Research on the Inversion Method of USO Frequency Stability Joining GNSS and Inter-satellite Distance Measurement

Abstract

K-band ranging (KBR) system and GNSS receiver are the key payloads of the gravity exploration satellite which employs LEO satellite tracking LEO satellite technology. Ultra-stable crystal oscillator, providing precise inter-satellite distance measurement with clock frequency reference, is the key component of the KBR-GNSS system. Therefore, real-time and dynamic monitoring on-orbit ultra-stable oscillator (USO)’s frequency stability are very necessary. First of all, the analysis formula of DOWR with time-tag corrected is deduced based on the study of the KBR-GNSS measuring principle. Second, the coupling relationship between Allan variance formula and inter-satellite time difference is analyzed deeply. Two methods of inversing USO Allan variance are proposed, of which one is using inter-satellite time difference measurement and the other one is employing inter-satellite distance measurement. Finally, referring to GRACE satellite payload scheme, a set of KBR-GNSS system is developed, by using which, the effectiveness of the two algorithms is validated and their advantages and disadvantages are compared meanwhile. The research results of this paper have some references to the design of inter-satellite ranging system of Chinese first generation earth gravity exploration satellite.