The High Altitude MMIC Sounding Radiometer (HAMSR) is a 25-channel microwave atmospheric sounder operating as a cross-track scanner. There are three bands: an 8-channel band near 50-GHz, used for primary temperature sounding; a 10-channel band near 118 GHz, used for secondary temperature sounding and assessment of scattering; a 7-channel band near 183 GHz, used for water vapor sounding. The instrument is continuously self-calibrating using internal calibration targets. Radiometric sensitivity at the composite sampling cells provided in the archive is typically 0.1 and ranges up to 0.25 K for the stratospheric channels. Calibration accuracy is estimated at better than 1 K for temperature sounding and better than 2 K for water vapor sounding. Temperature weighting function peaks are distributed between the surface and the flight altitude. HAMSR was mounted in a wing pod of a NASA ER-2 research aircraft. The TCSP mission collected data for research and documentation of cyclogenesis, the interaction of temperature, humidity, precipitation, wind and air pressure that creates ideal birthing conditions for tropical storms, hurricanes and related phenomena. The goal of this mission was to help us better understand how hurricanes and other tropical storms are formed and intensify. Regular image processing was available beginning on 12 July. The scan schedule was maintained through the end of July.