Testing of Stellar-Inertial Guidance Systems

The ever growing demands for improvement in performance of guidance equipment to be used in missiles and space vehicles has led to intensive interest in stellar-aided inertial reference systems. A stellar-inertial system uses star position information to correct for gyro drift and misalignment errors and serves as a means for updating position and velocity information generated by the guidance system computer. This capability becomes particularly attractive for extended space flights and for mobile ballistic missile systems. The design configurations assumed by stellar-inertial guidance systems may vary widely. Variations arise from the types of guidance equations dictated by the applications and also as a consequence of the instruments used as stellar sensors. The guidance problem may be solved by a variety of computational schemes, using explicit equations or schemes such as Q matrices. The star sensing devices are usually categorized by their detector mechanisms. The three main types used in systems now operational or under development are photomultipliers, vidicon tubes, and solid-state elements. The scanning methods used with these devices range from mechanical drives to electronic schemes using no moving parts. Each of these methods has merits and disadvantages which influence the guidance system designer in his selection. The intended application is the criterion in the type of computational scheme and components that are selected. This paper presents a survey of the above-mentioned aspects of stellar-inertial guidance equipment with a view toward establishing the validity and applicability of conventional inertial guidance test methods to the testing of stellar-inertial equipment.