Over the 23 years of the station’s existence in orbit, there have been about 30 close collisions with orbital debris, requiring evasive actions. Three of these near-misses occurred in 2020. In May of this year, there was a hit: a tiny piece of space debris punctured a 5mm hole in a Canadian-built ISS robotic arm.
This week there was an incident involving the wreckage of the defunct meteorological satellite Fengyun-1C, which was destroyed in 2007 by a Chinese anti-satellite missile test. The satellite exploded into more than 3,500 debris, most of which are still in orbit. Many are now in the ISS orbital region.
To avoid a collision, the Russian supply ship Progress, docked at the station, fired missiles for just over six minutes. This changed the speed of the ISS by 0.7 meters per second and raised its orbit, already over 400 km, by about 1.2 km.
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Orbit becomes crowded Space debris has become a major problem for all satellites orbiting the Earth, not just the ISS the size of a football field. Besides famous satellites such as China’s small space station Tiangong and the Hubble Space Telescope, there are thousands of others.
As the largest manned space station, the ISS is the most vulnerable target. It spins at 7.66 kilometers per second, which is enough to get from Perth to Brisbane in less than eight minutes.
A collision at this speed with even a small debris can cause serious damage. What matters is the relative speed of the satellite and the debris, so some collisions can happen slower while others can happen faster and cause even more damage.
As more and more people in low-Earth orbit become, more and more have to be faced. Nearly 5,000 satellites are already in operation, with many more in the pipeline.
SpaceX alone will soon have more than 2,000 Starlink internet satellites in orbit, approaching an initial target of 12,000 and possibly ultimately 40,000.
If only the satellites themselves were in orbit, things might not be so bad. But according to the European Space Agency’s Space Debris Administration, there are about 36,500 man-made objects larger than 10 cm in orbit, such as inoperative satellites and rocket stages. There are also about a million in sizes ranging from 1 to 10 cm and 330 million in sizes ranging from 1 to 1 cm.
Most of these objects are in low Earth orbit. Due to the high speeds, even a speck of paint can enter the ISS window, and a marble-sized object can enter the module under pressure.
ISS modules are protected to some extent by a multilayer shield to reduce the likelihood of puncture and leakage. But the risk remains that such an event could occur before the ISS reaches the end of its life around the end of the decade.
Of course, no one has the technology to track every debris, and we also have no way of getting rid of all that junk. However, possible methods for removing larger parts from orbit are being investigated.
Meanwhile, nearly 30,000 objects larger than 10 cm are tracked by organizations around the world, such as the US Space Observation Network.
Here in Australia, space debris tracking is becoming an increasingly active area of activity. Numerous organizations are contributing, including the Australian Space Agency, Electro Optic Systems, the ANU Space Institute, the Space Surveillance Radar System, the Industrial Science Group and the Australian Machine Learning Institute with funding from SmartSat CRC.
In addition, the German Aerospace Center (DLR) has a SMARTnet facility at the Mount Kent Observatory of the University of South Queensland, designed to monitor the geostationary orbit at an altitude of about 36,000 km, where many communications satellites, including those used by Australia, are located.
One way or another, we will eventually have to clean up our space neighborhood if we want to continue to benefit from the immediate regions of the “last frontier”.