Abstract The fundamental concept of Lageos is a long lived, dense, electrically and mechanically inert spherica satellite with its surface speckled wiht retroflecting cube corners, designed such that range measurements between duly equipped laser ground stations and the satellite are possible with an ultimate accuracey of 2 cm averaged.The Lageos concept requires that the satellite be placed in an orbit for which an ephemeris can be determined ultimately to a 5 cm rms uncertainty for a 24-hour...