the sky was filled with satellites

In December 2020, a group of astronomers documented a burst of highly energetic light in one of the most distant galaxies ever observed. But less than a year later, the claims in that document had been left in limbo. Other scientists said it had simply been a passing satellite.

“I was somewhat sad that the gamma ray burst turned out to be nothing more than an artificial satellite,” said Krzysztof Kaminski, an astronomer at the Polish Astronomical Observatory Institute, who specified that he had matched the position, timing and brightness of the discovery. with one of the space objects in orbit.

Linhua Jiang, an astronomer at Peking University in Beijing who coordinated the original detection, reported that His team had been permanently focused on the process and added that the probability of a satellite passing just facing the distant galaxy at the exact moment was minuscule at best.

Most likely, this discussion will not be the last among scientists about whether a passing satellite can be mistaken for an astronomical discovery.

Earth’s orbits are filling up with satellites at an astonishing rate. There are already more than 9,000 orbiting the planet and more than 5,000 belong to Starlink, the constellation built by the SpaceX corporation to provide internet service to Earth. They will be joined by thousands more satellites from other companies and countries in the coming decades. The more there are, the greater their interference in Earth-based astronomy’s ability to answer questions about the Cosmos and humanity’s place in it.

SpaceX did not respond to this reporter’s requests for comment. But astronomers on land say they are not willing to cede the night skies to trains of newly orbiting satellites..

To address growing obstacles to their observations they are combining new and old technologies with remarkable ingenuity. They are also working with industry to find solutions to obscure satellite vehicles. And they’re trying to persuade government regulators to pay more attention to the growing satellite industry..

The strategies are working, for now. But researchers’ quest to preserve the power of astronomy faces fundamental disadvantages. Building new telescopes can take decadeswhile dozens of new satellites can be added to the night skies every week.

“The time scales are very different,” says Meredith Rawls, a research scientist at the Vera C. Rubin Observatory, equipped with a powerful telescope financed by the United States that will come into operation in 2025 in Chile. “The speed at which the satellite industry is designing and launching its hardware is incredibly fast compared to that of Astronomy.”

To photograph the night sky, those who operated telescopes captured images on glass plates for more than a century.

More powerful ground-based observatories take decades to build, and many were designed with 20th-century levels of imaging techniques in mind.

That includes the Vera Rubin Observatory, named after an astronomer who played a central role in the discovery of dark matter. Its mission is mainly to detect planet-destroying asteroids and study the relationship between dark matter and dark energy.

The Vera Rubin telescope, by capturing a wide field of sky, is estimated to peer into mysteries of objects 20 million times fainter than what the human eye can see.

But as satellites invade the skies, astronomers who planned to rely on the Rubin telescope to make scientific discoveries are becoming more concerned..

“The purpose of the Rubin is to open a new window to the Universe to find things that we don’t even know yet to look for,” explained Meredith Rawls. “And if instead we’re going to look through the equivalent of a windshield full of bugs, who knows what we’re not going to see.”

Some telescopes using special detectors study such a narrow patch of sky that satellites may not interfere with them.

But the very vast view of the Rubin telescope poses unique problems. One study showed that, during certain times of the night, Almost every image taken will be spoiled by no less than one, if not many satellites, sealing their trail hundreds of pixels wide.

Dr. Rawls presented two strategies to deal with this threat to the telescope: dodge and correct. If astronomers know the trajectories of satellites in advance, technology can anticipate and “dodge” them. temporarily reorienting the telescope.

“We use an algorithm to determine where the telescope is pointing,” Rawls said. “The algorithm is brilliant; can take into account many different weights”he added. Even avoid swarms of satellites.

Rawls said dodging should remove about half of the scratches on Vera Rubin’s telescope, depending on how many satellites are in orbit.

For the correction strategy, The astronomer commented that scientists are developing algorithms to eliminate satellites from the data, a much more challenging task but one that disturbs the observations less.

Since software solutions are all imperfect and complex, some experts suggested that telescope builders think about changing their hardware.

Darren DePoy, an astronomer at Texas A&M University, used one type of detector, the CCD, but in 2018 he began testing a much more comprehensive one, the CMOS, which is the same type that is probably in the camera of a current smartphone.

“Although the physical order is very similar, the way the signal is emitted is a little different,” DePoy said. “With CMOS you can read all the pixels simultaneously while, to read each pixel sequentially in a CCD detector, you have to wait.”

As an example, DePoy said that while a CCD might require about 10 seconds to photograph a faint galaxy, the CMOS detector would take about 10 milliseconds. That is, it is 1,000 times faster. Because of this feature, by taking numerous quick exposures, astronomers can remove frames smeared by satellites or aircraft and then average the rest to create a flawless final image.

DePoy also said that small CMOS detectors are already popular among amateur astronomers who own hobby telescopes.

Sin embargo, cPurchasing and integrating large CMOS detectors, such as those used in science, remains expensive compared to using existing CCD detectors, says Richard Green, an astronomer at the University of Arizona and acting director of the Center for the Protection of Dark and Clear Skies from Satellite Constellation Interference, an organization that sponsors research on the subject.

Meredith Rawls highlighted that problem when asked if the Rubin telescope could use CMOS technology. “The idea of ​​changing now is just ridiculous,” she responded. “It’s like you’re building a house, about to put in the windows, and someone says, ‘Hey, shouldn’t we use a different foundation?’” she added.

So far the government has not acted to force satellite operators to help pay for telescope upgrades.. But some companies have been trying to address aspects of the problem.

When SpaceX founder Elon Musk came under fire in 2019 following the launch of the first Starlink satellites, he posted on Twitter that he had “sent a memo” to engineers, asking them to reduce sunlight reflections from the company’s orbiters.

SpaceX installed screens over its satellites as curtains, an idea that was quickly discarded because the screens not only managed to obscure the satellites but also blocked links for its satellites to communicate with each other.

The company’s most recent attempt involved a dielectric film coating. Contrary to expectations, this made the satellites shine brighter. But instead of reflecting sunlight back to the Earth’s surface, The material returns it to the space and attenuates the intensity of any scratches. SpaceX announced that it would share these coatings with other satellite manufacturers.

During the crucial twilight hours when many astronomical observations take place, SpaceX also began rotating its satellites so that they point the solar panels away from Earth. To compensate for the loss of solar energy, the size of the panels increased, an additional expense.

Initial data indicate that the interventions may be working. In a study that has yet to be peer-reviewed, a team of astronomers describes that newer Starlink satellites appear darker due to reduced reflection of sunlight from the surface. Will that be enough for now?

Translation: Román García Azcárate.