SpaceX’s attempt to reduce the reflectivity of Starlink satellites is working, but not to the degree required by astronomers.
Second, Starlink satellites with an anti-reflective coating are half as bright as the standard version. research published in The Astrophysical Journal. According to the team, led by astronomer Takashi Horiuchi of the National Astronomical Observatory of Japan, it is an improvement, but still not good enough. These “DarkSats“As they are called, they also continue to cause problems at other wavelengths of light.
Launched in May 2019, the initial batch of 60 Starlink satellites caused concern that the large constellations of low-orbiting satellites on Earth would interfere with astronomical observations. And in fact, that seemed to be the case, with Starlink satellites photobombing for a long time.exhibition plans of nearby galaxies i quotation marks, for example. Alert on the problem, astronomers described different ways in which SpaceX satellites can confuse scientific research, including operation from the nearby Vera C. Rubin Observatory in Chile.
The first batch of orbiting Starlink satellites is brighter than 99% of objects in low Earth orbit. This is a huge concern, given Elon Musk’s desire to launch more than 12,000 Starlink satellites and possibly up to 42,000. Starlink’s goal is to provide broadband internet to customers around the world.
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Discouraged, comments made by the CEO of SpaceX in March 2020 seemed incongruous with the emerging reality, in which Musk claimed that Starlink “will not cause any impact on astronomical discoveries, zero.” Encouraging, however, he also said that SpaceX “would take corrective action if it is above zero.” The company has responded by deploying some DarkSats, in which Starlink satellites received a darker coating to reduce albedo or reflectivity. These DarkSats, known as the Starlink-1130 version, were included in a batch of satellites launched by SpaceX on January 7, 2020. The new study aimed to: evaluate the effectiveness of this dark coating.
To do so, Horiuchi and his colleagues observed the satellites using the Murikabushi telescope at the Ishigakijima Astronomical Observatory.. The team watched the DarkSats along with the original version, known as Starlink-1113, at multiple wavelengths of light. This telescope allows scientists make simultaneous observations on the nearby green, red, and infrared bands. The team also compared the brightness of reflective objects with reference stars. In total, the team made four different observations from April to June 2020.
The scientists found that the “albedo of DarkSat is about half that of STARLINK-1113,” as they wrote in their article. That’s a decent improvement in the visual spectrum, but it’s still not fantastic. What’s more, problems persist in other wavelengths.
“DarkSat’s dark paint certainly halves the reflection of sunlight compared to ordinary Starlink satellites, but [the constellation’s] a negative impact on astronomical observations is still maintained, “Horiuchi said he said Physics World Cup. He said the mitigating effect is “good in the optical and ultraviolet 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 weaker. Called “VisorSats”, they feature a solar visor that “will attenuate the satellites once they reach their operating altitude.” seconds in Sky and Telescope. SpaceX launched some VisorSats last year, but it is not yet known the degree of reduction of its albedo compared to the original version or whether these versions will have high surface temperatures.
Horiuchi told Physics World that SpaceX should seriously consider raising the altitude of the constellation Starlink to further reduce the brightness of these objects. Star bonds currently orbit at heights reaching 340 miles (547 km). Compare that to OneWeb, a competitor to SpaceX, of whom constellation of satellites it will orbit 1,200 km (750 miles) and, as a result, will be much darker.
In January 2020, Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics and a satellite expert, he said me that “SpaceX is making a good faith effort to fix the problem,” and that he believes the company “can make satellites weaker than it can see with the naked eye.”
For the sake of astronomers around the world, I hope you are right on both fronts.