Astronomy

SpaceX scrubbed a planned launch of 23 Starlink satellites on Sunday (Nov. 3) due to a helium issue in the first stage of the company's Falcon 9 rocket.

Liftoff is scheduled for 9:29 p.m. ET today (Nov. 4).

What was once fair under the law may become unfair when science changes. The law must react to uphold due process

Monday evening (Nov. 4), the night before Election Day, will bring a lovely celestial display involving the two brightest objects in the nighttime sky: the moon and Venus.

The stars are destroying the pillars.

The outcome of the 2024 U.S. presidential election could set the climate agenda, reshape public education and shift the dynamics of global science collaboration.

Over 100 astronomers from leading U.S. universities have signed an open letter calling for an assessment of potential impacts of satellite megaconstellations on Earth's environment.

The focus is on finance at the UN climate summit in Baku, Azerbaijan, this month, but countries are a long way from any kind of consensus

The focus is on finance at the UN climate summit in Baku, Azerbaijan, this month, but countries are a long way from any kind of consensus

A galaxy cluster bends light from seven background galaxies around it, letting astronomers peer into space and time

Rocket Lab plans to launch a mission for a "confidential commercial customer" early Tuesday morning (Nov. 5), and you can watch the action live.

Japan launched the Kirameki 3 military communications satellite Monday morning (Nov. 4), on the fourth-ever flight of the country's H3 rocket.

According to the United Nations, the world produces about 430 million metric tons (267 U.S. tons) of plastic annually, two-thirds of which are only used for a short time and quickly become garbage. What’s more, plastics are the most harmful and persistent fraction of marine litter, accounting for at least 85% of total marine waste. This problem is easily recognizable due to the Great Pacific Garbage Patch and the amount of plastic waste that washes up on beaches and shores every year. Unless measures are taken to address this problem, the annual flow of plastic into the ocean could triple by 2040.

One way to address this problem is to improve the global tracking of plastic waste using Earth observation satellites. In a recent study, a team of Australian researchers developed a new method for spotting plastic rubbish on our beaches, which they successfully field-tested on a remote stretch of coastline. This satellite imagery tool distinguishes between sand, water, and plastics based on how they reflect light differently. It can detect plastics on shorelines from an altitude of more than 600 km (~375 mi) – higher than the International Space Station‘s (ISS) orbit.

The paper that describes their tool, “Beached Plastic Debris Index; a modern index for detecting plastics on beaches,” was recently published by the Marine Pollution Bulletin. The research team was led by Jenna Guffogg, a researcher at the Royal Melbourne Institute of Technology University (RMIT) and the Faculty of Geo-Information Science and Earth Observation (ITC) at the University of Twente. She was joined by multiple colleagues from both institutions. The study was part of Dr. Guffogg’s joint PhD research with the support of an Australian Government Research Training Program (RTP) scholarship.

Dr Jenna Guffogg said plastic on beaches can have severe impacts on wildlife and their habitats, just as it does in open waters. Credit: BPDI

According to current estimates, humans dump well over 10 million metric tons (11 million U.S. tons) of plastic waste into our oceans annually. Since plastic production continues to increase worldwide, these numbers are projected to increase dramatically. What ends up on our beaches can severely impact wildlife and marine habitats, just like the impact it has in open waters. If these plastics are not removed, they will inevitably fragment into micro and nano plastics, another major environmental hazard. Said Dr. Guffogg in a recent RMIT University press release:

“Plastics can be mistaken for food; larger animals become entangled, and smaller ones, like hermit crabs, become trapped inside items such as plastic containers. Remote island beaches have some of the highest recorded densities of plastics in the world, and we’re also seeing increasing volumes of plastics and derelict fishing gear on the remote shorelines of northern Australia.

“While the impacts of these ocean plastics on the environment, fishing and, tourism are well documented, methods for measuring the exact scale of the issue or targeting clean-up operations, sometimes most needed in remote locations, have been held back by technological limitations.”

Satellite technology is already used to track plastic garbage floating around the world’s oceans. This includes relatively small drifts containing thousands of plastic bottles, bags, and fishing nets, but also gigantic floating trash islands like the Great Pacific Garbage Patch. As of 2018, this garbage patch measured about 1.6 million km2 (620,000 mi2) and consisted of 45,000–129,000 metric tons (50,000–142,000 U.S. tons). However, the technology used to locate plastic waste in the ocean is largely ineffective at spotting plastic on beaches.

Geospatial scientists have found a way to detect plastic waste on remote beaches, bringing us closer to global monitoring options. Credit: RMIT

Much of the problem is that plastic can be mistaken for patches of sand when viewed from space. The Beached Plastic Debris Index (BPDI) developed by Dr. Guffogg and her colleagues circumvents this by employing a spectral index – a mathematical formula that analyzes patterns of reflected light. The BPDI is specially designed to map plastic debris in coastal areas using high-definition data from the WorldView-3 satellite, a commercial Earth observation satellite (owned by Maxar Technologies) that has been in operation since 2014.

