Overview STAR-1 synthetic aperture radar navigation and motion compensation upgrade

This paper presents an overview of the system design and implementation for the navigation and motion compensation (or mocomp) upgrade for the Intermap Sea Ice and Terrain Imaging Airborne Radar (STAR-1) 6 meter SAR system. The impetus for this upgrade is discussed along with the selection criteria for the inertial reference unit (IRU), the critical element for the navigation and mocomp system. Since most inertial systems incorporate lowpass filtering at a cutoff well below the expected aircraft motion bandwidth, an internal solution was required that was based on the raw acceleration and gyro data from the inertial system. The implementation of the internal solution is outlined along with the successful development of an air-borne transfer alignment from the Laseref III navigation solution to the internal solution used for mocomp. An overview of the STAR-1 mocomp implementation is then presented outlining the expected motion characteristics and the constraints imposed by the requirement for a real-time solution. As with any real-time system, the response time of the system is critical. The design of the hardware and software used to implement the navigation and mocomp is presented with a discussion of the advantages of a true multiprocessor environment with a preemptive real time operating system.