感谢月球勘测轨道飞行器（LRO）和月球轨道器激光高度计（LOLA）团队提供月球数字高程图。作为探索和空间科学网络（NESS）小组的一部分，这项工作得到了美国宇航局太阳系探索研究虚拟研究所合作协议80ARC017M0006的直接支持。

1. 软件设置
<ol><li>首先，转到https://deepblue.lib.umich.edu/data/concern/data_sets/bg257f178?locale=en并下载软件包。此软件仅在 UNIX 环境中进行过测试，但在其他环境中可能无法完全正常工作。此包中的 README 将帮助引导用户浏览所需的其余软件及其用途。</li>
	<li>请确保安装 2.7 或更大的巨蛇。阅读中提供了一个链接。还需要几个常见的巨蛇库，包括麻木，马普洛特利布，pylab，西比，子处理，短暂和日期。</li>
	<li>请确保安装 CASA 4.7.1 或更高。在阅读中提供的链接。</li>
	<li>请确保安装 gcc 4.8.5 或更高。阅读中提供了一个链接。</li>
	<li>请确保安装 SPICE 的 C 工具包。该软件用于对齐不同的天文参考帧，并跟踪行星、卫星和卫星的相对位置。下载此软件的链接也包含在阅读中。<ol>
<li>下载几个内核，其中包含有关天文和月球参考框架的信息，以及月球、地球和太阳的轨道动力学。需要的特定内核与下载地点的链接一起列在 README 中。</li>
	</ol>
</li>
	<li>获取所需的最终先决条件数据：由 LRO LOLA 测量创建的月球表面数字高程模型 （DEMs）。需要的特定文件在阅读中列出并链接。</li>
</ol>2. 创建阵列配置
<ol><li>自定义createArrayConfig.py脚本。<ol>
<li>通过为每个天线提供经度和纬度坐标列表来选择阵列的配置。 注：该脚本目前格式为直径为 10km 的阵列，包含 1024 个元素，32 个手臂，每个组件都有 32 个日志空间间隔天线，使用恒定因子在 0 纬度附近的经度/纬度之间转换。之所以选择该阵列（-1.04°，-0.43°）的选址，是因为它是海拔变化最低（σ = 5.6 米）的 10x10km patch 的中心，靠近月球 ME 框架中的子地球点（0°，0°）。</li>
		<li>更改脚本中的月球路径变量，以反映包含月球表面高程数据的数字高程模型的新下载位置。</li>
	</ol>
</li>
	<li>使用"蟒蛇createArrayConfig.py"运行createArrayConfig.py脚本。这将使用月球数字高程模型解决每个经度和纬度每个天线的海拔问题。将经度、纬度和高程保存到文件中，并打印到屏幕上，便于复制并粘贴到下一个脚本中。制作显示当地月球地形顶部阵列配置的数字（图 1）。</li>
</ol>3. 使用 SPICE 对齐坐标
<ol><li>自定义 eqarr 超时地球.c脚本。<ol>
<li>取上一个脚本的输出、每个天线的经度、纬度和高程，并将它们复制到脚本中的相应列表中，同时用接收器数和相应的坐标更新可变的"numsc"。 注：由于 C 没有动态阵列分配，因此无法在数据中自动灵活读取，因此必须进行手动复制。</li>
		<li>更新包裹中包含的lunar_furnsh.txt，并附上所需帧和临时文件的新路径名称。</li>
		<li>指定要观察的日期集。这将通知 SPICE 内的短暂人员准确跟踪地球和太阳与这些日期的定义阵列的关系。在脚本中，选择 2025 年大约每周发生的 48 个日期。</li>
		<li>指定天空的目标区域，让阵列跟踪和映像。目前，该脚本保存了从月球表面看到的地球的RA Dec，但人们可能很容易只是把静态的RA 12月坐标代替。</li>
	</ol>
</li>
	<li>编译 eqarr 过时.c脚本<ol>
<li>使用脚本顶部注释中的 gcc 命令编译脚本。这将是类似 "gcc eqar 过时间地球.c - o eqarr 过时间地球 - 我 / 家 / 亚历克谢格 / 香料 / 香料 / 包括 / 家庭 / 亚历克谢格 / 香料 / 香料 / lib / cspice. a - lm - std = c99" 。更改路径以反映 cspice 库的位置。</li>
	</ol>
</li>
	<li>运行 eqarr 可执行的时间与 ". / eqarr 时间" 。这应导致每个文件中包含一组变量的多个文件。最重要的是每个天线在J2000坐标中的XYZ位置，以及天空目标区域的右升降（RA和Dec）坐标（目前从月球的角度看是地球的坐标）。输出变量保存为包含所有请求日期数据的.txt文件。</li>
</ol>4. 使用 CASA 模拟阵列响应
