The destruction of a single satellite could be catastrophic for our orbital endeavours. Image Credit: ESA
In 2015, the United Nations adopted the 2030 Agenda for Sustainable Development—the Sustainable Development Goals (SDGs)—a universal call to action to protect the planet for future generations and ensure that all people will enjoy peace and prosperity. These 17 goals included the elimination of poverty, hunger, and inequalities, the promotion of education, and the promotion of sustainable development worldwide. With the rapid development in Low Earth Orbit (LEO), there are growing concerns that an 18th SDG should be adopted for space.
This goal calls for the sustainable use of Earth’s orbit by space agencies and commercial industry and the prevention of the accumulation of space junk. This has become a growing problem in recent years thanks to the deployment of satellite mega-constellations and the “commercialization of LEO.” In a recent study led by the University of Plymouth, a team of experts outlined how the lessons learned from marine debris mitigation could be applied to space so that future generations can live in a world where space truly is “for all humanity.”
The destruction of a single satellite could be catastrophic for our orbital endeavours. Image Credit: ESA
In 1978, NASA scientists Donald J. Kessler and Burton G. Cour-Palais proposed a scenario where the density of objects in Low Earth Orbit (LEO) would be high enough that collisions between objects would cause a cascade effect. In short, these collisions would create debris that would result in more collisions, more debris, and so on. This came to be known as the Kessler Syndrome, something astronomers, scientists, and space environmentalists have feared for many decades. In recent years, and with the deployment of more satellites than ever, the warning signs have become undeniable.
Currently, there is an estimated 13,000 metric tons (14,330 US tons) of “space junk” in LEO. With the breakup and another satellite in orbit – the Intelsat 33e satellite – the situation will only get worse. This broadband communications satellite was positioned about 35,000 km (21,750 mi) above the Indian Ocean in a geostationary orbit (GSO). According to initial reports issued on October 20th, the Intelsat 33e satellite experienced a sudden power loss. Hours later, the U.S. Space Forces (USSF) confirmed that the satellite appeared to have broken up into at least 20 pieces.
The ESA's ERS-2 Earth observation satellite was destroyed when it re-entered Earth's atmosphere on February 21st 2004. Heavy parts of satellites like reaction wheels don't don't always burn up in the atmosphere and can pose a hazard. ESA engineers are working on reaction wheels that will break into pieces to reduce the hazard. Image Credit: Fraunhofer FHR
When a satellite reaches the end of its life, it has only two destinations. It can either be maneuvered into a graveyard orbit, a kind of purgatory for satellites, or it plunges to its destruction in Earth’s atmosphere. The ESA’s ERS-2 satellite took the latter option after 30 years in orbit.
A map of space debris orbiting Earth. Credit: European Space Agency
Private and military organizations are tracking some of the 170 million pieces of space junk orbiting the planet, but they’re limited to how small an object they can detect. Only chunks larger than a softball can be tracked with radar or optical systems, and that only accounts for less than 1% of the junk out there.
But a new technique is being developed to resolve space junk to pieces smaller than one millimeter in diameter.
The deployment of the Drag Augmentation Deorbiting System (ADEO) was captured by a camera onboard the ION satellite carrier. Credit: ESA.
The European Space Agency successfully tested a solar-sail-type device to speed up the deorbit time for a used cubesat carrier in Earth orbit. The so-called breaking sail, the Drag Augmentation Deorbiting System (ADEO) was deployed from an ION satellite carrier in late December 2022. Engineers estimate the sail will reduce the time it takes for the carrier to reenter Earth’s atmosphere from 4-5 years to approximately 15 months.
The sail is one of many ideas and efforts to reduce space junk in Earth orbit.
“We want to establish a zero debris policy, which means if you bring a spacecraft into orbit you have to remove it,” said Josef Aschbacher, ESA Director General.
An artist's conception of Starlink in orbit. Credit: SpaceX
SpaceX has drawn plenty of praise and criticism with the creation of Starlink, a constellation that will one-day provide broadband internet access to the entire world. To date, the company has launched over 800 satellites and (as of this summer) is producing them at a rate of about 120 a month. There are even plans to have a constellation of 42,000 satellites in orbit before the decade is out.
However, there have been some problems along the way as well. Aside from the usual concerns about light pollution and Radio Frequency Interference (RFI), there is also the rate of failure these satellites have experienced. Specifically, about 3% of its satellites have proven to be unresponsive and are no longer maneuvering in orbit – which could prove hazardous to other satellites and spacecraft in orbit.
Artist's impression of a satellite exploding. Credit: ESA
On Friday (Jan. 19th), authorities at the Federal Communications Commission (FCC) announced that they had granted permission to cable tv provider DirecTV to begin the process of deorbiting their Spaceway-1 (F1) satellite. This was necessary ever since DirecTV detected a “major anomaly” with the satellite’s batteries which increased the risk of an explosion if its orbit remained unchanged.
