Optimized strategy for the calibration of superconducting gravimeters at the one per mille level

This paper reports on different sources of errorsthat occur in the calibration process of a superconductinggravimeter (SG), determined by comparison with a ballisticabsolute gravimeter (AG); some of them have never been discussedin the literature.We then provide methods to mitigatethe impact of those errors, to achieve a robust calibrationestimate at the 1 0/00 level. We demonstrate that a standarddeviation at the level of 1 0/00 can be reached within 48 h bymeasuring at spring tides and by increasing the AG samplingrate. This is much shorter than what is classically reportedin previous empirical studies. Measuring more than 5 daysaround a tidal extreme does not improve the precision in the calibration factor significantly, as the variation in the error asa function of 1/√ N does not apply, considering the decrease in signal amplitude due to the tidal modulation. However, weinvestigate the precision improvement up to 120 days, which can be useful if an AG is run continuously: at mid-latitudeit would require 21 days to ensure a calibration factor at the 1 0/00 level with a 99.7 % confidence interval. We also showthat restricting the AG measurement periods to tidal extremacan reduce instrument demand, while this does not affectthe precision on the calibration factor significantly. Then, we quantify the effect of high microseismic noise causingaliasing in the AG time series. We eventually discuss the attenuation bias that might be induced by noisy time seriesof the SG. When experiments are performed at the 1 0/00 level, 7 are needed to ensure that the error in the calibration estimatewill be at the 1 per mille level with a 99 % confidence