Navy asks Northrop Grumman to provide legacy AN/WSN-7 ring laser gyro systems for shipboard navigation

May 29, 2018
WASHINGTON – U.S. Navy shipboard navigation and guidance specialists are continuing their efforts to produce the legacy AN/WSN-7 ring laser gyro navigation system for Navy surface vessels and submarines.
WASHINGTON – U.S. Navy shipboardnavigation and guidance specialists are continuing their efforts to produce the legacy AN/WSN-7 ring laser gyro navigation system for Navy surface vessels and submarines.

Officials of the Naval Sea Systems Command in Washington announced an $10.9 million order Friday to the Northrop Grumman Corp. Sperry Marine segment in Charlottesville, Va., to build more of the company's AN/WSN-7 navigation system.

Northrop Grumman exercise a one-year option for production and associated provisioned items of the Navy’s WSN-7 navigation system -- a self-contained, ring laser gyro inertial navigation system that senses ship movement; computes the ship's precise position, velocity, attitude, and heading; and forwards the data to other vital ship systems.

The WSN-7 has been in service with the Navy for decades, and was designed as a replacement for spinning-mass gyro navigation equipment aboard Navy warships. The system is as a more reliable strapdown ring laser gyro-based replacement for the old WSN-2 navigation system.

The AN/WSN-7 offers accuracy of one nautical mile deviation over 24 hours. Navy officials are extending the life of the WSN-7 as long as possible as they develop a WSN-7 replacement.

Related: Honeywell to replace ring laser gyros to keep Navy AN/WSN-7 shipboard navigation functioning

Sperry Marine is developing the Inertial Navigation Systems Replacement (INS-R) Inertial Sensor Module (ISM) as a replacement for the WSN-7, to enable surface vessels to navigate accurately without GPS satellite navigation. This new system will be called the AN/WSN-12.

Sperry Marine reported completion of the ISM's preliminary design review in May 2016. The ISM will be a critical component on the INS-R WSN-12 replacement for the WSN-7. Preliminary design review means a system is operationally effective, and clears the way for detail design. First deliveries of WSN-12 engineering development models are schedule for later this year.

The INS-R will provide mission critical ship positioning, velocity, and altitude data to shipboard sensors, combat systems, guns, and missile systems. It will use an open-systems architecture using a modular design, standards-based interfaces, and widely supported consensus-based standards.

The AN/WSN-7, meanwhile, uses 25-year-old technology based on the NATO MK49 inertial navigation system deployed in the late 1980s. The INS-R will provide improved real-time navigation for Navy surface warships, and enable future technology growth.

Related: Northrop Grumman to develop new Navy shipboard navigation system to replace ageing AN/WSN-7

The standard WSN-7 shipboard configuration consists of two independent cabinets for redundancy and survivability. It is not be susceptible to jamming or detection by enemy forces.

The ring laser gyro uses two counter-propagating laser beams operating on different frequencies with the difference dependent on rotation rate. Measurement of this difference provides the rotation angle or rotation rate about the device's sensitive axis.

Compared with older spinning-mass gyro navigation systems, ring laser gyros are much smaller, do not resist changes in direction, are frictionless, have low power consumption, and feature almost no moving parts to enhance reliability while still providing adequate accuracy.

On this order Sperry Marine will do the work in Charlottesville, Va., and should be finished by April 2019. For more information contact Northrop Grumman Sperry Marine online at, or Naval Sea Systems Command at

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About the Author

John Keller | Editor

John Keller is editor-in-chief of Military & Aerospace Electronics magazine, which provides extensive coverage and analysis of enabling electronic and optoelectronic technologies in military, space, and commercial aviation applications. A member of the Military & Aerospace Electronics staff since the magazine's founding in 1989, Mr. Keller took over as chief editor in 1995.

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