Determination of transfer function for a superconducting gravimeter at Wuhan station

The transfer function of a superconducting gravimeter was determined for the first time in China．By injecting known step-function voltages into the recording system，the transfer function of the OSG-065 (observatory superconducting gravimeter No．065) at Wuhan station was achieved．The transfer function of a superconducting gravimeter includes two parts：amplitude response and phase response (time lag)．The experimental results show that normalized amplitude responses for periods larger than 1000 s nearly equal to 1.0 and for those periods less than 1 000 s are frequency-dependent．Consequently，amplitude response for OSG is required to be determined if its recordings are used to study the signals with periods less than 1 000 s．For the OSG-065 recordings filtered by GGP1 filter and with periods larger than 4 000 s，the time lag is 10.16±0.01 s，and needs to be considered in data analysis．The accuracy for time lags estimated reaches 0.01s，which is in agreement with the global geodynamics project (GGP) requirements．For recordings with periods less than 4 000 s，the time lags are frequency-dependent and need to be considered in the signal investigation．In conclusion，the amplitude response needs to be considered when the observation signal with periods less than 1 000 s，while the phase lag needs to be considered in all periodic signals．The transfer function of Wuhan OSG-065 was determined in the study，which provides a fundamental reference for the transfer-function determination of other superconducting gravimeters in China. © 2022 Huazhong University of Science and Technology. All rights reserved.