Artist's impression of the CHEOPS space observatory
|Mission type||Exoplanetology, astrophysics|
|Operator||Swiss Space Office|
|Mission duration||Planned: 3.5 years|
Elapsed: 1 month and 4 days
|Spacecraft type||Space observatory|
|Manufacturer||Airbus Defence and Space|
|Launch mass||≈300 kg (660 lb)|
|Payload mass||58 kg (128 lb)|
|Dimensions||1.5 m × 1.5 m × 1.5 m (4 ft 11 in × 4 ft 11 in × 4 ft 11 in)|
|Start of mission|
|Launch date||18 December 2019 at 9:54 CET (08:54 GMT)|
|Launch site||Guiana Space Centre|
(Ensemble de Lancement Soyouz)
|Regime||Sun-synchronous 6 am/pm|
|Perigee altitude||700 km (430 mi)|
|Apogee altitude||700 km (430 mi)|
frame-transfer back-side illuminated CCD
|Diameter||32 cm (13 in)|
|Wavelengths||330 to 1100 nm|
|Capacity||1.2 GBit/day downlink|
CHEOPS (CHaracterising ExOPlanets Satellite) is a European space telescope to determine the size of known extrasolar planets, which will allow the estimation of their mass, density, composition and their formation. Launched on 18 December 2019, it is the first Small-class mission in ESA's Cosmic Vision science programme.
The small satellite features an optical Ritchey–Chrétien telescope with an aperture of 30 cm, mounted on a standard small satellite platform. It was placed into a Sun-synchronous orbit of about 700 km (430 mi) altitude.
Thousands of exoplanets have been discovered by the end of the 2010s; some have minimum mass measurements from the radial velocity method while others that are seen to transit their parent stars have measures of their physical size. Few exoplanets to date have highly accurate measures for both mass and radius, limiting the ability to study the variety in bulk density that would provide clues as to what materials they are made of and their formation history. For the planned mission duration of 3.5 years, CHEOPS is to measure the size of known transiting exoplanets orbiting bright and nearby stars as well as search for transits of exoplanets previously discovered via radial velocity. Scientists behind the project expect these well-characterised transiting exoplanets to be prime targets for future observatories such as JWST or the extremely large telescopes.
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. 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 at the University of Bern and the Principal Scientist from ESA is Kate Isaak. After a competition phase, Airbus Defence and Space in Spain was selected as the spacecraft builder. The ESA mission cost is capped at €50 million. Media Lario S.r.l. (Italy) was responsible for the optical finishing of the primary optical element.
A sunshield mounted on the platform protects the radiator and detector housing against the Sun, and it also features solar panels for the electrical power subsystem. The sunshield wraps around the hexagonal bus.
Attitude and orbit control system (AOCS)
The control system is 3-axis stabilized, but nadir locked, ensuring that one of the spacecraft axes is always pointing towards the Earth. During each orbit, the spacecraft will slowly rotate around the telescope line-of-sight to keep the focal plane radiator oriented towards cold space, enabling passive cooling of the detector. The typical observation duration will be 48 hours. During a typical 48-hour observation CHEOPS will have a pointing stability of better than eight arcsec at 95% confidence.
CHEOPS Instrument System (CIS)
The detector, support electronics, telescope, back-end optics, instrument computer and thermal regulation hardware are known collectively as the CHEOPS Instrument System (CIS). The required photometric precision will be achieved using a single frame-transfer, back-illuminated CCD detector from Teledyne e2v with 1024 × 1024 pixels and a pixel pitch of 13 µm. The CCD is mounted in the focal plane of the telescope, and will be passively cooled to 233 K (−40 °C; −40 °F), with a thermal stability of 10 mK. The telescope is a single medium-size f/8, on-axis Ritchey–Chrétien telescope with a 32 cm (13 in) aperture, mounted on a stiff optical bench. The University of Geneva and the University of Bern provided the powerful photometer.
Two titanium plaques with thousands of miniaturised drawings by children have been fixed to CHEOPS. Each plaque measures nearly 18 cm × 24 cm (7.1 in × 9.4 in). The plaques, prepared by a team at the Bern University of Applied Sciences were unveiled in a dedicated ceremony at RUAG on 27 August 2018. The individual drawings can be found at the website of CHEOPS by clicking on a map of Europe.
The main goal of CHEOPS will be to accurately measure the size (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).
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 different science objectives require 500 separate target pointings. Assuming 1 hour per pointing the mission duration is estimated at 1175 days or 3.2 years. Together with the 20% of open time available for the community the total duration of the CHEOPS mission is estimated to be 3.5 years.
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. The first data is expected at the beginning of 2020.
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). 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.
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. The approved AO-1 projects include observations of the hot jupiters HD 17156 b, Kelt-22A b, warm jupiter K2-139b, multi systems GJ 9827, K2-138, the exoplanet DS Tuc Ab, 55 Cancri e (likely GTO), 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.
CHEOPS launched on board of a Soyuz-Fregat rocket on December 18, 2019 at 9:54 CET from Guiana Space Centre in Kourou, French Guiana. The primary payload was the first satellite of ASI's Cosmo-SkyMed Second Generation constellation. The launcher also deployed three CubeSats, including ESA's OPS-SAT.
- List of exoplanet search projects
- CoRoT – A European space telescope that operated between 2006 - 2014
- Kepler space telescope – Tenth mission of the Discovery program; optical space telescope for exoplanetology
- MOST – Canada's first space telescope
- PLATO – Third medium mission of Cosmic Vision; multi-mirror optical telescope for finding and studying exoplanets
- Transiting Exoplanet Survey Satellite (TESS) – NASA space telescope designed to search for exoplanets
- List of proposed space observatories
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- The CHEOPS Payload: a single Telescope. CHEOPS Home Page. Accessed on December 18 2019.
- CHEOPS - Executive Summary
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|Library resources about |
- CHEOPS ESA homepage
- CHEOPS homepage includes orbital tracking of the CHEOPS spacecraft
- Europe to begin search for habitable planets in our cosmic backyard, 22 October 2012, Stuart Clark, The Guardian
- CHEOPS mission visualization - video