The two Multiple Access Communications Satellites were 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 apparently failed to deploy. The other spacecraft was used during Operation Desert Storm for message relay to and from military troops in the Gulf region.

The spacecraft was gravity gradient stabilized (approx.5 degrees control) using a 9+ meter boom and 2.3 kg tip mass. Damping was achieved via hystersis rods. A Z-coil was used to invert the spacecraft should it stabilize upside down. Dual digital processors provided redundancy and were provided with 2.4 to 16 megabytes of data storage. The 16 sided cylindrical structure had body mounted solar cells which provided 10 to 17 watts of orbit average power. Redundant NiCd batteries provided 150 Whr capacity. The payload included 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.

Typical orbit: 613 x 739 km, 90 deg inclination. Length: 0.36 m (1.17 ft). Maximum Diameter: 0.61 m (2.00 ft). Mass: 68 kg (149 lb).

• 1990 May 9 - Macsat 1; M-1 - Launch Site: Vandenberg. Launch Complex: SLC5. Launch Vehicle: Scout. Mass: 68 kg (149 lb). Perigee: 602 km (374 mi). Apogee: 753 km (467 mi). Inclination: 89.90 deg. Period: 98.30 min.
  Multiple Access Communications Satellite; global store and forward communications. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

• 1990 May 9 - Macsat 2; M-2 - Launch Site: Vandenberg. Launch Complex: SLC5. Launch Vehicle: Scout. Mass: 68 kg (149 lb). Perigee: 600 km (370 mi). Apogee: 749 km (465 mi). Inclination: 89.90 deg. Period: 98.30 min.
  Multiple Access Communications Satellite; global store and forward communications. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).