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The University of Southampton

Biggest ever space debris study highlights risk posed by satellite ‘mega-constellations’

Published: 19 April 2017
Space debris
Space debris orbiting the Earth

Current measures to combat the threat posed by space debris may not be enough to prevent collisions in Earth orbit as companies prepare to launch unprecedented numbers of satellites, according to a University of Southampton scientist.

Dr Hugh Lewis, Senior Lecturer in Aerospace Engineering, has told delegates at the European Conference on Space Debris that the launch of the first ‘mega-constellations’ of communications satellites from next year will present an increased risk to Earth’s space environment unless action is taken to reduce their impact.

There are currently about 1,300 active satellites in Earth orbit, but the deployment of huge constellations made up of hundreds or thousands of satellites will vastly increase that number – and bring with it an increased risk of collision.

Many small satellites – especially CubeSats, a type of satellite used in space research – are expected to be launched at the same time.

Companies such as Boeing, OneWeb and SpaceX have filed plans to launch constellations of between 720 and 4,425 small, low-cost satellites as early as next year in an effort to provide high-speed internet coverage worldwide.

Now a team of European experts, led by Dr Lewis and working with the European Space Agency (ESA), has undertaken the biggest ever study into the effects of constellations and small satellites on the space environment.

The engineers used the University of Southampton’s state-of-the-art space debris model and Iridis High-Performance Computing facility to simulate the effects of large constellations and small satellites over a 200-year period.

The simulation was based on the existing satellite population and predicted future space launches, including a mega-constellation and small satellites, with more than 300 different scenarios being investigated.

It showed that adding a mega-constellation to the space environment resulted in a 50 per cent increase in the number of catastrophic collisions – involving the complete destruction of a satellite – over the 200 years, with potentially serious consequences for other satellites and the services they provide to the ground, as well as financial implications for the operators.

These collisions occurred even though the simulation incorporated very good compliance with existing space debris mitigation measures by satellites in the mega-constellation.

Dr Lewis said: “There has been a paradigm shift in the manufacturing of satellites. The cost of making a single communications satellite usually runs to hundreds of millions of pounds, but mass-produced satellites will potentially be much cheaper.

“The constellations that are due to be deployed from next year contain an unprecedented number of satellites – and a constellation launched without much thought will see a significant impact on the space environment because of the increased rate of collisions that might occur.”

As well as damaging or destroying the satellites involved, the debris created by collisions has serious implications for other space-users.

“In the best-case scenario you will cause other users to have to manoeuvre their satellites to avoid the debris, which can temporarily affect the services or data they provide. In the worst-case scenario a satellite is destroyed and the service or data are lost entirely.”

The study concluded that space debris mitigation guidelines need to be updated to incorporate measures to address mega-constellations and small satellite traffic.

Dr Lewis said: “The good news is that there are opportunities for mega-constellation operators to address these issues, through good design and by aiming to do better than the minimum required of them.

“It will be harder for small satellites, CubeSats in particular, to do the same until technology has matured to a level that will enable them to adopt a number of key space debris mitigation measures.”

Actions to decrease the likelihood of collisions for these space systems could include:

  • Decreasing the time that satellites spent in low Earth orbit after the end of their mission. The current guidelines stipulate a maximum of 25 years to bring a satellite out of orbit, a process which can take it across the orbits of other satellites
  • Making satellites smaller and more lightweight
  • The addition of propulsion systems and other features to small satellites
  • Extending a satellite’s active lifespan so not as many need to be launched
  • Deploying missions to remove faulty satellites from orbit

Following the conference the results of the study will be presented to the Inter-Agency Space Debris Coordination Committee (IADC).

The work was funded through the European Space Agency’s General Studies Programme.

The team included engineers from Clyde Space and Belstead Research, in the UK, Airbus Defence and Space and the Braunschweig University of Technology, in Germany, and the National Research Centre, Italy.

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