The In-Flight Frequency Behavior of Two Ultra-Stable Oscillators Onboard the New Horizons Spacecraft

J. Robert Jensen and Gregory Weaver

Abstract:	The New Horizons spacecraft has been on its extensive journey to Pluto, Charon, and the Kuiper Belt since January 2006. New Horizons uses two ultra-stable quartz oscillators as on-board references for radio science and the communications transceiver. One USO is configured as primary and the other is maintained in a “warm-boot” backup mode. The implementation of the transceiver for noncoherent navigation provides the opportunity for precise determination of the intrinsic USO frequency behavior during travel through deep space. In this paper, we report on the frequency behavior observed since launch. We show the effects of general and special relativity, including the Shapiro delay, and present the differences in the spacecraft reference frequency history when observed from different frames of reference. Both USO frequency behaviors demonstrated distinct interaction with Jupiter’s radiation belt during the period prior to closest approach in February 2007. The frequency drifts are -1.33 × 10-11/ day and +0.98 × 10-11/day, with each USO demonstrating a slight decrease in drift rate from that determined immediately after launch.
Published in:	Proceedings of the 39th Annual Precise Time and Time Interval Meeting November 27 - 29, 2007 Hyatt Regency Long Beach Long Beach, California
Pages:	79 - 94
Cite this article:	Jensen, J. Robert, Weaver, Gregory, "The In-Flight Frequency Behavior of Two Ultra-Stable Oscillators Onboard the New Horizons Spacecraft," Proceedings of the 39th Annual Precise Time and Time Interval Meeting, Long Beach, California, November 2007, pp. 79-94.
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