Tracking and Data Relay Satellite System Performance

Abstract

The system performance of the Tracking and Data Relay Satellite System (TDRSS) as supplied by Western Union Space Communications, Inc., to NASA is described. TDRSS provides a flexible, responsive communication and tracking service to earth orbiting satellites below an altitude of 12,000 kilometers. Forward link command service to a user satellite is provided with a communication channel having characteristics and radiated power controlled to support data rates from 100 bits per second to 25 Megabits per second. Return link telemetry service from a user satellite is provided over a wide range of data rates from 100 bits per 5 second to 300 Megabits per second with bit error rate performance exceeding 1 x 10⁻⁵. The configuration of the TDRSS satellites and ground communications equipment are computer controlled to respond quickly to user requests for support changes within a service period. Changes can generally be accomodated within 15 seconds after the receipt of a request. Equipment is available within the TDRSS which simulates a user spacecraft and can be inserted into the communication link to verify the adequacy of the TDRSS performance. Computer controlled test equipment will measure and report the performance of key parameters within a 10-minute period. Additionally, the system provides commercial service in the C and K-bands to fulfill the needs of the Western Union Telegraph Company and the American Satellite Corporation on a shared basis with the NASA services. The commercial service performance is briefly described.