Astronomers push for global debate over giant satellite swarms

SpaceX launched a batch of Starlink satellites into orbit around Earth on January 6, 2020.Credit: Paul Hennessy / NurPhoto / Getty

Aerospace companies have launched around 2,000 Internet satellites into orbit around Earth over the past 2 years, nearly doubling the number of active satellites. This has raised concerns among astronomers and other sky watchers, who are concerned about interference with night sky observations.

Now, in what would be the biggest international step yet to address these concerns, diplomats at a United Nations forum next month could discuss whether mankind has a right to a “heaven.” dark and calm ”. The debate could initiate a framework for how scientists and the public would cope with the flood of new satellites – and many more are expected.

Tens of thousands of satellites could be added to Earth orbit over the next few years to provide high-speed Internet, if companies and governments build and launch all networks, or “mega-stellations,” they have publicly announced. The large number of them could mean that hundreds are visible all night long, affecting the sky like never before in human history. “These constellations are radically changing the way space has been used,” explains Piero Benvenuti, astronomer at the University of Padua in Italy and former secretary general of the International Astronomical Union (UAI).

He and other astronomers have worked through the IAU to raise awareness in the international community about how mega-stellations are affecting scientists and members of the public. They say the goal is not to pit astronomers against satellite companies, but to develop a vision of how to fairly use the shared, but ungoverned, domain of outer space. “Consensus has to come from all countries,” says Connie Walker, astronomer at the National Optical-Infrared Astronomy Research Laboratory in Tucson, Arizona. Scientists discussed these and other topics at a conference on satellite constellations, called SATCON2, which was held virtually July 12-16.

“Free for exploration”

Many astronomers were taken by surprise in 2019, when the first batch of Starlink Internet satellites launched by SpaceX from Hawthorne, Calif., Turned out brighter than expected in astronomical images. In response to the complaints, SpaceX tested several strategies for darkening satellites; it now launches all of its Starlinks with lens hoods attached, to make them less noticeable when sunlight reflects on them. Astronomers and representatives of several companies, including SpaceX, have set a light threshold for satellites that is slightly lower than what the human eye can see in a dark sky. Starlinks are close to this luminosity threshold but do not currently reach it, explains Meredith Rawls, an astronomer at the University of Washington in Seattle.

The threshold is an objective and not a requirement. Even if companies adhere to it, satellites will be visible in telescopes. They are particularly disruptive to telescopes that monitor large areas of the sky. Up to 40% of the images that will be taken by the Vera C. Rubin Observatory, a major US telescope under construction in Chile, could be marred by satellite trails at dusk and dawn.1. Transmissions from some satellites could also interfere with radio telescopes such as the Square Kilometer Array, a large international observatory under construction in South Africa and Australia.

A chain of Starlink satellites cross the sky diagonally above a lighthouse at night

A chain of Starlink satellites is visible in the night sky.Credit: Yuri Smityuk / ITAR-TASS News Agency / Alamy

There are no laws governing the impact of satellites on the night sky. The 1967 Outer Space Treaty, which is the founding document on international relations in outer space, asserts that outer space is “free to explore.” But there is a precedent for asking the UN to try to reach an international consensus on how to deal with the visual pollution of the skies. In 2002, at the request of IAU, the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) briefly discussed the possibility of regulating “intrusive space advertising”, such as billboards. spatial displays that would be visible from Earth. A trader proposed this type of billboard for the 1996 Olympics, but it never came true and COPUOS never acted on the subject.

International relationships

In April, Benvenuti and other astronomers were able to raise the issue of satellite constellations at a meeting of the COPUOS subcommittee, when delegations from five countries signed an IAU-led white paper saying that mega-constellations are a concern for astronomers and others. “The presentation of the document gave us a reason to talk about the issue to all those space policy specialists in many countries,” says Andy Williams, head of external relations at the European Southern Observatory in Garching, Germany. “It’s a fantastic way to raise awareness. The UN does not have the power to regulate launches, but it could bring nations together to set international standards that would encourage satellite operators to consider and mitigate the effects of their mega-constellations on astronomy.

The delegations of the United States, Canada and Japan proposed that the subcommittee continue to consider the topic of satellite constellations as a regular agenda item for its meeting. But those in China and Russia objected, saying they needed more time to study the issue. (China, like several other nations, is making plans for a satellite mega-constellation to provide broadband internet around the world.) Now Benvenuti and his colleagues are working to see if the whole of COPUOS could take up the topic at the time. of its next meeting, which begins on August 25. This kind of popular pressure from astronomers is the main way for nations to start discussing the subject. “The debate will have to take place in international forums,” explains Tanja Masson-Zwaan, researcher in space law at the University of Leiden in the Netherlands.

In the meantime, astronomers are working on other solutions to the problem of interference from satellite constellations. These include the development of databases of satellite positions to predict when satellites will pass overhead – so that telescopes can temporarily avoid that part of the sky – and software to erase satellite tracks from images. .

Others are working to bring more voices into the mega-constellation debate so that it is not dominated by Western astronomers. Many Indigenous communities have deep cultural histories tied to the stars, says Aparna Venkatesan, an astronomer at the University of San Francisco, Calif., Who is leading efforts to make those voices heard. The appearance of satellite streaks can harm this cultural identity.

But time is running out. SpaceX is launching new bundles of Starlinks – around 60 satellites per bundle, sometimes multiple times a month. “People spend years building relationships, but in the meantime the satellites are launched continuously,” says Venkatesan. “It’s almost like we came up with solutions to a problem three years ago.”


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