The European Space Agency has selected Thales Alenia Space in the UK to lead a study for the planned mission to "ambush" a passing comet. Called Comet Interceptor, this cosmic brigand represents a new strategy for exploring comets fresh from the Oort cloud by lying in wait, perhaps for years, before embarking on a rendezvous mission.
The past four decades have been marked by a series of ambitious deep-space missions to comets in our solar system. In 1986, an armada of five probes from Europe, the USSR, and Japan flew by Halley's Comet, with the British-built Giotto probe coming within 370 miles (596 km) of the nucleus. Since then, probes have visited several comets, taking samples of their tails of gas and dust, and even landing on the surface.
These missions required years of planning and preparation, so all of the comets visited so far have been ones with very short orbital periods. That means these comets have remained relatively close to the Sun, periodically passing through the inner solar system. It also means that the ice on the surface has sublimated away, leaving behind a crust of dust rather like an aging snowbank on a city street.
While much has been learned from these short-period comets, what scientists really want is one that is in pristine condition. Ideally, one which has only recently, in cosmic terms, had its orbit disturbed and is hurtling toward the Sun on its first and, possibly, only visit.
The problem is that there would be so little warning about the approach of such a comet that conventional missions would never have a chance to prepare, much less launch.
Announced by ESA in June 2019, Comet Interceptor is intended to overcome this by parking in orbit for what could be several years, awaiting the appearance of a new comet suitable for interception.
The composite spacecraft will consist of a mothership and two small probes about 30 cm long that will be deployed as soon as it's on its way to the comet. Flying ahead, they will make a very close pass to help the Comet Interceptor build up the first 3D map of such an object.
ESA has selected Thales Alenia Space in the UK to lead a study to design the mothership, while JAXA will work on the probes.
Comet Interceptor is one of ESA's new "fast" missions designed to weigh under 2,200 pounds (1,000 kg) and be launched as a piggyback payload on another mission. It is slated for launch in 2028.
Source: UK Space Agency, Thales