Space Network (SN) is a NASA program that combines space and ground elements to support spacecraft communications in Earth vicinity. The SN Project Office at Goddard Space Flight Center (GSFC) manages the SN, which consists of:
Tracking and Data Relay Satellite (TDRS) currently consists of first generation (F1-F7), and second generation (F8-F10) satellites.
The space segment of the SN consists of up to six operational relay satellites in geosynchronous orbit. These communications satellites are allocated longitudes for relaying forward and return service signals to and from customers, any entity with an Earth-orbiting satellite that has an agreement with SN to use its communications services, for data transfer and tracking. An additional TDRS, F1, provides dedicated support to the National Science Foundation (NSF) through the use of the WSC Alternate Relay Terminal (WART). Additional spare TDRSs may be in geosynchronous orbit.
All first generation TDRSs (F1-F7, also known as TDRS A-G) carry functionally identical payloads and all second generation TDRSs (F8-F10, also known as TDRS H-J) carry functionally identical payloads.