Geometry Numerical Simulation and Analysis for Moon-Based Earth Observation

Because of their scientific and social significance, large-scale geoscientific phenomena are attracting more and more attention. However, many existing Earth observation systems lack the ability to conduct long-term continuous observations on regional to global scales because of limitations on spatial and temporal coverage and the existence of systematic bias. The geometrical relationship between the Sun, Earth, and Moon is a precondition to understanding the Moon-based Earth observation (MEO). In this study, a geometry numerical simulation system for the MEO is developed based on Jet Propulsion Laboratory ephemerides data, time system transformations, and reference system transformations. Using this system, we study changes of Moon-based sensors (MBSs) subpoints in the year 2016 and from 1901 to 2016, the local azimuth–elevation angle of a point of interest on the Earth at different times in 2016 and throughout that year, and changes in observation duration at four different locations in 2016 and from 1901 to 2016. A nonlinear fitting method is used to analyze the periodic behavior of observation durations. Some factors influencing the MEO geometry are also analyzed, including the influence of the DE data source on MBS's position and on the azimuth–elevation angle of a point of interest on the Earth, the influence of the minimum observation elevation angle on the MBS observation extent, and the influence of the MBS location on the subpoint, azimuth–elevation angle, and observation period. The results show that Moon-based Earth observatory has specific and unique advantages in terms of observation geometry, which makes it suitable for observation of large-scale geoscientific phenomena.