LOW EARTH ORBIT SATELLITE

LOW EARTH ORBIT SATELLITE

            Traditionally, communications satellites have operated in geo-stationary orbit (GSO), 35,000 km above the equator, and low Earth orbit (LEO) satellites have been used for weather monitoring, resource mapping, and Earth sensing. By the start of the new millennium, in five years, revolution will have occurred in the communication satellite industry with LEO satellite networks becoming key pathways of the information superhighway.

Low Earth Orbit (LEO) satellites are satellites that operate in orbits of around 100 km to 1,000 km above the Earth’s surface – much lower than traditional communications satellites – which bring them into frequent radio contact with ground stations. LEOs are used for a variety of civil, scientific and military roles including Earth observation, radar, optical, telecoms and demonstrator.

LEO satellite constellations now form a vital link in the expanding communications and observation networks that are essential for global economic development, especially in remote areas. Reliability is therefore a key issue for satellite manufacturers and operators.

Low Earth Orbit satellite must travel very quickly to resist the pull of gravity approximately 17,000 mile per hour. Because of this, Low Earth Orbit satellite can orbit the planet in as little as 90 minutes.

Kinds of LEO

Little LEO

            Little LEO are required to offer non-voice services for example vehicle tracking, environmental monitoring and two-way data communication. A little LEO is a constellation of small, low-earth orbiting satellites, use for short, and narrowband communication. Little LEO are small, Low cost, class of satellites.

Big LEO

            Big LEO are used for technology devices such as high speed, high bandwidth data communications, and video conferencing. They can carry voice and high speed data services. They are aimed at data communications and real time voice into hand held devices. Big LEO can also offer global services, which are also subject to regulatory requirements. 

Advantage of LEO

• A LEO satellite’s proximity to earth compared to a GEO satellite gives it a better signal strength and less of a time delay, which makes it better for point to point communication.
• A LEO satellite’s smaller area of coverage is less of a waste of bandwidth.

Disadvantage of LEO

• A network of LEO satellites is needed, which can be costly.
• LEO satellites have to compensate for Doppler shifts cause by their relative movement.
• Atmospheric drag affects LEO satellites, causing gradual orbital deterioration.