The quest to track down Earth-like planets outside of the Solar System is to be boosted with the launch of a new mission.
Corot (COnvection, ROtation and planetary Transits), which is due to launch on 27 December, will be capable of detecting small rocky planets of a similar size to our own.
Corot will be the first spacecraft able to detect rocky planets down to about twice Earth's size that are orbiting neighbouring stars.
Corot can spot small rocky planets
At present, our knowledge of Earth-sized exoplanets (planets that exist outside of the Solar System) has been limited, as they are very difficult to locate from the ground.
The smallest exoplanet so far found is over five times more massive than the Earth.
But it has been estimated that Corot will find perhaps hundreds of these rocky planets, as well as many larger gas giants as it scours the sky.
Identifying planets similar to Earth is critical in the hunt for extra-terrestrial life. The data from Corot will aid future planned explorations to locate Earth-like worlds.
The mission has a second objective: to find out more about stars themselves.
Corot will provide data on the bodies' mass, age and chemical composition.
This information will be used to compare the Sun with other stars.
HOW IT WORKS
1. 4CCD camera and electronics: Captures and analyses starlight
2. Baffle: Works to shield the telescope from extraneous light
3. Telescope: A 30cm mirror; it views the star fields
4. Proteus platform: Contains communication equipment, temperature controls and direction controls
5. Solar panel: Uses the Sun's radiation to power the satellite
The 650kg (1,400lb) satellite contains a 27cm (11in) telescope and a four-charge-coupled-device (CCD) camera.
With this equipment, it can detect the tiny changes in brightness in the tens of thousands of stars it is viewing.
Corot is looking for relatively rare events in which a planet crosses in front of its parent star, as viewed from the Earth. This blocks out some of the star's light, causing a tiny dip in its brightness that Corot is tuned to detect.
Every 512 seconds the camera on board can monitor about 10,000 stars in its field to capture any of these small variations in brightness.
Finding a transit will involve a bit luck
The team hopes to find between 10 and 40 planets in each of the five or six star regions it will be looking in, along with hundreds of new gas giant planets similar to our Jupiter.
Simultaneously, the satellite will be probing the insides of stars using a technique called astroseismology.
Similar to seismology, which employs the waves from earthquakes to uncover details about the Earth's interior, Corot will use "starquakes" - waves generated deep inside a star that send ripples across its surface - to learn about more about the object's internal processes.
Starquakes also cause the star's brightness to vary, and Corot's instrumentation is tuned to capture these characteristic changes.
The launch date for the mission is 27 December. Corot will be lofted on a Soyuz-2-1b vehicle from the Baikonur Cosmodrome, Kazakhstan, into a circular polar orbit 827km (514 miles) above the Earth.
After a month spent checking the onboard instruments, Corot will begin its observations of surrounding star fields.
It will focus on five to six different areas of the sky, each time for duration of about 150 days.
The mission is scheduled to last approximately 2.5 years.
Corot is a multinational mission led by the French space agency, Cnes. There are six partners involved: the European Space Agency (Esa), Austria, Spain, Germany, Belgium and Brazil.