Job titles of the future: Satellite streak astronomer

Earlier this year, the $800 million Vera Rubin Observatory commenced its decade-long quest to create an extremely detailed time-lapse movie of the universe. Rubin is capable of capturing many more stars than any other astronomical observatory ever built; it also sees many more satellites. Up to 40% of images captured by the observatory within its first 10 years of operation will be marred by their sunlight-reflecting streaks. 

Meredith Rawls, a research scientist at the telescope’s flagship observation project, Vera Rubin’s Legacy Survey of Space and Time, is one of the experts tasked with protecting Rubin’s science mission from the satellite blight, which could make observations more difficult because the satellites are millions of times brighter than the faint stars and galaxies it hopes to study. Satellites could also confuse astronomers when the sudden brightening they cause gets mistaken for astronomical phenomena.

An unexpected path

When Rawls joined the Rubin project in 2016, she says, she had no clue what turn her career would take. “I was hired as a postdoc to help build a new imaging pipeline to process precursor images [and] analyze results to identify things we needed to fix or change,” she says.

But in 2019, SpaceX began deploying its internet-beaming Starlink constellation, and the astronomical community started to sound alarm bells. The satellites were orbiting too low and reflected too much sunlight, leaving bright marks in telescope images. A year later, Rawls and a handful of her colleagues were the first to make a scientific assessment of the satellite streaks’ effect on astronomical observations, using images from the Víctor M. Blanco telescope (which, like Rubin, is in Chile). “We wanted to see how bright those streaks were and look at possible mitigation strategies,” Rawls says. Her team found that although the streaks weren’t overwhelmingly bright, they still risked affecting scientific observations.

Streak removal 

Since those early observations, an entirely new subdiscipline of astronomical image processing has emerged, focusing on techniques to remove satellite light pollution from the data and designing observation protocols to prevent too-bright satellites from spoiling the views. Rawls has become one of the leading experts in the fast-evolving field, which is only set to grow in importance in the coming years.

“We are fundamentally altering the night sky by launching a lot more stuff at an unsustainably increasing rate,” says Rawls, who is also an astronomy researcher at the University of Washington. 

To mitigate the damage, she and her colleagues designed algorithms that compare images of the same spot in the sky to detect unexpected changes and determine whether those could have been caused by passing satellites or natural phenomena like asteroids or stellar explosions.

A rising force

The number of satellites orbiting our planet has risen from a mere thousand some 15 years ago to more than 12,000 active satellites today. About 8,000 of those belong to SpaceX’s Starlink, but other ventures threaten to worsen the light-pollution problem in the coming years. US-based AST SpaceMobile, for example, is building a constellation of giant orbiting antenna arrays to beam 5G connectivity directly to users’ phones. The first five of these satellites—each over 60 square meters in size—are already in orbit and reflecting so much light that Rubin must adjust its observing schedule to avoid their paths. 

“So far, what we’ve seen with the initial images is that it’s a nuisance but not a science-ending thing,” says Rawls. She remains optimistic that she and her colleagues can stay on top of the problem.

Tereza Pultarova is a London-based science and technology journalist.

The case against humans in space

Elon Musk and Jeff Bezos are bitter rivals in the commercial space race, but they agree on one thing: Settling space is an existential imperative. Space is the place. The final frontier. It is our human destiny to transcend our home world and expand our civilization to extraterrestrial vistas.

This belief has been mainstream for decades, but its rise has been positively meteoric in this new gilded age of astropreneurs. Expanding humanity beyond Earth is both our birthright and our duty to the future, they insist. Failing to do so would consign our species to certain extinction—either by our own hand, perhaps through nuclear war or climate change, or in some cosmic disaster, like a massive asteroid impact.

But as visions of giant orbital stations and Martian cities dance in our heads, a case against human space colonization has found its footing in a number of recent books. The argument grows from many grounds: Doubts about the practical feasibility of off-Earth communities. Concerns about the exorbitant costs, including who would bear them and who would profit. Realism about the harsh environment of space and the enormous tax it would exact on the human body. Suspicion of the underlying ideologies and mythologies that animate the race to settle space.

And, more bluntly, a recognition that “space sucks” and a lot of people have “underestimated the scale of suckitude,” as Kelly and Zach Weinersmith put it in their book A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through?, which was released in paperback earlier this year.

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The Weinersmiths, a husband-wife team, spent years thinking it through—in delightfully pragmatic detail. A City on Mars provides ground truth for our lofty celestial dreams by gaming out the medical, technical, legal, ethical, and existential consequences of space settlements. 

