Radiometric Calibration of a Hyperspectral Microwave Sounder

Hyperspectral microwave sounding of atmospheric temperature and humidity profiles is a promising application for spaceborne weather observation. This approach extends the capabilities of more traditional infrared sounders to include incloud retrievals, significantly expanding the observational scope of the remote sensing technique. Calibration of microwave spectrometers is a vital step that ensures the accuracy of observations and, consequently, of retrieved profiles. Here, we study the calibration of HiSRAMS, a prototype tested on an airborne platform in Canada in 2021-2023. Due to design constraints, HiSRAMS is susceptible to artifacts arising from quasi-optical standing waves and to environment-dependent biases. Cryogenic calibration results, standing wave corrections, and bias analysis are discussed.