干旱区生态环境知识资源中心

HAYABUSA is the first spacecraft ever to land on and lift off from any celestial body other than the moon. The mission, which returned asteroid samples to the Earth while overcoming various technical hurdles, ended on 2010 June 13, with the planned atmospheric re-entry. In order to safely deliver the sample return capsule, the HAYABUSA spacecraft ended its 7-year journey in a brilliant "artificial fireball" over the Australian desert. Spectroscopic observation was carried out in the near-ultraviolet and visible wavelengths between 3000 angstrom and 7500 angstrom at 3-20 angstrom resolution. Approximately 100 atomic lines such as Fe I, Mg I, Na I, Al I, Cr I, Mn I, Ni I, Ti I, Li I, Zn I, OI, and NI were identified from the spacecraft. Exotic atoms such as Cu I, Mo I, Xe I and Hg I were also detected. A strong Li I line (6708 angstrom) at a height of similar to 55 km originated from the onboard Li-Ion batteries. The FeO molecule bands at a height of 63 km were probably formed in the wake of the spacecraft. The effective excitation temperature as determined from the atomic lines varied from 4500 K to 6000 K. The observed number density of Fe I was about 10 times more abundant than Mg I after the spacecraft explosion. N-2(+) (l(-)) bands from a shock layer and CN violet bands from the sample return capsule’s ablating heat shield were dominant molecular bands in the near-ultraviolet region of 3000 4000 angstrom. OH(A X) band was likely to exist around 3092 angstrom. A strong shock layer from the HAYABUSA spacecraft was rapidly formed at heights between 93 km and 83 km, which was confirmed by detection of N-2(+) (l(-)) bands with a vibration temperature of similar to 13000K. Gray-body temperature of the capsule at a height of similar to 42 km was estimated to be similar to 2437 K which is matched to a theoretical prediction. The final message of the HAYABUSA spacecraft and its sample return capsule are discussed through our spectroscopy.