A Comprehensive Probe of Gravity via Lunar Laser Ranging

APOLLO（Apache Point Observatory Lunar Laser-ranging Operation）旨在通过测量月球轨道的形状来测试我们当前引力理论的基础-爱因斯坦的广义相对论-精确到一毫米。 这项技术涉及到从阿波罗宇航员放置在月球上的反射器上反射激光脉冲。 通过测量激光脉冲的往返飞行时间来确定到月球的距离，从而可以跟踪月球轨道的形状。在阿波罗计划之前，这种技术确定月球轨道形状的精度为2-3厘米，并验证了广义相对论的正确性，精度约为0.1%。 通过使用3.5米的望远镜和现代仪器，APOLLO能够达到1毫米的范围精度，因此可以进行0.01%的广义相对论精度测试。 阿波罗现在正在进行例行操作，收集第一批数据。根据这项奖励，阿波罗将改进其技术，并产生其第一个科学成果。 月球测距技术的简单优雅，加上它与我们历史上鼓舞人心的阿波罗登月计划的联系，使阿波罗成为向公众传达科学兴奋的合适工具。该奖项由物理学部和数学和物理科学理事会多学科活动办公室共同资助。

APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) aims to test the foundations of our current theory of gravity--Einstein's General Relativity--by measuring the shape of the lunar orbit to one-millimeter precision. The technique involves bouncing laser pulses off reflectors placed on the moon by the Apollo astronauts. Measuring the round-trip time-of-flight of the laser pulses determines the distance to the moon, thus allowing the shape of the lunar orbit to be traced.Prior to APOLLO, this technique determined the lunar orbit shape to 2-3 cm precision, and verified the correctness of General Relativity to about the 0.1% level of precision. By using a 3.5 meter telescope and modern instrumentation, APOLLO is capable of one-millimeter range precision, and will thus allow 0.01% precision tests of General Relativity. APOLLO is now in routine operation collecting its first data. Under this award, APOLLO will refine its technique and produce its first scientific results. The simple elegance of the lunar ranging technique, coupled with its connection to our historically inspiring Apollo lunar program, make APOLLO an apt vehicle for communicating the excitement of science to the public. This award is co-funded by the Physics Division and by the Office of Multidisciplinary Activities in the Mathematical and Physical Sciences Directorate.