Companies' plans for satellite constellations 'put night sky at risk'

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Schemes from firms such as Elon Musk’s SpaceX raise fears for our view of heavens

The night sky over Exmoor national park.
The night sky over Exmoor national park. Photograph: Ben Birchall/PA
Science editor

Last modified on Fri 10 Jan 2020 01.08 EST

The spectacular view of the heavens on a clear, dark night is under threat from plans to launch tens of thousands of satellites that will be visible tearing across the sky, astronomers have been told.

Tech firms have begun to place a number of satellite “mega constellations” into low Earth orbit in a move designed to expand internet access and open new markets in the developing world.

But while companies need permits before they can launch their satellites there is no global body overseeing the impact that a surge in visible spacecraft might have on the appearance of the night sky.

“We stand to lose our connection with nature,” said Ruskin Hartley, executive director of the International Dark-Sky Association (IDA), before raising his concerns in a presentation at the American Astronomical Society meeting in Honolulu on Wednesday. “We need to make sure that in the debate and dialogue the people who enjoy being out under a dark sky have a voice.”

On Monday, Elon Musk’s SpaceX launched a third batch of 60 Starlink satellites, which relay the internet to Earth. The firm has secured permission from the US Federal Communications Commission to launch 12,000 Starlinks and is seeking approval to boost the constellation with 30,000 more. Other firms, such as Amazon, Samsung, Oneweb, and Telesat, all have plans for smaller constellations.

Astronomers raised concerns last year that so many satellites, which would far outstrip the 5,000 or so in orbit today, would affect their observations. Researchers on the $1bn Large Synoptic Survey Telescope being built in Chile found that satellites would leave streaks across many of the images they collected, particularly at dusk and dawn.

“Whether people are professional astronomers or individuals who have never looked through a telescope, what unites us is the sense of awe and the sense of looking at the sublime when we are out under a clear, dark, sky,” said Hartley. “It’s that sense that you are looking into the depths of the universe. People are seeking out places where they can go and enjoy an unimpeded view of the night sky, but if we are going to put up this veil of moving objects, if there are no places left where we can do that any more, what does that mean for us?”

With 12,000 new satellites in low Earth orbit, about half a dozen might be visible at any one time at a dark sky site, said Hartley. That number could grow to two dozen with 40,000 more satellites.

SpaceX, to minimise the visibility of its satellites, said it would be painting the undersides of them black in future.

Most affected by the companies’ plans would be the dedicated dark sky parks and reserves, ranging from Exmoor national park in the UK, to the River Murray reserve, in Australia. Often, local communities have spent years working with councils and businesses to minimise the light pollution that obscures the stars and planets visible on clear nights.

Hartley urged the satellite companies to back three principles which the IDA had drawn up to protect dark skies around the world.

The first principle is to ensure that satellites are not bright enough to be seen with the naked eye, even at dark sky sites. The second rule calls on companies to make sure satellites rarely tumble and create “flares” in the night sky. Finally, firms must be transparent about when they are launching, where their satellites will orbit, and how they will bring the devices down when they become defunct.

Jo Richardson, founder of Space Detectives, an outreach company funded by the UK and European Space Agencies, said growing light pollution already meant that many schoolchildren were unable to see even the most common star constellations.

She said: “In a lot of places the urban sprawl has already obliterated much of the night sky. We talk about plastic in the oceans and pollution in the air, but there’s never any importance placed on light pollution. Children are growing up without ever having the chance to look up at the dark sky. It’s not enough that we’re fighting light pollution from the Earth, we’re now going to be fighting it from space as well. There is a feeling of hopelessness. There’s a feeling that people just don’t get it.”

Hayden Goodfellow at Kielder Observatory in the Northumberland and Kielder Water and Forest International Dark Sky Park said: “The night sky is a wonderful resource which can be enjoyed by anyone, with any equipment or level of expertise. In Northumberland we pride ourselves on providing views of the sky free from artificial glare. There is no doubt that the number of satellites being proposed will have an impact on our views of the sky but we are hopeful that SpaceX and other companies will remain engaged with the astronomical community to minimise their impact on observations.”