Why Go to Space to Measure Parallaxes?
Stellar parallax is very difficult to measure because it is a very small quantity and it decreases the further a star is from the Earth. Very precise measurements are needed to determine a stellar parallax and this is why we need to get out of the Earth's atmosphere, to get away from the distortions that it creates.
How Accurate Will These Measurements Be?
Gaia will have an accuracy of about 20 microarcseconds (approximately 6 billionths of a degree) at V=15 mag. This accuracy corresponds to the angle subtended by a five-story building at the distance of Mars, when Mars is the furthest away from us.
How Many People Work in the Gaia Project?
Gaia is in the detailed design phase during which time the elements of the craft and instruments are designed in detail, and plans for Gaia's operations are refined. Currently about 500 people are working on Gaia, including ESA staff and members of the space industry, scientific community and academic world.
How Long Does It Take to Build a Satellite Like Gaia?
A mission like Gaia may be studied and discussed for several years before ESA's advisors approve it. Detailed designing and advanced technology studies then take 3 to 4 years, and a further 3 to 4 years are needed to build and test the satellite, and prepare it for launch.
Who Builds the Satellite?
Many individuals, scientific institutes, and industrial companies contribute to a mission like Gaia. As many as 400 scientists, 2000 engineers and managers, and 20 to 30 companies might be involved.
Who Will Have Access to the Data Gathered by Gaia?
The data acquired by Gaia will be converted into useful information (positions, distances, velocities, astrophysical parameters...) by experts in Europe. Results will be available to everyone once the data have been reduced to a useful form. Scientists from any institute, amateur astronomers, or students will have free access to Gaia's data. The general public will also be informed of any interesting discoveries through the internet and other media.