[P-CG24] 宇宙・惑星探査の将来計画および関連する機器開発の展望

[PCG24-P01] MMX搭載広角分光カメラOROCHIの迷光解析と改善手法

*布施 綾太¹、塩谷 圭吾²、亀田 真吾³、加藤 博基³、尾崎 正伸²、石橋 高⁴、神山 徹⁵、阿部 新助¹ (1.日本大学、2.宇宙航空研究開発機構、3.立教大学、4.千葉工業大学、5.国立研究開発法人産業技術総合研究所)

キーワード：MMX、カメラ、迷光

The Martian Moons eXploration (MMX) is planned to survey two Martian moons, Phobos and Deimos, and return samples from Phobos. MMX will be launched in 2024 and carries several scientific instruments. The OROCHI (Optical RadiOmeter composed of Chromatic Imagers) is wide-angle multiband camera which consists of 7 cameras with bandpass filter in specific visible wavelength (e.g., 730nm; Phyllosilicate feature). The specification is 12.22 mm/F4, 3296(H) x 2472(V) pix, 73(H) x 58(V) deg, 20 m/pix@20km, MTF@Nyquist>0.3. The OROCHI is aimed to constrain the global surface composition and physical structure of Phobos. In our scientific goals, Signal-to-Noise ratio of the OROCHI needs to be S/N > 100 in order to detect faint absorption clearly. Origins of the noise are mainly electrical noise from a CCD sensor and stray light from a optical system, and we focused on the latter. Stray light is generated by reflected lights at sensor, filter, and lens surfaces, therefore, the S/N ratio depends on these reflectance. We designed a similar optical system of the OROCHI in software and performed stray light analysis by measuring the reflectance of a sensor candidate and assuming that of filter and lens. Then, we estimated the S/N ratio. Although the S/N did not reach 100 at the beginning of analysis, we could achieve finally over 100 by following approaches; decreasing the reflectance of the filter and lens, keeping the filter away from the sensor, and reducing the number of lenses. In this study, we propose the OROCHI’s optical design, results of stray light analysis, and the improvement method.