A degree 180 spherical harmonic model for the lunar topography

Using multiple step least squares fitting method and 0.25° gridded altimetry data ( http://pds-geophys.wustl.edu/pds ) from Clementine, a lunar topography model, NLT180A, is determined complete to spherical harmone degree (n) 180 This model is compared with the GLTM2 model (70x70) and shows good agreement for the long-wavelength component (longer than n=70).Other important parameters, including the offset between the center of figure (COF) and the center of mass (COM) of the Moon, and the topographical flattening of the Moon, have also been estimated. The estimates are similar to those obtained by other researchers. Possibility to obtain higher (than n=180) degree spherical harmonic model from the Clementine gridded data is discussed.Based on NLT180A, the lunar Moho topography and crustal thickness are estimated by assuming a traditional single layered crust on the top of Moho. The method used in this article will benefit the research of the future lunar mission, SELENE ( SEL enological and EN gineering E xplorer).