Lunar Reference Systems

该项目的目标是实现与月球相关的系统始终与ITRS/ICRS捆绑在一起，这是进一步开展月球科学和探索的先决条件。该项目还为转让用于绘制地外天体地图的已有大地测量方法铺平了道路。在第一阶段，基本概念已经形成：我们改进了LLR的分析和建模，例如通过增加一个地面站和反射站，以及考虑到月球反射器的潮汐位移。我们重新分析了LLR数据集，包括目前所有可用的LLR正常点。通过仿真，我们展示了新型反射器类型的好处。我们已经演示了如何将着陆点的照片与LRO图像相结合，以生成由LLR反射器坐标稳定的高精度本地地图。我们已经开发了基于不同类型的跟踪数据的LRO轨道确定技术。在第二供资阶段，将进一步推广这些方法，例如使用LOLA交叉或来自D-VLBI的新数据。主要目标是完善月球参考系的实现，将其始终如一地嵌入ICRF。这将通过采取不同的措施来实现：1)实现毫米级精度的LLR建模。改进影响月球运动和自转的模型，例如外力矩和内力矩，将进一步改善LLR后向反射器坐标，使其成为月球参考系的逐点实现。2)从多个数据集重建精确的LRO轨道。应利用辐射测量和LRO单向激光跟踪和测高数据，建立综合确定月球重力轨道和低次谐波的独立能力。3)整合LRO和GRAIL飞行任务的新数据。我们将在德国开发一种独立于NASA的能力，将LRO测高和图像参考到月球系统，并为改进月球的物理参数做出贡献。在项目结束时，我们将能够分析其他轨道飞行器任务的数据。4)数据组合。LROC图像和LOLA高度计的组合将为准确绘制月球地图奠定基础。LROC图像与以前登月任务的图像结合在一起，并绑定到LLR反射器坐标。在极地地区，来自LOLA的准确的DTMS将成为生成照明图的基础，这对于未来的着陆任务将是有价值的，以确定具有尽可能长的日光时间的地方。5)月球参考系的新解决方案。将通过分析月球和类星体无线电发射机之间的模拟和实际差异VLBI测量，形成LLR与VLBI观测相结合的概念。作为主要成果，将改进目前对硒中心系的认识，以获得准确的、全月统一的坐标知识和高分辨率的月球地图。这个月球框架将牢牢地与ICRF和ITRF捆绑在一起。

The goal of this project is to realize Moon-related systems consistently tied to the ITRS/ICRS, a prerequisite for further lunar science and exploration. This project also paves the way for transferring established geodetic methods for mapping of extra-terrestrial bodies. In the first period, basic concepts have been developed: We have improved LLR analysis and modelling, e.g. by an added ground and reflector station, as well as taking tidal displacements of lunar reflectors into account. We re-analysed the LLR data set including all currently available LLR normal points. Through simulations, we showed the benefit of novel reflector types. We have demonstrated how photographs of landing sites can be combined with LRO images to generate highly accurate local maps stabilised by the LLR reflector coordinates. We have developed techniques for LRO orbit determination based on different types of tracking data. In the second funding phase, these methods shall be further extended, e.g. by using LOLA crossovers or novel data from D-VLBI. The major objectives are to refine realisations of the lunar reference system, consistently embedded into the ICRF. This will be achieved by taking different measures:1) Realise LLR modelling with mm-level of accuracy. Refinement of models affecting lunar motion and rotation, e.g. external and internal torques, will further improve the LLR retroreflectors¿ coordinates as point-wise realisations of the lunar reference system.2) Reconstruct precise LRO orbits from multiple data sets. An independent capability for combined determination of orbits and low-degree harmonics of lunar gravity shall be established, using radiometric as well as LRO one-way laser tracking and altimetric data.3) Integrating novel data from missions LRO and GRAIL. We will develop a capability in Germany, independent from NASA, for referencing LRO altimetry and imagery to the lunar system, and contributing to improved physical parameters of the Moon. At the end of project, we will be able to analyse data from other orbiter missions.4) Data combinations. Combinations of LROC images and LOLA altimetry will lay the basis for accurately mapping the Moon. LROC images are combined with images from former lunar missions and tied to the LLR reflector coordinates. In the polar regions, accurate DTMs from LOLA will be the basis for generating illumination maps, which will be valuable for future landing missions, to identify places with the longest possible daylight hours.5) New solutions of the lunar reference system. A concept for the combination of LLR with VLBI observations will be developed by analysing simulated and, if possible, real differential VLBI measurements between radio transmitters on the Moon and quasars. As a major result, the current realisation of the selenocentric system will be improved to achieve accurate and Moon-wide uniform coordinate knowledge and a high-resolution lunar map. This lunar frame will be firmly tied to the ICRF and ITRF.