Going by the paperwork, 1 million satellites are headed for the skies. The question is, how many of these are real?
The skies are getting crowded: Anyone who has looked up at the stars during one of these autumn evenings has seen a satellite or three (or 30!) pass overhead. Thosee moving sparks of light are already many, but there will be more: There are currently filings for 1 million satellites and counting. That rather large number conjures up images of a night sky to crowded to even see the stars, much less do any useful astronomy.
The question is, how many of these satellites-to-be will become reality?
One Million Satellites — on Paper
The count comes from filings submitted to the International Telecommunication Union (ITU). Those submissions in turn come from ITU’s 193 member states, each of which files on behalf of private companies or government agencies. Each filing contains information about how many satellites will go up, which orbits they will occupy, and which frequencies they will use for operations.
The number of filings has skyrocketed, and so have the number of proposed satellites. Some filings make requests for tens or even hundreds of thousands of satellites. One memorable filing, made by Rwanda in 2021, was for a 337,320-satellite constellation named Cinnamon-937. That filing was eventually tied back to E-Space CEO Greg Wyler, who has since submitted another application through France for another 116,640 satellites. Both applications are still active.
“Greg Wyler said during the summer that they are planning for at least 30,000 satellites, while someone else from E-Space said they are planning for ‘about a few thousand’,” says Ewan Wright (University of British Columbia, Canada). “So we don’t even know what order of magnitude of satellites E-Space is actually planning to launch.”
At least some of the many ITU filings are almost certainly speculative, similar in concept to the land speculation that occurred back in the “Wild West” — but this time in space. The ITU has rules in place to prevent this; since 1997, for example, it has required a certain amount of due diligence before filings can be made. But efforts so far evidently haven’t been enough.
To stem the speculative tide of satellites, political scientist Andrew Falle, Wright, and their colleagues at the University of British Columbia, Canada, suggest in Science’s Policy Forum that this situation actually presents an opportunity for better regulation. “The ITU filings are the warning, and also part of the solution,” they write.
On November 20th, government and industry representatives from around the world will come together to decide on new regulations for the radio-frequency spectrum. While decisions at the World Radiocommunications Conference might not make headlines, any new rules agreed upon there will help shape the nature of the satellite problem in our skies.
“The rules would mostly help us understand how big the problem is going to be, but that's important,” says Jonathan McDowell (Center for Astrophysics, Harvard & Smithsonian). “It's hard to know how to prepare mitigation strategies when the number of satellites that are really going to go up is uncertain by a factor of 10 or more.”
The Satellite Problem
Proposed modifications to ITU’s regulations would seek to address a couple different problems. Because the ITU regulates, among other things, the orbits of new satellites, one key question to be addressed at the conference is space debris.
So far, SpaceX’s 4,924-and-counting Starlink constellation has managed to operate sans collisions. But just one collision could do a lot of damage, especially as low-Earth orbit becomes more and more crowded. “The concern is that eventually they will start colliding (however spiffy their automatic avoidance algorithms are) and generating a lot of debris,” McDowell says.
Another key question is that of frequency management. The radio spectrum is protected by international and national law (via the ITU as well as national regulative agencies, such as the Federal Communications Commision in the U.S.). Most protection goes toward communication, but radio astronomy does have a few protected bands of its own. Unfortunately for radio astronomers, those narrow slivers of frequency were decided in 1979 and have changed only a little since then.
The actual practice of radio astronomy isn’t limited to these protected bands, however, because astronomy doesn’t generally require transmitting signals, just receiving them. In particular, the detection of very low frequencies could enable astronomers to see signals from the cosmic dawn, allowing them to test ideas about the birth and fate of the universe. The Square Kilometer Array Observatory (SKAO), being built to the tune of $2.2 billion in South Africa and Australia, was developed especially to tune in to the early universe.
But such studies require an exceedingly low level of noise, and in a new study in Astronomy & Astrophysics, Steven Tingay (Curtin University, Australia) and colleagues used a SKAO prototype telescope to show that Starlink emits radio at low frequencies, both intentionally (for operations) and unintentionally (from avionics or propulsion systems onboard the satellites). SpaceX would need to reduce these emissions by factors of 100 or even 1,000 to avoid hindering radio astronomy experiments.
Promise and Pragmatism
SpaceX has willingly modified its satellites to address problems in astronomy conducted in visible light — in fact, its much larger Generation 2 satellites are largely (though not completely) within astronomer-recommended brightness limits. A similar spirit might help in the radio.
“It is possible that engineering mitigations on the spacecraft could bring those emissions down to something more manageable,” Tingay says, who has discussed the problem with SpaceX engineers. “There were certainly no promises to embark on mitigations, but a positive discussion about the possible origins of the emissions from the Starlink systems and a recognition of the impacts on astronomy.”
There's clearly more work to be done: “I think we are going to have to spend considerable time understanding the complex impacts and building a comprehensive evidence base in order to go further, with SpaceX and/or via the ITU,” he adds.
Some issues are already on the agenda, which may help the ITU to address these problems. Among them are “post-milestone reporting” (in other words, requiring nations to report major satellite failures), required monitoring of the total radio power satellites are emitting, and limiting the amount that satellites are allowed to deviate from their assigned altitudes. These changes will help regulate the radio spectrum and reduce the risk of creating space debris, but astronomy may indirectly benefit from such changes, too.
Falle and team are also suggest other items that could yet be placed on the agenda, including limits on the number of satellites in individual constellations or orbits and higher fees or similar consequences for large filings. They also suggest that current rules could address the issue of filings submitted via “flags of convience states.”
“New or updated rules can be adopted during those conferences through a consensus-based process,” Falle notes. “For this reason, we try to suggest very general steps that member states could take.”
Yet, even if the filing process is restricted so as to mitigate speculation, the fact remains that low-Earth orbit is premium real estate. In addition to Starlink’s 4,924 satellites, and OneWeb’s 634 satellites, Amazon just launched two prototypes for its planned 3,200-satellite Project Kuiper. Other projects are underway, too. It’s possible new ITU rules may stem this coming tide, but the main advantage for astronomers will be simply knowing the size of the beast they’re dealing with.
Editorial note (Oct. 20, 2023): The article was updated to include additional information from Andrew Falle and colleagues.