Autonomous Orbit Control Experience on TacSat-2 using Microcosm’s Orbit Control Kit (OCK)


Microcosm’s patented Orbit Control Kit (OCK) derives from the company’s long-term
commitment to transfer to the spacecraft, from the ground, those operations that are better performed by an on-board system. This approach will lead to efficiencies in ground operations, lower costs, and reduced system risk. The OCK technology was developed largely to reduce the burden of constellation operations by putting straightforward, deterministic, and repetitive functions onboard the spacecraft. The results from the TacSat-2 mission demonstrate that the technology also provides a capability not previously available: controlling a satellite’s in-track position (within about +1 km for low Earth orbit missions) months, if not years, in advance with great ease and accuracy with simple geometric calculations, rather than complex orbital mechanics and
propagation. This capability allows all system components to know factors such as the
current locations of all satellites in the system, location and direction to the nearest
satellite, parameters of current or future ground passes, when satellite transitions occur,
and when a given satellite will be over any location as far in the future as desired. For
constellations, the technology eliminates the need for re-phasing as the in-track position
is maintained with sufficient precision, along with the altitude, and is a major contributor
to collision avoidance.
Microcosm has now updated and enhanced the OCK software for a flight demonstration
on TacSat-2, which was launched in December 2006. The results have substantiated those from the previous University of Surrey UoSat-12 mission (1999), which showed that after only a few days, the technology was capable of maintaining in-track position to about +1 km. In this paper the authors will describe the basic concept of autonomous orbit control and the implementation that has now been flight proven on two space missions. Next will be a discussion of the results of the multiple OCK experiments that have occurred on the TacSat-2 mission.

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Plam, Y., R. Van Allen, T. Bauer and J. Wertz. 31st Annual AAS Guidance and Control Conference, Breckenridge, CO. February 1–6, 2008.