Comet Radar Explorer (CoRE) David Geng, Reece Elling, and Matthew Lees

Comet Background Comets are believed to be composed of leftover material from the beginning of our solar system around 4.6 Ga Composed primarily of ice (both water and frozen gases such as ammonia or methane) and dust that didn’t get incorporated into planetary formation Formed of a solid, frozen nucleus often only a few kilometers in diameter

Comet Background Comets have elongated elliptical orbits where they only come close to Earth and the Sun for a short part of their orbit As the comet reaches its perihelion, the sun warms it up, causing the ices to change to gases forming a coma that can extend hundreds of thousands of kilometers Sunlight and solar wind blow the coma dust and gas so that a comet's tail is always pointing away from the sun

Comet Background Often classified by the length of their orbital periods: Long-Period (200 to 100,000’s of years) that likely originate from the Oort Cloud Short-Period (< 200 years) that likely originate from the Kuiper Belt outside of Neptune’s orbit (ex. Halley’s) Comets that orbit near a major planet are typically called its “family” For example, Jupiter-family comets (JFCs) all have short orbital periods less than 20 years Over 500 JFCs have been identified, and these are good targets for study due to the short orbital periods

Comet Background Often classified by the length of their orbital periods: Long-Period (200 to 100,000’s of years) that likely originate from the Oort Cloud Short-Period (< 200 years) that likely originate from the Kuiper Belt outside of Neptune’s orbit (ex. Halley’s) Comets that orbit near a major planet are typically called its “family” For example, Jupiter-family comets (JFCs) all have short orbital periods less than 20 years Over 500 JFCs have been identified, and these are good targets for study due to the short orbital periods

Comet 10P/Tempel 2 Target of the CoRE mission Discovered by Willhelm Tempel in 1873 and observed extensively since, making it one of the best studied members of Jupiter’s family of short-period comets One of the largest known comet nuclei, roughly 16x8x8 km Very active, especially given its size

Comet 10P/Tempel 2 Target of the CoRE mission Discovered by Willhelm Tempel in 1873 and observed extensively since, making it one of the best studied members of Jupiter’s family of short-period comets One of the largest known comet nuclei, roughly 16x8x8 km Very active, especially given its size

Key Scientific Issues Or More Simply Origins of cometary nuclei How do primitive bodies accrete? Composition throughout interior Physical and geological evolution Mechanisms driving their spectacular activity Or More Simply How did it form? What are we actually seeing? Is it mostly ice? How does it work?

Why is this important? In-depth studies of comets can likely yield important clues about the formation of our solar system May have been the primary carriers of water and organic compounds - the building blocks of life - to early Earth

Why is this important? Still many unanswered questions about the geology of comets: Do global layers that we see on the surface persist through to the interior? Are smooth regions indications of landslides or could they be cryovolcanic? Are pits impact craters of sublimation pits rooted in the interior? Comet C-G

Timeline Depart July 2021 FlyBy Earth in July 2023 Arrive in November 2026 On Arrival Approach and flyby Tempel 2 Optical Mapping Orbit Radar Mapping Orbit - primary mission phase

Mission Approach and Flybys Assess the active regions Obtain the required tracking and imaging data for orbit. Optical Mapping Orbit (OMO) A sequence of ~9 to 11 am/pm polar orbits For multi-wavelength visible imaging and photometry Measurements of temperature and thermal inertia Radar Mapping Orbit (RMO) Radar “Cat Scan” of the nucleus By looking at the visible and infrared parts of the spectrum, THEMIS is determining the distribution of minerals on the surface of Mars and helping scientists understand how the mineralogy of the planet relates to the landforms.

Instruments on CORE Science and Navigation Camera (SNC) Designed the same as DLR Framing Camera on DAWN mission Will obtain color images and photometric observations globally to a pixel scale <3m Helpful for understanding geology and for constructing the comet nucleus shape model and optical navigation Show is a three-dimensional color image of one of Vesta’s smaller craters made using this camera.

Instruments on CORE Comet Infrared Imager (CIRI) High-heritage microbolometer imager sensitive to the 120-350 K temperature range expected at the nucleus Will obtain repeated daytime/nighttime images that are co-aligned with the multi-wavelength visible images is a high-heritage microbolometer (7-25 μm) imager sensitive to the 120-350 K temperature range expected at the nucleus (modeled below). It will be built at ASU by the team that delivered THEMIS for Mars Odyssey. CIRI will obtain repeated daytime/nighttime images, that are co-aligned with the multi-wavelength visible images.

Instruments on CORE SHARAD Heritage Radar SHAllow subsurface RADar Used for reflection radar imaging hardware and data processing Will give us a “Cat Scan” of the nucleus using coherent reflection sounding measurements On board the Mars Reconnaissance Orbiter (MRO) Much simpler to use on a comet than on a planet A reflection radar deployed in orbit about a comet will enjoy significant simplifying benefits compared to using the same instrument for Mars or lunar radar science: (1) The proximity of operations leads to a much higher signal to noise, as much as +30 dB. (2) The lack of an ionosphere simplifies data modeling and analysis. (3) The body is globally illuminated during every data acquisition, minimizing ambiguity or 'clutter' and allowing for tomographic reconstruction.

SHARAD processed images from MRO MRO = Mars Reconnaissance Orbiter Take the SHARAD observations from collections of 2-D profiles to geometrically corrected 3-D volumes for each polar region. Crucial to focused processing of orbital radar data is an accu- rate representation of the spacecraft velocity and the local surface slope. Horizontal reflectors directly below the spacecraft typically yield the strongest surface and subsurface returns.

How this affects life on Earth? Helps us understand where life potentially came from (seeding) Simple life forms could have started on comets Bodies it has made contact with could have pre- seeded it Transported life to earth when the comet landed Amino Acids found on Comet Wild 2

How this affects life on Earth? Structure of comet can help us learn where volatile substances came from Studying core of Tempel 2 can potentially find new volatile substances hidden inside

How this affects life on Earth? Learning more about the physical attributes of a comet can allow us to better estimate the amount of force released during collisions Could potentially help us negate hazardous objects

How this affects life on Earth? Tells us about elements at the beginning of solar system Collects elements from outer solar system and brings them closer to us Lets us examine clues from the outer system