Due to launch in 2028, Comet Interceptor will initially sit at the L2 Lagrange point, 1.5 million miles from the Earth in the opposite direction to the Sun. It will lie in wait at L2 until a suitable pristine comet – or interstellar object such as Oumuamua – is spotted travelling inward from beyond the solar system.
The mothership will then chart a course to intercept its target, passing within 1,000 miles, with two ‘daughter’ spacecraft sent in for closer observations. Each module will be equipped with a complementary science payload, providing different perspectives of the object's nucleus and its gas, dust, and plasma environment. The mothership will relay the findings back to Earth. ESA selected the project as the first in a new class of ‘Fast’ missions, which use existing, flight-proven technology to speed up the pathway from mission concept to implementation.
“I’m delighted that our academic community impressed ESA with a vision of what a small, fast science mission can offer,” said Chris Lee, head of Science Programmes at the UK Space Agency.
“In 1986 the UK-led mission to Halley’s Comet became the first to observe a cometary nucleus and, more recently, UK scientists took part in another iconic European comet mission, Rosetta. Now our scientists will build on that impressive legacy by attempting to visit a pristine comet for the very first time and learn more about the origins of our solar system.”
Celestial objects such as Oumuamua or virgin comets travelling in from the Oort cloud – which lies beyond the heliosphere in interstellar space – have been untouched by the Sun’s heat. As a result, they should hold scientific information about the early stages of the solar system, and perhaps even earlier than that. But these ‘time capsules’ are usually only detected shortly before entering the inner solar system, which is why Comet Interceptor will have to park at L2, awaiting the right opportunity.
“Pristine or dynamically new comets are entirely uncharted and make compelling targets for close-range spacecraft exploration to better understand the diversity and evolution of comets,” said Günther Hasinger, ESA’s Director of Science.
“The huge scientific achievements of Giotto and Rosetta – our legacy missions to comets – are unrivalled, but now it is time to build upon their successes and visit a pristine comet, or be ready for the next ‘Oumuamua-like interstellar object."
The scheduled launch in 2028 means the mission will share a rocket with another UK-led mission – the ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) space telescope, which aims to study the atmospheres of around 1,000 exoplanets.
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