Much to the authors’ own dismay, the result is a grotesquery of possible outcomes including (but not limited to) Martian eugenics, interplanetary war, and—­memorably—“space cannibalism.” 

The Weinersmiths puncture the gauzy fantasy of space cities by asking pretty basic questions, like how to populate them. Astronauts experience all kinds of medical challenges in space, such as radiation exposure and bone loss, which would increase risks to both parents and babies. Nobody wants their pregnant “glow” to be a by-product of cosmic radiation.

Trying to bring forth babies in space “is going to be tricky business, not just in terms of science, but from the perspective of scientific ethics,” they write. “Adults can consent to being in experiments. Babies can’t.”

You don’t even have to contemplate going to Mars to make some version of this case. In Ground Control: An Argument for the End of Human Space Exploration, Savannah Mandel chronicles how past and present generations have regarded human spaceflight as an affront to vulnerable children right here on Earth.

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“Hungry Kids Can’t Eat Moon Rocks,” read signs at a protest outside Kennedy Space Center on the eve of the Apollo 11 launch in July 1969. Gil Scott-Heron’s 1970 poem “Whitey on the Moon” rose to become the de facto anthem of this movement, which insists, to this day, that until humans get our earthly house in order, we have no business building new ones in outer space.

Ground Control, part memoir and part manifesto, channels this lament: How can we justify the enormous cost of sending people beyond our planet when there is so much suffering here at home? 

Advocates for human space exploration reject the zero-sum framing and point to the many downstream benefits of human spaceflight. Space exploration has catalyzed inventions from the CAT scan to baby formula. There is also inherent value in our shared adventure of learning about the vast cosmos.

Those upsides are real, but they are not remotely well distributed. Mandel predicts that the commercial space sector in its current form will only exacerbate inequalities on Earth, as profits from space ventures flow into the coffers of the already obscenely rich. 

In her book, Mandel, a space anthropologist and scholar at Virginia Tech, describes a personal transformation from spacey dreamer to grounded critic. It began during fieldwork at Spaceport America, a commercial launch facility in New Mexico, where she began to see cracks in the dazzling future imagined by space billionaires. As her career took her from street protests in London to extravagant space industry banquets in Washington, DC, she writes, “crystal clear glasses” replaced “the rose-colored ones.”

Mandel remains enchanted by space but is skeptical that humans are the optimal trailblazers. Robots, rovers, probes, and other artificial space ambassadors could do the job for a fraction of the price and without risk to life, limb, and other corporeal vulnerabilities.  

“A decentralization of self needs to occur,” she writes. “A dissolution of anthropocentrism, so to speak. And a recognition that future space explorers may not be man, even if man moves through them.” 

In other words, giant leaps for mankind no longer necessitate a man’s small steps; the wheels of a rover or the rotors of a copter offer a much better bang for our buck than boots on the ground.

In contrast to the Weinersmiths, Mandel devotes little attention to the physical dangers and limitations that space imposes on humans. She is more interested in a kind of psychic sickness that drives the impulse to abandon our planet and rush into new territories.

Mary-Jane Rubenstein, a scholar of religion at Wesleyan University, presents a thorough diagnosis of this exact pathology in her 2022 book Astrotopia: The Dangerous Religion of the Corporate Space Race, which came out in paperback last year. It all begins, appropriately enough, with the book of Genesis, where God creates Earth for the dominion of man. Over the years, this biblical brain worm has offered divine justification for the brutal colonization and environmental exploitation of our planet. Now it serves as the religious rocket fuel propelling humans into the next frontier, Rubenstein argues.

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“The intensifying ‘NewSpace race’ is as much a mythological project as it is a political, economic, or scientific one,” she writes. “It’s a mythology, in fact, that holds all these other efforts together, giving them an aura of duty, grandeur, and benevolence.”

Rubenstein makes a forceful case that malignant outgrowths of Christian ideas scaffold the dreams of space settlements championed by Musk, Bezos, and like-minded enthusiasts—even if these same people might never describe themselves as religious. If Earth is man’s dominion, space is the next logical step. Earth is just a temporary staging ground for a greater destiny; we will find our deliverance in the heavens.   

“Fuck Earth,” Elon Musk said in 2014. “Who cares about Earth? If we can establish a Mars colony, we can almost certainly colonize the whole solar system.”

Jeff Bezos, for one, claims to care about Earth; that’s among his best arguments for why humans should move beyond it. If heavy industries and large civilian populations cast off into the orbital expanse, our home world can be, in his words, “zoned residential and light industry,” allowing it to recover from anthropogenic pressures.

