How satellite swarms are putting astronomy at jeopardy.

SpaceX, a Hawthorne, California-based aerospace corporation, launched its first set of Starlink Internet-communication satellites three years ago, causing worry among astronomers about the streaks the spacecraft leave in images of the night sky. Since then, more than 2,300 Starlink spacecraft have been launched, accounting for roughly half of all active satellites.

In dealing with the onslaught, scientists have made some progress. The International Astronomical Union (IAU), for example, will launch a website with tools to help telescope operators estimate satellite placements so that they can point their instruments elsewhere in the coming days.

However, evidence is mounting that these satellite'megaconstellations' will have a significant impact on astronomical observatories and other skywatchers around the world. Satellite providers have yet to come up with a solution. SpaceX attempted to solve the problem by adding sun-blocking coverings to their Starlinks, which made them seem darker in the night sky. Nature, on the other hand, has discovered that the firm has stopped doing so.

Meredith Rawls, an astronomer at the University of Washington in Seattle, adds, "This is an unsustainable trajectory." "For the time being, our science is in good shape. But when will we miss a breakthrough?

The toll of megaconstellations-

Astronomers have gone from fretting over the satellites photobombing scientific observations to coordinating a global reaction since the first Starlinks launched. Following a series of international conferences in 2020 and 2021, the IAU established a Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference. Its soon-to-be-launched website will act as a collaborative hub for astronomers, legislators, satellite operators, and the general public to work on solutions to reduce the harmful consequences of satellites blazing over the sky.

According to a recent study, future satellite constellations would be most visible in latitudes about 50 degrees south and 50 degrees north, where many European and Canadian astronomy facilities are located2. Bright spots will swarm over the skies all night long at certain latitudes during the summer solstice if SpaceX and other businesses launch the 65,000 satellites they have suggested, according to the study. Around dawn and sunset, one out of every fourteen stars visible to the naked eye will be a satellite.

Samantha Lawler, an astronomer at the University of Regina in Canada, who led the research, describes the findings as "horrifying."

Astronomical observatories that investigate large swaths of the sky rather than single celestial objects would be the most impacted. The Zwicky Transient Facility (ZTF), which uses a 1.2-metre telescope on Palomar Mountain, California, to survey large swaths of the sky, found satellite streaks in 18 percent of its photographs acquired after twilight in August 20213. According to main author Przemek Mróz, an astronomer at the University of Warsaw, this number has risen as the number of satellites has grown. He observed that satellite streaks damaged roughly 20–25 percent of twilight photographs in a preliminary review of ZTF data from April 2022.

Mróz claims that satellite streaks haven't harmed many of the ZTF's observations so far, in part because its image-processing technologies can detect and conceal satellite traces. Other observatories, however, confront more difficult difficulties, such as the US-funded Vera C. It will be particularly vulnerable to satellite streaks following through its photographs because it will shoot the entire visible sky every three days. Rawls and other astronomers are developing methods to locate and remove satellite streaks from data as a way to mitigate the damage. Fixing the data, however, requires a lot of time and effort. Rawls says, "It's definitely eating my career."

A busy sky-

The increased number of satellites also poses a threat to radio astronomy, as well as increasing the amount of space debris. Other, more widespread effects could have a global impact: satellites contribute to a background glow in the sky, which can cause animals that rely on celestial navigation to become disoriented. Satellite streaks can potentially disrupt human knowing systems, such as Indigenous knowledge systems that rely on black sky information to indicate significant events throughout the year.

The growing hazard of satellite constellations, according to Karlie Noon, a PhD candidate in astronomy and an Indigenous research associate at the Australian National University in Canberra, adds to other night sky degradations such as light pollution. She claims that "our skies are being colonised in the same way that our lands have been colonised." "This isn't just a problem for Native Americans." She claims tha

Some satellite operators are attempting to resolve the issue. SpaceX, OneWeb in London, and Amazon's Project Kuiper in Seattle, Washington, have met with the IAU and national astronomical associations on a regular basis to discuss how to mitigate the satellites' impact. SpaceX has experimented with various methods for dimming their Starlinks, including the use of sunshades. The sunshades indeed limit the brightness of the satellites5, but they don't appear to be on the latest generation of Starlinks. Those satellites, which have been in orbit since September, interact with one another via lasers rather than radio, and the sunshades interfere with those communications.

It's still unclear how well that would function. According to an unpublished investigation of 102 observations of the brightness of Starlinks over time, the new generation appears to be brighter than those with sunshades. According to Anthony Mallama, a retired astronomer in Bowie, Maryland, who conducted the investigation, they are not as brilliant as the original Starlinks without sunshades.

Meanwhile, OneWeb has launched 428 of the 648 satellites that were originally planned. They orbit at a far higher height than the Starlinks, at 1,200 kilometres against 550 kilometres. Satellites are normally fainter than Starlinks due to their greater distance, but their brightness can vary significantly depending on how they catch and reflect sunlight.

According to Jeremy Tregloan-Reed, an astronomer at the University of Atacama in Copiapó, Chile, a preliminary examination of 50 OneWeb satellites in 2021 found that over half of them were a little brighter above the'safe' level stipulated by astronomers. Maurizio Vanotti, OneWeb's vice-president of space infrastructure development and partnerships, told the FAS webinar that the company is committed to reducing the visibility of its satellites.

Amazon's Project Kuiper, which would add over 3,200 satellites to the sky, expects to launch its first two prototypes by the end of the year. One of them will include a sunshade so that the corporation can compare how well it can decrease the light of the satellites. Although the IAU and other astronomical groups have lobbied the UN to recognise the problem, there are no laws governing how bright satellites should look in the night sky. At a conference of the UN's Committee on the Peaceful Uses of Outer Space, which opens on June 1 in Vienna, representatives from numerous countries will discuss how to preserve the sky.