Toward Resolving the Temporal Evolution of Precipitation Processes over the Ocean: On-Orbit Evaluation of the TEMPEST-D Microwave Radiometer

The advent of small satellites and miniaturized instrument technology enables a new paradigm for observation from Low Earth Orbit (LEO), namely the ability to time resolve physical processes with sensor constellations flying in close formation. Precipitation processes, which can have time scales of minutes in active convection, are a prime target to apply this capability. The Temporal Experiment for Storms and Tropical Systems (TEMPEST) mission was originally conceived to globally map the on-set of precipitation over the ocean and the surrounding environmental conditions. A demonstration satellite, termed TEMPEST-D, was designed, built and deployed from the International Space Station (ISS) in July 2018. TEMPEST-D is a 6U CubeSat carrying a cross-track imaging, five channel passive microwave radiometer with bands from 90-200 GHz. Critical to the TEMPEST design is the ability to accurately resolve the time derivative of the scene brightness temperature. This is facilitated by the inclusion of high-quality, blackbody calibration sources viewed thought the antenna, end-to-end. In this way, the sensor design and expected data quality are similar to the Advanced Technology Microwave Sounder (ATMS) on the NOAA polar satellites. We will present the early orbit evaluation of the TEMPEST-D radiometer performance relative to the requirements for resolving precipitation processes and the temporal evolution of the environmental water vapor field at mid and high-levels in the troposphere. We will also compare the performance to that from similar legacy sensors, such as ATMS, to document how this state-of-the-art CubeSat sensor compares to those sensors currently used in operational weather forecasting.