Advanced Line-of-Site Stabilization (LOSS) and Beam Control
Optical imaging systems and laser pointing systems provide a magnified image for viewing and for projecting a precision laser for illuminating a distant target. The optical system is susceptible to vibrational forces which impose jitter on any optical signal being processed by the system. This random motion of the optical system produces a blurring of an image being magnified by the system. In the case of a laser pointing system, the motion imparted to the laser disturbs it pointing direction.
In order to keep the Line-of-Site (LOS) stable, an inertial reference must be provided which identifies any apparent motion in the LOS. In space applications, a star is commonly used as an optical inertial reference because there is no apparent motion relative to the earth. For precision optical imaging and laser pointing system applications where stars are not readily available within the Field of View (FOV), an Optical Inertial Reference Unit (OIRU) stabilized by its own inertial sensors can provide an optical inertial reference that is within the FOV of the optical imaging and pointing system at all times.
Jitter imposed on the optical system displaces the OIRU reference laser signal which is detected by the LOS jitter sensor. The LOS jitter sensor signal is then used to generate a correction signal to position the jitter correction Fast Steering Mirror (FSM) in a direction to cancel the LOS jitter. The typical optical system architecture with advanced LOS stabilization is shown in the figure below.
In summary, ATA Optical IRU (OIRU) creates an Optical Reference Beam (ORB or “Virtual Star”) within the Optical System FOV for optical imaging and pointing system stabilization. ATA Fast Steering Mirrors (FSM) are used to reject LOS jitter measured by the LOS jitter sensor by positioning the FSM in a direction to cancel the LOS jitter.