Comet interceptor: an ESA mission to a dynamically new solar system object

Abstract

While the scientific merits of past comet missions are unquestioned, previously visited comets had all approached the Sun on many occasions and, as a consequence, have also undergone substantial compositional and morphological alterations. Comet Interceptor (Comet-I) was recently selected as ESA’s first fast-track class mission and aims to explore a pristine comet, which will ideally be visiting the inner Solar System for the first time. Comet-I will hitch a ride to a Sun-Earth L2 quasi-halo orbit, as a co-passenger in ESA’s M4 ARIEL’s launch, in 2028. It will then remain there waiting for the right departure conditions to definitively leave the L2 point and intercept a newly discovered comet. Comet-I will be the first mission to be design and, possibly launched, without an identified target. Nevertheless, a Monte Carlo analysis modelling the uncertainties of the long period comet population and the spacecraft transfer capabilities demonstrate the high likelihood of completing the mission within 6 years. A few days before the closest approach Comet-I will release two small independent probes (~30 kg each) into fly-by paths with close approach distances in the order of a few hundred kilometres, while the main spacecraft (~700 kg) will take a safer path (~1000 km) to protect it from the dust environment. Comet-I will thus involve three spacecraft elements working together to ensure a low-risk, bountiful, interdisciplinary scientific return through unprecedented multipoint measurements