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1. Dimorphos’s Orbit Period Change and Attitude Perturbation due to Its Reshaping after the DART Impact

Author

Ryota Nakano, Masatoshi Hirabayashi, Sabina D. Raducan, Petr Pravec, Shantanu P. Naidu, Harrison F. Agrusa, Steven Chesley, Fabio Ferrari, Martin Jutzi, Colby C. Merrill, Alex J. Meyer, Patrick Michel, Derek C. Richardson, Paul Sánchez, Peter Scheirich, Stephen R. Schwartz, Yun Zhang, Adriano Campo Bagatin, Po-Yen Liu, and Andrew F. Cheng

Subjects
Near-Earth objects, Asteroid satellites, Asteroid dynamics, Two-body problem, Asteroid rotation, Gravitational interaction, Astronomy, QB1-991
Abstract

On 2022 September 26 (UTC), NASA's Double Asteroid Redirection Test (DART) mission achieved a successful impact on Dimorphos, the secondary component of the near-Earth binary asteroid system (65803) Didymos. Subsequent ground-based observations suggest a significant reshaping of Dimorphos, with its equatorial axis ratio changing from 1.06 to ∼1.3. Here we report the effects of this reshaping event on Dimorphos's orbit and attitude. Given the reported reshaping magnitude, our mutual dynamics simulations show that approximately 125 s of the observed 33 minute orbit period change after the DART impact may have resulted from reshaping. This value, however, is sensitive to the precise values of Dimorphos's post-impact axis ratios and may vary by up to 2 times that amount, reaching approximately 250 s within the current uncertainty range. While the rotational state of the body is stable at the currently estimated axis ratios, even minor changes in these ratios or the introduction of shape asymmetry can render its attitude unstable. The perturbation to Dimorphos’s orbital and rotational state delivered by the impact directly, combined with any reshaping, leads to a strong possibility for a tumbling rotation state. To accurately determine the momentum enhancement factor ( β ) through measurements by the European Space Agency’s Hera spacecraft and to evaluate the effectiveness of the kinetic deflection technique for future planetary defense initiatives, the effects of reshaping should not be overlooked.

Published
2024
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3. Momentum Transfer from the DART Mission Kinetic Impact on Asteroid Dimorphos

Author

Andrew F. Cheng, Harrison F. Agrusa, Brent W. Barbee, Alex J. Meyer, Tony L. Farnham, Sabina D. Raducan, Derek C. Richardson, Elisabetta Dotto, Angelo Zinzi, Vincenzo Della Corte, Thomas S. Statler, Steven Chesley, Shantanu P. Naidu, Masatoshi Hirabayashi, Jian-Yang Li, Siegfried Eggl, Olivier S. Barnouin, Nancy L. Chabot, Sidney Chocron, Gareth S. Collins, R. Terik Daly, Thomas M. Davison, Mallory E. DeCoster, Carolyn M. Ernst, Fabio Ferrari, Dawn M. Graninger, Seth A. Jacobson, Martin Jutzi, Kathryn M. Kumamoto, Robert Luther, Joshua R. Lyzhoft, Patrick Michel, Naomi Murdoch, Ryota Nakano, Eric Palmer, Andrew S. Rivkin, Daniel J. Scheeres, Angela M. Stickle, Jessica M. Sunshine, Josep M. Trigo-Rodriguez, Jean-Baptiste Vincent, James D. Walker, Kai Wünnemann, Yun Zhang, Marilena Amoroso, Ivano Bertini, John R. Brucato, Andrea Capannolo, Gabriele Cremonese, Massimo Dall’Ora, Prasanna J. D. Deshapriya, Igor Gai, Pedro H. Hasselmann, Simone Ieva, Gabriele Impresario, Stavro L. Ivanovski, Michèle Lavagna, Alice Lucchetti, Elena M. Epifani, Dario Modenini, Maurizio Pajola, Pasquale Palumbo, Davide Perna, Simone Pirrotta, Giovanni Poggiali, Alessandro Rossi, Paolo Tortora, Marco Zannoni, Giovanni Zanotti, Cheng A.F., Agrusa H.F., Barbee B.W., Meyer A.J., Farnham T.L., Raducan S.D., Richardson D.C., Dotto E., Zinzi A., Della Corte V., Statler T.S., Chesley S., Naidu S.P., Hirabayashi M., Li J.Y., Eggl S., Barnouin O.S., Chabot N.L., Chocron S., Collins G.S., Daly R.T., Davison T.M., DeCoster M.E., Ernst C.M., Ferrari F., Graninger D.M., Jacobson S.A., Jutzi M., Kumamoto K.M., Luther R., Lyzhoft J.R., Michel P., Murdoch N., Nakano R., Palmer E., Rivkin A.S., Scheeres D.J., Stickle A.M., Sunshine J.M., Trigo-Rodriguez J.M., Vincent J.B., Walker J.D., Wünnemann K., Zhang Y., Amoroso M., Bertini I., Brucato J.R., Capannolo A., Cremonese G., Dall’Ora M., Deshapriya P.J.D., Gai I., Hasselmann P.H., Ieva S., Impresario G., Ivanovski S.L., Lavagna M., Lucchetti A., Epifani E.M., Modenini D., Pajola M., Palumbo P., Perna D., Pirrotta S., Poggiali G., Rossi A., Tortora P., Zannoni M., Zanotti G., Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), CNRS through the MITI interdisciplinary programmes, CNES, ESA, and European Project: 870377,NEO-MAPP

Subjects
asteroids, bulk density, geometry, 530 Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], kinetic, FOS: Physical sciences, satellite imagery, size, Article, motion, ma, controlled study, uncertainty, planetary defense, Earth and Planetary Astrophysics (astro-ph.EP), Multidisciplinary, asteroid, 520 Astronomy, momentum transfer, 620 Engineering, astronomy, preliminary data, [SDU]Sciences of the Universe [physics], DART, Astrophysics - Earth and Planetary Astrophysics
Abstract

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos's along-track orbital velocity component of 2.70 +/- 0.10 mm/s, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg/m$^3$, we find that the expected value of the momentum enhancement factor, $\beta$, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg/m$^3$, $\beta$= 3.61 +0.19/-0.25 (1 $\sigma$). These $\beta$ values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos., Comment: accepted by Nature

Published
2023
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7. Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris.

Author

James Baer and Steven Chesley

Subjects
*ASTEROIDS, *FORCING (Model theory), *MODEL theory, *SOLAR system
Abstract

Abstract  We apply the technique of astrometric mass determination to measure the masses of 21 main-belt asteroids; the masses of 9 Metis (1.03 ± 0.24 × 10-11 M⊙), 17 Thetis (6.17 ± 0.64 × 10-13 M⊙), 19 Fortuna (5.41 ± 0.76 × 10-12 M⊙), and 189 Phthia (1.87 ± 0.64 × 10-14 M⊙) appear to be new. The resulting bulk porosities of 11 Parthenope (12±4%) and 16 Psyche (46±16%) are smaller than previously-reported values. Empirical expressions modeling bulk density as a function of mean radius are presented for the C and S taxonomic classes. To accurately model the forces on these asteroids during the mass determination process, we created an integrated ephemeris of the 300 large asteroids used in preparing the DE-405 planetary ephemeris; this new BC-405 integrated asteroid ephemeris also appears useful in other high-accuracy applications. [ABSTRACT FROM AUTHOR]

Published
2008
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