<ol><li>自定义LunarEarthPicFreqIntegration.py脚本。<ol>
<li>指定阵列的观测频率以制作图像。这当前设置为 0.75 MHz。</li>
		<li>指定一个CASA兼容的真情图像（或从.fits图像文件创建）与扬斯基/像素值的阵列重建（例如， 图2）。需要更改代码中的常数（res、res1、宽度、弧形）以反映输入真实图像的大小和分辨率。 注：如果使用 SPICE 方法提供 RA Dec 坐标，则可以在此脚本中注释"导入短暂"语句。此库需要使用卡萨-皮普从卡萨-蟒蛇包安装，但 允许跟踪蟒蛇内的其他天文物体。</li>
	</ol>
</li>
	<li>运行LunarEarthPic.py脚本。脚本顶部的评论是有关如何运行脚本的示例。以下命令是有关如何从命令行运行脚本的一个示例： "诺胡普卡萨 - 诺记录器 - 诺格文件 - 诺吉 - 阿格 - c LunarEarthPicFreqIntegration.py - 出迪尔。-相关真实-numSC 1024|三通地球。out和" -numSC 标志用于通知代码正在使用多少天线/接收器，并帮助从包含接收器坐标的.txt文件中解压数据。 注：天线基线矢量，以观测波长（λ）的单位测量，具有长度D λ 和组件（υ，ν，w）= （∆x，∆y，∆z）/λ。然后，管道计算每个天线的可见性或观测到的交叉相关电压。在这里，小视场近似用于计算可见度，遵循汤普森等人的标准公式，在 频率 ν的无限微小带宽。 <img alt="Equation 2" src="/files/ftp_upload/61540/61540equ02.jpg"> 成像目标的天空坐标被视为相位中心，将帧的 z 或 w 轴指向相位中心。（l、m、n）是（U、V、W）坐标系统的方向。被观测源周围的天空亮度图案是我ν（l，m）。光谱通量密度通常呈现在衍生单元 1 Jansky （Jy） = 10~26W/m 2/Hz. 光谱亮度只是 Jy/steradian 表示来自天空特定区域的通量。ν（l，m）是规范化的天线主光束模式，或者它对来自天空中那个点的辐射有多敏感。 此脚本计算适当投影的参考帧中的天线与上一个脚本的坐标输出中的天线分离。然后，它使用方程 2 来计算每对天线的可见性数据。由此产生的可见度存储在 CASA 测量集文件 （.ms） 中的基线旁边。此 MS 文件是此脚本的主要输出。</li>
</ol>5. 成像数据-无噪音和嘈杂
<ol><li>自定义noiseCopies.py脚本。<ol>
<li>设置系统等效通量密度 （SEFD），在脚本中称为 avNoise。SEFD 是一种方便的方式来谈论无线电天线的总噪声，因为它在系统温度和有效区域都结合在一起，并且提供了直接比较信号和噪声的方法。它目前设置为1.38e7扬斯基，这是一个乐观的噪音水平为0.75 MHz。 注：对于低频无线电系统，有三个主要来源的恒定噪声：放大器噪声，准热噪声从自由电子（估计由迈耶-韦尔内特等人。24 是 6.69e4 Jy 在 0.75 Mhz， 使用电短偶极极近似）， 和银河背景辐射从银河系 （估计由诺瓦科 - 布朗25 是 4.18e6 扬斯基在 0.75 MHz 为整个天空， 其中月球阵列将只看到一部分） 。1.38e7 Jy 的这种最佳噪声水平假定放大器噪声主导其他术语。请参阅赫格杜斯等人，了解更详细的讨论。</li>
		<li>将带宽集成到可变的"噪音"行 200 中。设置为500千赫。</li>
		<li>将集成时间设置为可变"噪声"行 200。</li>
	</ol>
</li>
	<li>运行noiseCopies.py脚本与"无胡普卡萨-无记录-诺洛格文件-诺吉-agg-c noiseCopies.py |发球噪音。<ol>
<li>该脚本将首先从无噪音的可见性数据创建图像，调用标准射电天文学算法 CLEAN26 来创建像 图 3这样的图像。</li>
		<li>然后，脚本将创建 MS 的副本，并将适当的噪声级别添加到复杂的可见性数据中，并使用 CLEAN 进行图像。该脚本目前为长达 24 小时的集成时间和多个强大的加权计划值制作图像。根据阵列的配置，图像质量可能因数据加权方案的选择而异。这些嘈杂的图像将看起来像 图4，它使用了4小时的集成时间。 注意：噪声与标准信号添加到噪声公式中。从泰勒2 单极化的干涉学噪声是 <img alt="Equation 3" src="/files/ftp_upload/61540/61540equ03.jpg"> 在这里，η是系统效率或关联器效率，已设置为 0.8 的保守值。N蚂蚁是阵列中的天线数（每个可见性的N蚂蚁= 2），∆ν是正在Hz 中集成的带宽，∆t是几秒钟内的集成时间。</li>
	</ol>
</li>
</ol>

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N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+properties+of+lunar+surface.">Dielectric properties of lunar surface.</a> Solar System Research. 51, 121-126 (2017).</li><li>Yushkov, V., Kibardina, I., Yushkova, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+of+Electrophysical+Properties+of+the+Moon+Ground.">Modeling of Electrophysical Properties of the Moon Ground.</a> 2019 Russian Open Conference on Radio Wave Propagation (RWP). , 463-466 (2019).</li><li>Burke, G., Poggio, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Numerical+Electromagnetics+Code+(NEC)+method+of+moments.">Numerical Electromagnetics Code (NEC) method of moments.</a> Lawrence Livermore National Laboratory Technical Report. , (1994).</li><li>NASA-provided lunar payloads. NASA Glenn Research Center Available from: <a target="_blank" href="https://www1.grc.nasa.gov/space/planetary-exploration-science-technology-office-pesto/management/nasa-provided-lunar-payloads">https://www1.grc.nasa.gov/space/planetary-exploration-science-technology-office-pesto/management/nasa-provided-lunar-payloads</a> (2019)</li></ol>

作者没有什么可透露的。

模拟管道的每一步都是必要的，并输入到下一步，在月球表面进行阵列配置，正确调整参考帧，将阵列定位于天空中的目标区域，计算能见度数据，添加适当的噪声水平，并在生成的数据上运行成像算法。
对于每个步骤，可以进行自定义。在第 2 步中，用户定义的阵列配置可能是任何经度和纬度的列表。然后，在第 3 步中输入 SPICE 脚本，其中可以选择计划测量的确切时间，以及阵列应聚焦在天空中的位置。在第 3 步中，可以通过提供合适的 CASA 。truth 文件来指定阵列尝试映像的模拟真相发射。然后在第 4 步中，可能会根据观测频率和预期硬件功能更改预期的噪声水平。这组代码构成一个灵活的模拟框架，可根据目标科学对任意数量的用途的阵列设计进行重复。这些代码都可以在平均笔记本电脑或工作站上运行，但计算时间会随着天线数量的增加而增加。这个过程最慢的部分是预测可见性，然后是成像。对于小型阵列，整个过程可以在几分钟内完成，而对于几十万或几千个接收器的大型阵列，可能需要数小时或数天的时间。
使用此管道可以采取的一些后续步骤，以增加其现实性，包括添加一个依赖于渠道的前景拆除系统。这需要建立一个全球天空模型，以银河同步加速器发射的低频和Cas A等一些明亮的光源为主，跟踪接收机可见的天空的哪一部分，并将亮度模式与主光束结合在一起，阵列的相位中心与成像目标对齐。对于更长的集成时间，跟踪天空的明显运动也是一个问题。可以添加的另一个改进是瞬态事件/射频干扰 （RFI） 标记系统，该系统可以从正常成像中删除标记的通道，并将它们发送到图像和描述标记数据的专用管道。然后，此瞬态事件管道可以使用特殊的算法，如 uvmodelfit，可以利用这些事件的高信号与噪声比来描述它们比阵列27的正常分辨率更好。
还需要考虑其他影响，以便进行全阵列校准，其中之一是相互耦合。正如Ellingson28所讨论的，如果接收机彼此的波长在几个波长之内，这可能导致阵列的灵敏度降低。这体现在阵列的灵敏度降低，或相当于 SEFD 的增加。对于距离天顶10度以上的光束来说尤其如此。这项工作中的示例阵列以地球为目标，它的设计总是接近顶峰，因此相互耦合不应影响此特定成像目标，但需要在调试任何真正的阵列以释放其全部潜力时对 SEFD 进行全方位的高程角度和频率的研究。这种阵列模拟管道的另一个缺点在于使用的月球表面地图不完善。LRO LOLA 测量的 DEM 在 512 像素/度地图中最多具有 60x60 米/像素的分辨率。人们可以插话这些数据用于模拟阵列，但对于真正的阵列，需要有一个调试/校准周期，其中使用具有已知位置的源来确定所有天线与高精度之间的相对分离。可能的校准来源包括Cas A，周期性低频发射从木星或地球，或潜在的月球网关29。
还有月球表面的反应需要考虑。有一层月球表土称为重冰石，其作用就像是一种失去的介电，可以反射传入的辐射，具有一定的效率，在月球基岩之上，它也可以反映传入的发射，效率更高。此响应取决于环境温度和传入频率，以及重石的化学成分。研究30，31发现，在低于100K的低温下，重石对无线电发射几乎是透明的，反射发生在基岩水平，反射系数约为0.5-0.6。在 150-200 K 的高温下，重石可以吸收辐射并反射表面的传入辐射，反射系数约为 0.2-0.3。在超过200K的温度下，发现重石的介电特性会减弱，反射的变化可以忽略不计。这些效果可以减少阵列的有效区域，降低灵敏度，并需要更长的集成时间。这种效果可以用电磁模拟软件包（如NEC4.232）建模，这些软件包给出的相对许可/介电常数模型是月球深度的函数。这将输出给定频率的接收器的 SEFD，该频率可以输出到阵列模拟管道中，以计算添加到模拟信号的正确噪声。在接收器和月球表面之间添加接地网格可能有助于减少反射波的影响，但以部署的形式添加了自身的复杂情况。
围绕在月球表面实施无线电接收器的许多假设或模糊细节将最终凝固成为现实，最近资助的单低频天线项目，如光电子护套（ROLSES）月球表面的无线电波观测（ROLSES）和月球表面电磁实验（LuSEE）33。LuSEE最近由美国宇航局资助，作为商业月球有效载荷服务计划的一部分。两套天线将主要包括过去仪器（如立体声/波浪或 PSP FIELDS）的飞行备件，并计划于 2021 年交付。这些接收器的测量结果将最终巩固月球表面电离尘埃中光电子护套产生的准热噪声水平，以及它在月球日的变化。这些测量结果还将描述月球表面的反射和吸收水平，并量化它如何改变接收器的SEFD。它们还将提供关于月球表面接收的瞬态事件或RFI数量的统计数据。这些任务将为天线阵列铺平道路，这些天线最终将能够进行许多新的科学观测，如太阳无线电爆发的低频发射、遥远的星系和行星磁层。这项工作中描述的模拟管道为为各种科学目标重复这些未来阵列的设计提供了灵活的方法。

