Gaia

Spacecraft n⩝:

ESA spacecraft nº: 85

Launch data: Designation  39479 / 13074A Launch date  19 Dec 2013 - 09:12 UT Launch site  Ko, ELS Launch vehicle  Soyuz-2-1B/Fregat-MT Mission  Astrometry L-2 orbit: Perigee / Apogee   km Eccentricity   Inclination   deg Period   min

Spacecraft data: Prime manufacturer  Astrium Platform   Operator  ESA Mass at launch  2030 kg Dry Mass   kg Basic shape   Dimension (m)   Equipment  2 Astro telescopes, 1 Spectro telescope Solar array  Solar cells Stabilization   Propulsion   DC power   Design lifetime  5 yrs

Gaia heat shield deployment at Astrium Toulouse - Credit: Astrium / D. Eskenazi / 2011

Gaia departure from Toulouse - Credit: Astrium / 2013 / D. Eskenazi

Description:

• Gaia is an unmanned space observatory of the European Space Agency (ESA) designed for astrometry. The mission aims to compile a 3D space catalogue of approximately 1 billion astronomical objects (approximately 1% of the Milky way population)brighter than 20 G magnitudes where G is the Gaia magnitude passband between about 400 and 1000 nanometres light wavelengths. Successor to the Hipparcos mission, it is part of ESA's Horizon 2000 Plus long-term scientific program. Gaia will monitor each of its target stars about 70 times over a period of five years.
• The Gaia mission was proposed in 1993 by Swedish astronomer Lennart Lindegren of Lund University. Twenty years later, his idea will be taking to the skies. Lindegren, one of the world’s foremost astrometry experts, points out that Gaia will also test out with greater precision than ever Einstein’s theory of relativity, which states that mass causes spacetime to curve. Even light rays are bent when they pass near a massive object such as the sun.
• The 2000 kg Gaia spacecraft will measure the three-dimensional positions and velocities of galactic stars. The problem of accurate stellar distances has been a limiting factor in astrophysics with big uncertainties leading to uncertain masses, luminosities and other physical properties for all but the nearest stars; the Gaia catalog, when it is available early next decade, will put the whole field of astrophysics on a firmer footing. Gaia will spin around, with its two 1.5 x 0.5m silicon carbide primary mirrors sweeping starlight across its gigapixel detector array.
• The array has 106 CCDs each with 4500 x 1996 pixels. The SkyMapper array of 7 x 2 CCDs and the 7 x 9 array of Astrometric Field CCDs will measure positions; the 7 x 2 array of the Blue and Red photometer will pass the light through blue and red filters to measure accurate brightness and color; and the 4 x 3 array of the Radial Velocity Spectrometer CCDs will sit behind a spectrograph and use the 8500A Ca II triplet spectral lines to measure the Doppler shift of the brighter stars along the line of sight. The angular separation of the two mirrors is precisely monitored, to create an accurate latitude-longitude grid across the sky by measuring angular distances between widely separated pairs of stars.

Mission details:

• The European Space Agency's Gaia observatory was launched on Dec 19, 2013.
  Gaia was launched by a Soyuz ST-B with upper stage Fregat-MT No. 1039 from Kourou-Sinnamary. The Soyuz reached a -681 x 180 km x 15.0 deg suborbital path; the Fregat made a first burn to 175 x 175 km and then reignited for a long burn from 0933 to 0949 UTC to propel Gaia to a 344 x 962690 km x 15.0 deg orbit, on its way to the Sun-Earth L2 point.
• Gaia will fire its own propulsion system of 6 10-N thrusters to raise apogee to around 1.5 million km towards midnight; in a few weeks it will enter a Lissajous orbit around the L2 point and begin observations. Gaia's data will take years to process and will result in the best yet catalog of galactic stars.
• The Gaia astronomical observatory made the first of two critical L2 insertion burns on Jan 7, 2014. Thrusters fired from 1858 to 2014 UTC. After a second burn on Jan 14, Gaia entered a 263000 x 707000 x 370000 km Lissajous orbit around the Sun-Earth L2 point. Gaia's CCDs are working and observations of stars are underway.

Satellite tracking: