Performance Evaluation And Analysis Of BDS/GPS/Galileo Satellite Clocks In The Long-Term Scales

The navigation atomic clock is the most important payload of the navigation satellite,and its performance level directly determines the quality of positioning,navigation and timing(PNT)service.For foreign atomic clock technology lock-in problem,Chinese BeiDou navigation System(BDS)carrying the satellite clocks are all domestic rubidium clocks(most)and domestic hydrogen clocks(small),their performance and stability level are relatively poor.At the same time,the BDS spaceborne atomic clocks on-orbit operation process,because of the space environment abnormal voltage instability,equipment and components ageing,the service quality is not stable in performance,it is difficult to keep the stable for a long time for calibration precision index,and any abnormal will directly affect the performance of satellite clock navigation system service level.So it is necessary to monitor and evaluate comprehensively the service performance level of BDS satellite atomic clocks for a long time scales,analyze the real performance levels of the current BDS satellite atomic clocks on-orbit,reveal the performance differences of the BDS satellite-borne atomic clocks between different constellation,design the performance monitoring and evaluation program of BDS satellite clocks.At present,there are few public researches on the long-term status monitoring and classification performance evaluation of BDS satellite-borne atomic clock.Around these problems,this paper collected GPS,Galileo and BDS navigation system from 2013 to 2017 five-year precision clock difference product data,evaluated the three systems space-borne satellite atomic clock index change rule for a long time,change has carried on the summary analysis the performance of atomic clocks,reveals the spaceborne clock performance differences of different navigation system and the main clock switching rule,the main achievements and innovations are as follows:(1)The system summarizes the GNSS satellite clock performance evaluation theory and method of extracting the performance evaluation of the six key indicators,summarizes the data of discontinuity,gross error and clock jump abnormal data preprocessing methods,such as,design the spaceborne atomic clocks give attention to two or morethings Lord for clock switching detection,correlation analysis and in-orbit performance evaluation technology implementation plan.(2)In terms of phase,frequency and frequency drift index,found the BDS satellite clock phase modulation is frequent,but relatively stable frequency sequence,three types of constellation,MEO satellite clock performance is the most stable,is superior to the IGSO satellites clock,GEO satellite clock is the worst.The continuity and completeness of the Galileo bell product is slightly better than that of BDS,but it is significantly worse than GPS,and there is a similar significant phase and frequency jump with BDS.In terms of frequency drift rate,Galileo is comparable to GPS index(E-14),no obvious system noise,which is better than BDS index level(E-13).The frequency drift sequences belong to part of BDS satellites have obvious long period characteristic fluctuation,which may be related to the characteristics of satellite clock hardware device.(3)In terms of frequency stability,it was found the BDS satellite clock stability in E-14 magnitude of ten-thousand seconds,the average index is fairly with GPS satellite clock performance,the result of the Galileo system shows better performance of on-orbit features.In the fact of frequency accuracy,BDS satellite clock frequency accuracy is about E-13 orders of magnitude,its index result is better than that of GPS Block IIR and Block IIR-M clock offsets,and is fairly with the result of GPS Block IIF clock offsets,but is significant worse than the results(E-14)of Galileo index.(4)Combined with frequency drift and the change law of composite index such as frequency,design the detecting method of on-orbit satellite clock switching operation,more fully presents the BDS/GPS/Galileo five-year master clock switching time.The detection results show that the GEO and IGSO satellites of BDS are relatively frequent,and the MEO satellite has not switching.In comparison,GPS Block IIF has been switched to 17 times,and the Galileo system FOC satellite clock is more than 15 times,which is greater than that of BDS satellite clock switching(8 times).(5)Analyzed the correlation between different performance indexes,it is concluded that there was a strong correlation between frequency drift,frequency,accuracy and frequency stability indexes.It is worth noting that there are long periodic signals in the frequency accuracy and frequency stability sequence of severl GPS and Galileo satellite clocks,which need to be taken seriously in the monitoring and evaluation of navigation system.