Gaia Data Release 2
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Table 2

Summary of the astrometric calibration model and number of calibration parameters in the astrometric solution for Gaia DR2.

Basis functions Multiplicity of dependencies Number of

Effect and brief description Klm j f n g b w νeff G parameters
1 AL large scale lm = 00, 10, 20, 01 4 243 2 62 120 528
2 AL medium scale, gate lm = 00, 10 2 10 2 62 8 9 178 560
3 AL large scale, window class lm = 00, 10 2 14 2 62 3 10 416
4 AL large scale, window class, colour lm = 00, 10, 01 3 14 2 62 3 1 15 624
5 AL large scale, window class, magnitude lm = 00, 10 2 14 2 62 3 1 10 416
1 AC large scale lm = 00, 10, 20, 01 4 14 2 62 6 944
2 AC large scale, gate lm = 00 1 14 2 62 8 13 888
3 AC large scale, window class lm = 00, 10 2 14 2 62 3 10 416
4 AC large scale, window class, colour lm = 00, 10, 01 3 14 2 62 3 1 15 624
5 AC large scale, window class, magnitude lm = 00, 10 2 14 2 62 3 1 10 416

Notes. The column Basis functions lists the combinations of indices l and m used to model variations with AC coordinate on a CCD () and with time within a time granule (). Multiplicity of dependencies gives the number of distinct functions or values for each dependency, or a dash if there is no dependency: basis functions (Klm), granule index (j), field index (f), CCD index (n), gate (g), stitch block (b), window class (w), effective wavenumber(νeff), and magnitude (G). The last column is the product of multiplicities, equal to the number of calibration parameters of the effect.

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