Thermophysical Modeling of NEOWISE Observations of DESTINY+ Targets Phaethon and 2005 UD

Thermophysical models allow for improved constraints on the physical and thermal surface properties of asteroids beyond what can be inferred from more simple thermal modeling, provided that a sufficient number of observations is available. We present thermophysical modeling results of observations from the Near-Earth Object WISE (NEOWISE) mission for two near-Earth asteroids which are the targets of the DESTINY⁺ flyby mission: (3200) Phaethon and (155140) 2005 UD. Our model assumes a rotating, cratered, spherical surface, and employs a Monte Carlo Markov Chain to explore the multidimensional parameter space of the fit. We find an effective spherical diameter for Phaethon of {4.6}_-0.3^+0.2 km, a geometric albedo of p _V = 0.16 ± 0.02, and a thermal inertia Γ = 880 {}_-330⁺⁵⁸⁰, using five epochs of NEOWISE observations. The best model fit for (155140) 2005 UD was less well constrained due to only having two NEOWISE observation epochs, giving a diameter of 1.2 ± 0.4 km and a geometric albedo of p _V = 0.14 ± 0.09.