Bezos also believes that space settlements are essential for the betterment of humanity, in part on the grounds that they will uncork our population growth. He envisions an orbital archipelago of stations, sprawled across the solar system, that could support a collective population of a trillion people. “That’s a thousand Mozarts. A thousand Einsteins,” Bezos has mused. “What a cool civilization that would be.”

It does sound cool. But it’s an easy layup for Rubenstein: This “numbers game” approach would also produce a thousand Hitlers and Stalins, she writes. 

And that is the real crux of the argument against pushing hard torapidly expand human civilization into space: We will still be humans when we get there. We won’t escape our vices and frailties by leaving Earth—in fact, we may exacerbate them. 

While all three books push back on the existential argument for space settlements, the Weinersmiths take the rebuttal one step further by proposing that space colonization might actually increase the risk of self-annihilation rather than neutralizing it.

“Going to space will not end war because war isn’t caused by anything that space travel is apt to change, even in the most optimistic scenarios,” they write. “Humanity going to space en masse probably won’t reduce the likelihood of war, but we should consider that it might increase the chance of war being horrific.” 

The pair imagine rival space nations exchanging asteroid fire or poisoning whole biospheres. Proponents of space settlements often point to the fate of the dinosaurs as motivational grist, but what if a doomsday asteroid were deliberately flung between human cultures as a weapon? It may sound outlandish, but it’s no more speculative than a floating civilization with a thousand Mozarts. It follows the same logic of extrapolating our human future in space from our behavior on Earth in the past.

So should we just sit around and wait for our inevitable extinction? The three books have more or less the same response: What’s the rush? It is far more likely that humanity will be wiped out by our own activity in the near term than by any kind of cosmic threat. Worrying about the expansion of the sun in billions of years, as Musk has openly done, is frankly hysterical. 

In the meantime, we have some growing up to do. Mandel and Rubenstein both argue that any worthy human future in space must adopt a decolonizing approach that emphasizes caretaking and stewardship of this planet and its inhabitants before we set off for others. They draw inspiration from science fiction, popular culture, and Indigenous knowledge, among other sources, to sketch out these alternative visions of an off-Earth future. 

Mandel sees hope for this future in post-scarcity political theories. She cites various attempts to anticipate the needs of future generations—ideas found in the work of the social theorist Aaron Benanav, or in the values expressed by the Green New Deal, or in the fictional Ministry for the Future imagined by Kim Stanley Robinson in his 2020 novel of the same name. Whatever you think of the controversial 2025 book Abundance, by Ezra Klein and Derek Thompson, it is also appealing to the same demand for a post-scarcity road map.  

To that end, Mandel envisions “the creation of a governing body that would require that techno-scientific plans, especially those with a global reach, take into consideration multigenerational impacts and multigenerational voices.”  

For Rubenstein, religion is the poison, but it may also offer the cure. She sees potential in a revival of pantheism, which is the belief that all the contents of the universe—from rocks to humans to galaxies—are divine and perhaps alive on some level. She hasn’t fully converted herself to this movement, let alone become an evangelist, but she says it’s a spiritual direction that could be an effective counterweight to dominionist views of the universe.

“It doesn’t matter whether … any sort of pantheism is ‘true,’” she writes. “What matters is the way any given mythology prompts us to interact with the world we’re a part of—the world each of our actions helps to make and unmake. And frankly, some mythologies prompt us to act better than others.”

All these authors ultimately conclude that it would be great if humans lived in space—someday, if and when we’ve matured. But the three books all express concerns about efforts by commercial space companies, with the help of the US government, to bypass established space laws and norms—concerns that have been thoroughly validated in 2025.  

The combustible relationship between Elon Musk and Donald Trump has raised eyebrows about cronyism—and retribution—between governments and space companies. Space is rapidly becoming weaponized. And recent events have reminded us of the immense challenges of human spaceflight. SpaceX’s next-­generation Starship vehicle has suffered catastrophic failures in several test flights, while Boeing’s Starliner capsule experienced malfunctions that kept two astronauts on the International Space Station for months longer than expected. Even space tourism is developing a bad rap: In April, a star-studded all-woman crew on a Blue Origin suborbital flight was met with widespread backlash as a symbol of out-of-touch wealth and privilege.

It is at this point that we must loop back to the issue of “suckitude,” which Mandel also channels in her book through the killer opening of M.T. Anderson’s novel Feed: “We went to the moon to have fun, but the moon turned out to completely suck.”

The dreams of space settlements put forward by Musk and Bezos are insanely fun. The reality may well suck. But it’s doubtful that any degree of suckitude will slow down the commercial space race, and the authors do at times seem to be yelling into the cosmic void. 

