker, Luc; Van Staa, Rolf; Vanzetto, Sylvain; Weber, Markus; Weiler, Thomas; Weseler, Siegfried; Wickens, John; Wittmer, Bruno; Wlochal, Michael; De Wolf, Eddi A; Zhukov, Valery; Zoeller, Marc Henning

    2009-01-01

    The silicon strip tracker of the CMS experiment has been completed and was inserted into the CMS detector in late 2007. The largest sub system of the tracker are its end caps, comprising two large end caps (TEC) each containing 3200 silicon strip modules. To ease construction, the end caps feature a modular design: groups of about 20 silicon modules are placed on sub-assemblies called petals and these self-contained elements are then mounted onto the TEC support structures. Each end cap consists of 144 such petals, which were built and fully qualified by several institutes across Europe. From

  12. Analysis of Correlation between Ionospheric Spatial Gradients and Space Weather Intensity under Nominal Conditions for Ground-Based Augmentation Systems

    Science.gov (United States)

    Lee, J.

    2013-12-01

    Ground-Based Augmentation Systems (GBAS) support aircraft precision approach and landing by providing differential GPS corrections to aviation users. For GBAS applications, most of ionospheric errors are removed by applying the differential corrections. However, ionospheric correction errors may exist due to ionosphere spatial decorrelation between GBAS ground facility and users. Thus, the standard deviation of ionosphere spatial decorrelation (σvig) is estimated and included in the computation of error bounds on user position solution. The σvig of 4mm/km, derived for the Conterminous United States (CONUS), bounds one-sigma ionospheric spatial gradients under nominal conditions (including active, but not stormy condition) with an adequate safety margin [1]. The conservatism residing in the current σvig by fixing it to a constant value for all non-stormy conditions could be mitigated by subdividing ionospheric conditions into several classes and using different σvig for each class. This new concept, real-time σvig adaptation, will be possible if the level of ionospheric activity can be well classified based on space weather intensity. This paper studies correlation between the statistics of nominal ionospheric spatial gradients and space weather indices. The analysis was carried out using two sets of data collected from Continuous Operating Reference Station (CORS) Network; 9 consecutive (nominal and ionospherically active) days in 2004 and 19 consecutive (relatively 'quiet') days in 2010. Precise ionospheric delay estimates are obtained using the simplified truth processing method and vertical ionospheric gradients are computed using the well-known 'station pair method' [2]. The remaining biases which include carrier-phase leveling errors and Inter-frequency Bias (IFB) calibration errors are reduced by applying linear slip detection thresholds. The σvig was inflated to overbound the distribution of vertical ionospheric gradients with the required confidence

  13. Research on Earthquake Precursor in E-TEC: A Study on Land Surface Thermal Anomalies Using MODIS LST Product in Taiwan

    Science.gov (United States)

    Chang, W. Y.; Wu, M. C.

    2014-12-01

    Taiwan has been known as an excellent natural laboratory characterized by rapid active tectonic rate and high dense seismicity. The Eastern Taiwan Earthquake Research Center (E-TEC) is established on 2013/09/24 in National Dong Hwa University and collaborates with Central Weather Bureau (CWB), National Center for Research on Earthquake Engineering (NCREE), National Science and Technology Center for Disaster Reduction (NCDR), Institute of Earth Science of Academia Sinica (IES, AS) and other institutions (NCU, NTU, CCU) and aims to provide an integrated platform for researchers to conduct the new advances on earthquake precursors and early warning for seismic disaster prevention in the eastern Taiwan, as frequent temblors are most common in the East Taiwan rift valley. E-TEC intends to integrate the multi-disciplinary observations and is equipped with stations to monitor a wide array of factors of quake precursors, including seismicity, GPS, strain-meter, ground water, geochemistry, gravity, electromagnetic, ionospheric density, thermal infrared remote sensing, gamma radiation etc, and will maximize the value of the data for researches with the range of monitoring equipment that enable to predict where and when the next devastated earthquake will strike Taiwan and develop reliable earthquake prediction models. A preliminary study on earthquake precursor using monthly Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) data before 2013/03/27 Mw6.2 Nantou earthquake in Taiwan is presented. Using the statistical analysis, the result shows the peak of the anomalous LST that exceeds a standard deviation of LST appeared on 2013/03/09 and became less or none anomalies observed on 2013/03/16 before the main-shock, which is in consist with the phenomenon observed by other researchers. This preliminary experimental result shows that the thermal anomalies reveal the possibility to associate surface thermal phenomena before the strong earthquakes.

  14. VizieR Online Data Catalog: AzTEC/ASTE 1.1mm survey of SSA22 (Umehata+, 2014)

    Science.gov (United States)

    Umehata, H.; Tamura, Y.; Kohno, K.; Hatsukade, B.; Scott, K. S.; Kubo, M.; Yamada, T.; Ivison, R. J.; Cybulski, R.; Aretxaga, I.; Austermann, J.; Hughes, D. H.; Ezawa, H.; Hayashino, T.; Ikarashi, S.; Iono, D.; Kawabe, R.; Matsuda, Y.; Matsuo, H.; Nakanishi, K.; Oshima, T.; Perera, T.; Takata, T.; Wilson, G. W.; Yun, M. S.

    2015-01-01

    We used the AzTEC camera operating at 1.1mm mounted on the ASTE 10-m submillimetre telescope located at Pampa la Bola, near Cerro Chajnantor in northern Chile. All of the AzTEC/ASTE observations of SSA22 were carried out at night during 2007 August-September and 2008 August-September. (4 data files).

  15. Ground-based follow-up in relation to Kepler Asteroseismic Investigation

    CERN Document Server

    Uytterhoeven, K; Bruntt, H; De Cat, P; Frandsen, S; Gutierrez-Soto, J; Kiss, L; Kurtz, D W; Marconi, M; Molenda-Zakowicz, J; Ostensen, R; Randall, S; Southworth, J; Szabo, R

    2010-01-01

    The Kepler space mission, successfully launched in March 2009, is providing continuous, high-precision photometry of thousands of stars simultaneously. The uninterrupted time-series of stars of all known pulsation types are a precious source for asteroseismic studies. The Kepler data do not provide information on the physical parameters, such as effective temperature, surface gravity, metallicity, and vsini, which are crucial for successful asteroseismic modelling. Additional ground-based time-series data are needed to characterize mode parameters in several types of pulsating stars. Therefore, ground-based multi-colour photometry and mid/high-resolution spectroscopy are needed to complement the space data. We present ground-based activities within KASC on selected asteroseismic Kepler targets of several pulsation types. (Based on observations made with the Isaac Newton Telescope, William Herschel Telescope, Nordic Optical Telescope, Telescopio Nazionale Galileo, Mercator Telescope (La Palma, Spain), and IAC-...

  16. BigBOSS: The Ground-Based Stage IV BAO Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, David; Bebek, Chris; Heetderks, Henry; Ho, Shirley; Lampton, Michael; Levi, Michael; Mostek, Nick; Padmanabhan, Nikhil; Perlmutter, Saul; Roe, Natalie; Sholl, Michael; Smoot, George; White, Martin; Dey, Arjun; Abraham, Tony; Jannuzi, Buell; Joyce, Dick; Liang, Ming; Merrill, Mike; Olsen, Knut; Salim, Samir

    2009-04-01

    The BigBOSS experiment is a proposed DOE-NSF Stage IV ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with an all-sky galaxy redshift survey. The project is designed to unlock the mystery of dark energy using existing ground-based facilities operated by NOAO. A new 4000-fiber R=5000 spectrograph covering a 3-degree diameter field will measure BAO and redshift space distortions in the distribution of galaxies and hydrogen gas spanning redshifts from 0.2< z< 3.5. The Dark Energy Task Force figure of merit (DETF FoM) for this experiment is expected to be equal to that of a JDEM mission for BAO with the lower risk and cost typical of a ground-based experiment.

  17. Comparing Dawn, Hubble Space Telescope, and Ground-Based Interpretations of (4) Vesta

    CERN Document Server

    Reddy, Vishnu; Corre, Lucille Le; Scully, Jennifer E C; Gaskell, Robert; Russell, Christopher T; Park, Ryan S; Nathues, Andreas; Raymond, Carol; Gaffey, Michael J; Sierks, Holger; Becker, Kris J; McFadden, Lucy A

    2013-01-01

    Observations of asteroid 4 Vesta by NASA's Dawn spacecraft are interesting because its surface has the largest range of albedo, color and composition of any other asteroid visited by spacecraft to date. These hemispherical and rotational variations in surface brightness and composition have been attributed to impact processes since Vesta's formation. Prior to Dawn's arrival at Vesta, its surface properties were the focus of intense telescopic investigations for nearly a hundred years. Ground-based photometric and spectroscopic observations first revealed these variations followed later by those using Hubble Space Telescope. Here we compare interpretations of Vesta's rotation period, pole, albedo, topographic, color, and compositional properties from ground-based telescopes and HST with those from Dawn. Rotational spectral variations observed from ground-based studies are also consistent with those observed by Dawn. While the interpretation of some of these features was tenuous from past data, the interpretati...

  18. Ka-band bistatic ground-based SAR using noise signals

    Science.gov (United States)

    Lukin, K.; Mogyla, A.; Vyplavin, P.; Palamarchuk, V.; Zemlyaniy, O.; Tarasenko, V.; Zaets, N.; Skretsanov, V.; Shubniy, A.; Glamazdin, V.; Natarov, M.; Nechayev, O.

    2008-01-01

    Currently, one of the actual problems is remote monitoring of technical state of large objects. Different methods can be used for that purpose. The most promising of them relies on application of ground based synthetic aperture radars (SAR) and differential interferometry. We have designed and tested Ground Based Noise Waveform SAR based on noise radar technology [1] and synthetic aperture antennas [2]. It enabled to build an instrument for precise all-weather monitoring of large objects in real-time. We describe main performance of ground-based interferometric SAR which uses continuous Ka-band noise waveform as a probe signal. Besides, results of laboratory trials and evaluation of its main performance are presented as well.

  19. Phylogeny of Tec family kinases identification of a premetazoan origin of Btk, Bmx, Itk, Tec, Txk, and the Btk regulator SH3BP5.

    Science.gov (United States)

    Ortutay, Csaba; Nore, Beston F; Vihinen, Mauno; Smith, C I Edvard

    2008-01-01

    It is generally considered mammals and birds have five Tec family kinases (TFKs): Btk, Bmx (also known as Etk), Itk, Tec, and Txk (also known as Rlk). Here, we discuss the domains and their functions and regulation in TFKs. Over the last few years, a large number of genomes from various phyla have been sequenced making it possible to study evolutionary relationships at the molecular and sequence level. Using bioinformatics tools, we for the first time demonstrate that a TFK ancestor exists in the unicellular choanoflagellate Monosiga brevicollis, which is the closest known relative to metazoans with a sequenced genome. The analysis of the genomes for sponges, insects, hagfish, and frogs suggests that these species encode a single TFK. The insect form has a divergent and unique N-terminal region. Duplications generating the five members took place prior to the emergence of vertebrates. Fishes have two or three forms and the platypus, Ornithorhynchus anatinus, has four (lacks Txk). Thus, not all mammals have all five TFKs. The single identified TFK in frogs is an ortholog of Tec. Bmx seems to be unique to mammals and birds. SH3BP5 is a negative regulator of Btk. It is conserved in choanoflagellates and interestingly exists also in nematodes, which do not express TFKs, suggesting a broader function in addition to Btk regulation. The related SH3BP5-like protein is not found in Nematodes.

  20. Space-Borne and Ground-Based InSAR Data Integration: The Åknes Test Site

    Directory of Open Access Journals (Sweden)

    Federica Bardi

    2016-03-01

    Full Text Available This work concerns a proposal of the integration of InSAR (Interferometric Synthetic Aperture Radar data acquired by ground-based (GB and satellite platforms. The selected test site is the Åknes rockslide, which affects the western Norwegian coast. The availability of GB-InSAR and satellite InSAR data and the accessibility of a wide literature make the landslide suitable for testing the proposed procedure. The first step consists of the organization of a geodatabase, performed in the GIS environment, containing all of the available data. The second step concerns the analysis of satellite and GB-InSAR data, separately. Two datasets, acquired by RADARSAT-2 (related to a period between October 2008 and August 2013 and by a combination of TerraSAR-X and TanDEM-X (acquired between July 2010 and October 2012, both of them in ascending orbit, processed applying SBAS (Small BAseline Subset method, are available. GB-InSAR data related to five different campaigns of measurements, referred to the summer seasons of 2006, 2008, 2009, 2010 and 2012, are available, as well. The third step relies on data integration, performed firstly from a qualitative point of view and later from a semi-quantitative point of view. The results of the proposed procedure have been validated by comparing them to GPS (Global Positioning System data. The proposed procedure allowed us to better define landslide sectors in terms of different ranges of displacements. From a qualitative point of view, stable and unstable areas have been distinguished. In the sector concerning movement, two different sectors have been defined thanks to the results of the semi-quantitative integration step: the first sector, concerning displacement values higher than 10 mm, and the 2nd sector, where the displacements did not exceed a 10-mm value of displacement in the analyzed period.

  1. Ground-based multispectral measurements for airborne data verification in non-operating open pit mine "Kremikovtsi"

    Science.gov (United States)

    Borisova, Denitsa; Nikolov, Hristo; Petkov, Doyno

    2013-10-01

    The impact of mining industry and metal production on the environment is presented all over the world. In our research we set focus on the impact of already non-operating ferrous "Kremikovtsi"open pit mine and related waste dumps and tailings which we consider to be the major factor responsible for pollution of one densely populated region in Bulgaria. The approach adopted is based on correct estimation of the distribution of the iron oxides inside open pit mines and the neighboring regions those considered in this case to be the key issue for the ecological state assessment of soils, vegetation and water. For this study the foremost source of data are those of airborne origin and those combined with ground-based in-situ and laboratory acquired data were used for verification of the environmental variables and thus in process of assessment of the present environmental status influenced by previous mining activities. The percentage of iron content was selected as main indicator for presence of metal pollution since it could be reliably identified by multispectral data used in this study and also because the iron compounds are widely spread in the most of the minerals, rocks and soils. In our research the number of samples from every source (air, field, lab) was taken in the way to be statistically sound and confident. In order to establish relationship between the degree of pollution of the soil and mulspectral data 40 soil samples were collected during a field campaign in the study area together with GPS measurements for two types of laboratory measurements: the first one, chemical and mineralogical analysis and the second one, non-destructive spectroscopy. In this work for environmental variables verification over large areas mulspectral satellite data from Landsat instruments TM/ETM+ and from ALI/OLI (Operational Land Imager) were used. Ground-based (laboratory and in-situ) spectrometric measurements were performed using the designed and constructed in Remote

  2. GPS phase scintillation at high latitudes during the geomagnetic storm of 17-18 March 2015

    Science.gov (United States)

    Prikryl, P.; Ghoddousi-Fard, R.; Weygand, J. M.; Viljanen, A.; Connors, M.; Danskin, D. W.; Jayachandran, P. T.; Jacobsen, K. S.; Andalsvik, Y. L.; Thomas, E. G.; Ruohoniemi, J. M.; Durgonics, T.; Oksavik, K.; Zhang, Y.; Spanswick, E.; Aquino, M.; Sreeja, V.

    2016-10-01

    The geomagnetic storm of 17-18 March 2015 was caused by the impacts of a coronal mass ejection and a high-speed plasma stream from a coronal hole. The high-latitude ionosphere dynamics is studied using arrays of ground-based instruments including GPS receivers, HF radars, ionosondes, riometers, and magnetometers. The phase scintillation index is computed for signals sampled at a rate of up to 100 Hz by specialized GPS scintillation receivers supplemented by the phase scintillation proxy index obtained from geodetic-quality GPS data sampled at 1 Hz. In the context of solar wind coupling to the magnetosphere-ionosphere system, it is shown that GPS phase scintillation is primarily enhanced in the cusp, the tongue of ionization that is broken into patches drawn into the polar cap from the dayside storm-enhanced plasma density, and in the auroral oval. In this paper we examine the relation between the scintillation and auroral electrojet currents observed by arrays of ground-based magnetometers as well as energetic particle precipitation observed by the DMSP satellites. Equivalent ionospheric currents are obtained from ground magnetometer data using the spherical elementary currents systems technique that has been applied over the ground magnetometer networks in North America and North Europe. The GPS phase scintillation is mapped to the poleward side of strong westward electrojet and to the edge of the eastward electrojet region. Also, the scintillation was generally collocated with fluxes of energetic electron precipitation observed by DMSP satellites with the exception of a period of pulsating aurora when only very weak currents were observed.

