The laser ranging test is a scientific measurement of the distance between the stars and the ground by laser. The principle is that a highly isotropic pulsed laser beam is directed toward a corner mirror placed on the surface of the satellite, and the distance between the stars and the ground is calculated by the time difference between transmission and reception. The farthest laser ranging test in human history is the lunar laser ranging. As you can imagine, a light is emitted from the ground observatory from the earth and flies back from the moon, and the distance between the moon and the moon is converted through one time and one time. This is a comprehensive technology covering laser, photodetection, automatic control, space orbit and other fields. It is the most accurate technical method for measuring the distance between the Earth and the Moon. Its observation data is related to astronomical geodynamics and geostrophic dynamics. Studies in many disciplines such as studies, lunar physics, and gravitational theory have important value.
The lunar laser ranging sounds very simple, and there is no novelty in the concept. However, if you really want to use technology to express it, it will be much more difficult.
First, from the perspective of traditional technology, the main difficulty of lunar laser ranging is the laser emission and laser receiving conversion in the common optical path system. It is necessary to ensure that the system can normally emit laser light and receive echo signals.
The second is the telescope tracking pointing accuracy. When the telescope has a pointing accuracy of 3 seconds, the distance between the center of the laser beam and the lunar reflector is up to 6 kilometers when pointing to the moon, and the largest lunar reflector - Apollo 15 The effective reflection area is only 3402 square centimeters, which will directly affect the success of laser moon survey.
The third is the laser beam quality and optical system efficiency, which affects the actual emission energy and quality of the laser. This requires the production technology of the laser emitting device to be very high.