Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksOrbit ComputationC snm , S snm Ocean tide coefficients for the tide constituent sθ Argument of tide constitudent sFor a more detailed description see [ITN-96]. The computed deviations are used to correct therigid earth gravity model coefficients. These modified coefficients are then used to computethe gravity acceleration, corrected for ocean tides.4.2.7 Earth AlbedoThe reflection of sun light from the earth's surface produces a force, similar to solar radiationpressure but smaller, acting on the satellite. Unfortunately, the reflected solar flux is subject tothe density of clouds, the angle between satellite, earth and sun etc. A very rough estimate canbe given using the following formula:withΨraAlbedocR⋅ A r= Ψ ⋅ ⋅ m | r |Radiation pressure from earthsatellites position vectorc R reflectivity coefficientA area / cross sectionm masswhere( c , α,...)3Eq. 4.2-56Ψ = fEq. 4.2-57R,Earthis still a function of at least the earth's reflectivity, subject to cloud density and the anglebetween sun earth and satellite. Especially for LEO satellites, earth albedo is hard to model.For higher satellite orbits, earth albedo can usually be neglected.4.2.8 Vehicle ThrustWhen orbit corrections become necessary, an additional force resulting from the vehiclespropulsion system has to taken into account.a Thrust=Tm t()⋅ b() twithT Thrustb Vehicles thrust vectorm(t) Mass being a function of timewhere the mass decrease while fuel is burned and exhausted is described byEq. 4.2-58R. Wolf Page 37