a device providing an inertially stabilized laser beam as an optical reference . the device consists of a base and a small stabilized optical platform that emits the laser beam . the platform connects to the base through a mechanical flexure that allows relative motion in two axes . high - bandwidth angular rate sensors affixed to the platform measure platform motion in inertial space . linear displacement sensors measure relative motion between base and platform . a closed - loop control system accepts these sensor measurements and command actuators that null the sensed platform motions , maintaining the optical platform fixed in inertial space . the digital controller implements a sensor blending kalman filter that blends high frequency signals from the platform with low frequency signals from a dc sensor external to this device but affixed to the common base . the controller enables both stabilization of the laser beam and commanded pointing of the beam in inertial space .