Research On Key Technology Of Passive Orbit Determination Of GEO Satellite

Following the development of science and technology and the continuous progress of human society,artificial satellites and related technologies have been widely used in engineering and people's daily life.As the basis of satellites,the orbit product plays a vital role in satellite control and applications.The precise orbit determination(POD)technology commonly based on active signals,such as Unified S-Band(USB)system,Satellite Laser Ranging(SLR)network,Orbit Determination by Transfer Tracking(ODTT)technology,etc.However,this type of technologies has certain requirements for the satellites,related on-board payloads are required for USB or SLR,ODTT technology has requirement for the transponder resources.It is not suitable for unknown satellites.In fields such as radio monitoring,passive orbit determination is required.Therefore,there is an urgent need to develop a passive orbit determination technology,to achieve interferometric measurement and orbit determination by passively receiving satellite signals.This will have a great effect on the application and promotion of satellite technologies.For interferometers based on radio observation,there is no need to understand the content and modulation of the signal.Time difference of the signal arrival at stations can be get through correlation processing when the satellite is not silence,and then orbit products can be obtained.Therefore,this technology can be used for satellites that do not have communication links to POD stations.However,these type of technology(like VLBI)are commonly used in radio astronomy,which has high accuracy but complicated and expensive system.There are many key technologies that need to be overcome to establish a passive orbit determination system based on artificial satellites.This dissertation focuses on the research and discussion of the key technologies,the main achievements and innovations are as follows:1.The technology of common-view time and frequency transfer based on GEO communication satellite and the technology of precise common-view time and frequency transfer based on Bei Dou GEO satellite are proposed in this dissertation.And combining these two technologies,inter-station high precision passive time transfer is achieved.In a passive orbit determination system,if the connection interference technique(CEI)is deployed,the influence of the clock difference can be eliminated by using a common frequency source;if the VLBI technique is used,the clocks of each station must be synchronized with high precision to proceed the orbit determination.There are some shortages with the existing time transfer technology: the accuracy of pseudo-code common view is relatively low,integer ambiguity problem needs to be solved in the PPP technology,and the TWSTFT needs the emit signals.In order to enrich the time transfer technology of passive orbit determination systems,this dissertation proposed the common-view time and frequency transfer technology based on communication satellites,the precise common-view time and frequency transfer technology based on omnidirectional\directional antenna observation,and the application of Vondrak–Cepek smoothing method.The above-mentioned technologies are passive high-precision time transfer technologies,which can be used in passive orbit determination systems.2.Based on the strong signals of satellite,the narrow-band satellite interferometry technology was proposed,the data collection system for satellite interferometric measurement and related prototype software were developedMost of the current data collection systems for interferometric time measurement are based on radio source observation.The equipment has high accuracy and wide bandwidth.But the amount of data will be large and difficult to transfer or process,which is not convenient for popularization and application.This dissertation develops a data collection system and related software for satellite interferometric time measurement based on a software defined radio platform.The bandwidth of this system is adjustable.For strong satellites signals,narrowband mode can be used to collect data to reduce the amount of data and facilitate network transmission and data processing.In order to verify the performance of the system,software defined radio devices are used to alter part of the existing antenna systems of the ODTT network,thereby building a test platform and carrying out zero and short baseline experiments.Fine test results were obtained during the experiments.3.The system delay correction technology using Beidou GEO satellite as reference is proposed,and the passive orbit determine experiment of GEO satellite are carried out,which verified the effectiveness of the system delay correction technologyWhen using VLBI technique to observe satellite,the system delay was often corrected by cross-observation of dense radio sources with known precise positions.However,the passive orbit determination system cannot observe radio sources,it is necessary to develop a satellite-based system delay correction technology.The Beidou system has GEO satellites with precise orbit products and continuous broadcast signals;thus,they can be used as reference satellites.However,when the target satellite is away from the reference satellite,the system difference cannot be eliminated directly.This dissertation proposes a system delay correction technology using Beidou satellite as the reference.The technology uses precision orbit data of Beidou GEO satellite,combine with the clock bias and atmospheric products to separate the equipment delay for calibration.Experiments are carried out to verify the technology.The result shows that this technology has the same accuracy as the result of calibration technology based on radio sources.