Asteroid Photometry

Li, Jian‐Yang; Helfenstein, P.; Buratti, B. J.; Takir, D.; Clark, B. E.

doi:10.2458/azu_uapress_9780816532131-ch007

Cited by 31 publications

(30 citation statements)

References 129 publications

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“…These quantities confirm the previous measurements of spectral slopes reported in Capaccioni et al (2015). Phase reddening can be interpreted as an effect of multiple scattering (Cuzzi et al 2002;Li et al 2015), which is relatively stronger at large phase angles for bodies with a backscattering phase function, by stretching albedo differences at different wavelengths. This explanation is reasonable for surfaces with moderate to large w, where multiple scattering plays an important role, but may be not sufficient in the case of dark surfaces, where single scattering is the dominant process.…”

Section: Spectral Slopes and Phase Reddeningsupporting

confidence: 90%

Photometric properties of comet 67P/Churyumov-Gerasimenko from VIRTIS-M onboard Rosetta

Ciarniello

Capaccioni

Filacchione

et al. 2015

A&A

104

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Aims. We investigate the nucleus photometric properties of the comet 67P/Churyumov-Gerasimenko as observed by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard the Rosetta spacecraft. Both full-disk and disk-resolved images of the comet have been analyzed, deriving light and phase curves as well as a photometric reduction of the radiance factor (I/F) to single scattering albedo (SSA) in the 0.4-3.5 μm range. Methods. Hyperspectral cubes from VIRTIS were calibrated and corrected for instrumental artifacts. We computed integrated fluxes from full-disk acquisitions to derive nucleus light curves and phase curves at low phase angles (1.2• < α < 14.9• ). Disk-resolved observations in the phase angle range 27.2• < α < 111.5• were reduced to SSA by means of a simplified Hapke model, deriving average spectrophotometric properties of the surface and producing SSA maps at different wavelengths. Spectral phase reddening in the visible (VIS) and infrared (IR) ranges was measured. Finally, full-disk and disk-resolved data were used together to derive a phase curve of the nucleus in the 1.2• < α < 111.5• range. Results. We measure an asymmetric double-peaked light curve that is due to the elongated shape of the nucleus. The average SSA albedo shows a reddish spectrum with a strong absorption feature centered at 3.2 μm, while the surface exhibits a backscattering behavior. The derived geometric albedo is A geo = 0.062 ± 0.002 at 0.55 μm, indicating a very dark surface. Phase reddening is significant both in the VIS and IR ranges, and we report spectral slopes of 0.20/kÅ and 0.033/kÅ, respectively, after applying photometric reduction. SSA maps indicate that Hapi and Imothep regions are the brightest in the VIS, with the former showing a bluer spectrum with respect to the rest of the surface. The phase curve of the nucleus shows a strong opposition effect, with β = 0.077 ± 0.002 for α < 15• .

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Section: Spectral Slopes and Phase Reddeningsupporting

confidence: 90%

Photometric properties of comet 67P/Churyumov-Gerasimenko from VIRTIS-M onboard Rosetta

Ciarniello

Capaccioni

Filacchione

et al. 2015

A&A

104

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“…10a, b), similarly to what is observed by Li et al (2016b), with an increment of 4.6 × 10 . This behavior, indicated as "phase reddening", is common for asteroids (see Li et al 2015, and references therein) and airless bodies in general, such as comets , icy satellites (Cuzzi et al 2002;Ciarniello et al 2011;Filacchione et al 2012), and planetary rings Ciarniello et al 2016). Moreover, it has been observed in laboratory measurements and light-scattering simulations from Schröder et al (2014).…”

