Scattered Light Correction of HAYABUSA/AMICA Data and Quantitative Spectral Comparisons of Itokawa

Abstract

The Hayabusa spacecraft rendezvoused with its target asteroid 25143 Itokawa in 2005 and brought an asteroidal sample back to the Earth in 2010. The onboard camera, AMICA, took more than 1400 images of Itokawa during the rendezvous phase. It was reported that the AMICA images were severely contaminated by light scatter inside the optics. The effect made it difficult to produce the color maps at longer wavelengths (>800 nm). In this paper, we demonstrate a method to subtract the scattered light by investigating the dim halos of Itokawa and the Moon taken by AMICA during the inflight operation. As the result, we found that the overall data reduction scheme including the scattered light correction enables to recognize ~3% regional differences in the relative reflectance spectra of Itokawa. We confirmed that the color variation in Itokawa was largely attributed to space weathering.