The distance of approximately 36,000 kilometers from Earth refers to a specific orbit known as geostationary orbit. Satellites placed in this orbit are called geostationary satellites. There are several reasons why we deploy satellites in this particular orbit:
Communication: Geostationary satellites are primarily used for communication purposes. By placing a satellite in geostationary orbit, it remains fixed relative to a specific location on Earth's surface. This characteristic allows the satellite to maintain a constant line-of-sight connection with ground-based communication antennas, which simplifies communication services such as television broadcasting, internet connectivity, telephone calls, and data transmission over vast regions.
Coverage: Geostationary satellites provide extensive coverage of a large portion of the Earth's surface. Since they remain fixed relative to a specific point on Earth, they can cover an entire hemisphere, including remote areas and regions where terrestrial infrastructure is limited or nonexistent. This makes them ideal for providing communication services to a wide range of locations, including remote regions, ships at sea, and airplanes.
Stability: Satellites in geostationary orbit appear motionless when observed from the ground because they orbit the Earth at the same rotational speed as the Earth's rotation. This stability allows for the use of smaller and simpler ground-based receiving antennas, as they do not need to track the satellite's movement continuously. It also enables long-duration observations and monitoring of specific areas, such as weather patterns, climate monitoring, and Earth observation.
Ground Station Visibility: Placing satellites in geostationary orbit ensures that ground-based communication antennas can establish and maintain a direct line-of-sight link with the satellite without significant interruptions caused by the Earth's curvature or obstructions. This uninterrupted visibility simplifies communication and data transmission between the satellite and ground stations.
While geostationary orbit has its advantages for communication and Earth observation, other orbits, such as low Earth orbit (LEO) and medium Earth orbit (MEO), are used for different purposes like scientific research, Earth observation with higher resolution, global positioning systems (GPS), and satellite constellations. Each orbit has its own unique characteristics and is chosen based on the specific requirements of the mission or application.