SpaceX has a plan to launch 42,000 Starlink satellites into orbit, but the first 120 are already blocking astronomers' view of space

Elon Musk’s space firm has grand plans. As well as going to Mars, SpaceX is set to launch up to 42,000 of its small Starlink satellites into orbit to provide worldwide internet access. This means launching more than ten times the number of satellites already in orbit into what is an already crowded part of space.

But since the launch of the first batch of satellites in May 2019, astronomers have worried about the impact the deluge of additional satellites will have on the night sky. This week, for the first time, a pair of astronomers saw first-hand the impact these ‘mega-constellations’ of satellites will have.

In the early hours of Tuesday morning in a remote observatory in Chile, Cliff Johnson and Clarae Martínez-Vázquez were going about their normal routine when something unusual and bright crept into their field of view.

The pair of astronomers were observing from the Dark Energy Camera (DECam), part of a four-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Coquimbo, Chile. The telescope is part of the Dark Energy Survey, looking for answers about what the mysterious force is that’s ripping our universe apart.

While they were observing, the researchers saw a “huge amount” of Starlink satellites crossing their skies. “Our DECam exposure was heavily affected by 19 of them,” Martínez-Vázquez wrote on Twitter. “The train of Starlink satellites lasted for over five minutes!! Rather depressing… This is not cool!”

Johnson, who works for Northwestern University in Illinois, put together a raw photograph of the satellites. “The exposure was a six minute optical wavelength observation taken as part of the DELVE survey that is imaging the outskirts of the Magellanic Clouds and broadly mapping the southern sky in search of neighbouring dwarf galaxies” he says.

The bright light reflected from the sun by the satellites shone onto the camera and causes loss of pixels, meaning information that could have been captured has been lost. “This was a noticeable, but not hugely destructive impact” he says. It affected one image out of around 40 taken during their observing run which lasted for the night, and only a small fraction of the pixels in that image needed to be discarded.

But things could be about to get a lot worse. Only two batches of satellites have been launched so far, with the second lot of 60 going up on November 11. Twenty-four batches are needed before they can cover the whole globe. Although they aren’t providing a service yet, the satellites are already having an impact on the night skies.

As the satellites had only been launched on November 11, they had not yet reached their orbital altitude so were closer to Earth than they will be when they are operational. Currently, SpaceX has permission to launch 12,000 satellites, which are planned to be sent at a rate of 60 every two weeks until the mid-2020s, but last month it filed documents showing plans to launch 30,000 more. And it’s not the only one; OneWeb and Amazon have plans for similar fleets.

“This is the key,” says Johnson. “While this event was a relatively low-impact annoyance with relatively small impact on our science, the prospect of many thousands of satellites launching in the coming years could have a dramatic impact on observations.” He says he agrees with a recent statement from the International Astronomical Union, calling for regulation and consultation regarding the possibility of satellite constellations numbering in the tens of thousands.

“We are just seeing the tip of the iceberg after the first of many planned launches,” he says. ”It is important to have discussions now about how best to move forward, hopefully in cooperation with SpaceX and others.”

The average number of stars visible with the naked eye in areas of the lowest light pollution is about 5,000. Compared to the numbers of satellites proposed to be launched in the coming years, this is relatively small. Currently, satellite constellations like Iridium, owned by Motorola, provide communications like mobile data, but it only has a constellation of 66 satellites.

“Previously Iridium and other satellites were relatively few and had little effect on astronomy” says David Blanchflower, an astronomer and astrophotographer. With the numbers being discussed now, the satellites will be hard to avoid for astronomers, he says. According to researcher Cees Bassa from the Netherlands Institute for Radio Astronomy, once a constellation of 1600 satellites is launched, about 84 satellites would be above the horizon at any time.

“Astrophotographers will be especially affected” Blanchflower says, drawing on his own experiences of spending hours photographing the night sky. “Many hours of work could be spoiled by passing flashes of light.”

“When there will be more Starlink satellites, they impose two major problems” says Robin Mentel, who studies astronomy at the University of Leiden. “The problem with the StarLink satellites is not only that they will be numerous, but also that they will be very bright” he says.

SpaceX has previously said it will paint the base of its satellites black to minimise the amount of sunlight reflected by them during the night. However, in a recent photograph showing many of the satellites stacked up and ready for launch, they did not appear to have been painted black.

Another problem is the space they take up. “The space up there is finite, and the presence of space debris – used rocket stages, broken satellites, broken off satellite parts – already poses a certain threat to satellites” Mentel says. “Adding 12,000 satellites within a few hundred kilometers of height to each other, will dramatically exacerbate the problem: they basically will weave a web of satellites around the planet, each one endangering other satellites in the altitude and incoming spacecraft.”

Recently, the European Southern Observatory had to manoeuvre their satellite to avoid a collision with a Starlink satellite. This is something that was rare until now, says Mentel.

It’s not only research astronomers who will be impacted by the influx of satellites, either. In the future, it might become more common to see satellites in the night sky than stars. “Unless some way can be found to reduce their effects,” says Blanchflower, “I foresee problems for all night sky viewers.”

Source: wired.co.uk