#skyscan

(ESA)  Gaia scanning the sky

A visualisation of how Gaia scanned the sky during its first 14 months of operations, between July 2014 and September 2015. The oval represents a projection of the celestial sphere, with different portions of the sky gradually appearing, according to when and how frequently they were scanned by Gaia. The satellite scans great circles on the sky, with each scan lasting about 6 hours. During the first month, the scanning procedure was such that the ecliptic poles were always included. This meant that Gaia observed the stars in those regions many times, providing an invaluable database for the initial calibration of the observations. Then, starting on 21 August 2014, the satellite started its main survey, employing a scanning ‘law’ designed to achieve the best possible coverage of the whole sky. Credit: ESA/Gaia/DPAC; Acknowledgement: B. Holl (University of Geneva, Switzerland), A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC