Estimation of Earth rotation parameters from Lunar Laser Ranging data

In addition to Very Long Baseline Interferometry (VLBI) the Earth rotation phase ∆UT1 can also be determined directly from Lunar Laser Ranging (LLR) data. With the other Earth Orientation Parameters (EOP) like terrestrial pole coordinates and nutation parameters, the determination of a full set of EOP is possible from LLR observations. In recent years LLR observations have been carried out with bigger telescopes (APOLLO) and at infrared wavelength (OCA, Wettzell). This resulted in a better distribution of LLR data over the lunar orbit and retro-reflectors with a higher accuracy. The aim of our recent study is to quantify, how much the EOP determination can be improved with the new high-accurate LLR data compared to previous years and if it can then be used to validate VLBI results. First, we focus on estimating ∆UT1 and terrestrial pole coordinates from different constellations such as single or multi-station data and for a different number of normal points per night. The accuracies of the results determined from the new LLR data (after 2000.0) have significantly improved, being less than 20 µs for ∆UT1, less than 2.5 mas for x_p, and less than 3 mas for y_p for nights selected from subsets of the LLR time series which have 10 and 15 normal points obtained per night. Second, we focus on the determination of corrections of the nutation coefficients to the MHB2000 model of the IERS Conventions 2010. Here we also see significant smaller correction values and accuracies with an improvement of one order of magnitude, that means accuracies better then 0.01 mas. Recent results will be presented and discussed.

This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2123 QuantumFrontiers – 390837967.