In recent years, satellites have become smaller, cheaper, and easier to make with commercially available parts. Some weigh as little as one gram. This means that more people can afford to send them into orbit. Now satellite operators have begun to launch mega-constellations – groups of hundreds or even thousands of small satellites working together – into orbit around Earth.
Instead of one large satellite, groups of small satellites can simultaneously cover the entire planet. Civil, military and private operators are increasingly using constellations to create a global and continuous coverage of the Earth. Constellations can provide a variety of functions, including climate monitoring, disaster management, or digital connectivity, such as satellite broadband.
But in order to cover the entire planet with small satellites, a lot of them are needed. In addition, they must orbit close to the Earth’s surface to reduce coverage disruption and communication delays. This means that they occupy an already busy area of space called low Earth orbit, a space 100 to 2,000 km above Earth’s surface.
There are many problems with introducing so many satellites into orbit, from the dangers of space junk to obstructing our view of the night sky. But the shift to mega-constellations is also a challenge for global space management.
There are nearly 3,000 active satellites in orbit today, and this will skyrocket in the coming years. For example, the European Commission recently announced plans to launch thousands of satellites into orbit around Earth, adding to a growing list of planned mega-constellation launches.
As businesses and governments around the world continue to pursue mega-constellations, it is critical that the governance framework can support the proliferation of activity. There are a number of important issues to consider.
1. Definition
Satellites are regulated nationally and by licensing, guided by the principles of the 1967 Outer Space Treaty. Although the terms constellation or mega-constellation do not appear in the treaty, they are considered space objects, like all other satellites.
As procedures and regulations differ from country to country, the challenge is how to govern mega-constellations without creating legal fragmentation. It is imperative that the topic is discussed at an international level.
Yet there is currently no legally binding definition for a satellite constellation, nor for the newer term mega constellation. Exactly how many satellites make up a mega-constellation is unknown, and each country might view the term as slightly different. Clarity at the international level could pave the way for guidelines specific to mega-constellations that could contribute to the safe and sustainable use of low Earth orbit.
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2. Congestion
Most satellites in low Earth orbit operate between 600 and 800 km above sea level. This is considered a congested area as there are already many satellites. Small satellites have a shorter lifespan than the larger satellites, which usually orbit above low Earth orbit.
However, it can still take up to about 150 years for satellites to be removed, reentering the atmosphere and burning, when they are about 750 km above sea level. Some are deliberately removed by controlled return, and others are designed to fall in an uncontrolled manner. Operators of satellites and mega-constellations must think of ways to reduce the debris generated by these satellites above and beyond the usual procedure, to maintain sustainable use of low Earth orbit.
Given the number of future mega-constellations currently planned, space around Earth called low Earth orbit could easily become a limited resource.
3. Radio spectrum
This applies not only to the physical space, but also to the use of radio. To communicate, satellites use the radio spectrum. With the increase in mega-constellations, there is a danger that operators will “store” radio frequencies and store them before they actually need them.
To avoid this, a United Nations specialized agency for the use of satellite radio spectrum recently updated its regulatory framework and addressed the issue separately from other space regulations. Mega constellations will be placed on a flexible timeline, using only the frequencies they need at the time.
4. Avoid and track collisions
If the low Earth orbit becomes overcrowded with satellite and mega constellations, it will be more difficult to avoid collisions. In September 2019, the European Space Agency had to fire the boosters at one of its satellites to get it out of the way of another satellite, otherwise the two would have collided.
As the runway becomes congested, there may be a need for more collision avoidance maneuvers and better communication between satellite operators.
There are national efforts, mainly in the United States, for satellite tracking and collision avoidance. A system warns satellite operators of potential collision paths and allows course corrections where possible.
Way ahead
Hopefully, mega-constellations will be discussed by member states at the UN as soon as they are able to. While work in committee can be slow and highly political, international guidelines and national licensing procedures must add considerations for mega constellations.
The benefits of constellations and mega-constellations in low Earth orbit for socio-economic and environmental purposes are great. Because of this, it seems likely that the number of constellations will increase in the near future. To avoid problems, the rules and definitions surrounding mega-constellations must be made clear on an international scale.
This article by Lauren Napier, PhD researcher in Space Law and Policy, Northumbria University, Newcastle, has been republished from The Conversation under a Creative Commons license. Read the original article.
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