What are the major orbital perturbations affecting LEO satellites?

LEO satellites experience several perturbations from ideal Keplerian motion: Atmospheric drag - dominant below 600 km, causes orbital decay, varies with solar activity; J2 effect (Earth oblateness) - causes nodal regression and argument of perigee precession, used for sun-synchronous orbits; Higher-order gravity harmonics - tesseral terms cause longitude-dependent effects; Solar radiation pressure - affects high area-to-mass ratio spacecraft; Third-body effects - Sun and Moon gravitational pull, more significant at higher altitudes; Atmospheric tides - diurnal drag variation. Quantifying perturbations: Drag coefficient Cd (~2.2), solar activity indices (F10.7), and gravity models (EGM2008). Orbit maintenance compensates for drag. Mission design exploits J2 for repeating ground tracks or sun-synchronous orbits.