There are many different satellite orbits that can be used depending upon the satellite‘s functions and the area it is to serve.
The lower the satellites orbit the Earth, the stronger the gravitational pull, and this means that the satellite must travel faster to counteract this pull. Further away the gravitational field is less and the satellite velocities are correspondingly less.
A satellite orbits the Earth in one of two basic types of orbits such as Circular and Elliptical satellite orbit.
For a circular orbit, the distance from the Earth remains the same at all times whereas the elliptical orbit changes the distance to the Earth.
Circular orbits are classified into Low Earth Orbit (LEO), Medium Earth Orbit, Geosynchronous orbit, etc.
Most satellites, the International Space Station, the Space Shuttle, and the Hubble Space Telescope are all in Low Earth Orbit.
LEO (180 – 2000 Km) is convenient for installing new instruments, fixing things that are broken, and inspecting the damage.
A geosynchronous orbit, located at 35,790 km has the same orbital period as the sidereal rotation period of the Earth.
It allows satellites to synchronize with the rotation of the Earth (only in time and not in direction).
This makes geosynchronous satellites particularly useful for telecommunications and other remote sensing applications.
One particular form of geosynchronous orbit is known as a geostationary orbit, in which the satellite rotates in the same direction as the rotation of the Earth and has an approximate 24 hour period.
The satellite placed in geostationary orbit remains in the same position relative to the Earth.
It is used by many applications including direct broadcast as well as communications or relay systems.
While geosynchronous satellites can have any inclination, geostationary orbit lies on the same plane as the equator.
Polar Orbit –Satellites placed in polar orbits have an inclination of about 90 degrees to the equator and travels north-south over the poles at lower altitudes.
A satellite in the polar orbit approx. takes 90 minutes for a full rotation. As a result, a satellite can observe the entire surface in the time span of 24 hours.
They are often used for applications such as monitoring crops, forests, and even global security.
Sun Synchronous Orbit –It is a special case of Polar Orbit moving from pole to pole allowing the satellite to pass over any given point of the planet’s surface at roughly the same local time each day.
Since there are 365 days in a year and 360 degrees in a circle, it means that the satellite has to shift its orbit by approximately one degree per day.
These orbits are used for satellites that need a constant amount of sunlight and are useful for imaging, spy, and weather satellites.
Types of Orbits