Case study


A mission that will examine the Milky Way in unprecedented 3D detail, mapping stars and their movements.

Gaia spacecraft.
Artist's impression of the Gaia spacecraft. Credit: ESA.

The spacecraft is currently surveying more than one billion stars to make the largest, most precise map of our Galaxy to date. Gaia is continuously scanning the sky enabling each object to be observed on average about 80 times. Gaia logs the position, brightness and colour of every celestial object of sufficient brightness that falls within its field of view. Gaia is using the same principle of measurements that was successfully employed by the Hipparcos.

Mission overview:

  • in development since 2007
  • successfully launched 19th December 2013
  • following a four month commissioning phase, GAIA began its science mission in 2014
  • first set of data released 14 September 2016

The repeated observations are enabling astronomers to calculate positions, distances and velocities relative to the Sun for the objects that are observed. Any variations in brightness are being followed and analysed. With this wealth of data, astronomers are gaining a better understanding of the history and evolution of our Galaxy.

Gaia is able to detect large numbers of double stars throughout the Milky Way, as well as nearby planets that are the same size - or bigger - than Jupiter. It does this by measuring small disturbances in the positions of stars caused by a planet’s gravitational field. Scientists predict Gaia could find up to 50,000 planets during its five-year mission!

First data release

On 14 September 2016, the European Space Agency (ESA) announced that during its first 14 months, Gaia had pinned down the precise position in the sky of 1142 million stars.

The UK plays a significant role in data processing. Groups involve Cambridge, Edinburgh, University College London’s Mullard Space Science Laboratory, Leicester, Rutherford Appleton Lab (RAL) and Bristol are all key players in the processing of raw data.

This Gaia data release marks the first chance astronomers and the public have had to get their hands on the most detailed map ever made of the sky. Gaia has already been producing early scientific results over the past two years in the form of Gaia Alerts identified and released by the Cambridge team.

There is a wide range of Gaia’s discoveries arising from Science Alerts – supernovae of various types, cataclysmic variable stars, novae, flaring stars, gravitational microlensing events, active galactic nuclei and quasars, and many sources whose nature remains a mystery. These are made publically available and are followed up by astronomers and school groups.

Mission facts

Gaia originally stood for Global Astrometric Interferometer for Astrophysics. As the project evolved, the double-interferometer concept was replaced with different instruments. However, the mission name remained even though it no longer uses an interferometer as part of its telescope design.

The measurement accuracy expected for Gaia is about 10 to 100 times greater than what was achieved for the Hipparcos mission. The number of objects observed will be 10,000 times greater.

As part of its mission, Gaia is expected to detect tens of thousands of stars that failed to ignite. These are known as brown dwarves. The information gathered will help scientists understand the formation of stars. Technology

Gaia will be equipped with two telescopes, projecting images onto a single integrated camera instrument. They record the position, brightness and colour of the objects under observation.

The spacecraft is equipped with a ‘micro propulsion’ system, allowing fine adjustments to be made to its position.

UK involvement

Gaia is one of the most important space projects for the UK, having provided about €80M of contracts from ESA (European Space Agency) to build the spacecraft.

EADS Astrium at Stevenage was responsible for the spacecraft’s super precision guidance and control system as well as the powerful computers needed to process the torrent of data it will produce.

The ‘eye’ of Gaia’s camera is the most sensitive set of light detectors ever assembled for a space mission. It uses 106 CCDs made by UK company E2V Ltd with nearly 1 billion pixels covering an area of 2.8 square metres. The UK Space Agency is funding a £14M project with institutes across the UK. Cambridge leads the prime photometric processing and real-time science unit, and along with Leicester, Edinburgh and Rutherford Appleton Laboratory (RAL) are undertaking activities such as database definition and construction, framework development, development, verification testing and final integration of the data.

University College London’s Mullard Space Science Laboratory (MSSL) has a major role in spectroscopic science and is involved in software development including architecture, integration and validation, pre-processing development, spectra extraction and calibration of the data.

SciSys UK Ltd are responsible for the spacecraft’s operational simulator. Also in the UK, Selex Systems are providing system support, Aero Stanrew Ltd provided the avionics test bench, and ABSL provided the battery.

For more detailed information, see ESA’s Gaia mission homepage.

Published 28 April 2014