Image above: Annotated map of star positions in the sky in the first Gaia data set released on 14 September 2016. Credit: ESA / Gaia DPAC

ESA’s Gaia mission represents the next European breakthrough in astrophysics, a cornerstone mission launched in December 2013 aimed at producing the most accurate 3D map of the Milky Way to date. The resulting stereoscopic census of our Galaxy will represent a giant leap in astrometric accuracy complemented by the only full sky homogeneous photometric survey with an angular resolution comparable to that of the Hubble Space Telescope, as well as the largest spectroscopic survey ever undertaken.

The primary scientific aim of the mission is to map the structure of our Galaxy and unravel its formation history and subsequent evolution. This ‘Galactic archaeology’ requires a detailed mapping of the structure, dynamics, chemical composition, and age distribution of its stellar populations. Ideally one would like to ‘tag’ individual stars to each of the progenitor building blocks of the Galaxy. The Gaia mission is designed to provide the required fundamental data in the form of distances (through parallaxes), space velocities (through proper motions and radial velocities) and astrophysical characterization (through multi-color photometry) for massive numbers of stars throughout most of the Galaxy.

However, Gaia is not simply a ‘Milky Way mission’ but is truly a multi-faceted astrophysics mission which will enable all three of NOVA’s science networks to obtain exciting scientific results covering many topics: fundamental stellar data across the Hertzsprung-Russell diagram, the characterization of tens of millions of binary stars, unique samples of variable stars of nearly all types (including key cosmological distance calibrators), detection and orbital classification 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. Gaia will also provide a number of stringent tests of general relativity. Last but not least, a massive survey such as Gaia will uncover many surprises that the Universe still holds in store for us.

Gaia will measure positions, parallaxes and proper motions with accuracies ranging from ~10 to ~300 micro-arcsecond per year for over 1 billion stars to 20th magnitude. Multi-color photometry will be obtained for all stars and radial velocities, ranging in accuracy from 1 to 15 km/s, will be collected for stars brighter than 16th magnitude. This NOVA instrumentation project is aimed at enhancing the scientific exploitation of Gaia data in The Netherlands by participating in the photometric data analysis and in the scientific validation of the Gaia data products. The photometric data analysis encompasses all steps from the treatment of the raw photometric data coming directly from the satellite to the delivery of the final mission-averaged photometry for each observed object. Gaia’s photometric instrument consists of two low-resolution fused-silica prisms dispersing all the light entering the telescopes. One disperser — called BP for Blue Photometer — operates in the wavelength range 330–680 nm; the other — called RP for Red Photometer—covers the wavelength range 640–1050 nm.

The data processing for Gaia is undertaken by the Gaia Data Processing and Analysis Consortium (DPAC). The funding is provided by the national funding agencies through a multilateral agreement with ESA. Each partner commits to delivering a specific contribution to the overall data processing system for Gaia. The NOVA deliverable is specified as the ‘definition, design, development, validation, provision and maintenance of a complete software package for the flux extraction, color estimation, initial data treatment, and PSF/LSF calibration for the Blue and Red Photometers (BP/RP) of Gaia’ and ‘the definition, design, development, validation, provision and maintenance of a complete software package for clustering and advanced data selection for multi-Dimensional visualization’.

More information on Gaia can be found on the ESA website.

The NOVA principal investigator for Gaia, also the chair of the DPAC executive is Dr. Anthony Brown (Leiden observatory)

Image below: The spinning Gaia spacecraft is continually scanning two different swaths over the sky, registering the position (and brightness) of each star observed with astonishing accuracy. Credit: ESA