Science of Solar System Objects with the GAIA Mapping Mission and the GDR Catalogues.

Description

Since the beginning of its scientific programme, in mid-2014, the ESA space mission Gaia has regularly scanned the whole scan, providing astrometry, spectrometry, and spectro-photometry, of about a billion of stars and also Solar System Objects (SSOs). Although it is not specifically designed for observation of moving objects, the Gaia satellite provides photometric and astrometric measurements, with unprecedented accuracy, for a very large number of SSOs, mainly asteroids. The unique capabilities of Gaia allow for the collection of an extensive and homogeneous data set of some 350,000 asteroids (that is almost half of the known population), some planetary satellites, and comets, down to the limiting magnitude of G20.7 mag, at the sub-milli-arcsec and milli-mag level accuracy. Thanks to large number of sources, the systematic character of the survey, and the measurements of metrological precision into play, Gaiawill open a new era in asteroid science. Gaia has already started to provide its harvest with the first two Gaia data releases, DR1, published in September 2016. Gaia DR1 did provide positions for about 1 billion stars and proper motion for the Tycho-Gaia TGAS of 2 millionstars. The second data release, DR2 to be published in April 2018, will be the major step in the Gaia mission, providing all astrometric parameters (including parallax and proper motion) for a billion stars, in an absolute reference frame - to become the optical ICRF. Gaia DR2 will also provide for the first time epoch astrometry and photometry for about 14000 asteroids from its direct observations, down to magnitude G20.7. The Gaia performance remains excellent overthe entire available brightness range. We will present the Gaia data reduction pipeline for the SSOs, within the framework of the Data Processing and Analysis Consortium (DPAC), and the validation process of the DR2 data. We illustrate the peculiar properties of each single observation, as these properties will affect the subsequent exploitation of the mission data. Overall, we expect to derive masses, sizes, average densities, spin properties, reflectance spectra, albedos, as well as new taxonomic classifications for a very large numbers of asteroids. We will discuss the improvement brought by Gaia over 5 years of nominal mission, starting with DR1, and focusingespecially on the dynamics of asteroids and other Solar System Objects. This includes use of the catalogue for calibrating future and past photometric and astrometric observations, new perspectives for orbit determination and stellar occultations, detection of small acceleration or perturbations for the asteroids. Also we illustrate the ground-based activity coordinated by the Gaia-FUN-SSO network for follow-up observations of newly discovered Near Earth Object. Wewill further focus on the areas that will benefit from complementary observational campaigns to improve the scientific return of the mission, and on the involvement of the planetary science community as a whole in the exploitation of the Gaia survey.

Abstract

International audience

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