射电天文学领域始于1932年，卡尔·扬斯基1号在20兆赫时意外探测到银河系无线电发射，其范围现在通常称为低频无线电。从那时起，射电天文学发展迅速，赶上了已经持续了几个世纪的更高频率的光学观测。另一个突破是利用无线电干涉测量技术，利用远距离分离的天线组来制造合成孔径，为提高无线电观测2、3的灵敏度和分辨率提供了途径。这可以直观地视为光学观测常规分辨率公式的延伸：
<img alt="Equation 1" src="/files/ftp_upload/61540/61540equ01.jpg">
对于大小为 D 米的观测盘和λ 米的观测波长，hpBW Θ是半功率束宽度 （HPBW） 的弧度中的角大小，定义了天空中的分辨率。合成大满盘的一小部分，在大部分空区只散点的过程也被称为光圈合成。在无线电干涉测量领域，阵列的分辨率由阵列中任意两个接收器之间的最远距离决定，此距离在方程 1 中用作 D。
干涉学背后的数学在《射电天文学3》中的汤普森干涉学和合成等经典文本中得到了很好的记载。基本洞察可以非正式地传达为"（用于观察小视野的平面阵列）任何2个接收器（ 能见度）之间的信号交叉关联将产生有关天空亮度模式的2D Fourier系数的信息。傅立尔模式的采样取决于接收机（ 基线）的分离，由观测波长规范化。相距更远的接收器（在面向成像目标的标准紫外线坐标系统中）采样了更高的空间频率特征，在较小的尺度上产生更高的分辨率细节。相反，在同一 UVW 框架中紧密结合的接收器采样空间频率较低，以较低的分辨率提供较大规模结构的信息。
对于最低的无线电频率，地球电离层中的自由电子阻止低于10MHz的无线电波从太空传播到地面，反之亦然。 这种所谓的"电离层截流"长期以来一直阻止地面观测天空的这种频率范围。这种限制的明显答案是将无线电接收器送入太空，在那里它们可以记录数据，不受地球大气层的影响，并在其电离层中释放电子。在此之前，风4 号和STERO5号等航天器上的单一天线已经做到了这一点，它揭示了许多天体物理学过程，这些过程在这个低频无线电范围内产生排放。这包括电子与地球磁层的相互作用、太阳爆发产生的电子加速以及星系本身的辐射。单个天线观测可以测量此类事件的总通量密度，但无法确定发射来自何处。为了将这种低频发射本地化，并首次在这个频率机制中制作图像，许多天线将不得不被送入太空，并结合其数据来制造合成光圈。
这样做将打开一个新的窗口，通过这个窗口，人类可以观察宇宙，使一些科学测量，需要这些最低频率的天空图像。月球是太空中合成孔径的可能地点之一，与自由飞行轨道阵列相比，它具有优点和缺点。月球远端有一个独特的无线电静音区，可以阻挡来自人造信号的所有通常的干扰，而近侧为地球观测阵列提供了一个静态位置，如果在月球子地球点建造，地球将永远处于天空的顶峰。使用静态阵列，更容易获得测量大规模排放的短基线，因为它们没有碰撞的危险，不像自由飞行阵列。月球阵列的缺点主要是成本和功率上的困难。月球上的大规模阵列需要大量的基础设施和资金，而较小的轨道阵列需要的资源要少得多。还有权力问题：月球上的大多数地方都暴露在充足的阳光下，每个农历的1/3时间里，太阳能发电。从农历白天到晚上，在气温的大幅波动中幸存下来也是一个工程问题。抛开这些困难不谈，仍然存在确保拟议阵列设计适合其指定科学目标的问题。任何给定阵列的响应取决于所观察到的排放结构以及阵列的配置和灵敏度。
