Precise Observation of the Secular-Gravity Changes by means of the combination of Absolute and Superconducting Gravimeters.

为了获得与GRACE等卫星重力资料比较所需的高精度重力变化数据集，我们研究了超导重力测量与绝对重力测量相联合收割机的实用方法，并提高了各自的测量精度，为此，我们在日本京都、江志、松代和印度尼西亚万隆等观测站继续进行了超导重力观测。我们还开始了地下水测量，以揭示其重力效应在京都和万隆站：结果表明，地下水的变化和重力观测，特别是在万隆站之间有明显的相关性。我们证实，重力测量的精度提高，通过消除地下水的影响。我们进行了几个绝对重力测量平行于超导观测在江ashi和松希罗站在2000年和2001年，以及京都站，定期进行绝对测量。两个观测站的观测总时间超过一个月，足以进行比较。此外，我们还发展了一种新的数据处理方法，最终得到了非常精确的超导重力仪刻度因子。为了保证绝对重力测量的准确性，调整和验证是非常重要的。我们与地理测量所合作，进行了绝对重力仪之间的比较。除了实际测量外，我们还对卫星重力使命数据和地面测量数据进行了模拟研究，并建立了未来利用这些数据集的基本技术。

To obtain so accurate data sets of gravity variations as to be used for the comparison with the satellite gravity data such as GRACE, we studied practical methods to combine superconducting and absolute gravity measurements as well as to improve the accuracies of the individual measurements.For this purpose, we have continued superconducting gravity observations at the observation stations of Kyoto, Esashi, Matsushiro in Japan and Bandung in Indonesia. We also started groundwater measurements to reveal their gravity effects at Kyoto and Bandung stations: The results show a clear correlation between the groundwater variations and the gravity observations, especially at the Bandung station. We confirmed that the accuracy of the gravity measurements are improved by removing the groundwater effects.We carried out several absolute gravity measurements in parallel with the superconducting observations at the Esashi and Matsusiro stations in 2000 and 2001 as well as the Kyoto stations where absolute measurements are periodically conducted. The total observation, time in both stations exceeded more than one month which is long enough for purpose of comparison. Moreover, we developed a new method for the data processing, we finally obtained very precise calibration factors for the superconducting gravimeters. We also determined reference gravity values for future studies of secular gravity changes at the stations.To maintain the accurate absolute gravity measurements, adjustments and validations are very important. We carried out the comparison between the absolute gravity meters in collaboration with Geographical Survey Institute. The comparison also contributed to accumulate the know how of the absolute gravity measurements.In addition to the actual measurements, we also conducted several simulation studies of satellite gravity mission data and ground base measurements, and we established the basic techniques of future utilization of those data sets.