Optical Properties of (162173) 1999 JU3: In Preparation for the JAXA Hayabusa 2 Sample Return Mission
Abstract
We investigated the magnitudephase relation of (162173) 1999 JU3, a target asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed the International Astronomical Union's HG formalism but found that it fits less well using a single set of parameters. To improve the inadequate fit, we employed two photometric functions: the Shevchenko and Hapke functions. With the Shevchenko function, we found that the magnitudephase relation exhibits linear behavior in a wide phase angle range (α = 5°75°) and shows weak nonlinear opposition brightening at α < 5°, providing a more reliable absolute magnitude of H _{V} = 19.25 ± 0.03. The phase slope (0.039 ± 0.001 mag deg^{1}) and opposition effect amplitude (parameterized by the ratio of intensity at α = 0.°3 to that at α = 5°, I(0.°3)/I(5°) = 1.31 ± 0.05) are consistent with those of typical Ctype asteroids. We also attempted to determine the parameters for the Hapke model, which are applicable for constructing the surface reflectance map with the Hayabusa 2 onboard cameras. Although we could not constrain the full set of Hapke parameters, we obtained possible values, w = 0.041, g = 0.38, B _{0} = 1.43, and h = 0.050, assuming a surface roughness parameter \bar{θ } = 20°. By combining our photometric study with a thermal model of the asteroid, we obtained a geometric albedo of p _{v} = 0.047 ± 0.003, phase integral q = 0.32 ± 0.03, and Bond albedo A _{B} = 0.014 ± 0.002, which are commensurate with the values for common Ctype asteroids.
This work was conducted as part of the activities of the JAXA Hayabusa 2 GroundBased Observation SubGroup.
 Publication:

The Astrophysical Journal
 Pub Date:
 September 2014
 DOI:
 10.1088/0004637X/792/1/74
 arXiv:
 arXiv:1407.5569
 Bibcode:
 2014ApJ...792...74I
 Keywords:

 meteorites;
 meteors;
 meteoroids;
 minor planets;
 asteroids: general;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 27 pages, 4 figure, accepted for publication in the Astrophysical Journal