Types of satellite orbits

What is an orbit? Discuss different types of an satellite orbits? 

An orbit is a path. It's the way something goes around an object in space. The moon goes in orbit around Earth. You're in orbit right now! That's because Earth is following an orbit all the way around the sun. The International Space Station orbits Earth. An object in orbit is called a satellite. A satellite can be natural, like the moon. It can be human-made, like the space station. Earth is a natural satellite of the sun.

Planets, comets, asteroids and other objects orbit the sun. Many planets also have moons. These moons go in orbits around their planets

Types of Orbits according to shape

• Circular Orbit
• Elliptical Orbit

Types of orbits according to height

• Low Earth Orbit- The altitude is between 160- 2,000 Km. For example, Hubble Space Telescope, International Space Station (ISS)
• Medium Earth Orbit- It is also known as Intermediate Circular Orbit (ICO). It lies above the LEO and below the geostationary orbit. 2,000 Km- 36,000 Km.
• Geostationary Orbit- The orbit is circular.
• – It is in the equatorial plane (directly above the equator and thus its inclination is zero).
• – The angular velocity of the satellite is equal to the angular velocity of the earth.
• – The period of revolution of the satellite is equal to the period of rotation of the Earth.
• – The satellite finishes one revolution around the Earth in exactly one day.
• – There is only one geostationary orbit.
• – It is also known as the Geostationary Earth Orbit or the Geosynchronous Equatorial Orbit (GEO).
• – It is at a height of 36,000 Km from the Earth ( 35,786 Km to be precise).
• – The satellite follows the direction of Earth’s rotation.
• – The satellite appears stationary from the Earth.
• High Earth Orbit- It lies beyond 36,000 Km.
• Geosynchronous Orbit- It is not circular.
• – It is not in the equatorial plane but is in the inclined plane.
• – Angular velocity of the satellite is equal to the angular velocity of the Earth.
• – Period of revolution of the satellite is equal to the period of rotation of the Earth.
• – The satellite finishes one revolution around the Earth in exactly one day.
• – There are many geosynchronous orbits.
• Polar Orbit- It passes above or nearly above both the poles of the Earth.
• – It has an inclination of 90º to the equator.
• – The orbit is used for Earth mapping, Earth observation etc.
• – For Example, Indian Remote Sensing Satellites (IRS).
• Sun Synchronized Orbit- It is a special case of the polar orbit.
• – The satellite travels from the North to South poles as the Earth turns below it.
• – The satellite passes over the same part of the Earth at roughly the same local time each day.
• – This orbit can make communication and various forms of data collection very convenient.
• – They are generally medium or low orbits.
• – Uses include for surface analysis and espionage.
• Example– Resource Satellites, Carto Satellites, Ocean Satellites.
• RISAT-1, RISAT-2 (Radar Imaging Satellite)
• RISAT-2 (a coastal surveillance satellite) was launched before RISAT-1(2012) in 2009 the aftermath of the 2008 Mumbai Terror Attacks.
• Indian Mini Satellite (IMS)- part of spying system
• Technology Experiment Satellite (TES)- It is also an IRS. It is an experimental satellite to demonstrate and validate, in orbit, technologies that could be used in the future satellites of ISRO.

Shifting Orbits

• When satellite reaches the apogee* position, an apogee motor is fired and the satellite moves to another orbit.
• * apogee-  the point in the orbit of the moon or a satellite at which it is furthest from the earth.