Esa’s Solar Orbiter mission passes crucial milestone

The European Space Agency's ambitious mission to fly closer to the Sun than ever before is now ready for testing, ahead of its 2017 launch

It is hard not to be impressed with the spacecraft standing in the clean room at Airbus Defence and Space, Stevenage. It is a test model for a spacecraft that will travel closer to the Sun than any mission yet flown.

Called Solar Orbiter, it will have to contend with almost 13 times more solar energy than we receive on Earth. This will cause the temperature of its sunward-facing side to soar to 600C. The heat must be radiated away or it will destroy the spacecraft. "Thermal management is always difficult on a spacecraft, but on this mission it's epic," says Tim Horbury at Imperial College, London, who is the principal investigator on the spacecraft's magnetometer instrument.