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.