Comet Interceptor

Comet Interceptor is a European Space Agency mission, in collaboration with JAXA, to visit a long-period comet as it journeys into the inner solar system for the first time, or close to it.^[1] Such a comet, perhaps from the distant Oort Cloud, would carry material little changed since the Sun and planets formed.^[1]

Waiting for a target

Earlier comet missions, including ESA's Giotto and Rosetta, visited short-period comets that have passed the Sun many times and been changed by it.^[1] A truly new comet is usually discovered only months or a few years before its closest approach to the Sun, too late to build and launch a mission to it.^[1]

Comet Interceptor solves this by launching first. Planned to launch in late 2028 or early 2029, it is to wait at the Sun-Earth Lagrange point L2, 1.5 million km from Earth, until a suitable target is found.^[1] It could even be sent to an interstellar object like 'Oumuamua.^[1]

Three spacecraft at once

The mission consists of a main spacecraft and two probes, one of them provided by JAXA.^[1] They travel together and separate one to two days before reaching the comet, then observe it from several points at the same time to build a 3D profile.^[1] Although its target is not yet known, the mission is expected to be completed within six years of launch.^[1]

Comets in general are covered in Comets: what they are and how to see one.