The CAMEX-4 High Altitude MMIC Sounding Radiometer (HAMSR) dataset was collected by the High Altitude Monolithic Microwave Integrated Circuit (MMIC) Sounding Radiometer (HAMSR), which is a microwave atmospheric sounder recently developed by JPL under the NASA Instrument Incubator Program. Operating with 25 spectral channels in the 50-190 HGz region, it provides measurements that can be used to infer the 3-D distribution of temperature, water vapor, and liquid water in the atmosphere, even in the presence of clouds. HAMSR was mounted in a wing pod of a NASA ER-2 research aircraft.