Orbit mechanics: orbital period, footprint, visibility window

Orbital Mechanics Fundamentals

Satellite orbital mechanics follow Kepler laws and determine every aspect of constellation design. Orbital period scales with altitude — a satellite at 550 km completes one orbit in approximately 96 minutes, while one at 1,200 km takes about 109 minutes. The ground track footprint depends on the altitude and the minimum usable elevation angle. At 550 km with a 25-degree minimum elevation, each satellite covers a ground circle roughly 1,000 km in diameter. The visibility window, the time a satellite remains usable from a fixed ground point, typically ranges from four to eight minutes for LEO…