Abstract
Atom interferometry provides an important method of high-precision absolute gravity measurement. As absolute gravimeters, various systematic errors of atom gravimeters have been identified ...and evaluated. Here a comprehensive evaluation of systematic errors for a transportable atom gravimeter Huazhong University of Science and Technology-Quantum Gravimeter (HUST-QG) is presented. HUST-QG exhibited a short-term sensitivity of 24 μGal Hz
−1/2
and a combined uncertainty of 3 μGal. The operation and evaluation of HUST-QG for transportable gravity measurements during the 10th International Comparison of Absolute Gravimeters are discussed. And the degree of equivalence for HUST-QG in this comparison is 1.3 μGal, which supports our evaluation.
We design and implement a compact 85Rb atom gravimeter (AG). The diameter of the sensor head is 35 cm and the height is 65 cm; the optical and electronic systems are installed in four standard 3U ...cabinets. The measurement accuracy of this AG is improved by suppress laser crosstalk and light shift. In addition, the angle of the Raman laser reflector is adjusted and locked, and the attitude of the sensing head is automatically adjusted, and the vibration noise is also compensated. The comparison measurement results between this AG and the superconducting gravimeter indicate that its long-term stability is 0.65 μGal @50000 s.
The paper analyzes the development of strapdown inertial airborne gravimeters, which have significant advantages over gyrostabilized gravimeters in terms of size, power consumption and cost and ...substantially expand the capabilities of gravity survey. Technical solutions are described that make implementation of strapdown airborne gravimeters possible. The trends in their development are discussed, including integration of data from strapdown and gyrostabilized gravimeters.
Shipborne atomic gravimeter (SAG) is an instrument that can directly measure absolute gravity in dynamic environments. As a new type of gravity sensor, a standard method for evaluating its detailed ...performance has not been proposed and the detailed performance of SAG was rarely reported. In this paper, a system of dynamic gravity measurement, which was integrated with a home-made atomic gravimeter, is demonstrated, and a novel and simple method for testing the performance of SAG on the lake based on the modulated Coriolis effect is put forward. Firstly, in the state of ship mooring, a tilt modulation of the gravity sensor has been realized to make sure the Raman wave vector is parallel to the gravity axis. Moreover, a comparison between the measurement result of CG-5 and SAG has also been carried out to evaluate the accuracy of the SAG. Then, the Coriolis effect modulating experiment is carried out with various routes on lake to test its performance in dynamic environments. In the ship mooring state, the accuracy has been demonstrated to be 0.643 mGal. The internal consistency reliabilities are evaluated to be 0.8 mGal and 1.2 mGal under the conditions of straight line and circle navigation, respectively.
In a context of global change and increasing anthropic pressure on the environment, monitoring the Earth system and its evolution has become one of the key missions of geosciences. Geodesy is the ...geoscience that measures the geometric shape of the Earth, its orientation in space, and gravity field. Time‐variable gravity, because of its high accuracy, can be used to build an enhanced picture and understanding of the changing Earth. Ground‐based gravimetry can determine the change in gravity related to the Earth rotation fluctuation, to celestial body and Earth attractions, to the mass in the direct vicinity of the instruments, and to vertical displacement of the instrument itself on the ground. In this paper, we review the geophysical questions that can be addressed by ground gravimeters used to monitor time‐variable gravity. This is done in relation to the instrumental characteristics, noise sources, and good practices. We also discuss the next challenges to be met by ground gravimetry, the place that terrestrial gravimetry should hold in the Earth observation system, and perspectives and recommendations about the future of ground gravity instrumentation.
Plain Language Summary
In a context of global change and increased human vulnerability to terrestrial hazard, monitoring the Earth system is one of the key challenges of geoscience. In particular, terrestrial gravimetry, with its precision at the level of one part of a billion, allows the monitoring of many phenomena, from water resource availability to volcanic activity. This paper reviews the technique, its advantages and limitations, how it has been used in the Earth monitoring, and the next challenges to be met by ground gravimetry.
