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Short description: Space telescope
NamesAtmospheric Remote-sensing Infrared Exoplanet Large-survey
Mission typeSpace telescope
Mission duration4 years (planned) [1]
Spacecraft properties
Launch mass1,300 kg (2,900 lb) [2]
Dry mass1,000 kg (2,200 lb)
Payload mass300 kg (660 lb)
Start of mission
Launch date2029 (planned) [3]
RocketAriane 62
Launch siteCentre Spatial Guyanais, Kourou, ELA-4
Orbital parameters
Reference systemSun–Earth L2 orbit[4]
Main Cassegrain reflector
Diameter1.1 m × 0.7 m (3 ft 7 in × 2 ft 4 in)
Focal lengthf/13.4
Collecting area0.64 m2
Wavelengthsvisible and near-infrared
Telescope assembly (TA)
Ariel infrared spectrometer (AIRS)
Fine Guidance System (FGS)
A grey opaque circle with the word "ARIEL" written in white across the circle's bottom half. A series of concentric circles close in on the black-colored dot in the "I", with the last circle colored yellow, representing an exoplanet transiting in front of a star.
ARIEL mission insignia
Cosmic Vision

The Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) is a space telescope and the fourth medium-class mission of the European Space Agency's Cosmic Vision programme. The mission is aimed at observing at least 1000 known exoplanets using the transit method, studying and characterising the planets' chemical composition and thermal structures. Compared to the James Webb Space Telescope, ARIEL will have more observing time available for planet characterisation but a much smaller telescope and it will be launched almost a decade later. ARIEL is expected to be launched in 2029 aboard an Arianespace Ariane 6 together with the Comet Interceptor.


ARIEL will observe 1000 planets orbiting distant stars and make the first large-scale survey of the chemistry of exoplanet atmospheres.[5] The objective is to answer fundamental questions about how planetary systems form and evolve.[6] A spectrometer will spread the light into a spectrum ("rainbow") and determine the chemical fingerprints of gases in the planets' atmospheres.[6] This will enable scientists to understand how the chemistry of a planet links to the environment in which it forms, and how its formation and evolution are affected by its parent star.[6] ARIEL will study a diverse population of exoplanets in a wide variety of environments, but it will focus on warm and hot planets in orbits close to their star.[6]

The ARIEL mission is being developed by a consortium of various institutions from eleven member states of the European Space Agency (ESA),[lower-alpha 1] and international contributors from four countries.[lower-alpha 2] The project is led by principal investigator Giovanna Tinetti of the University College London,[8][9] who had previously led the unsuccessful Exoplanet Characterisation Observatory (EcHO) proposal for the M3 Cosmic Vision launch slot.[10][11] Operations of the mission and the spacecraft will be handled jointly by ESA and the consortium behind the mission's development, through a coordinated Instrument Operations and Science Data Centre (IOSDC).[7] A Mission Operations Centre (MOC) will be set up at the European Space Operations Centre (ESOC) in Darmstadt, Germany, while a concurrent ARIEL Science Operations Centre (SOC) will be set up at the European Space Astronomy Centre (ESAC) near Madrid, Spain.[7] The MOC will be responsible for the spacecraft itself, while the SOC will be responsible for archiving mission data and scientific data downlinked from the spacecraft. The IOSDC will help develop results from the mission based on data received by the SOC.[7]

In August 2017, NASA conditionally selected Contribution to ARIEL Spectroscopy of Exoplanets (CASE) as a Partner Mission of Opportunity, pending the result of ESA's Cosmic Vision selection.[12] Under the proposal NASA provides two fine guidance sensors for the ARIEL spacecraft in return for the participation of U.S. scientists in the mission.[13] CASE was officially selected in November 2019, with JPL astrophysicist Mark Swain as principal investigator.[14]

On December 7, 2021, ESA announced that the €200 million contract to build ARIEL had been awarded to Airbus Defence and Space.[15]


The design of the ARIEL spacecraft is based on that intended for the Exoplanet Characterisation Observatory (EChO) mission, and has heritage from the thermal design of Planck.[7][16] The body of the spacecraft is split into two distinct modules known as the Service Module (SVM) and the Payload Module (PLM). The SVM is shaped as a 'sandwich' structure, consisting of three aluminium V-Grooves and three pairs of low conductivity fibreglass bipod struts supporting the PLM.[16] A basic horizontal telescope configuration is used for the PLM itself, housing all of the spacecraft's scientific instruments and its oval 1.1 m × 0.7 m (3 ft 7 in × 2 ft 4 in) primary mirror.[16][17] At launch, the spacecraft will have a fuelled mass of 1,300 kg (2,900 lb), and will have a dry mass of 1,000 kg (2,200 lb).[17] The PLM will account for around 300 kg (660 lb) of that mass.[17]


The ARIEL telescope's assembly is an off-axis Cassegrain telescope followed by a third parabolic mirror to recollimate the beam. The telescope uses an oval 1.1 m × 0.7 m (3 ft 7 in × 2 ft 4 in) primary mirror; the imaging quality of the system is limited by diffraction for wavelengths longer than about 3 µm, and its focal ratio (f) is 13.4.[18] The system will acquire images in the visible and near-infrared spectrum.[18] To operate its infrared spectroscope between 1.95 µm and 7.8 µm, the telescope will be passively cooled to a temperature of 55 K (−218.2 °C; −360.7 °F).[7][18]

