Integrity Systems (ISI) led the Air Force's Distributed Kalman Filter Architectures (DKFA) program from its inception in 1987 to its Phase II completion in early 1994, and its later-phase completion in 1997. The DKFA program began as a Phase I SBIR (Small Business Innovation Research) contract, moved to a Phase II SBIR contract, and then received additional Air Force funding to demonstrate the new technology in a real-time avionics system testbed.

Under the Phase I and II contracts, ISI developed distributed Kalman filter (DKF) methods for multi-sensor navigation systems, particularly those with cascaded filter structures and/or parallel processing architectures. These new methods were implemented and simulation-tested in a realistic, tactical mission environment. Their demonstrated advantages include increased data throughput on parallel processors; optimal or near-optimal accuracy of the cascaded filter structures; and significant improvements in sensor fault detection and isolation capability. To conduct these studies, ISI developed the DKF Simulator, including medium/high fidelity truth models for the strapdown INS, baro altimeter, GPS satellites and receiver, synthetic aperture radar (SAR), and terrain-aided navigator (TAN). For each of these sensors, ISI designed and implemented the associated Kalman filter models. ISI also implemented general-purpose FORTRAN versions of the distributed Kalman filter, with a variety of user-selectable configurations. Simulation studies included comparative performance of the several DKF candidate configurations.

Subsequently, ISI developed the DKF-Ada Real-Time Testbed to support performance evaluation of the new DKF techniques in a simulated flight hardware/software environment. This Real-Time Testbed operated on two VAX processors connected by a MIL-STD 1553B databus, and demonstrated successful operation of the DKF method in a real-time Ada multitasking implementation. The Testbed also served as a prototype for the functionally equivalent DKF-Models (FORTRAN) and DKF-Filter (Ada) software running in the Air Force's Integrated Test Bed, a real-time avionics hardware/software simulation facility.