A Note on the Quality of Brightness Temperature Data of MSMR Onboard IRS-P4 Satellite

摘要

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 at 18 GHz deviates from the theoretically predicted trends. The effect, of atmosphere (water vapour) is taken into account in the theoretical trends. However, the frequency dependence of T_B plots from Scanning Multi-channel Microwave Radiometer (SMMR) of Nimbus - 7 satellite closely resembles the theoretical trends. 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.