A Method For Determining Onboard Clock Based On L-Band And C-Band Measurements

Time synchronization is a key technology of satellite navigation system as the basis oftime measurements, directly affecting positioning accuracy. Although satellite clock ishigh stability atomic clock, on board clock error caused by clock frequency drift isknown. So clock solutions play an important role in precision positioning. Analysis ofGNSS clocks performance is traditional carried out by network adjustment analysistechniques where orbits and all participant clocks are computed in a batch or KalmanFilter least-squares adjustment to a reference time scale and reference frame. Clocksolution may reflect radial orbit difference of the corresponding ephemeris, whichpropagate into the clock solutions. Geostationary satellites (GEO) are important partsof navigation satellite constellation. But the high-level precise orbit determination forGEO satellites are difficult to achieve, because the tracking geometry for GEO isalmost unchanged due to the geostationary feature of the GEO satellite, resulting inweak dynamical constraints. GEO satellites are often in the orbit maneuver, duringwhich it will also be difficult to determine the orbit of the satellite. The clockestimation error is correlated with the estimation error of the radial component of theorbit. This paper proposes a new method for determining the offset of GEOnavigation satellite on-board clock that processes ion-free GEO code and phasecombinations together with simultaneous GEO TWSTFT measurements in the modeof transmitting and receiving with the same station (TWTRS for short), which iscalled―combining solution‖. TWTRS is a high precision technique for orbitdetermination that is independent of navigation signal generation. The solution hasnothing to do with satellite orbit, which means that the orbit error does not affect thedetermination of clock onboard.From the principle of C band transponder ranging technique and L band activetracking ranging technique for GEO navigation satellite, combined with measurementerrors in these two types of observation and these error corrections, the theories ofintegrating simultaneous TWTRS observation and L-band navigation measurementsto determine on-board clock solution is mainly studied, and conventional dataprocessing programs are designed and developed. Compass GEO TWTRS and codeand phase pseudo-range data from Lintong and Kashi tracking stations has beenprocessed to character on-board clock. The analysis and evaluation of onboard clockresult has focused on three different aspects.The main contents in this thesis are as following:1. Based on L-band passive and C-band active satellite tracking measurementprinciples, TWTRS and pseudo-range equations are given in details.2. Navigation satellite is observed using transfer tracking system andsimultaneously Compass receiver, which are connected to the same atomic clock as areference at the same ground station site. The integration algorithm based on theTWTRS data and code pseudo-range data and the correction model of error resourcesare discussed in details.3. The actual observed data from Lintong and Kashi tracking stations are processed in program designed by myself and the results are analyzed in differentaspects, such as quadratic polynomial fit, comparison with traditional networkadjustment analysis result and inside closure comparison and so on.The results of the processed data from actual observation show that: thiscombination method can achieve the satellite clock solution without the support of thesatellite orbit, in other words, effectively weakened the couple degree of satellite orbitand satellite clock. So this combining solution with only a single station pseudo-rangeand TWTRS observations, timely and effectively achieve the purpose of the operationof real-time monitoring the satellite clock. The advantage is very obvious in theorbital maneuvering case. Inside and outside accuracy assessment analysis show thatthe integration method can achieve better than2ns clock solution precision.