- Searching for rocky planets outside our Solar System, COROT is an important stepping stone in the European effort to find habitable, Earth-like planets around other stars.
- By studying the acoustical waves rippling across the surfaces of stars, with waves as high as a few meters, one can penetrate into the so far ‘invisible’ stellar interiors and learn about the physics of stars. This is the engine driving the most important energy source in our universe, which creates the environment necessary for life on the surface of planets.
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COROT is the first mission capable of detecting rocky planets, several times larger than Earth, around nearby stars (planets outside our Solar System are referred to as ‘exoplanets’). It consists of a 30-centimetre space telescope. It was launched on 27 December 2006.
COROT will use its telescope to monitor closely the changes in a star’s brightness that comes from a planet crossing in front of it. While it is looking at a star, COROT will also be able to detect ‘starquakes’, acoustical waves generated deep inside a star that send ripples across a star’s surface, altering its brightness. The exact nature of the ripples allows astronomers to calculate the star's precise mass, age and chemical composition.
This technique is known as asteroseismology and ESA’s Solar and Heliospheric Observatory (SOHO) has been taking similar observations of the Sun for years. The COROT data is therefore essential to compare the Sun with other stars.
From the ground, the only planets detected around other stars have been giant gaseous worlds (Jupiter-like planets), over 10 times the diameter of the Earth. Not affected by the distorting effects of the atmosphere, COROT will be the first spacecraft capable of finding worlds made of rocks.
Such rocky worlds are smaller than the gas giants but several times larger than the Earth, itself the biggest rocky planet in the Solar System. Such planets would represent a new, as yet undiscovered, class of world that astronomers believe exists. With COROT, astronomers expect to find between 10-40 of them, together with tens of new gas giants, in each star field that COROT will observe. Every 150 days COROT will move to a new field and begin observing again.
ESA then plans to continue its search for Earth-like worlds into the second decade of the century with the launch of the Darwin mission. This flotilla of 4 or 5 spacecraft will take pictures of Earth-like worlds, allowing scientists to search for signs of life.
The payload of the COROT satellite consists of a telescope, two cameras - one for each of the two mission objectives (exoplanet search and asteroseismology), and the on-board computer processors. The latter were manufactured in ESA's European Space Research and Technology Centre (ESTEC) by the Research and Scientific Support Department as one contribution of ESA to the COROT mission.
The telescope is made out of two parabolic mirrors, having a 1.1-metre focal length. The field of view is a square of 2.8 x 2.8°, half for the seismology mission, the other half for the exoplanet mission. A prism, used by the telescope for certain aspects of the mission, will separate colours, enabling scientists to study stellar activity during a planetary transit.
There is an external ‘baffle’ on the telescope (designed at ESTEC). This is a device for shielding a lens from ‘light pollution’ from sources other than those objects at which the telescope is looking.
After launch, COROT was placed on a circular, polar orbit that allows for continuous observations of two large and opposite regions in the sky for more than 150 days each. Within each region there are many selected fields that will be monitored in turn. The reason for the oppositely sited regions is that, because of the Earth’s movement around the Sun, the sun’s rays start to interfere with the observations after 150 days. COROT then rotates by 180 degrees and start observing the other region.
COROT was first proposed in December 1996 by the French National Space Agency (CNES) and, over the next three years, the project was researched to see if it was feasible. In September 1999, a call for potential European partners was made and in March 2000, CNES gave the green light to carry out COROT.
COROT is a mission led by the French national space agency, CNES. ESA has joined the mission by providing the optics for the telescope and testing of the payload. Through this collaboration a number of European scientists have been selected as Co-Investigators in open competition. They come from Denmark, Switzerland, the UK and Portugal. As a result of ESA’s participation in COROT, scientists from ESA’s Member States will be given access to the satellite’s data. The baffle of the telescope has also been developed by a team at ESA’s ESTEC site.
ESA’s Research and Scientific Support department (RSSD) at ESTEC is a full partner in COROT by providing the on-board Data Processing Units (DPU’s). Other partners in COROT are Austria, Spain, Germany, Belgium and Brazil.
The ground stations used for COROT are located in Kiruna (S), Aussaguel (F) Hartebeesthoek (South Africa), Kourou (French Guyana), with mission-specific ground stations in Alcantara (Brazil) and Vienna (A).