📘 Definition
Orbital inclination is the angle between a satellite's orbital plane and Earth's equatorial plane, measured in degrees from 0° to 180°. An inclination of 0° is an equatorial orbit; 90° is a polar orbit; and values above 90° indicate a retrograde orbit. The ISS orbits at 51.6°, Starlink at 53° (primary shell), GPS at 55°, and most sun-synchronous orbits at 96–99°. Inclination is one of the six classical Keplerian elements that define an orbit.
0°–180°
Range
51.6°
ISS
53°
Starlink
55°
GPS
Understanding Inclination
Why Inclination Matters
A satellite can only image or communicate with latitudes up to its inclination value (and its supplement). A satellite at 51.6° inclination reaches latitudes from 51.6°N to 51.6°S. This is why the ISS's orbit was chosen — it was the highest inclination achievable from Baikonur while keeping launch efficiency acceptable, and it covers most populated areas.