View source for Tracking and data relay satellite

{{outdated|date=June 2024}}
{{Short description|American communications satellite}}
{{Use mdy dates|date=April 2014}}
{{Redirect|TDRS|the record label|Travis Dickerson}}
{{broader|Inter-satellite radiocommunication satellite}}

[[File:Map of TDRS.png|400px|thumb|Location of TDRS as of March 2019]]
[[File:TDRS Heart of Communication.ogv|thumb|The launch of TDRS-K begins the replenishment of the fleet through the development and deployment of the next generation spacecraft.]]
[[File:Tracking Data Relay Satellite (TDRS) Orbital Fleet Communicating with User Spacecraft.ogg|thumb|This visualization begins by showing how a typical spacecraft (NIMBUS-7) communicated with the ground before TDRS.]]
[[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]], 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]]. TDRS-1 was decommissioned in October 2009.<ref name=T1decomm>{{cite web|url=http://spaceflightnow.com/news/n0910/13tdrs/ |title=Breaking News &#124; 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) &#124; 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> 

==Operations==
The first tracking and data relay satellite was launched in 1983 on the [[Space Shuttle Challenger|Space Shuttle ''Challenger's'']] first flight, [[STS-6]]. The Boeing-built [[Inertial Upper Stage]] that was to take the satellite from Challenger's orbit to its ultimate [[geosynchronous orbit]] suffered a failure that caused it not to deliver the TDRS to the correct orbit. As a result, it was necessary to command the satellite to use its onboard [[Reaction control system|rocket thrusters]] to move it into its correct orbit. This expenditure of fuel reduced its capability to remain in a [[geostationary]] orbit; by late 1997 the orbit had changed to the point that the satellite was able to see the South Pole, and an uplink/downlink station was installed at [[Amundsen–Scott South Pole Station]] in January 1998;<ref name=southpole>{{cite web |url=http://antarcticsun.usap.gov/features/contentHandler.cfm?id=1742 |title=TDRS history |date=April 10, 2009}}</ref> TDRS-1 was an important communication uplink for Antarctic research until 2009.

The second tracking and data relay satellite was destroyed along with ''Challenger'' shortly after launch during the [[STS-51-L]] mission in January 1986.  The next five TRW-built TDRSS satellites were successfully launched on other Space Shuttles. Three follow-up Boeing-built satellites were launched by [[Atlas rocket]]s in 2000 and 2002. A NASA Press Release<ref>{{cite web|url=http://www.nasa.gov/home/hqnews/2003/apr/HP_news_03130.html |title=NASA – Pioneer NASA Spacecraft Celebrates 20 Years of Service |publisher=Nasa.gov |access-date=February 5, 2014}}</ref> summarized the capabilities of the system as a whole:

<blockquote>"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."</blockquote>

The first generation of TDRS are planned to be retired in 2015.<ref name=NASA>{{cite web|url=http://www.nasa.gov/home/hqnews/2011/nov/HQ_C11-049_TDRS.html|title=NASA Exercises Contract Option For TDRS-M Satellite Decision Will Retain Hundreds of Jobs |date=November 30, 2011|publisher=NASA|access-date=December 12, 2011}}</ref>

==TDRSS ground terminals==
The two [[TDRSS#Ground segment|TDRSS satellite ground terminal]]s are located at NASA White Sands Complex, which is in the [[Las Cruces, New Mexico|Las Cruces]] area. All radioed commands and received [[telemetry]] that go to and from the tracking and data relay satellites go by way of these terminals at the White Sands Complex. At first, just one large ground terminal system for the TDRSS was designed and built. However, some years later, due to increased user demand [[NASA]] ordered the design and construction of a second ground terminal system about {{convert|5|km}} away. Thus, there are now two functionally identical and redundant satellite ground terminals there, which are known as the [[White Sands Complex]].  Due to a Zone of Exclusion, no user support over the Indian Ocean, a ground terminal was built in [[Guam]] to support TDRS.<ref name=spacecomm/>

