Moon-Earth Yardstick--The Laser Ranging Retro Reflector is an array of precision optical reflectors that will serve as a target for Earth-based laser systems. The reflector will allow precise measurement of the Earth-Moon distance, wobble of the Earth's rotation, measurement of gravity influences, and measurements of mass distribution in the Moon. It will also provide an opportunity to study whether continents drift on the surface of the Earth. Developed for the National Aeronautics and Space Administration, it will be carried abroad Apollo 11, the United States first manned lunar landing.