HAYABUSA'S SAMPLING SITE COORDINATES ON
ITOKAWA: CONNECTING IN-SITU DATA AND
RETURNED SAMPLES .
H. Yano1 and S. Aida2. 1JAXA/ISAS, E-mail: yahoo.hajime@jaxa.jp. 2 DLR German Space Operations Center.
Introduction: Hayabusa performed two touchdown (TD) operations for sample collection at the “MUSES-C Regio” smoothterrain of Itokawa on November 19th and 25th, 2005 [1]. Although the emergency descent abort for TD1 and the software
problem for TD2 prohibited Hayabusa to shoot Ta projectiles
onto the asteroid surface, sub-mm to micron-sized asteroidal
samples were collected in two separated chambers of the sample
catcher, allowing to distinguish these samples from two different
locations, except the smallest end members that might be able tomove between the chambers. Thus estimates of these samplingsites will help to combine statistical characteristics of collected
samples with geological ground truth at the MUSES-C Regio.
Reconstructing the Descent Trajectories with HK Data:
The two sampling sites were estimated by reconstructing the orbit/drift motions of Haybusa’s HK data, much more comprehensively than a previous, preliminary attempt [2]. During the initial phase of the decent operation, the spacecraft position relative
to the asteroid was determined by the "GCP Navigation" on theasteroid surface as landmarks [3, 4] . In this analysis, the following sensor data were integrated: Attitude Sensor, Range Rate,
LIDAR, LRF-S1, LRF-S2, and ONC-W1,2. In addition, the Itokawa 3D model was used as a reference of the surface gradient.
TD1 Site Estimate: At 20:40 UTC, the flight sequence wasinterrupted due to an obstacle detection near the target marker
location, then the spacecraft was in drifted motion with the initialvelocity. The range data showed that the spacecraft bounced
twice after free fall. After the drift motion of ~50 minutes, Hayabusa landed near Itokawa’s south pole, at the latitude: -82 ~ -71
deg. and the longitude: +323 ~ +324 deg. There remain someuncertainties in the drift trace but the surface gradient at the estimated TD site gives a good agreement with the final spacecraft
attitude: ~25 deg. inclined from the Earth-Itokawa line.
TD2 Site Estimate: At the final decent phase of the TD2 onNovember 25th, the spacecraft attitude was aligned with regard to
the surface, and the landing/sampling was performed successfullyat ~22:07 UTC. The resulting trace is not as clear as the TD1 but
the best estimated sampling site for the TD2 is near the equator at
the latitude -10 ~ -1 and the longitude +331 ~ +333 deg.
Implications to Collected Samples: The TD1 region is in
the middle of the smooth terrain and close to the south pole vortex where global regolith gravels can migrate and accumulate
effectively [5]. Thus spectrally matured, eroded microparticlesmust exist. In contract, the TD2 equatorial region is right next tothe “Shirakami Mountain”, one of the steepest geopotential areason Itokawa. Thus regolith could be admixture between matured,
rounded components and spectrally younger, sharper-edged components. This is consistent with the early reports about space
weathering and 3D shapes of the samples from this region [6, 7].
References: [1] H. Yano, et al. 2006, Science, 312, pp.13501353. [2] T. Kubota, et al., 2006, Proc. AIAA/AAS Astrodynamics
Conf.. [3] S. Aida, et al., 2006, 2006 IAC Proc., IAC-06-E2.2.03.
[4] J. Kawaguchi, et al, 2006, Proc. AIAA/AAS Astrodynamics
Conf.. [5] H. Miyamoto, et al.: 2007, Science, 316, pp.10111014. [6] T. Noguchi, et al., 2011, Science, 333, pp. 1121-1125.
[7] A. Tsuchiyama, et al., 2011, Science, 333, pp. 1125-1128.