Gaia
Gaia's name was derived as an acronym for Global Astrometric Interferometer for Astrophysics. This reflected the optical technique of interferometry that was originally planned for use on this telescope. However, the working method has now changed. Although the acronym is no longer applicable, the name Gaia remains to provide continuity with the project.
Objectives
Gaia's main scientific objective is to use its census of stars to clarify the origin and subsequent history of our galaxy, the Milky Way. As well as this, Gaia is expected to become science's greatest discovery machine. Estimates suggest that Gaia will discover the following quantities of celestial objects:
- up to a million asteroids and comets within our own Solar System;
- thirty thousand planets beyond our Solar System;
- fifty thousand failed stars, called brown dwarfs;
- hundreds of thousands of dead stellar remnants, called white dwarfs;
- twenty thousand exploding stars, called supernovae;
- hundreds of thousands of distant active galaxies, called quasars.
Cost
Industrial studies, costing roughly 15 million Euros, are currently running until 2005 and are paid by ESA. The entire mission, including launch, ground operations and payload, will cost about 450 million Euros.
Launch
Gaia is scheduled for a mid-2010 launch. It will be lifted into space using a Russian Soyuz.
Orbit
After launch, Gaia will take about 6 months to cruise to the Lagrangian point, known as L2. The L2 point is approximately 1.5 million kilometres away from Earth (about four times the distance of the Moon). This gravitational equilibrium is a position that will keep pace with the Earth and offers a less obstructed view of the cosmos, than an orbit around the Earth.
Planned mission lifetime
Gaia is designed to fulfil its mission in six years, including the six-month cruise phase.
Spacecraft
Design
The nearly circular solar array/sunshield assembly dominates Gaia's design. Above this is a geodesic dome design that houses the payload module. Below the payload is a conical service module containing essential systems such as a propulsion module, communications and power. The spacecraft is three-axis stabilized and will use its capability to slowly rotate, scanning continually as it sweeps its instruments' fields of view across space.
Mass
At launch, Gaia will possess a mass of about 1700 kg, including 800 kg of payload, a 600 kg service module and 270 kg of fuel.
Dimensions
With the solar array deployed, its total width is about 11 m. The payload dome is approximately 3 m across and 2 m high. The service module is about 3 m across and 1 m high.
Industrial involvement
At present, two major, parallel studies, known as 'system studies' are ongoing. These have been awarded to Astrium and Alenia/Alcatel. There are also about 10 separate, smaller technical studies on-going too. The prime contractor for the mission will be chosen at the conclusion of these studies, expected around 2005.
What's on board?
Gaia carries two main science instruments:
Astro There will be two identical Astro telescopes onboard Gaia. Both possess rectangular primary mirrors, instead of circular ones, that are 1.4 m by 0.5 m. A further two mirrors then bring the light to a focus. Each instrument looks at a different section of sky, separated by 106 degrees. A suite of about 200 Charge Coupled Device (CCD) detectors will image celestial objects. They will precisely map the position of the stars and chart any movement across the sky, during Gaia's mission.
Spectro Spectro contains a smaller primary mirror than the Astro units, at just 0.5 m on a side. However, it too is a three-mirror telescope. Its view of the cosmos will be captured by five large CCD detectors, three of which will provide spectroscopic information so that the movement of the stars along the line of sight can be measured.
Both instruments are being paid for by ESA and will be the collective responsibility of ESA, its industrial partners and its science teams.
Operations
Ground control and all science operations will be conducted from the European Space Operations Centre (ESOC, Darmstadt, Germany), using the ground stations at Perth (Australia) and Kourou (French Guiana) during launch.
ESA Mission Manager and Project Scientist: Michael Perryman
ESA Study Manager: Oscar Pace
For further information please contact:
ESA Science Programme Communication Service
tel: +31 71 565 3273
fax: +31 71 565 4101
ESA Media Relations Service
tel: +33 1 5369 7155
fax: +33 1 5369 7690