Airbus Defence and Space, the world's second largest space company, has become the prime contractor for the CHEOPS (CHaracterising ExOPlanet Satellite) satellite, the first small type mission of ESA's (European Space Agency) Scientific Programme. The main objective of the CHEOPS mission is to monitor planetary transits by means of ultrahigh precision photometry on known stars that have planets orbiting them.

The CHEOPS mission formed a very important part in the celebration of ESA's 50th anniversary at the European Astronomy Centre of ESA, in Madrid, in the presence of the President of the Spanish Government, Mariano Rajoy, and ESA's Director General, Jean Jacques Dordain. Also present at the event were the Spanish Minister of Industry, Jose M. Soria, ESA's Director of Science and Robotic Exploration, Alvaro Gimenez, and the Spanish astronaut, Pedro Duque.

In monitoring the brightness of a star, scientists will look for signs of "transit" of a planet as it passes briefly in front of its star. The satellite will thus be able to determine the exact radius of the planet.

For planets with known masses, this will allow their density to be ascertained, providing an indication of their internal structure, formation and evolution. A second goal is to provide golden targets for in-depth characterisation using future ground (eg. European Extremely Large Telescope) and space-based (eg. James Webb Space Telescope) spectroscopic facilities.

"The mission represents a challenge for both ESA and industry, as it requires a very demanding development programme in terms of design, quality and planning in order to achieve launch in 2017," said Francois Auque, Head of Space Systems. "I'm confident that our teams, building on their expertise in small Earth Observation missions such as Ingenio and Sentinel-5 Precursor will rise to this latest scientific challenge."

CHEOPS is the first of the small-size (S class) missions of ESA, and was selected from 26 other proposed missions. These missions are designed to take full advantage of known technologies.

They should be low cost and rapidly developed missions, in order to offer greater flexibility in response to new ideas from the scientific community. The spacecraft is based on the Airbus Defence and Space AstroBus family of low cost satellite platforms (following on from e.g. Spot 6 and 7, KazEOSat-1), and the ninth for an ESA programme following on from Sentinel 5 Precursor and the MetOp Second Generation satellites.

Airbus Defence and Space's leadership as a satellite prime contractor in Spain is confirmed with CHEOPS, following the successful Ingenio and Paz programs. The company will re-use their experience on the AstroBus family in order to deliver CHEOPS on time.

The satellite will fly at an altitude of between 650 and 800km, in a dusk-dawn helio-synchronous orbit at an inclination of about 98 degrees, and will have a design lifetime of 3.5 years. The University of Bern is building the satellite's on-board instrument CIS (CHEOPS Instrument System) which features a 33.5cm-diameter Ritchey-Chretien telescope and a high performance backside illuminated CCD (Charge-Coupled Device) detector.