Satellite constellations could hinder astronomical research, scientists warn

SpaceX has so far sent a few hundred of Starlink broadband satellites into orbit, but the aerospace company has plans for a constellation featuring thousands of small satellites -- and this has researchers concerned.

A report published Tuesday by the Satellite Constellations 1 workshop, an effort organized by the National Science Foundation and the American Astronomical Society, says the constellation could be bad news for astronomers and their research.

"The main takeaway from our findings is that no combination of mitigations will totally eliminate the impacts of satellite constellations on ground-based astronomy," Connie Walker, an astronomer with NSF's NOIRLab and co-chair of the SATCON1 workshop, told reporters during a virtual press conference on Tuesday.

For decades, astronomers have been trying to escape light pollution. As a result, the newest generation of observatories has been pushed to increasingly remote, and sparsely populated, locales.

Over the next decade, a variety of technological advancements in the field of astronomy -- cameras with wide fields of view on large optical-infrared telescopes -- are scheduled to come online. When they do, astronomers will face a new source of light pollution.

Starlink's first 60 satellites, launched in 2019, were much brighter than many anticipated. The satellites could easily be seen from Earth's surface, leading researchers to worry about the impacts as Starlink grows -- and as other planned satellite constellations come online.

To gauge the potential damage and develop possible solutions to the problem of space-based light pollution, scientists at NSF and AAS assembled a working group of experts from the global astronomical community.

According to the SATCON1 workshop's report, the first of two planned papers, the impacts of Starlink and other large satellite constellations on astronomical research and the human experience of the night sky could range from "negligible" to "extreme."

Currently, low-Earth orbit satellite constellations are small, with SpaceX's 422 satellites leading the way. But other companies, including Telesat and Amazon, have plans to build out constellations featuring hundreds, perhaps thousands, of satellites.

"We know that there will be more in the future, and even with mitigations that we will employ over time, we know some of them will continue to land in our data," said Lori Allen, an astronomer with NSF's NOIRLab. "So we'd like to understand the impacts of those intrusions now."

By purposefully pointing telescopes at low-Earth orbit satellites, researchers were able to get a better sense of these reflective hunks of metal's impacts on astronomical research. Researchers then used data to model the effects of satellite constellations as they continue to grow.

"We modeled the visibility for the three largest of the constellations that we know of," Patrick Seitzer, astronomer with the University of Michigan.

Their analysis suggests low-Earth orbit satellite constellations will most likely affect astronomical investigations that require twilight observations, including searches for Earth-threatening asteroids and comets, outer solar system objects and the visible signatures of gravitational-wave sources.

"One of things we wanted to address was whether there are some satellite constellation configurations that are more challenging than others for ground-based astronomical observations," Seitzer said. "The higher altitude constellations are more challenging for astronomy."

Models showed that for every 30 seconds of exposure, observatories will pick up at least one satellite glare, no matter the time of day or year. These glares make it harder for astronomers to survey large astronomical datasets for unique patterns and the signatures of interesting phenomena.

The latest report also outlined six potential mitigation strategies, the first of which calls on the aerospace industry to "launch fewer or no LEOsats."

"However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact," the report's authors wrote.

More realistically, researchers called on SpaceX and other companies to design darker, less reflective satellites, and to work with the astronomical community to deploy them in the least intrusive way possible. According to the report, future satellites can be positioned lower in the sky and oriented to reflect less sunlight.

The astronomers also identified ways observatories can anticipate and account for satellite interference.

The report's authors suggest scientists develop new machine-learning algorithms to remove or mask satellite trails in astronomical images. Improved computer models could also help astronomers more accurately calculate satellite trajectories and position telescopes to avoid their trails.

Workshop participants said their second report will focus on related policy and regulation issues, and is expected to be published in mid-2021.

Related Links
Research Report: Report Offers Roadmap to Mitigate Effects of Large Satellite Constellations on Astronomy
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