Satellite Orbit and Ephemeris Determination using Inter Satellite Links
Share Embed Flag
Download ePaper

Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Satellite Orbit and Ephemeris Determination using Inter Satellite Links Satellite Orbit and Ephemeris Determination using Inter Satellite Links

athene.bibl.unibw.muenchen.de
from athene.bibl.unibw.muenchen.de More from this publisher
11.07.2015 Views

Simulations and ResultsInter Satellite Links6.1.3 Simulation ScenariosThe following scenarios have been evaluated by simulation. Not all possible combinationhave been investigate, but the chosen ones can be regarded as representative. The followingtable shows the investigated combinations.ScenarioGround Only24 Opt. GPS Galileo OCSWith ISLFull Net Red. Net Full Net Red Net RegionalNetIGSO Walker 18/6/2 C. Global C. Global C. Regional18 IGSO on 3 Loops C. Global C. Global9 IGSO 9 GEO C. Custom C. Global C. RegionalLEO 81 / 9 / 1 DORIS Galileo GalileoLEO 72 / 9 / 1 + 9GEODORIS Galileo GalileoGalileo 33 Galileo GalileoGalileo 27 / 3 Galileo GalileoIn the case of GPS and Galileo, "Reduced Net" mean the OCS (Operational Control Systemof GPS), whereas "Full Net" means the proposed Galileo network.For IGSO and GEO constellations simulation have been made using the custom regional andthe custom global network.For LEO constellations, the DORIS network has been used as a "full coverage " network andthe Galileo network as a reduced coverage network.The investigated constellation / network combinations have been processed with and withoutusing inter satellite links.Page 110R. Wolf

Inter Satellite LinksSimulations and Results6.2 Orbit Determination AccuracyThe following chapter deals with the accuracy of orbit determination. The results have beenderived using a numerical simulation of the satellite orbits, tracking geometry and observationerrors. The estimator used for orbit determination has been the real time Kalman filterdescribed in detail preceding chapters. The state vector for each satellite has been:Position errors in X, Y and Z direction (inertial J2000 frame)Velocity errors in X, Y and Z direction (inertial J2000 frame)Clock offset.The unmodelled residual acceleration has been assumed to be−7ma residual < 102sand the stability of the satellite clock has been assumed to be10 − 13sswhich correspond to a medium stability rubidium clock. These values have been added asprocess noise in the Kalman filter process.The simulation step width has been 30 seconds, for the orbit propagation, i.e. the position hasbeen computed for every 30 seconds. Measurements have been take every 5 minutes.The figures in this chapter show the real orbit errors on the left, and the standard deviationson the right. The real orbit errors in radial, along track and cross track direction have beenderived from the position difference in x, y and z direction by TT ( ε ) = ( X − X ) ⋅[ e e e ]r,a,cEstimatedTrueradialalongcrosswhere e denotes the unit vectors in radial, along track and cross track direction.The standard deviations in radial, along track and cross track directions have been derivedfrom the position error sub matrix of the covariance matrix P, which contains the variances ofthe position errors in inertial x, y and z direction. The following equation yields the variancein radial direction. It can easily be modified for the other two directions.σ2radial= eTradial⎡σ⎢⋅ ⎢σ⎢⎢σ⎣2xx2yx2zxσσσ2xy2yy2zyσσσ2xz2yz2zz⎤⎥⎥⋅ e⎥⎥⎦radialThe standard deviation is now obtained by simply computing the square root of the abovevalue.R. Wolf Page 111

Simulations <strong>and</strong> Results<strong>Inter</strong> <strong>Satellite</strong> <strong>Links</strong>6.1.3 Simulation ScenariosThe following scenarios have been evaluated by simulation. Not all possible combinationhave been investigate, but the chosen ones can be regarded as representative. The followingtable shows the investigated combinations.ScenarioGround Only24 Opt. GPS Galileo OCSWith ISLFull Net Red. Net Full Net Red Net RegionalNetIGSO Walker 18/6/2 C. Global C. Global C. Regional18 IGSO on 3 Loops C. Global C. Global9 IGSO 9 GEO C. Custom C. Global C. RegionalLEO 81 / 9 / 1 DORIS Galileo GalileoLEO 72 / 9 / 1 + 9GEODORIS Galileo GalileoGalileo 33 Galileo GalileoGalileo 27 / 3 Galileo GalileoIn the case of GPS <strong>and</strong> Galileo, "Reduced Net" mean the OCS (Operational Control Systemof GPS), whereas "Full Net" means the proposed Galileo network.For IGSO <strong>and</strong> GEO constellations simulation have been made <strong>using</strong> the custom regional <strong>and</strong>the custom global network.For LEO constellations, the DORIS network has been used as a "full coverage " network <strong>and</strong>the Galileo network as a reduced coverage network.The investigated constellation / network combinations have been processed with <strong>and</strong> without<strong>using</strong> inter satellite links.Page 110R. Wolf

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!