British engineers are to start work on a new spacecraft that will lie in wait for passing comets then chase them down and map their surfaces in three dimensions.
Appropriately dubbed the “comet chaser”, the mission will not only record details of the comets’ contours, but also the composition of the dust and and gases released as they hurtle through the heavens.
The mission involves three spacecraft that are designed to collaborate on the job. The mothership, to be built in the UK by Thales Alenia Space, will hold two smaller robotic probes from Japan that can be released near the target comet for extremely close fly-bys. These probes will then beam images and other data back to the mothership.
Comets are lumps of cosmic detritus left over from the birth of the solar system some 4.6bn years ago. Many are detected as they streak around the sun, causing them heat up and shed dust and vapour that stretches out into a spectacular tail.
With the comet chaser, astronomers hope to catch up with a comet before it becomes so active, allowing the twin robotic probes – each only 30cm long – to map and analyse the pristine comet nucleus that would otherwise be obscured.
“It’s going to be fascinating,” said Andrew Stanniland, CEO of Thales Alenia Space. “Most comets we see have been through the solar system many times and that means they are changed by the sun. This mission allows us to have a spacecraft in orbit so we can catch a pristine object. It will give us science about the history of our solar system that we’ve never had before.”
Due for launch in 2028, the spacecraft officially known as the Comet Interceptor, will head for a gravitational no-man’s land on the opposite side of the Earth to the sun. By loitering at this so-called Lagrange point, where the forces of gravity tend to make things stay put, the mission can await its quarry while burning a minimum of fuel.
The mission may have to wait in orbit for years before astronomers spot a suitable target for the spacecraft to investigate. If not a comet from the Oort cloud – a mysterious band of icy debris far beyond Neptune – the spacecraft could chase down an interstellar object like Oumuamua. The cigar-shaped asteroid tumbled into the solar system in 2017 but astronomers had no mission capable of catching it.
The Comet Interceptor, proposed by an international team led by UCL, Edinburgh University and others, is the first of the European Space Agency’s “fast” missions. The whole mission less than a tonne and must hitchhike into space on a rocket already scheduled for launch. The Comet Interceptor will launch in 2028 with the Ariel space telescope, a UK-backed ESA mission to study the atmospheres of alien planets orbiting distant stars.