Ruprecht-Karls-Universität Heidelberg

Gaia project at ARI

Gaia is a big astrometry mission by the European Space Agency ESA.  The Gaia satellite was launched in December 19, 2013. Commissioning of the satellite officially ended on July 18. After a short calibration period of 28 days the regular scientific measurements started.

Gaia measures the positions, parallaxes, proper motions, luminosities and colours of more than 1 billion stars with unprecedented precision, complemented by radial velcities and spectra of 100 million stars. Its main goal is to elucidate the structure, formation and evolution of the Milky Way.

On September 14, 2016 the first Gaia catalogue (Gaia DR1) was published with

  • Positions (α, δ) and G magnitudes for all sources with acceptable formal standard errors on positions (insgesamt 1,142,679,769 entries).
  • The five-parameter astrometric solution - positions, parallaxes, and proper motions - for 2,057,050 stars in common between the Tycho-2 Catalogue and Gaia is contained in Gaia DR1.
  • At the beginning of the routine phase, for a period of 4 weeks, a special scanning mode repeatedly covering the ecliptic poles on every spin was executed for calibration purposes. Photometric data of selected RR Lyrae (2595) and Cepheid (599) variable stars including these high-cadence measurements are contained in Gaia DR1.
  • Positions (α, δ) and G magnitudes for 2152 ICRF quasars.

A very big step was made on Apri 25, 2018: The second Gaia data release (Gaia DR2), the first one that did not use an additional catalogue like the Tycho-2 catalogue came out:

  • The five-parameter astrometric solution - positions on the sky (α, δ), parallaxes, and proper motions - for more than 1.3 billion (109) sources.
  • Median radial velocities (i.e. the median value over the epochs) for more than 7.2 million stars.
  • Positions (two-parameter solution2) for more than 361 million sources.
  • G magnitudes for more than 1.69 billion sources.
  • GBP and GRP magnitudes for more than 1.38 billion sources.
  • Epoch astrometry for 14,099 known asteroids.
  • Effective temperatures Teff for more than 161 million sources.
  • Classifications for more than 550,000 variable stars.

The scientific data reduction for the Gaia mission is being prepared by the pan-European Data Processing and Analysis Consortium (DPAC, external link).

At ARI DR1 and DR2 are available on

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