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. The contract for TDRS versions L & K was awarded to Boeing on December 20, 2007.

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 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. 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

• First Generation TDRS: models A thru G
• Second Generation TDRS: models H thru J

Launch history

Sub-section source: NSSDC Master Catalog Display: Spacecraft

Name	Launch date	Mission name	NSSDC ID No.	Notes
TDRS A	April 4, 1983	STS-6	1983-026B	also TDRS 1
TDRS B	January 28, 1986	STS-51-L	TDRSS-B	destroyed in the Challenger disaster, also TDRS 2
TDRS C	Sept. 29, 1988	STS-26	1988-091B	also TDRS 3
TDRS D	March 13, 1989	STS-29	1989-021B	also TDRS 4
TDRS E	August 2, 1991	STS-43	1991-054B	also TDRS 5
TDRS F	January 13, 1993	STS-54	1993-003B	also TDRS 6
TDRS G	July 13, 1995	STS-70	1995-003B	replacement for the lost TDRS B, also TDRS 7
TDRS H	June 30, 2000	Atlas IIa	2000-034A	First of the second generation of Boeing TDRS, also TDRS 8
TDRS I	March 8, 2002	Atlas IIa	2002-011A	also TDRS 9
TDRS J	December 4, 2002	Atlas IIa	2002-055A	also TDRS 10

References

• NASA's Goddard Space Flight Center TDRSS Official Page

Note: all references were accessed Oct. 10, 2007

External links

• NASA's TDRSS program overview page
• View current TDRS constellation (Java applet)