Gyroscope Operation Research Articles

Cryogenic gyroscopes for the relativity mission

The relativity mission, also known as gravity probe B (GP-B), uses high-precision electrostatically suspended cryogenic gyroscopes for measuring the relativistic precessions of the frame of reference in a 650 km polar orbit. A 2 K environment is used to ensure the thermal stability and to implement the readout technique based on the magnetic dipole moment generated by a rotating superconductor. Analysis and results from more than 100 000 h of gyroscope operation show that the residual Newtonian drift is less than 0.17 marcsec/yr for a supported gyroscope in 10 −9 m/s 2 , and less than 0.020 marcsec/yr for a gyroscope in a fully inertial orbit.

Gyroscopes and charge control for the Relativity Mission Gravity Probe B

The most demanding goal of the Gravity Probe B Relativity Mission (GP-B) is the measurement of the parametrized post-Newtonian parameter γ to one part in 10 5. This goal requires a total experimental accuracy of ≤ 0.044 marcsec/yr. Analysis of and results from 100,000 hours of gyroscope operation on the ground show that the residual Newtonian drift will be < 0.17 marcsec/yr for a supported gyroscope in 10 −9 m/s 2, and < 0.020 marcsec/yr for an unsupported gyroscope in a fully inertial orbit. The expected error due to gyroscope drift is thus consistent with the measurement goal. The main gyroscope disturbance caused by cosmic radiation is charging of the rotor. A force modulation technique allows measurement of the charge of the gyroscope rotor to about 5 pC, while bipolar charge control to 10 pC is achieved using electrons generated by UV photoemission.

Design and operation of a very large ring laser gyroscope

The design and initial operation of a vertical square He-Ne ring laser G0 with a perimeter of 14 m is discussed. This builds on earlier demonstrations of the feasibility of large ring lasers (perimeter approximately 4 m) for single-mode gyroscope operation and with lesser pulling than navigation gyroscopes. With servoing of the rf excitation to yield single-mode operation, G0 gave a quality factor 1 x 10(12) and a Sagnac line with a frequency of 287.8 +/- 1.0 Hz induced by Earth rotation Omega(E). This has confirmed some vital questions over the feasibility of very large gyroscopes for geodetic measurements at the level of 10(-9) Omega(E).

Bidirectional operation and gyroscopic properties of a homogeneously broadened ring laser using thin-film layered media.

A combination of dielectric reflectors and thin (thickness much less than the wavelength) gain layers can be tailored to provide a suitable amplifier medium for laser gyro operation. The potential advantage is an all-solid-state device, in which spontaneous-emission noise can be reduced and the coupling between counterpropagating waves minimized.

Sagnac-type optical gyros

The Sagnac effect is briefly presented, and passive and active interferometers are defined as «gyros»,i.e. devices for the measurement (and control) of rotations and angular speeds. A project for the assembling and testing of an active ring gyroscope is described: the project is aimed at obtaining a versatile set-up suitable for investigation of the effects of the geometry of the laser cavity and for optimization of the gyroscope operation.

An overview of fiber-optic gyroscopes

The principles of operation of fiber-optic gyroscopes are reviewed. Performance-limiting phenomena are discussed along with methods to reduce their effect on the rotation-rate signal. Current technology and performance of state-of-the-art systems are presented. Finally, a direction of future research and possible applications are indicated.