The program began as the experimental Maritime Orbital Test Satellite (Marots) in 1973, but was subsequently changed to an operational system resulting in a name change, a satellite redesign, and delayed development. Marecs is operated by ESA for Inmarsat. Spacecraft: Based on British Aerospace ECS platform.3-axis stabilised to 0.2 deg (pitch, roll) using fully redundant momentum wheels, thrusters, and nutation dampers. Redundant sun sensors provide 0.04 deg knowledge. Two sun-tracking solar arrays provide 955 W (BOL) with 2 NiCd batteries for eclipse power. Hydrazine propulsion system for station-keeping. Payload: Three repeaters: shore-to-ship with 5 MHz bandwidth, ship-to-shore with 6 MHz bandwidth, shore-to-shore with 0.5 MHz bandwidth. These provide 35 two-way voice channels plus search and rescue capabilities. One 2 m diameter L-Band antenna and 2 horns (one transmit, one receive) for 4/6 GHz channels. All antennas have full Earth coverage.