ZAH scientists propose ground-tracking of Gaia satellite and use WMAP for initial tests

The Gaia satellite is a cornerstone mission of the European Space Agency (ESA), to be launched in 2011. It will determine accurate positions, distances and velocities of one billion Milky Way stars during its expected five years of operation. ZAH scientists are heavily involved in the preparation of this mission. Given the special requirements of Gaia concerning the three-dimensional location and velocity of the satellite, normal space craft tracking procedures will not be sufficiently precise. In order to ensure that these demands can be reached, ZAH staff astronomer Uli Bastian (ARI) had proposed an additional world-wide astrometric tracking campaign using ground based telescopes. Fellow ZAH scientist Martin Altmann is responsible for the organization and supervision of this international campaign during the mission.

In order to develop and test procedures and methods of such satellite observations before the start of the Gaia mission, the scientists suggested to use the WMAP satellite which is operating at a similar orbit (the L2 Lagrange point of the Sun-Earth system). While being smaller and thus fainter than Gaia, WMAP has proved to be an ideal testbed.

The first optical images of the WMAP satellite were taken for this purpose an April 5th, 2008, by Sebastien Bouquillon (SYRTE/Obs. de Paris), Ricky Smart (INAF/OATo, Torino) and Alexandre Andrei (Observatorio Nacional, Rio de Janeiro) using the Wide-field Image detector (WFI) at the 2.2m ESO telescope in Chile. The three images taken within a few minutes very clearly show the motion of the WMAP satellite with respect to the background stars: they are superposed ("co-added") such that the "moving" WMAP satellite can be identified as the three colored points (red-green-blue) in the top right quarter of the picture. More details can be found on ESA's science news and on the Gaia: Picture of the week.

Contact: D. Möricke