The European Space Agency (ESA) has whittled down the list of projects it is considering for deployment in the year 2025 and is now considering three missions for liftoff in that year.
The three projects are:
- Ariel, aka Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, which would analyse the atmospheres of around 500 planets orbiting close to nearby stars, to determine their chemical composition and physical conditions.” This one's all about learning more about how planets form and work.
- Thor, the Turbulence Heating ObserveR, would study “the interaction of the solar wind with Earth’s magnetic field” and “address a fundamental problem in space plasma physics concerned with the heating of plasma and the subsequent dissipation of energy.”
- Xipe, the X-ray Imaging Polarimetry Explorer, could check out “X-ray emissions from high-energy sources such as supernovas, galaxy jets, black holes and neutron stars, to discover more about the behaviour of matter under extreme conditions.”
All three missions are “M-Class”, the agency's designation for medium-sized missions. There's also an “S” and “L” class and readers will not be surprised to learn they stand for “small” and “large” respectively.
S-Class missions include the CHEOPS exoplanet-spotter that will go aloft in 2017 and take over from the venerable Kepler craft. S-Class missions are designed to be cheap and fast. L-Class missions are the agency's most ambitious and expensive efforts. The first – JUICE, aka the JUpiter ICy moons Explorer – is expected to launch in 2022, arrive at the gas giant in 2030 and carry out observations for at least three years.
The ESA uses the three classes to ensure it has a pipeline full of missions, and a budgeting process to match.
Final decisions on which of Ariel, Thor or Xipe will win a launch are expected in the next year or so. Sadly, there can only be one but the boffin behind each have done well to make it this far: 24 other proposals didn't make the shortlist.
Three other M-Class missions have already been signed off. The Solar Orbiter is expected to launch in 2017 and will conduct close-range observations of Sol. Euclid will try to find dark matter and/or energy after a year 2020 launch, while 2024 should send PLATO to look for exoplanets.
The S-M-L classification was introduced long after the ESA's decision to do things like the Rosetta comet-spotter, whose work is depicted above. ®