arXiv subjects

Yan Seyffert

Publications and source records attributed to Yan Seyffert.

3 recordsLinked to original sources

arXiv2026

TEMPUS: Relativistic coordinate time scales for any solar-system body from arbitrary ephemerides

Precise time-scale transformations between solar-system bodies are an essential requirement for deep-space science and solar system navigation. The post-Newtonian relativistic expression relating a body-centered coordinate time TCX to the Barycentric Coordinate Time TCB depends on the gravitational environment and velocity of the target body, and must be evaluated consistently with the chosen planetary ephemerides. So far only INPOP has provided such a solution as part of its ephemerides releases, albeit only for Earth with TCG-TCB. We present TEMPUS, a tool that numerically integrates the IAU 2000 time-transformation for any solar-system body using positions and velocities from an arbitrary ephemerides. We provide a validated, ephemerides-agnostic implementation of TCX-TCB and assess its accuracy against published independent solutions. The rate $d\,\mathrm{TCX}/d\,\mathrm{TCB}$ is integrated with an Adams-Moulton order-12 predictor-corrector. The gravitational potential sum tested here includes the Sun, eight planets, Pluto, up to 343 main-belt asteroids, and 30 trans-Neptunian objects. Outputs can be stored in readable format tables of sampled values or as Chebyshev coefficient files. Comparisons are performed against the TU Dresden Klioner time solutions, the TCG-TCB solution provided with INPOP19a and INPOP21a, and the LTE440 lunar solution. For the planetary bodies TEMPUS agrees with Klioner at the $10^{-21} s\,s^{-1}$ level over 200 yr. Against the INPOP19a released TCG-TCB we also agree to the same level. The main-belt asteroids as well as the trans-Neptunian objects shift the planetary time scales at the $10^{-18} s\,s^{-1}$ level, and the choice of planetary and lunar ephemerides contributes differences on the $10^{-18} s\,s^{-1}$ level as well. TEMPUS provides a validated, ephemeris-agnostic post-Newtonian time-transformation for any solar-system body.

astro-ph.EP↗

arXiv2026

NovaMoon: A Strategic Lunar Reference Station for Positioning, Timing, and Largely Enhanced Science in the Earth-Moon System

The renewed interest in lunar exploration and the development of future lunar communication and navigation services highlight the need for a precise, stable, and interoperable geodetic and timing infrastructure on the Moon. NovaMoon, proposed as a scientific and navigation payload for ESA's Argonaut lander, is designed as a lunar-based local differential, geodetic, and timing station supporting both operational needs in the Moon's south polar region and a broad range of scientific investigations. The payload integrates a lunar laser retroreflector, a Very Long Baseline Interferometry transmitter, a receiver for navigation signals compatible with LunaNet standards, high-stability atomic clocks, and direct-to-Earth radio links -- making it the first lunar station to co-locate multiple ranging, tracking, and timing techniques. NovaMoon will enable sub-metre to decimetre positioning, provide local differential corrections for lunar users, and ensure an accurate and stable realisation of position and time. Preliminary simulation studies show that this multi-technique dataset improves the lunar reference frame, orientation and ephemerides, and estimates of interior parameters like tidal response and core properties. NovaMoon will also provide the first long-duration physical realisation of a lunar time reference. Beyond its primary goals, it supports improved cartography, precise surface geolocation, and higher-resolution topography, contributing to safer landings and operations. It also enables new tests of fundamental physics, including constraints on relativity and possible deviations from classical gravity.

astro-ph.EP↗

arXiv2025

Relativistic Time Modeling for Lunar Positioning Navigation and Timing

Future lunar missions will depend on an internationally agreed upon timescale that remains accurate under the Moon's unique gravitational environment and its orbital dynamics. This thesis investigates the proposed Lunar Coordinate Time (TCL), derived analogously to Geocentric Coordinate Time (TCG) and thus aligned with current IAU proposals. We first formalise the TCL transformation and quantify its characteristics from solar system simulations. Next, we compute stationary surface-clock drifts caused by gravitational redshift and the Moon's changing orientation parameters, evaluating how accurate atomic clocks deployed on the surface of the Moon (much like for ESA's proposed NovaMoon mission) would have to be to measure these effects. Finally, we simulate relativistic proper time for ESA's Moonlight navigation satellites, identifying average drift and harmonic variations, to better understand the system that will comprise and enable a Lunar PNT (Positioning, Navigation and Timing) architecture. These kinds of investigations are an essential step toward a sustained internationally cooperative operation at the lunar south pole and beyond.

astro-ph.EP↗