Still, the books challenge space enthusiasts of all stripes to imagine new ways of relating to space that aren’t so tactile and exploitative. Along those lines, Rubenstein shares a compelling anecdote in Astrotopia about an anthropologist who lived with an Inuit community in the early 1970s. When she told them about the Apollo moon landings, her hosts burst out in laughter. 

“We didn’t know this was the first time you white people had been to the moon,” they said. “Our shamans go all the time … The issue is not whether we go to visit our relatives, but how we treat them and their homeland when we go.” 

Becky Ferreira is a science reporter based in upstate New York, and author of First Contact, a book about the search for alien life, which will be published in September. 

NASA’s new AI model can predict when a solar storm may strike

NASA and IBM have released a new open-source machine learning model to help scientists better understand and predict the physics and weather patterns of the sun. Surya, trained on over a decade’s worth of NASA solar data, should help give scientists an early warning when a dangerous solar flare is likely to hit Earth.

Solar storms occur when the sun erupts energy and particles into space. They can produce solar flares and slower-moving coronal mass ejections that can disrupt radio signals, flip computer bits onboard satellites, and endanger astronauts with bursts of radiation. 

There’s no way to prevent these sorts of effects, but being able to predict when a large solar flare will occur could let people work around them. However, as Louise Harra, an astrophysicist at ETH Zurich, puts it, “when it erupts is always the sticking point.”

Scientists can easily tell from an image of the sun if there will be a solar flare in the near future, says Harra, who did not work on Surya. But knowing the exact timing and strength of a flare is much harder, she says. That’s a problem because a flare’s size can make the difference between small regional radio blackouts every few weeks (which can still be disruptive) or a devastating solar superstorm that would cause satellites to fall out of orbit and electrical grids to fail. Some solar scientists believe we are overdue for a solar superstorm of this magnitude.

While machine learning has been used to study solar weather events before, the researchers behind Surya hope the quality and sheer scale of their data will help it predict a wider range of events more accurately. 

The model’s training data came from NASA’s Solar Dynamics Observatory, which collects pictures of the sun at many different wavelengths of light simultaneously. That made for a dataset of over 250 terabytes in total.

Early testing of Surya showed it could predict some solar flares two hours in advance. “It can predict the solar flare’s shape, the position in the sun, the intensity,” says Juan Bernabe-Moreno, an AI researcher at IBM who led the Surya project. Two hours may not be enough to protect against all the impacts a strong flare could have, but every moment counts. IBM claims in a blog post that this can as much as double the warning time currently possible with state-of-the-art methods, though exact reported lead times vary. It’s possible this predictive power could be improved through, for example, fine-tuning or by adding other data, as well. 

According to Harra, the hidden patterns underlying events like solar flares are hard to understand from Earth. She says that while astrophysicists know the conditions that make these events happen, they still do not understand why they occur when they do. “It’s just those tiny destabilizations that we know happen, but we don’t know when,” says Harra. The promise of Surya lies in whether it can find the patterns underlying those destabilizations faster than any existing methods, buying us extra time.

However, Bernabe-Moreno is excited for the potential beyond predicting solar flares. He hopes to use Surya alongside previous models he worked on for IBM and NASA that predict weather here on Earth to better understand how solar storms and Earth weather are connected. “There is some evidence about solar weather influencing lightning, for example,” he says. “What are the cross effects, and where and how do you map the influence from one type of weather to the other?”

Because Surya is a foundation model, trained without a specialized job, NASA and IBM hope that it can find many patterns in the sun’s physics, much as general-purpose large language models like ChatGPT can take on many different tasks. They believe Surya could even enable new understandings about how other celestial bodies work. 

“Understanding the sun is a proxy for understanding many other stars,” Bernabe-Moreno says. “We look at the sun as a laboratory.”

See the stunning first images from the Vera C. Rubin Observatory

The first spectacular images taken by the Vera C. Rubin Observatory have been released for the world to peruse: a panoply of iridescent galaxies and shimmering nebulas. “This is the dawn of the Rubin Observatory,” says Meg Schwamb, a planetary scientist and astronomer at Queen’s University Belfast in Northern Ireland.

Much has been written about the observatory’s grand promise: to revolutionize our understanding of the cosmos by revealing a once-hidden population of far-flung galaxies, erupting stars, interstellar objects, and elusive planets. And thanks to its unparalleled technical prowess, few doubted its ability to make good on that. But over the past decade, during its lengthy construction period, “everything’s been in the abstract,” says Schwamb.

Today, that promise has become a staggeringly beautiful reality. 

