Earth Rotation Study Using Lunar Laser Ranging Data

Abstract

Values of UTO derived from lunar laser ranging data have been compared with BIH circular D, 5 day smoothed values on over 300 days during 5 years. A prominent annual term of 2.0 ms amplitude is the dominant systematic difference. After removing the annual term, a drift, and theoretical tidal terms, the UTO differences have an rms value of 1.5 ms. Spectra of these differences show that most of the power occurs at periods of four months or longer. Several spectral peaks may be significant and variations with timescales longer than 5 years are probable. There appears to be little power in the rotation of the earth at periods short compared to a month except that due to tidal terms. Over the 5 yr span we estimate the rms error in BIH circular D, 5 day smoothed values of UT1 to be 2.0 ms while for polar motion a 0.30 m error is obtained. With the annual term removed the UT1 error is reduced to 1.4 ms.