  3. Scintillation-Hardened GPS Receiver

    Science.gov (United States)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  4. Scintillation-Hardened GPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A Communications, Navigation, and Networking reConfigurable Testbed (CoNNeCT) experiment is proposed to improve the performance of GPS during geomagnetic storms....

  5. First ground-based FTIR-observations of methane in the tropics

    Directory of Open Access Journals (Sweden)

    A. K. Petersen

    2010-02-01

    Full Text Available Total column concentrations and volume mixing ratio profiles of methane have been retrieved from ground-based solar absorption FTIR spectra in the near-infrared recorded in Paramaribo (Suriname. The methane FTIR observations are compared with TM5 model simulations and satellite observations from SCIAMACHY, and represent the first validation of SCIAMACHY retrievals in the tropics using ground-based remote sensing techniques. Apart from local biomass burning features, our methane FTIR observations agree well with the SCIAMACHY retrievals and TM5 model simulations.

  6. Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters

    OpenAIRE

    İnan, Umran Savaş; Graf, K. L.; Spasojevic, M.; Marshall, R. A.; Lehtinen, N. G.; Foust, F. R.

    2013-01-01

    JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 7783–7797, doi:10.1002/2013JA019337, 2013 Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters K. L. Graf,1 M. Spasojevic,1 R. A. Marshall,2 N. G. Lehtinen,1 F. R. Foust,1 and U. S. Inan1,3 Received 16 August 2013; revised 9 October 2013; accepted 11 November 2013; published 3 December 2013. [1] The effects of ground-based very low frequency (VLF) transmitters on the lower ionospher...

  7. Status of advanced ground-based laser interferometers for gravitational-wave detection

    CERN Document Server

    Dooley, Katherine L; Dwyer, Sheila; Puppo, Paola

    2014-01-01

    Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years' worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO600 and KAGRA.

  8. Asteroseismology of solar-type stars with Kepler: III. Ground-based data

    DEFF Research Database (Denmark)

    Karoff, Christoffer; Molenda-Żakowicz , J.

    2010-01-01

    We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than a thousand objects which are the subject of an intensive study by the Kepler Asteroseis......We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than a thousand objects which are the subject of an intensive study by the Kepler...

  9. Estimation of solar irradiance using ground-based whole sky imagers

    CERN Document Server

    Dev, Soumyabrata; Lee, Yee Hui; Winkler, Stefan

    2016-01-01

    Ground-based whole sky imagers (WSIs) can provide localized images of the sky of high temporal and spatial resolution, which permits fine-grained cloud observation. In this paper, we show how images taken by WSIs can be used to estimate solar radiation. Sky cameras are useful here because they provide additional information about cloud movement and coverage, which are otherwise not available from weather station data. Our setup includes ground-based weather stations at the same location as the imagers. We use their measurements to validate our methods.

  10. Continuous professional development for GPs

    DEFF Research Database (Denmark)

    Kjaer, N K; Steenstrup, A P; Pedersen, L B

    2014-01-01

    randomly chosen Danish GPs. RESULTS: Focus groups: CPD activities are chosen based on personal needs analysis, and in order to be professionally updated, to meet engaged colleagues and to prevent burnout. GPs also attend CPD to assess their own pre-existing level of competence. CPD activities need...... by topics strengthening their professional capacity and preventing burnout. There would seem to be no need for a mandatory system....

  11. Global Positioning Systems Directorate: GPS Update

    Science.gov (United States)

    2015-04-29

    Council Maintenance/Security Spectrum 39 Satellites /31 Set Healthy Baseline Constellation : 24 Satellites • All Level l and Level II...Department of Transportation • Federal Aviation Administration Satellite Block GPS IIA GPS IIR GPS IIR-M GPS IIF Constellation Department of...segment - India- IRNSS UNCLASSIFIED/APPROVED FOR PUBLIC RELEASE 3 UNCLASSIFIED/APPROVED FOR PUBLIC RELEASE GPS Constellation Status SPACE AND

  12. GPS detection and monitoring of underground nuclear explosions

    Science.gov (United States)

    Park, Jihye; Grejner-Brzezinska, Dorota; von Frese, Ralph; Morton, Yu; Gaya-Pique, Luis

    2013-04-01

    Previous studies by Park et al. (2011) revealed that an underground nuclear explosion (UNE) induces the acoustic-gravity waves, which disturb the ionosphere and generate the traveling ionospheric disturbance (TID). GPS technique allows for the ionospheric disturbance observation with high accuracy, which, in turn, enables detection of the TID induced by the UNE. This study suggests the detection and verification method of the TID using GPS observations. TID waves can be identified from the continuous data span of the total electron content (TEC) along the ray path between the GPS satellites and the observing stations. Since the TID is a high frequency and low amplitude signal, it should be properly isolated from the raw TEC observation. In this study, we applied the numerical derivative method, referred to as the numerical third order horizontal 3-point derivative method. The detected TID-like signals can be verified by its array signature under the assumption that the TID induced from a point source tends to propagate with the constant speed. Moreover, the location of the point source can be computed using the array pattern of TID observations from multiple GPS stations. In this study, two UNEs conducted by the U.S. in 1992 and two UNEs conducted by North Korea in 2006 and 2009 were investigated. The propagation speed of the U.S. UNEs was about 573 m/s and 740 m/s, respectively, while the recent North Korean UNEs propagation speed was less than 300 m/s. This result can be explained by the explosion yields and the depth of the UNEs: the depth of the US UNEs were about 0.3 km with the explosion yield of up to 20 kiloton, while the North Korean UNEs were at about 1 km depth with the yield of less than a few kilotons. In addition, we observed that the TID waves from these four UNE events were highly correlative, and distinguished from waveforms due to other types of events, such as an earthquake. As a case study, we selected the recent Tohoku earthquake of 2011, and

  13. V-TECS Criterion-Referenced Test Item Bank for Radiologic Technology Occupations.

    Science.gov (United States)

    Reneau, Fred; And Others

    This Vocational-Technical Education Consortium of States (V-TECS) criterion-referenced test item bank provides 696 multiple-choice items and 33 matching items for radiologic technology occupations. These job titles are included: radiologic technologist, chief; radiologic technologist; nuclear medicine technologist; radiation therapy technologist;…

  14. Multiskilled Health Technician: Developing a V-TECS Curriculum Guide. Final Report.

    Science.gov (United States)

    Kisner, Mary J.; Marks, Renee

    A Vocational-Technical Education Consortium of States (V-TECS) curriculum was developed for a new job title, the "multiskilled health technician." A traditional task analysis method was not feasible, since the occupation does not exist. Instead, the project defined the occupation and developed the duties and tasks as a hybrid of many…

  15. En el TEC Escuela de Biología inaugura laboratorio de biocontroladores

    OpenAIRE

    Redacción, Redacción

    2013-01-01

    Un laboratorio de biocontroladores (parasitoides y depredadores) inauguró el Centro de Investigación en Biotecnología (CIB) de la Escuela de Biología del Instituto Tecnológico de Costa Rica (TEC).

  16. Anomalous TEC variations associated with the powerful Tohoku earthquake of 11 March 2011

    Directory of Open Access Journals (Sweden)

    M. Akhoondzadeh

    2012-05-01

    Full Text Available On 11 March 2011 at 14:46:23 LT, the 4th largest earthquake ever recorded with a magnitude of 9.0 occurred near the northeast coast of Honshu in Japan (38.322° N, 142.369° E, Focal depth 29.0 km. In order to acknowledge the capabilities of Total Electron Content (TEC ionospheric precursor, in this study four methods including mean, median, wavelet transform, and Kalman filter have been applied to detect anomalous TEC variations concerning the Tohoku earthquake. The duration of the TEC time series dataset is 49 days at a time resolution of 2 h. All four methods detected a considerable number of anomalous occurrences during 1 to 10 days prior to the earthquake in a period of high geomagnetic activities. In this study, geomagnetic indices (i.e. Dst, Kp, Ap and F10.7 were used to distinguish pre-earthquake anomalies from the other anomalies related to the geomagnetic and solar activities. A good agreement in results was found between the different applied anomaly detection methods on TEC data.

  17. 78 FR 64207 - Application To Export Electric Energy; TEC Energy Inc.

    Science.gov (United States)

    2013-10-28

    ... Application To Export Electric Energy; TEC Energy Inc. AGENCY: Office of Electricity Delivery and Energy... transmit electric energy from the United States to Canada pursuant to section 202(e) of the Federal Power... transmit electric energy from the United States to Canada for five years as a power marketer using...

  18. Ground-Based VIS/NIR Reflectance Spectra of 25143 Itokawa: What Hayabusa will See and How Ground-Based Data can Augment Analyses

    Science.gov (United States)

    Vilas, Faith; Abell, P. A.; Jarvis, K. S.

    2004-01-01

    Planning for the arrival of the Hayabusa spacecraft at asteroid 25143 Itokawa includes consideration of the expected spectral information to be obtained using the AMICA and NIRS instruments. The rotationally-resolved spatial coverage the asteroid we have obtained with ground-based telescopic spectrophotometry in the visible and near-infrared can be utilized here to address expected spacecraft data. We use spectrophotometry to simulate the types of data that Hayabusa will receive with the NIRS and AMICA instruments, and will demonstrate them here. The NIRS will cover a wavelength range from 0.85 m, and have a dispersion per element of 250 Angstroms. Thus, we are limited in coverage of the 1.0 micrometer and 2.0 micrometer mafic silicate absorption features. The ground-based reflectance spectra of Itokawa show a large component of olivine in its surface material, and the 2.0 micrometer feature is shallow. Determining the olivine to pyroxene abundance ratio is critically dependent on the attributes of the 1.0- and 2.0 micrometer features. With a cut-off near 2,1 micrometer the longer edge of the 2.0- feature will not be obtained by NIRS. Reflectance spectra obtained using ground-based telescopes can be used to determine the regional composition around space-based spectral observations, and possibly augment the longer wavelength spectral attributes. Similarly, the shorter wavelength end of the 1.0 micrometer absorption feature will be partially lost to the NIRS. The AMICA filters mimic the ECAS filters, and have wavelength coverage overlapping with the NIRS spectral range. We demonstrate how merging photometry from AMICA will extend the spectral coverage of the NIRS. Lessons learned from earlier spacecraft to asteroids should be considered.

  19. Applying the Water Vapor Radiometer to Verify the Precipitable Water Vapor Measured by GPS

    Directory of Open Access Journals (Sweden)

    Ta-Kang Yeh

    2014-01-01

    Full Text Available Taiwan is located at the land-sea interface in a subtropical region. Because the climate is warm and moist year round, there is a large and highly variable amount of water vapor in the atmosphere. In this study, we calculated the Zenith Wet Delay (ZWD of the troposphere using the ground-based Global Positioning System (GPS. The ZWD measured by two Water Vapor Radiometers (WVRs was then used to verify the ZWD that had been calculated using GPS. We also analyzed the correlation between the ZWD and the precipitation data of these two types of station. Moreover, we used the observational data from 14 GPS and rainfall stations to evaluate three cases. The offset between the GPS-ZWD and the WVR-ZWD ranged from 1.31 to 2.57 cm. The correlation coefficient ranged from 0.89 to 0.93. The results calculated from GPS and those measured using the WVR were very similar. Moreover, when there was no rain, light rain, moderate rain, or heavy rain, the flatland station ZWD was 0.31, 0.36, 0.38, or 0.40 m, respectively. The mountain station ZWD exhibited the same trend. Therefore, these results have demonstrated that the potential and strength of precipitation in a region can be estimated according to its ZWD values. Now that the precision of GPS-ZWD has been confirmed, this method can eventually be expanded to the more than 400 GPS stations in Taiwan and its surrounding islands. The near real-time ZWD data with improved spatial and temporal resolution can be provided to the city and countryside weather-forecasting system that is currently under development. Such an exchange would fundamentally improve the resources used to generate weather forecasts.

  20. Short-term estimation of GNSS TEC using a neural network model in Brazil

    Science.gov (United States)

    Ferreira, Arthur Amaral; Borges, Renato Alves; Paparini, Claudia; Ciraolo, Luigi; Radicella, Sandro M.

    2017-10-01

    This work presents a novel Neural Network (NN) model to estimate Total Electron Content (TEC) from Global Navigation Satellite Systems (GNSS) measurements in three distinct sectors in Brazil. The purpose of this work is to start the investigations on the development of a regional model that can be used to determine the vertical TEC over Brazil, aiming future applications on a near real-time frame estimations and short-term forecasting. The NN is used to estimate the GNSS TEC values at void locations, where no dual-frequency GNSS receiver that may be used as a source of data to GNSS TEC estimation is available. This approach is particularly useful for GNSS single-frequency users that rely on corrections of ionospheric range errors by TEC models. GNSS data from the first GLONASS network for research and development (GLONASS R&D network) installed in Latin America, and from the Brazilian Network for Continuous Monitoring of the GNSS (RMBC) were used on TEC calibration. The input parameters of the NN model are based on features known to influence TEC values, such as geographic location of the GNSS receiver, magnetic activity, seasonal and diurnal variations, and solar activity. Data from two ten-days periods (from DoY 154 to 163 and from 282 to 291) are used to train the network. Three distinct analyses have been carried out in order to assess time-varying and spatial performance of the model. At the spatial performance analysis, for each region, a set of stations is chosen to provide training data to the NN, and after the training procedure, the NN is used to estimate vTEC behavior for the test station which data were not presented to the NN in training process. An analysis is done by comparing, for each testing station, the estimated NN vTEC delivered by the NN and reference calibrated vTEC. Also, as a second analysis, the network ability to forecast one day after the time interval (DoY 292) based on information of the second period of investigation is also assessed

  1. On reconciling ground-based with spaceborne normalized radar cross section measurements

    DEFF Research Database (Denmark)

    Baumgartner, Francois; Munk, Jens; Jezek, K C

    2002-01-01

    This study examines differences in the normalized radar cross section, derived from ground-based versus spaceborne radar data. A simple homogeneous half-space model, indicates that agreement between the two improves as 1) the distance from the scatterer is increased; and/or 2) the extinction...

  2. Precision simulation of ground-based lensing data using observations from space

    CERN Document Server

    Mandelbaum, Rachel; Leauthaud, Alexie; Massey, Richard J; Rhodes, Jason

    2011-01-01

    Current and upcoming wide-field, ground-based, broad-band imaging surveys promise to address a wide range of outstanding problems in galaxy formation and cosmology. Several such uses of ground-based data, especially weak gravitational lensing, require highly precise measurements of galaxy image statistics with careful correction for the effects of the point-spread function (PSF). In this paper, we introduce the SHERA (SHEar Reconvolution Analysis) software to simulate ground-based imaging data with realistic galaxy morphologies and observing conditions, starting from space-based data (from COSMOS, the Cosmological Evolution Survey) and accounting for the effects of the space-based PSF. This code simulates ground-based data, optionally with a weak lensing shear applied, in a model-independent way using a general Fourier space formalism. The utility of this pipeline is that it allows for a precise, realistic assessment of systematic errors due to the method of data processing, for example in extracting weak len...

  3. Analysis of the substorm trigger phase using multiple ground-based instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Kauristie, K.; Pulkkinen, T.I.; Pellinen, R.J. [Finnish Meteorological Institute, Helsinki (Finland)] [and others

    1995-08-01

    The authors discuss in detail the observation of an event of auroral activity fading during the trigger, or growth phase of a magnetic storm. This event was observed by all-sky cameras, EISCAT radar and magnetometers, riometers, and pulsation magnetometers, from ground based stations in Finland and Scandanavia. Based on their detailed analysis, they present a possible cause for the observed fading.

