Polhode Motion, Trapped Flux, and the GP-B Science Data Analysis

Silbergleit, A. S.; Conklin, John; DeBra, D.; Dolphin, M.; Kozaczuk, Jonathan; Santiago, David I.; Salomon, Mark; Worden, P.

doi:10.1007/s11214-009-9548-z

Cited by 19 publications

(27 citation statements)

References 11 publications

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“…The changing polhode period is attributed to damping of the polhode motion. 22 This damping leads to the spin vector being asymptotically aligned with the maximum principal moment of inertia, I 3 . When the polhode angle is sufficiently small, γ p < π/4 rad, the polhode period is well characterized by an asymptotic part T pa and an exponentially decreasing part FIG.…”

Section: Experimental Observationsmentioning

confidence: 99%

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The effects of patch-potentials on the gravity probe B gyroscopes

Buchman

Turneaure

2011

Review of Scientific Instruments

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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.

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Section: Experimental Observationsmentioning

confidence: 99%

“…We can produce three equations from Eqs. (22) and (23) that only involve sums and differences of V A+/B+/C+ and V A−/B−/C− . These three equations give a statistical average suspension electrode voltage that is at least one-half the average rotor voltage.…”

Section: Patch-potential Modelmentioning

confidence: 99%

The effects of patch-potentials on the gravity probe B gyroscopes

Buchman

Turneaure

2011

Review of Scientific Instruments

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“…Moreover, a very complex HF SQUID signal analysis (TFM) had to be developed and carried out, as explained in [2,9], here in section 5.4, and in [3], section 2. Nevertheless, the knowledge and skills gained during preflight preparations for data treatment were very valuable for this post-flight work.…”

Section: Discussionmentioning

confidence: 99%

“…The blockdiagrams of this and some other signal preprocessing, including FFT harmonics of HF SQUID signal, are in figures 4 and 5. The HF SQUID signal needed for trapped flux mapping (TFM) ( [2,9]), crucial for the GP-B data analysis, was processed in a special way described in section 5.4.…”

Section: Set Of Science Signalsmentioning

confidence: 99%

Gravity Probe B data analysis: II. Science data and their handling prior to the final analysis

Silbergleit

Conklin

Heifetz

et al. 2015

Class. Quantum Grav.

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The results of the Gravity Probe B relativity science mission published in Everitt et al (2011 Phys. Rev. Lett. 106 221101) required a rather sophisticated analysis of experimental data due to several unexpected complications discovered on-orbit. We give a detailed description of the Gravity Probe B data reduction. In the first paper (Silbergleit et al Class. Quantum Grav. 22 224018) we derived the measurement models, i.e., mathematical expressions for all the signals to analyze. In the third paper (Conklin et al Class. Quantum Grav. 22 224020) we explain the estimation algorithms and their program implementation, and discuss the experiment results obtained through data reduction. This paper deals with the science data preparation for the main analysis yielding the relativistic drift estimates.

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“…This information was necessary to determine the distribution of trapped flux on the surface of the rotor and the time varying readout scale factor [7].…”

Section: Background and Available Signalmentioning

confidence: 99%

Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal

Salomon

Conklin

Kozaczuk

et al. 2011

Review of Scientific Instruments

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In this paper, we present a method to measure the frequency and the frequency change rate of a digital signal. This method consists of three consecutive algorithms: frequency interpolation, phase differencing, and a third algorithm specifically designed and tested by the authors. The succession of these three algorithms allowed a 5 parts in 10 10 resolution in frequency determination. The algorithm developed by the authors can be applied to a sampled scalar signal such that a model linking the harmonics of its main frequency to the underlying physical phenomenon is available.This method was developed in the framework of the Gravity Probe B (GP-B) mission. It was applied to the High Frequency (HF) component of GP-B's Superconducting QUantum Interference Device (SQUID) signal, whose main frequency f z is close to the spin frequency of the gyroscopes used in the experiment. A 30 nHz resolution in signal frequency and a 0.1 pHz/sec resolution in its decay rate were achieved out of a succession of 1.86 second-long stretches of signal sampled at 2200 Hz. This paper describes the underlying theory of the frequency measurement method as well as its application to GP-B 's HF science signal.

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Polhode Motion, Trapped Flux, and the GP-B Science Data Analysis

Cited by 19 publications

References 11 publications

The effects of patch-potentials on the gravity probe B gyroscopes

The effects of patch-potentials on the gravity probe B gyroscopes

Gravity Probe B data analysis: II. Science data and their handling prior to the final analysis

Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal

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