What The Heck Is Starlink? And What Is DarkSat?

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Originally published on EV Annex.
By Charles Morris

Starlink is another of Elon Musk’s brilliant ideas (some astronomers say it’s a bit too brilliant, as we shall see) — a constellation of thousands of small satellites in low Earth orbit that will provide internet access across the globe. The idea is to deliver connectivity to remote areas that currently have little or none, and to provide some much-needed competition to the near-monopolies currently operated by telecom and cable companies. Someday, Starlink could also provide communications links to colonies on the Moon and Mars.

Will Tesla vehicles be able to connect via Starlink? Back in 2018, some speculated that Teslas would soon be outfitted with Starlink receptors to provide fast and reliable in-car connectivity, and perhaps even to act as local Wi-Fi hotspots. However, in January 2020, in an interview with iGadgetPro, Elon Musk poured cool water on the idea. “It’s something that could happen in coming years, but there’s no plans to do it this year,” he said. “The antenna … is about the size of a medium pizza. You could put it on a car, but I think it’s more bandwidth than you really need. [Never underestimate our hunger for more bandwidth!] I think in most parts of the world, we’ll just use [5G cellular connectivity], but if you’re out in the countryside and there’s not good cell connectivity, then you could connect with a Starlink antenna.”

Deployment of Starlink has been proceeding at rocket speed. In April, SpaceX launched 60 more satellites (and by the way, aced a landing of the booster rocket on a drone ship in the Atlantic Ocean). This was the seventh batch launched, and it brought the total number of satellites now in orbit to 422 (eventually, they could number as many as 42,000). Musk has said that Starlink could begin to roll out minimal internet connectivity with 400 satellites, but at least 800 will be needed to reach moderate coverage. More launches are scheduled, and service could begin as early as this year.

Ringing the planet with so many satellites could have unintended consequences: as Matt Williams reports in Universe Today, some astronomers are afraid that the new constellation (and other similar networks planned by OneWeb, Amazon, and Telesat) could interfere with their work.

The Royal Astronomical Society noted that, although “the satellites will be relatively faint most of the time,” they are expected to exhibit “frequent reflective flaring, where transient alignment with sunlight leads to temporary surges in brightness.”

“Increasing the number of satellites so significantly presents a challenge to ground-based astronomy,” says the RAS. “The deployed networks could make it much harder to obtain images of the sky without the streaks associated with satellites, and thus compromise astronomical research.”

The International Astronomical Union raised similar concerns: “Although most of these reflections may be so faint that they are hard to pick out with the naked eye, they can be detrimental to the sensitive capabilities of large ground-based astronomical telescopes. Secondly, despite notable efforts to avoid interfering with radio astronomy frequencies, aggregate radio signals emitted from the satellite constellations can still threaten astronomical observations at radio wavelengths.”

At first, Elon Musk seemed to be dismissive of astronomers’ worries. In May 2019, when the first group of satellites was launched, he tweeted: “There are already 4900 satellites in orbit, which people notice ~0% of the time. Starlink won’t be seen by anyone unless looking very carefully & will have ~0% impact on advancements in astronomy.”

Since that time, as Mr. Williams writes, Musk and SpaceX have taken the issues more seriously, and have collaborated with the American Astronomical Society, the National Radio Astronomy Observatory, and the Vera C. Rubin Observatory to develop a comprehensive plan to address them.

“We have increased our understanding of the community as a whole through regular calls with a working group of astronomers during which we discuss technical details, provide updates, and work on how we can protect astronomical observations moving forward,” writes SpaceX. “The Vera C. Rubin Observatory was repeatedly flagged as the most difficult case to solve, so we’ve spent the last few months working very closely with a technical team there to do just that. Among other useful thoughts and discussions, the Vera Rubin team has provided a target brightness reduction that we are using to guide our engineering efforts as we iterate on brightness solutions.”

In April, Elon Musk took part in a presentation made during the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020). As part of the Optical Interference from Satellite Constellations Meeting, he explained how SpaceX plans to minimize light pollution from Starlink satellites.

The company is testing an experimental satellite called DarkSat, which uses a darkened phased array and parabolic antennas to reduce brightness by around 55%. However, satellites that are dark in the visual spectrum can still shine brightly in infrared. To counter this, SpaceX plans to add visor-like coverings to its parabolic antennas to reduce the amount of light they reflect. The company plans to test the first VisorSat prototype this month, and says that by June, all future satellites will have a visor.

SpaceX will also change the way its satellites move into on-station orbit. When satellites orbit the Earth, they periodically catch and reflect light from the Sun, especially during “orbit raise,” when they fire their thrusters to counter orbital decay. SpaceX is testing a “knife-edge” maneuver, which rolls the satellite so that it is on the same plane as the Sun, reducing the surface area exposed to sunlight, and thus the amount of light reflected.

As the New York Times reports, scientists can’t say yet whether these measures will be fully effective, but most seem to see them as a step in the right direction.

Patrick Seitzer, a professor of astronomy at the University of Michigan, is hopeful that the changes will make the satellites invisible to the naked eye — a huge relief to professional and amateur astronomers, as well as people who just love gazing at the night sky. “The really good news is how cooperative and how aggressive SpaceX has been in trying to fix this problem,” Dr. Seitzer said. “It should be the standard for all future spacecraft construction.”

Without the corrective measures, Starlink “would have been a fundamental change to our human experience of the night,” astronomer Tyler Nordgren told the Times. “That bullet may have been dodged.”

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