Passive TWSTFT: a cost-effective alternative for robust UTC(k) dissemination
Year: 2026
Type: article
Abstract: Two-way satellite time and frequency transfer (TWSTFT) is among the most accurate techniques for comparing clocks over (inter)continental baselines, exchanging bidirectional signals through a geostationary satellite—but the cost and complexity of an active (Tx & Rx) terminal restrict it to a handful of Coordinated Universal Time (UTC)(k) laboratories. We show that a passive, receive-only user can reach those same laboratories by reducing a one-way pseudorange for the satellite-motion, atmospheric, and equipment delays. Using active-network observations over 130 d, the satellite ephemeris is reconstructed by orbit determination (OD). A portable terminal—a commercial TV dish and a software-defined-radio receiver—was calibrated in common-clock mode at INRiM and deployed to the Côte d”Azur Observatory (OCA). Over a 40 d campaign, time transfer to three UTC(k) laboratories agreed with independent GNSS and active-TWSTFT links at the nanosecond level; despite larger short-term noise from solar-radiation-pressure and wet-tropospheric mismodelling, the overlapping Allan deviation reaches ≈ 10 − 14 at one day, matching GNSS performance. The accuracy is bounded by an ≈ 7 ns ( 1 σ ) budget, and an INRiM–OCA–INRiM closure sequence confirmed robustness to relocation and traceability to UTC(k). Passive TWSTFT thus offers a scalable, interference-resilient, and low-cost route to UTC(k) dissemination, with future work targeting automated OD for quasi-real-time operation.
Source: Metrologia
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,325
OpenAlex ID: W7171980235