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Theodolite Thursday: Satellites Interfere With Astronomy

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Earth Satellites Image One
Image Credit: NOIRLab
NSF
AURA
P. Marenfeld
Science Magazine

“A report warns that fleets of new communication satellites in low-Earth orbit will spoil some astronomical observations, even if all known mitigation strategies are taken.”

Astronomers and the operators of new, thousands-strong […] low-orbiting satellites will have to work together to prevent them from having a devastating impact on ground-based observations of planets, stars and other celestial objects, says a [recent] report […]. Even then, there is no escaping some harm from the fleets of commercial orbiters.

“All optical and infrared observatories will be affected to some degree,” [stated] astronomer Anthony Tyson of the University of California, Davis, […] at a briefing on the report.

“No combination of mitigation will eliminate their impact,” added astronomer Connie Walker of the U.S. National Optical-Infrared Astronomy Research Laboratory.

The satellites, designed to provide internet access in remote areas, now number in the hundreds. [Following] the launch of the first batch by SpaceX in May 2019, astronomers were alarmed by how bright they appear in the sky. If all the planned [launches] go ahead, the number of satellites will grow beyond 100,000. Since last year, there have been a number of independent studies of [satellites’] possible impact. [The] workshop’s report is the first time the satellite companies, and those who would be affected (astronomers to the agencies that fund them and their telescopes), have pooled their results and worked out a strategy for the future.

NASA Satellite Image Two
Photo Credit: NASA on Unsplash

The satellite trails are very bright, and out of focus slightly, so they’re wide and cover several pixels on images taken with a test version of the (soon to open Vera C.) Rubin Observatory’s camera, notes Tyson. [Telescopes] that need to work during twilight will also run into problems. Because the satellites are in low orbits, they will often be seen close to the horizon and will be most visible when they are still in sunlight but, the observer is not. If, however, satellite operators choose orbits above 600 kilometers, the situation gets worse because, then, their spacecraft are visible for more of the night, and in [the] summer, all night long. Astronomers should also develop software tools to remove satellite trails from images and the companies should make accurate orbital data available for their orbiters so telescopes can try to avoid them.

The only measure the report could offer to totally eliminate the damage to astronomy was to launch fewer or no low-orbiting satellites…likely not an option given the financial investments the companies are making in the [satellites] and the lucrative market they foresee.

Tyson and his colleagues have been working with SpaceX engineers to modify their satellites to reduce their brightness. His team has also modeled trying to steer the Rubin Observatory telescope to avoid passing satellites but, Tyson says there are simply too many. Astronomers are already actively pursuing image processing solutions but, he says “the jury’s out” on how much that can help.

Daniel Clery
Science Magazine
August 25, 2020

Addtional Reading:
Report Offers Roadmap (American Astronomical Society)
SATCON Report (NOIRLab)
Satellites Could Spoil View of Giant Sky Telescope (Science Magazine February 27, 2020)

Theodolite Thursday: Dolphins Learn Unusual Hunting Behavior

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Yes…another new heading. From Merriam-Webster:

[A] surveyor’s instrument for measuring horizontal and […] vertical angles

This is the instrument of land surveyors. In my case, I will survey other things. ~Vic

Dolphins Unsplash Image
Photo Credit: Courtnie Tosana on Unsplash

In the crystal clear waters of Shark Bay in Western Australia, scientists have noticed bottlenose dolphins engaging in an unusual behavior. They guide fish into the empty shells of giant snails, bring the shells to the surface and, then, shake them vigorously to dislodge the prey into their open mouths like a person polishing off a bag of popcorn. That extra effort, known as shelling, gets them a guaranteed meal.

Because the dolphins […] use the shells as a trap, this is the second known case of these marine mammals using tools. The first was reported in [1984] when researchers found that bottlenose dolphins wear marine sponges like protective gloves over their beaks to forage for fish on the sea floor. Now, researchers have shown that the dolphins of Shark Bay learn shelling from their friends. It’s the first time social learning involving a tool has been discovered in these mammals and a rare example of such learning in the animal kingdom.

Dolphins Unsplash Image Two
Photo Credit: Red Charlie on Unsplash

Though scientists noticed the shelling behavior more than 10 years ago, it became more frequent following an unusual marine heat wave (PDF) off Western Australia in 2011. The high temperatures roiled Shark Bay’s ecosystem and many gastropods, including sea snails, are believed to have died. “We think the dolphins took advantage of this die-off,” says Sonja Wild, a behavioral ecologist at the Max Planck Institute of Animal Behavior. “The next season,” she says, “there was an incredible increase in shelling”, which made it possible for her to tease out how young adult dolphins learn to do it.

Wild says shelling starts among the adults [but], the more time a young dolphin spends around an accomplished sheller […], “the more likely it is to learn” the technique and pass it on to others later. Still, because dolphin calves spend more than 30,000 hours with their mothers, it’s possible that some learned the trick from their moms, [states] Janet Mann, a dolphin expert at Georgetown University. It’s considered more cognitively demanding to learn a skill like shelling from an unrelated individual because both learner and demonstrator must be socially tolerant, especially while hunting.

Virginia Morell
Science Magazine
June 25, 2020