Darkened SpaceX Satellites Can Still Disrupt Astronomy, New Research Suggests

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Darkened SpaceX Satellites Can Still Disrupt Astronomy, New Research Suggests

“SpaceX’s attempt to reduce the reflectivity of Starlink satellites is working, but not to the degree required by astronomers,” reports Gizmodo:
Starlink satellites with an anti-reflective coating are half as bright as the standard version, according to research published in The Astrophysical Journal. It’s an improvement, but still not good enough, according to the team, led by astronomer Takashi Horiuchi from the National Astronomical Observatory in Japan. These “DarkSats,” as they’re called, also continue to cause problems at other wavelengths of light [and] were included in a batch of satellites launched by SpaceX on January 7, 2020. The new study aimed to evaluate the effectiveness of that dark coating…

The scientists found that the “albedo of DarkSat is about a half of that of STARLINK-1113,” as they wrote in their paper. That’s a decent improvement in the visual spectrum, but still not great. What’s more, problems persist at other wavelengths. “The darkening paint on DarkSat certainly halves reflection of sunlight compared to the ordinary Starlink satellites, but [the constellation’s] negative impact on astronomical observations still remains,” Horiuchi told Physics World. He said the mitigating effect is “good in the UV/optical region” of the spectrum, but “the black coating raises the surface temperature of DarkSat and affects intermediate infrared observations.”

A third version of Starlink is supposed to be even dimmer. Called “VisorSats,” they feature a sun visor that will “dim the satellites once they reach their operational altitude,” according to Sky and Telescope. SpaceX launched some VisorSats last year, but the degree to which their albedo is lessened compared to the original version is still not known, or if these versions will exhibit elevated surface temperatures.

Horiuchi told Physics World that SpaceX should seriously consider lifting the altitude of the Starlink constellation to further reduce the brightness of these objects.

. The article ends with a quote from an astronomer at Harvard-Smithsonian Center for Astrophysics and an expert on satellites. He’d told Gizmodo’s reporter back in January of 2020 that “SpaceX is making a good-faith effort to fix the problem,” and that he believes the company “can get the satellites fainter than what the naked eye can see.”

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