T. Brüsemeister | Searcharxiv

arXiv2026

The First Look of Gaia: Daily data quality and instrument health assessment with automated early warnings

The ESA Gaia mission is a 10+ year astrometric whole-sky scan, demanding consistent data quality over the whole timespan of operations Aims. The Gaia First Look (FL) is a system whose aim is monitoring the data quality to identify problems, which includes early warning capabilities for potential upcoming issues. Methods. In order to achieve its goals, the Gaia FL implemented its own limited astrometric solution, and used the daily calibrations from other segments of the Data Processing and Analysis Consortium (DPAC), as well as the diagnostic data from the satellite itself, in order to obtain a complete picture of the situation of the Gaia satellite on a daily basis. This led to a short-term health and data quality check, but also to a broader overview of the longer-term trends and evolutions within the payload. Potential issues that were encountered were reported to other groups within DPAC for further analysis purposes. When required, ways to mitigate the problems were discussed, and implemented. Results. We show a number of findings by the Gaia FL concerning longer-term evolution, individual but common effects, as well as detrimental impacts, all of which occurred over the operational phase of the Gaia mission

astro-ph.IM↗

arXiv2016

Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes

Gaia Data Release 1 (Gaia DR1) contains astrometric results for more than 1 billion stars brighter than magnitude 20.7 based on observations collected by the Gaia satellite during the first 14 months of its operational phase. We give a brief overview of the astrometric content of the data release and of the model assumptions, data processing, and validation of the results. For stars in common with the Hipparcos and Tycho-2 catalogues, complete astrometric single-star solutions are obtained by incorporating positional information from the earlier catalogues. For other stars only their positions are obtained by neglecting their proper motions and parallaxes. The results are validated by an analysis of the residuals, through special validation runs, and by comparison with external data. Results. For about two million of the brighter stars (down to magnitude ~11.5) we obtain positions, parallaxes, and proper motions to Hipparcos-type precision or better. For these stars, systematic errors depending e.g. on position and colour are at a level of 0.3 milliarcsecond (mas). For the remaining stars we obtain positions at epoch J2015.0 accurate to ~10 mas. Positions and proper motions are given in a reference frame that is aligned with the International Celestial Reference Frame (ICRF) to better than 0.1 mas at epoch J2015.0, and non-rotating with respect to ICRF to within 0.03 mas/yr. The Hipparcos reference frame is found to rotate with respect to the Gaia DR1 frame at a rate of 0.24 mas/yr. Based on less than a quarter of the nominal mission length and on very provisional and incomplete calibrations, the quality and completeness of the astrometric data in Gaia DR1 are far from what is expected for the final mission products. The results nevertheless represent a huge improvement in the available fundamental stellar data and practical definition of the optical reference frame.

astro-ph.GA↗