# Satellite Communication ## What is Satellite Communication Satellite communication uses artificial satellites orbiting the Earth to relay communication signals between locations on the ground. A communication satellite acts as a relay station in space. A ground station on Earth transmits a signal up to the satellite, called an uplink. The satellite receives the signal, amplifies it, and retransmits it back to Earth, called a downlink. Because satellites orbit at high altitudes, a single satellite can cover a very large area of the Earth's surface, enabling communication between locations that are separated by great distances, including locations where terrestrial communication infrastructure does not exist. ## Types of Satellite Orbits Geostationary Earth Orbit satellites orbit at an altitude of approximately 35,786 kilometers directly above the equator. At this specific altitude, the satellite orbits at the same rate as the Earth rotates, so it appears to remain stationary above a fixed point on the Earth's surface. This means that ground stations can use fixed antennas pointed at a specific position in the sky. A single geostationary satellite can cover about one third of the Earth's surface. The main disadvantage is the very high altitude, which causes significant latency of approximately 500 to 700 milliseconds for a round-trip communication, making geostationary satellites unsuitable for applications that require low latency. Low Earth Orbit satellites orbit at altitudes ranging from about 200 to 2,000 kilometers. Because they orbit much closer to Earth, they provide much lower latency than geostationary satellites. The lower altitude also means that each satellite covers a smaller area of the Earth's surface, so multiple satellites are needed to provide continuous coverage. Low Earth Orbit satellite constellations consisting of hundreds or thousands of satellites are used by services like Starlink to provide broadband internet access globally. Medium Earth Orbit satellites orbit at altitudes between low Earth orbit and geostationary orbit. GPS navigation satellites operate in medium Earth orbit. ## Applications of Satellite Communication Satellite television broadcasting delivers television signals from production facilities to broadcast satellites that beam the signals down to dish antennas on homes and buildings. Satellite internet access provides broadband connectivity to rural and remote areas where terrestrial internet infrastructure does not exist. Maritime and aviation communication depends on satellites to provide communication and internet access to ships and aircraft far from shore or over oceans. Military communication relies heavily on satellites for secure, global communication. GPS navigation systems use a constellation of medium Earth orbit satellites to provide precise location information anywhere on Earth. ## Advantages and Disadvantages Satellite communication can cover extremely remote areas where no other communication infrastructure exists. A single satellite can cover a vast area. Satellite networks can be deployed relatively quickly compared to building terrestrial infrastructure. The main disadvantages are the high cost of building and launching satellites, the significant latency for geostationary satellites, and vulnerability to atmospheric conditions. The cost of satellite internet service has historically been higher than terrestrial broadband, though competitive pressure from low Earth orbit systems is reducing costs.