GPS block IIR clocks in space: current performance and plans for the future

Phelan, J.; Dass, Todd; Freed, Gerald; Rajan, John; D'Agostino, J.; Epstein, Marvin

doi:10.1109/freq.2005.1573897

Cited by 9 publications

(2 citation statements)

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“…This quickly transitions to a power-law which varies as τ −1 , consistent with flicker phase noise for intervals up to several thousand seconds. This high-frequency noise behavior of the IIR and IIR-M satellites has been attributed to phase meter noise (Wu 1997;Petzinger et al 2003;Phelan et al 2006) in the Time Keeping System (TKS). The TKS phase meter comparator operates at 600 MHz with samples every 1.5 s, each having an accuracy estimated to be 1.67 ns.…”

Section: Gps Sub-daily Clock Stabilitiesmentioning

confidence: 99%

Characterization of periodic variations in the GPS satellite clocks

2008

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Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std. Z39.18Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. The clock products of the International Global Navigation Satellite Systems (GNSS) Service (IGS) are used to characterize the timing performance of the GPS satellites. Using 5-minute and 30-second observational samples and focusing only on the sub-daily regime, approximate power-law stochastic processes are found. The Block IIA Rb and Cs clocks obey predominantly random walk phase (or white frequency) noise processes. The Rb clocks are up to nearly an order of magnitude more stable and show a flicker phase noise component over intervals shorter than about 100 s. Due to the onboard Time Keeping System in the newer Block IIR and IIR-M satellites, their Rb clocks behave in a more complex way: as an apparent random walk phase process up to about 100 s then changing to flicker phase up to a few thousand seconds. Superposed on this random background, periodic signals have been detected in all clock types at four harmonic frequencies, n × (2.0029 ± 0.0005) cycles per day (24 hr UTC), for n =1, 2, 3, and 4. The equivalent fundamental period is 11.9826 ± 0.0030 hours, which surprisingly differs from the reported mean GPS orbital period of 11.9659 ± 0.0007 hours by 60 ± 11 s. We cannot account for this apparent discrepancy but note that a clear relationship between the periodic signals and the orbital dynamics is evidenced for some satellites by modulations of the spectral amplitudes with eclipse season. All four harmonics are much smaller for the IIR and IIR-M satellites than for the older blocks. Awareness of the periodic variations can be used to improve the clock modeling, including for interpolation of tabulated IGS products for higher-rate GPS positioning and for predictions in real-time applications. This is especially true for high-accuracy uses, but could also benefit the standard GPS operational products. The observed stochastic properties of each satellite clock type are used to estimate the growth of interpolation and prediction errors with time interval. REPORT TYPE 1. REPORT DATE (DD-MM-YYYY) TITLE AND SUBTITLE AUTHOR(S) PERFORMING ORGANIZATION REPORT NUMBER PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S ACRONYM(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S REPORT NUMBER(S)

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Section: Gps Sub-daily Clock Stabilitiesmentioning

confidence: 99%

Characterization of periodic variations in the GPS satellite clocks

2008

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“…Since frequency drifts are arisen over time in GPS satellite atomic clocks due to natural aging, the clocks involve clock bias with respect to the GPS Time (GPST), which behaviors have characteristics of a second order polynomial in the long term [6]. In addition, sudden anomalies such as phase jumps, frequency jumps, frequency increasing, etc., may also occur.…”

Section: Introductionmentioning

confidence: 99%

An Approach for GPS Clock Jump Detection Using Carrier Phase Measurements in Real-Time

Heo¹,

Cho²,

Heo³

2012

Journal of Electrical Engineering and Technology

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-In this study, a real-time architecture for the detection of clock jumps in the GPS clock behavior is proposed. GPS satellite atomic clocks have characteristics of a second order polynomial in the long term showing sudden jumps occasionally. As satellite clock anomalies influence on GPS measurements which could deliver wrong position information to users as a result, it is required to develop a real time technique for the detection of the clock anomalies especially on the real-time GPS applications such as aviation. The proposed strategy is based on Teager Energy operator, which can be immediately detect any changes in the satellite clock bias estimated from GPS carrier phase measurements. The verification results under numerous cases in the presence of clock jumps are demonstrated.

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Autonomous clock ensemble algorithm for GNSS applications

Coleman

Beard

2020

NAVIGATION

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GPS block IIR clocks in space: current performance and plans for the future

Cited by 9 publications

References 1 publication

Characterization of periodic variations in the GPS satellite clocks

Characterization of periodic variations in the GPS satellite clocks

An Approach for GPS Clock Jump Detection Using Carrier Phase Measurements in Real-Time

Autonomous clock ensemble algorithm for GNSS applications

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