Gaia-DR2 asteroid observations and INPOP planetary ephemerides

TL;DR

This study uses Gaia-DR2 asteroid data with updated planetary ephemerides to refine asteroid orbits, compare with radar data, and address systematic errors, informing future Gaia data releases.

Contribution

It demonstrates the portability of Gaia-DR2 data with updated ephemerides and introduces a formalism for adjusting global parameters, improving asteroid orbit determination.

Findings

Gaia-DR2 data can be effectively combined with radar observations for asteroid orbit refinement.

Corrections are necessary when using Gaia satellite positions with different planetary ephemerides.

Systematic Gaia biases need to be incorporated for optimal combined orbit analysis.

Abstract

We used the INPOP19a planetary ephemerides to perform the orbital adjustment of 14099 asteroids based on Gaia-DR2 observations, and compare for 23 of them the resulting orbits to radar data. As Gaia-DR2 has been processed using the planetary ephemeris INPOP10e, the primary goal of this paper is to confirm the portability of the data when using an updated version of the solar system model. In particular, we point out the fact that the Gaia satellite positions -- provided with respect to the INPOP10e solar system barycenter -- must be corrected when using another planetary ephemeris . We also present a convenient least square formalism that only handles small matrices and allows the adjustment of global parameters, such as masses. In order to check the consistency of the Gaia observations with other types of observations, we perform an orbital adjustment in combining Gaia and radar range observations for 23 objects, together with a careful post-fit analysis including an estimation of the Gaia systematic errors. Finally, we show that to ensure the combined use of Gaia angular DR2 observations and radar ranging, a more developed than firstly proposed dynamical modeling is required together with the addition of the systematic Gaia bias in the fit procedure.These results give promising directions for the next Gaia delivery, Gaia-DR3.