Rubin’s view of the universe is unlike any that preceded it—an expansive vision of the night sky replete with detail, including hazy envelopes of matter coursing around galaxies and star-paved bridges arching between them. “These images are truly stunning,” says Pedro Bernardinelli, an astronomer at the University of Washington.

During its brief perusal of the night sky, Rubin even managed to spy more than 2,000 never-before-seen asteroids, demonstrating that it should be able to spotlight even the sneakiest denizens, and darkest corners, of our own solar system.

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Today’s reveal is a mere amuse-bouche compared with what’s to come: Rubin, funded by the US National Science Foundation and the Department of Energy, is set for at least 10 years of planned observations. But this moment, and these glorious inaugural images, are worth celebrating for what they represent: the culmination of over a decade of painstaking work. 

“This is a direct demonstration that Rubin is no longer in the future,” says Bernardinelli. “It’s the present.”

The observatory is named after the late Vera Rubin, an astronomer who uncovered strong evidence for dark matter, a mysterious and as-yet-undetected something that’s binding galaxies together more strongly than the gravity of ordinary, visible matter alone can explain. Trying to make sense of dark matter—and its equally mysterious, universe-stretching cousin, dubbed dark energy—is a monumental task, one that cannot be addressed by just one line of study or scrutiny of one type of cosmic object.

That’s why Rubin was designed to document anything and everything that shifts or sparkles in the night sky. Sitting atop Chile’s Cerro Pachón mountain range, it boasts a 7,000-pound, 3,200-megapixel digital camera that can take detailed snapshots of a large patch of the night sky; a house-size cradle of mirrors that can drink up extremely distant and faint starlight; and a maze of joints and pistons that allow it to swivel about with incredible speed and precision. A multinational computer network permits its sky surveys to be largely automated, its images speedily processed, any new objects easily detected, and the relevant groups of astronomers quickly alerted.

All that technical wizardry allows Rubin to take a picture of the entire visible night sky once every few days, filling in the shadowed gaps and unseen activity between galaxies. “The sky [isn’t] static. There are asteroids zipping by, and supernovas exploding,” says Yusra AlSayyad, Rubin’s overseer of image processing. By conducting a continuous survey over the next decade, the facility will create a three-dimensional movie of the universe’s ever-changing chaos that could help address all sorts of astronomic queries. What were the very first galaxies like? How did the Milky Way form? Are there planets hidden in our own solar system’s backyard?

Rubin’s first glimpse of the firmament is predictably bursting with galaxies and stars. But the resolution, breadth, and depth of the images have taken astronomers aback. “I’m very impressed with these images. They’re really incredible,” says Christopher Conselice, an extragalactic astronomer at the University of Manchester in England.

One shot, created from 678 individual exposures, showcases the Trifid and Lagoon nebulas—two oceans of luminescent gas and dust where stars are born. Others depict a tiny portion of Rubin’s view of the Virgo Cluster, a zoo of galaxies. Hues of blue are coming from relatively nearby whirlpools of stars, while red tints emanate from remarkably distant and primeval galaxies. 

The rich detail in these images is already proving to be illuminating. “As galaxies merge and interact, the galaxies are pulling stars away from each other,” says Conselice. This behavior can be seen in plumes of diffuse light erupting from several galaxies, creating halos around them or illuminated bridges between them—records of these ancient galaxies’ pasts.

Images like these are also likely to contain several supernovas, the explosive final moments of sizable stars. Not only do supernovas seed the cosmos with all the heavy elements that planets—and life—rely on, but they can also hint at how the universe has expanded over time. 

Anais Möller, an astrophysicist at the Swinburne University of Technology in Melbourne, Australia, is a supernova hunter. “I search for exploding stars in very far away galaxies,” she says. Older sky surveys have found plenty, but they can lack context: You can see the explosion, but not what galaxy it’s from. Thanks to Rubin’s resolution—amply demonstrated by the Virgo Cluster set of images—astronomers can now “find where those exploding stars live,” says Möller.

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While taking these images of the distant universe, Rubin also discovered 2,104 asteroids flitting about in our own solar system—including seven whose orbits hew close to Earth’s own. This number may sound impressive, but it’s just par for the course for Rubin. In just a few months, it will find over a million new asteroids—doubling the current known tally. And over the course of its decadal survey, Rubin is projected to identify 89,000 near-Earth asteroids, 3.7 million asteroids in the belt between Mars and Jupiter, and 32,000 icy objects beyond Neptune. 

