Comet Interceptor

Mission

The Comet Interceptor mission was selected by ESA in June 2019 to combine this breakthrough in comet discoveries with a compact, agile set of spacecraft that can reveal to us a huge amount about a long period comet, ideally one is truly pristine, entering the inner Solar System for the first time. Although far rarer than long-period comets, Comet Interceptor will also have the capability of encountering an interstellar object passing through our Solar System if such an object is found on a suitable trajectory.

Previous missions only visited short-period comets (< 200 years) originating from the Kuiper Belt region, because their orbits are well known and there is enough time to design and manufacture a space-probe. The goal of the Comet Interceptor mission is to visit a long-period comet, coming from the Oort Cloud and entering the inner part of the Solar System for the first time. Its surface has therefore not yet been altered by high amounts of solar radiation. Such an object is called a Dynamically New Comet (DNC) and is usually detected about one year before perihelion, which is too little time to de- sign and manufacture the probe. Comet Interceptor circumvents this issue by being the first of many ESA F-class (fast class) missions. An F-class mission will hitch a ride on a larger M-class (medium class) mission and must be built within approximately eight years. Comet Interceptor will launch together with the ARIEL exoplanet telescope and then remain in the Sun-Earth Lagrange point L2. After a target has been selected, Comet Interceptor will be deployed and depart from L2 to intercept the comet.

Comet Interceptor is made up of three separate spacecrafts: A mothership (A) and two smaller daughterships (B1 and B2). The three will detach weeks prior to closest approach and adjust their course in such a way, that the mothership can perform a distant fly-by at around 1000 km whereas the daughterships will perform high-risk/high-return measurements much closer to the nucleus. The approach phase, where the spacecrafts travel perpendicular to the direction of the nucleus is shown in Figure 1.3. Comet Interceptor can potentially reach the comet in a range of 0.85 to 1.35 au. from the Sun.

A schematic view of the mission.
The proposed general encounter sequence for Comet Interceptor, not to scale. Green, blue and red lines are the trajectories of spacecraft (SC) A, B1 and B2, respectively. SC A passes farthest from the nucleus, performing remote sensing observations and receiving data from SC B1 and B2, which follow near-parallel trajectories nearer the nucleus. Post-encounter, SC A transmits stored data from all three platforms to Earth. The final SC, payload and precise flyby scenario may change as the mission development proceeds. Jones, G.H., Snodgrass, C., Tubiana, C. et al. The Comet Interceptor Mission. Space Sci Rev 220, 9 (2024). https://doi.org/10.1007/s11214-023-01035-0

The instruments for the main and an accompanying spacecraft:

  • Spacecraft A: (ESA)
    • CoCa: Comet Camera - to obtain high resolution images of the comet's nucleus at several wavelengths. 
    • MANIaC: Mass Analyzer for Neutrals in a Coma - a mass spectrometer to sample the gases released from the comet.
    • MIRMIS: Multispectral InfraRed Molecular and Ices Sensor - to measure the heat radiation being released from the comet's nucleus and study the molecular composition of the gas coma.
    • DFP : Dust, Field, and Plasma - to understand the charged gases, energetic neutral atoms, magnetic fields, and dust surrounding the comet.
  • Spacecraft B1: (JAXA)
    • HI: Hydrogen Imager - UV camera devoted to studying the cloud of hydrogen gas surrounding the target
    • PS: Plasma Suite - to study the charged gases and magnetic field around the target
    • WAC: Wide Angle Camera - to take images of the nucleus around closest approach from an unique viewpoint
  • Spacecraft B2: (ESA)
    • OPIC: Optical Imager for Comets - mapping of the nucleus and its dust jets at different visible and infrared wavelengths.
    • EnVisS: Entire Visible Sky coma mapper  - to map the entire sky within the comet's head and near-tail, to reveal changing structures within the dust, neutral gas, and ionized gases.
    • DFP : Dust, Field, and Plasma - a subset of DFP sensors on spacecraft A.