船载系泊状态下基于原子重力仪的绝对重力测量

Absolute gravity measurement based on atomic gravimeter under mooring state of a ship

重力场是反映地球质量分布及变化的重要参数,动态重力测量在地质调查、地球物理、资源勘探等领域有着重要应用.目前动态重力测量均基于相对测量原理,动态相对重力仪存在零点漂移问题,影响其测量性能.动态绝对重力仪可以为相对重力仪提供同步同址校准,解决其长漂问题,因此备受关注.本文基于原子重力仪和惯性稳定平台,搭建了一套船载绝对重力动态测量系统,并在船载系泊状态下开展了绝对重力动态测量实验.经评估,船载系泊环境下的重力测量灵敏度为16.6 mGal/Hz^-1/2,1000 s积分时间内重力测量的分辨率可达0.7 mGal.通过两周的绝对重力测量,评估了系统的稳定性.为了评估绝对重力的动态测量精度,将船上测量点与码头高精度绝对重力基准点的绝对重力值进行了比较,两点之间的绝对重力值差及其不确定度评估结果为(–0.072±0.134)mGal.本文结果为海洋相对重力仪的同时同船校准提供了一种新方案.

The gravity field is one of the basic physical fields of the Earth.Dynamic measurements could improve the efficiency of gravity surveying and mapping,and have very important applications in the fields of geological survey,geophysics,resource exploration,inertial navigation and so on.Currently,dynamic gravity measurements are mostly based on relative measurements.The dynamic relative gravimeters have the problem of zero drift,which affects the measurement performance.Dynamic absolute gravimeters can provide synchronous and co-site calibration for relative gravimeters and solve the problem of long drift.Therefore dynamic absolute gravimeters have attracted much attention.Based on a homemade atomic gravimeter and an inertial stable platform,a system of absolute gravity dynamic measurement has been built on a ship.The dynamic measurement experiments of absolute gravity under the state of ship-borne mooring have been carried out.It is found that the frequency of vibration noises of this ship is around 0.2 Hz,and the amplitude is about 1 Gal.In the case of harsh environment,the temperature and humidity of the used container have been controlled to be 25℃and 70%via the air conditioning.Then,a continuous gravity measurement of 5 hour has been taken,and the peak to peak value of 80 mGal has been achieved.The values of gravity have no drifts at all during the measurements.Besides,the sensitivity of gravity measurement has been evaluated to be 16.6 mGal/Hz^-1/2 under the environment of ship-borne mooring.A resolution of 0.7 mGal could be reached with an integration time of 1000 s.The stability of this system has been estimated after the measurement of absolute gravity for two weeks,and the change of absolute gravity values is about 0.5 mGal.Finally,in order to evaluate the accuracy of the dynamic measurement of absolute gravity,the measured average value of absolute gravity at ship-borne has been compared with the value of the high-precision absolute gravity reference point of the pier,and the results are estimated to be(–0.072±0.134)mGal.The results of this paper could provide a new solution for the simultaneous and co-site calibration of the ocean relative gravimeter on the same ship.