AMSC-1 is part of MSAT, the first dedicated system in North America to provide mobile telephone, radio, facsimile, paging, position location, and data communications for users on land, at sea, and in the air.

AMSC-1 has the capacity to support up to 2000 simultaneous radio channels, depending on the type of antenna used and bandwidth allocated. Communications between the mobile users and the satellites are accomplished in L-band; terrestrial feeder stations use Ku-band to communicate with the satellite and with one another.

Like others in the HS-601 series, the satellite consists of a cube-shaped center payload section, with the solar panel wings extending from the north and south sides, and an antenna array. The HS-601 is composed of two modules: the primary structure, which carries all launch vehicle loads and contains the propulsion system, bus electronics, and battery packs; and a payload module, which holds communications equipment and isothermal heat pipes. Reflectors, antenna feeds, and solar arrays mount directly to the primary module, and antenna configurations can be placed on three faces of the bus. Such a modular approach allows work to proceed in parallel on both structures, thereby shortening the manufacturing schedule and test time.

The satellite measures approximately 62 feet (18.9 meters) across with its two antennas deployed, and 68 feet, 9 inches (21 meters) long from the tip of one three-panel solar wing to the tip of the other. These arrays generate more than 3 kilowatts, backed up by a 28-cell nickel-hydrogen battery for use during an eclipse.