Ariel Exoplanet mission goes from plan to reality

A hot planet passes in front of its mother star in this artist’s impression of a system of exoplanets. Credit: ESA / ATG medialab

Ariel, the great mission to explore infrared exoplanets by atmospheric remote sensing, addresses one of the key themes of ESA’s Cosmic Vision program: what are the conditions for the formation of planets and the emergence of life? Ariel will study what exoplanets are made of, how they were formed and how they evolve, simultaneously examining a diverse sample of about 1,000 planetary atmospheres in visible and infrared wavelengths.

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

Observations of these worlds will provide insight into the early stages of planetary and atmospheric formation, and their subsequent evolution, which will also help us understand how our own solar system fits into the larger picture of the global 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 November 12, paving the way for construction.

“Ariel will enable planetary science far beyond the limits of our own solar system,” says Günther Hasinger, ESA Scientific Director. “The adoption of Ariel confirms ESA’s commitment to exoplanet research and will ensure that European astronomers will be 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 ten years, with each mission addressing a unique aspect of exoplanet science. Cheops, ExOPlanet’s signature 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 period 2026 to find and study extrasolar planetary systems, with particular emphasis on rocky planets around Sun-like stars in the habitable zone – the distance of one star where liquid water can exist on the surface of a planet. Ariel, slated to launch in 2029, will focus on hot and hot planets, ranging from super-Earths to gas giants orbiting near their parent stars, taking advantage of their well-mixed atmospheres to decipher their loose composition.

In the coming months, industry will be asked to make offers to supply space hardware to Ariel. Around the summer of next year, the industrial contractor will be selected to build it.

The mission payload module, which includes a one-meter 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 intensive period of working on preliminary design concepts and consolidating the technologies required to demonstrate the feasibility of the mission, we are ready to move Ariel forward into the implementation phase,” says Ludovic Puig, Head of ESA’s Ariel study.

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 – an “occultation”. The measurements will also allow astronomers to observe the gradation of the host star by the planet with an accuracy of 10 to 100 parts per million relative to the star.

Ariel will be able to detect signs of well-known ingredients in the atmosphere of 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 remote solar system. For a number of planets, Ariel will also conduct an in-depth study 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, most importantly, as populations, in much more detail than ever before,” says Göran. Pilbratt, scientist in ESA’s Ariel study.

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

“We are happy to enter the implementation phase of the Ariel mission,” says Jean-Christophe Salvignol, ESA Ariel project manager. “We are moving towards the optimal design of spacecraft 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 in Kourou, French Guiana. It will operate from an orbit around Lagrange’s second Sun-Earth point, L2, 1.5 million kilometers directly “behind” Earth as seen from the Sun, for an initial four-year mission. The ESA-led Comet Interceptor mission will share the journey through space.