Enlarge / Gaia is an ambitious mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. This amounts to about 1 per cent of the Galactic stellar population. Combined with astrophysical information for each star, provided by on-board multi-colour photometry, these data will have the precision necessary to quantify the early formation, and subsequent dynamical, chemical and star formation evolution of the Milky Way Galaxy. Additional scientific products include detection and orbital classification of tens of thousands of extra-solar planetary systems, a comprehensive survey of objects ranging from huge numbers of minor bodies in our Solar System, through galaxies in the nearby Universe, to some 500 000 distant quasars. It will also provide a number of stringent new tests of general relativity and cosmology. Gaia will be launched from Europe’s Spaceport in French Guiana at the end of 2013. Credit: ESA–D. Ducros, 2013

By repeatedly observing a billion stars, with its billion-pixel video camera, the Gaia mission will allow astronomers to determine the origin and evolution of our galaxy whilst also testing gravity, mapping our inner solar system, and uncovering tens of thousands of previously unseen objects, including asteroids in our solar system, planets around nearby stars, and supernovae in other galaxies.

Professor Gerry Gilmore, from the University of Cambridge and UK Principal Investigator for Gaia, said, "Gaia will be a revolution in our knowledge of the local Universe. For the first time we will have a fair sample of what is out there, where it is, how it is moving, how unseen (dark) matter is distributed, where and when stars formed and where and when the chemical elements of which we are made were created. Gaia will make a huge step towards understanding how the Milky Way came to be formed, and evolved into what we see today. For the first time, we will be able to see the Milky Way in 3-D. In fact in 6-D – where stars are, and how they are moving."

UK participation in the mission is funded by the UK Space Agency and scientists and engineers from around the UK have played key roles in the design and build of Gaia. The UK Science and Technology Facilities Council (STFC) funded the early development of the project, including the set-up of the data applications centre. STFC's current support involves the UK exploitation of the scientific data to be yielded from the mission.

The Cambridge Gaia Data Processing Centre will be the front line in processing Gaia's images, which will also be key to the discovery of many thousands of transient stars and supernovae: these will be made immediately available to schools and the public for their participation in the research.

Dr Chris Castelli, Acting Director of Technology, Science and Exploration at the UK Space Agency, said, "Gaia is an important space mission for the UK; we've won around €80 million of contracts from the European Space Agency to build the spacecraft and are providing a state of the art data centre that will turn the mission's raw data into the largest stellar catalogue ever made."

Andy Stroomer, Astrium UK's Director of Earth Observation, Navigation, and Science, added, "We are extremely proud of our contribution to the unique Gaia mission – the latest example in a long and successful heritage of supporting ESA science. Stevenage engineers have provided core systems for the Gaia satellite including video processing unit, satellite electrical platform, and mechanical subsystems,".

Gaia will map the stars from an orbit around the Sun, near a location some 1.5 million km beyond Earth's orbit known as the L2 Lagrangian point. The spacecraft will spin slowly, sweeping its two telescopes across the entire sky and focusing their light simultaneously onto a single digital camera, the largest ever flown in space.

Once Gaia starts routine operations, around Easter 2014, astronomers will have the challenge of dealing with a flood of data. Even after being compressed by software, the data produced by the five-year mission will fill over 30 000 CD ROMs. This data will be transmitted 'raw' and will need processing on Earth to turn it into a calibrated set of measurements that can be freely used by the astronomical community. The cutting edge computer technology developed at the Cambridge Data Processing Centre will be key to this process.

The first Gaia science will be discoveries of new sources – supernovae, extreme variable stars and blazars – which will be discovered at the Cambridge processing centre, and immediately made available for study by both professionals and the interested public. Gaia will discover many new sources which are bright enough for amateurs, and schools with access to public robotic telescopes, to become the first to confirm and obtain more information. Schools and amateurs will be able to load their data onto the Gaia web site (http://.ac.uk) where it will be used in scientific analyses, and fully credited.

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