Orbit Determination Of Lunar Satellites Based On Space Stations

Since 1960s, as a consequence of the competitions in space explorations, the United States and the former Soviet Union launched the first lunar probes. From 1958 to 1976, totally 83 manned or unmanned lunar probes had been launched by the United States and the former Soviet Union, making this era a milestone in the lunar exploration. Since 1980s, the space exploration technology and the lunar scientific research reached a new level, the United States successfully launched two lunar probes "Clementine" and "Lunar Prospector" respectively for high accuracy measurement of the Moon. At the beginning of 21st century, the world’s leading space organizations have again started missions to the Moon. The European space agency (ESA), the Japan’s space agency (JAXA) and the Indian space research organization (ISRO) all launched their own first lunar probe (SMART-1, Selene-1, Chandrayaan-1). NASA also launched three lunar orbiters (LRO, LCROSS, GRAIL). At the same time, our country launched the "Chang’e-1", "Chang’e-2" and "Chang’e-3" lunar probes successively, which fulfilled the first two stages ("round" and "down") of China’s lunar exploration project. In all these lunar explorations, the probe’s precise orbit is the key to the success of the missions.Usually, orbit determination of the lunar satellites mainly depends on the observation data from the ground stations (such as deep space network DSN). For example, our country’s "Chang’e-1" use both the USB and the VLBI from the ground stations. However, the Moon is about 380000 kilometers away from the Earth. The long distance brings severe challenges to the data transmission and accuracy. Besides, a growing number of satellites also increases the load of the ground stations. In addition, due to the coupling of orbital and rotational motions, the Moon has always one side towards the Earth. When the lunar satellites are at the far side of the Moon, they are invisible to the Earth. This causes the discontinuities in the observations from the ground stations, and consequently influences the navigation and positioning of the lunar satellites.To solve these problems, Beckman from the Goddard space flight center and some researchers from the university of Colorado proposed the so-called LiAISON (Linked, Autonomous, Interplanetary Satellite Orbit Navigation). This strategy uses the inter-satellite range data to fulfill the autonomous orbit determination of lunar satellites. Some domestic research teams (for example, the team lead by Prof. Dulan at the PLA Information Engineering University) also contribute to this study. The main idea of these studies is to use the inter-satellite data between a lunar satellite and a probe around the collinear libration point (CLP for brevity) of the Earth-Moon system to simultaneously determine the orbits of the lunar satellite and the CLP probe. Based on these previous studies, mis thesis made a farther and systematic study on this topic, and extended the idea to another special orbit in the Earth-Moon system, i.e., the distant retrograde orbit (hereafter, DRO for brevity). In this thesis, the study is firstly carried out in the circular restricted three-body problem, and then extended to the actual force model. My research shows that:(1) The autonomous orbit determination between the CLP (or DRO) probe and the lunar satellite is feasible in theory. A short length of data (2-5 days) can recover the orbit determination accuracy of the lunar satellite to that of the observations, and a longer length of data (-10 days) can recover the orbit determination accuracy of CLP (or DRO) probe to that of the observations;(2) For the CLP probe, large halo orbits are recommended. This is because these orbits have better stability, better visibility to the Moon and the lunar satellite, and better performance in the orbit determination;(3) For the DRO probe, it is recommended to use DRO orbits of moderate amplitude in x direction (-45000km). The observation geometry and the corresponding orbit determination accuracy can be improved by adding a moderate out-of-plane displacement to the DRO probe;(4) For the orbit determination with short length of data, the observation geometry and orbit determination accuracy of lunar satellite and the probe can be improved by adding one or more CLP (or DRO) probes;(5) Compared with the CLP orbit, the DRO has better stability. As a result, the orbit control frequency can be smaller. Only judging from the orbit control, it’s better to use the DRO instead of the CLP orbit.In this paper, the idea is also extended to the autonomous orbit determination between the CLP probe and the GEO/IGSO satellite. My researches show that it is also feasible to determine the orbit of the GEO/IGSO satellite autonomously only using the inter-satellite range data between the CLP probe and the GEO/IGSO satellite.