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Using Hapke Modelling to Probe Near-Earth Asteroid Phase Curves

Presentation #523.02 in the session Observing and Modeling NEO Properties (iPosters).

Published onOct 20, 2022
Using Hapke Modelling to Probe Near-Earth Asteroid Phase Curves

Phase curves of asteroids are often interpreted within the context of the properties of the materials present on asteroid surfaces. However, the phase curve of a non-spherical object that undergoes changes in viewing geometry can vary between and during apparitions from the phase curve expected from a spherical body with the same surface material. This means that model parameters used in fits to phase curve data, such as in the HG system [1], can vary depending on the sampling of the observations used to construct the phase curve. We have developed a code, using the Hapke photometric model [2], to estimate the systematic uncertainty introduced into asteroid phase curves due to these changes in aspect [3]. The significance of this effect is shown by re-analysing, using our code, the uncertainties of previously published phase curves for the asteroids (8014) 1990 MF and (19764) 2000 NF5 [4]. The aspect-related uncertainties on the absolute magnitudes are on average 4.5 times higher than the statistical fit uncertainties for these two objects. The propagation of this systematic uncertainty can heavily influence thermal modelling results. A greater than two-fold increase in the uncertainty of the NEATM-derived geometric albedo for (19764) 2000 NF5 is computed. The addition of aspect uncertainty into phase curve derived brightness predictions, that are used to estimate reflected flux contributions in the infrared transition region, can lead to an increase in the percentage uncertainties on these estimations from a few percent to a few tens of percent. We are also using Hapke modelling of phase curves to probe detections of activity from asteroids such as (3200) Phaethon, to investigate the possibility that aspect effects could lead to errors in estimates of excess brightness for these ‘active asteroids’. We are evaluating any potential biases this may introduce into calculations of the dust contribution to the Geminid meteor stream by the activity of (3200) Phaethon.

[1] Bowell et al., 1989, in Asteroids II, 524

[2] Hapke, 2012, Theory of Reflectance and Emittance Spectroscopy. Cambridge Univ. Press, Cambridge

[3] Jackson et al., 2022, MNRAS, 513, 3076

[4] Jackson et al., 2021, PASP, 133, 075003

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