Orbital Decay

Orbital decay is the progressive loss of altitude experienced by objects in low Earth orbit due to friction with the residual upper atmosphere. Even at 400 km, there are enough gas molecules to create measurable drag. As the orbit lowers, the satellite encounters denser atmosphere, increasing drag further — creating a positive feedback loop that accelerates until re-entry. The rate depends on altitude, solar activity (which expands the atmosphere), the object's ballistic coefficient (mass-to-area ratio), and orbital eccentricity. At 300 km, an object may deorbit in months; at 800 km, it could take centuries.