The NAMMA High Altitude MMIC Sounding Radiometer (HAMSR) dataset consists of data collected by HAMSR, which is a 25-channel microwave atmospheric sounder operating as a cross-track scanner. It operates with three bands: an 8-channel band centered around 50 GHz, used for primary temperature sounding; a 10-channel band centered around 118 GHz, used for secondary temperature sounding and assessment of scattering; and a 7-channel band centered around 183 GHz, used for water vapor (humidity) sounding. The instrument continuously self-calibrates by using internal calibration targets. Radiometric sensitivity at the composite sampling cells provided in the archive is typically 0.1 K 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. These data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets.