Satelliittiviestintäverkkoja

Satelliittiviestintäverkkoja, or satellite communication networks, are systems that use artificial satellites to relay and transmit signals across vast distances. These networks are crucial for providing telecommunications services in areas where terrestrial infrastructure is unavailable or impractical to deploy, such as remote regions, oceans, and for mobile communication. The fundamental principle involves ground stations transmitting signals to a satellite in orbit, which then retransmits them to other ground stations or mobile terminals.

Satellites used in these networks can be positioned in various orbits. Geostationary Earth Orbit (GEO) satellites, located approximately 35,786 kilometers above the equator, appear stationary from Earth, offering continuous coverage over a specific region. Low Earth Orbit (LEO) satellites, orbiting at much lower altitudes (typically 160 to 2,000 kilometers), require constellations of many satellites to provide global coverage due to their faster movement and smaller footprints. Medium Earth Orbit (MEO) satellites fall between LEO and GEO in terms of altitude and orbital characteristics.

Key components of a satellite communication network include the satellites themselves, ground stations (also known as earth stations), and user terminals. Ground stations are responsible for sending and receiving signals to and from the satellites, while user terminals can range from large VSAT (Very Small Aperture Terminal) dishes to smaller mobile satellite phones.

Applications of satellite communication networks are diverse and include internet access, television broadcasting, telephony, navigation systems (like GPS), emergency communications, and military operations. Their ability to bypass geographical barriers makes them indispensable for global connectivity and for ensuring communication resilience.