Near-Ultraviolet and Visible Spectroscopy of HAYABUSA Spacecraft Re-Entry

Abstract

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 June 13, 2010, 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 nearultraviolet and visible wavelengths between 3000 and 7500Å at 3 -20Å 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, O I, and N I 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 (6708Å) at a height of ∼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 (1 − ) 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 -4000Å. OH(A-X) band was likely to exist around 3092Å. 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 (1 − ) bands with a vibration temperature of ∼13000 K. Gray-body temperature of the capsule at a height of ∼42 km was estimated to be ∼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.

Superorbital re-entry shock layers: flight and laboratory comparisons

“…Winter et al also report the AUS data and discusses the HDVS1 data [35], and Loehle, Mezger and Fulge's spectra extends into the UV to overlap with AUS, but the spectra are too noisy below 400 nm to provide any useful information [34]. The spectra from Abe et al that overlapped with AUS was uncalibrated at the time of publication, and the visible spectra are not useful for the present work as it focuses on metallic species that come from paint or the spacecraft bus [26]. Higher altitude UV spectra (above 63 km) was predicted numerically to have less CN than N + 2 in the region between 380 and 400 nm, and an overarching peak from Fe and Al [26].…”

“…Hayabusa was launched as the MUSES-C mission on May 9, 2003 and was the third engineering space mission by the Japanese Aerospace Exploration Agency (JAXA) and the Institute of Space and Aeronautical Sciences (ISAS) [26]. Hayabusa, a small vehicle with a nose radius of 200 mm and weight of 16.5 kg, designed the TPS carefully for the extreme entry conditions and to integrate with the structure [27].…”

“…The mission was the first sample return mission to visit an asteroid (25143 Itokawa), return dust samples to Earth for analysis [28], and record high-resolution spectra of the asteroid [29]. Contact with the vehicle was lost after landing on the asteroid in late 2005 and the mission appeared failed until the vehicle re-established contact in early 2007, commencing its return to Earth [26]. The near-ballistic re-entry and landing took place at Woomera, Australia on June 13, 2010, providing a unique opportunity for observation teams to record time-resolved measurements of the radiating shock layer, the capsule surface and the wake including the spacecraft bus, all captured in Figure 2.3.…”

“…The data includes velocity and trajectory calculations correct to within ± 100 m · s −1 and a few hundred metres, respectively [31], total flux measurements across varying wavelength ranges [32], surface temperature measurements [33] [34] and spectra in the UV [5] [26] [35], visible [26] and different sections of the near infrared, to focus on atomic N and O between 700 and 900 nm [4] [35], and atomic N and C between 980 and 1080 nm [36]. The ground-based observation data taken by a team from The University of Queensland was the most important for the current work.…”

“…The spectra from Abe et al that overlapped with AUS was uncalibrated at the time of publication, and the visible spectra are not useful for the present work as it focuses on metallic species that come from paint or the spacecraft bus [26]. Higher altitude UV spectra (above 63 km) was predicted numerically to have less CN than N + 2 in the region between 380 and 400 nm, and an overarching peak from Fe and Al [26]. Buttsworth, Morgan and Jenniskens' data suggests that this will change leading up to and following peak heating, where CN will become dominant and the metallic lines will not feature.…”