  4. Simulation of the imaging quality of ground-based telescopes affected by atmospheric disturbances

    Science.gov (United States)

    Ren, Yubin; Kou, Songfeng; Gu, Bozhong

    2014-08-01

    Ground-based telescope imaging model is developed in this paper, the relationship between the atmospheric disturbances and the ground-based telescope image quality is studied. Simulation of the wave-front distortions caused by atmospheric turbulences has long been an important method in the study of the propagation of light through the atmosphere. The phase of the starlight wave-front is changed over time, but in an appropriate short exposure time, the atmospheric disturbances can be considered as "frozen". In accordance with Kolmogorov turbulence theory, simulating atmospheric disturbances of image model based on the phase screen distorted by atmospheric turbulences is achieved by the fast Fourier transform (FFT). Geiger mode avalanche photodiode array (APD arrays) model is used for atmospheric wave-front detection, the image is achieved by inversion method of photon counting after the target starlight goes through phase screens and ground-based telescopes. Ground-based telescope imaging model is established in this paper can accurately achieve the relationship between the quality of telescope imaging and monolayer or multilayer atmosphere disturbances, and it is great significance for the wave-front detection and optical correction in a Multi-conjugate Adaptive Optics system (MCAO).

  5. Ground-based LIDAR: a novel approach to quantify fine-scale fuelbed characteristics

    Science.gov (United States)

    E.L. Loudermilk; J.K. Hiers; J.J. O’Brien; R.J. Mitchell; A. Singhania; J.C. Fernandez; W.P. Cropper; K.C. Slatton

    2009-01-01

    Ground-based LIDAR (also known as laser ranging) is a novel technique that may precisely quantify fuelbed characteristics important in determining fire behavior. We measured fuel properties within a south-eastern US longleaf pine woodland at the individual plant and fuelbed scale. Data were collected using a mobile terrestrial LIDAR unit at sub-cm scale for individual...

  6. Use of neural networks in ground-based aerosol retrievals from multi-angle spectropolarimetric observations

    NARCIS (Netherlands)

    Di Noia, A.; Hasekamp, O.P.; Harten, G. van; Rietjens, J.H.H.; Smit, J.M.; Snik, F.; Henzing, J.S.; Boer, J. de; Keller, C.U.; Volten, H.

    2015-01-01

    In this paper, the use of a neural network algorithm for the retrieval of the aerosol properties from ground-based spectropolarimetric measurements is discussed. The neural network is able to retrieve the aerosol properties with an accuracy that is almost comparable to that of an iterative retrieval

  7. Retrieval of liquid water cloud properties from ground-based remote sensing observations

    NARCIS (Netherlands)

    Knist, C.L.

    2014-01-01

    Accurate ground-based remotely sensed microphysical and optical properties of liquid water clouds are essential references to validate satellite-observed cloud properties and to improve cloud parameterizations in weather and climate models. This requires the evaluation of algorithms for retrieval of

  8. Ground-based remote sensing scheme for monitoring aerosol–cloud interactions (discussion)

    NARCIS (Netherlands)

    Sarna, K.; Russchenberg, H.W.J.

    2015-01-01

    A method for continuous observation of aerosol–cloud interactions with ground-based remote sensing instruments is presented. The main goal of this method is to enable the monitoring of cloud microphysical changes due to the changing aerosol concentration. We use high resolution measurements from lid

  9. Ground-based remote sensing scheme for monitoring aerosol-cloud interactions

    NARCIS (Netherlands)

    Sarna, K.; Russchenberg, H.W.J.

    2016-01-01

    A new method for continuous observation of aerosol–cloud interactions with ground-based remote sensing instruments is presented. The main goal of this method is to enable the monitoring of the change of the cloud droplet size due to the change in the aerosol concentration. We use high-resolution mea

  10. Low Power Ground-Based Laser Illumination for Electric Propulsion Applications

    Science.gov (United States)

    Lapointe, Michael R.; Oleson, Steven R.

    1994-01-01

    A preliminary evaluation of low power, ground-based laser powered electric propulsion systems is presented. A review of available and near-term laser, photovoltaic, and adaptive optic systems indicates that approximately 5-kW of ground-based laser power can be delivered at an equivalent one-sun intensity to an orbit of approximately 2000 km. Laser illumination at the proper wavelength can double photovoltaic array conversion efficiencies compared to efficiencies obtained with solar illumination at the same intensity, allowing a reduction in array mass. The reduced array mass allows extra propellant to be carried with no penalty in total spacecraft mass. The extra propellant mass can extend the satellite life in orbit, allowing additional revenue to be generated. A trade study using realistic cost estimates and conservative ground station viewing capability was performed to estimate the number of communication satellites which must be illuminated to make a proliferated system of laser ground stations economically attractive. The required number of satellites is typically below that of proposed communication satellite constellations, indicating that low power ground-based laser beaming may be commercially viable. However, near-term advances in low specific mass solar arrays and high energy density batteries for LEO applications would render the ground-based laser system impracticable.

  11. Asteroseismology of solar-type stars with Kepler: III. Ground-based data

    DEFF Research Database (Denmark)

    Karoff, Christoffer; Molenda-Żakowicz , J.

    2010-01-01

    We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than a thousand objects which are the subject of an intensive study by the Kepler Asteroseis...

  12. A Fast Method for Embattling Optimization of Ground-Based Radar Surveillance Network

    Science.gov (United States)

    Jiang, H.; Cheng, H.; Zhang, Y.; Liu, J.

    A growing number of space activities have created an orbital debris environment that poses increasing impact risks to existing space systems and human space flight. For the safety of in-orbit spacecraft, a lot of observation facilities are needed to catalog space objects, especially in low earth orbit. Surveillance of Low earth orbit objects are mainly rely on ground-based radar, due to the ability limitation of exist radar facilities, a large number of ground-based radar need to build in the next few years in order to meet the current space surveillance demands. How to optimize the embattling of ground-based radar surveillance network is a problem to need to be solved. The traditional method for embattling optimization of ground-based radar surveillance network is mainly through to the detection simulation of all possible stations with cataloged data, and makes a comprehensive comparative analysis of various simulation results with the combinational method, and then selects an optimal result as station layout scheme. This method is time consuming for single simulation and high computational complexity for the combinational analysis, when the number of stations increases, the complexity of optimization problem will be increased exponentially, and cannot be solved with traditional method. There is no better way to solve this problem till now. In this paper, target detection procedure was simplified. Firstly, the space coverage of ground-based radar was simplified, a space coverage projection model of radar facilities in different orbit altitudes was built; then a simplified objects cross the radar coverage model was established according to the characteristics of space objects orbit motion; after two steps simplification, the computational complexity of the target detection was greatly simplified, and simulation results shown the correctness of the simplified results. In addition, the detection areas of ground-based radar network can be easily computed with the

  13. Ground-Based Lidar Measurements During the CALIPSO and Twilight Zone (CATZ) Campaign

    Science.gov (United States)

    Berkoff, Timothy; Qian, Li; Kleidman, Richard; Stewart, Sebastian; Welton, Ellsworth; Li, Zhu; Holbem, Brent

    2008-01-01

    The CALIPSO and Twilight Zone (CATZ) field campaign was carried out between June 26th and August 29th of 2007 in the multi-state Maryland-Virginia-Pennsylvania region of the U.S. to study aerosol properties and cloud-aerosol interactions during overpasses of the CALIPSO satellite. Field work was conducted on selected days when CALIPSO ground tracks occurred in the region. Ground-based measurements included data from multiple Cimel sunphotometers that were placed at intervals along a segment of the CALIPSO ground-track. These measurements provided sky radiance and AOD measurements to enable joints inversions and comparisons with CALIPSO retrievals. As part of this activity, four ground-based lidars provided backscatter measurements (at 523 nm) in the region. Lidars at University of Maryland Baltimore County (Catonsville, MD) and Goddard Space Flight Center (Greenbelt, MD) provided continuous data during the campaign, while two micro-pulse lidar (MPL) systems were temporarily stationed at various field locations directly on CALIPSO ground-tracks. As a result, thirteen on-track ground-based lidar observations were obtained from eight different locations in the region. In some cases, nighttime CALIPSO coincident measurements were also obtained. In most studies reported to date, ground-based lidar validation efforts for CALIPSO rely on systems that are at fixed locations some distance away from the satellite ground-track. The CATZ ground-based lidar data provide an opportunity to examine vertical structure properties of aerosols and clouds both on and off-track simultaneously during a CALIPSO overpass. A table of available ground-based lidar measurements during this campaign will be presented, along with example backscatter imagery for a number of coincident cases with CALIPSO. Results indicate that even for a ground-based measurements directly on-track, comparisons can still pose a challenge due to the differing spatio-temporal properties of the ground and satellite

  14. GPS satellite and receiver instrumental biases estimation using least squares method for accurate ionosphere modelling

    Indian Academy of Sciences (India)

    G Sasibhushana Rao

    2007-10-01

    The positional accuracy of the Global Positioning System (GPS)is limited due to several error sources.The major error is ionosphere.By augmenting the GPS,the Category I (CAT I)Precision Approach (PA)requirements can be achieved.The Space-Based Augmentation System (SBAS)in India is known as GPS Aided Geo Augmented Navigation (GAGAN).One of the prominent errors in GAGAN that limits the positional accuracy is instrumental biases.Calibration of these biases is particularly important in achieving the CAT I PA landings.In this paper,a new algorithm is proposed to estimate the instrumental biases by modelling the TEC using 4th order polynomial.The algorithm uses values corresponding to a single station for one month period and the results confirm the validity of the algorithm.The experimental results indicate that the estimation precision of the satellite-plus-receiver instrumental bias is of the order of ± 0.17 nsec.The observed mean bias error is of the order − 3.638 nsec and − 4.71 nsec for satellite 1 and 31 respectively.It is found that results are consistent over the period.

  15. Phase fluctuations of GPS signals and irregularities in the high latitude ionosphere during geomagnetic storm

    Science.gov (United States)

    Shagimuratov, I.; Chernouss, S.; Cherniak, Iu.; Efishov, I.; Filatov, M.; Tepenitsyna, N.

    2016-05-01

    In this report we analysed latitudinal occurrence of TEC fluctuations over Europe during October 2, 2013 geomagnetic storm. The data of GPS stations spaced in latitudinal range 68°-54° N over longitude of 20°E were involved in this investigation. The magnetograms of the IMAGE network and geomagnetic pulsations at Lovozero (68°02'N 35°00'W) and Sodankyla (67°22'N 26°38'W) observatories were used as indicator of auroral activity. During October 2, 2013 the strong geomagnetic field variations took place near 05 UT at auroral IMAGE network. We found good similarities between time development of substorm and fluctuations of GPS signals. The bay-like geomagnetic variations were followed by intensive phase fluctuations at auroral and subauroral stations. The strong short-term phase fluctuations were also found at mid-latitude Kaliningrad station near 05 UT that correspond to the maximal intense geomagnetic bay variations. This date confirms the equatorward expansion of the auroral oval. It brings in evidence also the storm time behavior of the irregularities oval obtained from multi-site GPS observations.

  16. High-order ionospheric effects on electron density estimation from Fengyun-3C GPS radio occultation

    Science.gov (United States)

    Li, Junhai; Jin, Shuanggen

    2017-03-01

    GPS radio occultation can estimate ionospheric electron density and total electron content (TEC) with high spatial resolution, e.g., China's recent Fengyun-3C GPS radio occultation. However, high-order ionospheric delays are normally ignored. In this paper, the high-order ionospheric effects on electron density estimation from the Fengyun-3C GPS radio occultation data are estimated and investigated using the NeQuick2 ionosphere model and the IGRF12 (International Geomagnetic Reference Field, 12th generation) geomagnetic model. Results show that the high-order ionospheric delays have large effects on electron density estimation with up to 800 el cm-3, which should be corrected in high-precision ionospheric density estimation and applications. The second-order ionospheric effects are more significant, particularly at 250-300 km, while third-order ionospheric effects are much smaller. Furthermore, the high-order ionospheric effects are related to the location, the local time, the radio occultation azimuth and the solar activity. The large high-order ionospheric effects are found in the low-latitude area and in the daytime as well as during strong solar activities. The second-order ionospheric effects have a maximum positive value when the radio occultation azimuth is around 0-20°, and a maximum negative value when the radio occultation azimuth is around -180 to -160°. Moreover, the geomagnetic storm also affects the high-order ionospheric delay, which should be carefully corrected.

  17. GPS/INS Sensor Fusion Using GPS Wind up Model

    Science.gov (United States)

    Williamson, Walton R. (Inventor)

    2013-01-01

    A method of stabilizing an inertial navigation system (INS), includes the steps of: receiving data from an inertial navigation system; and receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites; calculating a phase wind up correction; correcting at least one of the finite number of carrier phase observables using the phase wind up correction; and calculating a corrected IMU attitude or velocity or position using the corrected at least one of the finite number of carrier phase observables; and performing a step selected from the steps consisting of recording, reporting, or providing the corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position. A GPS stabilized inertial navigation system apparatus is also described.

  18. GPS phase scintillation during the geomagnetic storm of March 17, 2015: The relation to auroral electrojet currents

    DEFF Research Database (Denmark)

    Prikryl, Paul; Ghoddousi-Fard, Reza; Connors, Martin

    and magnetometers. GPS phase scintillation index is computed for L1 signal sampled at the rate of 50 Hz by specialized GPS scintillation receivers of the Expanded Canadian High Arctic Ionospheric Network (ECHAIN). To further extend the geographic coverage, the phasescintillation proxy index is obtained from......-enhanced plasma density (SED) and in the auroral oval during energetic particle precipitation events, substorms and pseudo-breakups in particular. In this paper we examine the relation to auroral electrojet currents observed by arrays of ground-based magnetometers and energetic particle precipitation observed......Ionospheric irregularities cause rapid fluctuations of radio wave amplitude and phase that candegrade GPS positional accuracy and affect performance of radio communication and navigation systems. The ionosphere becomes particularly disturbed during geomagnetic storms caused by impacts of coronal...

  19. Monitoring Animal Behaviour and Environmental Interactions Using Wireless Sensor Networks, GPS Collars and Satellite Remote Sensing

    Directory of Open Access Journals (Sweden)

    Peter Corke

    2009-05-01

    Full Text Available Remote monitoring of animal behaviour in the environment can assist in managing both the animal and its environmental impact. GPS collars which record animal locations with high temporal frequency allow researchers to monitor both animal behaviour and interactions with the environment. These ground-based sensors can be combined with remotely-sensed satellite images to understand animal-landscape interactions. The key to combining these technologies is communication methods such as wireless sensor networks (WSNs. We explore this concept using a case-study from an extensive cattle enterprise in northern Australia and demonstrate the potential for combining GPS collars and satellite images in a WSN to monitor behavioural preferences and social behaviour of cattle.

  20. GPS phase scintillation at high latitudes during the geomagnetic storm of 17-18 March 2015

    DEFF Research Database (Denmark)

    Prikryl, P.; Ghoddousi-Fard, R.; Weygand, J. M.

    2016-01-01

    , and magnetometers. The phase scintillation index is computed for signals sampled at a rate of up to 100 Hz by specialized GPS scintillation receivers supplemented by the phase scintillation proxy index obtained from geodetic-quality GPS data sampled at 1 Hz. In the context of solar wind coupling...... the scintillation and auroral electrojet currents observed by arrays of ground-based magnetometers as well as energetic particle precipitation observed by the DMSP satellites. Equivalent ionospheric currents are obtained from ground magnetometer data using the spherical elementary currents systems technique...... of energetic electron precipitation observed by DMSP satellites with the exception of a period of pulsating aurora when only very weak currents were observed....

  1. Inversion of GPS meteorology data

    Directory of Open Access Journals (Sweden)

    K. Hocke

    Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically

  2. Application of GPS Technologies to study Pre-earthquake processes. A review and future prospects

    Science.gov (United States)

    Pulinets, S. A.; Liu, J. Y. G.; Ouzounov, D.; Hernandez-Pajares, M.; Hattori, K.; Krankowski, A.; Zakharenkova, I.; Cherniak, I.

