Northrop Grumman's patented hemispherical resonator gyro (HRG) technology, which is used for military and commercial space applications, recently achieved a major milestone of 25 million hours of continuous operation without a single mission failure.

Since February 1996, the HRG has been a vital component of Northrop Grumman's Scalable Space Inertial Reference Unit (Scalable SIRU) and its predecessor, the Space Inertial Reference Unit (SIRU), which enable the stabilization, tracking and attitude control of spacecraft and satellites.

The Scalable SIRU was instrumental in achieving the scientific objectives of several highly successful program missions, including MESSENGER, Deep Impact and Cassini.

"Our HRG's impressive track record in space is unmatched," said Stephen J. Toner, vice president of Northrop Grumman's Military and Civil Space business unit. "Customers choose our high-endurance gyro for critical space missions that require superior performance and dependability because it is the pinnacle of space navigation."

The HRG's simple construction from three pieces of machined quartz, including a thin-walled quartz shell sensing element, makes it highly reliable and naturally radiation-hardened in any space environment. Additionally, the gyro's small size and light weight lends itself to an inertial reference unit form factor that is easily incorporated into a spacecraft's design.

Launched aboard more than 125 spacecraft, the HRG technology has been used in commercial, government and civil space missions for domestic and international customers. It was first used on the Near Earth Asteroid Rendezvous mission, which was the first of NASA's Discovery missions and the first mission to place a spacecraft into orbit around an asteroid.

The HRG technology is based on scientific observations made more than 100 years ago of a "ringing" wineglass that produces changing sounds depending upon its rate of rotation.