High accuracy performance capabilities of the military standard ring laser gyro inertial navigation unit

The medium accuracy standard ring laser gyro (RLG) inertial navigation unit (INU) exemplified by Litton´s LN-93 system has benefited from continual improvements during the production process such that the present navigational accuracy and reliability are better by a factor of two or more over the original requirements as defined by SNU 84-1. Performance enhancements are now available which further improve navigation performance to the high-accuracy category while maintaining the reliability of the production system. Two enhancement mechanizations are described-one that requires software-only changes to improve inertial performance, and one that employs a self-contained (embedded) GPS to augment the inertial performance. These enhancements may be applied in combination to provide uniquely effective immunity to GPS spoofing countermeasures. These enhancements retain the present standard RLG INU form factor, mounting, and electrical interface, and are therefore particularly advantageous for retrofit application. Potential retrofit applications with various aircraft avionics architectures are discussed