Precision spheres for the Gravity Probe B experiment

Marcelja, F.; DeBra, D.; Turneaure, J. P.

doi:10.1088/0264-9381/32/22/224007

Cited by 7 publications

(5 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Davidson Optronics and Speedring rough ground the fused silica blanks into spheres. These were lapped and polished at Stanford, yielding <20 nm peak deviation of the rotor surface from the best fit sphere [10,11]. Rotor asphericity was measured using a Talyrond Model 73 roundness measuring instrument [12], manufactured by the Rank Taylor Hobson Company, shown in figure 3.…”

Section: Gyroscope Overviewmentioning

confidence: 99%

The Gravity Probe B gyroscope

Buchman¹,

Lipa²,

Muhlfelder³

et al. 2015

Class. Quantum Grav.

Self Cite

View full text Add to dashboard Cite

The Gravity Probe B (GP-B) gyroscope, a unique cryogenically operated mechanical sensor, was used on-orbit to independently test two predictions of general relativity (GR). Here, we describe the development and performance of the GP-B gyroscope, its geometry and fabrication, spin-up and vacuum approach, magnetic considerations, and static charge management. The history of electrically suspended gyroscopes puts the current work in context. Fabrication and ground testing of the GP-B gyroscope are detailed, followed by a review of on-orbit initialization, calibration, operation, and performance. We find that the performance was degraded relative to the mission goals, but was still sufficient to provide excellent new tests of GR. The degradation is partially due to the existence of gyroscope torques due to an unanticipated interaction between patch potentials on the rotor and the housing. We discuss these patch potentials and describe the effect of related torques on gyro drift. It was essential to include models for the effects due to the patch potentials in the complete data analysis model to yield determinations of the two GR effects.

show abstract

Section: Gyroscope Overviewmentioning

confidence: 99%

The Gravity Probe B gyroscope

Buchman¹,

Lipa²,

Muhlfelder³

et al. 2015

Class. Quantum Grav.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This improvement resulted from conservative assumptions made prior to launch combined with a post-launch rotor mass unbalance that was lower than the pre-flight estimate. The actual rotor mass unbalances ranged from 10.1 to 4.8 nm or 65% to 300% smaller than pre-launch worstcase estimates [19,20]. Centrifugal bulge was approximately a factor of four smaller than expected due to reduced rotor spin speed.…”

Section: Treatment Of Systematic Errorsmentioning

confidence: 81%

Gravity Probe B data analysis: III. Estimation tools and analysis results

Conklin¹,

Heifetz²,

Holmes³

et al. 2015

Class. Quantum Grav.

Self Cite

View full text Add to dashboard Cite

This paper provides detailed descriptions of the numerical estimation algorithms used to fit physics-based models to the data from the Gravity Probe B spacecraft, as well as the scientific results of the experiment, and the statistical and systematic uncertainties. The first paper in this series of three data analysis papers derives the mathematical expressions for the signals to be analyzed, and the second paper deals with science data acquisition and their preparation for the relativistic drift rate estimation. The data from each of the four gyroscopes are partitioned into six segments, each spanning several weeks to several months. These segments are first analyzed individually to check the validity of the mathematical models and the accuracy of the estimation routine by examining the consistency of the relativistic drift rate estimates from each of these 24 gyro-segments. Then, the drift rate estimates and uncertainties are calculated for each individual gyroscope and for the four gyroscopes combined. These results are presented and compared with each other and with the prediction of general relativity.

show abstract

“…The machine was designed and manufactured at PTB. A similar machine design in a simpler technical performance is known from the NASA Gravity Probe B experiment [4,109]. The lapping processes employed different sizes of alumina grain (Al2O3) in aqueous solution.…”

Section: Avogadro Experimentsmentioning

confidence: 99%

Contributions of precision engineering to the revision of the SI

et al. 2017

View full text Add to dashboard Cite

All measurements performed in science and industry are based on the International System of Units, the SI. It has been proposed to revise the SI following an approach which was implemented for the redefinition of the unit of length, the metre, namely to define the SI units by fixing the numerical values of so-called defining constants, including c, h, e, k and NA. We will discuss the reasoning behind the revision, which will likely be put into force in 2018. Precision engineering was crucial to achieve the required small measurement uncertainties and agreement of measurement results for the defining constants

show abstract

Precision spheres for the Gravity Probe B experiment

Cited by 7 publications

References 23 publications

The Gravity Probe B gyroscope

The Gravity Probe B gyroscope

Gravity Probe B data analysis: III. Estimation tools and analysis results

Contributions of precision engineering to the revision of the SI

Contact Info

Product

Resources

About