TDRS

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A Tracking and Data Relay Satellite (TDRS) is a one of a network of communications satellites used by NASA and other United States government agencies for communication to satellites or the International Space Station. The system was designed to replace an existing network of ground stations that had supported all of NASA's manned flight missions. The prime design goal was to increase the time spacecraft were in communication with the ground and improve the amount of data that could be transferred.

The initial seven satellites were built by TRW; later, three versions have been put together by Boeing's Satellite Systems division. 10 satellites have been launched. 9 satellites are still in service.

The first TDRS was launched in 1983 on the Space Shuttle Challenger's first flight, STS-6. The Boeing-built Inertial Upper Stage that took the satellite from Challenger's orbit to its ultimate geostationary orbit did not deliver to the correct orbit. As a result, the satellite was forced to use its onboard thrusters to get it to the correct orbit. This reduced its operational lifetime, and has since been reduced to part-time duty supporting Antarctic communications.

The second was lost on the Challenger's 10th mission when it was destroyed with the Challenger shortly after liftoff on STS-51-L in 1986. The next five were launched on other shuttles. The three Boeing-built successors were launched on Atlas rockets in 2000 and 2002. A NASA press release summarized the capabilities of the system as a whole:

"Working solo, TDRS-1 provided more communication coverage, in support of the September 1983 Shuttle mission, than the entire network of NASA tracking stations had provided in all previous Shuttle missions."

The communications systems on the TDRS satellites were designed to support multiple missions at the same time. Each satellite has S band, K_u band and K_a band systems which support multiple data-rates. The newer Boeing satellites are able to support more communications than the older TRW-built satellites.

[edit] Satellite variants

• First Generation TDRS

• Second Generation TDRS

[edit] Launch history

• TDRS A was launched April 4, 1983 on STS-6
• TDRS B was destroyed January 28, 1986 on STS-51-L in the Challenger disaster
• TDRS C was launched September 29, 1988 on STS-26
• TDRS D was launched March 13, 1989 on STS-29
• TDRS E was launched August 2, 1991 on STS-43
• TDRS F was launched January 13, 1993 on STS-54
• TDRS G, the replacement for the lost TDRS B, was launched July 13, 1995 on STS-70
• TDRS H, the first Boeing-built craft, was launched January 20, 2000 on an Atlas IIa
• TDRS I was launched on March 8, 2002 on an Atlas IIa
• TDRS J was launched on December 10, 2002 on an Atlas IIa

[edit] External links

• NASA's Goddard Space Flight Center TDRSS page
• NASA's TDRSS program overview page