TDRSS Ground Station Software/ADPE

Abstract

The Tracking and Data Relay Satellite System (TDRSS) provides data relay and tracking services for other (user) satellites. The ground station performs all the modulation/demodulation functions for, simultaneously, as many as 19 forward (to user spacecraft) and 32 return (from user spacecraft) data channels at K and at S-band. TDRSS is transparent to the data itself; it passes synchronized bit streams directly to/from NASA. The data channels exist on up to 4 communication satellites and are carried on 6 single access and 3 multiple access space antennas. TDRSS relay services are available 24 hours/day, 7 days/week. Individual services using a single TDRS may be maintained for up to 24 hours. Using 3 TDRS', a user satellite may be serviced continually. The TDRSS ground station is a highly automated collection of communication electronics. Automation is achieved through the use of software in a large complex of dedicated computers - 9 DEC PDP 11/70's and a dual processor Univac 1110. The software performs three major functions: * management of the TDRSS resources - spacecraft, ground antennas, demodulators, bit syncs, etc. * computation of user spacecraft tracking/trajectory data * telemetry, tracking and control of the TDRS' The software/ADPE configuration was designed to provide the responsiveness needed to support the TDRSS mission: rapid and flexible scheduling and management of equipment to provide relay to and from NASA; rapid, highly accurate trajectory and tracking computation; ground-supported autotrack for the TDRS single access antennas; simultaneous provision of TT&C functions for multiple TDRS'; and control of the behavior of the Ground Station under abnormal (failed equipment) conditions.