Laser ranging of satellites reveals unprecedented geodynamic insights and distances.
The article discusses how scientists used lasers to measure the distance to two satellites called Etalon. They did this by observing the satellites from a telescope in Shanghai. Between April and December 1990, they collected data from 73 passes of the satellites. In each pass, they recorded up to 4,256 distance measurements, with some distances being more than 20,000 kilometers.