A Note on the Physical Parameters of the Moon

Using the Stokes coefficients of the Moon recommended by IERS Standards (1992), we determined the expression of lunar equipotential surface (selenoid), then calculated the parameters of best-fitting lunar ellipsoid. Moreover, we derived a set of hydrostatic values of lunar physical parameters by solving the Clairaut equation, and discussed the feature of nonhydrostatic component in the figure parameters of the Moon. Finally, we suggest that the lunar physical parameters should be divided into three kinds: primary constants, derived constants, and estimated constants (see Table III); as well that the second-degree Love number,k ₂, of the Moon should belong to the estimated constants. At present, in view of the accuracy in reductions of LLR data, a value ofk ₂ obtained from model calculations should be defined as its adopted value. For example, the value ofk ₂, 0.0266, in this paper can replace 0.0222 in IERS Standards (1992).