As companies send out thousands of low-orbit satellites to build a global internet, will astronomy be inhibited? And who controls satellite traffic?
Tech billionaire Elon Musk has said that his Starlink satellite-based internet will be able to connect anyone, anywhere – except the polar regions – by August of this year. Musk’s floating head made the extraordinary promise via video call at the 2021 Mobile World Congress (an annual mobile communications trade show) in early July.
Starlink, a global internet service carried by satellites rather than cables, promises to provide high-speed broadband internet to just about anyone who needs it. It appears to be an ideal solution for remote communities, where laying ground infrastructure can be challenging.
So far, so good. But, alarmingly for some, to achieve this feat Musk’s space company, SpaceX, already has approval to send some 12,000 satellites into low-Earth orbit (LEO) by 2026. That’s on top of the 1500 satellites already in orbit. In 2019 the company filed paperwork at the International Telecommunications Union for approval for 30,000 more.
Astronomers raise concerns
The prospect of a swarm of satellites orbiting our planet has led astronomers worldwide to voice concerns about potential interference with their research, and the obstruction of the night sky as a valuable natural resource.
Australia’s astronomer-at-large, Fred Watson, says these space-queues can pose a real problem for astronomers, both professional and amateur.
And Starlink isn’t the only player in this game. Rival company OneWeb plans to launch 48,000 satellites, and Amazon 3236 satellites as part of its Kuiper Systems constellation. These bring the total potential volume to more than 100,000 LEO satellites within a decade or two.
One of the major problems is that satellites are often visible from Earth, especially at sunrise or sunset when the light reflects off their surfaces.
In November 2019, Clara Martínez-Vázquez, an astronomer at the Cerro Tololo Inter-American Observatory (CTIO) in Chile, tweeted a photo of Starlink satellites streaking overhead, which were interfering with her observations using DECam, an experiment probing the universe for dark energy.
“Wow!! I am in shock!! The huge amount of Starlink satellites crossed our skies tonight at Cerro Tololo,” the caption read. “Our DECam exposure was heavily affected by 19 of them! The train of Starlink satellites lasted for over five minutes!! Rather depressing…This is not cool!”
Others voiced their concerns that a whopping 100,000 or more low-orbit satellites from the various satellite internet companies would make their observations more difficult.
The online space resource Heavens Above has a dynamic, 3D orbital display that allows us to track every Starlink satellite currently in orbit. Even without the promised 42,000 new satellites – or indeed the satellites from Starlink’s major competitors – it’s a vision of an Earth that appears swarmed.
On the display, some satellites appear in tight red lines as if marching in step – a consequence of their being launched into orbit close behind one another, 60 satellites at a time. Australia’s astronomer-at-large, Fred Watson, says these space-queues can pose a real problem for astronomers, both professional and amateur.
“You get these lines of spacecraft in these tight constellation clusters, and many astronomers have had their images ruined by them,” he says.
Starlink has offered their own suggestions for mitigating concerns. Strategies include altering the satellites’ orientation so that they are knife-edge to the sun and don’t reflect as much light back to Earth, as well as darkening satellites by applying a visor to block sunlight from hitting the spacecraft’s brightest points.
While these mitigations can help solve the problem of the satellites’ visibility to the naked eye, both radio and optical astronomy still face major issues.
“Space X has gone ahead and launched all these spacecraft with very little warning, and the astronomical community has been taken off-guard.”
The Square Kilometre Array Observatory (SKAO) is a joint collaboration between seven member countries (Australia, China, Italy, the Netherlands, Portugal, South Africa and the UK) to build the largest radio telescope in the world. SKAO will be composed of two radio telescope arrays, one in South Africa and one in Australia. Among many scientific feats, the observatory will look to understand how the first stars formed after the big bang, investigate dark energy, and scour for signs of life in the cosmos.
According to Watson, LEO satellite constellations will pose a major problem for radio telescopes like SKAO. In South Africa, the telescopes will use the same radio frequency – Band 5b – as the satellites themselves, hampering certain observations.
