Manned Space Flight Network

After the end of Skylab, the MSFN and STADAN were merged to form the Spaceflight Tracking and Data Network (STDN).

STDN was in turn replaced by the satellite-based Tracking and Data Relay Satellite System (TDRSS) during the Space Shuttle program, being used as of 2009[update].

Deep space missions are visible for long periods of time from a large portion of the Earth's surface, and so require few stations (the DSN uses only three, as of February 20, 2010[update]).

These differing requirements led NASA to build a number of independent tracking networks, each optimized for its own mission.

For the Mercury, Gemini, and Apollo missions, these were the primary means of communication, with the Deep Space Network (DSN) being assigned a supporting/backup role.

A Pacific Ocean ship (USNS Wheeling) and the Goldstone Deep Space Communications Complex (GDS), California were used during Gordon Cooper's 1963 MA-9 flight.

From a NASA technical report on the history of the MSFN:[6] The technical facts of life were these: the radars of the Mercury and Gemini Networks obviously could not track two spacecraft orbiting the Moon a quarter-million miles away: neither could the small MSFN telemetry antennas hope to pick out the telemetry and voice messages in the weak signals arriving from the vicinity of the Moon.

A Jet Propulsion Laboratory (JPL) system called "Unified S-band", or USB, was selected for Apollo communications, which allowed tracking, ranging, telemetry, and voice to all use the same S band transmitter.

JPL was naturally reluctant to compromise the objectives of its many unmanned spacecraft by turning three of its DSN stations over to the MSFN for long periods.

How could the goals of both Apollo and deep space exploration be achieved without building a third 26-m antenna at each of the three sites or undercutting planetary science missions?

Deep space missions would not be compromised nearly as much as if the entire station's equipment and personnel were turned over to Apollo for several weeks.

TDRSS uses a network of 10 geostationary communication satellites, and a single ground station at White Sands Test Facility.