Planned launch of the CHEOPS satellite on December 17

The space telescope CHEOPS is scheduled to begin its journey into space on Tuesday, December 17th on board a Soyuz rocket from the European Space Agency (ESA) in Kourou, French Guiana. CHEOPS is a joint mission of ESA and Switzerland, led by the University of Bern, in collaboration with the University of Geneva.



CHEOPS is a scientific satellite of the European Space Agency built under Swiss leadership, notably by the University of Geneva (UNIGE). It is put into orbit at the end of 2019, in order to study exoplanets orbiting bright stars. © UNIGE/ESA


CHEOPS (short for CHaracterising ExOPlanet Satellite) consists of a space telescope developed and assembled by the University of Bern, in collaboration with the University of Geneva (UNIGE),  and a satellite platform that carries the telescope and allows the control of the satellite from the ground. CHEOPS, which will be operated by the University of Geneva, is the first mission jointly run by Switzerland and ESA. The mission serves to study exoplanets by observing the stars around which the planets orbit. CHEOPS will measure the minuscule changes in brightness which occur when a planet passes in front of its host star. These changes being proportional to the surface of the transiting planet, CHEOPS will allow to measure the size of the planets.


The mission targets stars which are orbited by planets with dimensions ranging from Earth-like to Neptune-like with the goal to obtain the most precise possible measurement of their size. This data, together with available information about the masses of the planets, will provide their mean density. This means that scientists will be able to obtain key information about the bulk composition and structure of these planets – for example, whether they are predominantly rocky or made up of gases, or whether there are deep oceans on them. In turn, this is a decisive step for determining the probability of these planets to be habitable.


"Every rocket launch is a sensitive moment"

In August 2019, CHEOPS passed the last tests at Airbus in Madrid. Willy Benz, astrophysics professor at the University of Bern and principal investigator of the CHEOPS mission, says: "After over six years of intensive work, I am of course very pleased that the launch is finally in sight.” CHEOPS is now expected to start its journey into space on board a Soyuz rocket on Tuesday, December 17th, 2019, shortly before 10 a.m. in our time zone (6 a.m. local time). The multinational company Arianespace is responsible for the rocket launch. CHEOPS will start its journey into space together with a satellite which belongs to the Italian Cosmo-SkyMed satellite program. The carrier rocket will also have five small satellites, so-called "CubeSats" on board. Willy Benz will travel to Kourou with a Swiss delegation, including the 2019 Nobel Prize in Physics Didier Queloz, Professor at the Universities of Geneva and Cambridge, for the launch. "A rocket launch is always a delicate and stressful moment where quite a few things can go wrong. In addition, poor weather conditions could also prevent the launch which is set very close before Christmas", explains Willy Benz.

After the launch, it will take approx. 140 minutes until CHEOPS leaves the rocket and orbits the earth at around 700 km height. The first data is expected at the beginning of 2020. While the CHEOPS Mission Control Center is based in Madrid, the CHEOPS Science Operations Center is in Geneva, the second Swiss partner university of the experiment. David Ehrenreich, CHEOPS Mission Scientist at the at the Observatory of the Faculty of Science of the UNIGE, says: "I too will only really be able to sleep peacefully again once CHEOPS has reached its orbit and is fully functional."

The mission presents an excellent opportunity for scientists world-wide, explains Kate Isaak, ESA Project Scientist: “With twenty percent of the observing time available through the ESA-run Guest Observers Programme, scientists from around the world will be able to capitalise directly on the unique capabilities of CHEOPS.”

The launch of CHEOPS is a great moment for everyone involved, but in particular for Switzerland as well, as David Ehrenreich highlights: "CHEOPS was developed thanks to good collaboration between Swiss universities, led by the University of Bern and the industry – this shows once again that Switzerland is a space faring nation."

6 Dec 2019