Finding more than 2,000 previously hidden asteroids in just a few hours of observations, then, “wasn’t even hard” for Rubin, says Mario Jurić, an astronomer at the University of Washington. “The asteroids really popped out.”

Rubin’s comprehensive inventorying of the solar system has two benefits. The first is scientific: All those lumps of rocks and ice are the remnants of the solar system’s formative days, which means astronomers can use them to understand how everything around us was pieced together. 

The second benefit is security. Somewhere out there, there could be an asteroid on an Earthbound trajectory—one whose impact could devastate an entire city or even several countries. Engineers are working on defensive tech designed to either deflect or obliterate such asteroids, but if astronomers don’t know where they are, those defenses are useless. In quickly finding so many asteroids, Rubin has clearly shown that it will bolster Earth’s planetary defense capabilities like no other ground-based telescope.

Altogether, Rubin’s debut has validated the hopes of countless astronomers: The observatory won’t just be an incremental improvement on what’s come before. “I think it’s a generational leap,” says Möller. It is a ruthlessly efficient, discovery-making behemoth—and a firehose of astronomic delights is about to inundate the scientific community. “It’s very scary,” says Möller. “But very exciting at the same time.”

It’s going to be a very hectic decade. As Schwamb puts it, “The roller-coaster starts now.”

Inside the race to find GPS alternatives

Later this month, an inconspicuous 150-kilogram satellite is set to launch into space aboard the SpaceX Transporter 14 mission. Once in orbit, it will test super-accurate next-generation satnav technology designed to make up for the shortcomings of the US Global Positioning System (GPS). 

The satellite is the first of a planned constellation called Pulsar, which is being developed by California-based Xona Space Systems. The company ultimately plans to have a constellation of 258 satellites in low Earth orbit. Although these satellites will operate much like those used to create GPS, they will orbit about 12,000 miles closer to Earth’s surface, beaming down a much stronger signal that’s more accurate—and harder to jam. 

“Just because of this shorter distance, we will put down signals that will be approximately a hundred times stronger than the GPS signal,” says Tyler Reid, chief technology officer and cofounder of Xona. “That means the reach of jammers will be much smaller against our system, but we will also be able to reach deeper into indoor locations, penetrating through multiple walls.”

A satnav system for the 21st century

The first GPS system went live in 1993. In the decades since, it has become one of the foundational technologies that the world depends on. The precise positioning, navigation, and timing (PNT) signals beamed by its  satellites underpin much more than Google Maps in your phone. They guide drill heads at offshore oil rigs, time-stamp financial transactions, and help sync power grids all over the world.

But despite the system’s indispensable nature, the GPS signal is easily suppressed or disrupted by everything from space weather to 5G cell towers to phone-size jammers worth a few tens of dollars. The problem has been whispered about among experts for years, but it has really come to the fore in the last three years, since Russia invaded Ukraine. The boom in drone warfare that came to characterize that war also triggered a race to develop technology for thwarting drone attacks by jamming the GPS signals they need to navigate—or spoofing the signal, creating convincing but fake positioning data. 

The crucial problem is one of distance: The GPS constellation, which consists of 24 satellites plus a handful of spares, orbits 12,550 miles (20,200 kilometers) above Earth, in a region known as medium Earth orbit. By the time their signals get all the way down to ground-based receivers, they are so faint that they can easily be overridden by jammers.

Other existing Global Navigation Satellite System constellations, such as Europe’s Galileo, Russia’s GLONASS, and China’s Beidou, have similar architectures and experience the same problems.

But when Reid and cofounder Brian Manning founded Xona Space Systems in 2019, they didn’t think about jamming and spoofing. Their goal was to make autonomous driving ready for prime time. 

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Dozens of robocars from Uber and Waymo were already cruising American freeways at that time, equipped with expensive suites of sensors like high-resolution cameras and lidar. The engineers figured a more precise satellite navigation system could reduce the need for those sensors, making it possible to create a safe autonomous vehicle affordable enough to go mainstream. One day, cars might even be able to share their positioning data with one another, Reid says. But they knew that GPS was nowhere near accurate enough to keep self-driving cars within the lane lines and away from other objects on the road. That is especially true in densely built-up urban environments that provide many chances for signals to bounce off walls, creating errors.

“GPS has the superpower of being a ubiquitous system that works the same anywhere in the world,” Reid says. “But it’s a system that was designed primarily to support military missions, virtually to enable them to drop five bombs in the same bowl. But this meter-level accuracy is not enough to guide machines where they need to go and share that physical space with humans safely.”

Reid and Manning began to think about how to build a space-based PNT system that would do what GPS does but better, with accuracy of three inches (10 centimeters) or less and ironclad reliability in all sorts of challenging conditions.

