Lunar Time Ephemeris LTE440: User Manual

TL;DR

The LTE440 lunar time ephemeris provides a precise numerical model for transforming between Lunar Coordinate Time and other barycentric time scales, based on IAU 2024 standards, with picosecond accuracy and detailed secular and periodic drift estimates.

Contribution

This paper introduces LTE440, a new lunar time ephemeris aligned with IAU 2024 standards, offering high-precision time transformations and comprehensive drift analysis.

Findings

Secular drifts between TCL and TDB/TCB are quantified.

Periodic terms with amplitudes of hundreds of microseconds are identified.

LTE440 achieves precision at the level of several picoseconds.

Abstract

We present the numerical lunar time ephemeris LTE440 based on the definition of Lunar Coordinate Time (TCL) given by the International Astronomical Union (IAU) in IAU 2024 Resolution II. LTE440 can be used to obtain the numerical transformation between TCL and Solar System Barycentric Dynamical Time (TCL-TDB) or Solar System Barycentric Coordinate Time (TCL-TCB). The theoretical model, numerical method, and performance of LTE440 are discussed. The secular drifts between TCL and TDB and between TCL and TCB are respectively estimated as $\left< d\mathrm{TCL}/d\mathrm{TDB}\right>=1+6.798\,355\,238\times10^{-10}$, and $\left< d\mathrm{TCL}/d\mathrm{TCB}\right>=1-1.482\,536\,216\,67\times10^{-8}$. The most significant periodic terms have amplitudes of about 1651 microseconds for the annual term and 126 microseconds for the monthly term. The precision of LTE440 is estimated to be at the level of several picoseconds. LTE440 is freely available at https://github.com/xlucn/LTE440.