Calibration of instrumental drift of superconducting gravimeter iGrav #003 by comparison with absolute gravity measurements at Zao and Fuji stations

Abstract The instrumental drift of the superconducting gravimeter iGrav (serial number 003) was calibrated by comparison with absolute gravity measurements at two different locations and with different methods. At the Zao station, absolute gravity measurements were performed once a year to estimate the drift over four years. At the Fuji station, continuous measurements of absolute gravity were performed for two months and the data were directly compared with the iGrav data. At both stations, the instrumental drift was well represented by a linear function of time, but the drift rate obtained at Fuji was approximately twice as large as that at Zao. The cause of this difference is unknown.