Application of Zero-Lock Laser Gyro Technology to High Accuracy Stellar-Inertial Systems

Noboru Kondo

Abstract:	The four-mode multioscillator ring laser gyro, designated as the Zero-lock Laser GyroTM (ZLG) by Litton, enables new and innovative approaches to mechanizing high accuracy stellar-inertial navigation systems. Absent any requirement for dithering or rate biasing to circumvent the lock-in phe- nomenon inherent in conventional two-mode ring laser gy- ros (RLG), the ZLG offers many advantages for stellar- inertial systems. The ZLG does not impose any disturbing dynamic motion on the stellar sensor, facilitating high accu- racy star tracking. In addition, the extremely precise scale factor of the ZLG allows comounting of the stellar sensor with the inertial sensors on a common instrument cluster and sequentially pointing the whole stellar-inertial sensor clus- ter at multiple target stars to measure the inertial system errors. This eliminates the need for the highly accurate angle encoders used in currently operational stellar-inertial sys- tems to transform stellar observations to their inertial refer- ence axes. Factory production of medium-accuracy ZLG inertial navi- gation systems (INS) was initiated in early 1991 for several military andcommercial contractual programs. Since stellar updates can correct for gyro drift errors, the same medium- accuracy ZLG is being utilized in Litton developmental pro- grams for high accuracy stellar-inertial systems. This paper describes the significant differences between four- and two-mode RLGs, the tradeoffs in mechanizing RLG/ZLG-based stellar-inertial systems, the specific applications of ZLG technology to stellar-inertial programs, and the resultant benefits.
Published in:	Proceedings of the 1992 National Technical Meeting of The Institute of Navigation January 27 - 29, 1992 Catamaran Resort Hotel San Diego, CA
Pages:	253 - 262
Cite this article:	Kondo, Noboru, "Application of Zero-Lock Laser Gyro Technology to High Accuracy Stellar-Inertial Systems," Proceedings of the 1992 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1992, pp. 253-262.
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