Difference between GEO, MEO and LEO Satellite Systems: Satellite Constellations and Advanced Earth Observation

By: | Updated: Nov-11, 2022
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Difference between GEO, MEO and LEO Satellite Systems

Different orbits are now used to place numerous artificial satellites, most common being GEO, MEO, and LEO. The orbit chosen for a satellite depends on its purpose. The specific orbit chosen for a satellite depends on many factors, among them the function of the satellite as well as the territory it needs to monitor and study. More so, there are different types of satellites designed for particular purposes, which also has a huge role in deciding on which orbit they should reside.

It is quite clear that the lower the orbit of a satellite, the more it is affected by the Earth’s gravity and the greater the speed required to overcome this force, and vice versa. But what does that mean for GEO, MEO, and LEO satellite constellations and the purposes they serve? In this piece, we will cover the specifics of each orbit and describe what a satellite constellation is and how it can benefit world industries from different altitudes.

Where Satellites Reside

A satellite must be properly placed on the right orbit after it has been launched. It rotates in a special way and serves for scientific, military, or other purposes. It’s critical to choose the correct orbit for a satellite based on its technical characteristics and the purpose it’s about to serve.

LEO Satellites

The location of the Low Earth Orbit, which is between 200 and 1,200 kilometers above the Earth, indicates its relatively low altitude above the surface of our planet. However, it is still located above the altitude limits that are available to ordinary aviation.

The low location of this orbit above the Earth determines a number of its characteristics:

  • The revisit period of a satellite is much shorter 
  • The time of a radio signal delay is shorter 
  • Space radiation levels are lower 
  • Less energy is needed to get a satellite into LEO orbit, hence saved money on the launch.

A LEO satellite constellation can experience decrease in velocity due to the friction of the satellite against the gasses, especially for satellites in the lower part of the orbit. Therefore, for practical purposes, a minimum orbital altitude of 300 kilometers above the Earth’s surface is usually used, since below this altitude the friction of the spacecraft against gasses increases. Among other Low Earth Orbit satellite constellation traditional challenges is that LEO is a very crowded place. However, the situation is even worse due to its clogging by the so-called “space debris”.

MEO Satellites

Such satellites will orbit at least at 5,000 altitude. The signals transmitted from the MEO satellite travel a shorter distance. This improves the signal strength at the receiving end. These satellites are used for high speed telephone signals. It takes a constellation of a dozen or more MEO satellites to cover the entire Earth.

GEO Satellites

These satellites are usually used for satellite television. They are located above 35,000 km from the Earth’s surface and have the same speed as the Earth. Consequently, these satellites are considered stationary relative to the Earth because they are synchronized with the planet’s rotation. Such satellites are used for weather forecasting, satellite television, satellite radio, and other types of global communications.

What Are Satellite Constellations and What Are They Used For?

So, what is a satellite constellation? In fact, it’s a network of identical satellites developed and launched for the same purpose. They can be controlled simultaneously and are set to operate as a system where each of the units compliments the other. 

EOS SAT Satellite Constellation

One example of a new satellite constellation that is on its way is EOS SAT by EOS Data Analytics. The company specializes in satellite imagery analytics with the help of AI and offers its own software products to benefit different industries. Having such expertise and knowledge in the industry, it was only natural to make the next step and launch its own satellite constellation.

EOS SAT will be focused primarily on agriculture, but will also greatly benefit forestry and other industries where vegetation monitoring is essential. It will consist of seven small satellites launched to the LEO orbit to rotate around the Earth sun-synchronically.

The uniqueness of this constellation is that it will be equipped with optical sensors able to acquire data within 13 bands that are related to agriculture. For those who need radar images that do not require sun radiation, they can be found on EOSDA LandViewer as it offers imagery from the Sentinel-1 — SAR satellite constellation.

All 7 satellites of the constellation are set to operate on the orbit by 2025. The precise data they will provide will be useful for agriculture and related businesses and will include information on soil moisture, crop health, plant growth stages, field boundaries detection, crops mapping, and yield forecasting.

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