And Watson says even in Australia radio waves from local radio stations can bounce off any object in near space and reflect back to the telescope – creating a whole lot of extra “noise”.
Even for optical telescopes, Starlink’s proposed mitigations will not be able to entirely prevent interference.
“With wide-angle imagery of the sky, you’re essentially surveying the sky with very, very sensitive detectors,” says Watson. So, while you may be able to obscure satellites from the naked eye, “it’s not pushing them down beyond the detection of large optical telescopes”.
Certain telescopes will be disproportionately affected, for example the Vera C. Rubin Observatory currently under construction in Chile.
“It will survey the entire sky every six or seven days looking for transient events, including possible near-Earth impacting asteroids,” says Watson. “That’s going to be probably one of the most badly impacted.”
Who patrols the space highway?
The 1967 United Nations Outer Space Treaty (OST) sets principles for international space law.
But one of the major concerns among the astronomical community is the perceived lack of international oversight of a technological space that’s constantly changing.
“The problem is that organisations like the UN are slow and ponderous, and the horse has bolted on this issue,” Watson says. “Space X has gone ahead and launched all these spacecraft with very little warning, and the astronomical community has been taken off-guard.”
“If you want to put a satellite into orbit, you have to register with the International Telecommunications Union. And there’s legislation and procedure about how you do that to have an orbital slot allocated to you.”Kim Ellis Hayes
Kim Ellis Hayes is an international lawyer and space-law expert; she’s also in training to become a scientist-astronaut. She says that the laws governing who can put what into space are stringent but complex.
“If you want to put a satellite into orbit, you have to register with the International Telecommunications Union,” she says. “And there’s legislation and procedure about how you do that to have an orbital slot allocated to you.”
Everything that goes into space needs to be registered to avoid collisions. Besides the international regulatory process, each nation has its own regulatory process for placing objects into orbit; in the US, the Federal Communications Commission (FCC) authorises what American companies can and cannot put into space.
Most countries are signed up to the OST, and Ellis Hayes says that there are voluntary agreements that operate in between the international treaty and the national regulatory bodies that bind those countries to certain principles, like preventing contamination in outer space.
“So there’s a misconception that the people launching constellations of satellites are doing something outside the law,” Ellis Hayes says.
“Whilst it’s legal, the question is: should they be doing it because of the effect on science and astronomy? That raises a host of different questions.”
The sky as a cultural asset
The concerns that swirl around these satellite swarms are not just about science, they’re about society too.
In November 2020, the American Astronomical Society and International Astronomical Union’s Satellite Constellation Working Group (SCWG) published a paper in Nature Astronomy warning about the need to protect our natural night skies. The group argued for a radical shift in the international policy framework to define the night sky as an “ancestral global commons”.
The concerns tap into a collective cultural fear about the commercialisation of space, an area that’s perceived as a scientific and a spiritual realm.
“I think that there’s this big disconnect between radio astronomers and people launching constellations of satellites.”
Watson says that if 100,000 of these satellites orbit Earth, the night sky will undoubtedly change.
“That’s a huge number – you’ve got thousands above the horizon at any one time, so it’s certainly making a difference.”
He says it raises concerns about the cultural loss of the night sky as we know it: “We take our night sky seriously. We love watching the constellations, so it’s making a difference to that.”
The future of low-Earth orbit
The situation isn’t permanent. All satellites have a shelf life, and will eventually burn up in orbit.
“But it’s still something we’re going to be faced with for the next few decades, until some other technology replaces them,” says Watson.
In the meantime, cooperation is key. “The operators are talking to the astronomical community,” Watson says. “It isn’t a war. There’s work going on to try to mitigate the effects of these satellites, which may produce better results.”
Ellis Hayes agrees that the two communities – astronomers and tech companies – need to work together.
“I think that there’s this big disconnect between radio astronomers and people launching constellations of satellites,” she says. “It’s really important for radio astronomers to be really specific about the technical parameters of the interference.
“There needs to be a lot more consultation to make sure the two communities connect and discuss this issue in a constructive way.”
Amalyah Hart is a science journalist based in Melbourne.