03/09/2022

A study reported in Nature[1], "Satellite mega-constellations create risks in
Low Earth Orbit, the atmosphere and on Earth," in Scientific Reports (May 2021)
by Aaron C. Boley and Michael Byers, says the rapid development of
mega-constellations risks multiple tragedies of the commons. That could include
tragedies to ground-based astronomy, Earth orbit, and Earth's upper atmosphere.
The study asserts that international cooperation is urgently needed, along with
a regulatory system that takes into account the effects of tens of thousands of
satellites.

"[T]he connections between the Earth and space environments are inadequately
taken into account by the adoption of a consumer electronic model applied to
space assets," the authors said. "For example, we point out that satellite
re-entries from the Starlink mega-constellation alone could deposit more
aluminum into Earth's upper atmosphere than what is done through meteoroids;
they could thus become the dominant source of high-altitude alumina."

The authors say their study shows that untracked debris will lead to
potentially dangerous on-orbit collisions on a regular basis due to the large
number of satellites within mega-constellation orbital shells. The total
cross-section of satellites in these constellations also greatly increases the
risk of impacts due to meteoroids. De facto orbit occupation by single actors,
inadequate regulatory frameworks, and the possibility of free-riding exacerbate
these risks.

According to Boley and Byers, in 2 years, the number of active and defunct
satellites in low-Earth orbit (LEO) has increased by over 50%. "SpaceX alone is
on track to add 11,000 more as it builds its Starlink mega-constellation and
has already filed for permission for another 30,000 satellites with the [FCC]."

More than 12,000 trackable debris pieces are already in low-Earth orbit,
typically 10 centimeters in diameter or larger, the study asserts. Including
sizes down to 1 centimeter would raise the debris count to about a million
inferred debris pieces that could threaten satellites, spacecraft, and
astronauts due to their orbits crisscrossing at high relative speeds.

Simulations of the long-term evolution of debris suggest that LEO is already in
the protracted initial stages of a mushrooming collision scenario, but that
this could be managed through active debris removal. The addition of satellite
mega-constellations and the general proliferation of low-cost satellites in LEO
stresses the environment further, the study posits.

[1] https://www.nature.com/articles/s41598-021-89909-7

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