Modernization of time scale control unit for «Glonass-K» spacecrafts

Navigation spacecraft’s atomic clocks suffer from sudden small frequency jumps. These jumps lead to a decrease of user’s positioning accuracy and should be considered. Traditional method to detect these frequency jumps with the use of ground control segment does not ensure early user alert of increasing range error. A perspective way to improve global navigation satellite system’s signal integrity is the use of satellite on-board autonomous system for continuous control of board synchronization equipment time scale. This paper describes a novel diagram of frequency comparator – the main element of such system. The main difference of proposed solution is an application of time-to-digital converter for estimation of time error which allows to decrease mass, dimensions and power consumption. The paper deals with the particularities of direct frequency comparator implementation for on-board equipment of space vehicle and describes structure of implemented breadboard model.