Gaia Data Flow System

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Gaia is a European Space Agency Cornerstone mission, to be launched Q4/2011 for a five to six year lifetime. Its scientific goal is to make the largest, most precise map of our Galaxy by conducting a census of the positions and velocities of one thousand million objects in and around our Galaxy. As such it will form the basis for studies of the structure and formation history of our Galaxy, one of the four core themes of UK astronomical research: Star Formation and Development of Galaxies. As a comprehensive survey mission, Gaia is expected to become one of science's greatest discovery machines. It will monitor each of its target objects (primarily stars, asteroids, galaxies and QSOs) on average 85 times over a five-year period, precisely charting their distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and failed stars called brown dwarfs. Within our own Solar System for example, Gaia is expected to identify tens of thousands of hitherto unknown asteroids. Expected discoveries also include the detection and characterisation of tens of thousands of extra-solar planetary systems. The survey will cover about 10 million galaxies and 500 000 distant quasars. It will further provide stringent new tests of general relativity. The Gaia data processing is the key in turning data from the satellite into information which astronomers can then analyse to make new discoveries. It is the link between measurements made by the instruments and the various catalogues with scientific results that will be the science legacy of the mission. The processing task is immense. Gaia is a mission of extremes, which reflects in the range of data reduction techniques required: from extreme-accuracy global astrometry to large scale photometry and spectroscopy, all based on data gathered in a constantly spinning satellite. The volume of data is large, covering nearly 2x10^12 individual observations, but more importantly, nearly the entire volume of data needs to be considered in some of the data processing. The analysis system is being decomposed into a number of key areas, which in sum form the final data processing system for Gaia. Our proposal's aims for the UK's commitment to Gaia is the development of the processing systems required to carry out all reductions of the photometric and most of the spectroscopic observations. Additionally, this work will generate the software systems required to support the Gaia Science Alerts system, which will represent the main early science data products from Gaia. The project will deliver software components designed to perform a wide range of complex processing tasks, * the software required for the the photometric data processing for all 200 CCDs recording image transit data * the data handling system to process the photometric data * the software required for the spectroscopic data processing and calibrations * the software for the Gaia in-flight CCD calibrations * the software for the science alerts sub system The Gaia Data Flow System project consists of key teams from the UK who have been involved in the delivery of large scale computing and analysis systems (such as that for Hipparcos, XMM, Planck, VISTA). Leveraging the knowledge there gained, coupled with use of advances in distributed and virtual observatory interoperability systems will ensure that the UK makes a full and cost effective commitment to the Gaia project, delivering a reduction and analysis system to provide the highest quality science products for eventual exploitation by the UK and European astronomical communities.