Tracking and Data Relay Satellite System
The system was designed to replace an existing network of ground stations that had supported all of NASA's crewed 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.
[1] In 2022 NASA announced that it would gradually phase out the TDRS system and rely on commercial providers of communication satellite services.
[2] To satisfy the requirement for long-duration, highly available space-to-ground communications, NASA created the Spacecraft Tracking and Data Acquisition Network (STADAN) in the early 1960s.
Consisting of parabolic dish antennas and telephone switching equipment deployed around the world, the STADAN provided space-to-ground communications for approximately 15 minutes of a 90-minute orbit period.
[citation needed] With the creation of the Space Shuttle in the mid-1970s, a requirement for a higher performance space-based communication system arose.
Since the entire network consisted of ground stations spread around the globe, these sites were vulnerable to the political whims of the host country.
In order to maintain a high-reliability rate coupled with higher data transfer speeds, NASA began a study[when?]
[citation needed] As of July 2009[update], TDRS project manager is Jeff J. Gramling, NASA Goddard Space Flight Center.
[4] Robert P. Buchanan, Deputy Project Manager, retired after 41 years at NASA with TDRS as one of final missions.
WSGT and STGT are geographically separated and completely independent of one another, while retaining a backup fiber-optic link to transfer data between sites in case of emergency.
The system architects moved the remaining SGLT to Guam to provide full network support for the satellite covering the ZOE.
It is a cost-effect wide area network telecommunications service for transmission of data, video, and voice for all NASA enterprises, programs and centers.
This part of the STDN consists of infrastructure and computers dedicated to monitor network traffic flow, such as fiber optic links, routers and switches.
Service control and assurance supports functions of real-time usage, such as receipt, validation, display and dissemination of TDRSS performance data.
Attitude determination computes sets of parameters that describe a spacecraft's orientation relative to known objects (Sun, Moon, stars or Earth's magnetic field).
The surge in user requirements during the 1980s allowed NASA to expand the network with the addition of more satellites, with some being co-located in a particularly busy orbital slot.
Programs such as the Hubble Space Telescope and LANDSAT relay their observations to their respective mission control centers through TDRSS.
[8] Almost twenty years later, on November 23, 2007, an on-line trade publication noted, "While NASA uses the (TDRSS) satellites to communicate with the space shuttle and international space station, most of their bandwidth is devoted to the Pentagon, which covers the lion's share of TDRSS operations costs and is driving many of the system's requirements, some of them classified.
