[[File:Tracking Data Relay Satellite (TDRS) Orbital Fleet Communicating with User Spacecraft 2017 - 360 video.webm|thumb|Visualization depicting TDRS satellites communicating with customer satellites.]]
A '''tracking and data relay satellite''' ('''TDRS''') is a type of [[communications satellite]] that forms part of the [[TDRSS|Tracking and Data Relay Satellite System]] (TDRSS) used by [[NASA]] and other United States government agencies for communications to and from independent "User Platforms" such as [[satellites]], balloons, aircraft, the [[International Space Station or iss]], and remote bases like the [[Amundsen-Scott South Pole Station]]. This system was designed to replace an existing worldwide network of ground stations that had supported all of NASA's [[Human space flight|crewed flight missions]] and uncrewed satellites in low-Earth orbits. The primary system design goal was to increase the amount of time that these spacecraft were in communication with the ground and improve the amount of data that could be transferred. These TDRSS satellites are all designed and built to be launched to and function in [[geosynchronous orbit]], {{convert|35786|km|mi|abbr=on}} above the surface of the Earth.
The first seven TDRSS satellites were built by the [[TRW Inc.|TRW]] corporation. The three later versions have been manufactured by the [[Boeing]] corporation's [[Boeing Satellite Systems|Satellite Systems]] division. Thirteen satellites have been launched; however, one was destroyed in the [[Challenger disaster in 1986 killing 7 crew members in 1988 a TDRS satellite was put to space it replaced the TDRS destroyed in the challenger disaster]]. TDRS-1 was decommissioned in October 2009.<ref name=T1decomm>{{cite web|url=http://spaceflightnow.com/news/n0910/13tdrs/ |title=Breaking News | NASA retires 'queen' of tracking satellite fleet |publisher=Spaceflight Now |access-date=February 5, 2014}}</ref> TDRS-4 was decommissioned in December 2011. Ten TDRSS satellites are currently in service.<ref name="spacecomm">{{cite web|url=https://www.nasa.gov/directorates/heo/scan/services/networks/tdrs_main|title=Tracking and Data Relay Satellite (TDRS) | NASA|date=Oct 22, 2019|publisher=Spacecomm.nasa.gov|access-date=October 22, 2019}}</ref> All of the TDRSS satellites have been managed by NASA's [[Goddard Space Flight Center]].<ref>{{cite web|url=http://www.nasa.gov/centers/goddard/news/topstory/2003/0403tdrs20th.html |title=NASA – Top Story – TDRS 20th Anniversary – April 03, 2003 |publisher=Nasa.gov |access-date=February 5, 2014}}</ref> The contract for TDRS versions L & K was awarded to Boeing on December 20, 2007.<ref>{{cite web|url=https://www.reuters.com/article/ousiv/idUSN2019803020071221 |title=Boeing to build NASA tracking, data relay satellites |publisher=Reuters |date=December 20, 2007 |access-date=February 5, 2014}}</ref> On November 30, 2011, NASA announced the decision to order an additional third-generation TDRS satellite, [[TDRS-13|TDRS M]].<ref name=NASA/>
In 2022 NASA announced it would begin to phase out the TDRS system and hand off satellite relay services to commercial providers.<ref>{{Cite web |title=Companies Vie to Build NASA’s Next Communications Network - IEEE Spectrum |url=https://spectrum.ieee.org/nasa-new-network-tdrs |access-date=2024-10-17 |website=spectrum.ieee.org |language=en}}</ref> In 2024 it announced that while TDRS satellites would probably continue to operate for a decade or more, all new orbital missions would communicate through privately-operated satellite networks.<ref>{{Cite web |date=2024-10-16 |title=NASA to Embrace Commercial Sector, Fly Out Legacy Relay Fleet - NASA |url=https://www.nasa.gov/missions/tdrs/nasa-to-embrace-commercial-sector-fly-out-legacy-relay-fleet/ |access-date=2024-10-17 |language=en-US}}</ref>
