Planning for the inevitable: a guide to disasters in low Earth orbit
In the opening credits of the 1998 blockbuster, Armageddon, an asteroid strikes Earth, causing fire to engulf the planet. “It happened before,” Charlton Heston warns, “It will happen again. It’s just a question of when.”
Unlike 99% of this movie, Heston isn’t exactly wrong. Scientists believe an extinction-causing asteroid hit Earth almost 66 million years ago. They also believe that another deadly asteroid strike is possible. That’s why many scientists, including my co-founder at LeoLabs (and former NASA astronaut) Ed Lu, study asteroids and develop protection measures. We got a glimpse into this work during NASA’s Double Asteroid Redirection Test (DART) earlier this year. Lucky for us, it was a success.
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Heston’s iconic phrase is not just applicable to asteroid strikes. Throughout history, the inevitability of disasters, from recurring events like hurricanes to rare events like pandemics, has led us to prepare for them as best we can. I believe disasters in low Earth orbit (LEO) should be approached no differently.
The inevitability of a disaster in low Earth orbit
The traffic in LEO is growing rapidly, particularly in lower altitudes ideal for large constellations, CubeSats, and crewed spaceflight. The sun-synchronous orbits are also a popular destination for earth imaging missions in LEO.
Across LEO, thousands of pieces of space debris reside in clouds of fragments and clusters of massive derelicts. This grim reality means that collisions are not a question of if but when. To prepare for this inevitability, we must understand what the dangers are and the threat level. That’s my job. My primary concern is protecting operational objects in space, like satellite constellations, which have become critical to daily life. That’s why my team and I work tirelessly to not only monitor the risks in space but to also characterize them.
Every industry has its bad days, including space. Rather than ignore them, the best response is to anticipate and prepare for them. Towards this effort, I’ll discuss four types of potential disasters in LEO below, these include:
- Operational payload on catalogued object collision
- Dead object on dead object collision
- Object colliding with lethal, small debris
- Operational payload attacked by an adversary
Operational payload on catalogued object collision
An operational satellite colliding with a catalogued object, such as another operational satellite or a trackable, non-operational object, is possible. Thankfully, this scenario is the easiest to avoid if the operational satellite is maneuverable. Satellite owner-operators can be notified of an upcoming conjunction in the days leading up to the event and act on that information. If the secondary object is non-maneuverable or non-operational, the owner-operator can decide how they want to maneuver. However, if the secondary object is another maneuverable satellite, the two owner-operators should coordinate.
This disaster scenario has occurred in the past when space situational awareness information was not as available as it is today. In 2009, an active Iridium satellite collided with an inactive Russian communications satellite. As a result, The U.S. military’s Joint Space Operations Center re-added the Iridium constellation to its daily conjunction assessment procedures and eventually expanded to cover all active satellites. In addition, the U.S. Strategic Command created a new program to encourage detailed information-sharing regarding the location and risks of objects in orbit. Today, that information is found in a publicly accessible platform managed by the Combined Space Operations Center and the 18th Space Defense Squadron.
While this disaster scenario is still a possibility, it’s less likely thanks to these changes as well as more advanced tracking technologies — like LeoLabs phased array radars and collision avoidance services — and operational capabilities from satellite owner-operators.
Dead object on dead object collision
Here’s what keeps me up at night: a collision between two massive dead objects in LEO. Why? Because this scenario is largely out of our control and fairly likely. On average, there’s one noteworthy conjunction event between two objects in LEO every minute. 75% of the most consequential events (i.e., those that will create the greatest number of fragments) are between two derelict objects.
When two objects collide in space, no matter the orbit, the number of fragments produced is proportional to the mass involved. The breakup of the 850 kg Fengyun 1C satellite in 2007, for example, resulted in more than 3,500 fragments larger than 10 cm. Any collision is a bad day, but if two massive dead objects collide in LEO, the result would be catastrophic. The collision would disperse debris across hundreds of kilometers in altitude and potentially impact multiple constellations, creating a ripple effect of dangerous collisional encounters. A rapid escalation of these types of events is indicative of what the beginning of the Kessler Syndrome would look like.
While this worst-case scenario hasn’t happened yet, we’re due for a collision between two massive derelict objects, according to observations made by my colleague Dr. Darren McKnight and his team. (More details to come in future editions of LeoPulse.)
