What is orbital inclination?
Orbital inclination is the angle between the plane of a satellite's orbit and Earth's equatorial plane, measured at the ascending node where the satellite crosses the equator from south to north. An inclination of 0° is a perfectly equatorial orbit (geostationary satellites); 90° is a polar orbit passing over both poles; angles between 0° and 90° are prograde (same direction as Earth's rotation); angles between 90° and 180° are retrograde.
Coverage implications
A satellite's inclination directly limits the latitude bands it overflies. A satellite in a 53° inclined orbit (like early Starlink shells) covers latitudes from 53°S to 53°N — missing the polar regions. A 98° inclined sun-synchronous orbit covers all latitudes including the poles. This is why Starlink supplements its 53° constellation with a 97.6° polar shell to serve Alaska, Canada, Scandinavia, and Antarctica. For LEO constellations, the mix of inclinations determines the distribution of capacity across latitude bands: mid-inclination orbits concentrate coverage over mid-latitudes where population density is highest.
Inclination maintenance
For GEO satellites, the Sun and Moon's gravitational pull causes the orbital inclination to drift away from 0° at approximately 0.75° per year. Maintaining strict geostationary position requires north-south stationkeeping manoeuvres to counteract this drift — consuming approximately 90% of a GEO satellite's propellant over its lifetime. Satellites that exhaust their propellant for north-south stationkeeping can often continue limited operation in an inclined GEO (IGSO) orbit, where they trace a daily figure-eight path (analemma) over their nominal longitude.