Determination of the controlled landing trajectory of Chang’E-1 satellite and the coordinate analysis of the landing point on the Moon

Abstract

Based on the tracking observations of radio ranges and VLBI delays of Chang'E-1 (CE-1) satellite during the controlled landing on the Moon on March 1, 2009, the landing trajectory and the coordinates of the landing point are determined by positioning analysis. It is shown that the landing epoch (the emission epoch of the last signal) of CE-1 satellite on the Moon was at UTC8h13m6.51s. The lunar longitude, latitude and surface height of the landing point in the lunar primary axes frame are respectively 52.2732°, 1.6440° and -3.56 km (the reference lunar radius is 1738 km). The uncertainties are 0.0040°, 0.0168° and 0.18 km. The corresponding uncertainty in the tangential direction of the lunar surface is 0.52 km and the three-dimensional (3D) positioning uncertainty is 0.55 km. It is accordingly deduced that even with the present technical specifications of the radio ranges and VLBI delays, the 1 km 3D positioning precision could be guaranteed for the lander in the second stage of China's Lunar Exploration Project. Concerning the trace determination of the rover on the lunar surface, because only telemetry signal will be emitted, VLBI would be the sole tracking technique from the Earth. The application of the constraint of geocentric distance is shown to be helpful to improving the positioning precision. It is worthy to pay close attention to the applications of the same beam VLBI technique, the lunar topographic model and the on-board observations of the lander and rover to the position/trace determination of the rover. China's Lunar ExplorationProject, Chang'E-1 satellite, controlled landing on the Moon, trajectory measurement, VLBI Citation: Li J L, Guo L, Qian Z H, et al. Determination of the controlled landing trajectory of Chang'E-1 satellite and the coordinate analysis of the landing point on the Moon.

The Chang’E-1 orbiter plays a distinctive role in China’s first successful selenodetic lunar mission

“…The Chang'E-1 satellite was tracked by two-way range and [5][6][7]. The tracking data cited in this paper are the two-way range and range rate data from the Qingdao and Kashi stations with 1-second sampling rate.…”

“…(1) Optical Imaging System: CCD Stereo Camera/Imager (CCD); Signal-Based Interferometer Spectrometer Imager (IIM), shown in Figure 2; Additionally, the TT&C and VLBI system has contributed to the lunar exploration project by means of the radio metric science data obtained by CE-1 [5][6][7].…”

“…However, due to the expected life span of the small thrusters on the platform, the experiments were replaced by a controlled impact on Feb. 9, 2009 to ultimately terminate the mission [7].…”

Global inventory of Helium-3 in lunar regoliths estimated by a multi-channel microwave radiometer on the Chang-E 1 lunar satellite

“…This newly acquired dataset provided an opportunity to quantitatively estimate the global inventory of the 3 He accumulated in the whole regolith. Other studies on the CE-1 observations can be found in [12][13][14][15][16][17].…”

Positioning reduction in the real-time phase of Chang’E-2 satellite

“…It is the special function of the PR method to monitor the trajectory evolution of the satellite during maneuvers. By solving the time series of the coordinate and velocity and converting which into osculating orbit elements [4][5][6], the PR method is successfully applied to the rapid identification of the capture of the CE-2 satellite by the Moon. When the orbit eccentricity gradually evolves from greater than 1 to less than 1 it indicates the satellite has been successfully captured.…”