几十年来，在月球表面绘制了几个概念阵列。早期的设计不是最详细的，但仍然认识到科学的进步，可以达到这样的阵列6，7，8，9，10。近年来还提出了更多的阵列，其中一些阵列，如FARSIDE11、DEX12和DALI13，试图测量10-40 MHz范围内红移中性氢21厘米信号的吸收槽，以探测所谓的"黑暗时代"，并限制早期宇宙的宇宙模型。其他如ROLSS14呼吁跟踪明亮的太阳II型无线电爆发远到日光层，以确定太阳高能粒子加速在日冕物质抛射中的位点作为他们令人信服的科学案例。较小的比例阵列也被描述为2元干涉仪RIF15，它将使用单个着陆器和移动的漫游车来采样许多基线，因为它从着陆器向外移动。RIF 专注于首次绘制这些低频的天空地图的能力，并计算紫外线覆盖和合成光束以进行综合观测。
天基无线电阵列还可以对遥远的无线电星系进行低频成像，以确定磁场和天体测量16。这些物体的低频图像将更完整地反映管理这些系统的物理情况，特别是为电子能量分布的下端产生同步加速器发射数据。也有一系列的各种磁层辐射发生在这些低频，提供全球（恒定同步辐射）和局部（爆发，极光千公吨辐射）特征的电子动力学，无法从地面17。这些类型的最亮记录的排放来自地球和木星，因为这些行星最近的行星具有强大的磁层。然而，具有足够灵敏度和分辨率的阵列可以观测到来自其他外行星，甚至太阳系外行星18的磁层发射。在最近的行星科学展望2050研讨会上，这一主题尤其被作为一个感兴趣的领域提出来。
这项工作的重点是模拟月球上无线电阵列的反应，从几个天线到成百上千个天线，无所不包。此模拟框架可用于在小视野（几平方度）中对任何给定的科学目标进行成像的测定阵列设计，但目前不支持所有天空成像。必须使用预测亮度图和逼真的噪声配置文件的准确估计，以确保给定的阵列大小/配置足以将目标观测到一定的噪声水平或分辨率。还要高度了解阵列的几何形状，以便准确计算基线，以便正确成像数据。目前，月球表面最好的地图是月球勘测轨道飞行器（LRO）19月球轨道器激光高度计（LOLA）20的数字高程模型（DEMs）。模拟管道接受每个接收机的经度纬度坐标，并从现有 DEM 中插话这些点的高程以计算完整的 3D 位置。
从这些坐标计算 基线 并插入一个通用天文学软件应用程序 （CASA）21 测量集 （MS） 文件中。MS 格式可用于许多现有的分析和成像算法，并保存有关阵列配置、可见性数据和与天空对齐的信息。然而，许多这些软件程序很难与与地球表面一起旋转的阵列配合使用，并且不适用于轨道或月球阵列。为了规避此问题，此管道手动计算给定阵列和成像目标的基线和可见度，并将数据插入 MS 格式。SPICE22 库用于正确对齐月球和天空坐标系统，并跟踪月球、地球和太阳的运动。
这里描述的模拟框架遵循了海格杜斯等人17，该软件由密歇根大学图书馆存档在深蓝档案23，存储在https://deepblue.lib.umich.edu/data/concern/data_sets/bg257f178?locale=en。此存档软件的任何修补程序或更新都可以在https://github.com/alexhege/LunarSynchrotronArray找到。下一节将描述此软件的要求，并演练形成阵列、设置适当的噪声水平、为阵列提供目标发射的模拟真实图像以及使用 CASA 脚本模拟阵列的无噪音和嘈杂的排放重建过程。

