Compact Position- and Azimuth-Determining System (CPADS)

The Improved Position and Azimuth Determining System (IPADS) takes up 6400 cubic inches, weighs 135 pounds with a Global Positioning System (GPS) receiver, and requires 200 watts of power. Clearly, there is a need to reduce its size, weight, and power (SWAP) footprint. The embedded inertial measurement unit (IMU) is the most SWAP- and performance-critical component of the system, which also includes optics, a display, and a battery. The existing IMU technology makes use of high-performance ring-laser gyroscopes (RLGs) and accelerometers. Since the required azimuth accuracy is 0.4 mil probable error (PE), the gyroscopes need to be capable of demonstrating bias instability (flicker) of no worse than 0.003 deg/hr. Hence, a high-end navigation-grade IMU is required. Unfortunately, while micro-electro-mechanical systems (MEMS) have drastically improved SWAP requirements, existing MEMS-based IMU performance has not approached the required level of bias stability, especially without external aiding. Therefore, a system that includes intrinsic self-calibration capabilities, which can compensate for the deficiency of MEMS sensors, is necessary to meet the IPADS performance requirements. For this program, Toyon will develop a self-calibrating compact PADS-replacement that will be inertial-sensor agnostic and will allow for in-field IMU replacements as technology improves.