Satellite Megaconstellations Are Now Threatening Telescopes in Space

Satellites swarming in low Earth orbit threaten space telescopes

TO Megan Bartels edited by Lee Billings

Today, the globe is surrounded by thousands of active satellites, each capable of photobombing astronomers' telescopes like an artificial star streaking across the night sky. Scientists working with ground-based observatories, such as the newest Vera K. Rubin Observatory, have long been concerned about this visual interference. satellites continue to multiplyspace-based telescopes, including everyone's favorite Hubble Space Telescopethey also begin to suffer.

And the problem will only get worse. If the companies follow through with their stated launch plans, there will be about 560,000 satellites in Earth's orbit by the late 2030s. Many of them will be members of megaconstellations—groups of hundreds or thousands of satellites that work toward some common goal, such as providing global broadband Internet from orbit. And according to new estimates published December 3 in Nature, at least one satellite from such swarms could appear in one of every three images taken by Hubble. Other observatories the researchers analyzed would see traces of these satellites in almost every single impact.

There is no hard limit at which satellite interference would make science impossible, but the light pollution created megaconstellations are already appearing in astronomical data and distracts people who are trying to explore the mysteries of space, says Alejandro Borlaff, an astrophysicist at NASA's Ames Research Center in California and co-author of the new study. “If we don't find a solution, it will only get worse and worse and worse,” he says.

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This is obvious, but Borlaff and his colleagues went deeper. They collected detailed information on the thousands of satellites the companies plan to launch, including information about the spacecraft themselves and their orbits.

The researchers then modeled what these satellites would look like to two currently operating space telescopes—Hubble and NASA's recently launched one. Spectrophotometer for the History of the Universe, the Age of Reionization and the Ice Explorer (SPERex). They also examined how satellites would affect observations from two planned space telescopes—China's Xuntian observatory, scheduled to launch in about a year, and the European Space Agency's Analysis of Resolved Remnants of Accreted Galaxies as a Key Instrument for Halo Studies (ARRAKIHS) mission, which could launch in the next decade.

All four observatories are very different, resulting in different vulnerabilities to satellite interference. For example, Xuntian must be in a fairly low orbit because it is intended to be deployed and upgraded by astronauts on China's Tiangong space station; this relatively low altitude means that the largest number of satellites pass between it and space. SPHEREx has the lowest resolution of the four, so each individual satellite affects more of its images. SPHEREx also sees in infrared light, which satellites can reflect even if the observatory is augmented to reduce their optical visibility. Overall, the analysis found that Chinese and European missions would be most affected by megaconstellations, with dozens of streaks appearing with each impact when there are 560,000 active satellites in orbit.

( James Webb Space Telescope and NASA's next major observatory, Rome Nancy Grace Space Telescopeboth are immune to such orbital interference—both operate nearly one million miles from Earth, in the opposite direction to the Sun.)

Even for telescopes closer to home, NASA is more optimistic about the challenges posed by megaconstellations. As for Hubble, an agency spokesman characterizes the streaks in the current images as “faint” and notes that while the number of satellite tracks will increase, “most of these streaks are easy to detect and remove using standard data processing techniques.” For SPHEREx, the telescope's operation requires its science targets to be viewed repeatedly over time, reducing the likelihood of satellites interfering with any individual observation of any given object, the spokesperson notes.

However, since the first launch of SpaceX's Starlink megaconstellation in 2019, astronomers have spoken out about the impact of the bright satellites on their hard-earned observations, especially those made with ground-based telescopes.

“Astronomers in all fields of astronomy are faced with a gradual deterioration in observing conditions due to satellite bands,” says Samantha Lawler, an astronomer at the University of Regina in Saskatchewan.

Ironically, one common proposal was to simply abandon ground-based observations and instead rely entirely on space telescopes, despite their high cost and near impossibility of upgrading them. “There are many reasons why this is a useless proposal, but this [study] really quantifies it,” Lawler says.

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