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S.M. Lederer (Cal State Univ SB, NASA Johnson Space Center), J.E. Thomas-Osip (Las Campanas Observatory), D.L. Domingue (Johns Hopkins Univ Applied Physics Lab), S.L. Gill (Cal State Univ SB), D.J. Osip (Las Campanas Observatory), F. Vilas (NASA Johnson Space Center), K.S. Jarvis (Lockheed-Martin Space Operations)
In 2004, Asteroid 25143 Itokawa made its final close approach to the Earth prior to its encounter (anticipated in the fall of 2005) with the Japanese spacecraft Hayabusa. At Lowell Observatory, we obtained 9 nights of BVRI broadband photometry with the 1.7 m Perkins Telescope in January and February. During this time, the asteroid reached its minimum phase angle of this apparition of 4 degrees. At Las Campanas Observatory in Chile, we collected 18 nights of UBVRI photometry with the 1.0 m Swope telescope, and 9 nights of JHK photometry with the 2.5 m DuPont telescope in June and July. These data span phase angles ranging from 11 degrees to 90 degrees. Also at Las Campanas, additional BVRI observations taken in January and June with the 6.5 m Magellan telescope extend the BVRI phase angle coverage to include 4 and 130 degrees phase angles (cf. Thomas-Osip et al., this meeting, for detailed multi-wavelength rotational light-curve analysis, and Gill et al., this meeting, for a study on broadband colors).
Here, we report on the rotationally corrected, multi-color phase angle curves of this asteroid, and compare the results from this apparition with the apparition in 2001 (c.f. Lederer et al. Icarus, in press). These data are ideally suited for a Hapke model study to investigate physical properties, such as single particle scattering albedo, and surface roughness. The low phase angle data allow us to investigate the backscattering properties (impossible with the 2001 apparition as the phase angle never dropped below 10 degrees) while the high phase angles (the forward scattering regime) are important for disentangling the effects of surface roughness and the single particle scattering function.
This work was made possible in part by a NASA MUCERPI grant, and the NASA Hayabusa Program.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.