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Characterising Exoplanets Satellite
CHEOPS spacecraft
Artist's impression of the CHEOPS spacecraft bus
OperatorSwiss Space Office
Mission durationPlanned: 3.5 years
Spacecraft properties
Spacecraft typeSpace observatory
BusSEOSAT platform
ManufacturerAirbus Defence and Space
Launch mass~300 kg (660 lb)
Payload mass58 kg (128 lb)
Dimensions1.5 x 1.5 x 1.5 m
Power~64 watts[1]
Start of mission
Launch datePlanned: 17 December 2019[2]
RocketSoyuz VS23[3][4]
Launch siteGuiana Space Centre
(Ensemble de Lancement Soyouz)
Orbital parameters
Reference systemGeocentric
RegimeSun-synchronous 6 am/pm
Perigee altitude700 km (430 mi)[6]
Apogee altitude700 km (430 mi)[6]
frame-transfer back-side illuminated CCD
Diameter32 cm (13 in)[6]
Focal lengthF/8
Wavelengths330-1100 nm
CHEOPS mission logo
ESA astrophysics insignia for CHEOPS  

CHEOPS (CHaracterising ExOPlanets Satellite) is a planned European space telescope for the study of the formation of extrasolar planets. The launch is planned for December 2019.[2]

The mission aims to bring an optical Ritchey–Chrétien telescope with an aperture of 30 cm, mounted on a standard small satellite platform, into a Sun-synchronous orbit of about 700 km (430 mi) altitude. For the planned mission duration of 3.5 years, CHEOPS is to examine known transiting exoplanets orbiting bright and nearby stars.[7]


Organized as a partnership between the European Space Agency (ESA) and the Swiss Space Office, CHEOPS was selected in October 2012 from among 26 proposals as the first S-class ("small") space mission in ESA's Cosmic Vision programme.[7] ESA is the mission architect and responsible for the spacecraft and launch opportunity procurement. The project is led by the Center for Space and Habitability at the University of Bern, Switzerland, with contributions from other Swiss and European universities. The principal investigator for the science instrument is Willy Benz from the University of Bern. After a competition phase, Airbus Defence and Space in Spain was selected as the spacecraft builder.[3] The mission is cost capped at €50 million.[3]


The main goal of CHEOPS will be to accurately measure the radii of the exoplanets for which ground-based spectroscopic surveys have already provided mass estimates. Knowing both the mass and the size of the exoplanets will allow scientists to determine the planets' density and thus their approximate composition, such as whether they are gaseous or rocky. CHEOPS will be the most efficient instrument to search for shallow transits and to determine accurate radii for known exoplanets in the super-Earth to Neptune mass range (1-6 Earth radius).[3]

CHEOPS will measure photometric signals with a precision limited by stellar photon noise of 150 ppm/min for a 9th magnitude star. This corresponds to the transit of an Earth-sized planet orbiting a star of 0.9 R in 60 days detected with a S/Ntransit >10 (100 ppm transit depth). For example, an Earth-size transit across a G star creates an 80 ppm depth.

The spacecraft is to be powered by solar panels that are also part of its sunshield. They will provide 60 W continuous power for instrument operations and allow for at least a 1.2 gigabit/day data downlink capacity.[8]

Observation priorities[edit]

80% of the science observing time on CHEOPS is dedicated to the CHEOPS Guaranteed Time Observing (GTO) Programme, under the responsibility of the CHEOPS Science Team (chaired by Didier Queloz).[9] The majority of the GTO programme involves the characterization of known transiting exoplanets and improvement of known parameters. Part of the GTO programme is to find transits of known exoplanets that were confirmed by other techniques, such as radial-velocity, but not by the transit-method. Another part of the GTO programme includes exploration of multi-systems and search of additional planets in those systems, for example using the transit-timing-variation (TTV) method.[10]