Object colliding with lethal, small debris
Lethal, small debris (i.e., sized 5 millimeters — 10 centimeters) are numerous in LEO and can have a damaging effect on both operational and non-operational objects. A collision with a 10 cm debris fragment, for example, could cause an operational satellite to break up completely. While a collision with fragments between 1 to 10 cm would likely cause mission-terminating damage and a collision with a 5 mm to 1 cm debris fragment would likely cause mission-degrading damage. Any size fragment above a few millimeters is likely lethal to astronauts. Unfortunately, this smaller debris is not yet tracked, which means we’re unable to effectively mitigate the risks from it. It’s not all bad news though, we’re actively working on a solution at LeoLabs.
In 2021, the world witnessed the effects from this type of debris when a small fragment tore a 5 mm hole in Canadarm 2’s thermal blanket that was attached to the International Space Station. While the robotic arm remains functional, the incident was a clear indication of the risks posed by even a millimeter-sized debris fragment. Put simply, what we can’t see has the potential to kill us.
Operational payload attacked by an adversary
The United States, India, Russia, and China have proven their ability to physically destroy a satellite by testing anti-satellite weapons (ASAT). These tests have resulted in thousands of pieces of space debris in LEO. Fragments from the 2021 Russian ASAT test, for example, continue to cause dangerous conjunctions: we observed ~3,000 in August alone. While there is a US-led movement to ban kinetic ASAT tests on orbital targets, the risk remains. There is also the possibility of a cyber-attack which could render a satellite non-operational. Russia’s threats against Space X’s Starlink satellites during the war in Ukraine, for example, have illustrated how real this risk is.
How to prepare for and respond to an in-orbit disaster
With today’s technology, it’s easier to prevent a disaster in LEO than it is to clean up after one. With this in mind, preparatory actions should reduce the likelihood of a disaster and respond quickly to one. Below, I’ve listed a few necessary actions along with some of the activities that are already underway across the industry, these include:
- Remove old debris
- Prioritize collision avoidance
- Report regularly
- Strategize for survivability
- Create a response framework
- Publicize threatening actions
Remove old debris
Tracking and monitoring debris is not enough to effectively prevent a disaster; we must invest in debris removal technologies and missions, and fund research into cleaning up small debris fragments. Thankfully, we’re on the right path. In 2020, the European Space Agency (ESA) awarded a contract to ClearSpace for the world’s first active debris removal (ADR) mission. This follows multiple ADR demonstrations over the last few years by SSTL, Astroscale, and others. In addition, new technologies are under development that will enable the rapid de-orbiting of satellites. Regulatory measures are also addressing the space debris issue. Members of the U.S. Congress recently introduced the ORBITS Act aimed at funding the development of ADR technology, and the Federal Communications Commission (FCC) recently changed the 25-year rule for de-orbiting satellites to a 5-year rule.
Prioritize collision avoidance
We should prioritize enabling day-to-day collision avoidance maneuvers for active satellites to avoid dangerous conjunctions. Many satellite operators have collision avoidance as part of their operational routine, but this should be enhanced with more tracking infrastructure and a focus on smaller debris.
Reports should be published on the risk of collisions so that operators are aware of changes in the risk environment and regulators can update policies. This includes internal assessments by operators identifying the risks facing their critical satellite assets and reports by regulatory bodies highlighting changes in the risk environment.
Strategize for survivability
Operators building and maintaining constellations should think about how they can ensure the survivability of their system if an accident occurs. This can be achieved through increased impact tolerance, on-orbit servicing, or “shelter in place” protocols, which occur when a satellite reduces its cross-sectional area to reduce the probability of collision. Ongoing improvements to spacecraft design are promising. On-orbit servicing, for example, is moving into the mainstream with the launch of Northrop Grumman’s SpaceLogistics vehicles.
Create a response framework
If a disaster occurs, there should be a standardized framework that lists necessary actions to be taken on the part of operators and regulators, including identifying the object(s) involved, cataloging new debris, and possibly identifying necessary changes in traffic patterns.
Publicize threatening actions
If an ASAT test occurs, for example, that information should be shared publicly, along with a characterization of the collision risk that the event created. This information is important for deterring aggressive actions, informing diplomatic responses, and setting boundaries between acceptable and unacceptable behavior.
Mitigation through planning
In a sense, Earth’s orbits are like the oceans, forests, and deserts. They are environments that we both depend on and that need our protection. However, the orbital environment differs in one key respect: we’re building it and thus have the chance to preserve it for the good of everyone.
Unfortunately, like that giant asteroid hurtling towards Earth in Armageddon, a disaster in LEO is approaching, it’s just a matter of time.The impact can’t be dismissed by saying, “that’s not in my country or my city,” because a collision on the other side of LEO will arrive in your satellite constellation’s backyard 45 minutes later. That’s why we must collectively and actively plan for all possible scenarios. Whatever happens up there will affect all of us down here.