Use of single star sightings in boost navigation

Abstract

Information obtained from a single inflight star sighting is used to calibrate a boost vehicle's IMU errors. Several error-inducing parameters, including initial alignment, accelerometers, and gyros are included in the estimation state vector. Although the problem studied is shown to be generally unobservable, suitable preflight alignment techniques can be used to induce observability. The resultant induced observability arises from correlations between initial alignment errors and platform gyros or accelerometer s used for initially aligning the platform. When the platform's initial misalignment is directly observable, the presence of correlations between the initial misalignment and formerly unobservable error sources permits estimation of the latter. Additional results and a sample problem demonstrate the effect of variations in initial conditions, dynamic effects, and observation noise as a function of relevant design parameters.