EOS-03 satellite

Types of orbit-

Geostationary orbit (GEO)- 

• Satellites in GEO circle Earth above the equator from west to east following Earth’s rotation – taking 23 hours 56 minutes and 4 seconds – by travelling at exactly the same rate as Earth. 
• This makes satellites in GEO appear to be ‘stationary’ over a fixed position. 
• GEO is used by satellites that need to stay constantly above one particular place over Earth, such as telecommunication satellites. 
• It can also be used by weather monitoring satellites, because they can continually observe specific areas to see how weather trends emerge there.
• Satellites in GEO cover a large range of Earth so as few as three equally-spaced satellites can provide near global coverage. 

Low Earth orbit (LEO)-

• A low Earth orbit (LEO) is an orbit that is relatively close to Earth’s surface. 
• It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth.
• LEO satellites do not always have to follow a particular path around Earth in the same way – their plane can be tilted. 
• This means there are more available routes for satellites in LEO, which is one of the reasons why LEO is a very commonly used orbit.
• It is the orbit most commonly used for satellite imaging, as being near the surface allows it to take images of higher resolution. 
• It is also the orbit used for the International Space Station (ISS), as it is easier for astronauts to travel to and from it at a shorter distance. 
• A satellite takes approximately 90 minutes to circle Earth, meaning the ISS travels around Earth about 16 times a day.
• Individual LEO satellites are less useful for tasks such as telecommunication, because they move so fast across the sky and therefore require a lot of effort to track from ground stations.

Polar orbit and Sun-synchronous orbit (SSO)

• Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km.
• Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth’s poles.
• Sun-synchronous orbit (SSO) is a particular kind of polar orbit. 
• Satellites in SSO, travelling over the polar regions, are synchronous with the Sun. 
• This means they are synchronised to always be in the same ‘fixed’ position relative to the Sun. 
• The satellite will always observe a point on the Earth as if constantly at the same time of the day.
• Such satellites are used to investigate how weather patterns emerge, when monitoring emergencies like forest fires or flooding or to accumulate data on long-term problems like deforestation or rising sea levels.

Transfer orbits and geostationary transfer orbit (GTO)-

• Transfer orbits are a special kind of orbit used to get from one orbit to another. 
• Some satellites are not always placed directly on their final orbit and are instead placed on a transfer orbit, where, by using relatively little energy from built-in motors, the satellite or spacecraft can move from one orbit to another.
• This allows a satellite to reach, for example, a high-altitude orbit like GEO without actually needing the launch vehicle to go all the way to this altitude.