Dynamic precision measurement of gravity field is of great significance to the fields of geological surveying, resource exploration, and autonomous navigation now. Current dynamic gravity measurements remain relative, thereby facing the drawbacks of accuracy calibration and measurement value drift of instruments. Operation of the absolute gravimeters in dynamic measurement could solve these problems. Whereas, during the measurement of absolute gravity in a dynamic environment, the interference and coupling of the dynamic environment is an important issue to research urgently. In this paper, we report the new progress on our homemade marine survey system of absolute gravity, and the experimental improvements are introduced compared with the previous system. Furthermore, experiments of marine gravity surveys campaign are carried out in the Yellow Sea of China. The cross-over tracks and repeated survey lines are designed in order to evaluate the performance. The internal coincidence precision of our marine survey system is estimated to be 1.22 mGal and the results are also in good agreement with the reference data measured by the relative gravimeter, and an external coincidence accuracy of 1.62 mGal is obtained. Finally, methods of data processing are given in great detail and the surveyed results are compared with satellite gravity data and the data from the shipborne relative gravimeter. Our results may be helpful for the development of marine absolute gravimeters and the actual shipborne surveys of absolute gravity.

This paper presents a unimorph deformable mirror intended to be used as secondary corrector in space telescopes. The deformable mirror consists of a single-crystal silicon wafer (76.2 mm diameter, 500 μm thickness) covered with an optical coating on the front side and an array of 25 independent piezoelectric transducer (PZT) actuators acting in $d_{31}$ mode on the back side. The mirror is mounted on an isostatic support with three position linear actuators controlling the rigid-body motion. The first part of the paper presents the experimental results obtained with the manufactured prototype. The mirror was tested in terms of root mean square (RMS) wavefront error, open-loop long-term stability, voltage budget for active control, rigid-body actuation, reflectivity, and dynamic response. The prototype is fully compliant with the requirements set by the European Space Agency (ESA). The second part of the paper, purely based on numerical simulations, presents a robust way to face thermal distortion, inherent to unimorph architecture.

This paper presents the technology to control the shape of thin polymer doubly curved shell structures with a unimorph layer of strain actuators to achieve high quality, light-weight, foldable space reflectors. The selected active material is PVDF-TrFE deposited by spin coating; it is electrostrictive, isotropic and enjoys an excellent piezoelectric coefficient $d_{31}\simeq 15$ pC/N when properly annealed, but has a nonlinear, quadratic behavior. The strain actuation is controlled by an array of segmented electrodes. The purpose of this study is to evaluate the material properties achieved in the manufacturing process. A simple, unidirectional model of electrostrictive material is considered and the material constants (electrostrictive constant $Q_{33}$ , piezoelectric constant $d_{31}$ , spontaneous polarization $P_s$ and poling strain $S_P$ ) are estimated from various static and dynamic experiments. The final part of the paper illustrates the control authority on a small demonstrator with seven independent electrodes and compares the experimental results with numerical finite element simulations.

动态重力测量可以提高重力场的勘测效率, 对基础地质调查、资源勘探、地球物理研究等具有十分重要意义. 本文基于冷原子重力仪、惯性稳定平台和牵引动力装置搭建了一套绝对重力动态移动测量系统, 并开展了绝对重力动态测量实验. 首先测量了不同牵引速度下的垂向振动噪声功率谱, 理论分析了其对动态重力测量的影响; 其次评估了不同牵引速度对原子干涉条纹对比度和直流偏置量的影响, 分析了动态环境下的振动补偿效果; 在最大牵引速度为5.50 cm/s、最大振动幅度为0.1 m/s²的情况下, 实验上仍能基于振动补偿技术恢复原子干涉条纹. 在此基础上, 通过开展不同T下的原子干涉条纹测量, 评估了动态测量环境下的绝对重力值, 在校正完系统误差并减去绝对重力初始值后得到的测量结果为(–1.22 ± 2.42) mGal (1 Gal = 0.01 m/s²). 最后, 通过与静态环境下的绝对重力测量值进行比较, 发现两者基本吻合. 本文开展的绝对重力动态移动测量实验有望为车载动态绝对重力测量提供数据参考.