Earlier this week, the International Space Station (ISS) was forced to dodge a possible collision with space debris. With a crew of astronauts and cosmonauts on board, this required an urgent orbit change on 11 November.
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 misses occurred in 2020.
In May of this year, there was a hit: a tiny piece of space debris punctured a 5mm hole in the ISS robotic arm, built in Canada.
This week there was an incident involving the wreckage of a defunct weather satellite, Fengyun-1C, 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 have already entered 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, now over 400 km (250 mi) high, by about 1.2 km (0.7 mi).
The orbit overflows
Space debris has become a serious 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 (4.75 miles) per second, 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 injury. 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 operational with many more on the way.
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 (4 inches) in orbit in orbit, such as dormant satellites and rocket stages. There are also about a million sizes from 1 to 10 cm, and 330 million in size from 1 mm 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 with 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.
Watching the sky
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 over 10 cm in size are being 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 – home to many communications satellites, including those in use in Australia.
One way or another, we will ultimately have to clean up our space neighborhood if we want to continue to benefit from the nearby regions of the “last frontier”.
Mark Rigby, Research Fellow at the University of South Queensland and Brad Carter, Professor of Physics at the University of South Queensland.
This article is reprinted from The Conversation under a Creative Commons license. Read the original article.