Data products

Scanning law

The scanning law describes where Gaia was pointing as a function of time. This is a crucial piece of information, because whether a star has astrometry or photometry or spectroscopy in Gaia depends on how many times that star was observed, and the scanning law describes the correlations between the number of observations of different stars.

Temporal gaps

While Gaia continuously gathers measurements, not all of those measurements are scientifically useful. There may have been excessive glare from the moon, a micro-meteoroid might have knocked Gaia off-axis, or some of the calibration data may have gone missing en route to Earth. Measurements from these times are removed from processing, which causes gaps in the time coverage of the Gaia dataset and alters the selection function.

  • Temporal gaps ( during which none of the photometry obtained by Gaia in any of the G, BP or RP bands contributed to the final data catalogue. This list was identified in CoG, Paper I. Further gaps affecting the photometry, astrometry and spectroscopy are given in the text of that paper.

  • The Gaia Data Processing and Analysis Consortium has now published an official list of gaps ( for the period of DR2, inspired by our frequent questions to the Gaia Helpdesk about particular gaps. These gaps should - in general - be used in preference to the gaps listed above!