Pre-Launch Calibration and Performance Study of the PolarCube 3U Temperature Sounding Radiometer Mission

Abstract:

The positive impact of passive microwave observations of tropospheric temperature, water vapor and surface variables on short-term weather forecasts has been clearly demonstrated in recent forecast anomaly growth studies. The development of a fleet of such passive microwave sensors especially at V-band and higher frequencies in low earth orbit using 3U and 6U CubeSats could help accomplish the aforementioned objectives at low system cost and risk as well as provide for regularly updated radiometer technology. The University of Colorado’s 3U CubeSat, PolarCube is intended to serve as a demonstrator for such a fleet of passive sounders and imagers. PolarCube supports an eight channel, double sideband 118.7503 GHz passive microwave sounder. The mission is focused primarily on sounding in Arctic and Antarctic regions with the following key remote sensing science and engineering objectives: (i) Collect coincident tropospheric temperature profiles above sea ice, open polar ocean, and partially open areas to develop joint sea ice concentration and lower tropospheric temperature mapping capabilities in clear and cloudy atmospheric conditions. This goal will be accomplished in conjunction with data from existing passive microwave sensors operating at complementary bands; and (ii) Assess the capabilities of small passive microwave satellite sensors for environmental monitoring in support of the future development of inexpensive Earth Science missions.

To ensure fidelity of data from the instrument, the following goals are being achieved: (i) precise numerical analysis of the diffracted field produced by corrugated feed and spinning reflector antenna system to the determination of an optimal feed horn and reflector geometry such that the system efficiencies are maximized and precisely known (ii) precise calibration of the receiver by accurate characterization of the sensitivity of radiometer components to physical temperature variations (iii) retrieval of atmospheric temperature profiles and surface temperature in clear and cloudy air and initial comparison of obtained profiles with those retrieved from co-located space-borne instruments and sounding balloons in order to validate radiometer operation. The status of the instrument and spacecraft along with pre-launch testing will be presented.