Launch and trajectory

The ARIEL spacecraft is expected to be launched in 2029 by Arianespace's Ariane 62 launch vehicle (currently in development[19][20]) together with the Comet Interceptor.[15][3][21][22] It will be launched from the Centre Spatial Guyanais (CSG) in Kourou, French Guiana,[21][22] from the "Ensemble de lancement Ariane" ELA-4 (Ariane Launch Area-4) being purpose-built for future Ariane 6 launches.[23] ARIEL will be launched to the L2 Lagrange point, in a position located at a distance of 1,500,000 km (930,000 mi) from Earth,[21] where it will encounter a very stable thermal environment that is required to detect exoplanets.[22]

See also


  1. These are the University of Vienna from Austria, the Universities of Leuven and Liège from Belgium, the Technical University of Denmark, the CEA, CNES, Paris Institute of Astrophysics, Marseille, Côte d'Azur, and Paris Observatories in France , the Max Planck Society and University of Hamburg in Germany , SRON and the Universities of Amsterdam, Delft, and Leiden in the Netherlands, the Space Research Centre of Polish Academy of Sciences, the CAB, Institute of Space Sciences and the Institute of Astrophysics of the Canary Islands in Spain , University of Bern in Switzerland , and the ATC and the Universities of Cardiff, Exeter, Hertfordshire, Keele, Leicester, London, and Oxford in the United Kingdom .[7]
  2. These are the Université de Montréal and the University of Toronto in Canada , the ELSI, Tokyo Institute of Technology, and Osaka University in Japan , the National Autonomous University of Mexico, and Caltech, the Lunar and Planetary Laboratory (LPL) and Jet Propulsion Laboratory (JPL), Lunar and Planetary Institute, and Universities of Arizona State, Chicago, and Princeton in the United States .[7]


  1. "ARIEL Summary". ESA. 11 November 2020. 
  2. "ARIEL Spacecraft". ESA. 11 November 2020. 
  3. 3.0 3.1 "Ariel moves from blueprint to reality". ESA. 12 November 2020. 
  4. "Ariel Space Mission – European Space Agency M4 Mission" (in en-US). 
  5. "A Candidate for the ESA M4 Mission". Ariel Space Mission. 21 April 2019. 
  6. 6.0 6.1 6.2 6.3 "ARIEL exoplanet mission selected as ESA's next medium-class science mission". Ariel Space Mission. 20 March 2018. 
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 "(ESA/SCI(2017)2) ARIEL – Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey -- Enabling Planetary Science across Light‐years". ARIEL Science Mission. March 2017. 
  8. Amos, Jonathan (20 March 2018). "Discovering the nature of planets". BBC News. 
  9. Gibney, Elizabeth (20 March 2018). "First space mission dedicated to exoplanet atmospheres gets green light". Nature (journal). 
  10. Gewin, Virginia (14 April 2011). "Turning point: Giovanna Tinetti". Nature (journal) (Nature (journal)) 472 (7342): 251. doi:10.1038/nj7342-251a. ISSN 1476-4687. 
  11. European Space Agency (21 February 2014). "ESA selects planet-hunting PLATO mission". Astronomy (magazine). 
  12. "NASA Selects Proposals to Study Galaxies, Stars, Planets". Jet Propulsion Laboratory. NASA.  This article incorporates text from this source, which is in the public domain.
  13. "FINESSE and ARIEL + CASE: Dedicated Transit Spectroscopy Missions for the Post-TESS Era". Cosmic Origins Program Analysis Group (COPAG). NASA.  This article incorporates text from this source, which is in the public domain.
  14. Landau, Elizabeth (8 November 2019). "NASA Instrument to Probe Planet Clouds on European Mission". NASA.  This article incorporates text from this source, which is in the public domain.
  15. 15.0 15.1 "ESA award €200m contract to Airbus to build Ariel observatory". European Spaceflight. 
  16. 16.0 16.1 16.2 "ARIEL: Spacecraft". European Space Agency. 20 March 2018. 
  17. 17.0 17.1 17.2 "Facts & Figures". ARIEL Space Mission. May 2017. 
  18. 18.0 18.1 18.2 ARIEL - Payload ESA, 20 March 2018
  19. Amos, Jonathan (22 June 2017). "Full thrust on Europe's new Ariane 6 rocket". BBC News. 
  20. Pultarova, Tereza (25 October 2017). "ArianeGroup CFO Pierre Godart on Ariane 6 cost savings, micro launchers and reusability". SpaceNews. 
  21. 21.0 21.1 21.2 "ESA's next science mission to focus on nature of exoplanets". European Space Agency. 20 March 2018. 
  22. 22.0 22.1 22.2 Warren, Melissa (20 March 2018). "UK part of ARIEL exoplanet project selected as ESA's next medium-class science mission". Science and Technology Facilities Council. 
  23. "Race to build Ariane 6 rocket launch pad". Euronews. 14 December 2017. 

External links

  • ARIEL official website
  • ARIEL at the European Space Agency