Radiometer Calibration for the NASA Tropics Cubesat Mission

This paper describes the TROPICS L1 calibration algorithm. The NASA TROPICS mission [1] hosts a passive microwave radiometer [2] that provides temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapor profiles using three channels near the 183 GHz water vapor absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher resolution water vapor channels), and a single channel at 205 GHz that is more sensitive to precipitation-sized ice particles. Noise Diodes (ND) are an attractive option for calibration of small satellite sounders, which replaces the bulky and heavy internal iron-filled epoxy calibration target that is difficult to shield from the sun [3]. The TROPICS radiome-ter's pre-launch thermal-vacuum testing characterized the ND output temperature and the radiometer's non-linearity, and also verified the characterization using parts of the algorithm described in this paper[4].