• ESA uses cookies to track visits to our website only, no personal information is collected.
    By continuing to use the site you are agreeing to our use of cookies. OK
    Find out more about our cookie policy.
    • → European Space Agency

    • About Science & Technology

    • For Public

    • For Educators

    • ESA

    • Science & Technology

    • Gaia

    • Missions
    • Show All Missions
    • Mission Home
    • Summary
    • Fact Sheet
    • Objectives
    • Mission Team
    • Industrial Team
    • A History of Astrometry
    • The oldest sky maps
    • Seeing and measuring farther
    • Astrometry in space
    • From Hipparchus to Hipparcos: A sonification of stellar catalogues
    • Mission Science
    • Galactic Structure
    • Stars
    • Solar System
    • Asteroids
    • Exoplanets
    • Science highlights from Data Release 1
    • Scrutinising the Milky Way
    • From the Sun's neighbourhood to the distant Universe
    • Spacecraft
    • Overview
    • Payload Module
    • Service Module
    • Operations & Archive
    • Where is Gaia?
    • The role of DPAC
    • Towards the final Gaia catalogue
    • Data Release 1
    • Data Release 2
    • Launch Vehicle
    • Orbit/Navigation
    • Outreach Resources
    • Resources
    • News Archive
    • Announcement Archive
    • Multimedia Gallery
    • Publication Archive
    • Journal Archive
    • Calendar of Events
    • Services
    • Contact Us
    • Subscribe
    • RSS feed
    • Terms and Conditions

    Billion pixel Gaia camera starts to take shape

    06 July 2011

    Another milestone in the development of Gaia, ESA's ultra-sensitive space astrometry mission, was passed on 1 June when the 106 electronic detectors of its billion pixel camera were assembled like a large mosaic for the first time.

    Technicians carefully bolting and aligning each of the CCDs onto the support structure. Credit: Astrium

    During its ambitious mission to map one thousand million stars, the spinning Gaia spacecraft will monitor each of these pinpoints of light up to 70 times over a five year period. In order to detect distant stars about one million times fainter than the eye can see, Gaia will carry 106 charge coupled devices (CCDs), each of which is, effectively, a miniature camera.

    These rectangular detectors, each measuring 6 × 4.7 cm, with a thickness of only a few tens of microns, are precisely fitted together on the CCD support structure (CSS). The gap between each CCD package is about 1 millimetre.

    Made of silicon carbide, a material that provides remarkable thermal and mechanical stability, the CSS weighs about 20 kg. The overall CCD mosaic, a key part of the complete focal plane assembly, measures 1 × 0.5 metres.

    The complete Gaia CCD mosaic.
    Credit: Astrium

    The contract to provide the Gaia CCDs was awarded to e2v Technologies of Chelmsford, UK, in summer 2005, and their production kept the company busy for more than 5 years. Each CCD converts incoming light into electrical charge and stores it as a tiny data package, or pixel, until it can be read by the onboard computer. The Gaia CCDs feature 4500 pixels in the along scan direction and 1966 pixels for across scan. With an overall total of about a thousand million pixels, Gaia's focal plane is the largest digital camera ever built for a space mission.

    Over the past few weeks, technicians from the mission's prime contractor, Astrium France, have been carefully bolting and aligning each of the CCDs onto the support structure at the company's facility in Toulouse. Working in double shifts inside a Class 100 clean room, the rectangular focal plane mosaic has grown at a rate of about four CCDs per day.

    Video is not supported
    The Gaia telescope elements and focal plane. Credit: ESA
    (For larger versions of this video click here)

    The completed focal plane is arranged in seven rows of CCDs. The main array, which comprises 102 detectors grouped into four fields, is dedicated to star detection. A further four CCDs are used for monitoring the stability of the 'basic angle' of 106.5 degrees between the two telescopes and the quality of the optical performances.

    "The mounting and precise alignment of the 106 CCDs is a key step in the assembly of the flight model focal plane assembly," said Philippe Garé, ESA's Gaia Payload Manager.

    As the two telescopes of the spinning Gaia spacecraft sweep across the sky, the images of stars in each field of view will move across the focal plane array. They will be detected first by the star mapper CCDs. Each of the two strips of seven CCDs detects star images only from its assigned telescope.

    The confirmed star images will then move across a block of 62 astrometric field CCDs, where they are assigned tracking 'windows' and given a precise time stamp by a rubidium atomic clock.

    Schematic of the Gaia focal plane.
    Credit: ESA - A. Short

    Next, the star images enter the photometric field where two rows of CCDs produce low-resolution spectra in different wavelength bands. The blue CCDs spread the light at wavelengths between 330 and 680 nm, while the spectrum created by the red CCDs goes from 640 to 1000 nm. These spectra are used for gathering colour information on the stars and for correction of the optical aberrations in the astrometric part of the instrument.

    Finally, the star images enter the spectroscopic field where a spectrograph only allows light in the narrow band of 847 to 874 nm. The filtered light is then dispersed over 1100 pixels to detect characteristic spectral lines in this band. Subsequent analysis on the ground enables stellar velocities in the radial (line-of-sight) direction to be calculated, based on the red or blue shifts of the spectral lines.

    Located 1.5 million km from Earth, Gaia will operate at a temperature of minus 110°C (163.15 K). This low temperature will be maintained by passive thermal control, including the cold radiator on the focal plane assembly and a giant sunshade attached to the top of the spacecraft.

    "In parallel to the assembly of the CSS, Astrium is working on the cold radiator and the proximity electronics module. We are aiming to bring together all three parts of the focal plane assembly by October of this year," noted Garé.

    Contact

    Philippe Garé
    Gaia Payload Manager
    Email: Philippe.Gareesa.int
    Phone: 31 (0)71 565 5671

    Giuseppe Sarri
    Gaia Project Manager
    Email: giuseppe.sarriesa.int
    Phone: +31 (0)71 565 4966

    Timo Prusti
    Gaia Project Scientist
    Email: tprustirssd.esa.int
    Phone: +31 (0)71 565 4794


    Last Update: 31 March 2017

    • Shortcut URL
    • http://sci.esa.int/jump.cfm?oid=48901
    • Images And Videos
    • Assembly of the Gaia CCD array (flight model)
    • Assembly of the Gaia CCD array (flight model)
    • Assembly of the Gaia CCD array (flight model)
    • The complete Gaia CCD array (flight model)
    • Gaia focal plane
    • Gaia optical bench and telescopes
    • See Also
    • Gaia focal plane

    Connect with us

    • RSS
    • Youtube
    • Twitter
    •  Flickr
    • Google+
    • Livestream
    • Subscribe
    • Twitter-2

    Follow ESA science