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Deciphering Comets: A Mission Concept for a Cometary Characterization and Observation Apparatus Cube-sat (CoCOA-Cube)

Presentation #311.10 in the session Future Missions and Instrumentations - Icy Bodies, Exoplanets, Stars (Poster + Lightning Talk)

Published onOct 23, 2023
Deciphering Comets: A Mission Concept for a Cometary Characterization and Observation Apparatus Cube-sat (CoCOA-Cube)

Comets represent some of the most pristine, observable material remaining from the era of Solar System formation. Since today’s comets were once part of the icy planetesimals, comets are vital to our understanding of the chemical and physical properties of our natal protoplanetary disk. However comets have also experienced 4.5 Gyr of various evolutionary processes that have changed their physical and compositional properties. The census of known comets has greatly expanded in recent years, though their characterization lags behind. Typical data for a given comet is often limited to somewhat sparse photometric information about the dust production rate. Repeated measurements of gas production rates as a function of heliocentric distance – a more fundamental measurement since it is tied to the basic process driving cometary activity in the first place – happen for relatively few comets. This is not to diminish the significant results and insights from extensive surveys of daughter species production and organic volatile components. Our mission concept envisions a broader observational campaign that could provide synoptic monitoring of parent species among a large number of comets. This would enhance assessments of ensemble properties and evaluations of activity, surface, and interior evolution. We are specifically concerned here with addressing the relative lack of simultaneous production rate measurements of two of the most abundant volatile species, H2O and CO2. While water can be measured by proxy through its daughter product OH’s fluorescence band near 309 nm, there can be significant atmospheric extinction. CO2 is an even more challenging species to study since, e.g., the atmosphere is opaque at its asymmetric-stretch vibrational band near 4.26 microns. Thus it is difficult in practice to constrain the total volatile mass loss from comets. We propose a space-based imaging all-sky survey to measure both OH and CO2 emissions simultaneously by using a 6U CubeSat platform configuration. The survey’s science goals would be to: (i) find the distribution of CO2 production rates and abundances relative to water across the whole comet population and across its subgroups; (ii) assess the two species’ dependences on each other and on heliocentric distance; (iii) tie modeling results to evolutionary processes. We plan to conduct observations in four narrow bands: a 309 nm band for OH emission, a 4.26 micron band for CO2 emission, and two nearby bands each just off the main OH or CO2 band respectively. We will thus be able to distinguish comets from other astronomical sources by their colors. Our main instrumentation contribution would be in developing a 3U-length appropriate optical apparatus that can provide imaging in both the near-UV and the near-IR. A low-Earth polar orbit and a wide field of view (~tens of degrees) toward the antisolar direction will maximize the efficiency and feasibility of our planned survey. The telescope optics can be extremely fast, with scales of ~arcmin per pixel, since we are searching for gas comae that are extended sources. The proposed approach represents an innovative and cost-effective way to greatly advance our knowledge of both the current state of cometary bodies and the relation to natal planetary disk conditions and evolution. We will perform measurements that traditionally require either major spacecrafts, dedicated satellites or combined ground-observing campaigns.

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