Real-Time GEO Orbit Determination Using TOPSTAR 3000 GPS Receiver

Abstract

Operational satellites for telecommunication and earth observation are generally designed for either low-earth orbit (LEO) or geostationary orbit (GEO) missions. LEO missions cover the range of 200 -2,000 km in altitude and 0 -180 deg in inclination, while GEO missions are at 36,000 km altitude and 0 deg inclination.For LEO missions, GPS receivers are now considered valuable equipment for accurate real-time localization and on-board time transfer. Most of the LEO satellites to be launched during the next 5 years incorporate GPS receivers. The use of GPS receivers for GEO missions, however, has been delayed for both technical and operational reasons. The technical reasons relate to unfavorable GPS geometry and signal power encountered by the receiver at high altitude, while the operational reasons relate to the fact that localization and time transfer are easily performed from the ground station, which remains in permanent view of the GEO spacecraft.From an operational point of view, interest in the use of GPS receivers for GEO missions becomes stronger when one considers autonomous orbit control: the station-keeping maneuvers are performed autonomously by the spacecraft itself, instead of being controlled from the ground station. This technique is expected to become mature in the next few years, especially given the growing interest in electric propulsion. Autonomous control of orbit requires that the spacecraft incorporate equipment for localization and time transfer, such as a GPS receiver.These issues are discussed in this paper, using for illustration the test results obtained with a TOP-STAR 3000 GPS receiver. First, the GPS receiver is briefly described, with focus on two features relevant for GEO navigation -accurate orbital filtering and good signal acquisition sensitivity. The most significant parameters for GEO missions are discussed: link budget and geometry, possible use of the side lobes of the transmitter antenna, ionospheric effects, and the stability of the receiver local clock. Test results obtained with the receiver connected to a radio frequency (RF) multichannel simulator are presented. The final section addresses the topic of GEO autonomous orbit control with GPS, especially when the spacecraft is using electric propulsion. In this situation, station-keeping thrusts are quasipermanent and act as a disturbing force for the GPS receiver. Simulation test results are presented for the station-keeping configuration of the STENTOR satellite. 169Real-Time GEO Orbit Determination Using TOPSTAR 3000 GPS Receiver

Tiny GPS receiver for space application

“…By contrast, GPS receivers that are deployed on satellites typically have a mass of several kilograms, power consumption of over 10 W, and a cost that ranges from $100,000 to upwards of million dollars [2][3][4]. GPS receivers for deployment on satellites are developed and manufactured by satellite manufacturers by using aerospace components for space-only applications, in a manner virtually separate from consumer electronics GPS receiver makers, with the result that the developmental cost is allocated to satellite-deployed devices that are manufactured only in limited quantities.…”

“…The GPS signal level that is output from the signal generator is approximately -120 dBm. After being amplified by a 30-dB amp (with a maximum noise index of 10 dB), the GPS signal is input into the GPS receiver through a 3-dB coupler (3) and a coaxial cable with an approximate loss factor of 2 dB. The precision of the GPS simulator signal in RMS value has a pseudo-range of ±0.01 m, and a pseudo-range rate of change of ±0.001 m/s [14].…”

Miniature Space GPS Receiver by Means of Automobile-Navigation Technology

“…The key technologies for their miniaturization are highly integrated circuits for receiver functions, based upon mass productions. 1,2 On the other hand, space-borne GPS receivers are as heavy as several kg and power consumption is as much as 10 W. [3][4][5] In general, the space-borne GPS receivers are manufactured with use of space-qualified parts dedicated for space application, separately from commercial GPS receiver manufacturing. This leads to expensive development cost and large size of instruments.…”

Development of a Miniature Multifunctional GPS Receiver for Space Applications

“…A new spaceborne GPS receiver corresponding to these functions should thus be developed. Overseas manufacturers SURRY and ALCATEL supply SGR 1) and TOP-STAR 3000, 2) but both are single-frequency (L1) receivers.…”