Stability improvement of an operational two-way satellite time and frequency transfer system

Huang, Yen-Hua; Fujieda, Miho; Takiguchi, Hiroshi; Tseng, Wen-Hung; Tsao, Hen‐Wai

doi:10.1088/0026-1394/53/2/881

Cited by 32 publications

(22 citation statements)

References 28 publications

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“…Currently, primary microwave clocks are connected via satellites [36] in the microwave domain by the existing GNSS infrastructure [122] or dedicated two-way time and frequency transfer (TWTFT) links [123][124][125]. Demonstrated frequency transfer uncertainties of existing microwave links (MWLs) reach into the 10 −16 range after averaging times of days [122,126] and into the 10 −17 range after averaging times of weeks with integer ambiguity resolution [122], and demonstrated time transfer uncertainties lie in the nanosecond region [125].…”

Section: Free Space-time and Frequency Linksmentioning

confidence: 99%

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

Alonso,

Alpigiani,

Altschul

et al. 2022

Preprint

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We summarize the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible roadmap for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with ESA and national space and research funding agencies. research areas. As anticipated for a Europe-based event, about 80% of the registrations are from European countries, as seen in the lower right panel of Fig. 1, but there is also significant North American and Asian participation.This community provides the backbone for long-term planning and the support needed to see the challenging cold atom missions foreseen in the road-map through to their successful completions. The participants display an excellent and diverse mix of expertise, building an outstanding basis for the success of the workshop and the development of the corresponding road-map, which defines possible interim and long-term scientific goals and outlines technological milestones. Section 2 is an introduction to our document, Sections 3 to 5 discuss our main science themes, namely atomic clocks, Earth Observation and fundamental physics, Section 6 discusses the technology developments required before quantum sensors can be deployed in space, Section 7 summarises the discussions during the Workshop, and in Section 8 we outline the corresponding Community road-map.

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Section: Free Space-time and Frequency Linksmentioning

confidence: 99%

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

Alonso,

Alpigiani,

Altschul

et al. 2022

Preprint

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“…TWSTFT has the diurnal oscillation of 0.5 ns -1 ns, which causes an inferior performance to GPS carrierphase, for an averaging time of less than 1 day. In the future, we plan to install the software-defined radio TWSTFT which may help remove the diurnal oscillation [28]. The optical-fiber link is between NIST and Alternate Master Clock (AMC, Colorado Springs, CO) using precision time protocol (PTP).…”

Section: Best Gps Carrier-phase Performance At Nistmentioning

confidence: 99%

A Study of GPS Carrier-Phase Time Transfer Noise Based on NIST GPS Receivers

Yao

Levine

2016

J. RES. NATL. INST. STAN.

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To do a better time comparison between high-precision clocks (such as a Cesium-fountain clock and Hydrogen-maser clock), we want to study and eventually lower the GPS carrier-phase time transfer noise. The GPS carrier-phase time transfer noise comes from four sources: GPS satellite, GPS signal path, ground receiving equipment (receiver and antenna), and data-processing algorithm. This paper focuses on the noise introduced by the ground receiving equipment. At NIST, we have installed seven GPS receivers. All receivers have the same reference time, i.e., UTC(NIST). Three of them are connected to the same antenna. The other four are connected to four different antennas. This architecture enables us to study the time-transfer noise from the ground receiving equipment. We study both long-term (> 100 days) noise and short-term (< 1 day) noise. For the long-term noise, the time-transfer result using one receiver can vary from that using another receiver by up to 1.8 ns, during 1.3 years. To achieve sub-nanosecond GPS timing accuracy, a careful monitoring of the time delays or a more frequent calibration is needed. For the short-term noise, we find that the common-clock difference between receivers using the same antenna is less noisy than that using two different antennas, at an averaging time of less than 0.5 hour. This indicates that the antenna and antenna cable contribute to the super-short-term noise of GPS carrier-phase time transfer significantly. In addition, the response to the GPS receiver's reference-time change is tested in this paper. The variation in the response can be up to ± 350 ps. Last, this paper gives the best carrier-phase time transfer result we can currently achieve with the available equipment at NIST. The best frequency stability is 4.0×10 −16 at 3 hours, 1.1×10 −16 at 1 day, 4.0×10 −17 at 10 days, and 1.3×10 −17 at 48 days.

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“…Such investigations have been classical since the 1960s (Blackband, ), but the proliferation of computers with huge computational power fitted with sound cards (Carlà, ; Schulte et al, ) sampling at least at 192 ksamples/s allows for any curious experimenter to implement such a receiver at basically no cost since all demodulation schemes are implemented as software, the ultimate implementation of software‐defined radio (SDR) principle in which the only hardware part is analog to digital conversion of the electromagnetic signal reaching the antenna (Dolea et al, ; Kamp, ). Indeed, the current trend to shift from analog to digital signal processing, especially in the context of time and frequency metrology (Gotoh et al, ; Huang et al, ; Mochizuki et al, ; Sherman & Jördens, ; Uchino & Mochizuki, ), meets the requirements of improved stability, flexibility, and reconfigurability (Mindell, ) provided by SDR, which has become practical lately with the advent of radio frequency high‐resolution analog to digital converters.…”

Section: Introductionmentioning

confidence: 99%

Software‐Defined Radio Decoding of DCF77: Time and Frequency Dissemination with a Sound Card

et al. 2018

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We investigate time and frequency dissemination using software‐defined radio processing of signals acquired from a low‐frequency emitter using a sound card. We use the resulting propagation time measurements for investigating some ionosphere physics and its interaction with cosmic ray flux. Rather than using the amplitude of the transmitted signal as classically considered, we here focus on a precise time of flight measurement by demodulating the spectrum spreading phase modulation added to the DCF77 amplitude modulation.

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Stability improvement of an operational two-way satellite time and frequency transfer system

Cited by 32 publications

References 28 publications

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map

A Study of GPS Carrier-Phase Time Transfer Noise Based on NIST GPS Receivers

Software‐Defined Radio Decoding of DCF77: Time and Frequency Dissemination with a Sound Card

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