Development of an optical device (Field Stacker) for achieving accurate photometry in ground-based mid-infrared observations
Development of an optical device (Field Stacker) for achieving accurate photometry in ground-based mid-infrared observations
复制标题
开发用于在地面中红外观测中实现精确测光的光学装置（Field Stacker）
DOI：
10.1117/12.2231283
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M. S. et al.
中科院分区：
文献类型：
--
作者：
Uchiyama;M. S. et al.
大气透过率的强时变性是中红外波段地面监测的关键问题。为了克服这个问题，一种名为“现场堆垛机”的新设备已经开发出来。它是一种将望远镜FoV中的两个离散场联合收割机组合成单个场并将其馈送到相机中的光学装置。它使我们能够同时观测科学目标和参考星星，并在实时定标的基础上大大提高测光精度。为了实际实现高精度测光，应精确调整视场叠加器中反射镜的倾斜度。通过简单的几何计算，估计每个拾取镜的可接受的失调误差< 0.0085度。实验室实际测得的倾斜误差基本满足这一要求。大气中水蒸气的空间变化是精确测光的另一个问题。在简单大气结构模型的基础上，利用红外背景辐射的时间变化估计了大气红外背景辐射的空间变化。在望远镜FoV（Φ25弧分）内，水蒸气的估计变化为0.00036 mm，这表明即使在31和37 μm处，它也不会显著影响测光精度。根据全天红外星表检查参考星的数量密度，以估计场叠加器的可用性。在9和18 μm处的估计可用性分别为99.8%和58.8%。
Strong time variation of atmospheric transmittance is a crucial problem for monitoring observations at mid- infrared wavelengths from the ground. To overcome this problem, a new device called "Field Stacker" has been developed. It is an optical device to combine two discrete fields in the telescope FoV into a single field and feed it in the camera. It enables us to observe a science target and a reference star simultaneously, and improve the photometric accuracy dramatically based on real-time calibration. To practically achieve highly accurate photometry, the tilt of the mirrors in the Field Stacker should be accurately adjusted. Acceptable error of the misalignment of each pick-up mirror is estimated to be < 0.0085 deg from a simple geometric calculation. The actual tilt error measured in the laboratory almost met this requirement. Spatial variation of the water vapor in the atmosphere is another concern for the accurate photometry. Assuming a simple model of the atmospheric structure, the spatial variation was estimated from time variation of infrared background radiation. The estimated variation of the water vapor was 0.00036 mm within the telescope FoV (Φ25 arc- minutes), suggesting that it does not significantly affect the photometric accuracy even at 31 and 37 μm. Number density of reference stars was examined based on all-sky infrared catalogues to estimate the availability of the Field Stacker. The estimated availabilities at 9 and 18 μm were 99.8% and 58.8%, respectively.