Michael Byers holds the Canada Research Chair in Global Politics and International Law. Aaron Boley holds the Canada Research Chair in Planetary Astronomy. They both teach at the University of British Columbia, where they co-direct the Outer Space Institute. The Salt Spring Recommendations on Space Debris are available here.
It must have seemed like a good idea at the time. Between 1961 and 1963, the United States military launched 480 million copper needles into orbit, creating an artificial ring around Earth. The ring, intended to relay radio signals, became obsolete before it was complete, with the launch of the first telecommunication satellites in 1962. Although most of the individual needles have re-entered the atmosphere, driven by the effects of solar radiation, clumps of them remain in orbit today, contributing to the serious and growing problem of space debris.
U.S. entrepreneur Elon Musk may now be embarking on a similar folly. His rocket company, SpaceX, has already launched the first 240 of a planned 12,000 Starlink communications satellites, and is proposing to eventually send up 30,000 more. Since there are 5,500 satellites currently in orbit, only half of which are active, SpaceX will soon become the largest satellite operator of all.
Starlink will revolutionize global communications, bringing connectivity to remote regions and assisting search-and-rescue and disaster relief. But SpaceX is moving so quickly – launching 60 satellites every two to four weeks – that it is proving impossible for national regulators and international organizations to keep up.
Humanity has discovered many uses for space-based systems since Sputnik, the first artificial satellite, was blasted into orbit in 1957.
Satellites are part of our daily lives, from the GPS in our mobile phones to the Earth imaging satellites used by farmers to detect moisture levels and insect infestations as they produce our food. Modern militaries rely heavily on satellites for communications, surveillance and high-precision targeting, as well as the operation of armed drones and fighter jets. If Canada buys F-35 fighter jets, it will need space-based broadband everywhere they fly, including in the Arctic.
The number of satellites – and our dependency on them – will only increase because of the miniaturization of technologies and the development of reusable rockets. Satellites the size of a shoebox can provide the same services today as satellites the size of a school bus did just two decades ago. This enables ride-sharing: placing multiple satellites on a single rocket and thus reducing launch costs. SpaceX launches its Starlink satellites flat-packed on top of a Falcon 9 rocket. The first stage of the two-stage rocket then returns to the Earth and lands on four legs, ready to be used again.
However, all these satellites are threatened by their own increasing numbers as well as a rapid accumulation of space debris, such as leftover rocket stages, defunct satellites and fragments from in-orbit breakups and collisions.
As a result, there is a growing risk that this proliferation of satellites will generate a cascade of runaway space debris that could render key parts of Earth orbit too dangerous for satellites to operate – at least without extensive risk and cost. Ultimately, debris-filled orbits could endanger all types of human space flight.
These days, we are keenly aware of the impact pollution has had on our environment – our lakes and oceans, tundras, deserts and atmosphere. Although it’s a different kind of pollution, we should also pay more attention to what we’re doing higher up, in that portion of outer space surrounding our planet. It, too, will have a profound effect on our future.
Understanding space debris
Objects in orbit are not all travelling in the same direction. This creates the risk of collisions at relative velocities of up to 15 kilometres a second (54,000 km/h). The Space Surveillance Network is tracking more than 20,000 objects larger than 10 centimetres across, which enables some potential collisions to be identified in advance.
Operated by the U.S. military, the network shares this information widely, including with China, Russia and dozens of commercial satellite operators. Sometimes, advance warning of a collision can provide time for an endangered satellite to be moved out of the way using thrusters. The International Space Station has engaged in evasive action on at least 20 occasions since 1998.
The risk of collisions is exacerbated because some orbits are more desirable than others.
Just like cars in Canada are concentrated in cities rather than spread out evenly across the country’s roads, satellites in orbit are concentrated in thin “orbital shells.” Geostationary Orbit, located 36,000 kilometres above the equator, is the optimal location for radio and TV broadcasting because satellites placed there match the rotation of the Earth, enabling ground-based dishes to be fixed in place.
Medium Earth Orbit is home to global positioning satellites, while Low Earth Orbit is perfect for Earth imaging satellites – because of the low altitudes as well as the availability of “sun-synchronous” orbits that allow a spacecraft to pass over the same location on Earth at the same local time every day. Low Earth Orbit will also now be home to “mega-constellations” of communications satellites such as Starlink. These constellations will provide global coverage with low “latency” – the small delays in transmission that result from the time it takes signals to travel between satellites and the Earth’s surface.
When collisions happen, they can create large amounts of debris that then threaten other satellites. In 2009, a commercial communications satellite collided with a derelict Russian satellite. The collision created more than 2,000 pieces of trackable debris, the majority of which remain in orbit today.
The 2009 collision will also have created hundreds of thousands of smaller fragments, any of which could potentially disable or destroy a satellite. In 2013, Canadian astronaut Chris Hadfield noticed a punctured solar panel on the International Space Station. He tweeted a picture along with the comment: “Bullet hole … Glad it missed the hull.”
