An analysis of the homogeneous ILS polar motion series

Abstract

Summary A new reduction of the International Latitude Service Observations for the years 1899–1977 has recently been completed under the direction of Dr S. Yumi and the International Astronomical Union Commission 19. This paper examines the annual, Chandler frequency, and long period motion of the Earth's pole implied by this new homogeneous data set. The estimated annual polar motion differs slightly from earlier results. The new value for the Chandler frequency is also very close to earlier results, but the estimated Q is somewhat larger, as might be expected by a reduction in noise level. Analysis of the long period motion shows an apparent drift and, in agreement with earlier studies using other data, there is some evidence of an approximately 30-yr oscillation in the pole position.