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			<td>No physical materials are needed, this is a purely computational work.</td>
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simulating imaging of large scale radio arrays on the lunar surface

近年来，由于科学和探索性的原因，人们重新产生了重返月球的兴趣。月球为建造大型基地提供了完美的训练场，这些基地可能适用于火星等其他行星。月球远端存在一个无线电静音区，这为早期的宇宙研究和系外行星搜索提供了希望，而近侧则提供了一个稳定的基座，可用于观测地球磁层的低频辐射，这可能有助于测量其对来袭空间天气的反应。大型无线电阵列的建造将带来巨大的科学回报，并作为对人类在其他行星上建造结构能力的考验。这项工作的重点是模拟月球上由数百或数千个天线组成的小型到大型无线电阵列的反应。阵列的响应取决于发射的结构以及阵列的配置和灵敏度。模拟无线电接收机选择一组位置，使用月球轨道器激光高度计仪器在月球勘测轨道器上的数字高程模型来描述接收机位置的海拔高度。描述并使用自定义的通用天文学软件应用程序代码处理来自模拟接收器的数据，使用 SPICE 对齐月球和天空坐标帧，以确保用于成像的正确投影。此模拟框架可用于在小视野中对任何给定的科学目标进行成像的测定阵列设计。此框架目前不支持所有天空成像。

遵循软件管道应该相当简单，并且应该很明显，每个步骤都按照其应有的要求工作。从第 2 步运行createArrayConfig.py应创建类似于 图 1的图形，其中定义阵列的配置绘制在月球表面的局部地形之上，从 LRO LOLA 衍生的数字高程模型中提取。
第 3 步应提供关键输出文件eqXYZ_EarthCentered.txt、Ras .txt 和 12 月.txt等。这些文件的示例位于下载的包中。
第 4 步应创建类似于 图 2的真人图像，然后用于计算可见性数据。它还应输出一个 CASA 测量集 （.ms） 文件，该文件可以使用通常的 CASA 卡萨布劳尔命令进行浏览，以便查看计算和保存基线和可见性数据。
第 5 步应分别输出类似于 图 3 和 图 4 的数字，以显示无噪音和嘈杂的图像。嘈杂的图像看起来应该不如无噪音的图像清晰。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61540/61540fig01.jpg"> 图1：月球表面高程图阵列的配置。 这是一个示例阵列配置，由超过 10 km 的对数间隔圆形阵列组成。该配置有 32 臂 32 对数间隔天线，共 1024 天线。之所以选择阵列（-1.04°，-0.43°）的选址，是因为它是10x10公里补丁的中心，其海拔变化最低（σ=5.6米），靠近月球平均地球（ME）框架中的子地球点（0°，0°）。高程数据来自从 LRO LOLA 测量得出的数字高程图。这个数字取自赫格杜斯等人13日。 <a href="https://www.jove.com/files/ftp_upload/61540/61540fig01large.jpg" target="_blank">请点击这里查看此数字的较大版本。</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61540/61540fig02.jpg"> 图2：月球距离辐射带同步加速器发射的真实图像。 这是阵列成像的科学目标的一个例子。然后将恢复的图像与此输入进行比较，以确定阵列的性能。亮度图是由萨拉姆贝电子模拟数据创建的，通过计算确定在月球距离上观测到的同步加速器发射。将 1.91° 地球添加到刻度指示器中。这个数字取自赫格杜斯等人13日。 <a href="https://www.jove.com/files/ftp_upload/61540/61540fig02large.jpg" target="_blank">请点击这里查看此数字的较大版本。</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61540/61540fig03.jpg"> 图3：直径为10公里的阵列的无噪音响应，以输入真实图像。 这是第 5 步的输出之一，应用标准射电天文成像算法 CLEAN，使用具有 +0.5 强健度参数的布里格斯加权方案。这个数字取自赫格杜斯等人13日。 <a href="https://www.jove.com/files/ftp_upload/61540/61540fig03large.jpg" target="_blank">请点击这里查看此数字的较大版本。</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61540/61540fig04.jpg"> 图4：10公里直径阵列的嘈杂响应输入真实图像。 这是第 5 步的输出之一，应用标准射电天文学 CLEAN，使用具有 +0.5 强健度参数的布里格斯加权方案。对于此图像，使用了 1.38e7 Jansky 的系统等效通量密度、500 kHz 的集成带宽和 4 小时的集成时间。为了模拟 16K 天线阵列而不是 1K 天线阵列的响应，噪音也降低了 16 倍。这个数字取自赫格杜斯等人13日。 <a href="https://www.jove.com/files/ftp_upload/61540/61540fig04large.jpg" target="_blank">请点击这里查看此数字的较大版本。</a>

