GPM microwave imager key technologies, performance and calibration results

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) Instrument was built and tested by Ball Aerospace and Technologies Corporation (Ball) under a contract with the GPM program at NASA Goddard. The design is a light-weight and compact scanning microwave radiometer with a stowable main reflector. Because calibration is a key consideration for GMI, the design includes multiple features to enhance calibration accuracy including a dual calibration system. The dual calibration system uses noise diodes in addition to hot and cold targets to provide on-board computation of nonlinearity and detection of transient errors in the hot and cold targets. The results of the ground calibration testing are presented. The noise diodes are key to reducing ground calibration errors. In this paper we describe the instrument and present the measured performance of the GMI instrument. We describe the key technologies developed for the GMI instrument. The measured performance is presented along with trend data through spacecraft level testing. The results of the instrument calibration are also summarized.