Lunar Laser Ranging at the University of Texas at Austin

月球激光测距(LLR)实验精确地测量了从地球上的一个观测站发射的激光脉冲的往返旅行时间，该脉冲从月球表面的一个后向反射器阵列反弹回来。这样的观测已经在麦克唐纳天文台进行了30多年。这些数据提供了固体地球科学、大地测量和地球动力学、太阳系星历、地球和天文参照系、月球物理、广义相对论和引力物理等领域的各种多学科和跨学科的科学成果。LLR单独或结合其他观测技术的数据，扩展了对地球自转轴的进动、月球章动、地球定向、地球对黄道的倾角、天赤道和黄道的交集、月球和太阳固体潮汐、月球潮汐减速、月球物理和自由振动、月球结构和月球内部能量耗散的理解。LLR为月球表面制图和测量提供输入，并帮助确定地面站和月球表面后向反射器的位置和运动、地月系统的质量、月球和地球重力调和和洛夫数、相对论测地进动以及广义相对论的等价原理。由于反射器的被动性质以及观测设备和数据分析能力随着时间的推移而不断改进，LLR数据将继续提供更好的结果。收益是稳定的，随着数据库的扩大，我们正在努力通过应用更聪明的观察策略来了解更多。根据这项提议，我们将继续在麦克唐纳激光测距站(MLRS)进行LLR观测工作。随着常规的单人操作和24小时/天、7天/周的时间表，月球覆盖在未来几年将是相当大的，因为我们与人造卫星激光测距(SLR)工作共享MLRS的使用。我们正在与世界各地的其他观测工作合作，特别是法国南部的LLR/SLR站。除了观察之外，德克萨斯大学奥斯汀分校还将进行一项全球沟通、合作和协调的分析工作。我们与喷气推进实验室、麻省理工学院、巴黎天文台以及法兰克福和慕尼黑的BKG的分析工作合作。此外，自1998年国际激光测距服务(ILRS)成立以来，德克萨斯大学麦克唐纳天文台设有ILRS LLR操作和分析中心。LLR观测网络的规模较小，LLR分析中心的数量相对较少，这决定了LLR操作/分析中心的独特性质和操作程序。LLR业务中心的职责已经演变为确保LLR网络中数据的顺畅流动，其形式和格式对于获得科学成果是有用的。该中心还以最大限度地提高科学成果的方式协调观测及其时间表。预报在每个LLR站现场协调，数据从所有观测点自动传输到ILRS数据中心。LLR数据分析师可以根据需要直接从数据中心保护他们的数据。这些分析员的反馈通常会直接反馈到各个观测站。在这笔国家科学基金的资助下，我们期待着在未来几年内对LLR进行成功的观测和分析，从而稳步和快速地扩大科学成果。***

AST-0204127ShelusThe Lunar Laser Ranging (LLR) experiment accurately measures the round-trip travel time for a laser pulse that is emitted from an observing station on the Earth and returns after bouncing off of a retroreflector array on the surface of the Moon. Such observations have been made at McDonald Observatory for more than 30 years. The data provide for varied, multi-disciplinary and inter-disciplinary science results in areas of solid Earth sciences, geodesy and geodynamics, solar system ephemerides, terrestrial and celestial reference frames, lunar physics, general relativity and gravitational physics. Standing alone or combined with data from other observing techniques, LLR expands the understanding of the precession of the Earth.s spin axis, the lunar nutation, Earth orientatation, the Earth.s obliquity to the ecliptic, the intersection of the celestial equator and the ecliptic, lunar and solar solid body tides, lunar tidal deceleration, lunar physical and free librations, the structure of the moon and energy dissipation in the lunar interior. LLR provides input into lunar surface cartography and surveying and helps determine Earth station and lunar surface retroreflector locations and motions, mass of the Earth-Moon system, lunar and terrestrial gravity harmonics and Love numbers, relativistic geodesic precession, and the equivalence principle of general relativity. Due to the passive nature of the reflectors and the improvement of observing equipment and data analysis capabilities with time, LLR data will continue to provide for improved results. Gains are steady and, as the data base expands, we are striving to learn even more by applying more clever observation strategies. Under this proposal, we continue the LLR observational effort at the McDonald Laser Ranging Station (MLRS). With routine single-person operation and a 24 hour/day, 7 day/week schedule, lunar coverage will be substantial in the years to come, as we share the use of the MLRS with artificial satellite laser ranging (SLR) efforts. We are cooperating with other observing efforts around the world, especially the French LLR/SLR station in the south of France. In addition to the observations, an analysis effort with world-wide communication, cooperation, and coordination will be ongoing here at the University of Texas at Austin. We cooperate with analysis efforts at the Jet Propulsion Laboratory, the Massachusetts Institute of Technology, the Paris Observatory, and the BKG in Frankfurt and Munich. Also, the University of Texas McDonald Observatory, since the inception of the International Laser Ranging Service (ILRS) in 1998, houses the ILRS LLR Operations and Analysis Center. The small size of the LLR observing network, and the relatively small number of LLR analysis centers, dictate the unique nature and operational procedures of this LLR Operations/Analysis Center. The responsibility of the LLR Operations Center has evolved to be one that assures the smooth flow of data through the LLR network, in a form and format that is useful for obtaining scientific results. The center also coordinates the observations and their scheduling in a manner to maximum the scientific gains. Predicts are coordinated on-site at each LLR station and the data are automatically transferred from all observing sites to the ILRS data centers. LLR data analysts can secure their data directly from the data centers as needed. Feed-back from these analysts often goes directly back to the individual observing stations. Under the auspices of this National Science Foundation Grant, we are looking forward to additional years of successful LLR observation and analysis, resulting in the steady and rapid expansion of scientific results. ***