NASA warns 560,000 satellites could contaminate space telescope images

Light emitted or reflected by the half-million satellites humanity intends to place in Earth’s orbit over the next few years could spoil nearly every image captured by space telescopes, NASA astronomers warned on Wednesday.

Researchers have long raised concerns that light pollution from ever-larger satellite fleets could jeopardise the dark skies visible from Earth.

A study in the journal Nature has now become the first to calculate how the vast satellite numbers proposed for the future could enter the field of view of telescopes in space as they observe the Universe.

Satellite constellations threaten space telescopes

According to the study, the number of objects in low Earth orbit has surged from around 2,000 in 2019 to 15,000, with many belonging to billionaire Elon Musk’s Starlink internet constellation.

Yet this is only a small fraction of the satellites expected to arrive.

The study said that, if every proposal currently submitted to regulators proceeds, 560,000 satellites will be orbiting Earth by the end of the 2030s.

This represents "a very severe threat" for space telescopes, Alejandro Borlaff, the study’s lead author at NASA’s Ames Research Center in California, told AFP.

For their research, astronomers modelled the effects that 560,000 satellites would have on four space telescopes.

The findings showed that light reflected by satellites would affect 96 percent of the images recorded by NASA’s SPHEREx telescope, the European Space Agency’s proposed ARRAKIHS telescope and China’s planned Xuntian telescope.

The Hubble Space Telescope, whose narrower view makes it less likely to photograph a satellite, would nevertheless have one-third of its images contaminated.

Effects on astronomy and asteroid detection

Such interference could disrupt a broad range of scientific work.

"Imagine that you are trying to find asteroids that may be potentially harmful for Earth," Borlaff said.

An asteroid moving across the sky "looks exactly like a satellite… it's really hard to figure out which one is the bad one," he added.

Certain space telescopes, including the renowned James Webb, would not be affected because they orbit at a stable location known as the second Lagrange point, 1.5 million kilometres from Earth.

'As bright as the brightest star'

One possible measure would be to place satellites below the altitude of space telescopes, although the study warned this could contribute to depletion of Earth’s ozone layer.

The simplest answer might therefore be to send fewer satellites into orbit.

However, rivalry between satellite internet providers, combined with growing demand generated by the artificial intelligence boom, means that outcome appears unlikely.

Borlaff said that almost three-quarters of satellites now in orbit belong to Musk’s Starlink network.

However, the study projected that Starlink would account for only 10 percent of all satellites within a couple of decades as competitors launch their own fleets.

In the meantime, companies could assist telescope operators by sharing information about their satellites’ positions, orientations and colours, Borlaff said.

Satellites are also becoming substantially larger.

Borlaff said satellites with an area of 100 square metres are, to the unaided eye, "as bright as the brightest star that you can see in the sky".

But plans now exist for satellites measuring 3,000 square metres, intended to meet AI’s data demands.

Borlaff added that these enormous satellites could be "as bright as a planet".

© Agence France-Presse