=== Bilateration ranging transponder system ===
The bilateration ranging [[transponder]] system (BRTS) provides tracking support for TDRS spacecraft. BRTS consists of four sites located at [[White Sands Missile Range]] (WSC), [[Guam]] (GRGT), [[Ascension Island]] (ACN), and [[Alice Springs]], Australia (ALS).<ref>Space Network Ground Segment Sustainment (SGSS) Mission System Requirements Document (MSRD). Section 3.5. NASA/GSFC: November 21, 2008</ref>

==Design==
[[File:Space Shuttle Discovery at Udvar-Hazy Center.jpg|thumb|A first-generation TDRS satellite on display at the [[Steven F. Udvar-Hazy Center]], placed above [[Space Shuttle Discovery|Space Shuttle ''Discovery'']].]]
The communications systems of the TDRSS satellites were designed to support multiple missions at the same time. Each satellite has [[S band]], [[Ku band|K<sub>u</sub> band]] (1st Gen only), and [[Ka band|K<sub>a</sub> band]] (2nd gen only) electronic communication systems hardware that operate at different carrier frequencies and also support various data-rates.<ref>{{cite web|url=http://www.nasa.gov/centers/goddard/pdf/97440main_TDRS_fs_9.18.pdf |title= NASA Goddard TDRS Radio Frequency Systems (need Adobe Acrobat Reader)|publisher=Nasa.gov|access-date=February 5, 2014}}</ref> The newer Boeing satellites are able to support more communications than the older TRW-built satellites.

==Different versions of the TDRS ==
: ''Section source: NASA TDRSS official site''<ref>{{cite web|url=https://www.spacecomm.nasa.gov/spacecomm/programs/tdrss/default.cfm |archive-url=https://web.archive.org/web/20090320041300/https://www.spacecomm.nasa.gov/spacecomm/programs/tdrss/default.cfm |url-status=dead |archive-date=March 20, 2009 |title=Tracking and Data Relay Satellite (TDRS) &#124; NASA |publisher=Spacecomm.nasa.gov |date=November 13, 2013 |access-date=February 5, 2014}}</ref>
* First generation TDRS: models A to G
* Second generation TDRS: models H to J
* Third generation TDRS: models K to M<ref>{{cite web|url=http://space.skyrocket.de/doc_sdat/tdrs-11.htm |title=TDRS 11, 12, 13 (TDRS K, L, M) |publisher=Space.skyrocket.de |access-date=August 18, 2017}}</ref>
* Launch site: [[Cape Canaveral]], United States
* Launch vehicle: [[Space Shuttle]], [[Atlas II]] or [[Atlas V]] booster
* Mass: 2108.0&nbsp;kg
* Nominal power: 1700.0{{nbsp}}W

{|class="wikitable sortable collapsible"
|-
!colspan=2 |Capability
|1st gen
|2nd gen
|3rd gen

|-
|colspan=2 style="background:#3d4;"|[[Solar panels|Solar Panels]]
|2
|2
|2

|-
|colspan=2 style="background:#f99;"|Single Access Antenna
|2
|2
|2

|-
|style="background:#f99;"|
|[[S band]]
|yes
|yes
|yes

|-
|style="background:#f99;"|
|[[Ku band]]
|yes
|yes
|yes

|-
|style="background:#f99;"|
|[[Ka band]]
|no
|yes
|yes

|-
|colspan=2 style="background:#3d4;"|Multi Access Antenna
| 
| 
| 

|-
|style="background:#3d4;"|
|receive elements
|30
|32
|32

|-
|style="background:#3d4;"|
|transmit elements
|12
|15
|15

|-
|style="background:#3d4;"|
|[[beamforming]]
| 
|on-board
|ground

|-
|style="background:#3d4;"|
|[[S band]]
|yes
|yes
|yes

|-
|colspan=2 style="background:#f99;"|Omni Antenna
| 
| 
| 

|-
|style="background:#f99;"|
|[[S band]]
|yes
|yes
|yes

|-
|colspan=2 style="background:#3d4;"|Space-to-ground Antenna
|2.0m
|2.4m
| 

|-
|style="background:#3d4;"|
|[[S band]]
|yes
|yes
|yes

|}

=== Launch history ===
: ''Sub-section source: NSSDC Master Catalog Display: Spacecraft''
{{See also|List of TDRS satellites}}
Note: while a TDRSS satellite is in the manufacturing process it is given a letter designation, but once it has successfully achieved the correct geosynchronous orbit it is referred to with a number (for example, TDRS-A during development and before on-orbit acceptance, and TDRS-1 after acceptance on orbit and put into operational use). Thus, satellites that are lost in launch failures or have massive malfunctions are never numbered.

