Space junk: the danger orbits the Earth

The crew of the International Space Station, including German astronaut Matthias Maurer, heaved a sigh of relief in November. “There are no signs of a collision,” cosmonaut Pyotr Dubrov reports to Earth. The crew has been rescued in two spaceships so they can quickly fly back to Earth should the debris hit humanity’s outpost. Shortly before that, Russia had shot down a disused satellite.

Space junk debate after weapons test
Moscow’s test of a so-called anti-satellite weapon has sparked another debate about the danger of space debris. The US armed forces initially spoke of more than 1,500 traceable pieces of rubble that could eventually break into hundreds of thousands of pieces. According to Russian specialists at the state agency Tass, there were more than 220 “dangerous encounters” between the ISS and scrap parts in space in 2020 alone.

“Obviously we were a bit worried that we would have to fly home after three days,” Maurer said of the incident. “Of course that would not have been nice after several years of preparation for this flight. That’s why we were very relieved when the ‘all-clear’ came and we could return to the ISS.” Every few weeks, the crew is warned about debris. “That’s because in space we still leave behind what we bring up and It is therefore very important that space companies dispose of everything as safely as possible,” says Maurer.

Millions of pieces of debris in orbit
Using model calculations, scientists estimate that in total there are about a million particles in orbit larger than a centimeter. If such a large screw were to hit a satellite, experts say it would have the destructive power of a hand grenade. But millions upon millions of smaller pieces of debris, just a few millimeters in size, can also cause significant damage.

The Russian space agency Roskomos is concerned about the growing number of scrap parts. In a collision, the ISS could be damaged or in the worst case destroyed about 400 kilometers above Earth, Roskosmos reports. As larger parts approach, the ISS changes flight altitude.

In ten years it could be critical
Experts currently classify the risk to space travel as “not so great.” In ten years, however, the situation could become critical if humanity does not take countermeasures, Vitaly Gorjuchkin, head of Russia’s space control system, told the Interfax agency.

“The detection and cataloging of space debris makes it possible to predict the occurrence of dangerous situations and to warn against sharing this information,” explains Roskosmos. However, there is still no “international practice” in exchanging information about potentially dangerous objects.

Countries such as Russia, the US, Canada, China, Japan and India, as well as the EU, therefore have options for monitoring space near Earth. Scientists have long been working on how to collect — and avoid — space debris. Roskosmos boss Dmitry Rogozin had demanded that satellite manufacturers be required to take care of their removal.

War in Ukraine puts back efforts
However, it is questionable whether international cooperation will take place in space. The war in Ukraine has divided Russia and the West. Skeptics also see the survival of the ISS in jeopardy.

Manuel Metz of the German Aerospace Center (DLR) has been dealing with space scrap for years. “In many countries, including Germany, there is only a voluntary obligation to avoid scrap metal,” says the German space agency astrophysicist at DLR. A private actor can put satellites into orbit without adhering to guidelines.

“France, on the other hand, has a space law – actors have to provide a lot of details here.” The subject is currently being intensively discussed internationally under the term “space traffic management”.

Thousands of new debris are created in a collision
According to Metz, the greatest density of scrap is about 800 kilometers above the Earth. “These are orbits commonly used by Earth observation satellites.” A collision generates a lot of energy. “An object as small as ten centimeters can crush an entire satellite. Thousands more fragments are thus created.”

The recommendation is to leave obsolete satellites in an orbit of less than 600 to 650 kilometers so that they burn up in the Earth’s atmosphere within 25 years at the latest.

The experts use the GESTRA radar system in Koblenz, among other things, to observe the sky. Developed by the Fraunhofer Institute for High Frequency Physics and Radar Techniques on behalf of the German Space Agency, it scans part of the sky to identify objects and calculate their orbits. “It is undergoing final testing until it is fully operational,” Metz says. “Then, for the first time in Germany, we will be able to independently observe orbital data from objects in orbit.”