Seeing-limited Imaging Sky Surveys—Small versus Large Telescopes
Seeing-limited Imaging Sky Surveys—Small versus Large Telescopes
复制标题
视域有限的成像巡天——小型与大型望远镜
DOI：
--
复制
发表时间：
2020
影响因子：
3.5
通讯作者：
S. Ben
中科院分区：
文献类型：
--
作者：
E. Ofek;S. Ben
通常，大型望远镜的建造和运营成本的增长速度快于其收集区域的增长速度。这减缓了科学进步，使得增加望远镜尺寸变得昂贵且复杂。我们回顾了这样一个论点，即代表成像巡天望远镜能力并捕获广泛科学目标的一个指标是望远镜的抓地力，即每单位时间可检测到标准烛光的空间体积。我们证明，在均匀欧几里得宇宙中，在背景噪声主导的极限下，把握为： ∝ Ω A eff 3 / 4 σ − 3 / 2 t E 3 / 4 / ( t E + t D ) ，其中 Ω 是望远镜视场，Aeff 是望远镜的有效采集面积，σ 是仪器或大气视宁度或像素大小（以占主导地位者为准），tE是曝光时间，tD 是死区时间。在这种情况下，最佳曝光时间是死区时间的三倍。我们还引入了一个称为信息内容掌握的相关指标，它总结了望远镜每单位时间观测到的所有源的方差。我们表明，在背景噪声主导的情况下，信息内容的掌握程度与掌握程度相同。对于以视宁为主的天空观测，在抓握力、集光率或收集区域优化方面，最近的技术进步使得建造多个小型望远镜比建造具有类似抓握力或集光率的单个大型望远镜更具成本效益。这些关键进步包括具有 ≲4 μm 像素的大画幅背照式 CMOS 探测器的可用性，在给定小型快速望远镜的典型焦距的情况下，非常适合采样标准视宁条件。我们还讨论了使用多个小型望远镜进行光谱和强度干涉仪的可能性。我们认为，如果使用多个小型望远镜实现具有成本效益的宽视场成像和多目标光谱仪的所有障碍都被消除，那么建造新的以视宁为主的单一大口径（≳1 m）可见光望远镜的动力将被削弱。这些想法催生了目前正在建设中的大型阵列巡天望远镜的概念。
Typically large telescope construction and operation costs scale up faster than their collecting area. This slows scientific progress, making it expensive and complicated to increase telescope size. We review the argument that a metric that represents the capability of an imaging survey telescopes, and that captures a wide range of science objectives, is the telescope grasp—the amount of volume of space in which a standard candle is detectable per unit time. We show that in a homogeneous Euclidean universe, and in the background-noise dominated limit, the grasp is: ∝ Ω A eff 3 / 4 σ − 3 / 2 t E 3 / 4 / ( t E + t D ) , where Ω is the telescope field of view, Aeff is the effective collecting area of the telescope, σ is the instrumental or atmospheric seeing or the pixel-size, whichever dominates, tE is the exposure time, and tD is the dead time. In this case, the optimal exposure time is three times the dead time. We also introduce a related metric we call the information-content grasp, which summarizes the variance of all sources observed by the telescope per unit time. We show that, in the background-noise dominated regime, the information-content grasp scales like the grasp. For seeing-dominated sky surveys, in terms of grasp, étendue, or collecting-area optimization, recent technological advancements make it more cost effective to construct multiple small telescopes rather than a single large telescope with a similar grasp or étendue. Among these key advancements are the availability of large-format back-side illuminated CMOS detectors with ≲4 μm pixels, well suited to sample standard seeing conditions given typical focal lengths of small fast telescopes. We also discuss the possible use of multiple small telescopes for spectroscopy and intensity interferometers. We argue that if all the obstacles to implementing cost-effective wide-field imaging and multi-object spectrographs using multiple small telescopes are removed, then the motivation to build new single large-aperture (≳1 m) visible-light telescopes which are seeing-dominated, will be weakened. These ideas have led to the concept of the, currently under construction, Large-Array Survey Telescope.
DOI：
10.1088/1538-3873/aaecbe
发表时间：
2019-01-01
影响因子：
3.5
作者：
Bellm, Eric C.;Kulkarni, Shrinivas R.;Zolkower, Jeffry
通讯作者：
Zolkower, Jeffry
DOI：
10.1088/1538-3873/ab0c2a
发表时间：
2019-06-01
影响因子：
3.5
作者：
Bellm, Eric C.;Kulkarni, Shrinivas R.;Ye, Quan-Zhi
通讯作者：
Ye, Quan-Zhi