Tracking a spacecraft that is landing on another planet or moon has historically been very difficult because radio telescopes and other methods used in the tracking process have limited precision. The Chang'e 3 lander was equipped with a camera that recorded images of the lunar surface while the craft was descending. Using some of these images, researchers associated with the Chang'e 3 mission reconstructed the trajectory taken by the Chang'e 3 lander during its descent with much better precision that what was possible using a radio telescope.

 

 

http://www.raa-journal.org/raa/index.php/raa/article/view/1937