Operational Use of the Hadamard Variance in GPS

Steven T. Hutsell, Wilson G. Reid, Lt Jeffrey D. Crum, Lt H. Shawn Mobbs, James A. Buisson

Abstract: With upcoming GPS Block IIR hunches scheduled, rubidium clock estimation will require more attention than ever before during the next decade of GPS operations. GPS Master Control Station (MCS) estimation architecture relies on a three-state polynomial clock model, which does not include a time-variant decay parameter for frequency drift. Since current GPS rubidium frequency standards exhibit significant time-dependent frequency drift changes, the MCS is compelled to make precise utilization of the random run process noise parameter, known as q3. The work of various scientists over the past three decades has shown the Hadamard variance to converge for random run FM. At PTTI '95, the 2d Space Operations Squadron (2 SOPS) introduced an algorithm that presented a simple, convergent polynomial relationship between the Hadamard variance and the MCS's Kalman filter process noise parameters. Until recently, however, neither the Hadamard variance nor the Hadamard-Q equation had actually been put to use in GPS. The Naval Research Laboratory (NRL) has now created analysis software designed to employ the Hadamard variance in their GPS clock analyses, to supplement their already existing software, which makes use of the Allan variance. This paper presents results of the NRL analysis using both the Allan and Hadamard variances for several operational GPS rubidium frequency standards, as well as results from the recent operational use of the Hadamard-Q equation, by 2 SOPS personnel, based on the NRL analysis data.
Published in: Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting
December 3 - 5, 1996
Hyatt Regency Reston Town Center
Reston, Virginia
Pages: 201 - 214
Cite this article: Hutsell, Steven T., Reid, Wilson G., Crum, Lt Jeffrey D., Mobbs, Lt H. Shawn, Buisson, James A., "Operational Use of the Hadamard Variance in GPS," Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 1996, pp. 201-214.
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