2 April 2015
The Gaia-GBOT (Gaia Ground Based Optical Tracking) is a part of the "Data Processing and Analysis Consortium", the large consortium of over 400 scientists from many European countries, charged with the scientific conduction of the Gaia mission by ESA.
The GBOT group is in charge of the optical part of the tracking of the Gaia satellite. This optical tracking is necessary to allow the Gaia mission to fully reach its goal in terms of astrometric precision level (primarily to correct for the effects of relativistic aberration and for the precise determination of parallaxes of solar system objects), and which cannot be reached using the standard procedures alone, i.e. by a single ranging and communications station. These observations are done daily and will be performed during the 5 years of the mission (with the use of optical CCD frames taken by a small network of 2-3 meters class telescopes located all over the world).
The requirements for the accuracy on the satellite position determination, with respect of the stars in the field of view, is 20 mas (corresponding to 150 meters at the distance to Gaia). Note that the full level of accuracy that is required for GBOT can only be reached, once we are able to use the first data from Gaia itself, available about 1.5-2 years after mission start (which is even then much more accurate than anything available today) as a reference catalog, meaning that all observation obtained till then need to be re-reduced.
The storage and the astrometric reduction of the Gaia-GBOT data are officially the charge of the SyRTE division of "Observatoire de Paris.
The web-page of the Data Storage and Processing Center of Gaia-GBOT