Tag Archives: space debris

It's getting crowded up there. A plot of space debris around the Earth. (NASA)

Scientists spot space debris in daylight, helping satellites ‘social distance’

It’s really getting crowded up there! The immediate area around Earth is cluttered with space debris, with recent estimates suggesting almost 4,000 man-made satellites in a near-Earth orbit, only one-third of which are currently operational. These non-operational units are subject to leakage, fragmentation and even explosions — further littering the immediate region around our planet. On top of this is a further population of near 20,000 known space debris objects. 

If humanity is going to continue to exploit the space immediately surrounding the Earth measures need to be taken to avoid this space debris. Collisions between this space junk and operating satellites aren’t just costly and damaging, they also create more debris. Now researchers at the University of Bern have made a breakthrough that just might help satellites avoid just collisions. 

The Bern team used the geodesic laser at Optical Ground Station and Geodynamics Observatory Zimmerwald to spot space debris in the daylight. (© Universität Bern / Université de Bern / University of Bern, AIUB)
The Bern team used the geodesic laser at Optical Ground Station and Geodynamics Observatory Zimmerwald to spot space debris in the daylight. (© Universität Bern / Université de Bern / University of Bern, AIUB)

The Bern team is the first in the world to successfully determine the distance from Earth to a piece of space junk in daylight. The researchers performed the feat on June 24th using a geodesic laser fired from Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald. The achievement opens up the possibility of spotting space debris during the day, this means that possible collisions between satellites and space debris can be identified early and mitigation strategies such as evasive manoeuvres can be implemented earlier. 

Being Evasive

Spotting space debris during the day should help prevent events such as the collision that occurred between the operational communications satellite Iridium 33 and the obsolete Cosmos 2251 communications satellite in 2009. Occurring at an altitude of 800 km over Siberia the impact at 11.7 km/s created a cloud of over 2000 pieces of debris — each larger than 10 cm in diameter. Within a matter of months, this cloud of debris had spread across a wide area, and it has been a threat to operational satellites ever since. 

Simulations performed at Lawrence Livermore National Lab on the Testbed Environment for Space Situational Awareness (TESSA) show the collision between Iridium 33 and the Cosmos 2251 communications satellite and the space debris it created. (Lawrence Livermore National Lab)

But one positive did come out of the event, it made both scientists and politicians wake-up to the fact that the problem of space debris can no longer be ignored.

In fact, the risk of collision with space junk in certain orbits around the Earth is so great, that evasive manoeuvres are commonplace. The ESA alone receives thousands of collision warnings for each satellite in its fleet per year! This leads to satellites performing dozens of evasive acts each year. But, it’s vitally important to accurately assess when evasive action is actually needed as they can be costly and time-consuming to perform. 

“The problem of so-called space debris — disused artificial objects in space — took on a new dimension,” says Professor Thomas Schildknecht, head of the Zimmerwald Observatory and deputy director of the Astronomical Institute at the University of Bern. “Unfortunately, the orbits of these disused satellites, launcher upper stages or fragments of collisions and explosions are not known with sufficient accuracy.”

Thus, as well as reducing collision risk, daytime observations of space debris could mean that unnecessary evasive action is avoided. There could be another benefit to early debris detection too. 

Many researchers are currently investigating the possibility of missions to clear space debris. One such example is the work of Antônio Delson Conceição de Jesus and Gabriel Luiz F. Santos, both from the State University of Feira de Santana, Bahia, Brazil, recently published in the journal EPJ Special Topics. The pair modelled the complex rendezvous manoeuvres that would be required to bring a ‘tug vehicle’ into contact with space junk. Better positioning debris clusters could assist these efforts considerably.

Fun with Lasers

Currently, the position of space debris can only be estimated with a precision of around a few hundred metres, but the team from Bern believe that using the satellite laser ranging method they employed to make their daylight measurement, this margin of error can be slashed down to just a few meters, a massive improvement in accuracy. 

