Revised Block II/IIA Lifetime Predictions and the Impact on Block IIR/IIF Replenishment Planning

James. M. Womack

Abstract:	Revised lifetime predictions based on on-orbit experience from reaction wheels, clocks, and solar array performance are developed for Block II/IIA satellites. The revised lifetime predictions extend the baseline Block IIA mean mission duration (MMD) from 6.75 years to 8.45 years. Existing production and launch schedules for future Block IIR/IIF satellites evaluated using the new lifetime predictions indicate that there is high near-term availability of 24 satellites, which drops in later years. By stretching the planned Block IIR launch schedule and maintaining the existing Block IIF production schedule, the availability of 24 satellites can be maintained above 95%. The revised lifetime predictions for Block II/IIA show that the Block IIF production schedule is on track, and contrary to previous assessments, there should be minimal risk in maintaining 24 satellites on-orbit.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	381 - 390
Cite this article:	Womack, James. M., "Revised Block II/IIA Lifetime Predictions and the Impact on Block IIR/IIF Replenishment Planning," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 381-390.
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