Measurement of the Newtonian gravitational constant based on the principle of free fall

The Newtonian gravitational constant (G) is one of the fundamental physical constants. This paper introduces a method to determine the Newtonian gravitational constant based on the principle of free fall, through measuring the change of gravity from the disturbed mass with an FG5/112 absolute gravimeter. This method has good repeatability. The measurement precision can be improved by error control and a large number of experiments. The constant G is obtained by two experiments, and the measured value is (6.6665±0.0554)×10⁻¹¹ m³/(kg·s²). Supported by the National Basic Research Program of China (Grant No. 2003CB716300) and Key Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-125)     

Trend of China land water storage redistribution at medi- and large-spatial scales in recent five years by satellite gravity observations

The GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission has provided a new method to study land water mass redistribution at medi- and long-spatial scales in recent years. We estimate continental water mass redistribution in China using GRACE observations during 2003 to 2007. The results show some large regions with increase or decrease of land water mass storage in the central northern region, Tibetan Plateau, the Three Gorges region, the place where Qinghai, Sichuan and Gansu provinces meet, and the Altun Mountains region in the Xinjiang Uygur Autonomous Region. In the first two regions, it is obvious that water (ice) mass storages are decreasing. Water mass in the central northern region decreases at a linear rate of 2.4 cm/a equivalent water height, equal to 5.2 billion cubic meters per year during the five years’ period, and water mass depletion in Hebei Province is ∼ 4.5 billion cubic meters per year in the same period, which is consistent with the average water mass depletion of 4.0 billion cubic meters per year of overused underground water in the recent 30 years estimated by Hebei Province Water Resources Bureau. Furthermore, GRACE can detect the water mass accumulation of ∼ 5 cm equivalent water height within the region spreading over about 0.12 million square kilometers due to the Three Gorges dam construction in June 2003. We also find a water mass gain of ∼ 1.1 cm/a in the areas where Qinghai, Sichuan and Gansu provinces meet. This indicates that the climate of these regions has been becoming gradually humid in recent years. Supported by Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-202), National Natural Science Foundation of China (Grant No. 40674038), and Program of Key Laboratory of Space Environment and Geodesy of Ministry of Education of China     

弹性地球CIP轴的极移和岁差章动

基于经典的弹性地球自转动力学理论,通过引入章动参考系相对惯性空间的运动,建立了弹性地球极移和章动的联合动力学方程。由此对 CIP 轴进行了理论定义,并给出了其极移、岁差章动的动力学方程。在顾及到 5 阶引潮力矩的情况下,给出了 CIP 轴的岁差章动的解析表达式。理论研究表明,奇数阶岁差章动力矩使得黄经章动和交角章动出现了异向项（即黄经章动出现了 cos 项,交角章动出现了 sin 项）,同时也证明了岁差表达式与地球模型无关。得出的理论可为动力大地测量学和天文地球动力学的研究提供理论参考和依据。