1 Astrodynamics Science about Itokawa, Gravity and Ephemeris

[Abstract] Hayabusa was moving near Asteroid Itokawa for about three months in 2005. Using tracking and navigation data such as range, Doppler, distance from the asteroid, and optical images taken by navigation cameras, we estimated the mass of Itokawa for several orbital phases. The results are consistent in their error ranges. The estimated mass of Itokawa is 3.51 ±0.105 (1010 kg), from which the density of Itokawa is derived as 1.9 ±0.13 (g/cm3). This is one of the important characteristics to understand the nature of Itokawa. We are also trying to investigate the accuracy of the ephemeris of this asteroid. I