Continuous Gravity Observation with the Superconducting Gravimeter CT #043 at Syowa Station, Antarctica

In April 2003, a new superconducting gravimeter CT #043 was installed at gravity observation hut in Syowa Station and TT-70 #016 was replaced with CT #043 at the end of 2003. Before the removal of the TT-70 #016, parallel observation with CT #043 and TT-70 #016 was carried out during the period from April 18 to November 4. A tidal analysis program BAYTAP-G was applied to the output signals from the both gravimeters for harmonic analysis, and tidal amplitude factors, phases and residuals were computed. Large instrumental drift over 200 μGal per year was observed in CT #043 record, but the drift could be eliminated accurately by fitting an exponential decaying function of first order. Tidal amplitudes and phases obtained from the both gravimeters data during the parallel observation period are in good agreement with each other. The detided gravity residuals agree both in variation pattern and amplitudes of the variation. This fact means reliability of the observation by CT #043 and adequacy of the manner to eliminate the instrumental drift. Tidal factors from CT #043 data after January 2004 were also compared with those obtained by previous studies using TT-70 #016 data, and they coincided with each other. From comparison of the gravity residuals from January through December 2004 with sea level trend, the obtained response coefficient to sea level change is about 0.07 μGal/cm.