Development of Compact High Altitude Imager and Sounding Radiometer (CHAISR) microwave radiometers for meteorological observation from HALE UAV

A set of compact microwave radiometers are under development for tropospheric sounding and imaging, as a part of the Compact High Altitude Imager and Sounding Radiometer (CHAISR) that operates in lower stratosphere. It aims to observe vertical temperature profiles and column-averaged water vapour for entire troposphere where most weather system takes place. Given total weight (4 kg) and power (50 W) constraints for the CHAISR are not the only challenges. The CHAISR requires nominal operation in thermal range between -75 and +43 °C up to 50 hPa. Along with optical cameras and in situ sensors in the CHASIR, microwave radiometers are to fit in 130 mm diameter and 290 mm length with total weight less than 1.5 kg for conical scan unit. Maximum power consumption of less than 15 W does not allow conventional internal blackbody calibration facility onboard, and alternative methods has been developed. Frequency ranges of three radiometer bands are ~20, ~40, and ~55 GHz, with 16 total channels. This MMIC based compact radiometers use quasi-correlation design for continuous observation for both reference and scene. Numerical simulation of the radiometer design shows less than 1 °K of RMSE is expected. Manufacture of the CHAISR is expect to be first quarter of 2017 and test flight is planned in summer of the same year.