Mission type | Exoplanetology, astrophysics |
---|---|
Operator | Swiss Space Office / ESA |
COSPAR ID | 2019-092B |
SATCAT no. | 44874 |
Website | cheops sci |
Mission duration | 3.5 years (nominal) + 3 years (extended) [1] Elapsed: 4 years and 7 months (in progress) |
Spacecraft properties | |
Spacecraft type | Space observatory |
Bus | SEOSAT [2] |
Manufacturer | Airbus Defence and Space (Spain) |
Launch mass | 273 kg [3] |
Payload mass | 58 kg [4] |
Dimensions | 1.5 × 1.5 × 1.5 m (4 ft 11 in × 4 ft 11 in × 4 ft 11 in) |
Power | 64 watts [5] |
Start of mission | |
Launch date | 18 December 2019, 08:54:20 UTC [6] |
Rocket | Soyuz-ST-A/Fregat-M (Soyuz VS23) [7] [8] |
Launch site | Centre Spatial Guyanais, ELS |
Contractor | Arianespace |
Orbital parameters | |
Reference system | Geocentric orbit [9] |
Regime | Sun-synchronous orbit |
Perigee altitude | 712 km (442 mi) |
Apogee altitude | 715 km (444 mi) |
Inclination | 92.80° |
Period | 90.00 minutes |
Main telescope | |
Type | Ritchey–Chrétien frame-transfer back-side illuminated CCD |
Diameter | 32 cm [10] |
Focal ratio | f/8 |
Wavelengths | 330 to 1100 nm |
Transponders | |
Capacity | 1.2 Gbit/day downlink [11] |
Instruments | |
Photometer [12] | |
CHEOPS mission patch |
CHEOPS (CHaracterising ExOPlanets Satellite) is a European space telescope. Its objective is 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. [13]
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 altitude.
Thousands of exoplanets have been discovered by the end of the 2010s; [14] 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. [15]
For the planned mission duration of 3.5 years, CHEOPS is to measure the size of known transiting exoplanets orbiting bright and nearby stars, [16] as well as search for predicted transits of exoplanets previously discovered via radial velocity. Scientists behind the project expect these well-characterised transiting exoplanets to be prime targets for observatories such as James Webb Space Telescope (JWST) or the extremely large telescopes. [17]
In 2023, the mission was extended to 2026. During the extended mission CHEOPS is expected to also search for exomoons. [1]
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. [16] 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. [7] [18] The ESA mission cost is capped at €50 million. [7] Media Lario S.r.l. (Italy) was responsible for the optical finishing of the primary optical element. [19]
CHEOPS launched on board of a Soyuz-STA launch vehicle on 18 December 2019, at 08:54:20 UTC from Centre Spatial Guyanais (CSG) in Kourou, French Guiana. [6] [20] CHEOPS separated after two hours and 23 minutes from lift-off. [21] The primary payload was the first satellite of ASI's COSMO-SkyMed Second Generation constellation, CSG 1. The launcher also deployed three CubeSats, including ESA's OPS-SAT. [13] CHEOPS went into a 712 km (442 mi) altitude Sun-synchronous polar orbit.
After the cover of the telescope was opened on 29 January 2020, [22] CHEOPS took its first light image on 7 February 2020. The image is centred on the star HD 70843, a yellow-white star located around 150 light years away. The star was selected because of its brightness and position on the sky. The stars in the image are blurry, which is intended. The defocused mirror distributes the light of the star over many pixels of the detector, making the measurements of starlight more precise. [23] The first light images were better than it was expected from tests in the laboratory. The images were smoother and more symmetrical, which could reduce noise caused by the detector and the spacecraft. [24]
In April 2020, the telescope began science operations. [25]
The satellite has dimensions of approximately 1.5 × 1.5 × 1.5 m (4 ft 11 in × 4 ft 11 in × 4 ft 11 in) and a hexagonal base structure. The satellite bus of the CHEOPS spacecraft is based on the SEOSAT platform. [11]
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. [11]
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. [11] [26]
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 Charge-coupled device (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), 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. [27] The University of Geneva and the University of Bern provided the powerful photometer. [12] Target star images are deliberately defocussed to help accurate photometry. [23]
Two titanium plaques with thousands of miniaturised drawings by children have been fixed to CHEOPS. Each plaque measures nearly 18 × 24 cm (7.1 × 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. [28] The individual drawings can be found at the website of CHEOPS by clicking on a map of Europe. [29]
The main goal of CHEOPS is the accurate measurement of 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 is 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). [7]
CHEOPS measures 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[ further explanation needed ].
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. [30]
The spacecraft is powered by solar panels that are also part of its sunshield. They provide 60 W continuous power for instrument operations and allow for at least a 1.2 gigabit/day data downlink capacity. [11] Data-taking started in early 2020. [31]
Eighty per cent 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). [32] 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. [33]
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. [34] The approved AO-1 projects include observations of the hot jupiters HD 17156 b, Kelt-22A b, [35] warm jupiter K2-139b, [36] multi systems GJ 9827, K2-138, the exoplanet DS Tuc Ab, [37] 55 Cancri e (likely GTO), [38] [39] WASP-189 b [40] 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. [41]
HD 108236 f was discovered with CHEOPS. [42]
A study of WASP-189b (a 'hot Jupiter') has been published. [43]
TOI-178 has been found to have 6 planets, 5 having orbital resonances. [44] Planetary densities have been calculated.
