ASTROMETRY GAIA SOFTWARE
Transforming the raw information into useful and reliable stellar positions to a level of accuracy never possible before is an extremely complex procedure, entrusted to a pan-European collaboration of about 450 scientists and software engineers: the Gaia Data Processing and Analysis Consortium, or DPAC. Although the current data are preliminary, we wanted to make them available for the astronomical community to use as soon as possible," adds Dr Prusti. " The satellite is working well and we have demonstrated that it is possible to handle the analysis of a billion stars. Barros (CENTRA – University of Lisbon), on behalf of DPAC. Holl (University of Geneva, Switzerland), A. Click here for details and large versions of the video. The stripes and other artefacts in the image reflect how Gaia scans the sky, and will gradually fade as more scans are made during the five-year mission. " The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations," says Timo Prusti, Gaia project scientist at ESA. This first release is based on data collected during its first 14 months of scanning the sky, up to September 2015. Launched 1000 days ago, Gaia started its scientific work in July 2014. " Today's release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy." " Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before," says Alvaro Giménez, ESA's Director of Science. On its way to assembling the most detailed 3D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1142 million stars.Īs a taster of the richer catalogue to come in the near future, today's release also features the distances and the motions across the sky for more than two million stars. Experiences gained with this first ever space astrometry mission are considered in relation to a follow up mission for Hipparcos.Gaia's first sky map.
The data quality verifications are reviewed and guidelines to the proper use of the Hipparcos data are provided, followed by some of the first scientific results of the mission. Astrometric and photometric data for a selection of 48 minor planets, the Jovian moon Europa and the Saturnian moons Titan and Iapetus were also obtained. The Hipparcos mission was complemented by the Tycho experiment, providing a complete all-sky survey of astrometric and photometric parameters for one million stars down to magnitude 11, though with lower accuracies than obtained for the main mission. This has led to the discovery of thousands of variable stars.
The mission results comprise not only outstanding astrometric data on both single and double stars, but also an unique all-sky photometric survey which has been used for variability investigations. Data files presented in the catalogues are described in the context of the data reductions, and explained in content and usage. This is followed by a description of the input data streams and a summary of the data reductions. It presents a brief review of the satellite, the aims of the mission with their relation to ground-based astrometry, and the mission history. The emphasis is on those aspects that have or may have influenced the data as presented in the catalogues.
A review is presented of the European Space Agency's astrometric satellite project Hipparcos, for which the final data catalogues were published in June 1997.
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