Gaia Data Release 1

Pre-processing and source list creation

¹ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí Franquès 1, 08028 Barcelona, Spain
² Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 14, 69120 Heidelberg, Germany
³ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí Franquès 1, 08028 Barcelona, Spain
⁴ Institute for Astronomy, School of Physics and Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
⁵ Aurora Technology for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
⁶ Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Torino, Via Osservatorio 20, Pino Torinese, 10025 Torino, Italy
⁷ Sterrewacht Leiden, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands
⁸ ESA, European Space Astronomy Centre, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
⁹ Gaia Project Office for DPAC/ESA, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
¹⁰ Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden
¹¹ Technische Universität Dresden, Mommsenstrasse 13, 01062 Dresden, Germany
¹² GEA-Observatorio National/MCT, Rua Gal. Jose Cristino 77, CEP 20921-400 Rio de Janeiro, Brazil
¹³ Altec, Corso Marche 79, 10146 Torino, Italy
¹⁴ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA, UK
¹⁵ Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
¹⁶ GMV for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
¹⁷ EURIX S.r.l., via Carcano 26, 10153 Torino, Italy
¹⁸ SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, LNE, 61 avenue de l’Observatoire, 75014 Paris, France
¹⁹ Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal
²⁰ Institute of Astrophysics and Space Sciences, Faculdade de Ciencias, Campo Grande, 1749-016 Lisboa, Portugal
²¹ INAF, Osservatorio Astrofisico di Catania, 78 Catania, Italy
²² IMCCE, Institut de Mécanique Céleste et de Calcul des Ephémérides, 77 Avenue Denfert-Rochereau, 75014 Paris, France
²³ HE Space Operations BV for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
²⁴ Univ. Bordeaux, LAB, UMR 5804, 33270 Floirac, France, and CNRS, LAB, UMR 5804, 33270 Floirac, France
²⁵ Dipartimento di Informatica, Université di Torino, C.so Svizzera 185, 10149 Torino, Italy
²⁶ Telespazio Vega UK Ltd for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
²⁷ University of Padova, via Marzolo 8, 35131 Padova, Italy
²⁸ RHEA for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
²⁹ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Rd, 200030 Shanghai, PR China
³⁰ The Server Labs S.L. for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
³¹ Vitrociset Belgium for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
³² Astrophysics Research Institute, ic2 – Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
³³ Serco Gestion de Negocios S.L. for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
³⁴ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
³⁵ Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
³⁶ Observatoire de Genève, chemin des Maillettes 51, 1290 Sauverny, Switzerland
³⁷ HE Space Operations BV for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
³⁸ ISDEFE for ESA/ESAC, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Spain
³⁹ Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁴⁰ Barcelona Supercomputing Center, Nexus II Building, Jordi Girona 29, 08034 Barcelona, Spain
⁴¹ Consorci de Serveis Científics i Academics de Catalunya (CSUC), Gran Capita 2, 08034 Barcelona, Spain

^⋆ Corresponding author: C. Fabricius, e-mail: claus.fabricius@am.ub.es

Received: 5 April 2016
Accepted: 23 May 2016

Abstract

Context. The first data release from the Gaia mission contains accurate positions and magnitudes for more than a billion sources, and proper motions and parallaxes for the majority of the 2.5 million Hipparcos and Tycho-2 stars.

Aims. We describe three essential elements of the initial data treatment leading to this catalogue: the image analysis, the construction of a source list, and the near real-time monitoring of the payload health. We also discuss some weak points that set limitations for the attainable precision at the present stage of the mission.

Methods. Image parameters for point sources are derived from one-dimensional scans, using a maximum likelihood method, under the assumption of a line spread function constant in time, and a complete modelling of bias and background. These conditions are, however, not completely fulfilled. The Gaia source list is built starting from a large ground-based catalogue, but even so a significant number of new entries have been added, and a large number have been removed. The autonomous onboard star image detection will pick up many spurious images, especially around bright sources, and such unwanted detections must be identified. Another key step of the source list creation consists in arranging the more than 10¹⁰ individual detections in spatially isolated groups that can be analysed individually.

Results. Complete software systems have been built for the Gaia initial data treatment, that manage approximately 50 million focal plane transits daily, giving transit times and fluxes for 500 million individual CCD images to the astrometric and photometric processing chains. The software also carries out a successful and detailed daily monitoring of Gaia health.