Reduced Gaia commanded scanning law

These data files contain "reduced" versions of the Gaia commanded scan law. The commanded scanning law released by Gaia (https://www.cosmos.esa.int/web/gaia/full-mission-scanning-law) contains the time, sky positions of each field of view, and parallax factors for each field of view sampled with a 10 second cadence. The "reduced" scanning law turns these samples into unique "scans" binned by sky position using a HEALPix pixelization of the sky. Unlike the GOST (https://gaia.esac.esa.int/gost/index.jsp), this does not have a focal plane model, so we don't resolve the CCD-level observations and we won't be extremely precise (we only track which pixels the center of the FOV hits). Each transit is considered as a single scan event. The "reduced" scanning law carries all of the caveats of the commanded scan law: there are known deviations between the commanded and actual scanning law related to the attitude of the spacecraft and time gaps in observing, and these deviations are not included here.

The resulting reduced scanning law data files contain scans with HEALPix level 6. For each sky position / HEALPix pixel, we store one row per transit:

- bjd_time - float32 (TCB BJD relative to Gaia reference time)

- scan_angle_deg - float32 (position angle, degrees)

- parallax_factor_al - float32 (dimensionless)

 

These data files are used by the epochalypse Python package.