The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office (ESTO). The science payload on MiRaTA consists of a tri-band microwave radiometer and GPS radio occultation (GPSRO) experiment. The microwave radiometer takes measurements of all-weather temperature (V-band, 52–58 GHz), water vapor (G-band, 175–191 GHz), and cloud ice (G-band, 207 GHz) to provide key observations used to improve weather forecasting. The GPSRO experiment, called the Compact TEC (Total Electron Content) and Atmospheric GPS Sensor (CTAGS) measures profiles of temperature and pressure in the upper neutral atmosphere and electron density in the ionosphere. The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, (2) new GPS receiver and patch antenna array technology for both neutral atmosphere and ionospheric GPS radio occultation retrieval on a nanosatellite, and (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements.