Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksSimulations and Results6.1.1.2 IGSO Walker ConstellationThe next analysed constellation is a 18 / 6 / 2 Walker constellation with 55 ° inclination. Thismeans• 18 satellites total in the constellation• 6 orbital planes, with the ascending nodes spaced by 60°• 3 satellites per plane, spaced in mean anomaly by 120°• The phase difference adjacent planes is 40°The orbit altitude is fixed by selecting the orbit class IGSO, which means Inclined Geo-Synchronous Orbit. Due to their orbital period of 23 hours 56 minutes (sidereal day), they aresynchronised with earth's rotation rate. At their ascending node, they cross the equator at thesame point every time, leading to the characteristic "8 shape" of the ground track.A special case of this orbit class is the Geo Stationary Orbit (GEO) which remains as a fixedpoint with respect to an earth fixed reference frame. The following picture shows the groundtracks, as well as the ground station locations of a " custom global network" used in thisscenario.Figure 6-3 Ground Tracks of IGSO Walker ConstellationThe following picture shows the minimum visibility of this constellation over a period of 24hours. Although only 18 satellites are present in this constellation, it provides a goodcoverage. There are always more than 4 satellites visible.R. Wolf Page 95