Have you heard of earth orbits??

An earth orbit is a path in space that an object/satellite takes when it goes around the earth.

There are three main Earth orbits:

1) Low Earth orbit (LEO)

2) Medium Earth orbit (MEO)

3) Geostationary orbit (GEO)

Other than this we have Sun-Synchronous orbit (SSO), Geostationary Transfer Orbit (GTO), and Highly Elliptical Orbit (HEO).

Low Earth orbit (LEO): It is the closest orbit from the earth's surface, It is normally at an altitude of 160 to 1000km above the surface. Though it is very far, it is still the closest orbit compared to the other orbits. Being near to the surface reduces transmission time delay to only 0.05 seconds but on the other hand, we required at least 20 or more satellites in LEO to cover the entire earth. satellites in LEO are used for satellite imaging and for communication and remote sensing satellite systems. In this orbit, satellites travel at a speed of approximately 7.8 km per second, at this speed a satellite takes around 90 minutes to complete an orbit.

Medium Earth orbit (MEO): It has a wide range, anywhere between LEO and GEO. Generally at an altitude of 2,000 to 35,000 km, due to its wide range, the satellites at this orbit travels at different speeds and takes anywhere between 2 to 8 hours to complete one orbit but some can even take up to 24 hours. Further, the increase in altitude also increases the scope of the satellite hence it requires fewer satellites compared to LEO to cover the entire earth. Satellites in MEO are commonly used for navigation purposes, like Global Positioning System (GPS), and Galileo (created by the European Union).

Geostationary orbit (GEO): This orbit is at an altitude of 35,786 km and travels at a speed of 3 km per second, making it take 23 hours 56 minutes and 4 seconds to complete one orbit, as being exactly the same rate as Earth, the satellites in GEO appear to be ‘stationary’. As it is farther from Earth’s surface compared to many orbits, satellites in this orbit can cover a much larger area and hence requires only three equally-spaced satellites to provide near-global coverage. Geostationary Orbit Satellites are used for weather forecasting, satellite TV, satellite radio, and other types of global communications.

Sun-synchronous orbit (SSO): It is a particular kind of polar orbit. Satellites in SSO travels from the north pole to the south pole as the Earth turns below it and are in synchronous with the sun, which means they are always placed at a relatively fixed position from the sun. These satellites pass over the same spot at the same local time, this makes communication and data collection very convenient. Satellites in SSO would usually be at an altitude range of 600 - 800 km and at 800km they travel at a speed of approximately 7.5 Km per second.

Geostationary Transfer Orbit (GTO):

This is a special kind of orbit used by satellites to move from one orbit to the other. Satellites launched from Earth are not always placed directly in their orbit, they are first placed in the transfer orbit where they move in a circular or elliptical orbit to reach the desired orbit. This way they use relatively less energy from built-in motors rather than needing a launch vehicle to move from one orbit to the other.

Lagrange points (L-points):

These are specific points far out in space where the gravitational pull of Earth and the Sun is precisely equal to the centripetal force required by a small object to move with them. Hence objects (satellite) sent there tend to remain stable and can thus be ‘anchored’ relative to Earth. These points in space can be used by spacecraft to reduce the fuel consumption needed to remain in position. Of the five Lagrange points, three are unstable and two are stable. The unstable Lagrange points - labeled L1, L2, and L3 - lie along the line connecting the two large masses. The stable Lagrange points - labeled L4 and L5 - form the apex of two equilateral triangles. Scientists have not yet found any use for point L3 since it remains hidden behind the Sun at all times.