The Tracking and Data Relay Satellite (TDRS)

Abstract

In 1982, NASA plans to launch the first TDRS into geosynchronous equatorial orbit using the Shuttle and the Inertial Upper Stage. Each TDRS will carry a highly flexible multifunction communication payload that services TDRS System users or Advanced Westar (AW) users while providing concurrent Westar C-band service. In the TDRS mode, two 4.9 meter diameter gimballed antennas provide single access S-band and/or K-band service, and a 30 element phased array provides 20 channel multiple access S-band service. Space Ground Link (SGL) communication with the White Sands Ground Station users a 2 meter gimballed K-band antenna. In the AW mode, K-band service is provided by a spacecraft switched TDMA transponder through four spot beams (two using the 4.9 meter antennas and two using separate feeds on the SGL antenna) and three area coverage beams (two from a body fixed dual feed antenna and one from an area feed assembly on the SGL antenna). C-band service is provided by a standard 12 channel Westar payload with its own 1.5 meter antenna. Nominal deployment is four satellites: two dedicated TDRS are at 41° and 171°W, and the AW and spare (or shared) satellites are at 91° and 83°W, respectively. TDRS is a 5000 pound satellite with momentum wheels for 3-axis control and a hydrazine reaction control system for momentum dumping and stationkeeping.