Astronomers push for global debate on giant satellite swarms

Source: Nature doi:

16 July 2021

Working with the United Nations, scientists hope to establish standards for satellite ‘megaconstellations’ and reduce disruption of astronomical observations.

Alexandra Witze

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

Now, in what would be the biggest international step yet towards addressing these concerns, diplomats at a United Nations forum next month might discuss whether humanity has a right to ‘dark and quiet skies’. The debate could initiate a framework for how scientists and the public would deal with the flood of new satellites — with many more expected.

Tens of thousands of satellites could be added to Earth orbit in the next few years to provide broadband Internet, if companies and governments build and launch all the networks, or ‘megaconstellations’, they have publicly announced. The sheer number of these could mean that hundreds are visible all night long, affecting the sky like never before in human history. “These constellations are changing dramatically the way space has been used,” says Piero Benvenuti, an astronomer at the University of Padua in Italy and a former general secretary of the International Astronomical Union (IAU).

He and other astronomers have been working through the IAU to raise international awareness of how the megaconstellations 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, realm of outer space. “The consensus has to come from all the countries,” says Connie Walker, an 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, that was held virtually from 12 to 16 July.

‘Free for exploration’

Many astronomers were caught by surprise in 2019, when the first batch of Starlink Internet satellites launched by SpaceX of Hawthorne, California, turned out to be brighter than expected in astronomical images. In response to complaints, SpaceX tested several strategies to darken the satellites; it now launches all of its Starlinks with sunshades attached, to make them less visible when sunlight reflects off them. Astronomers and representatives of several companies, including SpaceX, have settled on a brightness threshold for satellites that is slightly fainter than the human eye can see in a dark sky. Starlinks are close to that brightness threshold but do not currently meet it, says Meredith Rawls, an astronomer at the University of Washington in Seattle.

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