Key Points
Review of the geophysical phenomena that can be addressed by terrestrial time‐variable gravity
The next challenges of terrestrial gravimetry are discussed
Terrestrial gravimetry remains central in the Earth observation system
Atom gravimeter (AG) is a kind of high-precision absolute gravimeter based on atom interference, which can measure absolute gravitational acceleration. Vibration is one of the important factors which ...limits the measurement accuracy. Vibration compensation is an effective method to reduce the impact of vibration on measurement accuracy and it is especially suitable for complex vibration environments. In this paper, an improved vibration compensation method is proposed. Based on the simplified model of vibration transfer function, the method searches for the optimal parameters through an improved chaotic sparrow search algorithm (CSSA) to effectively restore the real vibration of the Raman mirror and achieve the best compensation effect. The experimental results show that the improved method proposed in this paper can achieve better compensation effectiveness in less calculation time than the previous methods. The modified atom interference fringe fitting uncertainty can attenuate by 70.21%, and the search time is reduced by nearly 6 times, effectively improves the accuracy and stability of the AG measurement. This method can correct the interference fringes in time when the environment changes, which provides a new idea for the design of vibration compensation method considering dynamic gravimetry with AG.
The National Institute of Metrology, China, successfully organized the 10th International Comparison of Absolute Gravimeters in its Changping Campus in 2017 (ICAG-2017). The ICAG-2017 is registered ...as the CCM.G-K2.2017 Key Comparison (KC) and Pilot Study (PS) in the frame of CIPM Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM-MRA). KC instrument belongs to an institute of National Metrology Institutes (NMIs) or its Designated Institute (DIs). PS instrument belongs to an institute that is not listed as NMI or DI. The comparison allows the determination of the degree of equivalence of national standards for free-fall acceleration measurement and ensures the consistency of the participating results with their declared uncertainties. This is the first time that such a comparison has been organized outside of the European continent and establishes a new absolute gravimeter international comparison site in China. With the participation of 13 KC gravimeters, it is also the largest comparison up to now. In parallel, a pilot study was also conducted which allowed the participation of 17 PS gravimeters including several atomic gravimeters. For the KC part of ICAG-2017, the results have already been published on “Metrologia” (Volume 57,07,002). This paper presents the results of the PS part of ICAG-2017 in which 15 of the 17 gravimeters are in equivalence.
In the Province of San Juan, Argentina, high precision geodetic instruments are operated whose observations must be corrected to compensate for the effects of the Earth's tides. Currently, this can ...be done using the parameters predicted either by theoretical models or local parameters determined by in situ observations. This work reports the results of the analysis of San Juan's tide records acquired with a spring vertical gravimeter (Scintrex CG5). The success of the use of spring relative gravity data in tidal analysis depends on accurate calibration and the proper removal of the instrumental drift from the gravimeter. The instrumental drift of the different registry segments was modeled by polynomial functions. The amplitude calibration factor of the gravimeter was determined by simultaneous gravity measurements with an SG038 superconductor gravimeter, then analyzed in the time and frequency domains. The tidal parameters of the harmonics K1 and M2 derived from tidal analysis are consistent (better than ± 0.05%) with the theoretical parameters for different models of the Earth's interior. The difference between the tested ocean tide models is negligible.
The superconducting gravimeter is currently the most accurate instrument in relative gravity measurement, so the high-precision calculation and analysis of superconducting magnetic levitation system ...is crucial to the development work of superconducting gravimeter. Shielding material can weaken the influence of external magnetic field source fluctuation on the internal levitation magnetic field, and provide a stable electromagnetic environment for the magnetic levitation system. But at the same time, shielding material will also have an impact on the internal suspended magnetic field itself, which will lead to large deviations in the study of electromagnetic characteristics of the magnetic levitation system. This paper establishes and optimizes the simulation calculation model of superconducting gravimeter magnetic levitation system based on H method, and studies the effect of magnetic shielding on the magnetic field, levitation force and magnetic force gradient of the internal levitation system. After that, the simulation calculation results are compared with the experimental results, and the simulation calculation error of superconducting levitation force and magnetic gradient is less than 1%, which verifies the correctness of the optimized simulation model. This study is an important guide for the accurate calculation of the electromagnetic properties of all superconducting systems containing magnetic shielding materials, such as superconducting gravimeter, superconducting gravity gradiometer, etc.
We report on the realization and evaluation of the 85Rb mobile atom absolute gravimeter named WAG-H5-1. With a distinctive Raman laser implementation, two new systematic errors, ac Stark shift ...imbalance and Raman laser chirp, are found and evaluated. The robustness of the instrument was tested during 1200 km-long transportation for the 10th International Comparison of Absolute Gravimeters at Beijing in October 2017. We acquire the degree of equivalence of 3 Gal after the comparison. Its performance was further assessed by comparing with an absolute gravimeter (FG5X) in Wuhan. With high mobility and environmental adaptability, the gravimeter reaches a sensitivity of 30 Gal (Hz)−1/2, stability of 1 Gal@ 4000 s and accuracy within 10 Gal.
