Chiba Institute of Technology
Kobe University
The Graduate University for Advanced Studies (SOKENDAI)
Chiba Institute of Technology
Photocoding
Kochi University
Kobe University
Japan's asteroid probe Hayabusa2 equips Deployable Camera 3 (DCAM3) that will observe an impact experiment using Small Carry-on Impactor (SCI) on asteroid 162137 Ryugu (1999 JU3). DCAM3 has two cameras, DCAM3-A (a monitor camera) and DCAM3-D (a scientific camera). DCAM3-D, especially, aims to understand impact phenomena on asteroids through observing the trajectory of SCI and the shape of the ejecta curtain created by the impact. The imaging performance of DCAM3-D might degrade by coloring of the lenses that is due to the radiation of up to 11 krad for a 1-mm aluminum shielding during the 6.5-years cruise of Hayabsa2. Since the two lens materials Ohara Inc. S-TIH6 and S-BAM12 among the five lens materials for the DCAM3-D optics have no data of the optical transmission dependence on the radiation total dose, we conducted gamma-ray irradiation tests for them. Samples were irradiated up to 10 krad. The relative reduction of transmission between 450 to 750 nm that are the wavelength range for DCAM3-D was maximum at 450 nm and less than 3.7% for S-TIH6 and 5.5% for S-BAM12. The reduction is getting less at longer wavelength. These transmission performances were recovered modestly with the time after irradiation. The degradation of the received signal determined by weighted integration with the solar spectrum and the spectral response of the CMOS sensor used in DCAM3-D is 10.4%, which satisfies the allowable degradation of 20% that is required for the observation of SCI with S/N > 5. These results indicate that S-TIH6 and S-BAM12 are applicable for the optical system of DCAM3-D.
内容記述
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内容記述（英）
Physical characteristics: Original contains color illustrations
Hayabusa2分離カメラ用硝材のガンマ線照射試験
AA1530045000.pdf
(1.49MB)
