Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksSoftware Description∆IO40.3= ⋅ TEC2fEq. 5.3-20whithTEC Total Electron Content along the signal pathf FrequencyThe error of the model has been assumed to be 50%. This value is added to the observationvariance.5.3.3 Tropospheric ModelA radio signal is also subject to tropospheric refraction, causing a delay in the signal receptiontime, similar to the ionospheric delay, but much less in magnitude. There are severaltropospheric models in use. The one utilised in the simulations is the Saastamionentropospheric model [HWL-94].with∆pTeTr0.002277= ⋅ (p +πcos( - δ)21255π( + 0.05) ⋅ e - tan( - δ))T2atmospheric pressureTemperaturePartial pressure of water vapourEq. 5.3-21δ ElevationIt can be assumed as sufficient to take average values for p and T and e. The residual error hasbeen assumed as 20 % of the result from above equation.5.3.4 Multipath SimulationMultipath is not easy to model, but can be assumed as being a more or less slowly varyingbias. It was simulated using the functionyA⋅sinωt= eEq. 5.3-22which resembles a multipath figure with a slowly varying geometry. All delays and errorshave been added to the measurements as biases.R. Wolf Page 83