ARIEL exoplanet mission selected as ESA’s next medium-class science mission

20th March 2018

Artist's Impression of ARIEL

ARIEL, a mission to answer fundamental questions about how planetary systems form and evolve, has been selected by the European Space Agency (ESA) as its next medium-class science mission, due for launch in 2026. During a 4-year mission, ARIEL will observe 1000 planets orbiting distant stars and make the first large-scale survey of the chemistry of exoplanet atmospheres. ESA’s Science Programme Committee announced the selection of ARIEL from three candidate missions on 20th March 2018. STFC through its RAL Space and UK ATC teams is part of the UK team contributing to this project.

The ARIEL mission has been developed by a consortium of more than 60 institutes from 15 ESA member state countries, including UK, France, Italy, Poland, Spain, the Netherlands, Belgium, Austria, Denmark, Ireland, Hungary, Sweden, Czech Republic, Germany, Portugal, with an additional contribution from NASA in the USA currently under study."UK institutions have provided the leadership and planning for ARIEL, including UCL, STFC RAL Space, STFC UK ATC, Cardiff University and the University of Oxford.

Ian Bryson, Head of Strategic Development at the UK Astronomy Technology Centre said, “It is always exciting to be part of an ESA Science Mission and ARIEL is no exception as it will discover key information about the nature and atmospheric composition of some of the thousands of exoplanets we already know to exist. At the UK ATC we have been working on ARIEL (and the predecessor concept EChO) since 2011 and look forward to getting stuck into the next design phase.”

ARIEL will study a diverse population of exoplanets ranging from Jupiter- and Neptune-size planets down to super-Earths, in a wide variety of environments. While some of the planets may be in the habitable zones of their stars, the main focus of the mission will be on warm and hot planets in orbits close to their star.

Warm and hot exoplanets represent a natural laboratory in which to study the chemistry and formation of planets. High temperatures keep different molecular species circulating throughout the atmosphere and prevent them from sinking or forming cloud layers, where they can become hidden from remote detection. The scorching temperatures experienced by planets close to their stars, which can be at temperatures in excess of 2000 degrees Celsius, also mean that more molecules from the planet’s interior make their way into the atmosphere. This provides ARIEL with better information about the planet’s internal composition and the formation history of the planetary system.

ARIEL’s Principal Investigator, Prof Giovanna Tinetti of UCL said, “Although we’ve now discovered around 3800 planets orbiting other stars, the nature of these exoplanets remains largely mysterious.  ARIEL will study a statistically large sample of exoplanets to give us a truly representative picture of what these planets are like. This will enable us to answer questions about how the chemistry of a planet links to the environment in which it forms, and how its birth and evolution are affected by its parent star.”

ARIEL will have a meter-class telescope primary mirror to collect visible and infrared light from distant star systems. A spectrometer will spread the light into a ‘rainbow’ and extract the chemical fingerprints of gases in the planets’ atmospheres, which become embedded in starlight when a planet passes in front or behind the star. A photometer and guidance system will capture information on the presence on clouds in the atmospheres of the exoplanets and will allow the spacecraft to point to the target star with high stability and precision.

The payload for ARIEL will be amongst the first to be assembled and tested at the STFC RAL Space National Satellite Test Facility, due to be open in mid-2020 following £99 million investment as part of the UK Government’s Industrial Strategy Challenge Fund.

ARIEL will be launched from Kourou in French Guiana and will be placed in orbit around the Lagrange Point 2 (L2), a gravitational balance point 1.5 million kilometres beyond the Earth’s orbit around the Sun. Here, the spacecraft is shielded from the Sun and has a clear view of the whole sky to maximise the possible target exoplanets for observations.

The ARIEL Consortium Project Manager, Paul Eccleston, of STFC RAL Space said “It is wonderful news that ESA have selected ARIEL for the next medium class science mission. The team are very excited to have the opportunity to realise the mission we’ve been developing for the last two years. ARIEL will revolutionise our understanding of how planetary systems form and evolve, helping us put our own solar system into context and compare it to our neighbours in the galaxy.”

