Orbits and Its Type


What is an orbit?
  • An orbit is the curved path that an object in space (such as a star, planet, moon, asteroid or spacecraft) takes around another object due to gravity.
  • Gravity causes objects in space that have mass to be attracted to other nearby objects. If this attraction brings them together with enough momentum, they can sometimes begin to orbit each other.
Low Earth orbit (LEO)
  • A low Earth orbit (LEO) is, as the name suggests, 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 – which is low compared to other orbits, but still very far above Earth’s surface.
Medium Earth orbit (MEO)
  • Medium Earth orbit comprises a wide range of orbits anywhere between LEO and GEO. It is similar to LEO in that it also does not need to take specific paths around Earth, and it is used by a variety of satellites with many different applications.
Polar orbit and Sun-synchronous orbit (SSO)
  • Polar orbits: Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth's poles.
    • Satellites in a polar orbit do not have to pass the North and South Pole precisely; even a deviation within 20 to 30 degrees is still classed as a polar orbit. Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km.
  • Sun-synchronous orbit (SSO): It 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. This means that the satellite always visits the same spot at the same local time – for example, passing the city of Paris every day at noon exactly.
    • This means that the satellite will always observe a point on the Earth as if constantly at the same time of the day, which serves a number of applications; for example, it means that scientists and those who use the satellite images can compare how somewhere changes over time.

Geosynchronous orbit

  • There’s a sweet spot above the Earth where a satellite can match the same rotation of the Earth. This special position in high Earth orbit is known as a geosynchronous orbit.
  • About 35,786 kilometers above the Earth’s surface, satellites are in geostationary orbit. From the center of the Earth, this is approximately 42,164 kilometers. This distance puts it in the high Earth orbit category.
  • At any inclination, a geosynchronous orbit synchronizes with the rotation of the Earth. More specifically, the time it takes for the Earth to rotate on its axis is 23 hours, 56 minutes and 4.09 seconds, which is the same as a satellite in a geosynchronous orbit.
  • This makes geosynchronous satellites particularly useful for telecommunications and other remote sensing applications.


Geostationary orbit
  • While geosynchronous satellites can have any inclination, the key difference to geostationary orbit is the fact that they lie on the same plane as the equator.
  • Geostationary orbits fall in the same category as geosynchronous orbits, but it’s parked over the equator. This one special quality makes it unique from geosynchronous orbits.
  • Weather monitoring satellites like GOES are in geostationary orbits because they have a constant view of the same area. In a high Earth orbit, it’s also useful for search and rescue beacons.



Lagrange Points: These are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion. These can be used by spacecraft to reduce fuel consumption needed to remain in position.

                                

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