“We have been using the technology at the Zimmerwald Observatory for years to measure objects equipped with special laser retroreflector,” Schildknecht says, adding that these measurements were also previously only possible to make at night. “Only a few observatories worldwide have succeeded in determining distances to space debris using special, powerful lasers to date.”

The Zimmerwald Laser and Astrometry Telescope ZIMLAT in Zimmerwald, which is used for distance measurement to space debris objects. (© Universität Bern / Université de Bern / University of Bern, AIUB)
Example of a “string of pearls” of photons reflected by the target debris object in the “sea of sky background photos”. (© Universität Bern / Université de Bern / University of Bern, AIUB)

Despite providing more accurate measurements, geodetic laser systems such as the one at the Zimmerwald observatory employed by the researchers are actually at least one order of magnitude less powerful than specialized space debris lasers. Additionally, detecting individual photons diffusely reflected by space debris amid the sea of daylight photons is no mean feat.

These problems were overcome by the use of highly sensitive scientific CMOS camera with real-time image processing to actively track the space junk, and a real-time digital filter to detect the photons reflected by the object.

“The possibility of observing during the day allows for the number of measures to be multiplied. There is a whole network of stations with geodetic lasers, which could in future help build up a highly precise space debris orbit catalogue,” Schildknecht concludes. “More accurate orbits will be essential in future to avoid collisions and improve safety and sustainability in space.”

Orbital ‘littering’ fee might solve our space junk problem

A computer-generated image representing space debris as could be seen from high Earth orbit. Credit: NASA.

Where humans go, trash isn’t too far behind — and that includes space, too. In fact, space junk is a growing problem that may make it impossible to launch things beyond Earth’s atmosphere if we don’t do something about it. A new study is proposing an innovative solution: charge a fee for every satellite put into orbit.

An orbital space tax

Since we began sending satellites into space in the late 1950s, human activity has been leaving behind trash with every launch. Every major world power has contributed to this growing space junk problem.

NASA is monitoring some of the biggest pieces of debris out there, including approximately 20,000 objects as big or bigger than a baseball and 50,000 objects as big as a marble. Smaller pieces of debris, however, are virtually undetectable right now, but NASA estimates there are millions of objects that are 50 microns to 1 millimeter in diameter.

That might not seem like such a big deal but consider that these tiny pieces of debris travel at 17,500 miles per hour. At these velocities, even an object with a tiny mass can exert a powerful kinetic energy capable of significant damage upon impact.

Below you can see what a tiny speck of space debris did to the super-reinforced glass of the International Space Station’s Cupola — if you had any doubt this isn’t serious business. Now, imagine the kind of damage a larger object can do. A person on Earth even got hit by a piece of space debris in 1997.

This isn’t a crack on a car’s windshield, but 7-mm chip in diameter in one of the windows of the ISS’ Cupola — the dreamy vantage point which astronauts use to take amazing pictures. It was caused by “possibly a paint flake or small metal fragment no bigger than a few thousandths of a millimetre across,” ESA wrote. Credit: ESA.

Most proposals for decluttering Earth’s low-orbit have focused on technology, such as giant collecting nets, janitorial satellites with harpoons, even Earth-based giant lasers.

The Tragedy of the Commons (in space)

Matthew Burgess is not a space engineer but rather an economist — yet his take on cleaning up Earth’s low-orbit may be more impactful than any fancy technology.

In a new study, Burgess, who is an economist at the University of Colorado at Boulder, and colleagues suggest charging satellite operators and other agents involved in launching stuff into orbit an annual fee.

The reasoning behind this idea is that space is a common resource and, despite its name, it is not limitless — not in the amount of junk we can safely dispose of in orbit, at least. This is similar to how we (should) tax carbon in order to account for the negative externalities of fossil fuels in the environment.

