Radiometric Calibration of the Advanced Wind Scatterometer Radar ASCAT Carried Onboard the METOP-A Satellite

Wilson, J. J. W.; Anderson, Craig; Baker, M.; Bonekamp, Hans; Saldana, Julia Figa; Dyer, Richard; Lerch, J A; Kayal, G; Gelsthorpe, R. V.; Brown, Michael; Schied, Eberhard; Schutz-Munz, S; Rostan, F.; Pritchard, E W; Wright, Nick; King, David B.; Onel, Ü

doi:10.1109/tgrs.2010.2045763

Cited by 46 publications

(22 citation statements)

References 2 publications

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“…Main mission events such as the gyroscope failure of ERS-2 ESCAT in 2001 (Crapolicchio et al, 2012) or the regular calibration campaigns performed for ASCAT (Wilson et al, 2010) may affect the overall long-term instrument stability. Radiometric instabilities of the instrument will affect the TUWien soil moisture retrieval by degrading the parameter estimation precision.…”

Section: Instrument Stability Of Escat and Ascatmentioning

confidence: 99%

Long-term Soil Moisture Time Series Analyses based on Active Microwave Backscatter Measurements

Wagner

Reimer

Bauer-Marschallinger

et al. 2015

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Active microwave sensors operating at lower microwave frequencies in the range from 1 to 10 GHz provide backscatter measurements that are sensitive to the moisture content of the soil. Thanks to a series of European C-band (5.3 GHz) scatterometers, which were first flown on board of the European Remote Sensing satellites ERS-1 and ERS-2, and later on board of MetOp-A and MetOp -B, we are now in the possession of a long-term soil moisture time series starting in 1991. The creation of globally consistent long-term soil moisture time series is a challenging task. The TU-Wien soil moisture algorithm is adopted to tackle these challenges. In this paper we present two methodologies that were developed to ensure radiometric stability of the European C-band scatterometers. The objective of sensor intra-calibration is to monitor and correct for radiometric instabilities within one scatterometer mission, while sensor inter-calibration aims to remove radiometric differences across several missions. In addition, a novel vegetation modelling approach is presented that enables the estimation of vegetation parameters for each day across several years to account for yearly to longer-term changes in vegetation phenology and land cover.

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Section: Instrument Stability Of Escat and Ascatmentioning

confidence: 99%

Long-term Soil Moisture Time Series Analyses based on Active Microwave Backscatter Measurements

Wagner

Reimer

Bauer-Marschallinger

et al. 2015

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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“…With the development of GPS meteorology, the space-based GPS radio occultation is regarded as a valuable tool for atmospheric change studies (Rocken et al, 1997;Kursinski et al, 1997;Hajj et al, 2002;. Since the GPS/MET (Global Positioning System/Meteorology) mission has conducted a number of successful measurement experiments from 1995 to 1997 (Ware, 1996;Rocken et al, 1997), some low Earthorbiting (LEO) satellites, such as CHAMP, GRACE, COS-MIC (The Constellation Observing System for Meteorology, Ionosphere and Climate) and MetOp-A (Wickert et al, 2001(Wickert et al, , 2005Rocken et al, 2000;Wilson et al, 2010) have begun to equip RO instruments to facilitate the development of the RO technique. In the GPS occultation technique, the atmospheric refractivity is an important quality in numerical weather prediction (Esteban et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Estimation and evaluation of COSMIC radio occultation excess phase using undifferenced measurements

Xia

Jiang

et al. 2017

Atmos. Meas. Tech.

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Abstract. In the GPS radio occultation technique, the atmospheric excess phase (AEP) can be used to derive the refractivity, which is an important quantity in numerical weather prediction. The AEP is conventionally estimated based on GPS double-difference or single-difference techniques. These two techniques, however, rely on the reference data in the data processing, increasing the complexity of computation. In this study, an undifferenced (ND) processing strategy is proposed to estimate the AEP. To begin with, we use PANDA (Positioning and Navigation Data Analyst) software to perform the precise orbit determination (POD) for the purpose of acquiring the position and velocity of the mass centre of the COSMIC (The Constellation Observing System for Meteorology, Ionosphere and Climate) satellites and the corresponding receiver clock offset. The bending angles, refractivity and dry temperature profiles are derived from the estimated AEP using Radio Occultation Processing Package (ROPP) software. The ND method is validated by the COSMIC products in typical rising and setting occultation events. Results indicate that rms (root mean square) errors of relative refractivity differences between undifferenced and atmospheric profiles (atmPrf) provided by UCAR/CDAAC (University Corporation for Atmospheric Research/COSMIC Data Analysis and Archive Centre) are better than 4 and 3 % in rising and setting occultation events respectively. In addition, we also compare the relative refractivity bias between ND-derived methods and atmPrf profiles of globally distributed 200 COSMIC occultation events on 12 December 2013. The statistical results indicate that the average rms relative refractivity deviation between ND-derived and COSMIC profiles is better than 2 % in the rising occultation event and better than 1.7 % in the setting occultation event. Moreover, the observed COSMIC refractivity profiles from ND processing strategy are further validated using European Centre for Medium-Range Weather Forecasts (ECMWF) analysis data, and the results indicate that the undifferenced method reduces the noise level on the excess phase paths in the lower troposphere compared to the single-difference processing strategy.

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“…Generally, three kinds of approaches can be adopted for scatterometers in-orbit calibration to get an accurate gain pattern: employing 1) active/passive calibration ground stations (CGSs) [7]- [9]; 2) homogeneous land targets [10]- [12]; and 3) ocean calibration method [4], [13]. Among them, active CGSs, i.e., transponders, provide very accurately known point target cross sections and have been used by AMI, ASCAT, and NSCAT [7], [9].…”

Section: Introductionmentioning

confidence: 99%

Calibration and Estimation of Attitude Errors for a Rotating Fan-Beam Scatterometer Using Calibration Ground Stations

Zhu

Dong

Lin

et al. 2015

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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The rotating fan-beam scatterometer (RFSCAT) onboard Chinese-French Oceanic SATellite (CFOSAT) due to launch in 2018 is a new type of radar scatterometer system for ocean surface wind vector measurement. It can give observations with more azimuth and incidence angles for a single wind vector cell (WVC) than other available scatterometers. This has been proved effective in bettering the retrieved wind quality by the simulation approach. However, its innovative observing geometry is challenging for the coming in-orbit external calibration. In this paper, CFOSAT attitude errors are estimated, and its antenna gain pattern is monitored and verified based on the external calibration strategy of a Ku-band scatterometer employing calibration ground stations (CGSs). The effects of satellite attitude errors on the measurements are also analyzed, together with simulation results for the external calibration. It is shown that a gain pattern with accuracy of 0.08 dB and attitude errors within 0.025 are achieved.

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Radiometric Calibration of the Advanced Wind Scatterometer Radar ASCAT Carried Onboard the METOP-A Satellite

Cited by 46 publications

References 2 publications

Long-term Soil Moisture Time Series Analyses based on Active Microwave Backscatter Measurements

Long-term Soil Moisture Time Series Analyses based on Active Microwave Backscatter Measurements

Estimation and evaluation of COSMIC radio occultation excess phase using undifferenced measurements

Calibration and Estimation of Attitude Errors for a Rotating Fan-Beam Scatterometer Using Calibration Ground Stations

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