Thanks to their efforts, scientists now have an effective way to monitor plastic on beaches, which could assist in clean-up operations. As part of the remote sensing team at RMIT, Dr. Guffogg and her colleagues have developed similar tools for monitoring forests and mapping bushfires from space. To validate the BPDI, the team field-tested it by placing 14 plastic targets on a beach in southern Gippsland, about 200 km (125 mi) southeast of Melbourne. Each target was made of a different type of plastic and measured two square meters (21.5 square feet) – smaller than the satellite’s pixel size of about three square meters.

The resulting images were compared to three other indices, two designed for detecting plastics on land and one for detecting plastics in aquatic settings. The BPDI outperformed all three as the others struggled to differentiate between plastics and sand or misclassified shadows and water as plastic. As study author Dr. Mariela Soto-Berelov explained, this makes the BPDI far more useful for environments where water and plastic-contaminated pixels are likely to coexist.  

“This is incredibly exciting, as up to now we have not had a tool for detecting plastics in coastal environments from space. The beauty of satellite imagery is that it can capture large and remote areas at regular intervals. Detection is a key step needed for understanding where plastic debris is accumulating and planning clean-up operations, which aligns with several Sustainable Development Goals, such as Protecting Seas and Oceans.”  

The next step is to test the BPDI tool in real-life scenarios, which will consist of the team partnering with various organizations dedicated to monitoring and addressing the plastic waste problem.

Further Reading: RMIT, Marine Pollution Bulletin

The post Plastic Waste on our Beaches Now Visible from Space, Says New Study appeared first on Universe Today.

Space-based telescopes are remarkable. Their view isn’t obscured by the weather in our atmosphere, and so they can capture incredibly detailed images of the heavens. Unfortunately, they are quite limited in mirror size. As amazing as the James Webb Space Telescope is, its primary mirror is only 6.5 meters in diameter. Even then, the mirror had to have foldable components to fit into the launch rocket. In contrast, the Extremely Large Telescope currently under construction in northern Chile will have a mirror more than 39 meters across. If only we could launch such a large mirror into space! A new study looks at how that might be done.

As the study points out, when it comes to telescope mirrors, all you really need is a reflective surface. It doesn’t need to be coated onto a thick piece of glass, nor does it need a big, rigid support structure. All that is just needed to hold the shape of the mirror against its own weight. As far as starlight is concerned, the shiny surface is all that matters. So why not just use a thin sheet of reflective material? You could just roll it up and put it in your launch vehicle. We could, for example, easily launch a 40-meter roll of aluminum foil into space.

Of course, things aren’t quite that simple. You would still need to unroll your membrane telescope back into its proper shape. You would also need a detector to focus the image upon, and you’d need a way to keep that detector in the correct alignment with the broadsheet mirror. In principle, you could do that with a thin support structure, which wouldn’t add an excessive bulk to your telescope. But even if we assume all of those engineering problems could be solved, you’d still have a problem. Even in the vacuum of space, the shape of such a thin mirror would deform over time. Solving this problem is the main focus of this new paper.

Once launched into space and unfurled, the membrane mirror wouldn’t deform significantly. But to capture sharp images, the mirror would have to maintain focus on the order of visible light. When the Hubble was launched, its mirror shape was off by less than the thickness of a human hair, and it took correcting lenses and an entire shuttle mission to fix. Any shifts on that scale would render our membrane telescope useless. So the authors look to a well-used trick of astronomers known as adaptive optics.

How radiative adaptive optics might work. Credit: Rabien, et al

Adaptive optics is used on large ground-based telescopes as a way to correct for atmospheric distortion. Actuators behind the mirror distort the mirror’s shape in real time to counteract the twinkles of the atmosphere. Essentially, it makes the shape of the mirror imperfect to account for our imperfect view of the sky. A similar trick could be used for a membrane telescope, but if we had to launch a complex actuator system for the mirror, we might as well go back to launching rigid telescopes. But what if we simply use laser projection instead?

By shining a laser projection onto the mirror, we could alter its shape through radiative recoil. Since it is simply a thin membrane, the shape would be significant enough to create optical corrections, and it could be modified in real time to maintain the mirror’s focus. The authors call this technique radiative adaptive optics, and through a series of lab experiments have demonstrated that it could work.

Doing this in deep space is much more complicated than doing it in the lab, but the work shows the approach is worth exploring. Perhaps in the coming decades we might build an entire array of such telescopes, which would allow us to see details in the distant heavens we can now only imagine.

Reference: Rabien, S., et al. “Membrane space telescope: active surface control with radiative adaptive optics.” Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave. Vol. 13092. SPIE, 2024.

The post Future Space Telescopes Could be Made From Thin Membranes, Unrolled in Space to Enormous Size appeared first on Universe Today.

Space.com has an exclusive three-page preview of IDW's new "Star Trek: Lower Decks #1" comic.

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China's Shenzhou 18 crew have returned home after more than six months in space.

Sometimes a river of hot gas flows over your head.