Ariel goes from the plane to reality

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

Ariel, the atmospheric remote sensing infrared large exoplanet survey mission, 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, by studying a diverse sample of around 1,000 planetary atmospheres simultaneously at visible and infrared wavelengths.

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

Observations of these worlds will give insight into the early stages of planetary and atmospheric formation, and their subsequent evolution, also helping us in the process to understand how our own Solar System fits into the larger picture of the cosmos in general.

Ariel was selected in 2018 as the fourth middle-class science mission in ESA’s Cosmic Vision plan. It was adopted by ESA during 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’s science director. “The adoption of Ariel consolidates ESA’s commitment to exoplanet research and will ensure that European astronomers are at the forefront of this revolutionary field for the next decade and beyond.”

Ariel will be ESA’s third dedicated exoplanet mission to launch in a ten-year period, and each mission will address a unique aspect of exoplanet science. Cheops, ExOPlanet’s signature satellite, launched in December 2019, is already producing world-class science. Plato’s mission PLAnetary Transits and Oscillations of the Stars, 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 from a star where there is liquid. water can exist on the surface of a planet. Ariel, scheduled to launch in 2029, will focus on hot and warm planets, ranging from super-earths to gas giants that orbit close to their parent stars, taking advantage of their well-mixed atmospheres to decipher their bulk composition.

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

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

“After an intensive period of work on preliminary design concepts and on consolidating the technologies necessary to demonstrate mission feasibility, we are ready to take Ariel to the implementation stage,” says Ariel’s studio director. from ESA, Ludovic Puig.

The telescope’s spectrometers will measure the chemical footprints of a planet 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 dimming of the host star 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 planets’ atmosphere, such as water vapor, carbon dioxide, and methane. It will also detect more exotic metallic compounds to decipher the general chemical environment of the distant solar system. For a select 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 exoplanet characterization to the next level by studying these distant worlds as individuals and, more importantly, as populations, in much more detail than ever before,” says ESA’s Ariel study scientist Göran Pilbratt.

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

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

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