The Comet Interceptor Mission

Abstract

Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum $\varDelta $ Δ V capability of $600\text{ ms}^{-1}$ 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.

Solar Sail Optimal Performance in Heliocentric Nodal Flyby Missions

“…In this paper, the mission scenario mimics the framework used to define the performance characteristics of ESA's Comet Interceptor [10,20]. Specifically, it is assumed that the solar sail-based spacecraft transfer occurs entirely in the ecliptic plane and that the flyby point coincides with one of the two nodes of the heliocentric orbit of a potential small celestial target yet to be discovered.…”

“…Is there any connection between comets and the appearance of life on Earth? In this context, ESA's Comet Interceptor [10] is a mission to a long-period comet designed to answer these fundamental questions. In particular, the Comet Interceptor was proposed to the European Space Agency in 2018 [11], adopted in 2022, and is currently under development [12], with the launch scheduled for 2029 [10].…”

“…ESA's Comet Interceptor mission comprises a mother spacecraft containing two smaller scientific probes, which are scheduled to be released shortly before the flyby with the comet to obtain a three-dimensional observation of the small celestial object and enable multipoint measurements of the comet [13,14]. The mother spacecraft is launched towards a near halo orbit around the Sun-Earth L 2 point, and there it remains parked, with minor maintenance manoeuvres, awaiting the discovery of a new celestial small body to intercept, for a total duration of between a few months and four years [10]. The main spacecraft is equipped with a chemical propulsion system designed to provide a minimum transfer ∆V capability of 600 m/s [10].…”

“…The mother spacecraft is launched towards a near halo orbit around the Sun-Earth L 2 point, and there it remains parked, with minor maintenance manoeuvres, awaiting the discovery of a new celestial small body to intercept, for a total duration of between a few months and four years [10]. The main spacecraft is equipped with a chemical propulsion system designed to provide a minimum transfer ∆V capability of 600 m/s [10]. To avoid costly manoeuvres (in terms of velocity change) outside the initial orbital plane, the long-period comet must be intercepted at one of the two nodal points of intersection of its orbit with the ecliptic plane.…”

“…The latter is defined by the pairs {r f , ∆θ} that the interplanetary spacecraft can reach with the prescribed (maximum) value of velocity change in an assigned (maximum) value of flight time, i.e., within an assigned (maximum) time interval. The results of the study of ESA's Comet Interceptor mission showed that the reachable zone by a direct transfer is essentially confined to the case where r f > 1 au and ∆θ > 0 deg (i.e., the small celestial target is behind Earth at the encounter point), while in order to reach an encounter point with ∆θ < 0 (i.e., ahead of Earth) it is necessary to exploit a trajectory that includes one (or multiple) Moon gravityassist maneuver [10]. In this sense, each point in the reachability zone (i.e., the generic pair {r f , ∆θ}) is characterized by a value of the flight time and the required velocity change.…”