The easiest way to do that is to bring the satellites closer to Earth so that data reaches receivers in real time without inaccuracy-causing delays. The stronger signal of satellites in low Earth orbit is more resistant to disruptions of all sorts. 

When GPS was conceived, none of that was possible. Constellations in low Earth orbit—altitudes up to 1,200 miles (2,000 km)—require hundreds of satellites to provide constant coverage over the entire globe. For a long time, space technology was too bulky and expensive to make such large constellations viable. Over the past decade, however, smaller electronics and lower launch costs have changed the equation.

“In 2019, when we started, the ecosystem of low Earth orbit was really exploding,” Reid says. “We could see things like Starlink, OneWeb, and other constellations take off.”

Matter of urgency

In the few years since Xona launched, concerns about GPS’s vulnerability have begun to grow amid rising geopolitical tensions. As a result, finding a reliable replacement has become a matter of strategic importance. 

In Ukraine especially, GPS jamming and spoofing have become so common that prized US precision munitions such as the High Mobility Artillery Rocket System became effectively blind. Makers of first-person-view drones, which came to symbolize the war, had to refocus on AI-driven autonomous navigation to keep those drones in the game. 

The problem quickly spilled beyond Ukraine. Countries bordering Russia, such as Finland and Estonia, complained that the increasing prevalence of GPS jamming and spoofing was affecting commercial flights and ships in the region.

But Clémence Poirier, a space security researcher at ETH Zurich, says that the problem of GPS disruption isn’t limited to the vicinity of war zones.

“Basic jammers are very cheap and super easily accessible to everyone online,” Poirier says. “Even with the simplest ones, which can be the size of your phone, you can disrupt GPS signals in [an] area of a hundred or more meters.”

In 2013, a truck driver using such a device to conceal his location from his boss accidently disrupted GPS signals around the Newark airport in New Jersey. In 2022, the Dallas Fort Worth International Airport reported a 24-hour GPS outage, which prompted a temporary closure of one of its runways. The source of the interference was never identified. That same year, Denver International Airport experienced a 33-hour GPS disruption. 

Race to securing PNT

“Xona is a promising solution to enhance the resilience of GPS-dependent critical infrastructures and mitigate the threat of GPS jamming and spoofing,” Poirier says. But, she adds, there is no “magic wand,” and a “variety of different approaches will be needed” to solve the problem.

And indeed, Xona is not the only company hoping to provide a backup for the indispensable yet increasingly vulnerable GPS. Companies such as Anello Photonics, based in Santa Clara, California, and Sydney-based Advanced Navigation are testing terrestrial solutions: inertial navigation devices that are small and affordable enough for use beyond high-end military tech. These systems rely on gyroscopes and accelerometers to deduce a vehicle’s position from its own motions. 

When integrated into PNT receivers, these technologies can help detect GPS spoofing and take over for the duration of the interference. Inertial navigation has been around for decades, but recent advances in photonic technologies and microelectromechanical systems have brought it into the mainstream.

The French aerospace and defense conglomerate Safran is developing a system that distributes PNT data via  optical-fiber networks, which form the backbone of the global internet infrastructure. But the allure of space remains strong: The ability to reach any place at any time is what turned GPS from an obscure military system into a piece of taken-for-granted infrastructure that most people today can hardly live without.

And Xona could have some space-based competition. Virginia-based TrustPoint is currently raising funds to build its own low-Earth-orbit PNT constellation, and some have proposed that signals from SpaceX’s Starlink could be repurposed to provide PNT services as well.

Xona hopes to secure its spot in the market by designing its signal to be compatible with that of GPS, allowing manufacturers of GPS receivers to easily slot the new constellation into existing tech. 

Although it will take at least until 2030 for the entire constellation to be up and running, Reid says Xona’s system will provide a valuable addition to the existing GPS infrastructure as soon as 16 of its satellites are in orbit. 

The upcoming launch comes three years after a demonstration mission known as Huginn tested the basics of the technology. The new satellite, called Pulsar-0, will be used to see how well the system can resist jamming or spoofing.

Xona plans to launch an additional four spacecraft next year and hopes to have most of the constellation deployed by 2030. 

A new atomic clock in space could help us measure elevations on Earth

In 2003, engineers from Germany and Switzerland began building a bridge across the Rhine River simultaneously from both sides. Months into construction, they found that the two sides did not meet. The German side hovered 54 centimeters above the Swiss side.

