PulChron: A Pulsar Time Scale Demonstration for PNT systems

Piriz, R.; Garbin, Esteban; Roldan, P.; Keith, Michael; Shaw, B.; Shemar, S. L.; Burrows, Kathryn; Davis, John; Binda, S.

doi:10.33012/2019.16753

Cited by 9 publications

(4 citation statements)

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“…XPNAV timekeeping utilizes the stability of pulsar rotation to maintain the onboard clock accuracy. The longterm stability of pulsar rotation is comparable to the currently used timescale International Atomic Time (Rawley et al, 1987) and supports the implementation of a new timescale (Chen, 2018;Piriz et al, 2019). Such a timescale is capable of utilizing the short-and long-term stabilities of a hydrogen maser and the observed pulsar rotation, respectively.…”

Section: Introductionsupporting

confidence: 54%

“…We propose three types of clocks with different stability properties. Clock 1 corresponds to a highly stable hydrogen maser in a laboratory environment (Piriz et al, 2019), Clock 2 is an ultra-stable oscillator (USO) used for lunar exploration mission LRO (Dirkx, 2015), and Clock 3 is the USO that is commonly used in near-Earth space missions (Winternitz et al, 2018). Table 4 provides the parameters for the three clocks.…”

Section: Satellite Clock Modelmentioning

confidence: 99%

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Autonomous orbit determination and timekeeping in lunar distant retrograde orbits by observing X‐ray pulsars

et al. 2021

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A server satellite that is parked in a stable distant retrograde orbit (DRO) in the vicinity of the Moon can provide navigation service for satellites in the Earth-Moon system. In this study, X-ray pulsar navigation (XPNAV) is investigated to determine the server's orbital position and velocity, and maintain its onboard timing autonomously to ensure the autonomy of the server. First, the feasibility and potential advantages of XPNAV in DRO are analyzed qualitatively based on the unique properties of DRO: long-term orbital stability and short-term, nearly uniform-velocity rectilinear motion. Second, high-fidelity X-ray photon timestamps are simulated to serve as the original measurements for XPNAV. A classical extended Kalman filter is used to estimate the orbital states (i.e., position and velocity) and the clock timing of the satellite in DRO, wherein the pulse phase and Doppler frequency are estimated as intermediate measurements. Finally, Monte Carlo simulations are conducted to assess the variation in the XPNAV performance with the DRO orbital period, clock noise, and detector effective area. The simulation results show that XPNAV in DRO can achieve considerably improved position accuracy than that in low Earth orbit using the same hardware while maintaining the long-term stability of the satellite onboard clock, thus demonstrating the capability of XPNAV to be used in an operational spaceflight mission around or beyond the Moon.

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Section: Introductionsupporting

confidence: 54%

Section: Satellite Clock Modelmentioning

confidence: 99%

Autonomous orbit determination and timekeeping in lunar distant retrograde orbits by observing X‐ray pulsars

et al. 2021

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“…Pulsar time has the potential to apply in the area of autonomous navigation in deep space and the work of time-keeping. For example, a pulsar-aided clock by combining pulsar time and Galileo System Time (GST) has been proposed recently (Piriz et al 2019). The aim of the aided clock is to achieve a high standard time scale in short-term and long-term.…”

Section: The Effects Of Observational Strategies On Predictions Of Pu...mentioning

confidence: 99%

The influence of the observational strategies of pulsar timing on the properties of pulsar clocks

Zhang

Tong

Zhao

et al. 2020

Res. Astron. Astrophys.

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Pulsars are very stable spinning stars, which have the potential to application in the work of time-keeping and autonomous navigation in deep space. For time application, an individual pulsar can be regarded as a clock. The accuracy and stability of a pulsar clock are mainly determined by various timing noises and the measurement errors; however, they would be affected by the concrete observational strategy. Taking four millisecond pulsars from the first data released by International Pulsar Timing Array (IPTA) as an example, we investigated the influences of different observational strategies on the properties of pulsar clocks by removing some data in various ways. We find that the long-term stabilities of pulsar clocks are nearly not affected by increasing the observational cadence with a fixed time span. It is also found that the capabilities of prediction by pulsar clocks are also hardly affected by different observational strategies, which is reflected by both the stable weighted root-mean-square (wrms) and the stability of the resulting pre-fit timing residuals, unless the data span is too short or the data period is too far from the start of prediction.

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“…Millisecond pulsars (MSPs), with brilliant spinning stability, are the most stable natural frequency sources that provide a way to investigate the performance (especially in the long term) of timescales based on quantum theory in the solar system. In history, many authors (Petit & Tavella 1996;Rodin 2006Rodin , 2008Hobbs et al 2012Hobbs et al , 2020Rodin & Fedorova 2018;Píriz 2019) have proposed various methods to construct the ensemble pulsar timescale (EPT). An effective EPT can keep a lower noise level compared with the pulsar timescale (PT) established by a signal MSP and hence it behaves more stable.…”

Section: Introductionmentioning

confidence: 99%

An Improved Wiener Filtration Method for Constructing the Ensemble Pulsar Timescale

Zhang,

Tong,

Yang

2024

ApJ

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An improved Wiener filtration (WF) method for constructing the ensemble pulsar timescale (EPT) is proposed to solve the existing problems in the WF algorithm. The improvements consist of three parts: (i) adjusting the cross-power spectral density (PSD) and PSD estimated by the weighted average (WA) algorithm by the concept of the energy upper limit; (ii) combining the cross-PSD and WA PSD to form a different signal modulus for the filtration of residuals of different noise levels; and (iii) setting a weight for each residual by a more general algorithm based on the concept of effective power. We use this improved WF method to construct the EPT by both simulated data and observational data from the second data release of the International Pulsar Timing Array. The results from the simulated data indicate this improved WF can successfully suppress the noise level and reform the common signal. For observational data, this method also successfully detects the fluctuations of International Atomic Time (TAI) and local atomic time TA(NTSC). A stability analysis shows that an EPT will have the potential to reveal the instability of TAI on a scale longer than 7 yr. This improved WF method can also be used to detect and monitor the noise in pulsar timing residuals inversely, by using multiple atomic time standards, which can in turn improve the EPT.

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PulChron: A Pulsar Time Scale Demonstration for PNT systems

Cited by 9 publications

References 0 publications

Autonomous orbit determination and timekeeping in lunar distant retrograde orbits by observing X‐ray pulsars

Autonomous orbit determination and timekeeping in lunar distant retrograde orbits by observing X‐ray pulsars

The influence of the observational strategies of pulsar timing on the properties of pulsar clocks

An Improved Wiener Filtration Method for Constructing the Ensemble Pulsar Timescale

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