Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Autonomous Onboard ProcessingInter Satellite Links7.4.1 User Position Error due to Normal Orbit and Clock DegradationTo evaluate the effect of orbit and clock degradation, a user at positionLatitude: 48 °Longitude: 11 °(Munich) has been assumed, which computes his position using all satellites in view(approximately 12 SV). The satellites positions are computed using the derived broadcastparameters. The broadcast clock parameters have not been computed, but are assumed to beapplied as well. Thus only the residual degradation effect has been modelled by random walkon the frequency and the resulting error has been added to the range.In the following simulation, no integrity monitoring takes place. The predicted and uploadedbroadcast ephemeris, as well as the clock are subject to degradation. The following threefigures show examples of the true orbit and clock error due to ageing.Radial Error [cm] 1998 07 01 12:17 - 1998 07 02 11:5956.028.00-28.0-56.0[h]4 8 12 16 20Along Track Error [cm] 1998 07 01 12:17 - 1998 07 02 11:5942.021.0-21.00-42.0[h]4 8 12 16 20Cross Track Error [cm] 1998 07 01 12:17 - 1998 07 02 11:5966.033.0-33.00-66.0[h]4 8 12 16 20Clock Error [cm] 1998 07 01 12:17 - 1998 07 02 11:59496.0248.0-248.00-496.0[h]4 8 12 16 20Figure 7-3 Orbit and Clock Degradation of SV 26Page 168R. Wolf