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A SpaceX Falcon 9 rocket takes off from Cape Canaveral Air Force Station with 60 Starlink satellites on November 11, 2019 in Cape Canaveral, Florida. The Starlink constellation will eventually consist of thousands of satellites designed to provide worldwide high-speed Internet service.
Paul Hennessy | NurPhoto | fake pictures
Rocket builder SpaceX is fast becoming the world’s leading satellite operator, having launched 420 of its own satellites in the past year, with plans for thousands more.
However, the unprecedented scale of SpaceX’s satellite internet project, known as Starlink, has sparked a public outcry from astronomers around the world. The network represents SpaceX’s plan to build a network of approximately 12,000 small satellites to provide high-speed Internet to anywhere in the world.
Starlink satellites have appeared as bright streaks in images taken by telescopes, since SpaceX launched the first mission almost a year ago.
An image from the Arizona Lowell Observatory telescope shows streaks left by Starlink satellites after SpaceX’s first launch in May 2019.
Victoria Girgis / Lowell Observatory
The satellites are visible enough at times that an astronaut aboard the International Space Station even spotted Starlink earlier this month.
SpaceX in recent months has been busy addressing astronomers’ concerns directly. The American Astronomical Society (AAS) in December noted that “the response from our community was strong enough for SpaceX to communicate with AAS seeking to establish a line of communication.”
On Monday, SpaceX CEO Elon Musk and members of his Starlink division made a presentation to the National Academy of Sciences, Engineering and Medicine. The company’s leadership gave updates on the changes SpaceX has made to the design of its Starlink satellites, as well as changes to how satellites move in space, to help reduce glare and damage to astronomers’ images. .
“SpaceX is committed to making future satellite designs as dark as possible,” the company said in a press release on Tuesday about the presentation.
“We also strongly believe in the importance of a natural night sky for us all to enjoy, which is why we have been working with leading astronomers around the world to better understand the details of their observations and the engineering changes we can make to reduce satellites brightness, “added SpaceX.
“With the benefit of hindsight, the changes seem pretty simple,” Musk said during Monday’s presentation. “We will feel a bit silly in hindsight, since it’s not that difficult.”
The company emphasized that it continues to work with AAS to address the issue of Starlink astronomy, as well as with the Vera C. Rubin Observatory in Chile.
“The Vera C. Rubin Observatory was repeatedly singled out as the most difficult case to solve, which is why we have spent the past few months working closely with a technical team there to do just that,” SpaceX said. “Among other helpful thoughts and discussions, the Vera Rubin team has provided a target gloss reduction that we are using to guide our engineering efforts as we iterate on gloss solutions.”
The company is testing Starlink’s brightness solutions even as it continues to rapidly build the satellite “constellation”. The company said it has begun releasing “predictive data before launch at the request of astronomers,” to help them know when and where the satellites will be.
SpaceX told AAS in December that the company plans to have up to 1,584 Starlink satellites in space by the end of this year. Furthermore, with SpaceX currently launching a new Starlink mission approximately once a month, the company’s director of satellite policy, David Goldman, wrote in a letter to the FCC on Monday that the company “anticipates that before the end of 2020 it will begin to offer commercial service in the northern United States and southern Canada, and then will rapidly expand to near-global coverage of the populated world in 2021. “
That is why Starlink satellites appear as bright objects in the sky.
As Starlink satellites move across the sky, the reflection of sunlight at sunrise and sunset makes them especially visible from the ground.
“This happens because satellites are illuminated by the Sun, but people or telescopes on the ground are in the dark,” said SpaceX.
SpaceX’s goals to reduce Starlink brightness
The company outlined for astronomers its goals to reduce glare from satellites. While Starlink satellites are visible to the naked eye while in orbit, SpaceX said its first goal is for the spacecraft to be “generally invisible to the naked eye within a week of launch,” as well as “for almost all phases of their mission. “Their second goal is to minimize Starlink’s impact on astronomy,” darkening the satellites so they don’t saturate the observatory’s detectors. “
SpaceX noted that a major contributor to Starlink’s brightness “are the white diffuse phase array antennas at the bottom of the satellite, the white diffuse parabolic antennas on the sides (not shown below) and the white diffuse rear of the solar array. These surfaces are all white to keep temperatures down so the components don’t overheat. “
Until now you have experimented with a way to reduce shine. One of the satellites in a batch of 60 launched in January received a darkening treatment. Nicknamed “DarkSat,” the Starlink satellite reduced its brightness “by approximately 55%,” the company said.
Although the “DarkSat” approach reduced the brightness of the satellite, the dark surfaces get hot and can damage the satellites, while reflecting some light. Instead, SpaceX plans to launch a different method next month: “A visor solution.”
This design is nicknamed “VisorSat”. SpaceX said one of the Starlink satellites will have “a fold-out visor,” shown below, which is intended to “prevent sunlight from hitting the brightest parts of the spacecraft.” During launch, the visor is flat against the body of the satellite but, after deploying into orbit, the visor extends.
“The viewfinder prevents light from reflecting off the diffuse antennas by preventing light from reaching the antennas entirely,” said SpaceX. “This approach not only avoids thermal shocks from the surface darkening the antennas, but should also have a greater impact in reducing glare.”
The company appears confident in VisorSat’s design, as SpaceX said that by “June, all future Starlink satellites will have umbrellas.” Starlink satellites already in space without these design changes will darken in a few years.
SpaceX emphasized that, in general, “it will not be possible to create satellites that are invisible to the most advanced optical equipment on Earth.” But the company’s attempts to reduce Starlink’s brightness will help astronomers mitigate the damage to the images.
The company also hinted at a “next generation” Starlink satellite to be built to take advantage of the company’s massive Starship rocket, which SpaceX is now developing. SpaceX President Gwynne Shotwell said in October that Starship will “be able to take 400 satellites at once.” While the company did not specify what the next generation changes will be, SpaceX said those Starlink satellites “will be specifically designed to minimize glare while increasing the number of consumers it can serve with high-speed Internet access. “
A rocket from the SpaceX prototype spacecraft on the company’s test bed in Boca Chica, Texas.
SpaceX
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