9.2.1 Data integration

Author(s): Alex Hutton and Enrique Utrilla

As described in previous sections, the data received from Gaia follows a chain of processes focused in different aspects. Typically each of these specialized processes uses only the part of the data available for each source that is relevant for it, discarding the rest. In other cases, output is generated only for a subset of the sources. For this reason the output of different processes has to be combined with the original data as part of the cyclic processing to generate a complete record with all the information available for each source.

From the point of view of astrometry, the core of this integration process is the combination of the data from IDU, which provides the crossmatch of individual observations into sources, and AGIS, that generates an astrometric solution for the position and proper motions of the sources, as well as data from the initial catalogue.

In particular, for DR2 the astrometry datasets to be integrated are the following:

  1. 1.

    The complete, unfiltered list of sources obtained in the cycle 1, from which the Gaia DR1 catalogue was extracted. This includes data integrated from the AGIS and IDU in the cycle 1 (AGIS-01 and IDU-01).

  2. 2.

    An update on some sources from cycle 1 whose crossmatch was incorrect due their high proper motion (HPM).

  3. 3.

    The lists of new, updated and removed sources as a result of the processing in IDU of the cycle 2 data (IDU-02). This process can result in the merging of two previously separate sources, or the split of the observations previously assigned to a single source into two or more, or the deletion of a source based on previous spurious observations.

  4. 4.

    The astrometry produced by AGIS for these cycle 2 sources (AGIS-02).

Additionally, other data merged into the source records when available was:

  • Solar System object parameters

  • detailed photometry and spectrometry

  • radial velocities

  • variability classification

  • stellar parameters

  • etc.

This integration process is carried out by a dedicate software called MDBIntegrator.