According to NASA:
The Tracking and Data Relay Satellites (TDRS) comprise the communication satellite component of the Tracking and Data Relay Satellite System (TDRSS). TDRSS is a communication signal relay system which provides tracking and data aquisition services between low-earth orbiting spacecraft and control and/or data processing facilities. The system is capable of transmitting to and receiving data from spacecraft over at least 85% of the spacecraft's orbit.
The TDRSS space segment consists of six on-orbit Tracking and Data Relay Satellites located in geosynchronous orbit. Three TDRSs are available for operational support at any given time. The operational spacecraft are located at 41°, 174° and 275° West longitude. The other TDRSs in the constellation provide ready backup in the event of a failure to an operational spacecraft and, in some specialized cases, resources for target of opportunity activities.
The TDRSS ground segment is located near Las Cruces, New Mexico, known as the White Sands Complex. Forward data is uplinked from the ground segment to the TDRS and from the TDRS to the spacecraft. Return data is downlinked from the spacecraft via the TDRS to the ground segment and then on to the designated data collection location.
The Tracking and Data Relay Satellite (TDRS) Project is providing follow-on and replacement spacecraft necessary to maintain and expand the Space Network. The contract to build three additional TDRS spacecraft, known as TDRS K, L, and M, was awarded to Boeing Space Systems in December 2007. TDRS K launched January 30, 2013, and TDRS L launched January 23, 2014. TDRS M's launch readiness date is scheduled for 2015. The contract also has options for one additional spacecraft, TDRS N. In addition to building the TDRS K, L, and M spacecraft, the contract also includes the modifications to the White Sands Complex (WSC) ground system required to support these new spacecraft.
The TDRS Project, established in 1973, is responsible for the development, launch, and on-orbit test and calibration of TDRS spacecraft. There have been four procurements of TDRS spacecraft, which include the Basic Program (TDRS F1-F6), the Replacement Program (TDRS F7), the TDRS H,I,J Program, and the TDRS K,L,M Program. TDRS Flight 7 was a replacement for Flight 2, which was lost aboard Challenger in 1986. The first seven spacecraft (TDRS F1-F7) are referred to as the First Generation, the H,I,J series are called the Second Generation, and the K,L,M series are known as the Third Generation. TDRS F1-7 spacecraft were built by TRW (now Northrop Grumman) in Redondo Beach, CA. The TDRS F8-10 (H,I,J) spacecraft were built by Hughes (now Boeing) in El Segundo, CA.
The NASA Space Network consists of the on-orbit telecommunications TDRS satellites, placed in geosynchronous orbit, and the associated TDRS ground stations, located in White Sands, New Mexico and Guam. The TDRS constellation is capable of providing nearly continuous high bandwidth (S, Ku, and Ka band) telecommunications services for expandable launch vehicles and user spacecraft in low Earth orbit. Examples include: the Hubble Space Telescope, the Earth Observig Fleet and the International Space Station. The TDRS System is a basic agency capability and a critical national resource.
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Paired Frequency Bands |
| Paired Bands | Use | Service | Table |
| 2025.8 - 2117.9 MHz | S-band Single Access (TDRS transmit) | Space Operation | F |
| 2200 - 2300 MHz | S-band Single Access (TDRS receive) | Space Research (space-to-Earth) | F |
| 2103.4 - 2109.4 MHz | S-band Multiple Access (TDRS transmit) | Space Operation | F |
| 2285 - 2290 MHz | S-band Multiple Access (TDRS receive) | Space Operation (space-to-Earth) | F |
| 13.4 - 14.05 GHz | TDRS downlink | Space Research | F |
| 14.6 - 15.25 GHz | TDRS uplink | Space Research (Earth-to-space) | F |
| 13.75 - 13.8 GHz | Ku-band Single Access (TDRS transmit) | Space Operation | F |
| 14.891 - 15.116 GHz | Ku-band Single Access (TDRS receive) | Space Research (space-to-Earth) | F |
Frequencies |
| Frequency | Bandwidth | Use | Service | Table |
| 2036 MHz | - | TDRS command uplink | Space Operation | F |
| 2211 MHz | - | TDRS telemetry downlink | Space Operation | F |
| 13.731 GHz | - | TDRS telemetry downlink | Space Operation | F |
| 14.785 GHz | - | TDRS command uplink | Space Operation | F |
| 15.15 GHz | - | TDRS reference frequency signal uplink | Space Operation | F |
Frequency Bands |
| Band | Use | Service | Table |
| 25.25 - 27.5 GHz | Ka-band Single Access (TDRS receive) | Space Research | F |
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