The European Gaia astrometry mission is due for launch in 2011. Gaia will
rely on the proven principles of ESA's Hipparcos mission to create an all-sky
survey of about one billion stars throughout our Galaxy and beyond, by
observing all objects down to 20th magnitude. Through its massive measurement
of stellar distances, motions and multi-colour photometry it will provide
fundamental data necessary for unravelling the structure, formation and
evolution of the Galaxy. This paper presents the design and performance of the
broad- and medium-band set of photometric filters adopted as the baseline for
Gaia. The nineteen selected passbands (extending from the ultraviolet to the
far-red), the criteria, and the methodology on which this choice has been based
are discussed in detail. We analyse the photometric capabilities for
characterizing the luminosity, temperature, gravity and chemical composition of
stars. We also discuss the automatic determination of these physical parameters
for the large number of observations involved, for objects located throughout
the entire Hertzsprung-Russell diagram. Finally, the capability of the
photometric system to deal with the main Gaia science case is outlined.Comment: MNRAS, accepted 1-Dec-2005; 26 pages, 15 figure
Abstract. CCD observations of the southern clusters NGC 4755 and 47 Tucanae were obtained in the Vilnius photometric system. A brief outline of the data pathway from observations to final analysis via IRAF and ASCAR software is given.
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