Marisat 3 was the second of a series of COMSAT maritime communications satellites.

The satellite was operated at orbital position of 176 degrees east from 1976 to 1991.

It was transferred to 326.1° E (33.9° W), Over the Atlantic Ocean, and since 1999 has been providing a broadband data link to the US National Antarctic Foundation in Antarctica at the South Pole's Amundsen-Scott research station.

Intelsat engineers used the remaining fuel on board to raise the orbit about 125 miles (200 km) above the geostationary arc and put it into an array orbit.

Marisat 3 was launched by a Delta rocket from Cape Canaveral Air Force Station, Florida, at 22:44 UTC on October 14, 1976.