The European Space Agency's (ESA) Ariel mission, a groundbreaking endeavour to explore the atmospheres of planets outside our solar system, has successfully passed a major development hurdle. The mission, with substantial leadership and funding from the UK, has completed its Critical Design Review (CDR), confirming that its design and development are sufficiently mature for the spacecraft's construction phase to begin.
Ariel, which stands for Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is set to become the first dedicated mission to create a large-scale survey of exoplanet atmospheres. Its primary objective is to study the chemical composition and thermal structures of approximately 1,000 exoplanets, ranging from gas giants to rocky worlds. By analysing the light passing through these atmospheres, scientists hope to gain unprecedented insights into how planets form and evolve, and the conditions that might support life beyond Earth.
The UK plays a pivotal role in the Ariel mission. Scientists and engineers from institutions across the country, including University College London (UCL) and the Rutherford Appleton Laboratory (RAL Space), are leading the mission's science consortium and contributing significantly to the development of its sophisticated instruments. The UK Space Agency has committed substantial funding to the project, underscoring the nation's commitment to cutting-edge space research and its position at the forefront of exoplanet science.
Passing the CDR signifies that the mission's design is robust and meets all technical and scientific requirements. This detailed review involved scrutinising every aspect of the spacecraft, from its scientific instruments and propulsion systems to its operational procedures. With this milestone achieved, the focus now shifts towards the fabrication and assembly of the flight model, a complex process that will involve international collaboration across Europe.
Scheduled for launch in 2029, Ariel will operate from a stable orbit around the second Sun-Earth Lagrange point (L2), approximately 1.5 million kilometres from Earth. From this vantage point, it will have an unobstructed view of the cosmos, allowing its instruments to precisely measure the tiny changes in starlight as exoplanets transit in front of their host stars. These observations will provide the spectral 'fingerprints' of various molecules in exoplanet atmospheres, revealing their composition and temperature.
The data collected by Ariel will be crucial for placing our own solar system in a broader cosmic context, helping scientists to understand the diversity of planetary systems and the prevalence of different planetary types. This research builds upon the foundational work of previous missions like NASA's Kepler and TESS, which have discovered thousands of exoplanets, but Ariel will be the first to systematically characterise their atmospheres on such a large scale.
Source: UK Space Agency