satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioi ...

is said to occupy an inclined orbit around

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

if the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

exhibits an angle other than 0° to the

equatorial plane The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projecti ...

. This angle is called the orbit's

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

. A planet is said to have an inclined orbit around the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

if it has an angle other than 0° to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

plane.

Types of inclined orbits

Geosynchronous orbits

A geosynchronous orbit is an inclined orbit with an altitude of that completes one revolution every

sidereal day Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coor ...

tracing out a small figure-eight shape in the sky.Basics of the Geostationary Orbit By Dr. T.S. Kelso
/ref> A geostationary orbit is 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 not corrected using 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

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

This is a special type of orbit that precesses at 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 same

mean solar time Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Two types of solar time are apparent solar time ( sundial ...

every day. These orbits have an inclination governed by the equation: :

\cos(i) \approx -\left( \frac \right)^\frac

where

i

is the orbital inclination, and

T

is the orbital period.

External links

References