Spectral analysis of earth orientation results from Doppler tracking of the Navy Navigation Satellite System

Abstract

Doppler tracking of the Navy Navigation Satellite System (NNSS) gives solutions for polar motion as a by-product of the orbital computation process. The polar motion estimation process at the Defense Mapping Agency is reviewed and comparisons of the Doppler results with the polar motion series of the newer techniques, Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI), and the Bureau International de l'Heure (BIR) Circular-Dare made. TwoChandler periods of data are analyzed beginning with the start of the Main MERIT Campaign in September 1983.

The two major components, annual and Chandler wobble, are removed. The resulting residuals, as well as those obtained by differencing all combinations of Doppler series and the three reference series, are smoothed by different techniques. The 'seven-point moving average' and the Vondrak smoothing algorithm are the two smoothers applied. A computational spectral analysis is presented that determines which periods dominate the residuals.