Frequency dependence of brightness temperature ( T B ) in the range 6–21 GHz is studied as a function of surface roughness, vegetation cover and soil moisture using theoretical models. Frequency dependence of T B is plotted from Multi-channel Scanning Microwave Radiometer (MSMR) T B data of Indian Remote Sensing Satellite (P-series) IRS-P4 for different target types such as ocean, desert, forest, agricultural and snow regions. MSMR responds to the variations of the target parameters; however, it is noticed that the T B data at 18 GHz deviate from the theoretically predicted trend. The effect of atmosphere (water vapour) is taken into account in the theoretical trend. However, the frequency dependence of T B plots from Scanning Multi-channel Microwave Radiometer (SMMR) of Nimbus-7 closely resemble the theoretical trend. This indicates that the relative calibration of 18 GHz T B of IRS-P4 has some problem and needs to be looked into. Approximate offset values for each land type are computed and presented here. A general comparison of T B of MSMR and SMMR indicates that T B of MSMR is higher by 4 K, which needs to be further investigated.
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Document Type: Research Article
Physics Department, Kuwait University, P.O. Box 5969, Safat 13060, State of Kuwait
Centre of Studies in Resources Engineering, Indian Institute of Technology – Bombay, Powai, Mumbai 400076, India
Publication date: 2006-01-20
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