A Differential Orbit Improvement Program for Lunar Orbiter

Abstract

The Smithsonian Astrophysical Observatory plans to expand the Differential Orbit Improvement program to determine lunar orbits as well. The orbits will be determined in a moon-fixed selenocentric reference system. Observations of directions, ranges, and ranger-rate (Doppler) from the Earth’s surface as well as from the Moon’s surface will be used. It is planned that observations of lunar satellites from a moon-fixed station will also be used. An ephemeris for the Moon will have to be given, but additional correction to those ephemerides will be determined the same way as correction to the observing station’s coordinates are determined with earth satellites. The use of the phenomenological approach that has been so successful for earth satellites will have many advantages in the determination of selenocentric orbits, at least for the beginning of the lunar satellite era.