Watch this Scientific Journal Video about Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface at JoVE.com

Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface

提出了一个模拟框架，用于测试月球表面大型无线电阵列的成像能力。讨论了主要的噪声组件，并通过了软件管道，详细介绍了如何为新的科学用途自定义它。

模拟月球表面大规模无线电阵列的成像

In recent years there has been a renewed interest in returning to the Moon for reasons both scientific and exploratory in nature. The Moon provides the ...

simulating-imaging-of-large-scale-radio-arrays-on-the-lunar-surface

Research

JoVE Journal

Engineering

4.7K 次观看.  University of Michigan. 提出了一个模拟框架，用于测试月球表面大型无线电阵列的成像能力。讨论了主要的噪声组件，并通过了软件管道，详细介绍了如何为新的科学用途自定义它。

视频: Simulating Imaging of Large Scale Radio Arrays on the Lunar Surface

Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

X-ray microtomography was used to image, at a resolution of 6.6 &#181;m, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space of a carbonate rock at pressures and temperatures representative of typical formations used for CO2 storage. Chemical equilibrium between the CO2, brine and rock phases was maintained using a high pressure high temperature reactor, replicating conditions far away from the injection site. Fluid flow was controlled using high pressure high temperature syringe pumps. To maintain representative in-situ conditions within the micro-CT scanner a carbon fiber high pressure micro-CT coreholder was used. Diffusive CO2 exchange across the confining sleeve from the pore-space of the rock to the confining fluid was prevented by surrounding the core with a triple wrap of aluminum foil. Reconstructed brine contrast was modeled using a polychromatic x-ray source, and brine composition was chosen to maximize the three phase contrast between the two fluids and the rock. Flexible flow lines were used to reduce forces on the sample during image acquisition, potentially causing unwanted sample motion, a major shortcoming in previous techniques. An internal thermocouple, placed directly adjacent to the rock core, coupled with an external flexible heating wrap and a PID controller was used to maintain a constant temperature within the flow cell. Substantial amounts of CO2 were trapped, with a residual saturation of 0.203 &#177; 0.013, and the sizes of larger volume ganglia obey power law distributions, consistent with percolation theory.

We present a methodology for the imaging of multiple fluid phases at reservoir conditions by the use of x-ray microtomography. We show some representative results of capillary trapping in a carbonate rock sample.

多重流体相储层孔隙条件级成像使用X射线微断层

X-ray microtomography was used to image, at a resolution of 6.6 &#181;m, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space ...

科研

工程学

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

高速喷液嵌塞对移动表面的可视化

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

烧蚀材料在试验过程中等离子体发生器发射光谱边界层研究

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Dynamic Pore-scale Reservoir-condition Imaging of Reaction in Carbonates Using Synchrotron Fast Tomography

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve geologic seals and allow CO2 to escape. However, the dissolution processes at reservoir conditions are poorly understood. Thus, time-resolved experiments are needed to observe and predict the nature and rate of dissolution at the pore scale. Synchrotron fast tomography is a method of taking high-resolution time-resolved images of complex pore structures much more quickly than traditional &#181;-CT. The Diamond Lightsource Pink Beam was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 hours. The images were segmented and the porosity and permeability were measured using image analysis and network extraction. Porosity increased uniformly along the length of the sample; however, the rate of increase of both porosity and permeability slowed at later times.

Synchrotron fast tomography was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 h.

用同步快速反应层析成像动态孔隙规模油藏条件下成像碳酸盐

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve ...

Nanostructured Ag-zeolite Composites as Luminescence-based Humidity Sensors

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high external quantum efficiencies (EQE) and spans the whole visible spectrum. It has been recently reported that the UV excited luminescence of partially Li-exchanged sodium Linde type A zeolites [LTA(Na)] containing luminescent silver clusters can be controlled by adjusting the water content of the zeolite. These samples showed a dynamic change in their emission color from blue to green and yellow upon an increase of the hydration level of the zeolite, showing the great potential that these materials can have as luminescence-based humidity sensors at the macro and micro scale. Here, we describe the detailed procedure to fabricate a humidity sensor prototype using silver-exchanged zeolite composites. The sensor is produced by suspending the luminescent Ag-zeolites in an aqueous solution of polyethylenimine (PEI) to subsequently deposit a film of the material onto a quartz plate. The coated plate is subjected to several hydration/dehydration cycles to show the functionality of the sensing film.

