UCL to lead European ARIEL mission to study exoplanets

UCL is to lead the €450m ARIEL mission to study newly discovered planets after it was chosen as the next European Space Agency (ESA) science expedition.

Hot exoplanet

Due for launch in mid-2028, ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) will set out over four years to answer fundamental questions about how planetary systems form and evolve.

The spacecraft will do this by observing 1000 planets orbiting distant stars and conducting 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.

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 Oxford University.

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 study a number of exoplanets – ranging from Jupiter- and Neptune-size planets down to so-called super-Earths – in a variety of environments, but will focus mainly on warm and hot planets in orbits close to their star.

The high temperatures on these planets, which can be in excess of 2000 degrees Celsius, keep different molecular species circulating throughout the atmosphere, where they can be detected and studied. Similarly, as more molecules from the planet’s interior make their way into the atmosphere, ARIEL will be provided with better information about the planet’s internal composition and the formation of the planetary system.

ARIEL will be equipped with a meter-class telescope primary mirror to collect visible and infrared light from distant star systems. A spectrometer will then 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, which is due to open in mid-2020 following a £99m investment as part of the UK government’s Industrial Strategy Challenge Fund.

ARIEL in numbers:

  • Elliptical primary mirror: 1.1m x 0.7m
  • Instrumentation: Three photometric channels and three low resolution spectrometers covering from 0.5 to 7.8 microns in wavelength
  • Mission lifetime: Four years in orbit
  • Launch date: Mid 2028
  • Payload mass: ~450kg
  • Total Spacecraft Dry mass: ~1200kg
  • Launch mass: ~1300kg
  • Destination: Sun – Earth Lagrange Point 2 (L2)
  • ESA Mission Cost: ~€450m, plus nationally funded contribution of the payload
  • Launch vehicle: Ariane 6-2 from French Guiana