What If Satellites Collide Because No One Is Checking Email?
What If Satellites Collide Because No One Is Checking Email?
Back in December the Chinese government notified the United Nations that its new space station had twice maneuvered out of the way of satellites belonging to Elon Musk's Space Exploration Technology Corp., or SpaceX, in 2021. Yet rather than phone SpaceX, NASA or even the White House, China leaned on a less reliable means of communication to express concern and resolve the matter.
“Chinese authorities tried multiple times to reach the US side via e-mail, but received no reply,” a Chinese Foreign Ministry spokesperson explained last Thursday, when commenting on the near collision.
Those unrequited Chinese missives might be humorous if they didn't reveal a much bigger problem. Despite a rapidly growing number of spacecraft (and junk) orbiting the Earth, there is no formal international framework for avoiding collisions. That's a dangerous risk, especially as tensions rise between China and the US, the world's two leading spacefaring nations.
An accidental collision between their satellites and spacecraft could easily be misinterpreted as aggressive action and spiral into a crisis, threatening economies increasingly dependent on space. Both countries should seek an agreement that reduces such a possibility.
In 1957, Sputnik, the Soviet satellite that kicked off the space age, had the Earth's orbit to itself. Over the next half-century, a handful of countries, led by the US, added around 60-100 satellites per year to the vast spaces around the planet without worrying about collisions.
Then in the 2010s, the lazy pace of launches quickened as SpaceX inaugurated the era of low-cost private launch services. In 2020, more than 1,000 satellites were successfully launched in a year for the first time. As of September 2021, there were approximately 4,550 operational satellites in orbit, and at least another 3,000 non-functional ones.
The numbers will grow quickly over the next decade as private companies and governments launch constellations of communication satellites that work together. Starlink, the name of SpaceX's planned constellation of 4,408 satellites, began launching in 2019. There are currently more than 1,460 operational Starlink satellites in orbit, and the company is requesting regulatory approval for an additional 30,000. And that's just the start: By one accounting, governments and private companies have plans for more than 100,000 satellites, including a Chinese constellation of 13,000.
In the absence of an international agreement on space traffic management, different governments and private entities are free to choose how they track and avoid other space objects. For years, the US military, relying upon its extensive network of sensors (and those of its partners), has provided the most comprehensive tracking system, both for US entities, and those abroad who sign up for the data (China does not).
But the US military only has the right to redirect its own satellites. The most it can do in the event of a collision between objects owned by others (including private US space entities like SpaceX) is send alerts, typically delivered by email. And there can be a lot of alerts: The European Space Agency’s operations center in Darmstadt, Germany, receives hundreds of email alerts per day.
If a satellite operator pays attention to email, the system works fine. But satellite operators, like everyone else, don't always stay on top of their in-boxes. For example, in 2019 SpaceX missed multiple email warnings that one of its satellites had a 1 in 1,000 chance of colliding with a European Space Agency satellite. SpaceX later confirmed that a “bug” prevented the company from seeing the ESA's increasingly worried messages. In the meantime, the ESA unilaterally maneuvered its satellite out of the way.
The absence of an international framework for avoiding orbital collisions creates other problems, too. For example, current definitions of what constitutes a potential “near miss” between spacecraft vary widely, often by miles. China's alarm over Starlink's satellites is informed, at least in part, by a much wider definition of what's a risk to hit its space assets than the one embraced by SpaceX and the US government (SpaceX did not respond to a request for comment). That difference in opinion can create a crisis where one might not exist if the definitions aligned.
The good news is that China's 2021 encounters with Starlink's satellites appear to have alarmed the Chinese authorities into seeking a solution. Last week, China's Foreign Ministry stated an interest in establishing “a long-term communication mechanism with the US side” to safeguard spacecraft from collisions.
It's an invitation worth taking, cautiously. Both sides maintain spy satellites and other national security assets whose locations and purposes they won't be keen to reveal to the other. The US side, with its more advanced capabilities, might even view China's invitation as a ruse designed to uncover the full extent of its assets and interests, as well as those of its private space sector.
But those are reasons to be careful, not to avoid exploring a means to communicate efficiently with an emerging space power. In the short term, universal agreement on what precisely constitutes an orbital near miss would be useful to the services and start-ups in both countries that seek to help satellite operators avoid collisions.
Longer term, the two countries will need to agree on ways to communicate the locations of satellites. Rather than delay agreement by focusing on all satellites, including those related to national security, they could start by focusing on commercial constellations. Eventually mechanisms can be explored for more sensitive objects, with the hope that any US-China communication framework can serve as a foundation for a broader and more difficult global agreement on orbital traffic.
Space will never be safe. But humanity will need more than emails to help reduce the unnecessary risks.