    2016-12-01

    We present the progress reached by the GPS TEC technologies in study of pre-seismic anomalies in the ionosphere appearing few days before the strong earthquakes. Starting from the first case studies such as 17 August 1999 M7.6 Izmit earthquake in Turkey the technology has been developed and converted into the global near real-time monitoring of seismo-ionospheric effects which is used now in the multiparameter nowcast and forecast of the strong earthquakes. Development of the techniques of the seismo-ionospheric anomalies identification was carried out in parallel with the development of the physical mechanism explaining these anomalies generation. It was established that the seismo-ionospheric anomalies have a self-similarity property, are dependent on the local time and are persistent at least for 4 hours, deviation from undisturbed level could be both positive and negative depending on the leading time (in days) to the moment of impending earthquake and from longitude of anomaly in relation to the epicenter longitude. Low latitude and near equatorial earthquakes demonstrate the magnetically conjugated effect, while the middle and high latitude earthquakes demonstrate the single anomaly over the earthquake preparation zone. From the anomalies morphology the physical mechanism was derived within the framework of the more complex Lithosphere-Atmosphere-Ionosphere-Magnetosphere Coupling concept. In addition to the multifactor analysis of the GPS TEC time series the GIM MAP technology was applied also clearly showing the seismo-ionospheric anomalies locality and their spatial size correspondence to the Dobrovolsky determination of the earthquake preparation zone radius. Application of ionospheric tomography techniques permitted to study not only the total electron content variations but also the modification of the vertical distribution of electron concentration in the ionosphere before earthquakes. The statistical check of the ionospheric precursors passed the

  3. Location - Global Positioning System (GPS) Photos

    Data.gov (United States)

    Army Corps of Engineers, Department of the Army, Department of Defense — Digital photos tagged with GPS location information. The St. Paul District maintains a digital library of over 10,000 GPS photos. Photos are often associated with...

  4. GPS Attitude Determination for Launch Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Toyon Research Corporation proposes to develop a family of compact, low-cost GPS-based attitude (GPS/A) sensors for launch vehicles. In order to obtain 3-D attitude...

  5. GPS operations at Olkiluoto in 2011

    Energy Technology Data Exchange (ETDEWEB)

    Koivula, H.; Kallio, U.; Nyberg, S.; Jokela, J.; Poutanen, M. [Finnish Geodetic Institute, Masala (Finland)

    2012-06-15

    The Finnish Geodetic Institute has studied crustal deformations at Olkiluoto, Kivetty and Romuvaara in co-operation with Posiva Oy since 1995. At Olkiluoto a total of 32 GPS campaigns have been carried out at inner network since 1995 and 17 campaigns at outer network since 2003. Kivetty and Romuvaara were not measured in 2011. In the Olkiluoto inner network 80 percent of the estimated change rates are smaller than 0.10 mm/a. One third of the change rates are statistically significant. They are mainly related to the Olkiluoto permanent station (GPS1) and to the pillars GPS6 and GPS13. The change rates related to GPS6 are not realistic due to the site-specific changes affecting the time series. The maximum change rate (-0.20 mm/a {+-} 0.05 mm/a) is related to GPS13. The time series of GPS13 is half the length of other pillars and therefore, the change rates are more uncertain. In the Olkiluoto outer network the maximum and statistically significant change rate is between GPS1-GPS11 (0.39 mm/a {+-} 0.06 mm/a). Pillar GPS12 was not observed this year. The change rates of baselines GPS1-GPS14 and GPS1-GPS15 are first time statistically significant. The change rates indicate a small movement of the GPS1 pillar. The baseline GPS1-GPS11 crosses an old fracture zone locating in the direction of the Eurajoensalmi, which might be a reason for the deformation. On the other hand, the Onkalo excavations in the vicinity of the Olkiluoto permanent station (GPS1) may cause some movement. Electronic distance measurements have been performed at Olkiluoto at the baseline GPS7-GPS8 using the Mekometer since 2002. The measurements have been carried out simultaneously with GPS campaigns. Based on 19 measurements in 10 years, the trends of the two time series seems to be similar. Due to unmodelled or dismodelled geometrical offsets and the scale difference between GPS measurements and EDM there is about 0.3 mm difference between distances GPS7-GPS8 derived from GPS measurements and EDM

  6. Entry Dispersion Analysis for the Hayabusa Spacecraft using Ground Based Optical Observation

    CERN Document Server

    Yamaguchi, T; Yagi, M; Tholen, D J

    2011-01-01

    Hayabusa asteroid explorer successfully released the sample capsule to Australia on June 13, 2010. Since the Earth reentry phase of sample return was critical, many backup plans for predicting the landing location were prepared. This paper investigates the reentry dispersion using ground based optical observation as a backup observation for radiometric observation. Several scenarios are calculated and compared for the reentry phase of the Hayabusa to evaluate the navigation accuracy of the ground-based observation. The optical observation doesn't require any active reaction from a spacecraft, thus these results show that optical observations could be a steady backup strategy even if a spacecraft had some trouble. We also evaluate the landing dispersion of the Hayabusa only with the optical observation.

  7. Ground-based walking training improves quality of life and exercise capacity in COPD.

    Science.gov (United States)

    Wootton, Sally L; Ng, L W Cindy; McKeough, Zoe J; Jenkins, Sue; Hill, Kylie; Eastwood, Peter R; Hillman, David R; Cecins, Nola; Spencer, Lissa M; Jenkins, Christine; Alison, Jennifer A

    2014-10-01

    This study was designed to determine the effect of ground-based walking training on health-related quality of life and exercise capacity in people with chronic obstructive pulmonary disease (COPD). People with COPD were randomised to either a walking group that received supervised, ground-based walking training two to three times a week for 8-10 weeks, or a control group that received usual medical care and did not participate in exercise training. 130 out of 143 participants (mean±sd age 69±8 years, forced expiratory volume in 1 s 43±15% predicted) completed the study. Compared to the control group, the walking group demonstrated greater improvements in the St George's Respiratory Questionnaire total score (mean difference -6 points (95% CI -10- -2), pimproves quality of life and endurance exercise capacity in people with COPD.

  8. Nulling interferometry: performance comparison between space and ground-based sites for exozodiacal disc detection

    CERN Document Server

    Defrère, D; Foresto, V Coudé du; Danchi, W C; Hartog, R den

    2008-01-01

    Characterising the circumstellar dust around nearby main sequence stars is a necessary step in understanding the planetary formation process and is crucial for future life-finding space missions such as ESA's Darwin or NASA's Terrestrial Planet Finder (TPF). Besides paving the technological way to Darwin/TPF, the space-based infrared interferometers Pegase and FKSI (Fourier-Kelvin Stellar Interferometer) will be valuable scientific precursors in that respect. In this paper, we investigate the performance of Pegase and FKSI for exozodiacal disc detection and compare the results with ground-based nulling interferometers. Besides their main scientific goal (characterising hot giant extrasolar planets), Pegase and FKSI are very efficient in assessing within a few minutes the level of circumstellar dust in the habitable zone around nearby main sequence stars. They are capable of detecting exozodiacal discs respectively 5 and 1 time as dense as the solar zodiacal cloud and they outperform any ground-based instrumen...

  9. Techniques to extend the reach of ground based gravitational wave detectors

    Science.gov (United States)

    Dwyer, Sheila

    2016-03-01

    While the current generation of advanced ground based detectors will open the gravitational wave universe to observation, ground based interferometry has the potential to extend the reach of these observatories to high redshifts. Several techniques have the potential to improve the advanced detectors beyond design sensitivity, including the use of squeezed light, upgraded suspensions, and possibly new optical coatings, new test mass materials, and cryogenic suspensions. To improve the sensitivity by more than a factor of 10 compared to advanced detectors new, longer facilities will be needed. Future observatories capable of hosting interferometers 10s of kilometers long have the potential to extend the reach of gravitational wave astronomy to cosmological distances, enabling detection of binary inspirals from throughout the history of star formation.

  10. Ground-based near-infrared imaging of the HD141569 circumstellar disk

    CERN Document Server

    Boccaletti, A; Marchis, F; Hanh, J

    2003-01-01

    We present the first ground-based near-infrared image of the circumstellar disk around the post-Herbig Ae/Be star HD141569A initially detected with the HST. Observations were carried out in the near-IR (2.2 $\\mu$m) at the Palomar 200-inch telescope using the adaptive optics system PALAO. The main large scale asymmetric features of the disk are detected on our ground-based data. In addition, we measured that the surface brightness of the disk is slightly different than that derived by HST observations (at 1.1 $\\mu$m and 1.6 $\\mu$m). We interpret this possible color-effect in terms of dust properties and derive a minimal

  11. Validation of Aura OMI by Aircraft and Ground-Based Measurements

    Science.gov (United States)

    McPeters, R. D.; Petropavlovskikh, I.; Kroon, M.

    2006-12-01

    Both aircraft-based and ground-based measurements have been used to validate ozone measurements by the OMI instrument on Aura. Three Aura Validation Experiment (AVE) flights have been conducted, in November 2004 and June 2005 with the NASA WB57, and in January/February 2005 with the NASA DC-8. On these flights, validation of OMI was primarily done using data from the CAFS (CCD Actinic Flux Spectroradiometer) instrument, which is used to measure total column ozone above the aircraft. These measurements are used to differentiate changes in stratospheric ozone from changes in total column ozone. Also, changes in ozone over high clouds measured by OMI were checked in a flight over tropical storm Arlene on a flight on June 11th. Ground-based measurements were made during the SAUNA campaign in Sodankyla, Finland, in March and April 2006. Both total column ozone and the ozone vertical distribution were validated.

  12. DEM extraction and its accuracy analysis with ground-based SAR interferometry

    Science.gov (United States)

    Dong, J.; Yue, J. P.; Li, L. H.

    2014-03-01

    Two altimetry models extracting DEM (Digital Elevation Model) with the GBSAR (Ground-Based Synthetic Aperture Radar) technology are studied and their accuracies are analyzed in detail. The approximate and improved altimetry models of GBSAR were derived from the spaceborne radar altimetry based on the principles of the GBSAR technology. The error caused by the parallel ray approximation in the approximate model was analyzed quantitatively, and the results show that the errors cannot be ignored for the ground-based radar system. For the improved altimetry model, the elevation error expression can be acquired by simulating and analyzing the error propagation coefficients of baseline length, wavelength, differential phase and range distance in the mathematical model. By analyzing the elevation error with the baseline and range distance, the results show that the improved altimetry model is suitable for high-precision DEM and the accuracy can be improved by adjusting baseline and shortening slant distance.

  13. Investigating the long-term evolution of subtropical ozone profiles applying ground-based FTIR spectrometry

    OpenAIRE

    García, O.E.; Schneider, M; A. Redondas; Y. González; Hase, F.; Blumenstock, T.; Sepúlveda, E.

    2012-01-01

    This study investigates the long-term evolution of subtropical ozone profile time series (1999–2010) obtained from ground-based FTIR (Fourier Transform InfraRed) spectrometry at the Izaña Observatory ozone super-site. Different ozone retrieval strategies are examined, analysing the influence of an additional temperature retrieval and different constraints. The theoretical assessment reveals that the FTIR system is able to resolve four independent ozone layers with a precision of better than 6...

  14. Space Fence Ground-Based Radar System Increment 1 (Space Fence Inc 1)

    Science.gov (United States)

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-438 Space Fence Ground-Based Radar System Increment 1 (Space Fence Inc 1) As of FY 2017...11 Track to Budget 17 Cost and Funding 18 Low Rate Initial Production 23 Foreign Military Sales 24 Nuclear Costs 24 Unit Cost...Document CLIN - Contract Line Item Number CPD - Capability Production Document CY - Calendar Year DAB - Defense Acquisition Board DAE - Defense Acquisition

  15. Particle production during inflation and gravitational waves detectable by ground-based interferometers

    OpenAIRE

    Cook, Jessica L.; Sorbo, Lorenzo

    2011-01-01

    Inflation typically predicts a quasi scale-invariant spectrum of gravitational waves. In models of slow-roll inflation, the amplitude of such a background is too small to allow direct detection without a dedicated space-based experiment such as the proposed BBO or DECIGO. In this paper we note that particle production during inflation can generate a feature in the spectrum of primordial gravitational waves. We discuss the possibility that such a feature might be detected by ground-based laser...

  16. NASA Requirements for Ground-Based Pressure Vessels and Pressurized Systems (PVS). Revision C

    Science.gov (United States)

    Greulich, Owen Rudolf

    2017-01-01

    The purpose of this document is to ensure the structural integrity of PVS through implementation of a minimum set of requirements for ground-based PVS in accordance with this document, NASA Policy Directive (NPD) 8710.5, NASA Safety Policy for Pressure Vessels and Pressurized Systems, NASA Procedural Requirements (NPR) 8715.3, NASA General Safety Program Requirements, applicable Federal Regulations, and national consensus codes and standards (NCS).

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

    OpenAIRE

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

    2011-01-01

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

  18. The Gaia Era: synergy between space missions and ground based surveys

    CERN Document Server

    Vallenari, A

    2008-01-01

    The Gaia mission is expected to provide highly accurate astrometric, photometric, and spectroscopic measurements for about $10^9$ objects. Automated classification of detected sources is a key part of the data processing. Here a few aspects of the Gaia classification process are presented. Information from other surveys at longer wavelengths, and from follow-up ground based observations will be complementary to Gaia data especially at faint magnitudes, and will offer a great opportunity to understand our Galaxy.

  19. First-generation Science Cases for Ground-based Terahertz Telescopes

    CERN Document Server

    Hirashita, Hiroyuki; Matsushita, Satoki; Takakuwa, Shigehisa; Nakamura, Masanori; Asada, Keiichi; Liu, Hauyu Baobab; Urata, Yuji; Wang, Ming-Jye; Wang, Wei-Hao; Takahashi, Satoko; Tang, Ya-Wen; Chang, Hsian-Hong; Huang, Kuiyun; Morata, Oscar; Otsuka, Masaaki; Lin, Kai-Yang; Tsai, An-Li; Lin, Yen-Ting; Srinivasan, Sundar; Martin-Cocher, Pierre; Pu, Hung-Yi; Kemper, Francisca; Patel, Nimesh; Grimes, Paul; Huang, Yau-De; Han, Chih-Chiang; Huang, Yen-Ru; Nishioka, Hiroaki; Lin, Lupin Chun-Che; Zhang, Qizhou; Keto, Eric; Burgos, Roberto; Chen, Ming-Tang; Inoue, Makoto; Ho, Paul T P

    2015-01-01

    Ground-based observations at terahertz (THz) frequencies are a newly explorable area of astronomy for the next ten years. We discuss science cases for a first-generation 10-m class THz telescope, focusing on the Greenland Telescope as an example of such a facility. We propose science cases and provide quantitative estimates for each case. The largest advantage of ground-based THz telescopes is their higher angular resolution (~ 4 arcsec for a 10-m dish), as compared to space or airborne THz telescopes. Thus, high-resolution mapping is an important scientific argument. In particular, we can isolate zones of interest for Galactic and extragalactic star-forming regions. The THz windows are suitable for observations of high-excitation CO lines and [N II] 205 um lines, which are scientifically relevant tracers of star formation and stellar feedback. Those lines are the brightest lines in the THz windows, so that they are suitable for the initiation of ground-based THz observations. THz polarization of star-forming...

  20. Interactive dynamic three-dimensional scene for the ground-based three-dimensional display

    Science.gov (United States)

    Hou, Peining; Sang, Xinzhu; Guo, Nan; Chen, Duo; Yan, Binbin; Wang, Kuiru; Dou, Wenhua; Xiao, Liquan

    2016-10-01

    Three-dimensional (3D) displays provides valuable tools for many fields, such as scientific experiment, education, information transmission, medical imaging and physical simulation. Ground based 360° 3D display with dynamic and controllable scene can find some special applications, such as design and construction of buildings, aeronautics, military sand table and so on. It can be utilized to evaluate and visualize the dynamic scene of the battlefield, surgical operation and the 3D canvas of art. In order to achieve the ground based 3D display, the public focus plane should be parallel to the camera's imaging planes, and optical axes should be offset to the center of public focus plane in both vertical and horizontal directions. Virtual cameras are used to display 3D dynamic scene with Unity 3D engine. Parameters of virtual cameras for capturing scene are designed and analyzed, and locations of virtual cameras are determined by the observer's eye positions in the observing space world. An interactive dynamic 3D scene for ground based 360° 3D display is demonstrated, which provides high-immersion 3D visualization.

  1. Intercomparison of ground-based ozone and NO2 measurements during the MANTRA 2004 campaign

    Directory of Open Access Journals (Sweden)

    K. Strong

    2007-11-01

    Full Text Available The MANTRA (Middle Atmosphere Nitrogen TRend Assessment 2004 campaign took place in Vanscoy, Saskatchewan, Canada (52° N, 107° W from 3 August to 15 September, 2004. In support of the main balloon launch, a suite of five zenith-sky and direct-Sun-viewing UV-visible ground-based spectrometers was deployed, primarily measuring ozone and NO2 total columns. Three Fourier transform spectrometers (FTSs that were part of the balloon payload also performed ground-based measurements of several species, including ozone. Ground-based measurements of ozone and NO2 differential slant column densities from the zenith-viewing UV-visible instruments are presented herein. They are found to partially agree within NDACC (Network for the Detection of Atmospheric Composition Change standards for instruments certified for process studies and satellite validation. Vertical column densities of ozone from the zenith-sky UV-visible instruments, the FTSs, a Brewer spectrophotometer, and ozonesondes are compared, and found to agree within the combined error estimates of the instruments (15%. NO2 vertical column densities from two of the UV-visible instruments are compared, and are also found to agree within combined error (15%.

