Author(s): Enrique Utrilla
The Gaia Catalogue does not only produce a wealth of data, it also represents a complex processing before a Catalogue can be issued. The main data processing is being handled by three DPAC Coordination Units, CU3 for the astrometric data, CU5 for the photometric data and CU6 for the spectroscopic data. Then three Coordination Units analyse the processed data, CU4 for optical or binary stars, solar system objects and extended objects, CU7 for variable stars, and CU8 for classification and astrophysical parameters. Finally, CU9 takes care of the intermediate and final publication of the Gaia data.
Before proceeding to the validation of the data, the information obtained from different Coordination Units (or even different processes inside a single Coordination Unit, such as AGIS and IDU for CU3) have to be integrated and combined into a coherent unit. For Gaia EDR3 this also implies combining the information already processed during cycles 1 and 2 that was the base for the Gaia DR2 catalogue with updates from cycle 3.
These integrated records contain all the available information on the observed sources in a format which is convenient for processing, but not for being stored and queried in a database. Therefore these records must be converted to a more convenient format for validation and presentation before being ingested into the Archive database. At the same time, sources that do not meet some minimum astrometric or photometric quality are filtered out. These filters are defined in Section 7.2.3.
Once the data are in the Archive database providing convenient access to the data, a cross-match with external catalogues is computed, and some dedicated validation processes are run to provide statistics, assess their consistency and flag sources that do not pass the validation criteria. These sources are then filtered out before the catalogue is released to the public.
This chapter describes these successive steps which are being followed for the consolidation of the Catalogue.