European mission CHEOPS joins the quest to understand exoplanets

CHEOPS mission will be studying exoplanets

3…2…1…BLAST OFF!

CHaracterising ExOPlanets Satellite, or CHEOPS, the first European mission to study exoplanets, was launched into Space TODAY, on Wednesday, December 18th, at 8:45 AM Greenwich Time from the Guiana Space Centre. The satellite blasted into space atop a Soyuz-ST rocket, the Russian launch vehicle from the same rocket family that delivers astronauts and payload to the International Space Station. Originally, the launch was due to take place 24 hours earlier, on Tuesday the 17th, but because of some software problems the take-off was postponed. Luckily, not for long! 

While NASA already has two exoplanet hunters, Keppler (now retired) and TESS, in orbit, the European Space Agency is sending off their first. Astronomers are looking forward to receiving many exciting news about the alien worlds CHEOPS is going to observe! 


While about 80% of the probe’s time will be devoted to its primary science programme, the remaining 20% will be available to the guest observers through the CHEOPS Guest Observers Programme. So far 12 proposals have been granted the precious observing time. More opportunities will come in the early 2020!


CHEOPS mission objectives

The aim of the mission is not discovery, but further research. So CHEOPS will not be looking for new exoplanets, but rather re-observe the already known ones with greater accuracy. Over the course of at least 3.5 year long service CHEOPS will explore thousands of Earth-to-Neptune sized planets that orbit bright nearby stars in order to determine their bulk densities. But how?

By analyzing passages of an exoplanet in front of its host star (this method is known as transit photometry), astronomers will be able to derive the planet’s size. Next, they will use the known mass of this planet (derived from previous observations with a radial velocity method) to calculate the planet’s density and find out whether it is rocky or gas or icy!  

To date scientists have discovered over 4000 exoplanets new exoplanets. And many of the planets CHEOPS will be looking at haven’t yet been discovered. The most interesting CHEOPS exo-worlds will be further investigated by the upcoming James Webb Telescope mission.  



CHEOPS will be observing extrasolar planets from the so-called “dusk-dawn” polar orbit. That means the satellite will be passing above both poles while always staying in the Earth’s terminator, the border between night and day sides of the planet.  The spacecraft will keep its “back” turned to the Sun to avoid stray light from the Earth and stay cool. 


What’s inside?

A rather small and lightweight satellite, CHEOPS is essentially a 30 cm optical telescope on a platform. The telescope has the same design as many other professional instruments, including the 2.4 meter Hubble Space Telescope and the two 10 meter ground-based Keck Observatory telescopes in Hawaii. 


All right. New satellite, exoplanets, high precision measurements. 

But… why?

As we know, there are billions of  “Solar Systems” out there. We expected them to be similar to our own, but the observations of these far-away worlds proved us wrong, revealing the planets we could not even imagine existed. Therefore we cannot help but ask ourselves: 

How do Earth size exoplanets form? Do they have atmospheres? How many of them are in their star’s habitable zone? And, ultimately… Are we alone in the Universe?

Hopefully, CHEOPS will take us one step closer to answering some of these questions.


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