  2. Limitation of Ground-based Estimates of Solar Irradiance Due to Atmospheric Variations

    Science.gov (United States)

    Wen, Guoyong; Cahalan, Robert F.; Holben, Brent N.

    2003-01-01

    The uncertainty in ground-based estimates of solar irradiance is quantitatively related to the temporal variability of the atmosphere's optical thickness. The upper and lower bounds of the accuracy of estimates using the Langley Plot technique are proportional to the standard deviation of aerosol optical thickness (approx. +/- 13 sigma(delta tau)). The estimates of spectral solar irradiance (SSI) in two Cimel sun photometer channels from the Mauna Loa site of AERONET are compared with satellite observations from SOLSTICE (Solar Stellar Irradiance Comparison Experiment) on UARS (Upper Atmospheric Research Satellite) for almost two years of data. The true solar variations related to the 27-day solar rotation cycle observed from SOLSTICE are about 0.15% at the two sun photometer channels. The variability in ground-based estimates is statistically one order of magnitude larger. Even though about 30% of these estimates from all Level 2.0 Cimel data fall within the 0.4 to approx. 0.5% variation level, ground-based estimates are not able to capture the 27-day solar variation observed from SOLSTICE.

  3. Kepler and Ground-based Transits of the Exo-Neptune HAT-P-11b

    CERN Document Server

    Deming, Drake; Jackson, Brian; Peterson, Steven W; Agol, Eric; Knutson, Heather A; Jennings, Donald E; Haase, Flynn; Bays, Kevin

    2011-01-01

    We analyze 26 archival Kepler transits of the exo-Neptune HAT-P-11b, supplemented by ground-based transits observed in the blue (B-band) and near-IR (J-band). Both the planet and host star are smaller than previously believed; our analysis yields Rp=4.31 +/-0.06 Earth-radii, and Rs = 0.683 +/-0.009 solar radii, both about 3-sigma smaller than the discovery values. Our ground-based transit data at wavelengths bracketing the Kepler bandpass serve to check the wavelength dependence of stellar limb darkening, and the J-band transit provides a precise and independent constraint on the transit duration. Both the limb darkening and transit duration from our ground-based data are consistent with the new Kepler values for the system parameters. Our smaller radius for the planet implies that its gaseous envelope can be less extensive than previously believed, being very similar to the H-He envelope of GJ436b and Kepler-4b. HAT-P-11 is an active star, and signatures of star spot crossings are ubiquitous in the Kepler tr...

  4. Structure and evolution of Pluto's Atmosphere from ground-based stellar occultations between 2002 and 2015

    Science.gov (United States)

    Meza, Erick; Sicardy, Bruno; Rio de Janeiro occultation team, Granada occultation team, International Occultation and Timing Association

    2016-10-01

    Ground-Based stellar occultations probe Pluto's atmosphere from about 3 km altitude (~ 10 μbar pressure level) up to 260 km altitude (~0.1 μbar). Our main goal is to derive Pluto's atmosphere evolution using thirteen ground-based occultations observed between 2002 and 2015 (plus 2016, if available). We consistently analyze the light curves using the Dias et al. (ApJ 811, 53, 2015) model, and confirm the general pressure increase by a factor of about 1.5 between 2002 and 2015 and a factor of almost three between 1988 and 2015. Implications for Pluto's seasonal evolution will be briefly discussed in the context of the New Horizons (NH) findings.Ground-based-derived temperature profiles will be compared with NH's results, where we use new temperature boundary conditions in our inversion procedures, as given by NH near 260 km altitude. Although the profiles reasonably agree, significant discrepancies are observed both in the deeper stratospheric zone (altitude topographic features revealed by NH.Finally, possible correlations between spike activity in the occultation light-curves and local underlying presence of free nitrogen ice terrains will be investigated.Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ ERC Grant Agreement n 669416 "LUCKY STAR").

  5. Flow Characteristics of Tidewater Glaciers in Greenland and Alaska using Ground-Based LiDAR

    Science.gov (United States)

    Finnegan, D. C.; Stearns, L. A.; Hamilton, G. S.; O'Neel, S.

    2010-12-01

    LiDAR scanning systems have been employed to characterize and quantify multi-temporal glacier and ice sheet changes for nearly three decades. Until recently, LiDAR scanning systems were limited to airborne and space-based platforms which come at a significant cost to deploy and are limited in spatial and temporal sampling capabilities necessary to compare with in-situ field measurements. Portable ground-based LiDAR scanning systems are now being used as a glaciological tool. We discuss research efforts to employ ground-based near-infrared LiDAR systems at two differing tidewater glacier systems in the spring of 2009; Helheim Glacier in southeast Greenland and Columbia Glacier in southeast Alaska. Preliminary results allow us to characterize short term displacement rates and detailed observations of calving processes. These results highlight the operational limitations and capabilities of commercially available LiDAR systems, and allow us to identify optimal operating characteristics for monitoring small to large-scale tidewater glaciers in near real-time. Furthermore, by identifying the operational limitations of these sensors it allows for optimal design characteristics of new sensors necessary to meet ground-based calibration and validation requirements of ongoing scientific missions.

  6. Phase-coherent mapping of gravitational-wave backgrounds using ground-based laser interferometers

    CERN Document Server

    Romano, Joseph D; Cornish, Neil J; Gair, Jonathan; Mingarelli, Chiara M F; van Haasteren, Rutger

    2015-01-01

    We extend the formalisms developed in Gair et al. and Cornish and van Haasteren to create maps of gravitational-wave backgrounds using a network of ground-based laser interferometers. We show that in contrast to pulsar timing arrays, which are insensitive to half of the gravitational-wave sky (the curl modes), a network of ground-based interferometers is sensitive to both the gradient and curl components of the background. The spatial separation of a network of interferometers, or of a single interferometer at different times during its rotational and orbital motion around the Sun, allows for recovery of both components. We derive expressions for the response functions of a laser interferometer in the small-antenna limit, and use these expressions to calculate the overlap reduction function for a pair of interferometers. We also construct maximum-likelihood estimates of the + and x-polarization modes of the gravitational-wave sky in terms of the response matrix for a network of ground-based interferometers, e...

  7. Modeling of Heat and Mass Transfer in a TEC-Driven Lyophilizer

    Science.gov (United States)

    Yuan, Zeng-Guang; Hegde, Uday; Litwiller, Eric; Flynn, Michael; Fisher, John

    2006-01-01

    Dewatering of wet waste during space exploration missions is important for crew safety as it stabilizes the waste. It may also be used to recover water and serve as a preconditioning step for waste compaction. A thermoelectric cooler (TEC)-driven lyophilizer is under development at NASA Ames Research Center for this purpose. It has three major components: (i) an evaporator section where water vapor sublimes from the frozen waste, (ii) a condenser section where this water vapor deposits as ice, and (iii) a TEC section which serves as a heat pump to transfer heat from the condenser to the evaporator. This paper analyses the heat and mass transfer processes in the lyophilizer in an effort to understand the ice formation behavior in the condenser. The analysis is supported by experimental observations of ice formation patterns in two different condenser units.

  8. Chemistry Teacher Education Coalition: Extending the PhysTEC Model to Chemistry

    Science.gov (United States)

    Kirchhoff, Mary

    2012-02-01

    The American Association of Employment in Education reports that chemistry, like physics, faces ``some shortage'' of educators. Inspired by the success of the Physics Teacher Education Coalition (PhysTEC), the American Chemical Society (ACS) is developing the Chemistry Teacher Education Coalition (CTEC) to actively engage chemistry departments in the preparation of future chemistry teachers. Engaging chemistry departments in teacher preparation would increase the number and diversity of well-prepared high school chemistry teachers while catalyzing cultural change within chemistry departments. Many features of PhysTEC, such as a grant competition to create model teacher preparation programs and regular conferences, are directly applicable to chemistry. This presentation will provide an overview of ACS efforts to launch a successful CTEC initiative.

  9. Laboratory study on the molluscicidal effect of Earth Tec: an environmentally responsible copper sulfate product.

    Science.gov (United States)

    Ahmed, M M; Hady, H M; Salama, M M; el-Ghazali, S

    1994-08-01

    Studies were carried out, under laboratory conditions to evaluate the molluscicidal activity of Earth Tec on Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni. Earth Tec is an environmentally responsible copper sulfate product manufactured and marketed as an algicide/bactericide with an active ingredient form of copper ion (Cu++). A single application, of 1 ppm of copper equivalent, for 24 hours caused 100% mortality rate of the snails. Exposure for 48 hours to 1 ppm and 2 weeks to 0.25 ppm caused mortality rates of 84% and 100% respectively. It was concluded that this chemical compound is a promising molluscicide. Field studies are ongoing and will be published in due time.

  10. Diagnosing dementia with confidence by GPs.

    NARCIS (Netherlands)

    Hout, H.P.J. van; Vernooij-Dassen, M.J.F.J.; Stalman, W.A.B.

    2007-01-01

    BACKGROUND: Earlier reports suggest limited clinical reasoning and substantial uncertainty of GPs in assessing patients suspected of dementia. OBJECTIVE: To explore the predictors of GPs to decide on the presence and absence of dementia as well as the predictors of diagnostic confidence of GPs.

  11. The SMS-GPS-Trip-Method

    DEFF Research Database (Denmark)

    Reinau, Kristian Hegner; Harder, Henrik; Weber, Michael

    2015-01-01

    This article presents a new method for collecting travel behavior data, based on a combination of GPS tracking and SMS technology, coined the SMS–GPS-Trip method. The state-of-the-art method for collecting data for activity based traffic models is a combination of travel diaries and GPS tracking...

  12. Diagnosing dementia with confidence by GPs.

    NARCIS (Netherlands)

    Hout, H.P.J. van; Vernooij-Dassen, M.J.F.J.; Stalman, W.A.B.

    2007-01-01

    BACKGROUND: Earlier reports suggest limited clinical reasoning and substantial uncertainty of GPs in assessing patients suspected of dementia. OBJECTIVE: To explore the predictors of GPs to decide on the presence and absence of dementia as well as the predictors of diagnostic confidence of GPs. DESI

  13. INS/GPS Integration Architectures

    Science.gov (United States)

    2010-03-01

    to maintain the mean code tracking error close to zero. RF FILTER I/Q DEMOD SAMPLING CORRELATION AND INTEGRATION SQUARE LAW DETECTION kth...Q(t) INERTIAL SENSORS OTHER SENSORS CORRELATOR BANK (n) x ′ˆ Figure 2.9: Code tracking information flow diagram for GPS-based navigator. The

  14. Recent GPS Results at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Behrend, Dirk; Imfeld, Hans L.; /SLAC

    2005-08-17

    The Alignment Engineering Group (AEG) makes use of GPS technology for fulfilling part of its above ground surveying tasks at SLAC since early 2002. A base station (SLAC M40) has been set up at a central location of the SLAC campus serving both as master station for real-time kinematic (RTK) operations and as datum point for local GPS campaigns. The Leica RS500 system is running continuously and the GPS data are collected both externally (logging PC) and internally (receiver flashcard). The external logging is facilitated by a serial to Ethernet converter and an Ethernet connection at the station. Internal logging (ring buffer) is done for data security purposes. The weatherproof boxes for the instrumentation are excellent shelters against rain and wind, but do heat up considerably in sun light. Whereas the GPS receiver showed no problems, the Pacific Crest PDL 35 radio shut down several times due to overheating disrupting the RTK operations. In order to prevent heat-induced shutdowns, a protection against direct sun exposure (shading) and a constant air circulation system (ventilation) were installed. As no further shutdowns have occurred so far, it appears that the two measures successfully mended the heat problem.

  15. Contents of GPS Data Files

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, John P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carver, Matthew Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Norman, Benjamin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-12-09

    There are no very detailed descriptions of most of these instruments in the literature – we will attempt to fix that problem in the future. The BDD instruments are described in [1]. One of the dosimeter instruments on CXD boxes is described in [2]. These documents (or web links to them) and a few others are in this directory tree. The cross calibration of the CXD electron data with RBSP is described in [3]. Each row in the data file contains the data from one time bin from a CXD or BDD instrument along with a variety of parameters derived from the data. Time steps are commandable but 4 minutes is a typical setting. These instruments are on many (but not all) GPS satellites which are currently in operation. The data come from either BDD instruments on GPS Block IIR satellites (SVN41 and 48), or else CXD-IIR instruments on GPS Block IIR and IIR-M satellites (SVN53-61) or CXD-IIF instruments on GPS block IIF satellites (SVN62-73). The CXD-IIR instruments on block IIR and IIR(M) satellites use the same design.

  16. Optimal Preprocessing Of GPS Data

    Science.gov (United States)

    Wu, Sien-Chong; Melbourne, William G.

    1994-01-01

    Improved technique for preprocessing data from Global Positioning System receiver reduces processing time and number of data to be stored. Optimal in sense that it maintains strength of data. Also increases ability to resolve ambiguities in numbers of cycles of received GPS carrier signals.

  17. Animal Tracking ARGOS vs GPS

    Science.gov (United States)

    Robinson, P. W.; Costa, D.; Arnould, J.; Weise, M.; Kuhn, C.; Simmons, S. E.; Villegas, S.; Tremblay, Y.

    2006-12-01

    ARGOS satellite tracking technology has enabled a tremendous increase in our understanding of the movement patterns of a diverse array of marine vertebrates from Sharks to marine mammals. Our current understanding has moved from simple descriptions of large scale migratory patterns to much more sophisticated comparisons of animal movements and behavior relative to oceanic features. Further, animals are increasingly used to carry sensors that can acquire water column temperature and salinity profiles. However, a major limitation of this work is the spatial precision of ARGOS locations. ARGOS provides 7 location qualities that range from 3,2,1,0,A,B,Z and correspond to locations with a precision of 150m to tens of kilometers. Until recently, GPS technology could not be effectively used with marine mammals because they did not spend sufficient time at the surface to allow complete acquisition of satellite information. The recent development of Fastloc technology has allowed the development of GPS tags that can be deployed on marine mammals. Here we compare the location quality and frequency derived from standard ARGOS PTTs to Fastloc GPS locations acquired from 11 northern elephant seals, 5 California and 5 Galapagos sea lions and 1 Cape and 3 Australian fur seals. Our results indicate that GPS technology will greatly enhance our ability to understand the movement patterns of marine vertebrates and the in-situ oceanographic data they collect.

  18. Analysis of ionospheric TEC from GNSS observables over the Turkish region and predictability of IRI and SPIM models

    Science.gov (United States)

    Ansari, Kutubuddin; Corumluoglu, Ozsen; Panda, Sampad Kumar

    2017-04-01

    The present study investigates the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish Permanent GNSS Network (TPGN) and International GNSS Services (IGS) observations during the period from January 2015 to December 2015. The corresponding TEC predicted by the International Reference Ionosphere (IRI 2012) and Standard Plasmasphere-Ionosphere Model (SPIM), and interpolated from Global Ionosphere Maps (GIMs) are evaluated to realize their reliability over the region. We studied the diurnal and monthly behavior of TEC and the relative TEC deviations along with the upper and lower quartiles to represent its spatio-temporal variability. The diurnal variation of GNSS-derived TEC indicates its maximum peak value around 10.00 UT which decreases gradually to attain minimum value after midnight. The monthly maximum value of TEC is observed in March followed by May and August, and the lowest value is seen during September. Studies show that the monthly relative deviation of TEC variability lies in the range of -1 to 4 units for all stations with the maximum difference between positive and negative variability remaining around 5. The studies also cover seasonal variation, grand-mean of ionospheric TEC and TEC intensity from the TPGN. The seasonal ionospheric VTEC pattern over all stations depicts slight increment in VTEC distribution during March equinox compared to September equinox. The December solstice perceived relatively higher VTEC than June solstice. The overall of VTEC values enhanced at all stations towards end of the year 2015 compare to mid of year due the high solar activity. The maximum grand-mean of VTEC is registered in March equinox while the lowest value is seen in September irrespective of all stations. The measured grand-mean intensity variations of VTEC values are in ascending phase during March, May, August and November months, but in descending phase during February, April, June and September

  19. Integrated navigation of aerial robot for GPS and GPS-denied environment

    Science.gov (United States)

    Suzuki, Satoshi; Min, Hongkyu; Wada, Tetsuya; Nonami, Kenzo

    2016-09-01

    In this study, novel robust navigation system for aerial robot in GPS and GPS- denied environments is proposed. Generally, the aerial robot uses position and velocity information from Global Positioning System (GPS) for guidance and control. However, GPS could not be used in several environments, for example, GPS has huge error near buildings and trees, indoor, and so on. In such GPS-denied environment, Laser Detection and Ranging (LIDER) sensor based navigation system have generally been used. However, LIDER sensor also has an weakness, and it could not be used in the open outdoor environment where GPS could be used. Therefore, it is desired to develop the integrated navigation system which is seamlessly applied to GPS and GPS-denied environments. In this paper, the integrated navigation system for aerial robot using GPS and LIDER is developed. The navigation system is designed based on Extended Kalman Filter, and the effectiveness of the developed system is verified by numerical simulation and experiment.

