Accuracy improvements for a GPS attitude determining system developed for the Strategic Defense Initiative Organization

Summary form only given. The Strategic Defense Initiative Organization (SDIO) has sponsored Adroit Systems´ development and testing of an attitude determining system (ADS) based on GPS (Global Positioning System) satellite signal interferometry. The relative phase difference of the GPS carrier is measured between a pair of antennas spaced 1 m apart to determine the antenna baseline pointing vector. The system requires only three satellites to operate once the position of the antenna is ascertained. Double differencing is used to eliminate RF bias and drift between antennas. The second generation of this ADS was delivered in 1990 to the USA Army Engineer Topographic Laboratory for evaluation. This Adroit ADS can calculate and update pointing information each second. Accuracy was demonstrated in Army tests to approximately 10 milliradians in one second, and below 1 milliradian with a 300 second sample time