Knowledge Bank

Based on the analysis of the polar motion behavior, we found the possibility of predicting polar motion up to one year in advance. Comparing these predicted polar coordinates with the observed ones (smoothed), the rms of the differences is about 0."02. The differences of the relative polar motion are much smaller. For any time interval of 20 - 30 days throughout the whole year, the rms of the relative polar motion differences is about 0."01. Compared with the best available VLBI results (from 1977 to 1980), the rms of (pred. - obs.) is 0."013, and the relative rms (for time intervals less than two months) is 0.008 (here the observed data is unsmoothed). It appears that 80 - 90% of the polar motion is composed of the stable, predictable Chandler and annual terms. UT1-UTC has more complicated changes than polar motion making it difficult to find a satisfactory method of long-term prediction. So far the rms prediction error is 0.s0023 for up to 30 days. [Some mathematical expressions are not fully represented in the metadata. Full text of abstract available in document.]