Testing Gravity via Lunar Laser Ranging: APOLLO Analysis and Acquisition

最近建造的阿帕奇点天文台月球激光测距操作（APOLLO）已成为世界上首屈一指的月球激光测距（LLR）设施，在地球和月球之间提供1毫米的距离精度，作为测试广义相对论的一种方式。广义相对论对月球轨道的形状做出了具体的预测，因此我们可以将月球作为实验室，这是由阿波罗宇航员和苏联无人驾驶漫游者留在月球上的反射器实现的。这项工作的目标是将高质量的LLR观测再延长三年，同时收集足够好的当地重力校准测量结果，以确定毫米级的场地位移。与此同时，还将开始加紧努力，将太阳系模型提高到可以利用毫米级质量数据的状态。通过与一个完整而复杂的模型进行比较，可以探索与重力、地球物理学和月球物理学有关的问题。虽然不是主要的焦点，但月球内部的知识将从APOLLO中获得最多，因为该实验通常在一次会议中获得4到5个反射器，提供对月球方向和扭曲的精确测量。但是，这些关于月球的精确知识也将有助于了解月球在其轨道上的运动，因为这些信息对于确定月球质心在太空中的路径至关重要。LLR测试了重力的许多基本方面，如等效原理，重力恒定性，重力磁性和平方反比定律。因此，提高我们对引力的认识，对宇宙学家、天体物理学家、粒子物理学家和弦理论家都有很大的启发。这项工作也将有助于地球和行星科学，特别是通过纳入超导重力仪数据。该项目中出现的开源太阳系分析代码将为分析广泛的数据集提供一个有趣的平台，包括太阳系雷达测距、太阳系周围航天器的多普勒雷达、脉冲星计时实验等。此外，研究生和博士后培训是整个努力的一个宝贵组成部分。最后，阿波罗将继续其强大的公共宣传传统，包括在流行的电视节目中露面。

The recently built Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) has become the premier lunar laser ranging (LLR) facility in the world, delivering one-millimeter range precision between Earth and Moon as a way to test General Relativity. General Relativity makes specific predictions about the shape of the lunar orbit, so that we may use the Moon as a laboratory, made possible by the reflectors left on the Moon by the Apollo astronauts and unmanned Soviet rovers. The goal of this work is to extend high-quality LLR observations over an additional three-year period, simultaneously collecting calibrated measurements of local gravity well enough to determine site displacements at the millimeter level. In tandem, an intensive effort will be initiated to advance the solar system model to a state that can take advantage of millimeter-quality data. It is by comparison to a complete and sophisticated model that questions relating to gravity, geophysics, and lunar physics can be explored. Though not the main focus, knowledge of the lunar interior stands to gain the most from APOLLO, as the experiment routinely acquires 4 to 5 reflectors in one session, providing exquisite measurements of the lunar orientation and distortion. But this refined knowledge of the moon will also facilitate understanding of how the moon moves in its orbit, as such information is crucial to determining the path of the Moon's center of mass through space.LLR tests many fundamental aspects of gravity, like the equivalence principle, the constancy of gravity, gravitomagnetism, and the inverse-square law. Improving our knowledge of gravity therefore informs a diverse range of cosmologists, astrophysicists, particle physicists, and string theorists. This effort will also contribute to Earth and planetary science, especially via the inclusion of the superconducting gravimeter data. The open-source solar-system analysis code emerging from the project will provide an interesting platform for analyzing a wide range of data sets, including radar ranging in the solar system, Doppler radar to spacecraft around the solar system, pulsar timing experiments, etc. The same platform can form the basis of covariant studies for future proposed space missions that aim to test fundamental physics. Additionally, graduate student and postdoctoral training is a valuable component of the total effort. Finally, APOLLO will continue its strong tradition of public outreach, including featured appearances on popular television shows.