Introduction to Satellite Orbits
What is an orbit?
Orbits are the paths that satellites follow as they travel around celestial bodies, such as the Earth. The choice of orbit is crucial because it determines the satellite's coverage area, the duration it stays over a particular region, and its overall mission objectives. Understanding the different types of orbits is essential for anyone interested in satellite technology, as each orbit serves specific functions and has unique characteristics.
Types of Orbits
(LEO)
Low Earth orbit
-
Altitude: 160 km to 2,000 km above Earth's surface.
-
Characteristics: Satellites in LEO orbit the Earth quickly, taking around 90 minutes to complete one orbit. This orbit is ideal for Earth observation, imaging, and scientific research due to its proximity to the Earth's surface.
-
Applications: Earth observation, remote sensing, communication, and scientific missions.
(GEO)
Geostationary Orbit
-
Altitude: 35,786 km above Earth's equator, from west to east.
-
Characteristics: Satellites in GEO appear to be stationary relative to a point on Earth because they orbit at the same rotational speed as the Earth, 3km per second (23h, 56min, 4s). This orbit is ideal for communication satellites that need to maintain a constant connection with a specific region.
-
Applications: Communication, weather forecasting, and broadcasting.
(MEO)
Medium Earth orbit
-
Altitude: A wide range of orbits anywhere between LEO and GEO.2,000 km to 35,786 km above Earth.
-
Characteristics: MEO is often used for navigation satellites like the Global Positioning System (GPS). Satellites in this orbit have a longer orbital period, meaning they stay over a specific area for a more extended period compared to LEO.
-
Applications: Navigation, communication, and some types of environmental monitoring.
(SSO)
Polar orbit and Sun-synchronous orbit
-
Altitude: From north to south rather than from west to east, passing roughly over Earth's poles. Typically between 600 km and 800 km.
-
Characteristics: 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) is a particular kind of polar orbit. This means they are synchronised to always be in the same ‘fixed’ position relative to the Sun. At 800 km, it will be travelling at a speed of approximately 7.5 km per second.
-
-
Applications: Earth observation, environmental monitoring, and climate studies.
Conclusion
The selection of an orbit is a critical decision in satellite missions, as it dictates the satellite's functionality, coverage, and lifespan. Understanding orbital mechanics is key to optimizing satellite design and ensuring that the mission objectives are met efficiently and effectively.