This may look like a brightly decorated Easter egg wrapping, but it actually represents how ESA’s Gaia satellite scanned the sky during its first 14 months of science operations, between July 2014 and September 2015.
The oval represents the celestial sphere, with the colours indicating how frequently the different portions of the sky were scanned. Blue represents the regions scanned most frequently in that time period; the lighter colours lesser so.
The satellite scans great circles on the sky, with each lasting about six 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. … (ESA/GAIA)