The Method Of Orbit Determination By Transfer Tracking And Two Way Satellite Time Transfer Protocol Based On Igso Satellites

I1-S was deployed as the inclined geosynchronous orbit(IGSO)test satellite of the Bei Dou Navigation Satellite System.We accomplished the measurement of the orbit of I1-S by adopting the orbit determination by transfer tracking(ODTT)of GEO satellites.The first part of the Ph.D.dissertationis about the design of an ODTT system for IGSO satellites,and the studies on the measurement of orbits of IGSO satellites.The other part of the dissertation is devoted to IGSO-based two way satellite time and frequency transfer(TWSTFT).Currently TWSTFT mainly uses geostationary orbit(GEO)communication satellites as the signal relay.With the development of regional satellite navigation system,the number of satellites with inclined geosynchronous orbit gradually increases.The exploration for the use of IGSO satellites for the purpose of TWSTFT,especially for users in high latitude areas,would be an effectiveuse of the resource.Unlike GEO satellites,IGSO satellites move at relatively high speedsin reference to ground stations,such that the upward and downward paths of signal transmission areasymmetrical when TWSTFT is carried out based on IGSO satellites,which affects the accuracy of TWSTFT.This is a key problem that needs to be solved for an IGSO satellite-based TWSTFT.In this paper,we design the ODTT system of IGSO satellite,carry out the orbit determination test of I1-S satellite,propose a new IGSO satellite-based TWSTFT methodology and verify the concept experimentally.The key results and innovations are as follows:(1)We participated in the design of the retransmission orbit determination system for the IGSO satellite,using the parameters of its onboard C-band transponder of I1-S satellite,with an emphasison the calculation of the links between ground station and the satellite.We also designed the method of ground docking test for the ground station and the onboard transponder before the launch of satellite to ensure that the link design was feasible.(2)Previously the retransmission orbit determination methodology was only used for GEO satellites.We developed the IGSO satellite orbit determination system,and successfully conducted the IGSO satellite orbit determination test.Thus we expanded its application from GEO satellites to IGSO satellites.Specifically,we carried out the retransmission orbit determination test on the I1-S satellite,provided the support for the testing as well as the data for the precise determination of the orbit of the I1-S satellite.The validated results show that the accuracy for distance measurement with I1-S satellite is less than 6cm,and the accuracy for orbit determination is less than 1m,when 5MChip code rate was used.(3)Traditional TWSTFT can only be carried out with GEO satellites.Here we resolve the problem of asymmetric signal transmission path caused by the relatively high speed between IGSO satellite and ground station,and proposed a TWSTFT method based on IGSO satellites.In this method,the error caused by satellite motion is effectively corrected by the ranging data of the self-receiving channel of TWSTFT modem.TWSTFT test was carried out with I1-S satellite.The results show that the two-way comparison method based on IGSO satellite is consistent with that based on GEO satellite,and the degree of agreement is less than 0.4ns.Meanwhile,the performance of TWSTFT based on IGSO satellite was analyzed by the method of three-station closure error.The RMS of three-station closure error is less than 0.8ns.(4)The delay at ground station equipment is an important source of errors in TWSTFT.Based on the measured data,the relationship between equipment delay and temperature was studied.On the other hand,based on the existing retransmission system,a method of measuring the group delay of the onboard transponders was proposed,and a preliminary experimental study was carried out to further improve the orbit accuracy.