Gross mass: 2,430 kg (5,350 lb).
Lockheed Missiles and Space Company was awarded a $34 million contract to build a spacecraft for the Satellite Infrared Experiment (SIRE), designed to measure long wave infrared signatures. The spacecraft would also carry two secondary payloads - a space sextant and a sensor that would measure the isotopic composition of solar flares.
SAMSO terminated the SIRE (Satellite Infrared Experiment) contract with Lockheed because of large cost overruns. The SIRE payload was to have been launched on flight P80-2 and was to have measured the long wave infrared signatures of space objects against the stellar background. SAMSO began to develop a program to fly the SIRE sensor on space shuttle sortie missions around the mid-1980s.