Lunar Ephemeris Parameters for the EPM2023a

Abstract

Since 1969, the Lunar Laser Ranging (LLR) technique has been used to build and improve the ephemeris of the Moon. The results of processing of new laser observations are considered here to determine more accurately the lunar ephemeris parameters for the Ephemeris of Planets and the Moon (version EPM2023a), which was created and is maintained by the Institute of Applied Astronomy of the Russian Academy of Sciences. In 2014, the development of a new version of the EPM (including the Moon) started within the upgraded ERA-8 system (where ERA stands for Ephemeris Research in Astronomy). The new version of the lunar ephemeris implements a model of the orbital–rotational motion of the Moon that is similar to that used in the DE430 version of the NASA JPL Development Ephemerides. In this model, the Moon is considered as an elastic body with a rotating liquid core, and the rotation of the Moon around its center of mass in the celestial coordinate system is described by three Euler angles. Together with new geophysical and geodynamic parameters required today, this model replaced the model proposed by G.A. Krasinsky in the ERA-7 system. In this paper, to obtain the lunar ephemeris parameters for the EPM2023a, we use 33 602 Lunar Laser Ranging observations (LLRos; i.e., normal points), including 1985 new observations. About 100 lunar ephemeris parameters of the EPM2023a were improved, and some of them were compared to the corresponding parameters of the INPOP21a (where INPOP stands for Integration Numerique Planetaire de l’Observatoire de Paris) and DE440 ephemerides. For current projects and practical work in space research, it is necessary to use the latest lunar ephemerides—EPM2022a and EPM2023a.