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European satellite's mission to study exoplanets

Charles Black, Founder and CEO of Sen
Oct 20, 2012, 7:00 UTC

Sen—The European Space Agency (ESA) has announced plans for a new mission to study exoplanets. ESA hopes to launch the satellite in 2017. It comes as it was announced this week that a planet with a similar mass to Earth was detected in our nearest star system, Alpha Centauri. 

The mission, called Cheops - CHaracterising ExOPlanets Satellite - will target nearby bright stars which are already known to have planets. It's the first of a series of smaller missions developed as part of the space agency's Science Programme.

Cheops will monitor the brightness of our nearest stars to look for signs of transits, where planets cross in front of the star. In turn, this will allow an accurate measurement of the radius of a transiting planet. Scientists then hope to calculate the density of these planets where the mass is already known. This will then help to provide information about the internal structure.

According to Professor Alvaro Giménez-Cañete, ESA Director of Science and Robotic Exploration "by concentrating on specific known exoplanet host stars, Cheops will enable scientists to conduct comparative studies of planets down to the mass of Earth with a precision that simply cannot be achieved from the ground."

The idea is to help scientists understand the formation of planets, up to the size of the planet Neptune. The mission also aims to identify planets with significant atmospheres.

Information from Cheops will then be used to provide targets for further detailed studies of exoplanet atmospheres by the future telescopes such as the James Webb Space Telescope, which is targeted to launch in 2018, and the European Extremely Large Telescope, which should be ready for use by 2022.

Artist illustration of Cheops. Credit: University of Bern

Artist's impression of Cheops. Credit: University of Bern

The mission was selected from 26 proposals submitted in response to the Call for Small Missions in March. Professor Giménez-Cañete said this highlighted "the strong interest of the scientific community in dedicated, quick-turnaround missions focusing on key open issues in space science."

The idea of the small missions for ESA's Science Programme is to support low cost, quick turnaround missions, therefore offering more flexibility to respond to new ideas. 

Cheops has a lifetime of about three and a half years and will operate in a Sun-synchronous low-Earth orbit at an altitude of 800 km. Part of the observing time will be open to the wider scientific community. The mission will be run as a partnership between ESA and Switzerland, with contributions from a number of other ESA Member States.