Measurement and analysis of gyro noise

Noise was measured on two identical space-qualified gyroscopes of the floated rate-integrating type (Ferranti Type 125) in an analog rebalance-loop configuration of selectable loop bandwidth, running under space representative conditions in the frequency range 0.005 to 50 Hz. Results were processed into statistical parameters. Through a fast Fourier transform, auto and cross power spectra were determined together with auto and cross variance functions. Using transfer function polynomials, equivalent gyro open loop power spectra were computed from the closed loop results and compared with directly measured, open-loop spectra. The results allow a noise propagation analysis to be made when designing and analyzing satellite attitude-control systems with the Type 125 as a strapdown sensor. For systems using estimators and a combination of inertial and optical sensors, the results allow the derivation and application of a realistic noise model for this type of gyro.