A simulated image representing the projected contamination by satellite trails in a future space telescope image
NASA / Borlaff, Marcum, Howell
One in three images taken by the Hubble Space Telescope could be ruined if space companies’ plans to launch hundreds of thousands of satellites go ahead.
More than three-quarters of the nearly 14,000 satellites currently in orbit around Earth were launched in the past five years, many of them part of so-called mega constellations like that of Starlink, Elon Musk’s satellite internet company. But these numbers could be dwarfed if space companies’ proposals go ahead, with as many as half a million satellites planned to launch by the end of the 2030s, according to US Federal Communication Committee (FCC) filings.
Astronomers have already raised alarm at how these satellites could affect telescopes on Earth, but now Alejandro Borlaff at NASA Ames Research Center in California and his colleagues have found that they could seriously endanger space-based telescopes, too.
“When you position a telescope in space, it’s usually a very pristine environment. You don’t have any atmosphere, or city lights,” says Borlaff. “Now, for the first time, you have man-made objects that are somehow polluting the images – that was very striking.”
Borlaff and his team used FCC and International Telecommunication Union filings to predict how many satellites could be launched in the next decade and their planned orbits. Then they simulated how these could interfere with observations from four space observatories, including the Hubble and Chinese Xuntian telescopes, as well as the ARRAKHIS dark matter telescope, set to launch in 2030, and the SPHEREx galaxy telescope, which launched in this year.
The team found that if 560,000 satellites are launched as planned, there could be an average of two satellite trails for each Hubble photo and around 90 for each Xuntian photo, due to its larger field of view and orbital height.
They checked their simulations by predicting that with current satellite numbers, 4 per cent of Hubble images are affected by satellite trails, and this matched with an analysis of real images.
These predictions could come true if the planned satellite launches go ahead, says John Barentine of Dark Sky Consulting, a company based in Tucson, Arizona, but it’s unclear how many satellites will really be launched. “Many experts feel that the number of satellites that will actually orbit the Earth within about the next 15 years will reach a steady-state value of something more like 50,000 to 100,000.”
If the actual number of satellites is only a tenth of what is planned, then the consequences for space telescopes will be much less severe, says Barentine. “The number of trails per image will be only a factor of a few higher than it is now for ARRAKHIS and Xuntian and virtually unchanged for SPHEREx and HST.”
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