Research On The Method Of Tracking And Orbit Determination Of GEO Satellite Based On Interferometry

The orbit determination of Geostationary Earth Orbit(GEO)satellites is a difficult problem in the field of precise orbit determination,and due to the need for frequent maneuvers to maintain their orbital position,high-precision and efficient orbit recovery after satellite maneuvers is particularly important.Very Long Baseline Interferometry(VLBI)technology has ultra-high spatial resolution.Compared to traditional ranging technology for high-precision measurement in the radial direction of satellite orbit,its advantage lies in the high-precision measurement in the transverse direction.VLBI can calibrate its own system error by observing radio sources whose position are accurately known,but it is not suitable for observation systems with interferometric measurement capabilities that lack radio source observation conditions.The main research of this thesis is to study different calibration methods for system errors of interferometric measurement,combine VLBI with Orbit Determination by Transfer Tracking(ODTT)to improve the orbit determination precision of GEO satellites,and achieve highprecision and efficient orbit recovery after maneuvers.Based on the VLBI system and small antenna passive orbit measurement system of the National Time Service Center(NTSC),Chinese Academy of Sciences,the achievements and innovations of this thesis are as follows:(1)For observation system such as passive orbit measurement with small antennas that do not have the conditions for observing radio sources,in order to solve the calibration problem of system error,a method of using satellites that can obtain precise ephemeris instead of radio sources is proposed on the study of differential observation between radio sources and satellites,and verified and implemented on VLBI system.Design a schedule suitable for alternating observation.Precise orbit determination of GEO satellites has been carried out based on data from the mode of observing radio sources and satellite alternately,as well as that of observing different satellites.The method of using radio source for system error calibration is that: Select radio sources with high flow density in C band,and its angular distance is kept within 10 degrees from the satellite.Therefor,system error can be corrected by extrapolating the delay of baseline from the known precise position of radio sources.The observation data of the GEO satellite China Sat 12 after calibrating the system error by radio sources is used for precise orbit determination.The result shows that: 1.The internal coincidence precision of overlapping arc at three-dimensional position is better than 5 meters;2.The transverse constraint ability of VLBI on satellite orbit is significantly stronger than that of radial constraint;Using the precise orbit provided by ODTT for inspection,an external coincidence precision better than 40 m can be obtained.The method of using satellite instead of radio sources for system error calibration is that: Observe Beidou C02 and Beidou C05 satellite alternately and take Beidou C02 as a reference.The precise orbit of Beidou C02 provided by the international GNSS Monitoring and Assessment System(i GMAS)is used to deduce the delay of baseline.The delay can also be inferred from the orbit determined by VLBI data.The difference between the two delay is considered as system error so that Beidou C05 satellite’s system error can be calculated by polynomial fitting.The observation data of Beidou C05 after calibrating the system error is used for precise orbit determination which is inspected by the precise orbit provided by i GMAS.The precision at three-dimensional position is 61.852 m,which is 25.18% higher than 82.664 m before calibrating the system error.It can been that taking satellite with precise ephemeris as calibration references can effectively reduce the impact of system errors and improve the precision of orbit determination,which is of great significance for some interferometric measurement systems that do not have conditions for observing radio sources.(2)Propose to analyze the contribution of different VLBI baselines to joint ODTT for precise orbit determination from the perspective of improving the Position Dilution of Precision(PDOP),and achieve the improvement of precision for GEO satellite orbit determination.The shortcoming of ODTT in transverse measurement for satellite can be supplemented by joint VLBI so that the precision of orbit determination can be improved.And adding VLBI baselines can improve the PDOP value of ODTT system and the target satellite.Different VLBI baselines have different degrees of improvement on this PDOP value.This thesis first verifies its positive correlation with the improvement of orbit determination precision.Precise orbit determination of China Sat12 was carried out by joint data from ODTT and different baselines including KashiSanya joint ODTT,Jilin-Kashi joint ODTT,Jilin-Sanya joint ODTT and two baselines joint ODTT which are Jilin-Kashi and Jilin-Sanya.When adding a baseline of KashiSanya,PDOP is improved by 3.00 and orbit determination precision is improved by11.48%;When adding a baseline of Jilin-Kashi,PDOP is improved by 3.38 and orbit determination precision is improved by 14.73%;When adding a baseline of Jilin-Sanya,PDOP is improved by 6.90 and orbit determination precision is improved by 19.75%;When adding two baselines,Jilin-Sanya and Jilin-Kashi,PDOP is improved by 9.94 and orbit determination precision is improved by 27.23%.It can be seen that when the measurement precision of delay is at the same level,the more PDOP decreases,the greater the improvement in orbit determination precision.This conclusion can provide reference for the optimal selection of baseline under specific conditions of joint observation.(3)Develop a method of orbit determination with short arc joint VLBI and ODTT and achieve high-precision and high-efficiency orbit recovery after GEO satellites maneuver.Orbit determination with short arc is suitable for studying the orbit recovery of GEO satellites after maneuvering.Joint data including VLBI and ODTT can combine the measurement advantages of both technologies in the transverse and radial directions of orbit to meet the high-precision and high-efficiency orbit recovery requirements after maneuvering.Firstly,joint observation data of 1 hour,1.5 hours,and 2 hours were used for orbit determination.The result shows that: As the arc length of orbit determination increases,the precision of orbit determination can be improved;Under the same arc length,the precision of orbit determination by VLBI and ODDT is better than ODTT only.Then the arc length of ODTT is added and compare its precision with 1 hour-joint orbit determination.When the arc length of orbit determination only by ODTT increases to 3 hours,its orbit determination precision is 2.814 m,which is still lower than the 2.738 m of joint orbit determination with 1 hour arc;It was not until the arc length of orbit determination only by ODTT increases to 4 hours that the orbit determination precision can reached the same level as the joint orbit determination with1 hour.Therefore,the method of joint short arc orbit determination proposed in this thesis can increase the speed of orbit recovery after maneuvering to four times and achieve high-precision and high-efficiency orbit recovery after GEO satellite maneuver.In addition,the role of VLBI in orbit determination with 10 minutes ultra short arc is significant,and oritbt recovery of GEO after a maneuver can be achieved with the precision better than 10 m by VLBI joint ODTT.