Astronomers reiterate concerns over Starlink satellite brightness

(ORDO NEWS) — As SpaceX prepares for yet another launch of Starlink satellites, astronomers are concerned that the company may backtrack on its efforts to dim these satellites.

The Falcon 9 rocket lifted off on June 17 from Kennedy Space Center Launch Complex 39A and placed 53 Starlink satellites into orbit. This launch brings the total number of Starlink satellites launched to over 2,700, with over 2,450 in orbit.

These satellites, like several hundred previous ones, are version V1.5 of the Starlink project. These satellites lack the canopies that SpaceX installed on the satellites in 2020 to keep sunlight from hitting the reflective surfaces of the satellites, thereby reducing their brightness when viewed from the ground. Visors are not compatible with laser inter-satellite links installed on new V1.5 satellites.

Astronomers say they have noticed that the V1.5 satellites are brighter than earlier Starlink “VisorSat” satellites.

During a discussion at the 240th meeting of the American Astronomical Society (AAS) on June 13, Pat Seitzer, an astronomer at the University of Michigan who studies satellite brightness, said that VisorSats have a magnitude of 6.5.

This brightness was close to the recommendation from astronomers that they should be no brighter than 7th magnitude to minimize interference with astronomical observations.

However, V1.5 Starlink satellites are about half a magnitude brighter than VisorSat. “As a result, we are going in the opposite direction,” he said. “We should talk to SpaceX and find out what their plans are.”

Of great concern is the second generation of Starlink satellites. These satellites, intended to be launched on SpaceX’s Starship, will be significantly larger and therefore potentially brighter. “No one knows what the brightness will be,” Seitzer said. “Hopefully they can build on all the lessons learned so they don’t end up being four times brighter than they are now.”

Last month, SpaceX chief engineer David Goldstein, speaking at the Federation of Astronomical Societies, said the company was working on new technologies to dim second-generation Starlink satellites. This includes the development of a “dielectric mirror sticker” to be placed on satellites to reflect sunlight.

According to him, this approach will make the satellites 10 times dimmer than if they were covered with vantablack paint, one of the darkest paints. This ink also wears out in the space environment and has poor thermal performance.

Other panellists at the AAS event acknowledged that SpaceX and other companies are making efforts to reduce the brightness of their satellites.

“SpaceX has invested a lot of money and human resources in solving this problem,” said Connie Walker, director of the International Astronomical Union’s Center for the Protection of Dark and Quiet Skies from Satellite Interference. “They are again trying to create a strategy to reduce the brightness of their satellites.”

In addition to technical solutions, astronomers are also considering political approaches. Julie Davis, AAS Public Policy Scientist, said politicians are not very knowledgeable about the issue and that astronomers have to balance their concerns against the demand for broadband that satellites can offer.

“We have to be clear about what our problem is. We’re not against the internet, we just want the satellites not to be super-reflective.”


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