Lunar Reference Systems

该项目的目标是实现与ITRS/ICRS一致的月球相关系统，这是进一步开展月球科学和探索的先决条件。该项目还为转让已确立的地外天体测绘大地测量方法铺平了道路。在第一阶段，基本概念已经制定：我们已经改进了LLR分析和建模，例如通过增加地面和反射站，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，包括所有当前可用的LLR正常点。通过模拟，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度精确的局部地图。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。在第二个供资阶段，这些方法将得到进一步扩展，例如，通过使用LOLA交叉或D-VLBI的新数据。其主要目标是完善月球参考系的实现，并始终嵌入ICRF。这将通过采取不同的措施来实现：1）实现具有mm级精度的LLR建模。对影响月球运动和旋转的模型进行改进，例如外部和内部扭矩，将进一步改善LLR后向反射器的坐标，作为月球参考系的逐点实现。应建立独立的能力，利用辐射测量数据以及LRO单向激光跟踪和测高数据，综合确定轨道和月球重力低阶谐波。我们将在德国发展一种独立于美国航天局的能力，以便将LRO测高和成像技术用于月球系统，并为改进月球的物理参数作出贡献。在项目结束时，我们将能够分析来自其他轨道飞行器任务的数据。LROC图像和LOLA测高仪的组合将为精确绘制月球地图奠定基础。LROC图像与以前的月球任务图像相结合，并与LLR反射器坐标相关联。在极地地区，LOLA的精确DTM将成为生成照明地图的基础，这对未来的着陆任务很有价值，以确定日照时间最长的地方。将通过分析月球和类星体上无线电发射机之间的模拟和（如果可能的话）真实的差分甚长基线干涉测量数据，提出将激光测距与甚长基线干涉测量相结合的概念。作为一项主要成果，目前实现的月心系统将得到改进，以获得准确和全月统一的坐标知识和高分辨率的月球地图。这个月球框架将与ICRF和ITRF紧密相连。

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.