4.1.8 Fundamental constants

Author(s): Jos de Bruijne

The Gaia data processing makes use of a large number of constants and parameters. These vary from mathematical constants, through constants of nature, to parameters describing the instrument (for instance the number of CCD rows). To keep track of constants and parameters in a controlled way, all data processing software interfaces to the Gaia Parameter Data Base (Section 1.2.3; Perryman et al. 2008). This data base is updated regularly (under configuration control) and is based on industrial design documents and other sources of information. Access to the data base is limited to the DPAC consortium but external users can review the constants of nature (in the most recent, ‘live’ version of the data base) by using the credentials ‘test’ / ‘gaia’ on the GPDB landing page. Gaia EDR3 and Gaia DR3 use IAU resolutions up to and including 2015, the 2014 version of the CODATA recommended values of the fundamental physical constants (Mohr et al. 2016), leap seconds from IERS Bulletin C, and the INPOP10e solar-system ephemerides (Section 4.2.1; Fienga et al. 2016, 2011).