Last month, two derelict spacecraft – a NASA space telescope and a U.S. military satellite – nearly collided at a relative velocity of 15 km/second. At that speed, a hockey puck (170 grams) would transfer as much kinetic energy as four to five kilograms of TNT, causing both objects to explode into pieces. Now consider this: The telescope weighed 954 kilograms and the military satellite 85 kilograms.
Since there are thousands of derelict satellites and rocket stages in orbit, near-misses occur on an almost weekly basis.
Worse yet, whenever a collision occurs, the resulting increase in surface area of the debris magnifies the risk of further collisions.
The phenomenon of runaway space debris is referred to as the Kessler syndrome, after one of the NASA scientists who first identified it in 1978. The syndrome is depicted in the 2013 film Gravity – sped up to accommodate the time constraints of a Hollywood plot.
Runaway space debris threatens to turn Low Earth Orbit into a “tragedy of the commons,” whereby a resource that is open to everyone is destroyed through overuse.
Mega-constellations and aggrieved astronomers
SpaceX is not the only company building a global communications network in Low Earth Orbit. OneWeb has already launched its first satellites, with funding from Japan’s SoftBank. Amazon founder Jeff Bezos, the world’s richest person, is planning a mega-constellation that will be operated by his company.
Most of these satellites will be located within thin shells in Low Earth Orbit, greatly increasing the collision risk. Already, last September, the European Space Agency was forced to move a scientific Earth imaging satellite to avoid a collision with an experimental SpaceX satellite, after a failed attempt to contact the company by e-mail. Following the near-miss, the agency has been advocating the development of automated collision avoidance systems.
“Right of way” rules are also required to avoid games of “chicken.” Satellite operators have an interest in avoiding collisions, but moving a satellite consumes precious thruster fuel and can lead to service interruptions.
SpaceX’s mega-constellation has attracted public attention thanks to loud protests from astronomers. Light pollution from the first 240 Starlink satellites is already interfering with optical telescopes, while radio telescopes could suffer if signals from a constellation encroached on portions of the radio spectrum that are internationally protected for astronomy. Then there are “occultations,” which occur when satellites pass in front of stars and cause variations in brightness that could interfere with future astronomical measurements. Worse yet, all these negative effects of satellites on astronomy could delay the identification of an asteroid headed toward Earth and thus the time available to mount a deflection mission.
Some mitigation steps are possible – for instance, painting satellites matte black. But much of the light pollution comes from the solar panels, so the overall effect may not be significantly reduced. Painting a satellite black would also cause it to absorb more solar energy, adding thermal stress and potentially reducing its longevity. And near-infrared telescopes could be affected if satellites become hotter.
Mr. Musk responded to the astronomers by tweeting that telescopes should be moved to space anyway, above the distorting effects of the atmosphere. He was right about the importance of space-based astronomy and the potential for it to grow. But some telescopes and telescopic arrays are far too large to be moved into space, including a number of new and very expensive observatories being built in Chile and Hawaii right now. And what about the millions of astronomers, ranging from hard-core enthusiasts to parents who, by pointing the constellations out to their children, are engaging in one of humankind’s oldest traditions?
At a minimum, we believe the principle of “polluter pays” should apply. If Mr. Musk creates a situation where more telescopes have to be placed into orbit, SpaceX should launch those telescopes without charge.
Governing Earth orbit
Everything about space is hard, but it should still be possible to regulate satellites in ways that reduce the risks. The sky over Toronto is crowded, but pilots, air traffic controllers and advanced technologies make collisions extremely rare.
There are no international rules specifically regulating access to orbit or how satellites are designed and operated. All there is are two generally applicable provisions in the 1967 Outer Space Treaty. The first provides that space “shall be free for exploration and use by all states,” while the second requires that governments undertake “appropriate international consultations” before doing anything that could negatively interfere with the freedom of exploration and use enjoyed by others.
At the United Nations, the committee on the peaceful uses of outer space has adopted more specific non-binding guidelines. One guideline recommends the avoidance of “harmful activities that generate long-lived debris,” while another recommends that satellites be deorbited at the end of their operational lives.
An Inter-Agency Space Debris Coordination Committee, made up of representatives from 13 national space agencies, has recommended that this deorbiting be concluded within 25 years of the end of a satellite’s operational life. This recommendation has been widely accepted, perhaps because 25 years is quite generous. Indeed, 25 years is clearly excessive in the context of mega-constellations and efforts are now under way to negotiate a shorter time frame, either as a guideline or ideally a treaty.
Some national governments have acted unilaterally to make these recommendations mandatory. China and Russia, for instance, have made the UN guidelines binding on all their space operators under domestic law. Insurance companies are also in a position to help – by charging higher premiums for satellites lacking rapid end-of-life deorbiting capabilities.
