Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksSoftware DescriptionCode Range measurement precision performance of a DLL:dBL2σ τ=± D ( 1 + )2C/N ( C/ N ) T0 0Phase measurement precision performance of a PLL:λσ =± BLp( ) (τπ /+ 11)2 C N 2( C / N ) T0 0Doppler measurement precision performance:iiEq. 5.3-9Eq. 5.3-10θDopplerωL ωL NEq. 5.3-11o=2 2 ξ CwithT i Integration timeC/N 0 Carrier noise densityD Chip lengthB L B LP Noise bandwidth of tracking loopλ Wavelength of carrierω L Natural angle frequency of a PLLζ Attenuation factor of a loop filterd Early-late spacing of DLL (d=0.01 ... 1)From the equations above, generally a quadratic relationship between the distance and themeasurement noise can be derived for code and phase measurements. In the following it willbe shown that for realistic values the relationship is nearly linear.Let us assume some typical values for a GPS like scenario:Chip length D300 mCarrier wave length λ19 cmBandwidth of phase lock loop (PLL) B Lp 20 HzBandwidth of delay lock loop (DLL) B L 1 HzEarly late spacing of DLL d 0.1Integration time T I20 msR. Wolf Page 77