Spacecraft Navigation Using X-Ray Pulsars

The feasibility of determining spacecraft time and position using x-ray pulsars is explored. Pulsars are rapidly rotating neutron stars that generate pulsed electromagnetic radiation. A detailed analysis of eight x-ray pulsars is presented to quantify expected spacecraft position accuracy based on described pulsar properties, detector parameters, and pulsar observation times. In addition, a time transformation equation is developed to provide comparisons of measured and predicted pulse time of arrival for accurate time and position determination. This model is used in a new pulsar navigation approach that provides corrections to estimated spacecraft position. This approach is evaluated using recorded flight data obtained from the unconventional stellar aspect x-ray timing experiment. Results from these data provide first demonstration of position determination using the Crab pulsar.