Last but not least, astronomers and lawyers are exploring whether improved tracking of space objects could enable litigation in domestic courts for collisions caused by negligence, in the same way that climate change litigation is being driven by scientific advances in establishing “causation” between individual fossil fuel companies and damage from sea level rise and extreme weather events.
The testing of anti-satellite weapons has contributed greatly to space debris. Such weapons exist because destroying satellites could disable an opponent’s communications, situational awareness and targeting. Satellites, moreover, are fragile, difficult to defend and travel on predictable courses – all of which makes them vulnerable to ground-based missiles as well as “killer” satellites designed to be steered into high-speed collisions.
In 2007, China used a missile to destroy a defunct weather satellite. The strike was the worst debris-generating event on record, creating 2,087 pieces more than 10 centimetres across and many more pieces smaller than that. The U.S. Air Force estimated that more than 700 satellites were at risk of being struck by debris from the Chinese test, and indeed, a Russian satellite was disabled by one of the pieces in 2013.
After the Chinese test revealed that just one anti-satellite weapon can create tens of thousands of pieces of debris, subsequent tests have been conducted in ways that seek to prevent this from happening. In 2008, the United States used a missile-defence interceptor to destroy a malfunctioning satellite that was about to re-enter the atmosphere with thousands of litres of toxic thruster fuel on board. The interceptor struck the satellite at such a low altitude that no long-lasting debris was created.
The U.S., Russia and China have also focused on developing anti-satellite weapons that operate without high-speed collisions, such as spacecraft that can capture satellites or simply nudge them off course. Other methods include uplink and downlink jamming a satellite’s signals with radio interference, spoofing the satellite by broadcasting fake signals toward it, or blinding it with a laser.
In 2006, China directed a laser at a U.S. satellite, blinding it for a few minutes. In 2018, Russia jammed GPS signals to interfere with a NATO exercise in the Norwegian Sea. Cyberwarfare techniques could also be directed against satellites to disrupt their transmissions, corrupt data or even take control over them.
Meanwhile, other space-faring states are trying to catch up. Last March, India tested a missile against a satellite it had launched for that purpose. It designed the impact to occur just 283 kilometres above the Earth and assured other countries that no long-lasting debris would be created. Yet almost a year later, at least 19 trackable pieces remain in orbit, along with an unknown but likely much greater number of smaller pieces.
NASA administrator James Bridenstine was highly critical of the Indian test. Of the 400 pieces of debris initially identified by his agency, 24 had orbits that crossed the altitude of the International Space Station. Describing this as “a terrible, terrible thing,” Mr. Bridenstine said, “It is not acceptable for us to allow people to create debris fields that put at risk our people.”
NASA’s concerns are shared by the U.S. military. In 2015, General John Hyten of the U.S. Air Force Space Command described anti-satellite weapons that create debris as “horrible for the world. … Whatever you do, don’t create debris.” As mentioned, the U.S. military operates the Space Situational Network that warns of possible collisions.
In 2018, U.S. President Donald Trump signed a directive ordering all U.S. departments and agencies to work with other countries to prevent space debris. The directive ensured continuing U.S. leadership on this issue during a time of increasing unilateralism and isolation.
As for India, two things can be said in its defence. It struck the satellite at a low altitude because it sought to avoid the creation of long-lasting space debris. The test was not necessarily a signal of hostile intent, but rather a demonstration to China – its larger regional rival – that any attacks on Indian satellites could be responded to in kind. These are small comforts, however, since it is now likely only a question of time before Pakistan tries to demonstrate that it, too, can shoot down a satellite.
Where to from here?
Finding solutions to the problem of space debris will not be easy. Inspired by Silicon Valley, companies such as SpaceX are moving fast and breaking things. National governments, burdened with full agendas, ingrained practices and old rules, are slow to grapple with new challenges.
Yet there are reasons for hope. Modern militaries are gravely concerned about the risk of runaway space debris and have the financial and political clout to drive the search for solutions and then turn them into action. States have previously come together to prevent tragedies of the commons when, as is the case here, alternative technologies are available. The Montreal Protocol that banned chlorofluorocarbons to save the ozone layer is but one example.
Last month, we played host to a workshop titled Space Debris and National Security on Salt Spring Island, B.C., with funding from the Canadian Department of National Defence. Thirty international experts from universities, governments and industry drew up 20 recommendations.
Some of the recommendations can be implemented by countries unilaterally – for instance, the avoidance of anti-satellite weapons tests that generate debris. Others, such as the negotiation of a treaty prohibiting such tests, will require widespread co-operation.
Some of the recommendations are directed at companies such as SpaceX – for instance, that they reduce failure rates by including backup systems in their satellites, along with technologies that allow for rapid end-of-life deorbiting.
The most important recommendation, however, is a general one – that space be developed in a sustainable manner. Humanity has been polluting Earth’s orbit for six decades. It is time, now, to clean up our act.
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