House lasers and clever antennas are necessary conditions for satellite tv for pc broadband
An illustration of mynaric laser communications sending data across a constellation of low earth satellites. (Image: Mynaric)
There are many innovations in the making of satellite broadband delivery by companies like SpaceX and Telesat. Two cutting-edge technologies are key to making low-earth orbit satellite (LEO) broadband networks faster and cheaper: lasers and Active Electronic Steered Array (AESA) antennas. Rapid development of both is important to reduce latency and costs.
Frickin ‘laser beams
Laser links or optical communication between satellites form the basis for the next generation of SpaceX Starlink satellites as well as for satellites from Telesat and Amazon Project Kuiper. Two companies that can be seen in this area are BridgeComm and Mynaric.
The use of communication relays between satellites is nothing new. The Iridium network currently in operation and the OneWeb satellites in use use radio links to shift communications from satellite to satellite without the need to use a relay station on the earth’s surface. This is a huge benefit when there isn’t an affordable way to build a station in places like the middle of the ocean or at the poles. The use of inter-satellite links also reduces latency because packets do not travel through a ground station and terrestrial network connectivity to relay signals between satellite-linked locations in different parts of the world.
Similarly, the concept of optical free space communication is nothing new in the telecommunications world. Terrestrial devices provide high-speed, point-to-point communication on the ground at speeds of up to gigabits in clear weather, rain and rain, slowing down or blocking transmission – good for desert areas like Arizona or Nevada, less so in Seattle or Vancouver .
Security conscious customers such as the US military and corporations prefer point-to-point laser communications because they are extremely difficult to intercept compared to RF.
Laser advocates mention two additional benefits for intersatellite connections. Light travels 31 percent slower through fiber optic cables than a vacuum. So if you remove the fiber as a transmission medium, the network speed increases. Second, point-to-point laser communication provides a true “straight” path for data, rather than having to follow the rights of way and other meandering paths that occur when fibers are pulled through conduits and distributed across the ocean floor.
The challenge for space lasers is to precisely aim a beam of light and focus it on a receiver with satellites flying at speeds of thousands of miles per hour, and to build space-grade hardware in the quantities required for hundreds and thousands of satellites. Each satellite needs at least four laser communication modules to network with satellites in front and behind it in orbit and with satellites on either side – think “left” and “right” in relation to the satellite’s flight location. In the future, a fifth downward-facing laser module may be incorporated to provide additional high-speed communication between the orbiting constellation and terrestrial networks.
The challenge for space lasers is to precisely aim a beam of light and focus it on a receiver whose satellites travel at thousands of miles per hour.
Various tests have been and are being carried out in orbit to use lasers for both inter-satellite and satellite-to-ground communications. SpaceX comes closest to launching production-based inter-satellite links after being tested on two Starship satellites in 2020 and “v0.9” laser modules launched into polar orbit with 10 satellites in January 2021. All Starlink Satellites will become standard equipment at some point in the future. The company originally planned laser links on its first generation satellites, but the technology wasn’t ready in the timeframe SpaceX required.
Both Telesat and Amazon have built lasers into their satellites from day one. OneWeb is likely to incorporate laser intersatellite links into future generations of its satellites.
LEO’s Holy Grail – Low Cost Antennas
Because LEO satellites are closer to Earth, less power is required to transmit data between the ground and the satellite, and more data can be transmitted for any available amount of RF spectrum. “However, there is no free lunch” applies to LEO satellite constellations as it does to any other technological advancement. Lower orbits mean satellites fly faster across the sky, with a single satellite only flying overhead a few times a day for a few minutes.
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To ensure continuous 24-hour communications coverage, you need a “train” of satellites overhead, with “new” satellites visible as “old” satellites depart, and antennas that can track multiple satellites at the same time.
Commercial users and cruise lines using the O3b MEO (Medium Earth Orbit) and OneWeb networks can use two to three mechanical antennas to track multiple satellites. However, these operators have the luxury of having enough physical real estate for multiple courts and the service contracts to fix them if engines and transmissions break.
Enter AESA, the AESA antenna (Active Electronic Steered Array). Many radio transceivers are arranged in an array and use multiple managed beams to “track” satellites as they come across the sky, rather than mechanically moving a dish. AESA was first used in military radars, resulting in greater reliability and a much faster and more accurate pointing, as well as a much flatter and smaller shape than the traditional dish.
For consumer and enterprise LEO applications, AESA is a much more desirable solution than multiple physical antennas, but the sophistication and sheer amount of circuitry make it terribly expensive to build, with an antenna for a marine vessel costing more than $ 20,000 and antennas for commercial aircraft start at $ 50,000 and quickly higher.
How expensive and complex is an AESA antenna compared to other devices? A high-end cell phone might have four radios and 13 antennas and cost about $ 1,000. The SpaceX Starlink AESA dish has more than a thousand transmit / receive elements (radios) spread across a 19.75 by 21.5 inch physical circuit board – much larger than a cell phone. A Business Insider estimate put the cost of a Starlink court at around $ 2,400 in $ 1 million.
Amazon has shown some of its work developing a lower-cost AESA antenna for its Kuiper project, while Isotropic Systems and Kymeta Corporation are among the companies that are using different technologies to reduce antenna costs. OneWeb and Telesat Lightspeed need a healthy third-party antenna ecosystem for their LEO services to thrive as they don’t build antennas in-house.