Photometry of asteroid (101955) Bennu with OVIRS on OSIRIS-REx

Zou, Xiao-Duan; Li, Jian-Yang; Clark, Beth E.; Golish, Dathon R.; Ferrone, Salvatore; Simon, Amy A.; Reuter, Dennis C.; Domingue, Deborah L.; Kaplan, Hannah; Barucci, Maria Antonietta; Fornasier, Sonia; Praet, Alice; Hasselmann, Pedro Henrique; Bennett, Carina A.; Cloutis, Edward A.; Tatsumi, Eri; DellaGiustina, Daniella N.; Lauretta, Dante S.
Bibliographical reference

Icarus

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4
2021
Journal
Number of authors
18
IAC number of authors
1
Citations
12
Refereed citations
12
Description
NASA's OSIRIS-REx spacecraft arrived at its sampling target, asteroid (101955) Bennu, in December 2018 and started a series of global observation campaigns. Here we investigate the global photometric properties of Bennu as observed by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS) over the time period December 9, 2018, to September 26, 2019. In this study we used observations obtained over wavelengths ranging from 0.4 to 3.7 μm, with a solar phase angle range of 5.3° to 132.6°. Our aim is to characterize the global average disk-resolved photometric properties of Bennu with multiple models. The best-fit model is a McEwen model with an exponential phase function and an exponential polynomial partition function. We use this model to correct the OVIRS spectra of Bennu to a standard reference viewing and illumination geometry at visible to infrared wavelengths for the purposes of global spectral mapping. We derive a bolometric Bond albedo map in which Bennu's surface values range from 0.021 to 0.027. We find a phase reddening effect, and our model is effective at removing this phase reddening. Our average model albedo shows a blueish spectrum with a > 10% absorption feature centered at 2.74 μm. Of all comparisons with previously visited asteroids and comets, only 28P/Neujmin, 2P/Encke, and (162173) Ryugu are darker than Bennu. We find that Bennu is a few percent brighter than Ryugu in the wavelengths respectively observed by the OSIRIS-REx and Hayabusa2 missions (from 0.48 to 0.86 μm). We also compare our spectroscopic photometry of Bennu with the OSIRIS-REx imaging photometry and with ground-based predictions.
Related projects
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Minor Bodies of the Solar System

This project studies the physical and compositional properties of the so-called minor bodies of the Solar System, that includes asteroids, icy objects, and comets. Of special interest are the trans-neptunian objects (TNOs), including those considered the most distant objects detected so far (Extreme-TNOs or ETNOs); the comets and the comet-asteroid

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León Cruz