FedStat Obit Determination: Duty Cycle Operations and Orbit Accuracies

Yanming Feng

Abstract:	Techniques of Low Earth Orbiter (LEO) real time track-ing and Precise Orbit Determination (POD) using a flight GPS receiver have been well established over the past several years. A large number of GPS flight experiments have demonstrated that GPS can meet all of those needs for the most dynamically unpredictable flight vehicles with continuous tracking of GPS satellites and accuracy requirements for precise applications. However, unlike many other GPS-based Low Earth Orbiters, the flight GPS receiver on board FedSat would normally operate in duty-cycle mode, eg., 2-by-10 minutes per orbit (100.9 minutes per cycle) due to the strict limitation of power supply onboard the satellite, although it may occasionally turn to continuous operation for precise orbit experiments. Knowing the achievable orbit accuracy under specific op-eration conditions and processing modes is of primary concern to the system operators. In addition, because a filtering processing is unlikely to proceed on-board the FedSat, we must use the flight GPS data downlinked to the ground station each day to compute and predict the orbit into future for typically 24 hours for real time op-erational use. Hence, the effect of duty cycle operation on the predicted orbit accuracy is also of our interest. This paper will experimentally demonstrate the depend-ence of LEO orbit accuracies on different operation sce-narios through simulation studies for the FedSat orbit and numerical analysis for Topex/Poseidon GPS data avail-able for 23 June 1995. Results of simulation for FedSat orbit show that with duty-cycle operation of 2-by-10 min-utes per orbit, the 3D rms overall orbit accuracy of better than 20 m can be expected in a 24 h period of prediction. When FedSat turns to continuous operation, this accuracy can be improved to better than 10m. Results from Topex/ Poseidon GPS precise orbit determination show that the orbit accuracy of centimetre level can be still achieved, although an accuracy degradation to a factor of about 2 also occurs, if the data of 10 min per 50 min is chosen for processing.
Published in:	Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999) September 14 - 17, 1999 Nashville, TN
Pages:	445 - 450
Cite this article:	Feng, Yanming, "FedStat Obit Determination: Duty Cycle Operations and Orbit Accuracies," Proceedings of the 12th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1999), Nashville, TN, September 1999, pp. 445-450.
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