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Tracking and Data Relay Satellites (TDRS)

NASA’s Tracking and Data Relay Satellite (TDRS) provides near-continuous communication between Earth and spacecraft in low Earth orbit, enabling data relay for missions like the International Space Station and Hubble Space Telescope.

Credits: NASA/Dave Ryan

For more than 40 years, NASA’s Tracking and Data Relay Satellites (TDRS) have provided near-continuous, high-bandwidth communications to over 25 missions in low Earth orbit, including the Hubble Space Telescope and the International Space Station.

The TDRS fleet is made up of relay satellites that transmit signals between ground station antennas, spacecraft, and other relay satellites. Together, these satellites form a communications system that keeps missions in near-continuous contact with Earth, allowing them to transmit science, health, and location data almost instantly. Without these relays, spacecraft would lose communications whenever they moved out of view of ground antennas.

By relaying data between spacecraft and ground stations, the TDRS fleet provides near-constant communication relay links between Earth and satellites below geosynchronous orbit.

NASA/David Ryan

Real-time communications are especially critical to human spaceflight, but all spacecraft benefit from the enhanced connectivity relays provide. Today, both public and private space exploration depend on satellite relays like TDRS to bring their data back home. As of 2025, seven active TDRS satellites remain in geostationary orbit, offering continuous tracking and data relay for NASA missions.

From its inception, the TDRS fleet has revolutionized how NASA monitors and controls its missions. While its final satellite, TDRS-13, launched in 2017, TDRS continues to influence advancements in network architecture and the space communications marketplace.

Nobel Prize-winning science, every conversation with astronauts aboard the International Space Station, each image from Hubble Space Telescope, and much more have flowed through TDRS.

Dave israel

NASA Near Space Network Chief Architect

As TDRS approaches retirement, NASA is looking to its commercial successors for communications services with greater scalability, flexibility, and innovation. Effective November 8, 2024, NASA will no longer assign new missions to the TDRS system. Existing missions, such as the International Space Station and Hubble, will continue to use TDRS until the satellites are decommissioned.

The legacy of TDRS, however, will continue to be felt in the pioneering global architecture that future commercial satellite relays will inherit.

TDRS at a Glance

Operational Since: 1983 (TDRS-1)
Orbit: Geostationary (22,300 mi/35,786 km altitude)
Total Satellites Launched: 12
Current Active Fleet: 7
Last Satellite Launched: 2017 (TDRS-13)
End of New Mission Support: November 8, 2024

A horizontal arrangement of three NASA Tracking and Data Relay Satellites (TDRS) in space, illustrating their design evolution. The left satellite represents the first generation with gold mesh antennas, the center satellite is second generation with gray mesh antennas and blue solar panels, and the right satellite is third generation with an updated configuration and streamlined structure.

The three generations of NASA’s TDRS fleet highlight four decades of advancement in the system’s near-continuous relay services.

NASA/Dave Ryan

Generations of TDRS

Generation	Launch Years	Notable Features	Status
First	1983-1995	Enabled first near-continuous contact with low Earth orbit missions	Retired or near end-of-life (TDRS-2, -5, -6, -7)
Second	2000-2002	Enhanced power and data handling	Operational (TDRS-8, -9, -10)
Third	2013-2017	Improved signal quality and Ka-band capability	Active fleet (TSRS-11, -12, -13)

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