Greenhouse gas emissions here at ground level are wreaking havoc on the upper atmosphere, earth’s thermosphere, which potentially can cause catastrophic satellite collision in low-Earth orbit.
Earth’s thermosphere extends far into LEO, and greenhouse gas-driven changes in the structure of the upper atmosphere need to be considered when planning satellite operations moving forward, write the authors of a new study just published in the journal Nature Sustainability.
While greenhouse gases warm Earth's lower atmosphere, they cool the upper atmosphere, leading to a concerning global contraction, William Parker, the paper’s lead author and an MIT doctoral candidate in aeronautics and astronautics, told me via email.
Climate change is reshaping the thermosphere, reducing the natural atmospheric drag that we depend on to clear out space debris, Parker told me. As the atmosphere contracts, the consequences of satellite breakups, collisions, and ASAT (antisatellite weapon) tests become even more severe, intensifying the growing hazards in LEO, he says.
When the thermosphere contracts, the decreasing density reduces atmospheric drag — a force that pulls old satellites and other debris down to altitudes where they will encounter air molecules and burn up, says MIT. Less drag therefore means extended lifetimes for space junk, which will litter sought-after regions for decades and increase the potential for collisions in orbit, MIT notes.
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Crowded Orbits
We've launched more satellites in the past five years than had been launched in the preceding 60 years, says Parker. So, this new level of space activity, paired with the climate change component, makes orbital capacity an important topic to ensure long-term space sustainability, he says.
There are over 10,000 satellites drifting through low Earth orbit, which describes the region of space up to 2,000km from Earth’s surface, says MIT. In their new study, the researchers simulated different greenhouse gas emissions scenarios over the next century to investigate impacts on atmospheric density and drag, MIT notes.
Space debris in orbit around the Earth, vector illustration. Space junk, garbage ring around planet ... [+] Earth. Cosmos pollution poster, banner template.getty
LEO Satellites
And by the end of this century, the number of satellites safely accommodated within the altitudes of 200 to 1,000 km could be reduced by 50 to 66 percent, says MIT.
How much of a problem are the Starlink constellations?
Today, Elon Musk’s Starlink constellation operates over 60 percent of all active satellites in Earth orbit, says Parker. In the past year alone, they performed 100,000 collision avoidance maneuvers, dodging other satellites and debris from past collisions, explosions, and anti-satellite weapons tests, he says.
How far are we from a full blown Kessler Syndrome --- the point at which collisions generate debris faster than it can be naturally removed?
Recent research suggests that at certain orbital altitudes, we may have already surpassed the Kessler Syndrome threshold, says Parker. Even if no new satellites were launched into these altitude bands, debris levels would continue to rise as collisions outpace the atmospheric drag that would otherwise clear objects from orbit, he says.
What needs to be done to prevent a Kessler meltdown?
The U.S. Federal Communications Commission recently passed a rule that requires operators to deorbit a spacecraft as soon as practicable and no more than five years after the end of their mission, the authors note.
But currently, individual satellite operators and nations are rapidly expanding their operations, staking claims to different regions of space with little coordination, says Parker. We need international agreements to manage space traffic effectively and ensure the efficient use of low-Earth orbit, a finite and increasingly congested resource, he says.
Global Cooperation
Without binding international regulations, the race to occupy orbital space will continue in an unsustainable and chaotic manner, says Parker. Global cooperation is essential to ensuring long-term stability and safety in low Earth orbit, he says.
The Bottom Line?
We were surprised by the unexpected connection between climate change and the space debris problem, says Parker. The good news is that solving one can help address the other, he says. Reducing greenhouse gas emissions isn’t just good for the planet; it also helps ensure the long-term sustainability of space, says Parker.