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Kaleb Beebout
<aside> <img src="https://s3-us-west-2.amazonaws.com/secure.notion-static.com/fddf2a37-7eb3-4a44-9b09-07e1393fb420/vzlb.png" alt="https://s3-us-west-2.amazonaws.com/secure.notion-static.com/fddf2a37-7eb3-4a44-9b09-07e1393fb420/vzlb.png" width="40px" /> Published: 4/20/2022 | 17 min Read time | 3340 words
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Multi-orbit satellite systems recently surpassed a critical technical maturity. These technologies represent a massive opportunity that has the promise to unlock substantial performance gains in one of the quickest growing satellite verticals—Low Earth Orbit (LEO) broadband.
Hughes Network Solutions (a subsidiary of EchoStar) and OneWeb, two market leaders in their respective markets, demonstrated seamless handoff between LEO and Geosynchronous Orbit (GEO) satellites on August 26, 2021.
“The test, recorded on August 26 [2021], featured the successful real-time, seamless switching between the Hughes JUPITER 2 geostationary, high-throughput satellite (HTS) and OneWeb’s low latency, high speed LEO constellation.” (source)
The following analysis will provide an introductory technical and business overview to the use of multi-orbit satellite systems in consumer broadband.
Serving internet from satellites is not a new concept. Companies began exploring business-models serving internet from LEO satellites in the 90s, but were met with bankruptcies and financial trouble. Prior to these attempts, expensive, limited bandwidth services were available from communications satellites operating in GEO.
Relevant information about the inherent properties of LEO and GEO satellite systems and consumer internet consumption trends will be discussed below. If you are familiar with space systems, orbits, and related phenomena + theory please skip on to the key differences subtitle.
Space systems, like all physical systems, are governed by the unyielding laws of physics. Orbital altitudes are one of the key parameters of space systems that fall prey to these pesky physics laws. The vis viva equation puts terms to the necessary constant sum of kinetic and potential energy at all points on an orbit. In other words, raising the altitude of an orbiting body in space increases the potential energy which must be accompanied by a reduction in orbital velocity. Vice-versa, a reduction in altitude leads to an increase in orbital velocity.
Low Earth Orbit
LEO satellites occupy orbits roughly lower than 2,000 km above mean-sea-level of Earth. Popular LEO satellite systems often orbit between 350 km and 1200 km. The low altitude of LEO systems results in high orbital velocities. The resultant orbital period, or time to complete a single orbit, is between ~90 minutes and ~120 minutes.
Geosynchronous / Geostationary Orbit
GEO satellites occupy orbits approximately equal to 35,786 km above Earth mean-sea-level. The relatively high altitude compared to LEO orbits results in a much lower orbital velocity. The resultant orbital period of GEO satellites is equal to the rotation of Earth, ~24 hours. Conveniently, a satellite orbiting at the same rotation as Earth will appear stationary to an observer on the surface of the Earth (assuming 0° inclination).
It is helpful to understand how satellite internet works to understand the implications of differences between LEO and GEO satellite internet architectures. Satellite internet uses the satellites as a pass through connecting (1) from the end user’s ground station to the satellite constellation, (2) from the satellite constellation to a gateway ground station, (3) from the gateway ground station to the internet, and (4) back in reverse. Operations and details beyond this basic explanation are not fully necessary to understanding the rest of the analysis.
Physics of Orbital Regimes
Pesky physics laws also dictate the maximum speed of things. GEO altitude, being as high as it is, introduces large delays between satellite and ground station, governed by the speed of light—around 125 milliseconds. To provide context, consider that delays from adding routing legs in terrestrial-based internet architecture are measured on the order of single digit milliseconds. GEO satellites are ill-suited for broadband internet architecture.
Enter LEO satellite constellations. Their low altitude keeps propagation delay between a more tenable 4 milliseconds to 10 milliseconds. However, the low altitude is necessarily accompanied by their inherent high orbital velocities. A large number of satellites are needed to maintain consistent coverage over the surface of the earth. Applications for satellite licenses show an increase in interest for constellations of ~1,000 satellites or greater.