The other 20% of the science observing time on CHEOPS is made available to the scientific community in the form of an ESA-run Guest Observers' (GO) Programme. Researchers can submit proposals for observations with CHEOPS through an annual Announcements of Opportunity (AO) Program.[11] The approved AO-1 projects include observations of the hot jupiters HD 17156 b, Kelt-22A b,[12] warm jupiter K2-139b,[13] multi systems GJ 9827, K2-138, the exoplanet DS Tuc Ab found by TESS[14] and other exoplanet science related observations, such as planets around rapidly-rotating stars, planet material around white dwarfs and searching for transiting exocomets around 5 Vulpeculae.[15]

See also[edit]

  • CoRoT, planet-hunting space observatory operational from 2006 to 2012
  • Kepler, planet-hunting space observatory operational from 2009 to 2018
  • MOST, Canadian, operational from 2003 to 2019
  • PLATO, planned for launch in 2026
  • TESS, planet-hunting space observatory launched in 2018
  • List of proposed space observatories


  1. ^ CHEOPS - Executive Summary
  2. ^ a b 'We've found dozens of potentially habitable planets - now we need to study them in detail'. Jonathan O'Callaghan, Horizon Magazine. Published by PhysOrg. 4 November 2017.
  3. ^ a b c d CHEOPS exoplanet mission meets key milestones en route to 2017 launch. ESA, 11 July 2014
  4. ^ CHEOPS has arrived in Kourou. Barbara Vonarburg. 16 October 2019.
  5. ^ "CHEOPS will ride on a Soyuz rocket". 6 April 2017. Retrieved 19 September 2017.
  6. ^ a b c d CHEOPS - Mission Status & Summary
  7. ^ a b "ESA Science Programme's new small satellite will study super-Earths". ESA press release. 19 October 2012. Retrieved 19 October 2012.
  8. ^ CHEOPS - Requirements
  9. ^ "The CHEOPS Guaranteed Time Observing Programme - CHEOPS - Cosmos". Retrieved 2019-11-15.
  10. ^ "CHEOPS GTO program: GTO v1.4". 2019-03-19.
  11. ^ "CHEOPS Guest Observers Programme - CHEOPS Guest Observers Programme - Cosmos". Retrieved 2019-11-15.
  12. ^ Labadie-Bartz, Jonathan; Rodriguez, Joseph E.; Stassun, Keivan G.; Ciardi, David R.; Penev, Kaloyan; Johnson, Marshall C.; Gaudi, B. Scott; Colón, Knicole D.; Bieryla, Allyson; Latham, David W.; Pepper, Joshua (2019-01-21). "KELT-22Ab: A Massive, Short-Period Hot Jupiter Transiting a Near-solar Twin". The Astrophysical Journal Supplement Series. 240 (1): 13. arXiv:1803.07559. doi:10.3847/1538-4365/aaee7e. ISSN 1538-4365.
  13. ^ Barragán, O.; Gandolfi, D.; Smith, A. M. S.; Deeg, H. J.; Fridlund, M. C. V.; Persson, C. M.; Donati, P.; Endl, M.; Csizmadia, Sz; Grziwa, S.; Nespral, D. (2018-04-01). "K2-139 b: a low-mass warm Jupiter on a 29-d orbit transiting an active K0 V star". Monthly Notices of the Royal Astronomical Society. 475 (2): 1765–1776. arXiv:1702.00691. doi:10.1093/mnras/stx3207. ISSN 0035-8711.
  14. ^ Newton, Elisabeth R.; Mann, Andrew W.; Tofflemire, Benjamin M.; Pearce, Logan; Rizzuto, Aaron C.; Vanderburg, Andrew; Martinez, Raquel A.; Wang, Jason J.; Ruffio, Jean-Baptiste; Kraus, Adam L.; Johnson, Marshall C. (2019-07-23). "TESS Hunt for Young and Maturing Exoplanets (THYME): A Planet in the 45 Myr Tucana–Horologium Association". The Astrophysical Journal. 880 (1): L17. arXiv:1906.10703. doi:10.3847/2041-8213/ab2988. ISSN 2041-8213.
  15. ^ "AO-1 Programmes - CHEOPS Guest Observers Programme - Cosmos". Retrieved 2019-11-15.

External links[edit]