The two MACSAT (Multiple Access Communications satellite) spacecraft are third generation DSI digital communications satellites designed to demonstrate tactical UHF voice, data, fax and video store and forward capabilities for the U.S. military. The gravity gradient boom on one spacecraft appears to have failed to deploy. The other spacecraft was used during Operation Desert Storm for message relay to and from military troops in the Gulf region.

Spacecraft are gravity gradient stabilized (approx. 5 degrees control) using a 9+ meter boom and 2.3 kg tip mass. Damping achieved via hysteresis rods. Z-coil used to invert the spacecraft should it stabilize upside down. The spacecrafts were built on a 16-sided cylindrical structure. Body mounted solar cells provide 10 to 17 Watts of orbit average power with redundant NiCd batteries providing 150 Whr capacity. The payload, similar to the GLOMR payload, used dual digital processors to provide redundancy and 2.4 to 16 megabytes of data storage.

Each satellite contains two digitally tunable 10 Watt transmitters, a 65 Watt high power auxiliary receiver for spacecraft command and hardware reconfiguration, and two antenna systems. This equipment was used to conduct store and forward communications demonstrations.

The MACSATs served as prototypes for the Navy's Arcticsat planned and later cancelled constellation of six similar satellites.