Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksOrbit ComputationwhereP S =E/cE Solar constant (nominal 1358 W/m²)c vacuum speed of lightc R reflectivity coefficienta S astronomical unitA area / cross sectionm massr , r S radius vectors of Satellite and Sun respectivelyµ eclipse factorNormally, the "sensitivity" of the satellite to solar radiation, in Eq. 4.2-47 simplified asc R⋅ AEq. 4.2-48mis a complicated function of the satellites shape, used materials and attitude with respect to thesun. But for generic system level studies, this simplification is absolutely sufficient.The eclipse factor µ determines the amount of solar radiation acting on the satellite, beingdefined asµ = 1 for complete sun lightµ = 0 for umbra phase0 < µ < 1 for penumbra phaseOccultation of the Sun can arise from Earth or Moon. It depends on the model, whether thepenumbra phase is taken into account or not. Simpler models treat the earth's shadow as acylinder or a cone, more sophisticated models computes the eclipse factor for the penumbraphase from the percentage of the visible sun "disc".4.2.4 Air DragSatellites below 1000 km orbit height are strongly affected by drag forces. Although the airdensity is extremely low at such altitudes, the high velocity of a satellite leads to significantacceleration (or better deceleration), obtained by the following equation:aDcD⋅ A ρ= ⋅ ⋅ Dr ⋅ rDm 2wherea D Acceleration due to air dragc D Drag coefficientEq. 4.2-49R. Wolf Page 33