Buchman S, Turneaure J P
W.W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, California 94305-4085, USA.
Rev Sci Instrum. 2011 Jul;82(7):074502. doi: 10.1063/1.3608615.
Gravity probe B (GP-B) was designed to measure the geodetic and frame dragging precessions of gyroscopes in the near field of the Earth using a drag-free satellite in a 642 km polar orbit. Four electrostatically suspended cryogenic gyroscopes were designed to measure the precession of the local inertial frame of reference with a disturbance drift of about 0.1 marc sec/yr-0.2 marc sec/yr. A number of unexpected gyro disturbance effects were observed during the mission: spin-speed and polhode damping, misalignment and roll-polhode resonance torques, forces acting on the gyroscopes, and anomalies in the measurement of the gyro potentials. We show that all these effects except possibly polhode damping can be accounted for by electrostatic patch potentials on both the gyro rotors and the gyro housing suspension and ground-plane electrodes. We express the rotor and housing patch potentials as expansions in spherical harmonics Y(l,m)(θ,φ). Our analysis demonstrates that these disturbance effects are approximated by a power spectrum for the coefficients of the spherical harmonics of the form V(0)(2)/l(r) with V(0) ≈ 100 mV and r ≈ 1.7.
引力探测器B（GP - B）旨在利用一颗位于642公里极地轨道的无拖曳卫星，测量地球近场中陀螺仪的测地岁差和参考系拖曳岁差。四个静电悬浮低温陀螺仪被设计用于测量局部惯性参考系的岁差，其干扰漂移约为0.1毫角秒/年至0.2毫角秒/年。在任务期间观察到了许多意外的陀螺仪干扰效应：自旋速度和极迹阻尼、未对准和滚动极迹共振扭矩、作用在陀螺仪上的力以及陀螺仪电势测量中的异常。我们表明，除了可能的极迹阻尼外，所有这些效应都可以由陀螺仪转子、陀螺仪外壳悬架和接地平面电极上的静电贴片电势来解释。我们将转子和外壳贴片电势表示为球谐函数Y(l,m)(θ,φ)的展开式。我们的分析表明，这些干扰效应可以用球谐系数的功率谱V(0)(2)/l(r)来近似，其中V(0)≈100毫伏，r≈1.7。
