Space Segment
The space segment of the TDRSS constellation is the most dynamic part of the system. Even with nine satellites on orbit, the system provides support with three primary satellites, while using the rest as on-orbit spares capable of immediate usage as primaries. The original TDRSS design had two primary satellites, designated TDE, for "east", and TDW, for "west" and one on-orbit spare. 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. See Tracking and Data Relay Satellite for more details on the satellites.
Read more about this topic: Tracking And Data Relay Satellite System
Famous quotes containing the word space:
“Not so many years ago there there was no simpler or more intelligible notion than that of going on a journey. Travel—movement through space—provided the universal metaphor for change.... One of the subtle confusions—perhaps one of the secret terrors—of modern life is that we have lost this refuge. No longer do we move through space as we once did.”
—Daniel J. Boorstin (b. 1914)