Dr Chris Mutlow, Director of STFC RAL Space said, “Congratulations to the whole European consortium for ARIEL. It is great to see strong UK involvement including three STFC departments contributing their expertise and support for the European science community. It is particularly exciting for RAL Space as we will conduct some of the tests in the National Satellite Test Facility, which will be ready in time for this mission.”

ARIEL (Atmospheric Remote-Sensing Infrared Exoplanet Large-survey) Facts and Figures

For further information on ARIEL see:



ARIEL Lagrange Points

Image 1:

ARIEL will be placed in orbit around the Lagrange Point 2 (L2), a gravitational balance point 1.5 million kilometres beyond the Earth’s orbit around the Sun.

Image Credit: ESA/STFC RAL Space/UCL/Europlanet-Science Office


Artist's Impression of ARIEL

Image 2:

Artist's impression of ARIEL on its way to Lagrange Point 2 (L2). Here, the spacecraft is shielded from the Sun and has a clear view of the whole sky.

Image Credit: ESA/STFC RAL Space/UCL/Europlanet-Science Office


Science contact

Prof Giovanna Tinetti
University College London
Mob: +44 (0)7912509617

Technical contact

Paul Eccleston
Mob: +44 (0)7500571666

Media contacts

Anita Heward
Press Officer, ARIEL
Mob: +44 (0)7756 034 243

Madeleine Russell
Communications Officer, RAL Space
Tel: +44 (0) 1235 446288

Dr Rebecca Caygill
Media Relations Manager
UCL Communications & Marketing
Tel: +44 (0)20 3108 3846
Mob: +44 (0)77 3330 7596

Michael Bishop
Senior Communications Officer
Cardiff University
Tel: 02920 874499
Mob: 07713 325300

Notes for Editors

About UCL (University College London)

UCL was founded in 1826. We were the first English university established after Oxford and Cambridge, the first to open up university education to those previously excluded from it, and the first to provide systematic teaching of law, architecture and medicine. We are among the world's top universities, as reflected by performance in a range of international rankings and tables. UCL currently has over 39,000 students from 150 countries and over 12,500 staff. Our annual income is more than £1 billion. | Follow us on Twitter @uclnews | Watch our YouTube channel


RAL Space, based at STFC's Rutherford Appleton Laboratory, carries out an exciting range of world-class space research and technology development. It has had significant involvement in over 200 space missions and is at the forefront of UK Space Research | Follow us on Twitter @RAL_Space_STFC


The Science and Technology Facilities Council (STFC) is keeping the UK at the forefront of international science and tackling some of the most significant challenges facing society such as meeting our future energy needs, monitoring and understanding climate change, and global security. The Council has a broad science portfolio and works with the academic and industrial communities to share its expertise in materials science, space and ground-based astronomy technologies, laser science, microelectronics, wafer scale manufacturing, particle and nuclear physics, alternative energy production, radio communications and radar.

STFC operates or hosts world class experimental facilities including in the UK the ISIS pulsed neutron source, the Central Laser Facility, and LOFAR, and is also the majority shareholder in Diamond Light Source Ltd.

It enables UK researchers to access leading international science facilities by funding membership of international bodies including European Laboratory for Particle Physics (CERN), the Institut Laue Langevin (ILL), European Synchrotron Radiation Facility (ESRF) and the European Southern Observatory (ESO).

STFC is one of seven publicly-funded research councils. It is an independent, non-departmental public body of the Department for Business, Innovation and Skills (BIS). | Follow us on Twitter at @STFC_Matters.

The UK ARIEL team at UCL, STFC RAL Space, Cardiff University, Oxford University, Mullard Space Science Laboratory, STFC RAL Technology Department and UK ATC is supported by the UK Space Agency.