A tracking and data relay satellite (TDRS) is a type of

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth ...

that forms part of the

Tracking and Data Relay Satellite System The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites (each called a tracking and data relay satellite, TDRS) and ground stations used by NASA for space communications. The system was desig ...

(TDRSS) used by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft, the

International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ( ...

, 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 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, above the surface of the Earth. The first seven TDRSS satellites were built by the TRW corporation. The three later versions have been manufactured by the

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and p ...

corporation's Satellite Systems division. Thirteen satellites have been launched; however, one was destroyed in the

Challenger disaster On January 28, 1986, the broke apart 73 seconds into its flight, killing all seven crew members aboard. The spacecraft disintegrated above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 11:39a.m. EST (16:39 UTC). It was ...

. TDRS-1 was decommissioned in October 2009. TDRS-4 was decommissioned in December 2011. Ten TDRSS satellites are currently in service. All of the TDRSS satellites have been managed by NASA's Goddard Space Flight Center. The contract for TDRS versions L & K was awarded to Boeing on December 20, 2007. On November 30, 2011, NASA announced the decision to order an additional third-generation TDRS satellite, TDRS M.

Operations

The first tracking and data relay satellite was launched in 1983 on the Space Shuttle ''Challenger's'' first flight, STS-6. The Boeing-built

Inertial Upper Stage The Inertial Upper Stage (IUS), originally designated the Interim Upper Stage, was a two-stage, solid-fueled space launch system developed by Boeing for the United States Air Force beginning in 1976 for raising payloads from low Earth orbit to ...

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 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; 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 Atlas is a family of US missiles and space launch vehicles that originated with the SM-65 Atlas. The Atlas intercontinental ballistic missile (ICBM) program was initiated in the late 1950s under the Convair Division of General Dynamics. Atlas was ...

s 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 first generation of TDRS are planned to be retired in 2015.

TDRSS ground terminals

The two TDRSS satellite ground terminals are located at NASA White Sands Complex, which is in the Las Cruces area. All radioed commands and received

telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", an ...

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

ordered the design and construction of a second ground terminal system about 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 Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cent ...

to support TDRS.

Bilateration ranging transponder system

The bilateration ranging

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

system (BRTS) provides tracking support for TDRS spacecraft. BRTS consists of four sites located at

White Sands Missile Range White Sands Missile Range (WSMR) is a United States Army military testing area and firing range located in the US state of New Mexico. The range was originally established as the White Sands Proving Ground on 9July 1945. White Sands National P ...

(WSC),

(GRGT), Ascension Island (ACN), and Alice Springs, Australia (ALS).

Design

The communications systems of the TDRSS satellites were designed to support multiple missions at the same time. Each satellite has S band, K_u band (1st Gen only), and K_a band (2nd gen only) electronic communication systems hardware that operate at different carrier frequencies and also support various data-rates. 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'' * First generation TDRS: models A to G * Second generation TDRS: models H to J * Third generation TDRS: models K to M * Launch site: Cape Canaveral, United States * Launch vehicle:

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program ...

Atlas II Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. The Atlas II was a direct evolution of the Atlas I, featuring longer first stage tanks, higher-performing engine ...

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture between Lockheed Mart ...

booster * Mass: 2108.0 kg * Nominal power: 1700.0W

Launch history

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

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 An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

s below 2000 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

and near 14.3 (plus or minus 0.9)

GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

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

Gallery

File:1993 s54 TDRS-F.jpg, TDRS is deployed on STS-54 with 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 The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the National Aeronautics and Space Administration's (NASA) ten field centers. Since December 1968 ...

. File:TDRS-K satellite before launch.jpg, TDRS-K prior to launch at Kennedy Space Center.

References

Notes

NASA's Goddard Space Flight Center TDRS K/L Official Page

External links

NASA's TDRSS program overview page

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