An air-to-air left side view of an F-15 Eagle aircraft releasing an anti-satellite (ASAT) missile during a test. Credit: USAF
As long as human beings have been sending satellites into space, they have been contemplating ways to destroy them. In recent years, the technology behind anti-satellite (ASAT) weapons has progressed considerably. What’s more, the ability to launch and destroy them extends beyond the two traditional superpowers (the US and Russia) to include newcomers like India, China, and others.
For this reason, Sandia National Laboratories – a federal research center headquartered in New Mexico – has launched a seven-year campaign to develop autonomous satellite protection systems. Known as the Science and Technology Advancing Resilience for Contested Space (STARCS), this campaign will fund the creation of hardware and software that will allow satellites to defend themselves.
Drag sails can be used to de-orbit old satellites. Image Credit: Purdue University/David Spencer
The growing problem of space debris in LEO (Low-Earth Orbit) is garnering more and more attention. With thousands of satellites in orbit, and thousands more on the way, our appetite for satellites seems boundless. But every satellite has a shelf-life. What do we do with them when they’ve outlived their usefulness and devolve into simple, troublesome space debris?
Artist's impression of all the space junk in Earth orbit. Credit: NASA
This past weekend, a lot of attention was focused on the Tiangong-1 space station. For some time, space agencies and satellite trackers from around the world had been predicting when this station would fall to Earth. And now that it has safely landed in the Pacific Ocean, many people are breathing a sigh of relief. While there was very little chance that any debris would fall to Earth, the mere possibility that some might caused its share of anxiety.
Interestingly enough, concerns about how and when Tiangong-1 would fall to Earth has helped to bring the larger issue of orbital debris and reentry into perspective. According to the SDO, on average, about 100 tonnes of space junk burns up in Earth’s atmosphere every year. Monitoring these reentries and warning the public about possible hazards has become routine work for space debris experts.
This junk takes the form of defunct satellites, uncontrolled spacecraft, the upper stages of spent rockets, and various discarded items (like payload covers). Over time, this debris is slowed down by Earth’s upper atmosphere and then succumbs to Earth’s gravitational pull. Where larger objects are concerned, some pieces survive the fiery reentry process and reach the surface.
Radar images acquired by the Tracking and Imaging Radar system – one of the world’s most capable – operated by Germany’s Fraunhofer FHR research institute. Credit: Fraunhofer FHR
In most cases, this debris falls into the ocean or lands somewhere far away from human settlement. While still in orbit, these objects are tracked by a US military radar network, the ESA’s Space Debris Office, and other agencies and independent satellite trackers. This information is shared in order to ensure that margins of error can be minimized and predicted reentry windows can be kept narrow.
For the SDO team, these efforts are based on data and updates provided by ESA member states and civil authorities they are partnered with, while additional information is provided by telescopes and other detectors operated by institutional and private researchers. One example is the Tracking and Imaging Radar (TIRA) operated by the Fraunhofer Institute for High Frequency Physics and Radar Techniques near Bonn, Germany.
This is a challenging task, and often subject to a measure of imprecision and guesswork. As Holger Krag, the head of ESA’s Space Debris Office, explained:
“With our current knowledge and state-of-the-art technology, we are not able to make very precise predictions. There will always be an uncertainty of a few hours in all predictions – even just days before the reentry, the uncertainty window can be very large. The high speeds of returning satellites mean they can travel thousands of kilometres during that time window, and that makes it very hard to predict a precise location of reentry.”
Tiangong-1 as seen in a a composite of three separate exposures taken on May 25, 2013. Credit and copyright: David Murr.
Of the 100 tonnes that enters our atmosphere every year, the vast majority are small pieces of debris that burn up very quickly – and therefore pose no threat to people or infrastructure. The larger descents, of which there are about 50 per year, sometimes result in debris reaching the surface, but these generally land in the ocean or remote areas. In fact, in the history of spaceflight, no casualties have ever been confirmed by falling space debris.
The ESA also takes part in a joint tracking campaign run by the Inter Agency Space Debris Coordination Committee, which consists of experts from 13 space agencies. In addition to the ESA, this committee includes several European space agencies, NASA, Roscosmos, the Canadian Space Agency, the Japanese Aerospace Exploration Agency, the Indian Space Research Organization, the China National Space Agency, and the State Space Agency of Ukraine.
The purpose of these campaigns is for space agencies to pool their respective tracking information from radar and other sources. In so doing, they are able to analyze and verify each other’s data and improve prediction accuracy for all members. The ESA hosted the 2018 campaign, which followed the reentry of China’s Tiangong-1 space station as it entered Earth’s atmosphere this weekend – the details of which are posted on the ESA’s Rocket Science blog.
“Today, everyone in Europe relies on the US military for space debris orbit data – we lack the radar network and other detectors needed to perform independent tracking and monitoring of objects in space,” said Krag. “This is needed to allow meaningful European participation in the global efforts for space safety.”
While predicting when and where space debris will reenter our atmosphere may not yet be an exact science, it does have one thing going for it – its 100% safety record. And as the Tiangong-1 descent showed, early warning and active tracking ensure that potential threats are recognized well in advance.
In the meantime, be sure to enjoy this video on the Space Debris Office’s reentry monitoring, courtesy of the ESA:
