Determination of the free lunar libration modes from ephemeris DE430

作     者：Yong-Zhang Yang Jin-Ling Li Jin-Song Ping Hideo Hanada 

作者机构：Shanghai Astronomical ObservatoryChinese Academy of SciencesShanghai 200030China National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China University of Chinese Academy of SciencesBeijing 100049China RISE ProjectNational Astronomical Observatory of JapanOshu 0230861Japan 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2017年第17卷第12期

页      面：89-94页

核心收录：

学科分类：0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 070401[理学-天体物理] 0825[工学-航空宇航科学与技术] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China(Grant No.41590851) the Major State Basic Research Development Program of China(2015CB857101) 

主　　题：Moon physical librations Fourier analysis least squares method 

摘      要：The Moon’s physical librations have been extensively studied, and elaborate researches have been developed for the purpose of deriving accurate modes of free librations. Our motivation comes from the Planetary and Lunar Ephemeris DE430 by JPL/NASA, which was created in April 2013,and is reported to be the most accurate lunar ephemeris today using the data from Gravity Recovery and Interior Laboratory（GRAIL）. Therefore, the residuals after fitting the model have reduced owing to improvement in the libration models, and the free librations embedded in the Euler angles have also improved. We use Fourier analysis to extract the approximate frequencies from DE430 and then a quadratic interpolation method is used to determine higher accuracy frequencies. With the frequencies,the linear least-squares fitting method is employed to fit the lunar physical librations to DE430. From this analysis we identified the three modes of free physical librations, and estimated the amplitudes as 1.471′′in longitude, 0.025′′in latitude and 8.19′′× 3.31′′for the wobble, with the respective periods of1056.16, 8806.9 and 27262.99 d. Since the free librations damp with time, they require recent excitation or a continuous stimulating mechanism in order to sustain.