Britannica Sources used in this answer

How do ring laser gyroscopes help guide jetliners and satellites?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

gyrocompass The gyrocompass aboard the National Oceanic and Atmospheric Administration's (NOAA) ship *Rainier*. Gyrocompasses are navigational instruments that use a continuously driven gyroscope to accurately seek the direction of true (geographic) north.

Ring laser gyroscopes are optical devices used in inertial guidance systems to help navigate jetliners, booster rockets, and satellites. Unlike mechanical gyroscopes, they have virtually no moving parts and operate based on the Sagnac effect.12

In these systems, laser beams are split and directed in opposite directions through three mutually perpendicular hollow rings (often shaped as triangles, squares, or rectangles) filled with inert gases. When the vehicle turns or pitches, the beam traveling in the direction of rotation takes slightly longer to return to its origin than the beam traveling against the rotation. This creates an interference pattern that is measured by photoelectric cells.1

The patterns from all three rings are numerically integrated to determine the craft's turning rate in three dimensions. By combining these instantaneous turning rates with data from accelerometers, an onboard computer can continuously calculate the vehicle's velocity and position to maintain its intended trajectory.12