Satellite Evolution: from GEO to LEO
Looking at the evolution of space technology, there is a shift from the historical satellite communications revolved primarily around the Medium Earth Orbit (MEO) or the Geosynchronous Equatorial Orbit (GEO) towards Low Earth Orbit (LEO).
Referring to circular orbit, satellites can be distinguished based on altitude into three ranges:
• LEO (Low Earth Orbit): at an altitude of 500–2000 km above the Earth secures the continuity of coverage by satellite network with satellites ranging from 50 up to 100 satellites and delay range in link "UE-Satellite" of 3-30 ms;
• MEO (Medium Earth Orbit): located at an altitude of 8000–20.000 km over the surface of the Earth, providing full coverage of the Earth by satellites ranging from 10 up to 12 satellites with delay range in link "UE-Satellite" of 27-90 ms;
• GEO (Geostationary Orbit: located at an altitude of 35.786 km, providing full coverage of the Earth by a constellation ranging from one up to three satellites with delay range in link "UE-Satellite" of 120-280 ms.
MEO and GEO follow earth’s 24-hour orbital cycle from an altitude of more than 35,000 kilometers, therefore only a small number of these satellites are needed to cover most of the planet’s surface. However, these satellites are large, complex and also very costly.
On the other hand, LEO satellites sit closer to the Earth, are smaller in size and have a shorter lifespan. Therefore, in order to ensure the same coverage, LEO satellites are usually launched grouped in constellations. LEO satellites provide multiple benefits, such as:
• Higher bandwidth and speed
• Enabling low-latency communications
• Are much less expensive, both per unit and launch costs
In a nutshell, the competitive prizes are opening space as a viable market to more companies and connectivity services, shifting from customized and handcrafted systems to mass production and automation.