Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Simulations and ResultsInter Satellite Links6.2.1 Optimized GPS Constellation6.2.1.1 Ground Tracking (OCS)The orbit determination accuracy for a GPS satellite using the OCS shows large variations inthe standard deviations. The space vehicle is tracked by 3 station most of the time. For theperiods where it is tracked by only two stations, the covariances increase, although the realorbit errors do not necessarily increase. The real time tracking accuracy is better than 1.2meter in the radial direction, but up to 3 meters in the along track direction.Radial Error [cm] 1993 07 02 19:08 - 1993 07 10 19:0854.0Radial Std. Dev. [cm] 1993 07 02 19:08 - 1993 07 10 19:08120.027.080.00-27.040.0-54.0[h]46 92 138 1840[h]45 90 135 180Along Track Error [cm] 1993 07 02 19:08 - 1993 07 10 19:08174.0Along Track Std. Dev. [cm] 1993 07 02 19:08 - 1993 07 10 19:08291.087.0194.00-87.097.0-174.0[h]46 92 138 1840[h]45 90 135 180Cross T rack Error [cm] 1993 07 02 19:08 - 1993 07 10 19:0836.0Cross T rack Std. Dev. [cm] 1993 07 02 19:08 - 1993 07 10 19:0896.018.064.00-18.032.0-36.0[h]46 92 138 1840[h]45 90 135 180Figure 6-17 Tracking Accuracy with GPS OCSPage 112R. Wolf