John P. Rahn

Progress in navigation-grade IFOG performance

We previously reported achievement of 0.0027 deg/rt-hr angle random walk, as well as attainment of 0.0092 deg/hr bias uncertainty, 9.2 ppm scale factor error and 0.38 arc-seconds input axis alignment error over the temperature range -55 to 71 degC under dynamic thermal environments. The gyro coil in these instruments has less than 3 inches outer diameter and less than one inch height. In this paper we report on further advances in navigation-grade IFOG technology achieved at Litton. The angle random walk has been reduced by a factor of three to 0.0009 deg/rt-hr. Bias uncertainty of 0.0081 deg/hr has been attained over the -55 to 71 degC temperature range having more stringent temperature ramps than previously reported. The gyro bias magnetic sensitivity has been reduced to 0.0002 deg/hr/gauss. This paper describes the IFOG optical architecture that utilizes a low-birefringence network and a polarization maintaining network, discusses the dominant sources of thermal and magnetically-induced bias error in the IFOG and presents the latest data from the navigation- grade IFOG.