Tracking and Data Relay Satellite

A Tracking and Data Relay Satellite (TDRS) is one of a network of communications satellites of the Tracking and Data Relay Satellite System (TDRSS) 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. All were managed by NASA Goddard Space Flight Center. [ [http://www.nasa.gov/centers/goddard/news/topstory/2003/0403tdrs20th.html NASA Goddard TDRSS 20th Year] ] The contract for TDRS versions L & K was awarded to Boeing on December 20, 2007. [ [http://www.reuters.com/article/ousiv/idUSN2019803020071221 Boeing to build NASA tracking, data relay satellites] ]

Operations

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 [ [http://www.nasa.gov/home/hqnews/2003/apr/HP_news_03130.html NASA Press Release April 3, 2003 ] ] 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."

Design

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. [ [http://www.nasa.gov/centers/goddard/pdf/97440main_TDRS_fs_9.18.pdf NASA Goddard TDRS Radio Frequency Systems] (need Adobe Acrobat Reader)] The newer Boeing satellites are able to support more communications than the older TRW-built satellites, however, they have had significantly shorter and more problematic lifetimes.

Variants and history

: "Section source: NASA TRDSS Official Site" [ [https://www.spacecomm.nasa.gov/spacecomm/programs/tdrs.cfm NASA TDRSS Official Site] ]
*First Generation TDRS: models A thru G
*Second Generation TDRS: models H thru J

Launch history

: "Sub-section source: NSSDC Master Catalog Display: Spacecraft"

References

* [http://msp.gsfc.nasa.gov/tdrss/oview.html NASA's Goddard Space Flight Center TDRSS Official Page] : "Note: all references were accessed Oct. 10, 2007"

External links

* [https://www.spacecomm.nasa.gov/spacecomm/programs/tdrs.cfm NASA's TDRSS program overview page]
* [http://screamyguy.net/ephemeris/viewer.htm?TITLE=TDRS View current TDRS constellation] (Java applet)