The 0.3 m CHEOPS satellite is ready for launch!

CHEOPS stands for CHaracterising ExOPlanets Satellite. It is the first European Space Agency (ESA) mission dedicated to the study of exoplanets, planets located outside of our Solar System. Planned for launch on December 17 in a Soyuz-Fregat rocket from Kourou in French Guiana, this space telescope will share the rocket space with additional instruments: the Italian Cosmo-SkyMed satellite,  ESA’s OPS-SAT, and two CubeSats (ANGELS and EYE-SAT) developed by the Centre National d’Etudes Spatiales (CNES)

Unlike previous exoplanets missions, such as CoRoT (2006-2013), Kepler (2009-2018), or Tess (2018-present), CHEOPS satellite is not an exoplanet finder. Its main objective is to characterize known exoplanets larger than Earth and smaller than Neptune. It will measure radii of known exoplanets that we know the mass, measured with ground-based telescopes. If you know the mass and the size of the exoplanet, you can find the planets’ density and then know if the planet is gaseous or rocky. It’s the first step to determine exoplanets composition, internal structure, and to identify potential targets for future observations.

CHEOPS satellite will measure the starlight variation when a known exoplanet transits in front of its parent star. This technique is called high precision transit photometry. When the planet passes in front of its star, the starlight dims and creates a lightcurve. The depth and the shape of the lightcurve allows determining planet characteristics and if it has moons or rings. As of today, we know 4,143 planets discovered around other stars. About 71.6% were discovered with the transit method, a method used to find exoplanets size and orbital parameters.

Transit photometry. Copyright: ESA.

Who developed CHEOPS?

The CHEOPS mission is a partnership between ESA and the University of Bern in Switzerland. A consortium of 11 European countries have contributed to CHEOPS, including Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, Switzerland, and the UK. In Spain, Airbus Defence and Space designed and constructed the spacecraft.

Just a 30 cm telescope!

CHEOPS is a 30 cm Ritchey-Chrétien space telescope with a 0.32 degrees field of view (FOV). Its primary mirror is 8 times smaller than the Hubble Space Telescope! The spacecraft will be placed into a 700 km altitude Sun synchronous orbit. With a size of 1.5 m and a mass of 300 kg, the CHEOPS spacecraft is very compact. The mission duration is at least 3.5 years.The optical system provides a de-focused image on the focal plane. A large external baffle minimizes straylight. The telescope includes a single frame-transfer backside illuminated CCD detector with very low noise. The CCD, working at wavelengths between 330 and 1,100 nm, is cooled at 233 K (-40 °C) and has a thermal stability close to 10 mK! 

Watch the live stream launch

CHEOPS is set for launch on December 17. Follow the web live stream at on 17 December, at 09:30 CET (Central European Time):

  • 09:54 CET: Liftoff
  • 2.5 hours later: CHEOPS separation
  • 3 hours later: Signal acquisition

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