When it comes to launching satellites designed to orbit the Earth, there are three potential destinations. These orbits, dubbed low, medium, and geosynchronous Earth orbits, or LEO, MEO, and GEO, respectively, all exist within a specific height window above the planet’s surface. What is the difference between these three orbit heights, and why are LEO satellites expected to be the next big thing?
The basics of satellite orbits
Understanding the popularity of LEO satellite constellations depends on understanding how these different orbits work, both together and separately. Each orbit is at a different height, and each has its own benefits and downsides.
Low Earth orbit satellites hover anywhere from 160 to 2,000 km above the planet’s surface. Medium Earth orbit placements vary anywhere from 2,000 km to 35,786 km, and geosynchronous and geostationary orbits include anything above 35,786 km. For comparison, the average passenger airliner flies at roughly 14 km above the surface.
Each orbit has its own use. Structures like the International Space Station sit in a low Earth orbit. They’re in what amounts to a perpetual free-fall, which is enough to simulate microgravity, but is still technically within the outer edges of the Earth’s atmosphere. Higher orbits are more difficult to reach, requiring more fuel and larger rockets to achieve those heights.
Are LEO satellites the next big thing?
LEO satellite constellations have been in the news a lot lately, especially as SpaceX adds satellites to its Starlink constellation, launching 60 CubeSats at a time. When the constellation is complete, sometime in 2027, there will be 12,000 Starlink satellites providing high-speed low-latency Internet to users around the globe.
CubeSats are tiny, making it easier to carry more of them into orbit at the same time. They can range in size anywhere from 1 lb to 200 lb, but that is still a fraction of the size of more traditional satellites that researchers can only launch one at a time.
LEO satellites are most commonly used for things like surface imaging. Keeping the International Space Station in a similar orbit makes it easier for astronauts to travel to and from the facility.
Building the LEO economy
Space is the future, and the introduction of things like LEO constellations serves a separate purpose. NASA and other space agencies are working to create what they’re calling a Low Earth Orbit Economy. As of 2020, NASA has opened the International Space Station for commercial and business opportunities.
Companies can apply for space or time on the space station, and NASA has even made private astronaut missions possible, though those are limited to two 30-day missions per year.
The goal here isn’t to privatize spaceflight as much as it is to make spaceflight more accessible and attainable for companies outside of the major space agencies. SpaceX and Axiom Space are the first two private companies to contribute to this LEO economy, but they are just the first bricks in what will be the foundation of the LEO economy that will carry the industry into the future.
Downsides of LEO satellite constellations
The idea of LEO satellite constellations might seem like the wave of the future, and in many ways, it is. But there may be some downsides to these planned super constellations. Each new launch of 60 Starlink satellites obscures the sky for days afterward with little white dots as each CubeSat makes its way up to its final position in the sky.
Astronomers have raised concerns about the potential impact this might have on astronomy as a whole. As more satellites join the constellation, the odds rise that one of them will pass across a telescope’s viewscape.
These satellites may also be more vulnerable to cyberattacks simply because they present a larger surface to attack, according to industry experts. This won’t be a large risk right now as the constellations only number in the hundreds.
However, when the super constellation is complete with 12,000 CubeSats circling the planet, the vulnerable surface gets larger and may be more prone to attack. StarLink won’t be complete until 2027, giving the company plenty of time to reinforce the system’s cybersecurity.
There is also the question of exactly how many satellites can fit into orbit before they start crashing into one another, causing a catastrophic cascade known as Kessler Syndrome. Donald J. Kessler projected that eventually, the density of objects in LEO would reach a point where they would just start colliding with each other. Each satellite added to the sky increases that risk.
Looking toward the future – and the stars
Low Earth orbit satellites are quite literally the wave of the future. It might not be long before everything from our Internet to our television and everything in-between is operating on similar advanced technology. They have a few kinks they’ll need to work out, but these constellations are in their infancy. Still, it’s an exciting step in the right direction as we look both toward the future and toward the stars.