arXiv subjects

Agnès Fienga

Publications and source records attributed to Agnès Fienga.

13 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

The International Lunar Reference System

As the exploration of the Moon accelerates in the coming years, there is already an urgent need to standardise the Position, Navigation and Timing of spacecraft, and consequently for the definition of the lunar reference system and frame. This document gathers the most recent recommendations of the the International Association of Geodesy (IAG) / International Astronomical Union (IAU) Joint Working Group (WG) 1.1.3 "Lunar Reference frames" on the topic. Despite the challenges for producing a Lunar Reference System and Frame due to the limited number of control points and a single data type, the WG proposes applying an approach developed for Global Navigation Satellite Systems (GNSS). This supports an accurate and reliable reference system, consistent with International Earth Rotation and Reference Systems Service (IERS) standards and, based on redundant sources, ensures resilience for the lunar Position, Navigation and Timing (PNT) framework. The first realization of the International Lunar Reference Frame 2026 (ILuRF2026), ILuRF2026, is delivered on the temporay website https://ilurs-6e772d.gitlab.io/ and on the future http://ilurf.gssc.esa.int together with associated software.

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

Definition and Realization of the International Lunar Reference Frame

All future lunar missions require a definition of the lunar reference system and a realization in the form of the lunar reference frame to ensure consistent products for positioning, navigation, cartography, and timing. This paper defines the origin, orientation, and scale of the Lunar Reference System (LRS), as well as provides numerical solutions for the first realization of the International Lunar Reference Frame (ILRF). ILRF is defined as the Principal Axis (PA) system, attached to the surface and co-rotating with the Moon, with its origin in the lunar center of mass (lunocenter). The ILRF realization is based on variance component estimation of the three lunar ephemeris solutions: INPOP21a, DE430, and EPM2021 for the series of the position of the lunar center of mass and rotation Euler angles -- precession, nutation, and proper rotation. The solution is valid starting with the period covered by Lunar Laser Ranging (LLR) data in 1970 and ending with extrapolated ILRF realizations in 2052 for future lunar missions. Results. The combined ILRF is characterized by the mean error of 17.6 cm for 2010-2030, where 15.3 cm comes from the origin and 8.6 cm from the orientation realization. The error in the realization of the origin is mainly caused by a poor geometry of the retroreflector network, resulting in a high correlation between the scale and the X component of the lunocenter in PA. The LLR post-fit residuals in ILRF are at the level of 2-3 cm in terms of the standard deviations of one-way ranges for best-performing LLR stations. The mean errors of the transformation between ILRF and other reference frame realizations in PA are at the level of 3 cm, whereas the mean transformation error to the DE421 Mean Earth frame equals 5 cm.

astro-ph.EP↗

arXiv2025

Boosting decision trees for Main Belt Asteroid selection in planetary ephemerides: an alternative model

One of the main bottleneck in assessing the accuracy of Mars orbit is the unknown value of the asteroids in the Main Asteroid Belt. Nowadays a modeling with 343 asteroids as point masses is used, with the relative masses fitted to observational data. In the current work we propose an innovative methodology to reduce the number of asteroids implemented as point masses, thus reducing the number of parameters to be fitted, without a significant degradation of the postfit residuals.

astro-ph.EP↗

arXiv2023

Bayesian test of Brans-Dicke theories with planetary ephemerides: Investigating the strong equivalence principle

Context: We are testing the Brans-Dicke class of scalar tensor theories with planetary ephemerides. Aims: In this work, we apply our recently proposed Bayesian methodology to the Brans-Dicke case, with an emphasis on the issue of the strong equivalence principle (SEP). Methods: We use an MCMC approach coupled to full consistent planetary ephemeris construction (from point-mass body integration to observational fit) and compare the posterior distributions obtained with and without the introduction of potential violations of the SEP. Results: We observe a shift in the confidence levels of the posteriors obtained. We interpret this shift as marginal evidence suggesting that the effect of violation of the SEP can no longer be assumed to be negligible in planetary ephemerides with the current data. We also notably report that the constraint on the Brans-Dicke parameter with planetary ephemerides is getting closer to the figure reported from the Cassini spacecraft alone, but also to the constraints from pulsars. We anticipate that data from future spacecraft missions, such as BepiColombo, will significantly enhance the constraints based on planetary ephemerides.

astro-ph.EP↗

arXiv2023

Testing Theories of Gravity with Planetary Ephemerides

We describe here how planetary ephemerides are built in the framework of General Relativity and how they can be used to test alternative theories. We focus on the definition of the reference frame (space and time) in which the planetary ephemeris is described, the equations of motion that govern the orbits of solar system bodies and {electromagnetic waves}. After a review on the existing planetary and lunar ephemerides, we summarize the results obtained considering full modifications of the ephemeris framework with direct comparisons with the observations of planetary systems, with a specific attention for the PPN formalism. We then discuss other formalisms such as Einstein-dilaton theories, the massless graviton and MOND. The paper finally concludes on some comments and recommendations regarding misinterpreted measurements of the advance of perihelia.