  20. 2009年6至7月华南地区电离层TEC扰动研究%Study of the South China Ionospheric TEC Disturbances During June-July 2009

    Institute of Scientific and Technical Information of China (English)

    黄江; 邓柏昌; 刘伟峰; 徐杰; 黄林峰; 赵文化

    2011-01-01

    电离层TEC(Total Electron Content)扰动与多种扰动源相关联.2009年6至7月期间存在地震和日全食的扰动源.利用广州地区GPS监测网在2009年6至7月连续监测到的TEC数据,通过采用前15天数据的滑动窗口对数据进行处理,从时间序列和空间分布两方面分析了华南地区电离层TEC扰动特征.结果显示,2009年6至7月华南地区电离层TEC扰动和该时期发生的地震以及日全食事件可能有关联;2009年7月多个地震发生引起的电离层扰动特征为,震前出现的是正异常,发震当天或震后有可能是正异常,也有可能是负异常;7月22日日全食当天TEC扰动为正异常,推测该正异常是地磁活动、地震活动及日全食综合效应的结果.%There are many origins of ionospheric TEC (Total Electron Content) disturbances during June-July 2009, including several earthquakes and a total solar eclipse. In current study, using the GFS-TEC date observed during June-July 2009 in Guangzhou GPS station and processed by a sliding window with the data of prior 15 days, the characters of South China ionosphere are investigated in spatial and temporal distribution. The results indicate that there are possible relations between the South China ionospheric TEC disturbances and seismic-activities as well as total solar eclipse during June-July 2009. The characters of ionospheric TEC disturbance induced by several earthquakes are commented as follows: positive values before earthquake, positive values or negative values near and after the occurrence of earthquake, even more, that the positive values on the day of total solar eclipse (22 July 2009) may be accounted for magnetic activities, seismic activities and total solar eclipse.

  1. AzTEC 1.1 mm OBSERVATIONS OF THE MBM12 MOLECULAR CLOUD

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M. J.; Kim, S.; Youn, S.; Kang, Y.-W. [Department of Astronomy and Space Science, Sejong University, KwangJin-gu, KunJa-dong 98, Seoul 143-747 (Korea, Republic of); Yun, M. S.; Wilson, G. W. [Department of Astronomy, University of Massachusetts, 710 North Pleasant St., Amherst, MA 01003 (United States); Aretxaga, I.; Hughes, D. H.; Humphrey, A. [Instituto Nacional de Astrofisca, Optica y Electronica, Tonantzintla, Puebla (Mexico); Williams, J. P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Austermann, J. E. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80309 (United States); Perera, T. A. [Department of Physics, Illinois Wesleyan University, Bloomington, IL 61701 (United States); Mauskopf, P. D. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Magnani, L., E-mail: sek@sejong.ac.kr [Department of Physics and Astronomy, The University of Georgia, Athens, GA 30602-2451 (United States)

    2012-02-10

    We present 1.1 mm observations of the dust continuum emission from the MBM12 high-latitude molecular cloud observed with the Astronomical Thermal Emission Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. We surveyed 6.34 deg{sup 2} centered on MBM12, making this the largest area that has ever been surveyed in this region with submillimeter and millimeter telescopes. Eight secure individual sources were detected with a signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered to be real astronomical objects compared to the other candidates based on calculations of the false detection rate. The distribution of the detected 1.1 mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of the 100 {mu}m emission and the {sup 12}CO emission. We detected the 1.1 mm dust continuum emitting sources associated with two classical T Tauri stars, LkH{alpha}262 and LkH{alpha}264. Observations of spectral energy distributions (SEDs) indicate that LkH{alpha}262 is likely to be Class II (pre-main-sequence star), but there are also indications that it could be a late Class I (protostar). A flared disk and a bipolar cavity in the models of Class I sources lead to more complicated SEDs. From the present AzTEC observations of the MBM12 region, it appears that other sources detected with AzTEC are likely to be extragalactic and located behind MBM12. Some of these have radio counterparts and their star formation rates are derived from a fit of the SEDs to the photometric evolution of galaxies in which the effects of a dusty interstellar medium have been included.

  2. AzTEC Millimetre Survey of the COSMOS Field: I. Data Reduction and Source Catalogue

    CERN Document Server

    Scott, K S; Perera, T A; Wilson, G W; Aretxaga, I; Bock, J J; Hughes, D H; Kang, Y; Kim, S; Mauskopf, P D; Sanders, D B; Scoville, N; Yun, M S

    2008-01-01

    We present a 1.1 mm wavelength imaging survey covering 0.3 sq. deg. in the COSMOS field. These data, obtained with the AzTEC continuum camera on the James Clerk Maxwell Telescope (JCMT), were centred on a prominent large-scale structure over-density which includes a rich X-ray cluster at z = 0.73. A total of 50 millimetre galaxy candidates, with a significance ranging from 3.5-8.5 sigma, are extracted from the central 0.15 sq. deg. area which has a uniform sensitivity of 1.3 mJy/beam. Sixteen sources are detected with S/N > 4.5, where the expected false-detection rate is zero, of which a surprisingly large number (9) have intrinsic (de-boosted) fluxes > 5 mJy at 1.1 mm. Assuming the emission is dominated by radiation from dust, heated by a massive population of young, optically-obscured stars, then these bright AzTEC sources have FIR luminosities > 6 x 10^12 L(sun) and star formation-rates > 1100 M(sun)/yr. Two of these nine bright AzTEC sources are found towards the extreme peripheral region of the X-ray clu...

  3. A new TEC interpolation method based on the least squares collocation for high accuracy regional ionospheric maps

    Science.gov (United States)

    Krypiak-Gregorczyk, Anna; Wielgosz, Paweł; Jarmołowski, Wojciech

    2017-04-01

    The ionosphere plays a crucial role in space weather that affects satellite navigation as the ionospheric delay is one of the major errors in GNSS. On the other hand, GNSS observations are widely used to determine the amount of ionospheric total electron content (TEC). An important aspect in the electron content estimation at regional and global scale is adopting the appropriate interpolation strategy. In this paper we propose and validate a new method for regional TEC modeling based on least squares collocation (LSC) with noise variance estimation. This method allows for providing accurate TEC maps with high spatial and temporal resolution. Such maps may be used to support precise GNSS positioning and navigation, e.g. in RTK mode and also in the ionosphere studies. To test applicability of new TEC maps to positioning, double-difference ionospheric corrections were derived from the maps and their accuracy was analyzed. In addition, the corrections were applied to GNSS positioning and validated in ambiguity resolution domain. The tests were carried out during a strong ionospheric storm when the ionosphere is particularly difficult to model. The performance of the new approach was compared to IGS and UPC global, and CODE regional TEC maps. The results showed an advantage of our solution with resulting accuracy of the relative ionospheric corrections usually better than 10 cm, even during the ionospheric disturbances. This proves suitability of our regional TEC maps for, e.g. supporting fast ambiguity resolution in kinematic GNSS positioning.

  4. Comparison of the Fenwal Amicus and Fresenius Com.Tec cell separators for autologous peripheral blood progenitor cell collection.

    Science.gov (United States)

    Altuntas, Fevzi; Kocyigit, Ismail; Ozturk, Ahmet; Kaynar, Leylagul; Sari, Ismail; Oztekin, Mehmet; Solmaz, Musa; Eser, Bulent; Cetin, Mustafa; Unal, Ali

    2007-04-01

    Peripheral blood progenitor cells (PBPC) are commonly used as a stem cell source for autologous transplantation. This study was undertaken to evaluate blood cell separators with respect to separation results and content of the harvest. Forty autologous PBPC collections in patients with hematological malignancies were performed with either the Amicus or the COM.TEC cell separators. The median product volume was lower with the Amicus compared to the COM.TEC (125 mL vs. 300 mL; p COM.TEC (3.0 x 10(6) vs. 4.1 x 10(6); p = 0.129). There was a statistically higher mean volume of ACD used in collections on the Amicus compared to the COM.TEC (1040 +/- 241 mL vs. 868 +/- 176 mL; p = 0.019). There was a statistical difference in platelet (PLT) contamination of the products between the Amicus and the COM.TEC (0.3 x 10(11) vs. 1.1 x 10(11); p COM.TEC compared to the Amicus instruments (18.5% vs. 9.5%; p = 0.028). In conclusion, both instruments collected PBPCs efficiently. However, Amicus has the advantage of lower PLT contamination in the product, and less decrease in PB platelet count with lower product volume in autologous setting.

  5. A Comparison of Snow Depth from GPS-Interferometry vs. AMSR-E/AMSR-2

    Science.gov (United States)

    Kim, E. J.; Patel, H.; Wu, A.; Braun, J.; Small, E. E.; Larson, K. M.

    2013-12-01

    The validation of snow data products from satellite sensors has perennially faced the challenge of finding station data that is both widely distributed and possessing sufficient spatial density to provide accurate validation statistics. Point data from ground truth stations have been widely used despite the orders-of-magnitude scale mismatch as well as the insufficient spatial density; this has persisted mainly due to the lack of better alternatives. We evaluate a novel source of validation data that uses ground-based GPS networks, by comparison against snow data products from the AMSR-E sensor aboard the Aqua satellite and now the AMSR2 sensor aboard the GCOM-W1satellite. There are three advantageous features of this approach. First, the GPS networks already exist. Second, the thousands of sites are widely distributed spatially and have a higher spatial density than other stations currently used for snow validation. And third, the observed area of the GPS technique approaches 10,000 m2--much larger than point-scale station observations (1 to 10 m2). Evaluating the new GPS approach along with the more well-known AMSR-E/AMSR-2 snow depth product will provide a baseline for exploiting this potentially large new validation data source in a variety of remote sensing science studies. This work is based on recent advances in GPS techniques by Larson et al that have allowed geodetic quality GPS instrumentation to be used to measure changes in soil moisture and snow depth in the region surrounding GPS antennas. These retrievals relate observed changes in ground reflected GPS signals to changes in either the soil conditions around the antenna or the depth of snow at the site. In this paper, we will focus solely on snow depth. Observations from several GPS stations from the Plate Boundary Observatory (PBO), operating in varied locations in the western United States have been compared with AMSR-E and/or AMSR-2 snow retrievals. These sites span a range of climates (especially

  6. Comparison of Thermal Structure Results from Venus Express and Ground Based Observations since Vira

    Science.gov (United States)

    Limaye, Sanjay

    2016-07-01

    An international team was formed in 2013 through the International Space Studies Institute (Bern, Switzerland) to compare recent results of the Venus atmospheric thermal structure from spacecraft and ground based observations made since the Venus International Reference Atmosphere (VIRA) was developed (Kliore et al., 1985, Keating et al., 1985). Five experiments on European Space Agency's Venus Express orbiter mission have yielded results on the atmospheric structure during is operational life (April 2006 - November 2014). Three of these were from occultation methods: at near infrared wavelengths from solar occultations, (SOIR, 70 - 170 km), at ultraviolet wavelengths from stellar occultations (SPICAV, 90-140 km), and occultation of the VEx-Earth radio signal (VeRa, 40-90 km). In-situ drag measurements from three different techniques (accelerometry, torque, and radio tracking, 130 - 200 km) were also obtained using the spacecraft itself while passive infrared remote sensing was used by the VIRTIS experiment (70 - 120 km). The only new data in the -40-70 km altitude range are from radio occultation, as no new profiles of the deep atmosphere have been obtained since the VeGa 2 lander measurements in 1985 (not included in VIRA). Some selected ground based results available to the team were also considered by team in the inter comparisons. The temperature structure in the lower thermosphere from disk resolved ground based observations (except for one ground based investigation), is generally consistent with the Venus Express results. These experiments sampled at different periods, at different locations and at different local times and have different vertical and horizontal resolution and coverage. The data were therefore binned in latitude and local time bins and compared, ignoring temporal variations over the life time of the Venus Express mission and assumed north-south symmetry. Alternating warm and cooler layers are present in the 120-160 altitude range in results

  7. Effect of the X5.4 Class Solar Flare Event of Solar Cycle 24 ON the GPS Signal Reception in Peninsular Malaysia

    Science.gov (United States)

    Ismail, S.; Musa, T. A.; Aris, W. A. W.; Gopir, G.

    2016-09-01

    In this paper, we examine the effect of solar flare event on the Global Positioning System (GPS) signal reception in Peninsular Malaysia during the X5.4 class solar flare on 7th March 2012, 00:24 UT at active region AR1429. GPS data from six MyRTKnet stations that cover the northern, southern, western and eastern regions of Peninsular Malaysia were used, namely Langkawi (Kedah), Bandar Baharu (Pulau Pinang), Pekan (Pahang), Mersing (Johor), Tanjung Pengelih (Johor) and Malacca (Malacca). The total electron content (TEC) was estimated based on the single layer ionospheric model. Next, the ionospheric delay for each GPS frequency of L1 (1575.42 MHz), L2 (1227.60 MHz) and L5 (1176.45 MHz) was then calculated. The results show that solar flare event can influence the GPS signal reception in Peninsular Malaysia where the X5.4 class solar flare shows significant effect of the ionospheric delay within the range of 9 m - 20 m. These research findings will significantly contribute to space weather study and its effects on space-based positioning system such as the GPS.

  8. EFFECT OF THE X5.4 CLASS SOLAR FLARE EVENT OF SOLAR CYCLE 24 ON THE GPS SIGNAL RECEPTION IN PENINSULAR MALAYSIA

    Directory of Open Access Journals (Sweden)

    S. Ismail

    2016-09-01

    Full Text Available In this paper, we examine the effect of solar flare event on the Global Positioning System (GPS signal reception in Peninsular Malaysia during the X5.4 class solar flare on 7th March 2012, 00:24 UT at active region AR1429. GPS data from six MyRTKnet stations that cover the northern, southern, western and eastern regions of Peninsular Malaysia were used, namely Langkawi (Kedah, Bandar Baharu (Pulau Pinang, Pekan (Pahang, Mersing (Johor, Tanjung Pengelih (Johor and Malacca (Malacca. The total electron content (TEC was estimated based on the single layer ionospheric model. Next, the ionospheric delay for each GPS frequency of L1 (1575.42 MHz, L2 (1227.60 MHz and L5 (1176.45 MHz was then calculated. The results show that solar flare event can influence the GPS signal reception in Peninsular Malaysia where the X5.4 class solar flare shows significant effect of the ionospheric delay within the range of 9 m – 20 m. These research findings will significantly contribute to space weather study and its effects on space-based positioning system such as the GPS.

