Advanced Microwave Atmospheric Sounder (AMAS) Channel Specifications and T/V Calibration Results on FY-3C Satellite

The Advanced Microwave Atmospheric Sounder (AMAS) is the new generation of Microwave Humidity Sounder (MWHS) onboard the Feng Yun 3 C/D (FY-3C/D) satellite and follows the heritage and development of MWHS onboard the FY-3(A/B) satellite. AMAS onboard the FY-3C satellite is a 15-channel total power microwave radiometer in the range of 89-191 GHz scheduled to be launched on September 23, 2013. Compared to MWHS onboard FY-3A/B, AMAS improves channel characteristics by adding eight horizontal polarized channels near 118.75 GHz, which is the first operational polar-orbiting satellite-based sensor to observe the atmosphere in Earth-scanning mode in the 118-GHz oxygen band. Also, AMAS has more channels at 183 GHz than MWHS. This paper analyzes the channel capability and radiometric characteristics of AMAS at 118.75 GHz. Before the launch of FY-3C, the intensive thermal vacuum (T/V) tests for AMAS were carried out in a 2-m T/V chamber, and the basic parameters were obtained, such as the receiver nonlinearity and sensitivity of each channel for AMAS. Furthermore, system nonlinear error correction and bias correction of warm and cold targets are derived after the T/V data analysis and will be used for calibration processing, playing an important role in level 1 and 2 data processing. Accuracies of calibrated channels in AMAS range from 0.48 K to 2.7 K.