Integrity Systems' founder, Dr. Neal Carlson, contributed to the Space Shuttle avionics system design early in his career, while employed with Intermetrics, Inc. under subcontract to Rockwell International. Dr. Carlson developed the top-level design of the Shuttle's triple-redundant navigation system with 3 inertial navigation solutions. Each solution was corrected by Kalman filters processing mid-value-selected measurements from (in most cases) triple-redundant navigation sensors. The Kalman filters implemented 3 state vectors but only 1 covariance matrix, since the statistics for each solution were identical. Dr. Carlson also helped design fault detection and identification (FDI) algorithms for the redundant navigation sensors. He initiated and led the development of the Shuttle Redundancy Management Simulator (RMSIM). RMSIM was used and enhanced for several years thereafter, to perform simulation tests of the Shuttle fault-tolerant avionics and redundancy management systems.