2. The GAIA Mission Design

The GAIA mission has been designed to solve one of the most difficult, yet deeply fundamental challenges in modern astronomy: to understand the structure, formation and evolution of our Galaxy. The basic requirement in order to achieve this goal is that of obtaining extraordinarily accurate three-dimensional positions and velocities as well as colors in several bands for a significant sample of the Galaxy's stars. The current mission design ([Gilmore et al. 1998], [Straizys 1999] and [ESA 2000]), which was essentially established during the Concept and Technology Study carried out for ESA by Matra Marconi Space, not only fully meets this requirement but also promises to yield a wide range of ``by-products'' of fundamental scientific relevance in their own right. Even if it will be subject to further optimization in the near future, in its present form already the mission design comprises a detailed description of all relevant aspects, including spacecraft, payload and satellite operations.