The figure above shows the track of the Gaia satellite against the night sky. The positions were measured by GBOT, Gaia's Ground Based Optical Tracking network, over the past 13 months.
Gaia is now on its second Lissajous orbit around the L2 point. The image, with the sky in ecliptic coordinates, shows the oscillation of Gaia around L2.
The coordinates and magnitudes of the backdrop stars have been taken from the Hipparcos catalogue and are restricted to naked eye objects, i.e. stars brighter than 6.0 mag. The Gaia track, which is colour coded, is time dependant, with black and violet depicting the first days, starting on 25 December 2013, and red depicting the most recent positions in January 2015. Each point shows one set of GBOT observations, with gaps resulting from full moon periods; other gaps can be attributed to bad weather or similar issues. The large gap near 18h is due to the extremely overcrowded environment near the centre of the Milky Way where an astrometric reduction of the data is almost impossible.
The GBOT campaign utilises a network of small-to-medium telescopes to deliver one set of data per day which allows the determination of Gaia's position to an accuracy of about 20 milli arcseconds. Observations have been made with the 2.0-m Liverpool Telescope on La Palma, ESO's 2.6-m VST on Paranal and the Las Cumbres telescopes. The position extraction is performed at Paris Observatory. GBOT's data on Gaia will be included in the orbit reconstruction performed at Europe's Space Operations Centre (ESOC) in Darmstadt in order to increase the accuracy of this undertaking.