SATELLITES  CLASS

 

 

 

 LEO – Low Earth Orbit

 LEO satellites orbit from 160-2000km above the earth, take approximately 1.5 hrs for a full orbit and only cover a portion of the earth’s surface, therefore requiring a network or constellation of satellites to provide global, continual coverage.

They move relatively quickly across the sky, require many satellites to provide global coverage (600 to 3000+), and cost the most to implement and maintain the constellation due to the large number of satellites, relatively short ~ 5-year satellite lifespan, and the number of earth ground stations required. 

Due to the proximity to Earth, LEO satellites have a lower latency (latency is the time between the moment a packet is transmitted and the moment it reaches its destination) and require less amplification for transmission.

Typical Satellite services: for Aviation: 

- Starlink: Ku Band 

( > 6000 sat) 200 / 50 mbps ,  ALT: 550km,
LAtency <70ms
Rotation 90min

- Oneweb-Eutelsat : Ku BAnd 

(648 sat, ALT : 1200km ) 195/ 32 mbps,
Latency < 100ms,
rotation 109min. 
12 Orbital  planes with 49 satellites /plane 

 
- Iridium NEXT -Certus:  L-Band

(66 sat). ALT 780km,  704Kbps,
Latency 395ms 
6 Orbital planes , 11 satellites/plane
Rotation 101min.

 -  Telesat Lightspeed:  link  KA BAnd and Mil Ka.

 Up to 300 Sat. ALT  1000km
 Low  latency
 In development
 IntelSat 

 Introduction to LEO  Satellites 

 Jonathan's Space Pages

 MEO – Medium Earth Orbit

 MEO satellites are located above LEO and below GEO satellites and typically travel in an elliptical orbit over the North and South Pole or in an equatorial orbit.

These satellites are traditionally used for GPS navigation systems and are sometimes used by satellite operators for voice and data communications.

MEO satellites require a constellation of satellites to provide continuous coverage.
Tracking antennas are needed to maintain the link as satellites move in and out of the antenna range.

GPS  is  a MEO  31 Satellites constellation.

 

 GEO – Geostationary Orbit

 GEO satellites orbit at 35,786 km (22,282 mi) above the equator in the same direction and speed as the earth rotates on its axis.

This makes it appear to the earth station as fixed in the sky.
They maintain a fixed position over a point on the earth, require the fewest satellites for global coverage (3 to 4), and cost the least to implement and maintain due to the 15–20- year longevity of individual satellites. 

The majority of commercial communications satellites operate in this orbit; however, due to the distance from the earth there is a longer latency.

Satellites orbits chart:

Typical Satelite  services:  ViaSat, InmarSAT, IntelSAT.