Series of Satellite Encounters to Solve Autonomous Formation Assembly Problem

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T. Kormos; P. Palmer; M. Sweeting (2003), JBIS, 56, 290-298

Refcode: 2003.56.290
Keywords: satellite fly-by, J2 drift, formation flying, formation assembly

Abstract:
This paper addresses the problem of bringing two satellites on different orbital planes together and presents results of successful experiments done using two Surrey Satellite Technology Limited (SSTL) satellites: UoSat- 2 and UoSat-12. A simple linearized Keplerian model with J2 dynamics included was used for initial approxima- tion. A standard LQR controller is presented which by using the above model provides optimal along-track only firing strategy to bring the satellites within a few kilometres of each other. A high precision analytical propaga- tion determines the exact geometry and time of closest approach. As the inclinations of the above two satellites differ by more than 30 degrees, the final step of bringing the two satellites into a stable formation was obviously left out, but radio receiver data from the fly-by are presented to validate the accuracy of the method. A nonlinear least squares filter was constructed to extract orbital elements from the radio data received, thus improving our knowledge of the relative orbits of the two satellites. We have brought the two satellites at closest 7.7 km, while other encounters happened at much larger distances. Clear radio signals were received when the satellites were even 150 km apart. For selected encounters for which we have good quality radio data, we were able to confirm that our prediction was 0.451 second accurate with respect to timing and 2.29 km with respect to closest approach distance.

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