Hayabusa2# mission target 1998 KY26 preview: a small optically bright rapid rotator

Hayabusa2# mission target 1998 KY26 preview: a small optically bright rapid rotator | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hayabusa2# mission target 1998 KY 26 preview: a small optically bright rapid rotator Toni Santana-Ros, Przemyslaw Bartczak, Karri Muinonen, Agata Rozek, and 15 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5821856/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Sep, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Understanding the physical characteristics of small bodies in the Solar System is crucial for refining models of their formation and evolution. Although several kilometre-sized asteroids have already been visited by spacecraft, 1998 KY26 will be the first asteroid in the decametre range to be explored in situ. Its diameter and spin period place it above the spin barrier, suggesting that its formation and properties may differ from those of previously visited bodies. However, the key physical characteristics of 1998 KY26 remain poorly understood. We conducted a photometric observing campaign during 1998 KY26’s close approach to Earth in 2024. Our observations revealed that 1998 KY26 has a high optical albedo and colours consistent with an E-type taxonomy. We also determined its spin period to be (5.3516 ± 0.0001) minutes—twice as fast as previously reported. Using lightcurve inversion methods, we derived a retrograde pole solution and constructed convex and non-convex shape models. By integrating these models with Goldstone radar data from 1998, we estimated 1998 KY26’s diameter to be (11 ± 2) m. The most likely structure for 1998 KY26 is monolithic, yet a fine grained rubble-pile structure is theoretically possible given its required small strength level. We found that it will be possible to validate these results with future JWST observations. Our comprehensive characterisation of 1998 KY26 can inform the planning of the Hayabusa2# spacecraft’s rendezvous encounter, scheduled for July 2031. Additionally, it provides valuable insights into the non-gravitational forces acting on small Solar System bodies, enhancing our understanding of their orbital evolution which could shed light on the nature of dark comets. Physical sciences/Astronomy and planetary science/Planetary science/Asteroids, comets and Kuiper belt Physical sciences/Astronomy and planetary science/Planetary science/Inner planets Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Published Journal Publication published 18 Sep, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5821856","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":402148937,"identity":"60a94193-4399-4040-a5e1-ea565be7f6d5","order_by":0,"name":"Toni Santana-Ros","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIiWNgGAWjYJADxgcJIEoCiHnwKAPLHYCwmQ1I1sImwUCMFnv+w88ef6i5I2/e3v6s4kGNHYPB7QbGB2/b8NgikWZucODYM8M5Z86Y3Ug4lsxgcOcAs+FcvFoYzCQOsB1mnCGRw3YjseEAg8GNBDZpXnxa+I9/kzjw77D9DIn0ZwVQLey/8WphyDGTONh2OHGGRIIZA8wWZrxabuSUSZztO5w8g+eMsQTQLzySdw42S845h1sLe//xbRIV3w7bzmBvf/jxR42dHN/t5oMf3pTh1oLFpQyMDSSoHwWjYBSMglGADQAAZApSMvAe5EMAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-0143-9440","institution":"Universidad de Alicante","correspondingAuthor":true,"prefix":"","firstName":"Toni","middleName":"","lastName":"Santana-Ros","suffix":""},{"id":402148938,"identity":"c0387501-7d68-4664-82e3-87cd77b44526","order_by":1,"name":"Przemyslaw Bartczak","email":"","orcid":"","institution":"Astronomical Observatory Institute, Faculty of Physics, A. 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