Spectra of rapid oscillations of earth rotation parameters determined during the CONT02 campaign

Over the two weeks of the CONT02 campaign in October 2002 the Earth rotation parameters (ERP) were determined with a resolution of one hour by VLBI and also by GPS. Analyses of these two very precise polar motion and UT1-UTC series reveal oscillations with periods of 8 hours and 6 hours. Their detection independently by two accurate space geodetic techniques is a first evidence for a real sub-semidiurnal variation of the ERP. On the other hand the oscillations might still be an artefact stemming from similar methods of data sampling or from un-recovered diurnal drifts in the time series. Additionally, polar motion excitation functions were computed from the VLBI and GPS data series and analyzed in order to estimate the power necessary to excite rapid polar motion. The Atmospheric Angular Momentum (AAM) and Oceanic Angular Momentum (OAM) data series with high time resolution were used in the analyses, too. Time variable spectra of rapid polar motion oscillations and their excitation functions were computed by the Fourier Transform Band Pass Filter, showing time variations of the amplitudes of these oscillations.