Abstract:

Several key techniques are validated by Chang’E-2 (CE 2), including the direct transfer trajectory to moon and the lunar orbit insertion maneuver at 100km altitude, etc. Then, an extended mission to sun earth Lagrangian point L2 was carried out. For new characteristics of the trajectories, mission design and orbit determination strategy are presented. Based on post processed precision ephemeris, the orbit determination and prediction accuracy of pre maneuvers is evaluated and fast assessments of post maneuvers are performed. Based on orbit determination results before lunar insertion, the 3 hour predicted position error of perilune is 1km and the velocity error is 0.3m/s. A comparison of the orbit determination results with 3 different lunar potential field models is presented. The analysis of measurement residuals and post processed ephemerides shows that RMS of the residuals using SGM100h is the maximal of all. Furthermore, orbit determination accuracy of the different types of measurements is evaluated for CE 2 extended mission. Measurement residuals are analyzed based on pre TCM precision ephemeris. The RMS of data residuals including ranging, time delay and time delay rate are respectively 5m, 5ns and 1ps/s.

Key words: Chang’E-2, Mission design, Orbit determination strategy, Lunar gravity field, Sun earth Lagrangian point L2, Orbit determination accuracy