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The First Satellite Constellations Launched in History
The first satellite constellation in history was launched by Telstar in 1962. The original Telstar satellite operated in a non-geosynchronous orbit, which meant that the availability of transatlantic signals was limited to 30 minutes in each 2.5-hour orbit when the satellite passed over the Atlantic Ocean. Although a true milestone for communications, Telstar’s intermittent availability limited its usefulness, it was an engineering marvel that set the stage for future generations of satellites and constellations. Approximately one year after the launch of Telstar in 1962, the first Geosynchronous Equatorial Orbit (GEO) was achieved in August of 1963 by Syncom3.
GEO satellites sync with the Earth’s rotation, meaning they are always pointing to the same location as the Earth rotates. This ensures that the satellite is always in a fixed position over Earth to provide connectivity 24 hours a day to a particular region. After Syncom3, generations of GEO communication satellites were developed for television, military applications, telecommunications, and internet purposes. However, due to the geometry of GEO orbits, service is centered at the equator, with no coverage provided in the Northern and Southern latitudes of the Arctic and Antarctic regions, respectively.
Developments in Lower Earth Orbit Satellite Communications
Lower Earth Orbit (LEO) satellite networks were proposed to provide truly global coverage, including the polar regions. Of several early LEO constellations launched in the 1990s, Iridium proved to be the most robust, supporting commercial and military applications over the lifespan of its first constellation. In 2017, Iridium began launching the $3 billion upgrade of its 66-satellite constellation.
Today, Iridium NEXT, Iridium’s recently upgraded constellation, offers up to 704 Kbps of bandwidth, nearly a 300x increase over the first-generation Iridium constellation.
The Modern Rise of Lower Earth Orbit Satellite Communications
Since 2014, numerous companies have announced satellite networks using LEO constellations due to their unique advantages. Because LEO satellites are roughly 1,000 km above the Earth’s surface, while GEO satellites are 36,000 km above, radio modems connected to them are small, lightweight, and use very small antennas. Critically for data and voice services, there is much lower latency or signal delays with LEO communications than with GEO.
SpaceX, OneWeb, and Amazon all plan to launch more than 1,000 satellites each in the coming years, signaling the advantages of LEO networks. As evidenced by a slew of new constellations and heavy public and private investments, satellite technology is developing quickly.
SpaceX’s Starlink, Amazon’s Kuiper, and Iridium’s NEXT constellations are all recently launched LEO networks poised to provide powerful, low latency connectivity to millions of consumers and organizations worldwide.
GEO and LEO Satellite Communications for Aviation
In the aviation industry, applications that can benefit from low latency real-time LEO connectivity include Beyond-Line-of-Sight (BLOS) communications, Command-and-Control (C2) applications, real-time weather data, global mapping, and fleet tracking, broadcasting, video and imagery communications, safety services, and artificial intelligence.
GEO satellite constellations serve a different role for aviation. While GEO satellites have higher latency and require more power and bigger antennas, they provide higher bandwidth for business and passenger jets with many simultaneous users. GEO satellite systems are heavier and costlier to operate, so balancing necessity with operational efficiencies is key when selecting Satcom networks. The right network will depend on the requirements of the aircraft and what missions are being served.
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SKYTRAC’s #SatcomSeries focuses on the evolution of satellite communication technology and its application for the aviation industry. Follow along for more articles on the topic.
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