ESA’s Exoplanet The Ariel mission, which is scheduled to start in 2029, has moved from the study phase to the implementation phase. An industrial contractor is then selected to build the spacecraft.
It is the first mission dedicated to measuring the chemical composition and thermal structures of exoplanets and 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 is related to the environment in which it formed, or whether the nature of the host star drives the physics and chemistry of the planet’s evolution.
Observations of these worlds give insights into the early stages of planetary and atmospheric formation and their subsequent development and help us to understand how our own solar system fits into the overall picture of the entire cosmos.
Ariel was selected as the fourth medium-sized science mission in ESA’s Cosmic Vision plan in 2018. It was “approved” by ESA during the Agency’s Science Programs Committee meeting on November 12th, paving the way for construction.
“Ariel will enable planetary research far beyond the boundaries of our own solar system,” says Günther Hasinger, ESA’s Director of Science. “Ariel’s adoption confirms 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 exoplanet mission launched in ten years. Each mission deals with 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 a focus on rocky planets around sun-like stars in the habitable zone – the distance from a star in which liquid is present Water can exist on the surface of a planet. Ariel, slated to launch in 2029, will focus on warm and hot planets ranging from super-earths to gas giants orbiting near their parent stars, using their well-mixed atmosphere to decipher their mass composition.
In the coming months, industry will be invited to bid to supply spacecraft hardware for Ariel. The main contractor will be selected for the construction around the summer of next year.
The mission’s payload module, which includes a 1-meter-class cryotelescope and associated scientific 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.
“After working hard on preliminary design concepts and consolidating the technology required to demonstrate the feasibility of the mission, we are ready to move Ariel into the implementation phase,” said Ludiel Puig, Ariel studies manager at ESA.
The telescope’s spectrometers measure the chemical fingerprints of a planet when it crosses in front of – “transits” – its host star or passes behind it – an “occultation”. The measurements will also enable astronomers to observe the planet’s eclipse of the host star with an accuracy of 10 to 100 ppm from the star.
Ariel will be able to detect signs of known constituents in the planet’s atmosphere such as water vapor, carbon dioxide and methane. More exotic metal compounds are also being detected in order to decipher the entire chemical environment of the distant solar system. For a select number of planets, Ariel will also conduct a thorough 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 examining these distant worlds both as individuals and, more importantly, as populations, in greater detail than ever before,” said Göran Pilbratt, Ariel study scientist at ESA.
“Our chemical enumeration of hundreds of solar systems will help us understand each planet in the context of the host star’s chemical environment and composition, and better understand our own cosmic neighborhood,” added Ariel project scientist Theresa Lueftinger from ESA.
“We are excited to enter the implementation phase of the Ariel mission,” says ESA Ariel Project Manager Jean-Christophe Salvignol. “We are moving towards optimal spacecraft design to answer fundamental questions about our place in the cosmos.”
Ariel is 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 the second Sun-Earth Lagrange point L2, 1.5 million kilometers directly behind the Earth, as seen from the Sun, on a first four-year mission. The Comet Interceptor mission, led by ESA, will share the journey into space.