CHEOPS, supplemented by TESS data, characterized AU Mic and its planet b. It also confirmed transit-timing variations, caused by the outer planets. [45]
TOI-561 is a multi-planet system that was studied with CHEOPS, HARPS-N and TESS. The study confirmed that TOI-561 b is the lowest density ultra-short period planet. [46]
CHEOPS observed occultations caused by the planet 55 Cancri e and was able to observe individual occultations for the first time. [47]
A study searching for transits around 6 white dwarfs did not detect any transits [48] and a study to search for exomoons around v2 Lupi d was unable to detect any additional transits. The full transit of v2 Lupi d was observed for the first time with CHEOPS, potentially aiding any future searches for exomoons around this planet. [49]
CHEOPS also sees trails from other satellites during its observations, since it is in low Earth orbit. [50]
CoRoT was a space telescope mission which operated from 2006 to 2013. The mission's two objectives were to search for extrasolar planets with short orbital periods, particularly those of large terrestrial size, and to perform asteroseismology by measuring solar-like oscillations in stars. The mission was led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners.
Gaia is a space observatory of the European Space Agency (ESA), launched in 2013 and expected to operate until 2025. The spacecraft is designed for astrometry: measuring the positions, distances and motions of stars with unprecedented precision, and the positions of exoplanets by measuring attributes about the stars they orbit such as their apparent magnitude and color. The mission aims to construct by far the largest and most precise 3D space catalog ever made, totalling approximately 1 billion astronomical objects, mainly stars, but also planets, comets, asteroids and quasars, among others.
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported as of January 2024 have been observed directly, with even fewer being resolved from their host star.
Transiting Exoplanet Survey Satellite (TESS) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission. It was launched on 18 April 2018, atop a Falcon 9 launch vehicle and was placed into a highly elliptical 13.70-day orbit around the Earth. The first light image from TESS was taken on 7 August 2018, and released publicly on 17 September 2018.
CoRoT-1 is a yellow dwarf main sequence star similar to the Sun. The star is located approximately 2,510 light-years away in the constellation of Monoceros. The apparent magnitude of this star is 13.6, which means it is not visible to the naked eye; however, it can be seen through a medium-sized amateur telescope on a clear, dark night. The first exoplanet discovered in the course of the CoRoT mission orbits this star; it is considered to be a "hot Jupiter", and is approximately as massive as the planet Jupiter itself.
CoRoT-7 is a binary star system made up of a late G-type star and a M-dwarf star that was discovered in 2021. The primary star has three exoplanets, including CoRoT-7b, an super-Earth exoplanet that is remarkable due to its extremely high temperature and very short orbital period, around 20 hours. It was the first exoplanet shown to be rocky. The system has the name CoRoT-7 after the CoRoT space telescope, which discovered the exoplanets around the star CoRoT-7A. The stellar system is 520 light-years from the Earth.
CoRoT-5 is a magnitude 14 star located in the Monoceros constellation.
PLAnetary Transits and Oscillations of stars (PLATO) is a space telescope under development by the European Space Agency for launch in 2026. The mission goals are to search for planetary transits across up to one million stars, and to discover and characterize rocky extrasolar planets around yellow dwarf stars, subgiant stars, and red dwarf stars. The emphasis of the mission is on Earth-like planets in the habitable zone around Sun-like stars where water can exist in a liquid state. It is the third medium-class mission in ESA's Cosmic Vision programme and is named after the influential Greek philosopher Plato. A secondary objective of the mission is to study stellar oscillations or seismic activity in stars to measure stellar masses and evolution and enable the precise characterization of the planet host star, including its age.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 1 July 2024, there are 6,660 confirmed exoplanets in 4,868 planetary systems, with 995 systems having more than one planet. This is a list of the most notable discoveries.
K2-138b is a potentially rocky Super-Earth exoplanet orbiting every 2 days around a K1V star. The planet, along with the four others in the system, was found by citizen scientists of the Exoplanet Explorers project on Zooniverse. It was the final planet found in the system and was officially announced on January 8, 2018.
K2-138, also designated EPIC 245950175 or EE-1, is a large early K-type main sequence star with a system of at least 6 planets discovered by citizen scientists. Four were found in the first two days of the Exoplanet Explorers project on Zooniverse in early April 2017, while two more were revealed in further analysis. The system is about 660 light-years away in the constellation Aquarius, within K2 Campaign 12.
CoRoT-8b is a transiting exoplanet orbiting the K-type main sequence star CoRoT-8 1,050 light years away in the equatorial constellation Aquila. The planet was discovered in April 2010 by the CoRoT telescope.
DS Tucanae is a binary star system 144 light years away in the constellation of Tucana. It has an apparent visual magnitude of 8.5, and is a RS Canum Venaticorum variable. The system is notable for being young as a member of the 45 Myr old Tucana-Horologium moving group and for the primary star hosting the confirmed exoplanet DS Tucanae Ab, discovered by THYME, using TESS.
Katherine Gudrun Isaak is a British astrophysicist and the Project Scientist for the European Space Agency Characterising Exoplanet Satellite mission (CHEOPS). She is based at European Space Research and Technology Centre.
L 98-59 is a bright M dwarf star, located in the constellation of Volans, at a distance of 10.608 parsecs, as measured by the Gaia spacecraft.
LTT 9779 is a G-type main-sequence star located 264 light-years away from the Solar System in the constellation of Sculptor. The star is about 95% the radius and about the same mass as the Sun, but younger than the Sun at 1.7 billion years old, hence its lower luminosity. It has a temperature of 5,443 K and a rotation period of 45 days. LTT 9779 is orbited by one known exoplanet.