“Space is a common resource, but companies aren’t accounting for the cost their satellites impose on other operators when they decide whether or not to launch,” Burgess, who is also an assistant professor in Environmental Studies and an affiliated faculty member in Economics at the University of Colorado Boulder, said in a press release. “We need a policy that lets satellite operators directly factor in the costs their launches impose on other operators.”

According to the study’s results, an annual fee of $235,000 per satellite would quadruple the value of the satellite industry by 2040.

The tax on orbital use for satellites would be calculated to reflect the cost to the industry of putting another satellite into orbit. This includes the project costs of additional collision risk and space debris production.

“To us as environmental economists, the situation in orbit very much resembles other common resources we’re familiar with (e.g. fisheries, traffic, atmospheric carbon). With these resources, overexploitation typically occurred (or continues to occur) until incentive-based policies have been put into place. When we looked at the policy conversation, we saw a lot of discussion about technical and managerial fixes — things like debris removal nets or harpoons, and discussions of keep-out zones or deorbit guidelines. We saw very little discussion considering what an incentive-based solution would look like. Given our backgrounds, we wanted to contribute that piece to the conversation,” Akhil Rao, assistant professor of economics at Middlebury College and the paper’s lead author, told ZME Science in an e-mail.

Such fees would increase over time in order to account for the rising value of cleaner orbits — scarcity begets value, after all.

The model used by the researchers suggests that an optimal fee would increase at a rate of 14% per year, reaching $235,000 per satellite per year by 2040.

“Economic data was one of the big challenges. There’s a lot of physical data on the objects in orbit — where the object is, when it was launched, who launched it, when it’s expected to decay, etc. — but there’s a lot less data at the per-object level on how much revenue individual satellites produce and how much they individually cost. We used highly aggregated sector-level economic data as a result,” Rao said.

Burgess and Rao compared the forecasted impact of orbital-use fees under various scenarios to business as usual (no fees to operate in space) and technological fixes like janitorial satellites and lasers.

The results suggest that an orbital fee introduces an economic incentive that forces operators to think twice before they add another satellite in orbit unless it really adds value.

Perhaps counter-intuitively, these kinds of fees might actually help the satellite industry grow from $600 billion under a business-as-usual scenario to around $3 trillion. According to the researchers, the massive uptake in valuation can be pinned to reduced collisions and collision-related costs.

However, like other forms of taxes, an orbital-use fee would only work if all countries and agents launching satellites would participate in the program. There are now nearly a dozen countries that perform satellite launches and about 30 that own satellites but rely on others to launch them.

But if one country refuses to participate, the whole scheme is dismantled, similar to how a tax haven attracts corporations, leaving their home countries with no revenue.

“There are many ways the orbital-use fees could be collected and used. In the paper, we outline one possible model based on the Vessel Day Scheme (an agreement which regulates use of a tuna fishery between a group of nations in the Pacific, the Parties to the Nauru Agreement). In this model, the fees would be internationally harmonized and nations with satellite operators would collect fees from the operators subject to their laws. The revenues could then be used as the collecting nation sees fit,” Rao said.

“So for example, if company A was launching from the US, the US could collect the internationally-harmonized orbital-use fees from company A and spend it domestically, invest it in debris cleanup R&D, refund it to US taxpayers, or find some other use for it. The nice thing about these kinds of fees (“Pigouvian taxes”) is that their effectiveness doesn’t hinge on what the revenue is used for,” he added.

As such, there are many challenges to this approach but this doesn’t make it any less appealing. Frankly, we need to hit space junk with everything we’ve got; otherwise, we might risk never being able to safely leave this planet and reach our full potential as a space-faring species.

“In other sectors, addressing the Tragedy of the Commons has often been a game of catch-up with substantial social costs. But the relatively young space industry can avoid these costs before they escalate,” Burgess said.

“Orbit use might seem like an “out there” topic, but satellites are actually very integrated in our daily lives. GPS, remote sensing, and satellite telecommunications power a number of consumer products, and that’s before we talk about government uses, responses to natural disasters, and new innovations that are just emerging. We all have a vested interest in making sure the environment where these valuable assets live stays usable, now and moving forward,” Rao wrote in an e-mail.

The findings appeared in the Proceedings of the National Academy of Sciences.

ISS astronauts could use laser cannon to blast off hazardous space junk

Astronauts onboard the ISS may soon get a new “toy” – a space laser cannon to blast off space debris that might threaten the space station. Even a tiny scratch or dent could cause massive problems, and with us putting more and more stuff in space, the risk of damage constantly increases too.

There are hundreds of thousands of pieces of space debris in orbit. Image via Wikipedia.

“Our proposal is radically different from the more conventional approach that is ground based, and we believe it is a more manageable approach that will be accurate, fast, and cheap. We may finally have a way to stop the headache of rapidly growing space debris that endangers space activities. We believe that this dedicated system could remove most of the centimeter-sized debris within five years of operation,” said project Toshikazu Ebisuzaki.

We’re dealing with air pollution, water pollution, ground pollution… but a lesser known issue is space pollution. Even though we’ve only started exploring outer space for decades, we’ve put out a staggering amount of stuff in orbit. As of 2009 about 19,000 pieces of debris larger than 5 cm (2 in) are tracked, with 300,000 pieces larger than 1 cm estimated to exist. Most junk sources are shuttle components, lost equipment, boosters or anti-satellite weapons put up by the US and Soviet Union during the 1960s and 1970s. Although most of these pieces orbit at a different distance from Earth than the ISS, many of them still have the potential to pose threats.

Up until now, the ISS had no other option than to try to change its trajectory to avoid space junk, but now, Japanese researchers believe they have found the solution to that problem. They developed a laser system that can vaporize bits of debris way before they can harm the ISS. The entire system was actually created to monitor the atmosphere for ultraviolet emissions from cosmic rays, but it could double as a precision space junk tracking system. In other words, you have the tracking system, and all you need is a space laser – an instrument that focuses intense beams of energy onto very specific targets, vaporizing them, or if the junk is hard metal, changing their trajectory so they aren’t dangerous anymore.

“We realized,” says Toshikazu Ebisuzaki, who led the effort, “that we could put it to another use. During twilight, thanks to EUSO’s wide field of view and powerful optics, we could adapt it to the new mission of detecting high-velocity debris in orbit near the ISS.”

The laser could zap targets from 60 miles away (100 km), and it could be installed as soon as 2017. Meanwhile the European Space Agency is testing fishing-style nets to catch larger pieces of space junk which can’t be handled otherwise.

“We may finally have a way to stop the headache of rapidly growing space debris that endangers space activities. We believe that this dedicated system could remove most of the centimeter-sized debris within five years of operation,” says Ebisuzaki.



Gecko sex in space, and why this is good for science

space-geckoOn July 19, the Russian space agency, Roscosmos, sent five geckos in space in order to study their sex lives under micro-gravity conditions. Five days later, though, contact with the gecko love satellite was interrupted stirring a bit of panic. Luckily, technicians managed to restore contact with the craft, according to the Russian space agency and the experiment is continuing as planned on its two-month mission.

The four females and one male will be followed by researchers as they mate, lay eggs and hatch younglings to see how micro-gravity affects fertility. Specifically, the Gecko-F4 mission aims:

  • Create the conditions for sexual activity, copulation and reproduction of geckos in orbit
  • Film the geckos’ sex acts and potential egg-laying and maximise the likelihood that any eggs survive
  • Detect possible structural and metabolic changes in the animals, as well as any eggs and foetuses

As if enough eyes weren’t enough, the geckos will be kept company by Drosophila fruit flies, as well as mushrooms, plant seeds and various microorganisms that are also being studied. In the chamber next to this tiny ecosystem lies a furnace were melting and solidification of metal alloys in space will be studied. After the two month study is over, Roscosmos plans on running addition experiments before its eventual Earth uncontrolled re-entry four months later.

