Equivalent emissivity correction of the blackbody on-board MWRI-RM

The microwave imager (MWRI-RM) uses the dual-point calibration on the feed port surface method to achieve real-time on-orbit calibration. Within one calibration cycle, the feed rotates under the cold-space reflector to receive the cosmic background brightness temperature as the cold calibration point; the feed then rotates under the onboard blackbody to receive blackbody radiation as the hot calibration point. Therefore, the emissivity of the onboard blackbody directly affects the on-orbit calibration accuracy of the microwave imager, making it necessary to conduct blackbody correction tests on the ground to calibrate the blackbody observation model. Ground vacuum test results show that the emissivity of the onboard blackbody in the 10.65–183 GHz frequency range is better than 0.9975, and after emissivity correction, the error when the microwave imager observes the onboard blackbody is better than 0.2 K.