K Hiraoka

Publications (2)1.18 Total impact

• Article: An overview of the LIDAR observations of asteroid 25143 Itokawa

  T. Mukai, S. Abe, N. Hirata, R. Nakamura, O.S. Barnouin-Jha, A.F. Cheng, T. Mizuno, K. Hiraoka, T. Honda, H. Demura, R.W. Gaskell, T. Hashimoto, T. Kubota, M. Matsuoka, D.J. Scheeres, M. Yoshikawa
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  ABSTRACT: We present an overview of the laser altimeter(LIDAR) results for asteroid 25143 Itokawa. The trace of a 7 × 12-m elliptical beam spot made it possible to determine the local surface topography with an accuracy of a few meters in altitude, from a home position roughly 7 km above the surface. Sequential detection of the altitude of the spacecraft during two orbital spans of descent for sampling allowed determination of the asteroid mass as 3.58 × 1010 kg ± 5% and 3.54 × 1010 kg ± 6%, which are consistent with the most probable mass estimate of 3.51 × 1010 kg ± 3% given by Fujiwara et al. [Fujiwara, A., Kawaguchi, J., Yeomans, D.K. et al., 2006. The rubble-pile asteroid Itokawa as observed by Hayabusa. Science 312, 1330–1334]. Together with the total volume of the asteroid deduced from a shape model (i.e., 1.84 × 107 m3 ± 3%), this estimate by LIDAR suggests that asteroid Itokawa has a low density of 1.9 g/cm3 ± 9% and a high bulk porosity of about 40%.
  Advances in Space Research 04/2007; 40:187-192. · 1.18 Impact Factor
• Article: An overview of the LIDAR observations of asteroid 25143 Itokawa

  T. Mukai, S. Abe, N. Hirata, R. Nakamura, O. S. Barnouin-Jha, A. F. Cheng, T. Mizuno, K. Hiraoka, T. Honda, Lidar/Hayabusa Team
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  ABSTRACT: The LIght Detection And Ranging instrument LIDAR on the Hayabusa spacecraft of the Japanese asteroid sample return mission has been operated since September 9 UT 2005 near the near-Earth asteroid 25143 Itokawa S-type asteroid A total operation time of LIDAR mostly in the Home Position along the Itokawa-S C-Earth line at about 7 km altitude was 1140 hours until November 25 UT whereas the available data of reflected signal from the asteroid surface were reduced to about 40 of total LIDAR shots due to worse spacecraft pointing caused by reaction wheel failures Although a planned systematic survey on the whole surface of Itokawa by LIDAR footprint of 5x12m from a 7km altitude was cancelled by this worse pointing LIDAR could perform the observations to derive the whole shape of target asteroid its surface local topographic profiles and the internal structure resulting from the gravity measurements We present here the overview of our LIDAR observations and show that asteroid Itokawa is the small asteroid with the mass of 3 58 - 0 18 x 10 10 kg and the resulting low bulk density of 1 95 - 0 14 g cm 3 implies the presence of unusually high porosity of 39 in S-type asteroid
  36:1572.