Pseudolite-based multiple space-vehicles relative navigation for formation flying

Precise relative navigation is a necessary and important technology for any operation of multiple space vehicles on-orbit formation flying together. Carrier-phase Differential GPS (CDGPS) positioning has been proven to be an accurate technique for relative positioning and attitude determining between multiple vehicles. But, the present satellite navigation system has no enough covering performance for some flying missions. For example, in high orbits, navigation satellite reception is often not sufficient to resolve position and attitude between all vehicles in the formation flying. One of the methods of taking advantage of satellite navigation system in such cases is to augment the available signals with additional signals from pseudolites. In fact, pseudolite is just a special transmitter, whose signals have many of the characteristics of the signals broadcast by the satellites of navigation system. Meanwhile, pseudolite can be placed on the ground, or in the MEO or GEO orbits. In this paper, an onboard pseudolite augmentation system of each vehicle for formation flying is studied, such as each vehicle can exchange navigation data with other vehicles. Such augmentation system can be used to improve the performance of satellite navigation system, e.g. GPS, GLONASS, and so on. Based on the correlative studies, some conclusion for the space application of pseudolite is given, including some idea about the arrangement of correlative ground experiments.