  9. SynTec Final Technical Report: Synthetic biology for Tailored Enzyme cocktails

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Janine [Novozymes, Inc., Davis, CA (United States); Teter, Sarah [Novozymes, Inc., Davis, CA (United States)

    2016-06-30

    Using a novel enzyme screening method inspired by synthetic biology, Novozymes developed new technology under SynTec which allows for more rapidly tailoring of enzyme cocktails. The methodology can be applied to specific feedstocks, and or coupled to address a specific hydrolytic conversion process context. Using combinatorial high throughput screening of libraries of enzyme domains, we can quickly assess which combination of catalytic modules delivers the best performance for a specific condition. To demonstrate the effectiveness of the screening process, we measured performance of the output catalytic cocktail compared to CTec3/HTec3. SynTec benchmark cocktail - blend of Cellic® CTec3 and HTec3. The test substrate was - ammonia fiber expansion pretreated corn stover (AFEX™ PCS).CTec3/HTec3 was assayed at the optimal pH and temperature, and also in the absence of any pH adjustment. The new enzyme cocktail discovered under SynTec was assayed in the absence of any pH adjustment and at the optimal temperature. Conversion is delivered by SynTec enzyme at significant dose reduction relative to CTec3/HTec3 at the controlled pH optimum, and without titrant required to maintain pH, which delivers additional cost savings relative to current state of the art process. In this 2.5 year $4M project, the team delivered an experimental cocktail that significantly outperformed CTec3/HTec3 for a specific substrate, and for specific hydrolysis conditions. As a means of comparing performance improvement delivered per research dollar spent, we note that SynTec delivered a similar performance improvement to the previous award, in a shorter time and with fewer resources than for the previously successful DOE project DECREASE, a 3.5 year, $25M project, though this project focused on a different substrate and used different hydrolysis conditions. The newly implemented technology for rapid sourcing of new cellulases and hemicellulases from nature is an example of Novozymes

  10. Comparative analysis of spread-F signature and GPS scintillation occurrences at Tucumán, Argentina

    Science.gov (United States)

    Spogli, L.; Lucilla, A.; Pezzopane, M.; Romano, V.; Zuccheretti, E.; De Franceschi, G.; Cabrera, M.; Ezquer, R. G.

    2013-12-01

    A deep understanding of the temporal and spatial evolution of the ionosphere can be achieved by using a multi-instrument approach which provides complementary information. Bearing this in mind, we analyze data recorded from October 2010 to September 2011, during the ascending phase of the 24th solar cycle, from an Advanced Ionospheric Sounder-Istituto Nazionale di Geofisica e Vulcanologia ionosonde and a GPS Ionospheric Scintillation and Total Electron Content (TEC) monitor receiver, located in the same site at low latitude in the Southern American longitudinal sector (Tucumán, 26.9°S, 294.6°E, magnetic latitude 15.5°S, Argentina). Such site offers the opportunity to perform combined spread-F and GPS scintillation statistics of occurrence under the southern crest of the equatorial ionospheric anomaly. Spread-F signatures, classified into four types (strong range spread-F (SSF), range spread-F, frequency spread-F (FSF), and mixed spread-F), the phase and amplitude scintillation index (σΦ and S4, respectively), the TEC, and the rate of TEC parameter, marker of the TEC gradients, that can cause scintillation, are considered. The seasonal behavior results as follows: the occurrence of all four types of spread-F is higher in summer and lower in winter, while the occurrence of scintillation peaks at equinoxes in the postsunset sector and shows a minimum in winter. The correspondence between SSF and scintillation seems to be systematic, and a possible correlation between S4 and FSF peaks is envisaged at the terminator. Evidence that scintillation, unlike ESF, is recorded all-day long, allows to speculate also on the relationship between the features of the sporadic E irregularities and scintillation patterns. Our results indicate that the daytime amplitude scintillation is in correspondence with the appearance of a dense Es layer, with critical frequency above 4 MHz. The investigation focused also on two particular periods, from 12 to 16 March 2011 and from 23 to 29

  11. Observational study of ionospheric irregularities and GPS scintillations associated with the 2012 tropical cyclone Tembin passing Hong Kong

    Science.gov (United States)

    Yang, Zhe; Liu, Zhizhao

    2016-05-01

    This study presents the ionospheric responses observed in Hong Kong to a Typhoon, namely, Tembin, from the aspects of the occurrence of ionospheric irregularities and scintillations, using Global Positioning System (GPS) observations from a ground-based GPS scintillation monitoring station in Hong Kong and from GPS receivers on board the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. The ionospheric irregularities and scintillations are characterized by the rate of total electron content variation index (ROTI) and the amplitude scintillation index S4, respectively. The typhoon Tembin formed over the western North Pacific during 18-30 August 2012 and approached Hong Kong during 24-27 August 2012 with the closest distance 290 km from Hong Kong at around 17 universal time (UT) on 25 August 2012. The ground-based observations indicate that in the nighttime period of 20:00-02:00 local time (LT = UT + 8 h) on 26 August when Tembin passed closely to Hong Kong, the ionospheric irregularities and scintillations of GPS signals were observed in the south of Hong Kong, over the area of 13°N ~ 23°N in latitude and 110°E ~ 120°E in longitude. From the COSMIC observations, it shows that the number of radio occultation scintillation events peaks on 26 August 2012 during the passage of Tembin. Without the presence of strong geomagnetic or solar activity, it is suspected that gravity waves might be generated in the lower atmosphere and likely seed the formation of ionospheric plasma irregularities. This work for the first time from Hong Kong observes the sign of coupling between the lower atmosphere and ionosphere in a tropical cyclone event, combining both ground- and space-based GPS observation data.

  12. Validation of integrated water vapor from OMI satellite instrument against reference GPS data at the Iberian Peninsula.

    Science.gov (United States)

    Vaquero-Martínez, Javier; Antón, Manuel; Ortiz de Galisteo, José Pablo; Cachorro, Victoria E; Wang, Huiqun; González Abad, Gonzalo; Román, Roberto; Costa, Maria João

    2017-02-15

    This paper shows the validation of integrated water vapor (IWV) measurements retrieved from the Ozone Monitoring Instrument (OMI), using as reference nine ground-based GPS stations in the Iberian Peninsula. The study period covers from 2007 to 2009. The influence of two factors, - solar zenith angle (SZA) and IWV -, on OMI-GPS differences was studied in detail, as well as the seasonal dependence. The pseudomedian of the relative differences is -1 ± 1% and the inter-quartile range (IQR) is 41%. Linear regressions calculated over each station show an acceptable agreement (R(2) up to 0.77). The OMI-GPS differences display a clear dependence on IWV values. Hence, OMI substantially overestimates the lower IWV data recorded by GPS (∼ 40%), while underestimates the higher IWV reference values (∼ 20%). In connection to this IWV dependence, the relative differences also show an evident SZA dependence when the whole range of IWV values are analyzed (OMI overestimates for high SZA values while underestimates for low values). Finally, the seasonal variation of the OMI-GPS differences is also associated with the strong IWV dependence found in this validation exercise. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Kepler and Ground-Based Transits of the exo-Neptune HAT-P-11b

    Science.gov (United States)

    Deming, Drake; Sada, Pedro V.; Jackson, Brian; Peterson, Steven W.; Agol, Eric; Knutson, Heather A.; Jennings, Donald E.; Haase, Plynn; Bays, Kevin

    2011-01-01

    We analyze 26 archival Kepler transits of the exo-Neptune HAT-P-11b, supplemented by ground-based transits observed in the blue (B band) and near-IR (J band). Both the planet and host star are smaller than previously believed; our analysis yields Rp = 4.31 R xor 0.06 R xor and Rs = 0.683 R solar mass 0.009 R solar mass, both about 3 sigma smaller than the discovery values. Our ground-based transit data at wavelengths bracketing the Kepler bandpass serve to check the wavelength dependence of stellar limb darkening, and the J-band transit provides a precise and independent constraint on the transit duration. Both the limb darkening and transit duration from our ground-based data are consistent with the new Kepler values for the system parameters. Our smaller radius for the planet implies that its gaseous envelope can be less extensive than previously believed, being very similar to the H-He envelope of GJ 436b and Kepler-4b. HAT-P-11 is an active star, and signatures of star spot crossings are ubiquitous in the Kepler transit data. We develop and apply a methodology to correct the planetary radius for the presence of both crossed and uncrossed star spots. Star spot crossings are concentrated at phases 0.002 and +0.006. This is consistent with inferences from Rossiter-McLaughlin measurements that the planet transits nearly perpendicular to the stellar equator. We identify the dominant phases of star spot crossings with active latitudes on the star, and infer that the stellar rotational pole is inclined at about 12 deg 5 deg to the plane of the sky. We point out that precise transit measurements over long durations could in principle allow us to construct a stellar Butterfly diagram to probe the cyclic evolution of magnetic activity on this active K-dwarf star.

  14. Toward High Altitude Airship Ground-Based Boresight Calibration of Hyperspectral Pushbroom Imaging Sensors

    Directory of Open Access Journals (Sweden)

    Aiwu Zhang

    2015-12-01

    Full Text Available The complexity of the single linear hyperspectral pushbroom imaging based on a high altitude airship (HAA without a three-axis stabilized platform is much more than that based on the spaceborne and airborne. Due to the effects of air pressure, temperature and airflow, the large pitch and roll angles tend to appear frequently that create pushbroom images highly characterized with severe geometric distortions. Thus, the in-flight calibration procedure is not appropriate to apply to the single linear pushbroom sensors on HAA having no three-axis stabilized platform. In order to address this problem, a new ground-based boresight calibration method is proposed. Firstly, a coordinate’s transformation model is developed for direct georeferencing (DG of the linear imaging sensor, and then the linear error equation is derived from it by using the Taylor expansion formula. Secondly, the boresight misalignments are worked out by using iterative least squares method with few ground control points (GCPs and ground-based side-scanning experiments. The proposed method is demonstrated by three sets of experiments: (i the stability and reliability of the method is verified through simulation-based experiments; (ii the boresight calibration is performed using ground-based experiments; and (iii the validation is done by applying on the orthorectification of the real hyperspectral pushbroom images from a HAA Earth observation payload system developed by our research team—“LanTianHao”. The test results show that the proposed boresight calibration approach significantly improves the quality of georeferencing by reducing the geometric distortions caused by boresight misalignments to the minimum level.

  15. Estimation of Antarctic ozone loss from Ground-based total column measurements

    Directory of Open Access Journals (Sweden)

    J. Kuttippurath

    2010-03-01

    Full Text Available The passive ozone method is used to estimate ozone loss from ground-based measurements in the Antarctic. A sensitivity study shows that the O3 loss can be estimated within an accuracy of ~4%. The method is then applied to the observations from Amundsen-Scott/South Pole, Arrival Heights, Belgrano, Concordia, Dumont d'Urville, Faraday, Halley, Marambio, Neumayer, Rothera, Syowa and Zhongshan for the diagnosis of ozone loss in the Antarctic. On average, the five-day running mean of the vortex averaged ozone column loss deduced from the ground-based stations shows about 53% in 2009, 59% in 2008, 55% in 2007, 56% in 2006 and 61% in 2005. The observed O3 loss and loss rates are in very good agreement with the satellite observations (Ozone Monitoring Instrument and Sciamachy and are well reproduced by the model (Reprobus and SLIMCAT calculations.

    The historical ground-based total ozone measurements show that the depletion started in the late 1970s, reached a maximum in the early 1990s, stabilising afterwards at this level until present, with the exception of 2002, the year of an early vortex break-up. There is no indication of significant recovery yet.

    At southern mid-latitudes, a total ozone reduction of 40–50% is observed at the newly installed station Rio Gallegos and 25–35% at Kerguelen in October–November of 2008–2009 and 2005–2009 (except 2008 respectively, and of 10–20% at Macquarie Island in July–August of 2006–2009. This illustrates the significance of measurements at the edges of Antarctica.

  16. Comparison of OMI UV observations with ground-based measurements at high northern latitudes

    Directory of Open Access Journals (Sweden)

    G. Bernhard

    2015-03-01

    Full Text Available The Dutch-Finnish Ozone Monitoring Instrument (OMI on board NASA's Aura spacecraft provides estimates of erythemal (sunburning ultraviolet (UV dose rates and erythemal daily doses. These data were compared with ground-based measurements at 13 stations located throughout the Arctic and Scandinavia from 60 to 83° N. The study corroborates results from earlier work, but is based on a longer time series (eight vs. two years and considers additional data products, such as the erythemal dose rate at the time of the satellite overpass. Furthermore, systematic errors in satellite UV data resulting from inaccuracies in the surface albedo climatology used in the OMI UV algorithm are systematically assessed. At times when the surface albedo is correctly known, OMI data typically exceed ground-based measurements by 0–11%. When the OMI albedo climatology exceeds the actual albedo, OMI data may be biased high by as much as 55%. In turn, when the OMI albedo climatology is too low, OMI data can be biased low by up to 59%. Such large negative biases may occur when reflections from snow and ice, which increase downwelling UV irradiance, are misinterpreted as reflections from clouds, which decrease the UV flux at the surface. Results suggest that a better OMI albedo climatology would greatly improve the accuracy of OMI UV data products even if year-to-year differences of the actual albedo cannot be accounted for. A pathway for improving the OMI albedo climatology is discussed. Results also demonstrate that ground-based measurements from the center of Greenland, where high, homogenous surface albedo is observed year round, are ideally suited to detect systematic problems or temporal drifts in estimates of surface UV irradiance from space.

  17. Ground-based microwave measuring of middle atmosphere ozone and temperature profiles during sudden stratospheric warming

    Science.gov (United States)

    Feigin, A. M.; Shvetsov, A. A.; Krasilnikov, A. A.; Kulikov, M. Y.; Karashtin, D. A.; Mukhin, D.; Bolshakov, O. S.; Fedoseev, L. I.; Ryskin, V. G.; Belikovich, M. V.; Kukin, L. M.

    2012-12-01

    We carried out the experimental campaign aimed to study the response of middle atmosphere on a sudden stratospheric warming in winter 2011-2012 above Nizhny Novgorod, Russia (56N, 44E). We employed the ground-based microwave complex for remote sensing of middle atmosphere developed in the Institute of Applied Physics of the Russian Academy of Science. The complex combines two room-temperature radiometers, i.e. microwave ozonometer and the stratospheric thermometer. Ozonometer is a heterodyne spectroradiometer, operating in a range of frequencies that include the rotation transition of ozone molecules with resonance frequency 110.8 GHz. Operating frequency range of the stratospheric thermometer is 52.5-5.4 GHz and includes lower frequency edge of 5 mm molecular oxygen absorption bands and among them two relatively weak lines of O2 emission. Digital fast Fourier transform spectrometers developed by "Acqiris" are employed for signal spectral analysis. The spectrometers have frequency range 0.05-1 GHz and realizes the effective resolution about 61 KHz. For retrieval vertical profiles of ozone and temperature from radiometric data we applied novel method based on Bayesian approach to inverse problem solution, which assumed a construction of probability distribution of the characteristics of retrieved profiles with taking into account measurement noise and available a priori information about possible distributions of ozone and temperature in the middle atmosphere. Here we introduce the results of the campaign in comparison with Aura MLS data. Presented data includes one sudden stratospheric warming event which took place in January 13-14 and was accompanied by temperature increasing up to 310 K at 45 km height. During measurement period, ozone and temperature variations were (almost) anti-correlated, and total ozone abundance achieved a local maxima during the stratosphere cooling phase. In general, results of ground-based measurements are in good agreement with

  18. Ground-Based Network and Supersite Observations to Complement and Enrich EOS Research

    Science.gov (United States)

    Tsay, Si-Chee; Holben, Brent N.; Welton, Ellsworth J.

