Research and Implementation of a Visual Simulation System of Orbital Motion of the Chang'E-2 Spacecraft

We develop a visual simulation system of the orbital motion of the Chang'E-2 based on OSG (Opensencegraph) by utilizing the terrain and image data obtained from the Chang'E-1 and the ephemeris data for the Chang'E-2, Sun, Earth, and Moon. The system satisfies the requirements for simulating the detectors of the Chang'E-2 when in operation, and it has been used for practical missions of the Chang'E-2. We first introduce the OSG, an open-source 3D graphic engine, and then describe the design of a structural model to integrate the basic frames and components of the simulating system. We finally give the details of some implementation methods of the system, such as those of modeling the moon/Chang'E-2, construction/access of the ephemeris database, update of spatial positions of simulated objects, simulation of CCD camera detection, and control of viewpoints. We show simulation results for the observation of the Chang'E-2 over the Sinus Iridum on the moon. The simulation system is of 4-dimensional as it incorporates the time dimension, achieving the simulation of the terrestrial-lunar spatial relationship. In addition, the system can simulate the appearance of lunar surface below the Chang'E-2 and the data acquisition process of the two-line CCD camera.