Instruments on board the comet interceptor ESA mission

Comet Interceptor (Comet-I), selected by the European Space Agency (ESA) in June 2019, is the first Fast-Class Science mission with a short development time and a strict limit for the cost at completion. The Comet-I instruments are expected to be qualified for flight by early 2026. Comet-I will be launched to the Sun-Earth L2 point sharing an Ariane 6.2 launch with ESA’s ARIEL satellite. Comet-I will remain at L2 until its departure to a yet-to-be-discovered long period comet or interstellar body. Comet-I will then perform a fly-by of the comet nucleus and will release two small probes: probe B1 provided by JAXA and probe B2 provided by ESA. These probes will fly closer to the comet nucleus. The mission’s primary science goal is to characterise for the very first time with multi-point observations, a Long-Period comet, dynamically new, or an interstellar object. This paper describes the suite of instruments which are under development, both for the mother spacecraft (S/C A) and for the small probe B2 under ESA responsibility. The instruments on board spacecraft A are: <li> CoCa: Comet Camera - to obtain high resolution images of the comet's nucleus at several wavelengths, developed by a consortium led by University of Bern </li> <li> MANiaC: Mass Analyzer for Neutrals in a Coma - a mass spectrometer to sample the gases released from the comet, developed by a consortium led by University of Bern </li> <li> MIRMIS: Modular InfraRed Molecules and Ices Sensor - to measure the thermal radiation released from the comet's nucleus and study the molecular composition of the gas coma, developed by a consortium led by University of Oxford in the UK and VTT in Finland </li> <li> DFP-A: Dust, Field and Plasma package - to detect and measure charged gases, energetic neutral atoms, magnetic fields, and dust surrounding the comet, developed by a consortium led by CBK in Poland. </li> The instruments on board probe B2 are: <li> OPIC: Optical Periscope Imager for Comets - mapping of the nucleus and its surrounding coma and dust environment, developed by University of Tartu in Estonia in collaboration with an industrial contractor. </li> <li> EnVisS: Entire Visible Sky coma mapper - to map the entire sky within the comet’s coma, using a fisheye lens. It is developed by a consortium led by CNR in Italy and IAA in Spain based on a designed initially developed by MSSL in the UK. </li> <li> DFP-B: Dust, Field, and Plasma - a subset of DFP sensors on spacecraft A, developed by a consortium led by CBK in Poland. </li>Despite being a fast development mission with very strict programmatic boundaries, Comet Interceptor includes a comprehensive suite of instruments addressing all major topics related to cometary science as requested by the European cometary science community. The main technical challenges of the instruments are the need to comply with very low mass and low power consumptions, particularly for probe B2. Also, limited time is available for the development which requires the use of technological solutions with high technology readiness level (TRL) in combination with early technology development. The instruments underwent their preliminary requirement review (PRR) in 2020 and a system requirement review (SRR) approximately 1 year after, in 2021. The preliminary design review (PDR) was successfully held in mid-2022. An extensive critical design review (CDR) has been held in the second half of 2023 and is under closure. The delivery of the electrical and functional models of the instruments to the satellite Prime Contractor is on-going, to allow the test of the satellite avionic test bench to start. The instrument flight models are expected to be completed between the end of 2025 and the beginning of 2026.