Session
Technical Session X: Subsystems
Abstract
The HETE (High Energy Transient Experiment) satellite, a joint project between MIT Center for Space Research and AeroAstro, is a high energy gamma ray burst/X-ray/UV observatory platform. In order to provide accurate time stamping of gamma ray burst events, a clock accurate to within 100 Ils of Universal Time (UT) is required on the satellite. This paper presents a clock setting/ranging subsystem that is incorporated into the HETE telemetry system at no additional weight or power consumption. This method makes use of augmenting the data scrambler with a PN ranging code with unique words which allows accurate ranging and clock setting on the spacecraft to within 3 Ils or better of UT. This system operates at baseband and is thus independent of the modulation type or carrier frequency used on the uplink and downlink. It also does not require that the uplink and downlink frequencies bear any particular relationship to each other. Clock setting and ranging measurements are performed on command from the ground station. The clock setting/ranging mode duration is approximately 3 to 5 seconds and is terminated automatically through a satellite-ground station handshake.
HETE Telemetry Ranging Subsystem
The HETE (High Energy Transient Experiment) satellite, a joint project between MIT Center for Space Research and AeroAstro, is a high energy gamma ray burst/X-ray/UV observatory platform. In order to provide accurate time stamping of gamma ray burst events, a clock accurate to within 100 Ils of Universal Time (UT) is required on the satellite. This paper presents a clock setting/ranging subsystem that is incorporated into the HETE telemetry system at no additional weight or power consumption. This method makes use of augmenting the data scrambler with a PN ranging code with unique words which allows accurate ranging and clock setting on the spacecraft to within 3 Ils or better of UT. This system operates at baseband and is thus independent of the modulation type or carrier frequency used on the uplink and downlink. It also does not require that the uplink and downlink frequencies bear any particular relationship to each other. Clock setting and ranging measurements are performed on command from the ground station. The clock setting/ranging mode duration is approximately 3 to 5 seconds and is terminated automatically through a satellite-ground station handshake.
