GNSS-free relative-distance measurement among multiple satellites using software-defined radio interferometry

抄録

An artificial satellite formation flight, which is a group of small satellites working together as a system, is increasingly being used because launching multiple small satellites is more cost effective than launching one large satellite. Hence, relative positioning among multiple satellites is expected to become more important. The range of using a formation flight is predicted to extend to farther areas such as lunar orbit and areocentric orbit. Global Navigation Satellite System (GNSS) signals are often used for positioning and time synchronization, but the signal intensity and position accuracy decrease in these farther areas. GNSS-free relative-distance measurement among multiple satellites is therefore needed. We propose a high accurate method (cm order) for measuring the relative distance between satellites using a radio interferometry system (GHz order) consisting of software defined radio (SDR) containing one receiver and one transmitter. The proposed method uses two frequencies to resolve the phase ambiguity in radio interferometry and uses SDR as a transponder without the need for time synchronization. Therefore, measurement accuracy reaches 0.59% at about a 6-m distance.