McDonald Uto Results and Implications for the Erold Campaign
Single-day results on UTO at the McDonald Observatory have been obtained on a large number of days when the observations covered an hour angle range of at least three hours. For data through November 1974, the median accuracy was 0.5 msec without allowance for uncertainty in the lunar orbit orientation, or 0.7 msec including this error source. It has been found that the lunar range results agree better with a strongly smoothed version of the BIH results than with the raw 5-day values. Also, the RMS fluctuations of the single-day lunar laser ranging results with respect to the strongly smoothed BIH values was only 0.7 msec when the mean difference for each lunation was removed. Thus, the majority of the short-period fluctuations in the BIH raw values during the period covered by our data probably are not due to real changes in the Earth’s rotation. This tentative conclusion suggests that short-period torques on the Earth’s mantle and crust may be small at most times. The dependence of the desirable averaging times for UTl and polar motion during the EROLD campaign on the assumed power spectrum of fluctuations in these quantities was discussed.