Composite USO/CSAC timekeeping system

Weaver, Gregory; Miranian, Mihran; Garstecki, Jeffrey F.

doi:10.1109/aero.2012.6187111

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…In recent years, due to the high data rates required to be transferred in communication networks, the demand for high accuracy satellite navigation systems and the development of high resolution radars and clocks with very high precision are required. Stable oscillators, including atomic ones like rubidium and even cesium atomic, are often used in communication and navigation facilities [1][2][3][4][5][6]. In addition to the above applications, many other electronic systems require frequency generators.…”

Section: Introductionmentioning

confidence: 99%

A New Approach for the Characterization of Nonstationary Oscillators Using the Wigner-Ville Distribution

Levy

Pinchas

Pinhasi

2018

Mathematical Problems in Engineering

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Oscillators and clocks are affected by physical mechanisms causing amplitude fluctuations, phase noise, and frequency instabilities. The physical properties of the elements composing the oscillator as well as external environmental conditions play a role in the characteristics of the oscillatory signal produced by the device. Such instabilities demonstrate frequency drifts and modulation and spectrum broadening and are observed to be nonstationary processes in nature. Most of tools which are being used to measure and characterize oscillator stability are based on signal processing techniques, assuming time invariance during a temporal window, during which the signal is assumed to be stationary. This paper proposes a new time-frequency metric for the characterization of frequency sources. Our technique is based on the Wigner-Ville distribution, which extends the spectral measures to consist of the temporal nonstationary behavior of the processes affecting the accuracy of the clock. We demonstrate the use of the technique in the characterization of phase errors, frequency offsets, and frequency drift of oscillators.

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Section: Introductionmentioning

confidence: 99%

A New Approach for the Characterization of Nonstationary Oscillators Using the Wigner-Ville Distribution

Levy

Pinchas

Pinhasi

2018

Mathematical Problems in Engineering

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“…These devices provide very good stability for timeframes of a few hours (Cash et al 2018;Fernández et al 2017), with very low power (1/8 W) and a small form-factor, and they are relatively inexpensive (< $10 k). However, CSACs alone do not provide sufficient long-term stability without external synchronization (Weaver et al 2012;Bagala et al 2016aBagala et al , 2016b. The original SA.45 MicroSemi CSACs also had relatively poor stability for timeframes less than 100 s, and have much higher phase noise than less expensive crystal oscillators.…”

Section: System Clocksmentioning

confidence: 99%

Design of a high-stability heterogeneous clock system for small satellites in LEO

2021

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We describe our investigation into the performance of low-power heterogeneous timing systems for small satellites, using real GPS observables from the GRACE Follow-On mission. Small satellites have become capable platforms for a wide range of commercial, scientific and defense missions, but they are still unable to meet the needs of missions that require precise timing, on the order of a few nanoseconds. Improved low-power onboard clocks would make small satellites a viable option for even more missions, enabling radio aperture interferometry, improved radio occultation measurements, high altitude GPS navigation, and GPS augmentation missions, among others. One approach for providing improved small satellite timekeeping is to combine a heterogeneous group of oscillators, each of which provides the best stability over a different time frame. A hardware architecture that uses a single-crystal oscillator, one or more Chip Scale Atomic Clocks (CSACs) and the reference time from a GPS receiver is presented. The clocks each contribute stability over a subset of timeframes, resulting in excellent overall system stability for timeframes ranging from less than a second to several days. A Kalman filter is used to estimate the long-term errors of the CSACs based on the CSAC-GPS time difference, and the improved CSAC time is used to discipline the crystal oscillator, which provides the high-stability reference clock for the small satellite. Simulations using GRACE-FO observations show time error standard deviations for the system range from 2.3 ns down to 1.3 ns for the clock system, depending on how many CSACs are used. The results provide insight into the timing performance which could be achieved on small LEO spacecraft by a low power timing system.

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Composite USO/CSAC timekeeping system

Cited by 2 publications

References 9 publications

A New Approach for the Characterization of Nonstationary Oscillators Using the Wigner-Ville Distribution

A New Approach for the Characterization of Nonstationary Oscillators Using the Wigner-Ville Distribution

Design of a high-stability heterogeneous clock system for small satellites in LEO

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