* Astronomy

It was confirmed that Hayabusa has reached a trajectory that will make it pass 750 thousand kilometres from the Earth.

It is two times as distant as to the Moon. Ion engines aboard have worked well since last week, and the spacecraft almost precisely has been guided along the target line shown. Around at the end of this month, Hayabusa will be on the orbit that passes through even within Moon's distance. Hayabusa will pass at two times as far distance as to the Moon
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Title: The Hayabusa Spacecraft Asteroid Multi-Band Imaging Camera: AMICA
Authors: Masateru Ishiguro, Ryosuke Nakamura, David J. Tholen, Naru Hirata, Hirohide Demura, Etsuko Nemoto, Akiko M. Nakamura, Yuta Higuchi, Akito Sogame, Aya Yamamoto, Kohei Kitazato, Yasuhiro Yokota, Takashi Kubota, Tatsuaki Hashimoto, Jun Saito

The Hayabusa Spacecraft Asteroid Multiband Imaging Camera (AMICA) has acquired more than 1400 multispectral and high-resolution images of its target asteroid, 25143 Itokawa, since late August 2005. In this paper, we summarize the design and performance of AMICA. In addition, we describe the calibration methods, assumptions, and models, based on measurements. Major calibration steps include corrections for linearity and modelling and subtraction of bias, dark current, read-out smear, and pixel-to-pixel responsivity variations. AMICA v-band data were calibrated to radiance using in-flight stellar observations. The other band data were calibrated to reflectance by comparing them to ground-based observations to avoid the uncertainty of the solar irradiation in those bands. We found that the AMICA signal was linear with respect to the input signal to an accuracy of << 1% when the signal level was < 3800 DN. We verified that the absolute radiance calibration of the AMICA v-band (0.55 micron) was accurate to 4% or less, the accuracy of the disk-integrated spectra with respect to the AMICA v-band was about 1%, and the pixel-to-pixel responsivity (flatfield) variation was 3% or less. The uncertainty in background zero-level was 5 DN. From wide-band observations of star clusters, we found that the AMICA optics have an effective focal length of 120.80 \pm 0.03 mm, yielding a field-of-view (FOV) of 5.83 deg x 5.69 deg. The resulting geometric distortion model was accurate to within a third of a pixel. We demonstrated an image-restoration technique using the point-spread functions of stars, and confirmed that the technique functions well in all loss-less images. An artefact not corrected by this calibration is scattered light associated with bright disks in the FOV.

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The Japan Aerospace Exploration Agency (JAXA) has been studying measures to deal with the anomaly detected in one of the ion engines aboard the Asteroid Explorer "HAYABUSA" as reported on November 9, 2009. As a result, the project team has come up with a recovery operation plan, and the project decided to resume the operations, while carefully watching the status of the ion engines.
JAXA has been studying the characteristics of the neutralisers and the ion sources. During the study, enough thrust is found available for the rest of the cruise, when the neutraliser of the engine-A is combined with the ion source of the engine-B.
While the operation still needs monitored carefully, the project team has concluded the spacecraft can maintain the current return cruise schedule back to the earth around June of 2010, if the new engines configuration continues to work as planned.

Source JAXA

On November 4th (Wed., Japan Standard Time), the Japan Aerospace Exploration Agency identified that one of the main ion engines (Thruster D) aboard the Asteroid Explorer "HAYABUSA" had autonomously stopped detecting a high neutraliser voltage owing to degradation. The HAYABUSA was during the second propulsion period in its return cruise back to the Earth in June 2010. Since the anomaly was identified, the project team has been trying to restart the engine while investigation of the causes; however, the engine has not been restarted yet as of today.
JAXA is currently under diagnostic investigation of the ion engines system aboard the HAYABUSA and trying to build an alternative sequence that helps the HAYABUSA return back to the Earth safely. JAXA will inform you of the update as soon as available.

Source JAXA