Section: Spectral Slopes and Phase Reddeningmentioning

confidence: 95%

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

Ciarniello

Sanctis

Ammannito

et al. 2017

A&A

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Aims. We present a study of the spectrophotometric properties of dwarf planet Ceres in the visual-to-infrared (VIS-IR) spectral range by means of hyper-spectral images acquired by the VIR imaging spectrometer on board the NASA Dawn mission. Methods. Disk-resolved observations with a phase angle within the 7• < α < 132• interval were used to characterize Ceres' phase curve in the 0.465-4.05 µm spectral range. Hapke's model was applied to perform the photometric correction of the dataset to standard observation geometry at VIS-IR wavelength, allowing us to produce albedo and color maps of the surface. The V-band magnitude phase function of Ceres has been computed from disk-resolved images and fitted with both the classical linear model and H-G formalism.Results. The single-scattering albedo and the asymmetry parameter at 0.55 µm are w = 0.14 ± 0.02 and ξ = −0.11 ± 0.08, respectively (two-lobe Henyey-Greenstein phase function); at the same wavelength, Ceres' geometric albedo as derived from our modeling is 0.094 ± 0.007; the roughness parameter isθ = 29• ± 6• . Albedo maps indicate small variability on a global scale with an average reflectance at standard geometry of 0.034 ± 0.003. Nonetheless, isolated areas such as the Occator bright spots, Haulani, and Oxo show an albedo much higher than average. We measure a significant spectral phase reddening, and the average spectral slope of Ceres' surface after photometric correction is 1.1% kÅ • gives H = 3.14 ± 0.04 and G = 0.10 ± 0.04, while the classical linear model provides V(1, 1, 0 • ) = 3.48 ± 0.03 and β = 0.036 ± 0.002. The comparison of our results with spectrophotometric properties of other minor bodies indicates that Ceres has a less back-scattering phase function and a slightly higher albedo than comets and C-type objects. However, the latter represents the closest match in the usual asteroid taxonomy.

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“…During the Approach and Preliminary Survey phases of the mission (August to December 2018), we measured Bennu's resolved reflectance (I/F) in MapCam's five filters across a wide range of phase angles (0.7° to 90°). Fitting these data to an exponential phase function [6] yields a low global average geometric albedo of 4.4% ± 0.2% at 550 nm (Fig. 1a).…”

Section: Global Average Propertiesmentioning

confidence: 99%

Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis

et al. 2019

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Christensen, P. R.; Drouet d'Aubigny, C. Y.; Hamilton, V. E.; Reuter, D. C.; Rizk, B.; Simon, A. A.; Asphaug, E.; Bandfield, J. L.; Barnouin, O. S.; Barucci, M. A.; Bierhaus, E. B.; Binzel, R. P.; Bottke, W. F.; Bowles, N. E.; Campins, H.; Clark, B. C.; Clark, B. E.; Connolly, H. C.; Daly, M. G.; Leon, J. de; Delbo', M.; Deshapriya, J. D. P.; Elder, C. M.; Fornasier, S.; Hergenrother, C. W.; Howell, E. S.; Jawin, E. R.; Kaplan, H. H.; Kareta, T. R.; Le Corre, L.; Li, J.-Y.; Licandro, J.; Lim, L. F.; Michel, P.; Molaro, J.; Nolan, M. C.; Pajola, M.; Popescu, M.; Garcia, J. L. Rizos; Ryan, A.; Schwartz, S. R.; Shultz, N.; Siegler, M. A.; Smith, P. H.; Tatsumi, E.; Thomas, C. A.; Walsh, K. J.; Wolner, C. W. V.; Zou, X.-D. and Lauretta, D. S. (2019). Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis. Nature Astronomy, 3 pp. 341-351. For guidance on citations see FAQs.Length of main text: 2956 words Length of methods: 3605 words Length of legends: 565 words Number of references: 53 main text, 69 including methods and supplementary information (refs 67 to 69 are cited in the SI only) , we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micron-scale particles).

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Asteroid Photometry

Cited by 31 publications

References 129 publications

Photometric properties of comet 67P/Churyumov-Gerasimenko from VIRTIS-M onboard Rosetta

Photometric properties of comet 67P/Churyumov-Gerasimenko from VIRTIS-M onboard Rosetta

Spectrophotometric properties of dwarf planet Ceres from the VIR spectrometer on board the Dawn mission

Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx imaging and thermal analysis

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