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This, of course, assuming contact isn’t lost again. The Russian space agency was quoted saying the most probable cause of the initial communications failure may have been space debris. The satellite that carries the experiment is flying in low-orbit at around 357 miles away from the Earth’s surface. Here, the gecko ferrying satellite shares orbit with the International Space Station and around 20,000 space debris. We’ve written extensively in the past on the dangers space debris pose to space missions and how we might possibly tackle them.

If mankind is ever to become an interstellar race, some humans will most certainly spend their lifetimes in space. Trips might last for whole generations in fact. It becomes thus important to understand what kind of effects zero gravity has on mating and fertility. If, for instance, across many generations maybe, it’s found that humans can’t reproduce in space this would spell a disaster. Geckos are part of a bigger plan meant to probe this very important question. They’re not the first beings to mate in space, though. This honor belongs to a cockroach!

In 2007, Roscosmos sent a crew of geckos, newts, snails, Mongolian gerbils and cockroaches to space and landed the experiment back on Earth 12 days later. The cockroaches were the first to mate in space, and researchers were able to identify which of them was the first to conceive in space – a cockroach named Nadezhda, which means “hope” in Russian. Interestingly enough, the roaches “run faster than ordinary cockroaches, and are much more energetic and resilient”, according to Russian researchers.


Ballistic test on Kevlar shows what could happen to the ISS from space debris impacts

We’ve mentioned on numerous occasions the growing problem of space debris and voiced our concerns that, if left unchecked, the thousands of metal junk fragments currently out there could seriously affect space missions and even threaten lives. In Earth’s orbit, even a tiny metal fragment could potentially wreak havoc upon impact with a spacecraft or satellite because of the extremely high kinetic energies involved. The International Space Station regularly comes in contact with such fragments. Sometimes, astronauts aboard need to perform a space walk in order to repair or replace a damaged solar cell or some other device. A ballistic test that demonstrates the kind of fire power the ISS is thrown against each day was recently released by the ESA.

Beware of space junk


This burned and torn through piece of kevlar shiled is the result of the test which used the Fraunhofer Institute’s Extra Large Light Gas Gun – a huge air cannon, basically – to shoot a 7.5mm (0.3in) aluminium bullet. The kevlar shield is the same as the one used to layer the manned modules of the International Space Station and protect the crew, while the firing bullet mimics a metal junk fragment traveling at 7 kilometers per second or 15,600 mph.

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I know, this looks very scary but believe it or not, the Kevlar did its job well since the aluminium casing it shielded remained intact. Actually, apart from a small dent and the scorching remains, the casing remained otherwise unharmed. The test proves that Kevlar is truly one tough mother, but it also gives to show that space debris is no funny business. Last year, the International Space Station went on full alert and the astronauts stationed there were forced to reach for their escape pods until further notice after mission control spotted a risky space debris trajectory that could have made impact with the space station. Luckily, the impact was averted.


Those of you who’ve watched the movie Gravity must be thinking if the scene where the space debris shooting the ISS are accurate. Despite the movie’s numerous short comings in terms of scientific accuracy, the very frightening scenes where the space debris collide with the station causing a monstrous chain of events are very much accurate.

What can the world do about space debris? Well, there are some ideas thrown about, ranging from a janitor satellite to a full blown giant ground laser that zaps the debris. If these work it remains to be seen, but for now the best thing the world’s space agencies and governments can do is to avoid creating more debris. In 1997, China intentionally blew up one of its satellites to demonstrate a weapon project. As a result more than 3,000 pieces of debris were scattered in orbit. Seriously, people should stop doing stupid stuff like this!

The results of the shielding test can be read in depth at ESA.

