Amazon and SpaceX Think Satellite Constellations Are the Key to Faster Internet
You may have seen one of the countless articles peppering news feeds about satellite constellation-based internet connectivity such as Starlink by SpaceX or OneWeb. A few companies have deployed their first satellites, and many more, such as Amazon, have filed applications with the FCC and the International Telecommunications Union (ITU) to get permission to develop their constellations. There are even rumors that Apple is working on a cluster of satellites to provide internet connectivity to its devices. The interest in satellite-based internet is high, and there’s plenty of opportunity for financial gain.
Satellite internet already exists, but it’s a different kind. Almost all satellite internet today is served by massive satellites in geostationary orbit, which means the orbital speed matches the rate of the Earth’s rotation. This gives the impression that the satellite remains at a fixed position in the sky (hence the “stationary” in geostationary). Such an orbit is only possible around the Earth’s equator.
The picture below is a computer-generated image of some known space objects. You can clearly identify geostationary orbit, which is the ring of satellites around the equator.
Geostationary orbit allows telecommunications companies to construct only one satellite that can serve entire regions at once. Geostationary satellites serve upwards of tens of thousands of people at one time, so these satellites must be very large and costly to accommodate sophisticated antennas and processing equipment. One geostationary satellite can typically cost over $100 million to build.
Geostationary satellites are often the only way individuals in remote areas can access the internet. The “satellite dishes” visible on buildings are almost always used to communicate with satellites in geostationary orbit, and are found more frequently in rural areas far away from high-speed fiber links.
Despite their widespread use, geostationary communications satellites have a distance problem. Geostationary orbit is over 25,000 miles above the surface of the Earth, which means that the time it takes radio waves to travel from the Earth to the satellite and back becomes problematic.
Typical round-trip time latency between your computer and a server on Earth is in the tens of milliseconds. When communicating through a geostationary satellite link, however, latencies of 500 milliseconds or more are not uncommon. This will limit the maximum data transfer rate in practice and make latency-dependent applications like gaming all but impossible.
High latency, and its associated impacts on service, is one of the primary drivers for the development of a new kind of satellite network. Additionally, the distance to these satellites necessitates large and highly directional dishes in order to communicate effectively from the ground. The only way to fix latency is to bring the communications satellite closer to Earth.
In order to achieve acceptable latencies, almost all proposed satellite constellations are designed to operate in low earth orbit (LEO). LEO encompasses all orbits up to around 1,000 miles in altitude, but most constellations target orbits lower than 500 miles. At this altitude, satellites move very fast across the sky and can only be seen from a very small patch of the globe. To get a better grasp of this concept, take a look at the image below.
This is precisely why so many satellites are required for coverage of even small parts of the globe. The image below is a diagram of a possible orbital plan for the Starlink constellation. These orbits are precisely tuned such that as one satellite leaves the sky another will be visible in most of North America. Satellites here are represented as dots.
Once deployed, satellite links can offer latencies lower than that of terrestrial links. Most terrestrial traffic is carried via high-bandwidth fiber-optic links. These can transport lots of data (on the order of trillions of bits per second) a long way, but fiber is actually slower than radio despite having greater bandwidth. The speed of light in a fiber-optic cable is around 200 million meters per second, whereas light and radio waves propagating through the atmosphere travel close to 300 million meters per second. Some satellite designs support inter-satellite data links via radio or lasers, allowing traffic to bypass terrestrial networks and reach its destination almost entirely via satellite.
All network designs require some number of ground stations, or ground-based transceivers tasked with taking traffic from satellites and transferring it to terrestrial wired networks. Some designs, such as that of OneWeb’s satellite cluster, will operate almost entirely through ground stations. Other designs, like that of SpaceX and Telesat, will use lasers and radio waves to transfer data between satellites before reaching a ground station. There are trade-offs to each, and this video by professor Mark Handley at University College London provides an overview of different link capabilities.
Despite their potential, there are many problems that may arise if all the proposed satellite networks are eventually developed.
One of the biggest problems with satellite constellations is the sheer number of objects that will end up in space. In fact, the number of man-made objects in orbit around Earth is expected to quintuple in the next decade. This drastically increases the chances of satellites colliding and could produce a scenario like from the movie Gravity, where a growing cloud of space debris wipes out almost all satellites in orbit. In fact, the first inter-satellite collision involved a satellite that was part of a communications cluster. This poses a threat to the future of space exploration.
Satellite clusters also threaten ground-based astronomy. A drastic increase in the number of satellites in the night sky can affect astronomical observations from ground-based telescopes. Many astronomers have warned that satellites are already affecting measurements. The image below shows a cluster of Starlink satellites right after launch. You can imagine how this long train of satellites could disrupt astronomical observation.
A last physical concern is radio frequency (RF) interference. All constellation designs call for a use of radio waves in the microwave portion of the electromagnetic spectrum to deliver service. With so many satellites in space, this can affect receivers on Earth by bombarding them with more electromagnetic radiation and raising the noise floor.
Potential issues also exist on the geopolitical front. Many countries, most notably China and Russia, heavily restrict internet access by forcing all traffic to pass through government-operated gateways within the country. Constellations with inter-satellite links can bypass internet censorship, making them potentially incompatible with government regulations.
Bypassing government censorship sounds like a nice idea in practice, but these constellations are designed to make money. If governments ban them, the corporations developing these networks lose out on customers. A potential way around this is to heavily utilize ground stations and force all incoming traffic to be routed through government servers first. This is the reason that OneWeb decided to abandon inter-satellite links in the first place.
Who will offer satellite services first?
SpaceX is likely to win the race to provide the first commercially available coverage with a next-generation satellite cluster. A commercial rollout with limited coverage is slated for mid-2020. SpaceX is in the unique position of controlling the entire process, from development to operation. Satellite development engineers can work closely with the teams operating SpaceX rockets to ensure maximum efficiency. SpaceX’s Starlink satellites are launched in groups of 60 at a time with startling packing efficiency in the rocket fairing (the nose cone that protects payloads during flight). The image below shows a human next to an almost empty fairing on the left, with the fully loaded Starlink payload on the right.
Satellite internet constellations are something to watch out for in the 2020s. This will likely be the first major revolution in the way massive portions of the population access the internet since dial-up internet. When activated, satellite internet constellations will provide instant competition to the monopoly that some ISPs have in rural areas. Rather than provide inferior service like with geostationary satellite internet, these constellations can provide speeds and latencies rivaling or surpassing fiber.