Inclined orbit

Asatelliteis said to occupy aninclined orbitaroundEarthif theorbitexhibits an angle other than 0° to theequatorial plane.This angle is called the orbit'sinclination.A planet is said to have an inclined orbit around theSunif it has an angle other than 0° to theeclipticplane.

Types of inclined orbits

Geosynchronous orbits

See also:Geosynchronous orbit

A geosynchronous orbit is an inclined orbit with an altitude of 37,000 km (23,000 mi) that completes one revolution everysidereal daytracing out a smallfigure-eight shapein the sky.Ageostationary orbitis a special case of geosynchronous orbit with no inclination, and therefore no apparent movement across the sky from a fixed observation point on the Earth's surface.

Due to their inherent instability, geostationary orbits will eventually become inclined if they are notcorrectedusing thrusters. At the end of the satellite's lifetime, when fuel approaches depletion, satellite operators may decide to omit these expensive manoeuvres to correct inclination and only control eccentricity. This prolongs the life-time of the satellite as it consumes less fuel over time, but the satellite can then only be used by ground antennas capable of following the north–south movement, satellite-tracking Earth stations.

Polar orbits

See also:Polar orbit

A polar orbit has an inclination of 90 degrees passing over the poles of the planet on each pass. These types of orbits are often used for earth observation and weather services.

Sun-synchronous orbits

See also:Sun-synchronous orbit

This is a special type of orbit thatprecessesat the same rate that the sun moves along the ecliptic, causing the satellite to rise over a fixed location on the earth's surface at the samemean solar timeevery day.

These orbits have an inclination governed by the equation:

$\cos(i)\approx -\left({\frac {T}{3.795{\text{ hr}}}}\right)^{\frac {7}{3}}$

where$i$is the orbital inclination, and$T$is the orbital period.

See also

• List of orbits
• Orbital inclination
• Non-inclined orbit