A protocol for the synthesis of moisture-responsive luminescent Ag-zeolite composites is described in this report.

纳米银沸石复合材料作为基于发光的湿度传感器

Small silver clusters confined inside zeolite matrices have recently emerged as a novel type of highly luminescent materials. Their emission has high ...

Experimental Implementation of a New Composite Fabrication Method: Exposing Bare Fibers on the Composite Surface by the Soft Layer Method

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional component that should have high electrical conductivity, high mechanical properties, and high productivity.
In this regard, a carbon fiber/epoxy resin composite can be an ideal material to replace the conventional graphite bipolar plate, which often leads to the catastrophic failure of the entire system because of its inherent brittleness. Though the carbon/epoxy composite has high mechanical properties and is easy to manufacture, the electrical conductivity in the through-thickness direction is poor because of the resin-rich layer that forms on its surface. Therefore, an expanded graphite coating was adopted to solve the electrical conductivity issue. However, the expanded graphite coating not only increases the manufacturing costs but also has poor mechanical properties.
In this study, a method to expose fibers on the composite surface is demonstrated. There are currently many methods that can expose fibers by surface treatment after the fabrication of the composite. This new method, however, does not require surface treatment because the fibers are exposed during the manufacture of the composite. By exposing bare carbon fibers on the surface, the electrical conductivity and mechanical strength of the composite are increased drastically.

A protocol to expose bare fibers on the composite surface by eliminating resin rich area is presented. The fibers are exposed during fabrication of the composites, not by the post surface treatment. The exposed carbon composites exhibit high electrical conductivity in the through-thickness direction and high mechanical property.

一种新的复合制备方法的实验实现: 用软层法对复合材料表面裸露纤维进行曝光

The bipolar plate is a key component in proton exchange membrane fuel cells (PEMFCs) and vanadium redox flow batteries (VRFBs). It is a multi-functional ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

不锈钢滑面的制备及高温抗粘接性能研究

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF) magnetron sputtering. LSMO nanoparticles were deposited with diameters from 10 to 20 nm and heights between 20 and 50 nm. At the same time, (Gd) Ba2Cu3O7&#8722;&#948; ((Gd) BCO) films were fabricated on both undecorated and LSMO nanoparticle decorated STO substrates using RF magnetron sputtering. This report also describes the properties of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 quasi-bilayer films structures (e.g., crystalline phase, morphology, chemical composition); magnetization, magneto-transport, and superconducting transport properties were also evaluated.

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7ÃƒÂ¢Ã‹â€ &#039;ÃƒÅ½ ´/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 STO Single-crystal Substrates

Here, we present a protocol to grow LSMO nanoparticles and (Gd) BCO films on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF)-sputtering.

Gdba2cu 3 o7 的射频磁控管散射-/la0.67sr 0.67 mno 3 准双层薄膜上的 srtio 3 (sto) 单晶基板上

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio ...

Characterization of SiN Integrated Optical Phased Arrays on a Wafer-Scale Test Station

Optical phased arrays (OPAs) can produce low-divergence laser beams and can be used to control the emission angle electronically without the need for moving mechanical parts. This technology is particularly useful for beam steering applications. Here, we focus on OPAs integrated into SiN photonic circuits for a wavelength in the near infrared. A characterization method of such circuits is presented, which allows the output beam of integrated OPAs to be shaped and steered. Furthermore, using a wafer-scale characterization setup, several devices can easily be tested across multiple dies on a wafer. In this way, fabrication variations can be studied, and high-performance devices identified. Typical images of OPA beams are shown, including beams emitted from OPAs with and without a uniform waveguide length, and with varying numbers of channels. In addition, the evolution of output beams during the phase optimization process and beam steering in two dimensions is presented. Finally, a study of the variation in the beam divergence of identical devices is performed with respect to their position on the wafer.

Here, we describe the operation of a SiN integrated photonic circuit containing optical phased arrays. The circuits are used to emit low divergence laser beams in the near infrared and steer them in two dimensions.

晶圆级试验站上SiN集成光学相控阵列的特性

Optical phased arrays (OPAs) can produce low-divergence laser beams and can be used to control the emission angle electronically without the need for ...

Fabrication of Surface Acoustic Wave Devices on Lithium Niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale&#8212;and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

Two fabrication techniques, lift-off and wet etching, are described in producing interdigital electrode transducers upon a piezoelectric substrate, lithium niobate, widely used to generate surface acoustic waves now finding broad utility in micro to nanoscale fluidics. The as-produced electrodes are shown to efficiently induce megahertz order Rayleigh surface acoustic waves.&#160;

锂氮化锂表面声波设备的制造

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order ...