Analysis of electromagnetic properties of superconducting suspension system for gravity measurement
A type of superconducting suspension system for gravity measurement was introduced, and the principle and feasibility was discussed. System modeling and simulation analysis was carried out by ANSOFT, and optimization of structural position was finally completed. Analysis shows that, the system was exceptionally stable with a magnetic force gradient small enough to observe gravity changes. For systems with a superconducting sphere weighed of 15 g, the gravity measurement accuracy could reach 1 nano-Gal.
Study on room-temperature effect of a superconducting gravimeter prototype

Purpose
This study aims to reveal the room-temperature effect of a superconducting gravimeter prototype, which will guide its subsequent optimization to improve its gravimetric measurement accuracy.


Design/methodology/approach
Without leveling, the prototype output signal, tilt data and room temperature were measured under steady operating conditions. After analyzing the correlations of the three data sets, the residuals of the prototype’s output signal were compensated using the tilt data and the geodynamic effects (ocean tide loading, atmospheric loading and the gravitational effect of polar motion) were then corrected.


Findings
The remaining residuals after correction may be caused by small tilt variations that are due to the sensor chamber temperature and radiation shield temperature changes. These small tilt variations were submerged in the tilt signal noise. Although the peak-to-peak noise of the tiltmeter does not exceed 15 µrad, it can still produce gravimetric deviations above 60 µGal when the prototype is significantly tilted.


Originality/value
This study analyzes in detail the room-temperature effect of a superconducting gravimeter prototype, introduces the tilt effect of the relative gravimeters to compensate for the gravimetric deviations and emphasizes that the improvement of fine leveling and the accuracy of the tiltmeter are key requirements for the prototype to perform high-accuracy gravity measurement tasks.

The Normal Modes of a Rotating, Elliptical Earth—II Near-Resonance Multiplet Coupling
Summary 
 
Certain of the Earth's poloidal and toroidal elastic-gravitational normal mode multiplets may be strongly coupled to another multiplet by the Earth's rotation and ellipticity of figure. This paper uses Rayleigh's variational principle to specify the selection rules for strong mode coupling and to examine the nature and effects of this mode coupling. It is found that some of the normal modes of a slowly rotating, slightly elliptical Earth model may consist of about half poloidal type motion and half toroidal type motion. This strong coupling can severely hinder the problem of proper mode identification and measurement of the angular frequencies of oscillation of the Earth's normal modes.