Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksSoftware DescriptionFunction / ModuleDescription• Clock driftEstimator • Weighted least squares with a priori statisticsPredicted Trajectory"True Trajectory"• Real time Kalman filter• Batch mode Kalman filterForce model integration, used to generate reference trajectory to allowlinearizationForce model integration, but using slightly different force model, used toderive measurementsErrors Simulation • Random walk on solar constantNumber of GroundstationsNumber of links• Random walk on air density• Deviated harmonic coefficientsNot limitedNot limitedMain Output • Covariance of radial / along track / cross track errorForce Model Errors• Instantaneous radial / along track / cross track errorImpact analysis of contributing forces by comparing orbits generated usingdifferent force modelsMain Output • Root mean square of radial / along track / cross track errorBroadcast Ephemeris• Instantaneous radial / along track / cross track errorLeast squares fit of a broadcast model over a time series of satellite positionsin earth-centred-earth-fixed co-ordinatesMain Output • Root mean square of radial / along track / cross track errorIntegrity Analysis• Instantaneous radial / along track / cross track error• User Range Error (URE)A RAIM algorithm is used to compute integrity of one selected satellite for agiven misdetection probability and false alarm rateMain Output • Minimum detectable bias / protection level• Instantaneous radial / along track / cross track error• Error detection flag• Error isolation flag• Type of error identifiedTable 5-1 Main Software FeaturesR. Wolf Page 71