隼鸟号航天器小行星多波段成像相机：AMICA
The Hayabusa Spacecraft Asteroid Multi-Band Imaging Camera: AMICA
摘要：
隼鸟号航天器小行星多波段成像相机（AMICA）自2005年8月下旬以来已经获得了其目标小行星25143 Itokawa的1400多张多光谱和高分辨率图像。在本文中，我们总结了AMICA的设计和性能。此外，我们描述了校准方法，假设和模型，基于测量。主要的校准步骤包括校正线性度和建模，以及减去偏置、暗电流、读出拖尾和像素间响应度变化。使用飞行中的恒星观测将AMICA v波段数据校准到辐射率。其他波段的数据通过与地面观测数据进行比较，按反射率进行了校准，以避免这些波段太阳辐射的不确定性。我们发现，当信号电平< 3800 DN时，AMICA信号相对于输入信号是线性的，精确度<< 1%。验证结果表明，AMICA v波段（0.55 μ m）绝对辐射定标精度为4%以下，盘积分光谱相对于AMICA v波段的精度约为1%，像元间响应度（平场）变化小于3%，背景零级不确定度为5DN。从星团的宽波段观测中，我们发现AMICA光学系统的有效焦距为120.80 \pm 0.03 mm，产生的视场（FOV）为5.83 deg x 5.69 deg。由此产生的几何失真模型精确到三分之一像素内。我们演示了一种使用恒星的点扩散函数的图像恢复技术，并证实该技术在所有无损图像中都能很好地工作。未通过此校准校正的伪影是与FOV中的亮盘相关联的散射光。
英文摘要：
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 modeling 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 artifact not corrected by this calibration is scattered light associated with bright disks in the FOV.
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