What would you prefer: Satellite-streamed cat GIFs – or a decent early warning of an asteroid apocalypse?

Earth's crowded orbit may obscure vital readings from space, boffins warn

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Swarms of small communications satellites saturating space may make it more difficult to observe and track potentially hazardous asteroids zooming toward Earth, astronomers have warned.

A report [PDF] out this week compiled by the Satellite Constellations 1 (SATCON1) committee outlined the repercussions of the growing number of metallic birds in low-Earth orbit (LEO) on astronomy.

The high reflectivity of these satellites ruins images of the night sky, as far-away objects are covered by bright streaks leftover from the passage of the satellites. The effect was noticed as soon as SpaceX flung its first constellation of 60 internet-relaying satellites into the heavens last year. That number has steadily risen to 655 as of this month. And with tens of thousands more on the way, the astronomical community is racing to come up with solutions to minimize their impact on science.

The circled streak in the center of this image is asteroid 2020 QG, which came closer to Earth than any other nonimpacting asteroid on record. It was detected by the Zwicky Transient Facility on Sunday, Aug. 16 at 12:08 a.m. EDT (Saturday, Aug. 15 at 9:08 p.m. PDT). Credits: ZTF/Caltech Optical Observatories

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The satellites appear brightest at twilight, and, unfortunately, that’s the best time to inspect near-Earth objects. Detecting and monitoring asteroids is time-sensitive; there’s a limited window to measure important properties such as their size and orbit to predict where they are headed and what effect they will have if they reach our world. If a satellite blocks the view of a space rock, astronomers could lose sight of their target and be unable to accurately warn us of an impending collision.

“Asteroids and comets have frequently impacted Earth in the past and will do so in the future, over long intervals with dramatic consequences, if not discovered and mitigated,” the report said. The American Astronomical Society, which jointly organized the study along with the US National Science Foundation, added: "LEO satellites disproportionately affect science programs that require twilight observations, such as searches for Earth-threatening asteroids and comets."

Other objects, particularly exoplanets and stars orbiting directly behind the trail of these pesky birds, will also be tricky to find. The most successful way of detecting exoplanets, known as the transit method, involves measuring the periodic brightness of host stars, a winking effect caused by planets moving in from of them. The reflected light from satellites, however, will drown out the glow emitted by these far-away suns, and, in turn, their planets won’t be seen, either.

“Some of the most severely affected targets will be the M dwarfs, since cooler stars at a fixed distance will suffer larger relative effects. With the full constellations deployed, it will be impossible to detect super-Earth planets around M dwarf stars crossed by satellites,” the SATCON1 committee said.

But that’s not all: these massive constellations of telecoms satellites may spoil astronomical surveys probing for dark energy or gravitational waves. Over time, even amateur skywatchers will have to get used to them zipping across their field of vision as they look through their telescopes.

It is impossible to calculate the risk or the impact of losing such opportunities to discover the unexpected

The greatest loss, assuming there are no killer asteroids, will be if the internet-relaying satellites impact the ability to find and observe completely new types of objects and processes that have yet to be discovered. “It is impossible to calculate the risk or the impact of losing such opportunities to discover the unexpected without knowing what we’re missing. But some phenomena will surely go undiscovered as a result of significant interference from LEO satellites,” the report cautioned.

There are a number of steps the committee recommended to minimize the negative effects of these satellites. Companies can work towards making their birds less reflective or promising to not launch them above 600 kilometres – a distance where they become visible all night.

Observatories will have to shuffle their schedules around to monitor the sky at times when interference is minimal. Astronomers will have to develop new techniques that remove the extra brightness or annoying trails of light produced from the satellites in images.

“The impacts of large constellations of LEO satellites on astronomical research programs and the human experience of the night sky are estimated to range from negligible to extreme, depending on factors including the scientific or other goals of the observation, the etendue of the facility, the observing strategy and ability to avoid satellites, and the ability to mask or remove satellite trails in data,” it concluded. ®

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