User spacecraft tracking, telemetry and command equipment design for the TDRSS era

The NASA TDRSS equipment and performance design characteristics are summarized. Two TDRSS will furnish tracking, telemetry, and command telecommunications services for LEO spacecraft by providing Ku- and S-band links and multiaccess capabilities. Data rates range from 0.1 bps to multihundreds of Mbps, depending on the number of users, the frequency, and the broadcast technique. Each TDRSS spacecraft has two antennas: one a 30 element array and the other a 2 m steerable ground link dish. A spread spectrum signaling technique has been implemented in order to permit the multiuser functions, although penalties were accepted in the clock rates and lengths and the data rates. The TDRSS system will give 85 percent coverage for altitudes from 160-2000 or 12,000 km, depending on the type of user.