gr-qc↗

arXiv2023

Bayesian test of the mass of the graviton with planetary ephemerides

In this work, we investigated Bayesian methodologies for constraining in the Solar System a Yukawa suppression of the Newtonian potential -- which we interpret as the effect of a non-null graviton mass -- by considering its impact on planetary orbits. Complementary to the previous results obtained with INPOP planetary ephemerides, we consider here a Markov Chain Monte Carlo approach associated with a Gaussian Process Regression for improving the resolution of the constraints driven by planetary ephemerides on the graviton mass in the Solar System. At the end of the procedure, a posterior for the mass of the graviton is presented, providing an upper bound at $1.01 \times 10^{-24} \; eV c^{-2}$ (resp. $λ_g \geq 122.48 \times 10^{13} \; km$) with a $99.7\%$ confidence level. The threshold value represents an improvement of 1 order of magnitude relative to the previous estimations. This updated determination of the upper bound is mainly due to the Bayesian methodology, although the use of new planetary ephemerides (INPOP21a used here versus INPOP19a used previously) already induces a gain of a factor 3 with respect to the previous limit. The INPOP21a ephemerides is characterized by the addition of new Juno and Mars orbiter data, but also by a better Solar System modeling, with notably a more realistic model of the Kuiper belt. Finally, by testing the sensitivity of our results to the choice of the $\textit{a priori}$ distribution of the graviton mass, it turns out that the selection of a prior more favorable to zero-mass graviton (that is, here, General Relativity) seems to be more supported by the observations than non-zero mass graviton, leading to a possible conclusion that planetary ephemerides are more likely to favor General Relativity.

astro-ph.EP↗

arXiv2023

Testing the mass of the graviton with Bayesian planetary numerical ephemerides B-INPOP

We use MCMC to sample the posterior distribution of the mass of the graviton -- assumed here to be manifest through a Yukawa suppression of the Newtonian potential -- by using INPOP planetary ephemerides. The main technical difficulty is the lack of analytical formulation for the forward problem and the cost in term of computation time for its numerical estimation. To overcome these problems we approximate an interpolated likelihood for the MCMC with the Gaussian Process Regression. We also propose a possible way to assess the uncertainty of approximation of the likelihood by mean of some realization of the Gaussian Process. At the end of the procedure, a 99.7% confidence level threshold value is found at $1.01 \times 10^{-24} \; eV c^{-2}$ (resp. $λ_g \geq 122.48 \times 10^{13} \; km$), representing an improvement of 1 order of magnitude relative to the previous estimation of Bernus et al. 2020. Beyond this limit, no clear information is provided by the current state of the planetary ephemerides.

gr-qc↗

arXiv2023

Interplanetary Laser Tri-lateration Network: simulation with INPOP planetary ephemerides

This study is done in the context of the project titled Interplanetary Laser Tri-lateration Network (ILTN) proposed by \cite{2018P&SS..153..127S} and investigated more in details by \cite{2022P&SS..21405415B} and \cite{2022P&SS..21505423B}. The original idea was to propose interplanetary measurements (in this case between Venus, Mars and the earth) as a way to measure the solar system expansion. But some recent interests on the measurement of asteroid masses and more generally the study of the mass distribution in the outer solar system appear with the ILTN. In this work, we are investigating how different possible configurations of interplanetary measurements of distances can be introduced in planetary ephemeris construction and how they improve our knowledge of planet orbits and other related parameters.

astro-ph.EP↗

arXiv2023

Constraints on the lunar core viscosity from tidal deformation

We use the tidal deformations of the Moon induced by the Earth and the Sun as a tool for studying the inner structure of our satellite. Based on measurements of the degree-two tidal Love numbers k2 and h2 and dissipation coefficients from the GRAIL mission, Lunar Laser Ranging and Laser Altimetry on board of the LRO spacecraft, we perform Monte Carlo samplings for 120,000 possible combinations of thicknesses and viscosities for two classes of the lunar models. The first one includes a uniform core, a low viscosity zone (LVZ) at the core-mantle boundary, a mantle and a crust. The second one has an additional inner core. All models are consistent with the lunar total mass as well as its moment of inertia. By comparing predicted and observed parameters for the tidal deformations we find that the existence of an inner core cannot be ruled out. Furthermore, by deducing temperature profiles for the LVZ and an Earth-like mantle, we obtain stringent constraints on the radius (500 +- 1) km, viscosity,21 (4.5 +- 0.8) x 10^16 Pa.s and the density (3400 +- 10) kg/m^3 of the LVZ. We also infer the first estimation for the outer core viscosity, (2.07 +- 1.03) x 10^17 Pa.s, for two different possible structures: a Moon with a 70 km thick outer core and a large inner core (290 km radius with a density of 6000 kg/m3), and a Moon with a thicker outer core (169 km thick) but a denser and smaller inner core (219 km radius for 8000 kg/m^3).

astro-ph.EP↗

arXiv2020

Extending Science from Lunar Laser Ranging

The Lunar Laser Ranging (LLR) experiment has accumulated 50 years of range data of improving accuracy from ground stations to the laser retroreflector arrays (LRAs) on the lunar surface. The upcoming decade offers several opportunities to break new ground in data precision through the deployment of the next generation of single corner-cube lunar retroreflectors and active laser transponders. This is likely to expand the LLR station network. Lunar dynamical models and analysis tools have the potential to improve and fully exploit the long temporal baseline and precision allowed by millimetric LLR data. Some of the model limitations are outlined for future efforts. Differential observation techniques will help mitigate some of the primary limiting factors and reach unprecedented accuracy. Such observations and techniques may enable the detection of several subtle signatures required to understand the dynamics of the Earth-Moon system and the deep lunar interior. LLR model improvements would impact multi-disciplinary fields that include lunar and planetary science, Earth science, fundamental physics, celestial mechanics and ephemerides.

astro-ph.IM↗

arXiv2017

Universality of free fall versus ephemeris

When a light scalar field with gravitational strength interacts with matter, the weak equivalence principle is in general violated, leading for instance to a violation of the universality of free fall. This has been known and tested for a while. However, recent developments [Minazzoli & Hees, PRD 2016] showed that a novel manifestation of the universality of free fall can appear in some models. Here we discuss this new scenario and expose how we intend to constrain it with INPOP ephemeris.

gr-qc↗