Thousands of pieces of "space junk" orbit our planet. (c) ESA

CO2 emissions might lead to more space junk hazard

Ever increasing CO2 levels in the atmosphere are not only hazardous to life on the planet’s surface, but also to human operations in space. A new study has found that an increase in carbon dioxide in the atmosphere upper levels could push made-made objects orbiting the planet further away from their trajectories, resulting in a faster accumulation of space junk and an increase risk of collusion with valuable satellites.

Thousands of pieces of "space junk" orbit our planet. (c) ESA

Thousands of pieces of “space junk” orbit our planet. (c) ESA

Carbon dioxide warms the lower atmosphere of Earth, however it works as a coolant at higher altitudes, where it’s not dense enough to recapture the heat that it emits. Thus, in its upper most layers the same build-up causes a cooling effect. So, the thermosphere, the upper-most layer of the atmosphere, begins to contract and in the process reduces the drag effect on satellites, the International Space Station, as well as any other object orbiting this region.

“The observed CO2 increase is expected to gradually result in a cooler, more contracted upper atmosphere and a consequent reduction in the atmospheric drag experienced by satellites,” said a statement from the Naval Research Laboratory, which took part in the study.

This translates in a longer life span for space junk, as more such objects will stay farther out for longer instead of burning up in the lower layers of the atmosphere, closer to Earth. Space debris already consist a very serious issue for operations in space, as hundreds of thousands of space junk debris travel at huge speeds in sub-orbital space, posing a high risk to satellites and manned missions at the International Space Station. A number of solutions have been proposed in order to deal with the issue, however deployment is still far away from becoming reality.

“Consequently, space junk will accumulate at a faster rate and we will see more collisions between space objects as a result,” the report stated. “We will also see many more ‘near-misses’ and these have an important effect on spacecraft operators.”

The scientists estimate that the concentration of carbon near 100 km altitude is increasing at a rate of 23.5 ± 6.3 parts per million per decade – about 10 ppm/decade faster than predicted by upper atmospheric model simulations. On the bright side, the scientists involved in the Atmospheric Chemistry Experiment (ACE), a scientific satellite mission funded primarily by the Canadian Space Agency, claim that the thermosphere contraction means that satellites won’t have to commence re-orbiting operations so often, saving fuel in the process.

Findings were reported in the journal Nature Geoscience.

Artist impression of the New Horizons spacecraft set to fly by the Pluto system in July 2015. (c) JHUAPL/SWRI

Pluto’s moons pose grave threat to NASA’s New Horizons spacecraft

Artist impression of the New Horizons spacecraft set to fly by the Pluto system in July 2015. (c) JHUAPL/SWRI

Artist impression of the New Horizons spacecraft set to fly by the Pluto system in July 2015. (c) JHUAPL/SWRI

NASA’s New Horizons spacecraft is currently seven years into its nine-and-a-half-year journey across the Solar System to explore Pluto. Since its launch in 2006, however, astronomers have discovered two more moons orbiting the dwarf-planet, which now pose a grave threat to the spacecraft’s initial navigation course because of space debris orbiting them.

“We’ve found more and more moons orbiting near Pluto – the count is now up to five,” said Dr Alan Stern, chief scientist on the New Horizons mission.

“And we’ve come to appreciate that those moons, as well as those not yet discovered, act as debris generators populating the Pluto system with shards from collisions between those moons and small Kuiper Belt objects.”

Scientists are currently devising alternative routes which will stir the spacecraft out of harms way, while at the same time preserving the mission’s integrity.

“We want people to understand just how interesting and how nail-biting New Horizons’ mission might be,” said Stern. “This is part of the excitement of first-time exploration, of going to a new frontier.”

Space debris have always been a grave issue for NASA spacecrafts exploring deep in the solar system – currently New Horizons is  24 times farther away from the sun than Earth is, only  1,000 days away and 730 million miles (1,180 million kilometers) from closest approach to Pluto. Since it’s travelling at a whooping fast velocity –  more than 30,000 miles per hour – a collision with a single pebble, or even a millimeter-sized grain, could ruin the spacecraft beyond recovery. All these years, billions of dollars, and heartfelt passions could all be in vain, if a disaster isn’t averted.

