The secular acceleration of the Moon determined from lunar laser ranging data

Lunar Laser Ranging data covering the interval from August 1969 to December 1987 were used to determine the seculer acceleration in the mean longitude of the Moon (\.n). In our analysis, the DE200/LE200 planets and lunar ephemerides were adopted for calculating the theoretical distance between the observing station and reflector. The method of stepwise regression was used in the processing of the data and the value of –25.4 ± 0. 1/cy² was obtained by a weighted least squares fit.Our result is in good agreement with that derived by other authors using various methods. The uncertainty (\.n) estimated from LLR data would be decreasing rapidly with increasing the data span. The high precision obtained in this paper is mainly due to the longer span and higher measuring accuracy of data.