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.Comment: Submitted at Living Review of Relativit

Sensitivity analysis of polar orbiter motion to lunar viscoelastic tidal deformation

We investigate the impact of viscoelastic tidal deformation of the Moon on the motion of a polar orbiter. The dissipative effects in the Moon’s interior, i.e., tidal phase lags, are modeled as Fourier series sampled at given frequencies associated with linear combinations of Delaunay arguments, the fundamental parameters describing the lunar motion around the Earth and the Sun. We implement the tidal model to evaluate the temporal lunar gravity field and the induced perturbation on the orbiter. We validate the numerical scheme via a frequency analysis of the perturbed orbital motion. We show that, in the case of the Lunar Reconnaissance Orbiter at a low altitude of less than 200 km, the main lunar tides and hence the potential Love numbers around the monthly and some multiple frequencies are dynamically separable. The omission of those effects in practice introduces a position error at the level of a few decimeters within 10 days

Observations astrométriques des planètes et ajustement des théories analytiques de leur mouvement

In this work, we have begun the first adjustment of the analytical theories of the planets built at the IMC-BDL, VSOP. We had gathered together several types of observations, reduced and homogenized them. There are very different types of data : old and recent transit observations spread on a period of more than 2 centuries (1750-1997), photographic and CCD observations, radar ranging data and positions of planets deduced from tracking observations of space probe by the use of the VLBI techniques. We also used positions of outer planets deduced from satellites absolute positions. We have treated an important number of data limiting our first study to the planets Mercury, Venus, Jupiter and Saturn. From the first fit made on Mercury and Venus observations, we have deduced a new link between the inertiel dynamical reference frame of VSOP and the inertiel cinematic reference frame of the ICRS. Furthermore, we confirm the idea that, in the case of the inner planets, thanks to radar and VLBI data, the optical observations, even recent ones, do not bring useful information in the fit and, worth, degrade it. We obtained 3 new solutions for the motion of Mercury, Venus and the Earth-Moon barycenter, with a good external accuracy. We chose to test the quality of the new solution of motion of the Earth-Moon barycenter by including this solution in the outer planets. We made a second fit based on observations of Jupiter and Saturn, computed in the reference frame deduced from the fit on Mercury and Venus observations. We increased the accuracy of a factor 2 on the positions of Jupiter when we compared positions deduced from the fitted solution and observed positions (made at La Palma in 1983-1993) which are not include in the fit. Finally, we made one of the first wavelet analysis on non-regularly sampled time series.Dans ce travail, nous avons commencé à mettre en place le premier ajustement des théories analytiques du mouvement des planètes du système solaire construites à l’Institut de mécanique céleste. Nous avons rassemblé un grand nombre d’observations, de type très différent, nous les avons réduites et avons rendu homogènes les échantillons d’ajustement ainsi constitués. Ces données regroupent aussi bien des observations angulaires méridiennes du XVIIIe et XIXe siècles, des observations CCD modernes que des estimations de distances géocentriques par tirs radar et des positions angulaires déduites du suivi des sondes spatiales par la technique d’interférométrie à très longue base. Nous avons utilisé aussi dans le cas des planètes géantes des positions indirectes du photocentre de la planète déduites d’observations de satellites galiléens ou de Saturne. De l’ajustement des solutions du mouvement de Mercure et Vénus, nous en avons déduit un nouveau raccordement entre le système de référence dynamique des planètes, et plus précisément de VSOP87, et celui cinématique de l’ICRS. De plus, nous confirmons l’idée que les observations optiques ne sont plus à utiliser dans le cadre d’un ajustement précis du mouvement de ces objets, Mercure et Vénus, et justifions l’utilisation univoque de données radio et radio. Un deuxième ajustement, raccordé au précédent, a été effectué pour les solutions analytiques de Jupiter et Saturne. Nous améliorons la précision de ces théories d’un facteur deux lors de comparaisons entre positions déduites de ces nouvelles et positions observées mais non incluses dans les échantillons d’ajustement. Enfin, nous montrons l’efficacité d’appliquer des méthodes d’analyse pointues, telle que l’analyse en ondelettes dans la détection d’effets observationnels dans les résidus utilisés lors des ajustements et l’impact de ces détection-corrections sur les nouvelles solutions

Impact of the dynamical perturbations of the main belt asteroids on planetary ephemerides : Why is it important to have accurate determination of the main belt asteroids size and shape

International audienc

Two problems in solar system dynamics, possible solutions and future

International audienc

Tests of relativity with solar system ephemerides

International audienceNot Availabl

Two problems in solar system dynamics, possible solutions and future

International audienc

Tests of relativity with solar system ephemerides

International audienceNot Availabl

Impact of the dynamical perturbations of the main belt asteroids on planetary ephemerides : Why is it important to have accurate determination of the main belt asteroids size and shape

International audienc

Testing GR and alternative theories with planetary ephemerides

International audienceWe 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 light rays. 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