===TDRS background===
:''Source: NASA: TDRS A Satellite''<ref name=tdrsa>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1983-026B |title=NASA – NSSDC – Spacecraft – Details |publisher=Nssdc.gsfc.nasa.gov |date=August 16, 2013 |access-date=February 5, 2014}}</ref>
TDRS-A was the first of TDRSS multiple satellite tracking system. The system is a concept utilizing communication satellite technology that improves and economizes the satellite tracking and [[telemetry]] operations. The base three [[geosynchronous satellites]] (one a standby) track and receive data from satellites for relay to a ground station. The two primary active satellites are separated in orbit by at least 130 degrees longitude.

One system is used for tracking satellites with [[apogee]]s below 2000&nbsp;km (the great majority of satellites), and the other for those with higher apogees. Use of operating [[frequencies]] near 2150 (plus or minus 150) [[MHz]] and near 14.3 (plus or minus 0.9) [[GHz]] were the initial plan.

TDRSS was originally intended to support satellites with apogees below 12,000&nbsp;km. Spacecraft in the TDRSS require only one communications system, since ground-based telemetry stations will be compatible with TDRSS equipment.

==Gallery==
<gallery mode="packed" heights="200px">
File:1993 s54 TDRS-F.jpg|TDRS is deployed on [[STS-54]] with [[Inertial Upper Stage|IUS booster]].
File:TDRS gen1.jpg|First-generation TDRS.
File:TDRS gen2.jpg|Second-generation TDRS.
File:TDRS-G at KSC.jpg|TDRS-G at [[Kennedy Space Center]].
File:TDRS-K satellite before launch.jpg|TDRS-K prior to launch at Kennedy Space Center.
</gallery>

==See also==
{{colbegin}}
* [https://esc.gsfc.nasa.gov/projects/ACCESS?tab=tdrs%20fleet TDRS GSFC NASA page]
* [[Space Communications and Navigation Program|SCaN]] Program
* [[European Data Relay System]]
* [[Luch (satellite)]]
* [[Indian Data Relay Satellite System]]
* [[Space Network]]
* [[Deep Space Network]]
* [[Near Earth Network]]
* [[Eastern Range]]
{{commons category|Tracking and Data Relay Satellite System}}
{{Portal|Spaceflight}}
{{colend}}

==References==
{{Reflist}}

==Notes==
* [http://tdrs.gsfc.nasa.gov/ NASA's Goddard Space Flight Center TDRS K/L Official Page]
* [https://web.archive.org/web/20100827212756/http://esc.gsfc.nasa.gov/space-communications/sn-sne.html NASA's Goddard Space Flight Center Space Network Official Page]

==External links==
* [https://web.archive.org/web/20090320041300/https://www.spacecomm.nasa.gov/spacecomm/programs/tdrss/default.cfm NASA's TDRSS program overview page]
* [https://web.archive.org/web/20101213165433/http://boeing.com/defense-space/space/bss/factsheets/601/tdrs_hij/tdrs_hij.html Boeing 2nd Generation]
* [https://web.archive.org/web/20110629103821/http://www.boeing.com/defense-space/space/bss/factsheets/601/tdrs_kl/tdrs_kl.html Boeing 3rd Generation]
{{TDRS}}
{{GSFC}}

[[Category:Communications satellites]]
[[Category:Tracking and Data Relay Satellite| ]]
[[Category:Satellites of the United States]]
[[Category:Articles containing video clips]]
[[Category:Satellites by type]]