The hemispherical resonator gyro (HRG) is a gyroscope technology, patented and commercialised by Northrop Grumman Corporation.
The HRG is used for military and commercial space applications. It 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.
