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Final Reconstruction of Asteroid Bennu's Particle Ejection Events from Sparse Data
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  • John Pelgrift,
  • Erik Lessac-Chenen,
  • Coralie Adam,
  • Jason Leonard,
  • Derek Nelson,
  • Leilah McCarthy,
  • Eric Sahr,
  • Andrew Liounis,
  • Michael Moreau,
  • Brent Bos,
  • Carl Hergenrother,
  • Dante Lauretta
John Pelgrift
KinetX

Corresponding Author:john.pelgrift@kinetx.com

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Erik Lessac-Chenen
KinetX, Inc.
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Coralie Adam
KinetX, Inc.
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Jason Leonard
KinetX, Inc.
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Derek Nelson
KinetX, Inc.
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Leilah McCarthy
KinetX, Inc.
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Eric Sahr
KinetX, Inc.
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Andrew Liounis
NASA Goddard Space Flight Center
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Michael Moreau
NASA Goddard Space Flight Center
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Brent Bos
NASA Goddard Space Flight Center
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Carl Hergenrother
University of Arizona
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Dante Lauretta
University of Arizona
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Abstract

On January 6, 2019, OSIRIS-REx first observed particles ejecting from the surface of near-Earth asteroid (101955) Bennu. This ejection event was unexpected and was only captured by chance in a pair of optical navigation images taken by the OSIRIS-REx NavCam 1 imager. With this limited dataset of only two observations per ejected particle, traditional orbit determination to reconstruct the particles’ trajectories was not possible. Therefore, a new technique was developed for reconstruction of the ejection event based on some simplifying assumptions that the particles all ejected from the same location at the same time and that their velocities remained constant after ejection (a reasonable approximation for fast-moving particles given Bennu’s weak gravity). This technique was then applied to reconstruct those particle events observed by the OSIRIS-REx spacecraft at Bennu from January 2019 through June 2019 by Pelgrift et al. (2020). We present a follow-on to that work that applies the same technique to reconstruct the particle ejection events observed in the latter half of OSIRIS-REx proximity operations at Bennu, covering the time span from July 2019 through July 2020. We reconstructed 8 additional events, bringing the total number of Bennu particle ejection events reconstructed using this technique to 19. The new dataset includes the largest event observed to-date, with over 350 individual tracked particles. The new events have particle ejection velocities similar to the previous events, ranging from 5 cm/s to 1.8 m/s. In the full dataset of 19 events, we observed the same trend noted in the original work where the majority of events were estimated to have occurred at mid-latitudes and afternoon local solar times (LST). Reference: Pelgrift, J. Y., Lessac-Chenen, E. J., Adam, C. D., Leonard, J. M., Nelson, D. S., McCarthy, L., et al. (2020). Reconstruction of Bennu particle events from sparse data. Earth and Space Science. 7, e2019EA000938. https://doi.org/10.1029/2019EA000938