    2011-01-01

    Since 1997 NASA has been successfully launching a series of satellites - the Earth Observing System (EOS) - to intensively study, and gain a better understanding of, the Earth as an integrated system. Space-borne remote sensing observations, however, are often plagued by contamination of surface signatures. Thus, ground-based in-situ and remote-sensing measurements, where signals come directly from atmospheric constituents, the sun, and/or the Earth-atmosphere interactions, provide additional information content for comparisons that confirm quantitatively the usefulness of the integrated surface, aircraft, and satellite datasets. Through numerous participations, particularly but not limited to the EOS remote-sensing/retrieval and validation projects over the years, NASA/GSFC has developed and continuously refined ground-based networks and mobile observatories that proved to be vital in providing high temporal measurements, which complement and enrich the satellite observations. These are: the AERO NET (AErosol RObotic NETwork) a federation of ground-based globally distributed network of spectral sun-sky photometers; the MPLNET (Micro-Pulse Lidar NETwork, a similarly organized network of micro-pulse lidar systems measuring aerosol and cloud vertical structure continuously; and the SMART-COMMIT (Surface-sensing Measurements for Atmospheric Radiative Transfer - Chemical, Optical & Microphysical Measurements of In-situ Troposphere, mobile observatories, a suite of spectral radiometers and in-situ probes acquiring supersite measurements. Most MPLNET sites are collocated with those of AERONET, and both networks always support the deployment of SMART-COMMIT worldwide. These data products follow the data structure of EOS conventions: Level-0, instrument archived raw data; Level-1 (or 1.5), real-time data with no (or limited) quality assurance; Level-2, not real high temporal and spectral resolutions. In this talk, we will present NASA/GSFC groundbased facilities, serving

  19. Ground-based SMART-COMMIT Measurements for Studying Aerosol and Cloud Properties

    Science.gov (United States)

    Tsay, Si-Chee

    2008-01-01

    From radiometric principles, it is expected that the retrieved properties of extensive aerosols and clouds from reflected/emitted measurements by satellite (and/or aircraft) should be consistent with those retrieved from transmitted/emitted radiance observed at the surface. Although space-borne remote sensing observations cover large spatial domain, they are often plagued by contamination of surface signatures. Thus, ground-based in-situ and remote-sensing measurements, where signals come directly from atmospheric constituents, the sun, and/or the Earth-atmosphere interactions, provide additional information content for comparisons that confirm quantitatively the usefulness of the integrated surface, aircraft, and satellite data sets. The development and deployment of SMARTCOMMIT (Surface-sensing Measurements for Atmospheric Radiative Transfer - Chemical, Optical & Microphysical Measurements of In-situ Troposphere) mobile facilities are aimed for the optimal utilization of collocated ground-based observations as constraints to yield higher fidelity satellite retrievals and to determine any sampling bias due to target conditions. To quantify the energetics of the surface-atmosphere system and the atmospheric processes, SMART-COMMIT instruments fall into three categories: flux radiometer, radiance sensor and in-situ probe. In this paper, we will demonstrate the capability of SMART-COMMIT in recent field campaigns (e.g., CRYSTAL-FACE, UAE 2, BASEASIA, NAMMA) that were designed and executed to study the compelling variability in temporal scale of both anthropogenic and natural aerosols (e.g., biomass-burning smoke, airborne dust) and cirrus clouds. We envision robust approaches in which well-collocated ground-based measurements and space-borne observations will greatly advance our knowledge of extensive aerosols and clouds.

  20. INDOOR LOCALIZATION SOLUTION FOR GPS

    OpenAIRE

    Shreyanka B. Chougule; Dr.Sayed Abdulhayan

    2017-01-01

    GPS technology is used for positioning application and it is highly reliable and accurate when used outdoor. Due to multipath propagation, signal attenuation and blockage its performance is limited in indoor and dense urban environment. As a solution, technologies like Apple’s iBeacon, Radio-frequency identification (RFID), Ultrasonic and Wireless Fidelity (Wi-Fi) access points are used to improve performance in Indoor environment. We are having a look at all these technologies which are mean...

  1. Ground-based measurements of aerosol optical properties and radiative forcing in North China

    Institute of Scientific and Technical Information of China (English)

    Hongbin Chen; Xiangao Xia; Pucai Wang; Wenxing Zhang

    2007-01-01

    In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network (AERONET) sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data.Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers.

  2. Estimation of above ground biomass in boreal forest using ground-based Lidar

    Science.gov (United States)

    Taheriazad, L.; Moghadas, H.; Sanchez-Azofeifa, A.

    2017-05-01

    Assessing above ground biomass of forest is important for carbon storage monitoring in boreal forest. In this study, a new model is developed to estimate the above ground biomass using ground based Lidar data. 21 trees were measured and scanned across the plot area study in boreal forests of Alberta, Canada. The study area was scanned in the summer season 2014 to quantify the green biomass. The average of total crown biomass and green biomass in this study was 377 kg (standard deviation, S.D. = 243 kg) and 6.42 kg (S.D. = 2.69 m), respectively.

  3. Synergetic ground-based methods for remote measurements of ozone vertical profiles

    Science.gov (United States)

    Timofeyev, Yuriy; Kostsov, Vladimir; Virolainen, Yana

    2013-05-01

    The technique of combining ground-based measurements in infrared and microwave spectral regions in order to achieve higher accuracy of ozone profile retrieval in extensive altitude ranges is described and analyzed. The information content, errors, altitude ranges and vertical resolution of ozone profile retrieval have been studied on the basis of numerical simulation of synergetic experiments. Optimal conditions of measurements are defined and requirements to additional information are formulated. The first results on ozone vertical profile retrieval using groundbased measurements of FTIR-spectrometer and microwave radiometer are given.

  4. Solar diameter, eclipses and transits: the importance of ground-based observations

    CERN Document Server

    Sigismondi, Costantino

    2012-01-01

    According to satellite measurements the difference between polar and equatorial radius does not exceed 10 milliarcsec. These measurements are differential, and the absolute value of the solar diameter is not precisely known to a level of accuracy needed for finding variations during years or decades. Moreover the lifetime of a satellite is limited, and its calibration is not stable. This shows the need to continue ground-based observations of the Sun exploiting in particular the methods less affected by atmospheric turbulence, as the planetary transits and the total and annular eclipses. The state of art, the advantages and the limits of these two methods are here considered.

  5. Asteroseismology of Solar-type stars with Kepler III. Ground-based Data

    CERN Document Server

    Molenda-Zakowicz, Joanna; Sousa, Sergio; Frasca, Antonio; Biazzo, Katia; Huber, Daniel; Ireland, Mike; Bedding, Tim; Stello, Dennis; Uytterhoeven, Katrien; Dreizler, Stefan; De Cat, Peter; Briquet, Maryline; Catanzaro, Giovanni; Karoff, Chistoffer; Frandsen, Soeren; Spezzi, Loredana; Catala, Claude

    2010-01-01

    We report on the ground-based follow-up program of spectroscopic and photometric observations of solar-like asteroseismic targets for the Kepler space mission. These stars constitute a large group of more than thousand objects which are the subject of an intensive study of the Kepler Asteroseismic Science Consortium Working Group 1 (KASC WG-1). The main goal of this coordinated research is the determination of the fundamental stellar atmospheric parameters, which are used for the computing of their asteroseismic models, as well as for the verification of the Kepler Input Catalogue (KIC).

  6. Boost-Phase ballistic missile trajectory estimation with ground based radar

    Institute of Scientific and Technical Information of China (English)

    Tang Yuyan; Huang Peikang

    2006-01-01

    A conditional boost-phase trajectory estimation method based on ballistic missile (BM) information database and classification is developed to estimate and predict boos-phase BM trajectory. The main uncertain factors to describe BM dynamics equation are reduced to the control law of trajectory pitch angle in boost-phase. After the BM mass at the beginning of estimation, the BM attack angle and the modification of engine thrust denoting BM acceleration are modeled reasonably, the boost-phase BM trajectory estimation with ground based radar is well realized. The validity of this estimation method is testified by computer simulation with a typical example.

  7. Integrated interpretation of helicopter and ground-based geophysical data recorded within the Okavango Delta, Botswana

    DEFF Research Database (Denmark)

    Podgorski, Joel E.; Green, Alan G.; Kalscheuer, Thomas

    2015-01-01

    ) data recorded across most of the delta, (ii) 2D models and images derived from ground-based electrical resistance tomographic, transient electromagnetic, and high resolution seismic reflection/refraction tomographic data acquired at four selected sites in western and north-central regions of the delta...... resistivities and very low to low P-wave velocities. Except for images of several buried abandoned river channels, it is non-reflective. The laterally extensive underlying unit of low resistivities, low P-wave velocity, and subhorizontal reflectors very likely contains saline-water-saturated sands and clays...... reflectivity. The interface between the POM unit and basement is a prominent seismic reflector....

  8. Hypergravity Facilities in the ESA Ground-Based Facility Program - Current Research Activities and Future Tasks

    Science.gov (United States)

    Frett, Timo; Petrat, Guido; W. A. van Loon, Jack J.; Hemmersbach, Ruth; Anken, Ralf

    2016-06-01

    Research on Artificial Gravity (AG) created by linear acceleration or centrifugation has a long history and could significantly contribute to realize long-term human spaceflight in the future. Employing centrifuges plays a prominent role in human physiology and gravitational biology. This article gives a short review about the background of Artificial Gravity with respect to hypergravity (including partial gravity) and provides information about actual ESA ground-based facilities for research on a variety of biosystems such as cells, plants, animals or, particularly, humans.

  9. Images of Neptune's ring arcs obtained by a ground-based telescope

    Science.gov (United States)

    Sicardy, B.; Roddier, F.; Roddier, C.; Perozzi, E.; Graves, J. E.; Guyon, O.; Northcott, M. J.

    1999-08-01

    Neptune has a collection of incomplete narrow rings, known as ring arcs, which should in isolation be destroyed by differential motion in a matter of months. Yet since first discovered by stellar occultations in 1984, they appear to have persisted, perhaps through a gravitational resonance effect involving the satellite Galatea. Here we report ground-based observations of the ring arcs, obtained using an adaptive optics system. Our data, and those obtained using the Hubble Space Telescope (reported in a companion paper), indicate that the ring arcs are near, but not within the resonance with Galatea, in contrast to what is predicted by some models.

  10. SCENARIO AND TARGET SIMULATION FOR A GROUND BASED MULTIFUNCTION PHASED ARRAY RADAR

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper describes a scenario and target simulation which operates in non real-time to provide full closed-loop operation of the ground based multifunction phased array radar simulation system in support of ballistic missile defence experiments against countermeasure.By simulating the target scattering signature and dynamical signature,this scenario and target simulation provide re- alistic scenario source to evaluate the system performance of multifunction phased array radar,and the key algorithms verification and validation such as target tracking,multi-target imaging and target recognition.

  11. Improved ground-based FTS measurement for column abundance CO2 retrievals(Conference Presentation)

    Science.gov (United States)

    Goo, Tae-Young

    2016-10-01

    The National Institute of Meteorological Sciences has operated a ground-based Fourier Transform Spectrometer (FTS) at Anmyeondo, Korea since December 2012. Anmyeondo FTS site is a designated operational station of Total Carbon Column Observing Network (TCCON) and belongs to regional Global Atmosphere Watch observatory. A Bruker IFS-125HR model, which has a significantly high spectral resolution by 0.02 cm-1, is employed and instrument specification is almost same as the TCCON configuration. such as a spectrum range of 3,800 16,000 cm-1, a resolution of 1 cm-1, InGaAs and Si-Diode detectors and CaF2 beam splitter. It is found that measured spectra have a good agreement with simulated spectra. In order to improve the spectral accuracy and stability, The Operational Automatic System for Intensity of Sunray (OASIS) has been developed. The OASIS can provide consistent photon energy optimized to detector range by controlling the diameter of solar beam reflected from the mirror of suntracker. As a result, monthly modulation efficiency (ME), which indicates the spectral accuracy of FTS measurement, has been recorded the vicinity of 99.9% since Feb 2015. The ME of 98% is regarded as the error of 0.1% in the ground-based in-situ CO2 measurement. Total column abundances of CO2 and CH4 during 2015 are estimated by using GGG v14 and compared with ground-based in-situ CO2 and CH4 measurements at the height of 86 m above sea level. The seasonality of CO2 is well captured by both FTS and in-situ measurements while there is considerable difference on the amplitude of CO2 seasonal variation due to the insensitivity of column CO2 to the surface carbon cycle dynamics in nature as well as anthropogenic sources. Total column CO2 and CH4 approximately vary from 395 ppm to 405 ppm and from 1.82 ppm to 1.88 ppm, respectively. It should be noted that few measurements obtained in July to August because of a lot of cloud and fog. It is found that enhancement of CH4 from the FTS at Anmyeondo

  12. The laser calibration system for the STACEE ground-based gamma ray detector

    CERN Document Server

    Hanna, D

    2002-01-01

    We describe the design and performance of the laser system used for calibration monitoring of components of the STACEE detector. STACEE is a ground based gamma ray detector which uses the heliostats of a solar power facility to collect and focus Cherenkov light onto a system of secondary optics and photomultiplier tubes. To monitor the gain and check the linearity and timing properties of the phototubes and associated electronics, a system based on a dye laser, neutral density filters and optical fibres has been developed. In this paper we describe the system and present some results from initial tests made with it.

  13. Ground-Based Gas-Liquid Flow Research in Microgravity Conditions: State of Knowledge

    Science.gov (United States)

    McQuillen, J.; Colin, C.; Fabre, J.

    1999-01-01

    During the last decade, ground-based microgravity facilities have been utilized in order to obtain predictions for spacecraft system designers and further the fundamental understanding of two-phase flow. Although flow regime, pressure drop and heat transfer coefficient data has been obtained for straight tubes and a limited number of fittings, measurements of the void fraction, film thickness, wall shear stress, local velocity and void information are also required in order to develop general mechanistic models that can be utilized to ascertain the effects of fluid properties, tube geometry and acceleration levels. A review of this research is presented and includes both empirical data and mechanistic models of the flow behavior.

  14. Ground-based and spaceborn observations of the type II burst with developed fine structure

    Science.gov (United States)

    Dorovskyy, V.; Melnik, V.; Konovalenko, A.; Brazhenko, A.; Rucker, H.; Stanislavskyy, A.; Panchenko, M.

    2012-09-01

    The combination of two huge ground-based radio telescopes (UTR-2 and URAN-2) operated in decameter wavelengths with three spatially separated spacecrafts (SOHO, STEREO-A and STEREO-B) equipped with white light coronagraphs, UV telescopes and decameter-hectometer band radio telescopes created a unique opportunity to investigate the high energy solar transients, such as CMEs and their manifestations in radio bands - type II bursts. In this paper we made detailed analysis of the powerful and complex event occurred on 7 June 2011 consisted of Halo-CME and type II burst with rich fine structure.

  15. Advanced ground-based gravitational-wave detectors' potential to detect generic deviations from general relativity

    CERN Document Server

    Narikawa, Tatsuya

    2016-01-01

    We discuss the potential of the advanced ground-based gravitational-wave detectors, such as LIGO, Virgo, and KAGRA, to detect generic deviations of gravitational waveforms from the prediction of General Relativity. We use the parameterized post-Einsteinian formalism to characterize the deviations, and assess how much magnitude of the deviations are detectable by using an approximate decision scheme based on Bayesian statistics. We find that there exist detectable regions of the parameterized post-Einsteinian parameters by using a single gravitational wave event. The regions are not excluded by currently existing binary pulsar observations for the parameterized post-Einsteinian parameters at higher post-Newtonian order.

  16. Ionospheric Scintillation Effects on GPS

    Science.gov (United States)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  17. GPS-Aided Video Tracking

    Directory of Open Access Journals (Sweden)

    Udo Feuerhake

    2015-08-01

    Full Text Available Tracking moving objects is both challenging and important for a large variety of applications. Different technologies based on the global positioning system (GPS and video or radio data are used to obtain the trajectories of the observed objects. However, in some use cases, they fail to provide sufficiently accurate, complete and correct data at the same time. In this work we present an approach for fusing GPS- and video-based tracking in order to exploit their individual advantages. In this way we aim to combine the reliability of GPS tracking with the high geometric accuracy of camera detection. For the fusion of the movement data provided by the different devices we use a hidden Markov model (HMM formulation and the Viterbi algorithm to extract the most probable trajectories. In three experiments, we show that our approach is able to deal with challenging situations like occlusions or objects which are temporarily outside the monitored area. The results show the desired increase in terms of accuracy, completeness and correctness.

  18. Applications of GPS technologies to field sports.

    Science.gov (United States)

    Aughey, Robert J

    2011-09-01

    Global positioning system (GPS) technology was made possible after the invention of the atomic clock. The first suggestion that GPS could be used to assess the physical activity of humans followed some 40 y later. There was a rapid uptake of GPS technology, with the literature concentrating on validation studies and the measurement of steady-state movement. The first attempts were made to validate GPS for field sport applications in 2006. While GPS has been validated for applications for team sports, some doubts continue to exist on the appropriateness of GPS for measuring short high-velocity movements. Thus, GPS has been applied extensively in Australian football, cricket, hockey, rugby union and league, and soccer. There is extensive information on the activity profile of athletes from field sports in the literature stemming from GPS, and this includes total distance covered by players and distance in velocity bands. Global positioning systems have also been applied to detect fatigue in matches, identify periods of most intense play, different activity profiles by position, competition level, and sport. More recent research has integrated GPS data with the physical capacity or fitness test score of athletes, game-specific tasks, or tactical or strategic information. The future of GPS analysis will involve further miniaturization of devices, longer battery life, and integration of other inertial sensor data to more effectively quantify the effort of athletes.