Space telescope set to study planets orbiting other stars

CHEOPS (Characterising Exoplanets Satellite), which is classed as a low-cost mission with a budget of €50m (£40m) and is due to launch in 2017, is designed to act as the next stage in exoplanet research from terrestrial telescopes.

It will look at targets chosen through ground-based research that can establish whether stars have orbiting planets but cannot determine much information about them.

In one set of studies focusing on Earth-sized planets, CHEOPS will determine whether these planets have atmospheres. In another set focusing stars on larger hot planets, it will look for possible accompanying smaller planets that previous observations could not see.

The satellite is designed specifically to look at star systems relatively close to our solar system, selecting targets that could then be studied further by the next generation of telescopes.

These include enormous ground-based observatories such as the 39m European Extremely Large Telescope, scheduled to start operations early next decade, and the James Webb Space Telescope, set for launch in 2018.

The CHEOPS telescope will be relatively small — the primary mirror is planned to be 33.5cm in diameter, compared with 6.5m for the James Webb — but will target bright stars.

Its main goal will be to look for the difference in the light from its target star as the planet passes in front of it, so it will be designed to be as robust as possible, resistant to changes in temperature, and will be equipped with a large light shield to prevent stray light, such as the reflected light from the Earth, from reaching its receptors.

It will also be placed in an orbit that will allow it to look at any part of the sky, maximising the number of star systems it will be able to study.

The scientific part of the CHEOPS mission is a collaboration between 13 institutions in Austria, Belgium, Switzerland, Italy, Sweden and the UK, with exoplanet specialist Don Pollacco of Warwick University’s physics department leading the UK’s part of the project. ESA has not yet determined where the spacecraft will be built.