Estimate of Four Topocentric Lunar Radii

Abstract

The Ranger lunar probes (6, 7, 8, and 9) which impacted the Moon at free flight velocities were tracked by three earth-based stations. These stations obtained accurate recordings of impact times and also range rate measurements for many hours prior to and within seconds of impact. Using this data, estimates of the dynamical center from four lunar surface points were determined. The range rate data determined the orbit relative to the tri-axial Moon and the recording of impact time triggered the proper radius vector (i.e., the selenocentric radius vector at the recorded time of impact, accounting for signal transit times).

This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.