SpaceX’s Counter-reflective darker Starlink Satellites are better, but only slightly, Astronomers claim


In recent launches, SpaceX has revealed special Starlink satellites with an anti-reflective coating. The company launched the first set of 60 small satellites on 24th May 2019. Among these was the dark-coated satellite, the DarkSat model. The coating reduces reflectivity. It counteracts the sun rays that are reflected on the satellite’s surface to reduce the brightness. A bright artificial satellite leaves white streaks that destroy picture quality when they pass above a ground-based telescope. This has become a major concern for astronomers. It obscures clear observation of other celestial objects such as asteroids.

According to Takachi Horiuchi and his colleagues at Japan’s National Astronomical Observatory, the coating only reduces the reflectivity by half. Furthermore, this reduction is effective up to certain wavelengths, beyond which it becomes ineffective. Horiuchi added that the reduction works in the UV/optical area of the spectrum. However, it increases DarkSat’s surface temperature. Intermediate infrared measurements are influenced by this. The satellites were launched by SpaceX to establish a global broadband network by linking the satellites to ground-based receivers. This will provide reliable internet access to people throughout the world.

The new satellites have raised concerns among astronomers and physicists. They appear to be brighter than 99% of previous artificial objects visible to the naked eye. It is in response to these concerns that SpaceX developed the DarkSat model. In the most recent satellite launch in 2020, SpaceX revealed a special Starlink Satellite with dark-coating. Horiuchi and his IAO counterparts have observed both the standard STARLINK-1113 version and the darker version. This is in a bid to study the comparisons between the two. They used the Murikabushi telescope’s MITsuME system. It is a multicolor imaging telescope that simultaneously uses three-color CCD cameras.

IAO results showed that negative impacts of the satellites remained despite the dark coating. “The darkening paint on DarkSat certainly halves reflection of sunlight compared to the ordinary Starlink satellites, but the negative impact of the constellation on astronomical observation remains,” said Horiuchi. In August 2020, Starlink launched another model known as Visorsat. This satellite has a deployable sun shield that reduces the brightness of the satellites. It is anticipated to be more productive compared to its predecessor, the DarkSat.

Horiuchi thinks that raising the orbital altitude of the satellites could make the Visorsat darker. He adds that compared to Starlink Satellites, OneWeb satellites are darker because they are located at an orbital altitude of 1200km.OneWeb is a small European satellite launched in 2019 to provide internet services globally. Astronomers hope that Visorsat will be darker than previous Starlink’s satellites. They recommend that researchers, the public, and SpaceX should work together to discover the effects of such missions on ground-based observations. They should also collaborate on coming up with ways of alleviating these negative effects.

“We think it is important to discuss with the astronomical community of ground-based observations and proceed with the necessary verification when such a problem occurs or is expected,” says Horiuchi. “Dark skies with beautiful stars and nebulae are the treasure for all people in the world. Astronomers need to communicate with the public towards keeping the shared treasure,” he added.
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