Satellite Orbit and Ephemeris Determination using Inter Satellite Links
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Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Satellite Orbit and Ephemeris Determination using Inter Satellite Links Satellite Orbit and Ephemeris Determination using Inter Satellite Links

athene.bibl.unibw.muenchen.de
from athene.bibl.unibw.muenchen.de More from this publisher
11.07.2015 Views

Orbit ComputationInter Satellite Linkscross track however error shows a periodic error characteristic, with the orbital period as anatural frequency and increasing amplitude. This characteristic also superimposed to the(linear) secular tendency in the radial error.3.02.5Radial0.10Cross TrackOrbit Error [m]2.01.51.0Orbit Error [m]0.050.00-0.050.50.0-0.1006:39:30.000 13:19:30.000 19:59:30.000UTC [hours:minutes:seconds]06:39:30.000 13:19:30.000 19:59:30.000UTC [hours:minutes:seconds]Figure 4-9 Radial / Cross Track Error of 800 km LEO neglecting Air DragThus, for satellite orbits below 1000 km, air drag has to be modelled.Page 54R. Wolf

Inter Satellite LinksOrbit Computation4.3.5 Other PerturbationsOther forces which contribute to the orbit perturbations are• Solid earth tides• Ocean tides• Albedo (reflection from earth)• Third body attraction due to major planetsIn this section, only a few of them will be considered. LEO satellites are subject toperturbations from earth albedo, solid earth tides and ocean loading tides. These perturbationscan be of non negligible magnitude in orbits below 800 km. Here, the major focus is onsatellite orbits suited for navigation applications. A constellation consisting of LEO satellitesrequires a high number of space craft to make sure that always a minimum of four spacevehicles are visible from any location on earth. The required number increases withdecreasing orbit height, thus a navigation constellation would have an orbit altitude above1000 km. Therefore, only two of the minor perturbation are shown in this section.Figure 4-10 and Figure 4-11 show the prediction error due to neglecting solid earth tides. Forthe 800 km LEO, the error is quite noticeable after one day, but for the MEO it is almostnegligible.50Orbit Error [m]-5-10-15-20-25RadialAlong TrackCross Track-30-3506:39:30.000 13:19:30.000 19:59:30.000UTC [hours:minutes:seconds]Figure 4-10 Orbit Error of 800 km LEO neglecting Solid Earth TidesR. Wolf Page 55

<strong>Orbit</strong> Computation<strong>Inter</strong> <strong>Satellite</strong> <strong>Links</strong>cross track however error shows a periodic error characteristic, with the orbital period as anatural frequency <strong>and</strong> increasing amplitude. This characteristic also superimposed to the(linear) secular tendency in the radial error.3.02.5Radial0.10Cross Track<strong>Orbit</strong> Error [m]2.01.51.0<strong>Orbit</strong> Error [m]0.050.00-0.050.50.0-0.1006:39:30.000 13:19:30.000 19:59:30.000UTC [hours:minutes:seconds]06:39:30.000 13:19:30.000 19:59:30.000UTC [hours:minutes:seconds]Figure 4-9 Radial / Cross Track Error of 800 km LEO neglecting Air DragThus, for satellite orbits below 1000 km, air drag has to be modelled.Page 54R. Wolf

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