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Title: EVALUATION OF OCEANSAT-1 MULTI-FREQUENCY SCANNING MICROWAVE RADIOMETER AND ITS POTENTIAL FOR SOIL MOISTURE RETRIEVAL

Author
item WEN, J. - WAGENIGEN UNIV.
item Jackson, Thomas
item BINDLISH, R. - SSAI
item SU, Z. - WAGENIGEN UNIV.

Submitted to: International Journal of Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2005
Publication Date: 9/20/2006
Citation: Wen, J., Jackson, T.J., Bindlish, R., Su, Z. 2006. Evaluation of OCEANSAT-1 multi-frequency scanning microwave radiometer and its potential for soil moisture retrieval. International Journal of Remote Sensing. 27:3781-3796.

Interpretive Summary: The potential for soil moisture retrieval using the Multi-frequency Scanning Microwave Radiometer (MSMR) on the Indian Space Research Organization - Oceansat-1 satellite using a previously developed algorithm was evaluated. The MSMR was a dual-polarized passive microwave sensor measuring at four frequencies and collected datafor a two years period from 1999 to 2001. This investigation was one of the first to utilize the MSMR data for a land application, and as a result, several data quality issues had to be addressed. Calibration of the low frequency channels was evaluated using inter-comparisons between the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) and the MSMR brightness temperatures and results suggested that additional calibration of the MSMR data was required. Comparisons between the MSMR measured brightness temperature and ground measured volumetric soil moisture collected during the South Great Plain experiment (SGP99) indicated that the lower frequency and horizontal polarization observations had higher sensitivity to soil moisture. Using the previously developed soil emission model, multi-temporal regional soil moisture distributions were retrieved for the continental United States. MSMR was the only satellite based C-band passive microwave system that collected data during the period between the Scanning Multichannel Microwave Radiometer (SMMR) that operated between 1978-1987 and AMSR-E launched in 2002. Establishing long term records of satellite microwave brightness temperature and derived soil moisture is of value in understanding and monitoring changes in climate and in particular the water cycle.

Technical Abstract: The Multi-frequency Scanning Microwave Radiometer (MSMR) aboard the Indian Space Research Organization - Oceansat-1 platform measured land surface brightness temperature at C-band frequencies and provided an opportunity for exploring large-scale soil moisture retrieval during its two-year period of operation. These data may provide a valuable extension to the Scanning Multichannel Microwave Radiometer (SMMR) and the Advanced Microwave Scanning Radiometer (AMSR) since they covered a portion of the time period between the two missions. This investigation was one of the first to utilize the MSMR data for a land application, and as a result, several data quality issues had to be addressed. These included geolocation accuracy, calibration (particularly over land), erroneous data, and the significance of anthropogenic Radio-Frequency Interference (RFI). Calibration of the low frequency channels was evaluated using inter-comparisons between the Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI) and the MSMR brightness temperatures. Biases (TMI TB > MSMR TB) of 3.4 and 3.6 K were observed over land for the MSMR 10.65 GHz horizontal and vertical polarization channels respectively. These results suggested that additional calibration of the MSMR data was required. Comparisons between the MSMR measured brightness temperature and ground measured volumetric soil moisture collected during the South Great Plain experiment (SGP99) indicated that the lower frequency and horizontal polarization observations had higher sensitivity to soil moisture. Using a previously developed soil emission model, multi-temporal regional soil moisture distributions were retrieved for the continental United States. Comparisons between the MSMR based soil moisture and ground measured volumetric soil moisture indicated a standard error of estimate of 0.052 m3/m3.