For millennia, humans have peered into the night sky hoping to divine their place in the universe. Telescopes and other technologies allowed them to look ever deeper. Now that age-old custom is running up against a very modern threat: satellites.
More than 3,300 operational satellites are currently in orbit, according to the Union of Concerned Scientists. As global demand for broadband and other services soars, that number could exceed 100,000 in the years ahead. This has scientists worried: Satellites reflect sunlight, causing bright trails across the night sky, which in turn can impede crucial observations or corrupt astronomical data.
Without government action, the rise of satellite constellations could soon make ground-based telescopes all but unusable — affecting everything from the study of the stars to the search for dangerous near-Earth objects.
Astronomers have long had a fraught relationship with technology. Tensions date to the 19th-century gas lamp. Cheap lights improved public safety, enabled factories to keep longer hours and allowed for the emergence of nightlife. But by the mid-1800s, big cities were so well lit (and so polluted) that astronomers were losing sight of the dimmest stars. In response, they tended to decamp for remoter pastures. When the countryside lit up, too, they pushed out to the world’s last dark places, such as the remote deserts of northern Chile.
Even those outposts weren’t entirely free from interference, and researchers had to learn to filter out (for example) radio and television signals. But bigger telescopes and better technology still allowed them to scan the cosmos effectively.
In 1997, Motorola Solutions Inc. made that task more difficult when it launched the first of dozens of communication satellites in a “constellation” around the Earth. Now operated by Iridium Communications Inc., the array provides global voice and data coverage. But its powerful transmitters also interfere with the bands of radio spectrum allocated (under international agreement) to scientific instruments like telescopes. That interference is growing worse every year, as more and more satellites come online.
SpaceX has already launched more than 1,300 satellites for its broadband network, called Starlink, and has been authorized to send up nearly 12,000 in total. OneWeb plans to have some 7,000 in orbit in the next few years, while Amazon.com Inc. wants to launch 3,236. Meanwhile, China is preparing for two constellations with a combined 12,992 satellites.
Last year, dozens of researchers from around the world met virtually to study the risks these launches pose. Results are being presented this week at the Committee on the Peaceful Uses of Outer Space at the United Nations. Their conclusions are grim: “The situation for astronomy is reaching a point of no return from continuous interference with observations and loss of science.”
Up to 40 percent of the images collected by wide-field telescopes could be rendered unusable, they found. Surveys of moving objects, including the International Asteroid Warning Network, could also be in jeopardy, while radio-telescope operators will find it increasingly hard to point at the sky without finding a satellite in their path.
Fortunately, SpaceX and OneWeb have publicly recognized these dangers. SpaceX, in particular, is working with astronomers to “darken” its satellites so that they have less impact on observatories. But even if both companies devise reasonable solutions, there’s no assurance that their competitors (public and private) will do the same.
Does it matter? From a cultural standpoint, it would be tragic if the ancient pursuit of studying the night sky were degraded to such an extent. On a more practical level, astronomy has played a huge role in advancing human welfare and boosting technologies from navigation to communication. Are future discoveries worth jeopardizing for the sake of global broadband? With some reasonable precautions, that should be a false choice.
As a start, bodies such as the U.N. should be raising the alarm and studying possible solutions to this problem. Existing agreements for divvying up radio frequencies could be a starting point for new talks on mitigating satellite risks. Governments should also create satellite-licensing agreements that require companies to protect essential scientific efforts. And operators should follow SpaceX’s lead in reaching out to scientists and incorporating their needs into technology designs.
There’s no going back to the dark nights of our ancestors. But with some foresight, policymakers should be able to ensure clearer skies into the future.