Ariel goes from design to reality

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

Ariel, the infrared detection mission of large exoplanets with atmospheric remote sensing, addresses one of the key themes of ESA’s Cosmic Vision program: 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, examining a diverse sample of about 1000 planetary atmospheres simultaneously in the visible and infrared wavelengths.

It is the first mission dedicated to measuring the chemical composition and thermal structures of exoplanets, connecting them to the environment of the host star. This will fill a significant gap in our knowledge of how the planet’s chemistry relates to the environment in which it formed, or whether the type of host star drives the physics and chemistry of the planet’s evolution.

Observations of these worlds will provide insight into the early stages of planetary and atmospheric formation and their subsequent evolution, while also helping us understand how our Solar System fits into the larger picture of the overall cosmos.

Ariel was selected in 2018 as the fourth middle-class science mission in ESA’s Cosmic Vision plan. It was adopted by ESA at the Agency’s Scientific Program Committee meeting on 12 November, paving the way for construction.

“Ariel will enable planetary science far beyond the confines of our solar system,” says Günther Hasinger, ESA’s Director of Science. “The adoption of Ariel strengthens ESA’s commitment to exoplanet research and will ensure European astronomers are at the forefront of this revolutionary field for the next decade and well beyond.”

Ariel will be ESA’s third dedicated exoplanet mission to launch within a ten-year period, with each mission addressing a unique aspect of exoplanet science. Cheops, the signature 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 2026 to find and study extrasolar planetary systems, with special emphasis on rocky planets around Sun-like stars in the habitable zone, the distance to a star where liquid is water can exist on the surface of a planet. Ariel, slated for launch in 2029, will focus on hot and hot planets, ranging from super-Earths to gas giants orbiting near their parent stars, using their well-blended atmospheres to decipher their mass composition.

In the coming months, the industry will be asked to bid on the supply of spacecraft hardware for Ariel. Around the summer of next year, the main industrial contractor will be selected to build it.

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

“After an intense period of work on preliminary design concepts and consolidating the technologies needed to demonstrate the viability of the mission, we are ready to move Ariel to the implementation phase,” says Ludovic Puig, head of ESA’s Ariel study.

The telescope’s spectrometers will measure a planet’s chemical footprints as it passes in front of – transits – its host star, or passes behind it – an occultation. The measurements will also allow astronomers to observe the planet’s darkening of the host star with an accuracy of 10-100 parts per million relative to the star.

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

“With Ariel, we will take the characterization of exoplanets to the next level by studying these distant worlds both as individuals and, importantly, as populations, in much more detail than ever,” says Göran Pilbratt, ESA scientist Ariel.

“Our chemical census of hundreds of solar systems will help us understand each planet in the context of the chemical environment and host star composition, in turn helping us better understand our cosmic neighborhood,” adds Theresa Lueftinger, Ariel project scientist. of ESA.

“We are delighted to enter the implementation phase of the Ariel mission,” says Jean-Christophe Salvignol, ESA’s Ariel project manager. “We are moving towards the optimal spacecraft design to answer fundamental questions about our place in the cosmos.”

Ariel is expected to be launched on ESA’s new Ariane 6 rocket from the European spaceport of Kourou in French Guiana. It will operate from an orbit around the second Sun-Earth Lagrange point, L2, 1.5 million kilometers directly behind the Earth as seen from the Sun, on an initial four-year mission. The ESA-led Comet Interceptor mission will share the journey into space.

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