The Lunar Orbiter Laser Altimeter (LOLA) works by propagating a single laser pulse through a Diffractive Optical Element that splits it into five beams. These beams then strike and are backscattered from the lunar surface. From the return pulse, the LOLA electronics determine the time of flight which, accounting for the speed of light, provides a precise measurement of the range from the spacecraft to the lunar surface. These range measurements, combined with accurate tracking of the spacecraft's location, are used to build a map revealing the contours of the lunar landscape.
This animation illustrates the dramatic improvement in our knowledge of the Moon's terrain made possible by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. A LOLA digital elevation map compiled in late 2009 is compared to the Unified Lunar Control Network (ULCN) 2005, a painstakingly constructed map based on the best available data at the time, including imagery from the Clementine, Apollo, Mariner 10, and Galileo missions as well as Earth-based observations.
A natural color view centered on the Apollo 15 landing site near Hadley Rille. The large dark circular areas are Mare Imbrium (left) and Mare Serenitatis (right). Note the many wrinkle ridges, or dorsa, in the otherwise smooth Serenitatis. The mountain range curving toward the lower left is the Apennines. The one to the north of it is the Caucasus. The bright crater in the lower left is Copernicus.
A natural color view at a high northern latitude. Imbrium and Serenitatis are at the bottom of the frame. The large dark spot near the north pole is the crater Rozhdestvenskiy. Below it along the terminator are Peary and Byrd, craters named for explorers of the Earth's poles.