Shape of the Moon from the Orbiter Determination of its Gravitational Field

Abstract

AN analysis of the perturbations of the American Orbiter 1, revolving since August 14 in a 200 min orbit close to the Moon, has led to a satisfactory determination of the principal characteristics of the lunar gravitational field¹, and it is of interest to compare these with previous predictions based on plausible physical assumptions. In a previous investigation² one of us predicted the coefficients of a harmonic expansion of the lunar gravitational potential on the assumption that the mass of the Moon is distributed homogeneously. The volume of the Moon is defined by a surface obtained from the hypsometric data of the Aeronautical Chart and Information Centre of the U.S. Air Force³. We believe these data to be the best available at the present time, because the use of high-resolution sequential photographs from Pic du Midi enabled the ACIC investigators to minimize the atmospheric effects, which are the principal source of errors.