With this in mind, NASA scientists are had at work tinkering solutions. The primary objective is currently identifying space debris in Pluto’s orbit using computer simulations, ground-based telescopes and the Hubble Space Telescope. Meanwhile, the team is also plotting alternative, more distant courses through the Pluto system that would preserve most of the science mission.

“We’re worried that Pluto and its system of moons, the object of our scientific affection, may actually be a bit of a black widow,” Stern said. “We’ve come to appreciate that those moons, as well as those not yet discovered, act as debris generators populating the Pluto system with shards from collisions between those moons and small Kuiper Belt objects.”

An interesting safety precaution NASA engineers are currently considering is pointing New Horizons’ antenna dish forward, “to act as a meteorite shield to protect the spacecraft from impacts,” Stern said. “This technique is not new — the Cassini probe used that when crossing Saturn’s ring plane as well.”

The latest the research team can alter the spacecraft’s trajectory is about 10 days before it gets to Pluto. That gives NASA scientists a few years to plot the best course for New Horizons.

“After that, there’s not enough fuel to make a change,” Stern explained. “We don’t often get into situations in spaceflight where we have to make last-minute decisions. We’re going to learn as much as possible before our final approach in 2015.”

Graph showing space debris inflation from the past few decades. In 2007, China destroyed one of its satellites with a missile creating 3,000 trackable objects and 150,000 debris particles. In 2009 a Russian and American satellite collided resulting in tonnes of debris. (c) NASA

ISS crew took to their escape pods this weekend after space debris collision alert

This Friday, ground mission control ordered the current stationed astronaut crew at the International Space Station to head for the escape capsules as a safety precaution in light of a threatening space junk flyby. This is the third time in 12 years an ISS crew had to take this extreme measure.

Graph showing space debris inflation from the past few decades. In  2007, China destroyed one of its satellites with a missile creating 3,000 trackable objects and 150,000 debris particles. In 2009 a Russian and American satellite collided resulting in tonnes of debris. (c) NASA

Graph showing space debris inflation from the past few decades. In 2007, China destroyed one of its satellites with a missile creating 3,000 trackable objects and 150,000 debris particles. In 2009 a Russian and American satellite collided resulting in tonnes of debris. (c) NASA

The space debris in question was barely detected on Friday, offering little advance warning such that the station might be moved, as such the crew, three Russians, two Americans and one Dutch astronaut, were advised to man the two Soyuz escape capsules in case the station was hit. According to NASA, however, the space junk’s trajectory was well beyond that of the space station, posing little threat, but made for an excellent exercise opportunity. Russia’s space agency said the debris had passed the station at a distance of 23km (14 miles) and on Saturday 0238 GMT, the astronauts were given the green light to return to the main space station modules.

“Everything went by the book and as expected, the small piece of cosmos satellite debris passed the international space station without incident.”

“The cosmonauts have returned to performing their previously assigned work,” an official told Interfax news agency.

A similar incident occurred just last June, however the situation was a lot more stressful, compared to the present one, which simply made for a convenient safety exercise. Back then, a piece of space debris flew by the ISS at a mere 335m distance – a red alert was issued then.

NASA currently keeps track of around 22,000 space objects orbiting Earth, but there are some million other space debris which are either too small to track or have yet to be tracked by the agency. These tiny space objects travel at a few kilometers per second, velocities ten times higher than that of bullet, and if eventually one such object were to hit the ISS, it might cause severe damage to the station itself or its instruments. An international standard for handling space junk is currently being discussed to keep the current rate of increase in debris to a minimum, while clean-up solutions, like a giant laser or space janitor satellite, are discussed for immediate deployment.