Light from satellites is obstructing the views of land telescopes.Credit: Alan Dyer/VWPics/UIG/Getty
Satellites are increasingly a global-communications lifeline, allowing people in remote areas, even war zones, to make phone calls and get online without the need for ground-based infrastructure. Services such as SpaceX’s Starlink, by far the largest of the networks of telecommunications satellites in low Earth orbit, have been booming during the past decade. Between 2017 and 2022, companies requested access to the radiofrequency spectrum for more than one million satellites.
This success comes at a cost, with mounting concerns about safety and sustainability. As things stand, most satellites are single-use products with a lifetime of 15 years or less. Moreover, space debris is a growing problem, as physicists Richard O. Ocaya at the University of the Free State in Bloemfontein, South Africa and Thembinkosi D. Malevu at North-West University, Potchefstroom, South Africa, describe in a Comment article. The satellite boom raises key questions about whether humanity could or should clutter the environment around Earth without regulation.
Swarms of satellites are harming astronomy. Here’s how researchers are fighting back
Astronomers are raising their voice in this debate. Researchers pointing their telescopes at stars and galaxies are increasingly finding their observations marred by light streaks and radiofrequency interference from satellites flying overhead. The problem is particularly acute for the Vera C. Rubin Observatory’s upcoming ten-year survey of the cosmos. This flagship telescope, built and operated by a US-led team of funders, is about to begin photographing the entire sky every three nights from its mountaintop location in Cerro Pachón, Chile. Its enormous ‘eye’, the largest camera ever built, will pick up everything that passes through its vision — including thousands of satellites.
In the past five years, some astronomers and satellite operators have collaborated to preserve ‘dark and quiet skies’, as we report in a News Feature. This could involve changing a satellite’s design to make it dimmer or coordinating activities so that astronomers can point their telescopes to regions where satellites aren’t flying at any given moment. But what is needed are some shared rules or guidelines, representing international best practice, that astronomers and satellite operators can agree on.
Work towards this is under way to an extent, but the pace needs to quicken. Three years ago, the International Astronomical Union (IAU) established a centre for the protection of dark and quiet skies, in Paris. It is a hub for scientific, policy, industry and community discussions about satellite swarms, and it has put forward common-sense recommendations that are already being adopted. French satellites, for instance, will tone down their brightness, after France updated its national space law last year in response to IAU recommendations.
Space debris is falling from the skies. We need to tackle this growing danger
The IAU team also helped to raise awareness of dark and quiet skies at a meeting of the United Nations Committee on the Peaceful Uses of Outer Space in Vienna last month, the first time that the issue had been formally discussed at a global level. Also in February, Chinese astronomers and satellite operators met with US and European researchers to share ideas on how radio astronomy and satellites can coexist. Such conversations should be encouraged.
Raising awareness is the first step. Finance is another. The IAU centre is run on a shoestring of in-kind contributions and free time donated by astronomers. Funders should step up with more support, as the US National Science Foundation did last year with a US$750,000 grant to the IAU to develop software tools that predict when satellites will appear in telescopes’ fields of view.
Then there’s the role of those who build and fly satellites. As the biggest operator, with more than 7,000 satellites, SpaceX, based in Hawthorne, California, has commendably led the way by working with astronomers to reduce the impact of its satellites on Rubin and other observatories. Other companies should follow SpaceX’s lead. This could include releasing more information on satellite specifications and the frequencies of their radio transmissions, as well as real-time locations of the craft. Much of this information is commercially sensitive, but at least some could be shared in ways that would still be useful to astronomers, with proprietary details redacted.
Last but not least — and some would say most importantly — there needs to be a discussion on regulation, or rather, the lack of it. Most companies are not dimming their satellites at least partly because there are few regulations saying that they must. There are several regulatory agencies for satellites, but they have limited, if any, enforcement power when it comes to the impacts of satellites on astronomy.
Sky rights
Beyond the clash with astronomers’ observations, discussions about the future of satellite swarms need to be integrated into broader conversations about space sustainability and human rights. That includes integrating perspectives from Indigenous peoples, many of whom have important connections with the night sky, but who have long been marginalized from decision-making and economic power in outer space.
International discussions need to recognize the rights of Indigenous peoples in space as well as on Earth, says Hilding Neilson, a Mi’kmaw astronomer at Memorial University of Newfoundland in St. John’s, Canada. In an article for the IAU centre, he argues that UN recognition of Indigenous rights must extend to outer space (H. Neilson Preprint at arXiv https://doi.org/pbj5; 2024). “If you’re going to destroy the night sky through light pollution or satellite pollution, that’s colonization,” he says.
The skies are a global resource, shared by all of humanity, and it is crucial that decisions about its use account for the needs of all stakeholders. Satellite connectivity remains a boon for many people, including Indigenous communities in remote and under-served areas. This is why the conversation about astronomy and satellites cannot be reduced to ‘satellites are bad and we must save the night skies for astronomy’. Satellites and astronomy can co-exist. It is up to everyone to find the path forward together.
