ESA Ariel Space Telescope Will Survey Atmospheres of 1000 Exoplanets Starting in 2029

ESA Ariel Space Telescope Will Survey Atmospheres of 1000 Exoplanets Starting in 2029

Brian Wang |
November 14, 2020 |

ESA’s exoplanet mission Ariel, scheduled for launch in 2029, has moved from study to implementation phase, following which an industrial contractor will be selected to build the spacecraft.

Ariel, the Atmospheric remote-sensing infrared exoplanet large-survey mission, addresses one of the key themes of ESA’s Cosmic Vision programme: What are the conditions for planet formation and the emergence of life? Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of around 1000 planetary atmospheres simultaneously in visible and infrared wavelengths.

Ariel will be ESA’s third dedicated exoplanet mission to launch within a ten-year period, with each mission tackling a unique aspect of exoplanet science. Cheops, the CHaracterising ExOPlanet Satellite, launched in December 2019, is already producing world-class science. Plato, the PLAnetary Transits and Oscillations of stars mission, will be launched in the 2026 timeframe to find and study extrasolar planetary systems, with a special emphasis on rocky planets around Sun-like stars in the habitable zone – the distance from a star where liquid water can exist on a planet’s surface. Ariel, planned to launch in 2029, will focus on warm and hot planets, ranging from super-Earths to gas giants orbiting close to their parent stars, taking advantage of their well-mixed atmospheres to decipher their bulk composition.

In the coming months, industry will be asked to make bids to supply spacecraft hardware for Ariel. Around summer next year, the prime industrial contractor will be selected to build it.

The mission’s payload module, which includes a one metre-class cryogenic telescope and associated science instruments, is provided by the Ariel Mission Consortium. The consortium comprises more than 50 institutes from 17 European countries. NASA also contributes to the payload.

The telescope’s spectrometers will measure the chemical fingerprints of a planet as it crosses in front of – ‘transits’ – its host star, or passes behind it – an ‘occultation’. The measurements will also enable astronomers to observe the dimming of the host star by the planet with a precision of 10–100 parts per million relative to the star.

Ariel will be able to detect signs of well-known ingredients in the planets’ atmospheres such as water vapour, carbon dioxide and methane. It will also detect more exotic metallic compounds to decipher the overall chemical environment of the distant solar system. For a select number of planets, Ariel will also perform a deep survey of their cloud systems and study seasonal and daily atmospheric variations.

It will operate from an orbit around the second Sun-Earth Lagrange point, L2, 1.5 million kilometres directly ‘behind’ Earth as viewed from the Sun, on an initial four-year mission.


Written By Brian Wang,

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