The Heat Capacity Mapping Mission (HCMM) spacecraft was the first of a series of Applications Explorer Missions (AEM). The objective of the HCMM was to provide comprehensive, accurate, high-spatial-resolution thermal surveys of the surface of the earth. The HCMM spacecraft was made of two distinct modules: an instrument module, containing the heat capacity mapping radiometer and its supporting gear, and a base module, containing the data handling, power, communications, command, and attitude control subsystems required to support the instrument module.
During February 21-23, 1980, the HCMM orbital altitude was lowered from 620 km to 540 km to stop the drift of the orbit plane to unfavorable sun angles which in turn reduced the power collection capability of the solar panels. The operations of the spacecraft were terminated on September 30, 1980.