RESULTS OF 3 YEAR OBSERVATION WITH A SUPERCONDUCTING GRAVIMETER AT THE GEOFORSCHUNGSZENTRUM POTSDAM

The superconducting gravimeter (SG) TT70 has been continuously recordi ng gravity data at the GeoForschungsZentrum (GFZ) Potsdam absolute gra vity site since July 1992. The recorded data are edited and preprocess ed by spike and step detection and elimination and gap filling. An atm ospheric pressure correction is carried out on gravity data in the tim e domain with a complex admittance before tidal fitting. The atmospher ic pressure admittance is calculated from tide free output of SG data and local atmospheric pressure using the cross spectral method. The gr ound water level admittance is determined by a single coefficient. Imp rovements with these corrections are shown in analysis results. New ti dal parameters for Potsdam site are determined and compared with recor dings of an Askania spring gravimeter at a nearby site. Deviations aga inst the Wahr-Dehant-model are shown. Polar motion data of the IERS (I nternational Earth Rotation Service, Paris) are used to calculate vari ations of centrifugal acceleration caused by polar motion (pole tide). These are compared with the corrected tide free output of SG series. For drift determination the polar motion correction is applied on SG d ata. The nutation period equivalent to the Earth's Nearly Diurnal Free Wobble is calculated from the SG data with a value of T-FCN = (437.4 +/- 1.5) sidereal days. This result is compared with those obtained fr om other SG stations.