Title: Calibration and Test of the Microwave Radiometer Technology Acceleration (MiRaTA) CubeSat
Presenting Author: Kerri Cahoy
Organization: Massachusetts Institute of Technology
Co-Author(s): Gregory Allan, Ayesha Hein, Zachary Lee, Weston Marlow, Idahosa Osaretin, Michael DiLiberto, Daniel Cousins, William J. Blackwell

Abstract:
The Microwave Radiometer Technology Acceleration (MiRaTA) Mission is a 3U CubeSat developed for NASA ESTO by MIT and MIT Lincoln Laboratory. MiRaTA aims to increase the quality and temporal coverage of Earth atmospheric microwave sounding measurements while leveraging the low costs associated with the CubeSat form factor. Microwave radiometry is a significant contributor to weather and climate monitoring programs, but the sun-synchronous orbits of radiometers' host satellites limit revisit times and their internal calibration targets are subject to on-orbit variability that is difficult to model on the ground. MiRaTA will perform multi-channel radiometry over three frequency bands at 52-58 GHz, 175-191 GHz, and 206-208 GHz to measure temperature, water vapor, and cloud ice. MiRaTA also hosts the Compact Total Electron Count (TEC) / Atmospheric GPS sensor (CTAGS), a GPS Radio Occultation (GPSRO) system based on a modified off-the-shelf GPS receiver and a purpose-built patch antenna array. MiRaTA will use CTAGS to demonstrate radiometer calibration using an internal noise diode and co-located GPSRO measurements. By doing so, it will avoid using an expensive and bulky internal calibration target like those commonly used for microwave radiometry. The MiRaTA CubeSat has completed integration and environmental testing, and is awaiting launch as part of the ELaNa XIV in 2017. A payload thermal vacuum test was conducted involving a spinning payload with a cold blackbody target and a hot blackbody target to confirm proper function of the MiRaTA radiometer. Results indicate that the calibration accuracy for seven V-band channels and four G-band channels is within requirements; however, one channel for the G-band experiences higher noise than expected. Additionally, the CTAGS unit was verified to work with the integrated spacecraft. Results are also presented on the accuracy of thermal model predictions found by comparing the model to measured temperatures during the thermal vacuum.