The Physics Of Satellites Orbiting Earth

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Satellites orbiting earth will experience external perturbations that can affect the orbit. The primary force acting on the satellite depends on the altitude of the orbit. The most significant effect is caused by atmospheric drag which affects satellites in low earth orbit. Outside of low earth orbit, satellites still experience external forces that could change the orbit however unlike atmospheric drag, the orbit altitude will not necessarily decrease. In addition to atmospheric drag, satellites are subject to thermal drag and gravity perturbations.

Atmospheric Drag: (Author: Emma)

Atmospheric drag effects all spacecraft orbiting earth below 2,000 km, producing both short periodic and slow perturbations. It is the is the largest source of error in modeling the force on many satellites because it is difficult to predict [2]. Atmospheric drag is caused by the collisions of gas molecules with the spacecraft. Over time, the collisions start to decay the orbit. Demonstrating a positive feedback effect, where drag decreases the orbital altitude where the density is greater which produces more drag which then decays quicker. Factors that influence drag are the atmospheric drag surrounding the spacecraft, as well as the spacecrafts drag coefficient, area, mass and velocity [1].

The atmospheric density is not constant and changes with solar activity. The solar magnetic activity cycle is the periodic change in the sun 's activity that lasts around 11 years. During solar maximum,

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