The misalignment occurred because the German engineers had measured elevation with a historic level of the North Sea as its zero point, while the Swiss ones had used the Mediterranean Sea, which was 27 centimeters lower. We may speak colloquially of elevations with respect to “sea level,” but Earth’s seas are actually not level. “The sea level is varying from location to location,” says Laura Sanchez, a geodesist at the Technical University of Munich in Germany. (Geodesists study our planet’s shape, orientation, and gravitational field.) While the two teams knew about the 27-centimeter difference, they mixed up which side was higher. Ultimately, Germany lowered its side to complete the bridge. 

To prevent such costly construction errors, in 2015 scientists in the International Association of Geodesy voted to adopt the International Height Reference Frame, or IHRF, a worldwide standard for elevation. It’s the third-dimensional counterpart to latitude and longitude, says Sanchez, who helps coordinate the standardization effort. 

Now, a decade after its adoption, geodesists are looking to update the standard—by using the most precise clock ever to fly in space.

That clock, called the Atomic Clock Ensemble in Space, or ACES, launched into orbit from Florida last month, bound for the International Space Station. ACES, which was built by the European Space Agency, consists of two connected atomic clocks, one containing cesium atoms and the other containing hydrogen, combined to produce a single set of ticks with higher precision than either clock alone. 

Pendulum clocks are only accurate to about a second per day, as the rate at which a pendulum swings can vary with humidity, temperature, and the weight of extra dust. Atomic clocks in current GPS satellites will lose or gain a second on average every 3,000 years. ACES, on the other hand, “will not lose or gain a second in 300 million years,” says Luigi Cacciapuoti, an ESA physicist who helped build and launch the device. (In 2022, China installed a potentially stabler clock on its space station, but the Chinese government has not publicly shared the clock’s performance after launch, according to Cacciapuoti.) 

From space, ACES will link to some of the most accurate clocks on Earth to create a synchronized clock network, which will support its main purpose: to perform tests of fundamental physics. 

But it’s of special interest for geodesists because it can be used to make gravitational measurements that will help establish a more precise zero point from which to measure elevation across the world.

Alignment over this “zero point” (basically where you stick the end of the tape measure to measure elevation) is important for international collaboration. It makes it easier, for example, to monitor and compare sea-level changes around the world. It is especially useful for building infrastructure involving flowing water, such as dams and canals. In 2020, the international height standard even resolved a long-standing dispute between China and Nepal over Mount Everest’s height. For years, China said the mountain was 8,844.43 meters; Nepal measured it at 8,848. Using the IHRF, the two countries finally agreed that the mountain was 8,848.86 meters. 

ESA-T. PEIGNIER

To create a standard zero point, geodesists create a model of Earth known as a geoid. Every point on the surface of this lumpy, potato-shaped model experiences the same gravity, which means that if you dug a canal at the height of the geoid, the water within the canal would be level and would not flow. Distance from the geoid establishes a global system for altitude.

However, the current model lacks precision, particularly in Africa and South America, says Sanchez. Today’s geoid has been built using instruments that directly measure Earth’s gravity. These have been carried on satellites, which excel at getting a global but low-resolution view, and have also been used to get finer details via expensive ground- and airplane-based surveys. But geodesists have not had the funding to survey Africa and South America as extensively as other parts of the world, particularly in difficult terrain such as the Amazon rainforest and Sahara Desert. 

To understand the discrepancy in precision, imagine a bridge that spans Africa from the Mediterranean coast to Cape Town, South Africa. If it’s built using the current geoid, the two ends of the bridge will be misaligned by tens of centimeters. In comparison, you’d be off by at most five centimeters if you were building a bridge spanning North America. 

To improve the geoid’s precision, geodesists want to create a worldwide network of clocks, synchronized from space. The idea works according to Einstein’s theory of general relativity, which states that the stronger the gravitational field, the more slowly time passes. The 2014 sci-fi movie Interstellar illustrates an extreme version of this so-called time dilation: Two astronauts spend a few hours in extreme gravity near a black hole to return to a shipmate who has aged more than two decades. Similarly, Earth’s gravity grows weaker the higher in elevation you are. Your feet, for example, experience slightly stronger gravity than your head when you’re standing. Assuming you live to be about 80 years old, over a lifetime your head will age tens of billionths of a second more than your feet. 

A clock network would allow geodesists to compare the ticking of clocks all over the world. They could then use the variations in time to map Earth’s gravitational field much more precisely, and consequently create a more precise geoid. The most accurate clocks today are precise enough to measure variations in time that map onto centimeter-level differences in elevation. 

“We want to have the accuracy level at the one-centimeter or sub-centimeter level,” says Jürgen Müller, a geodesist at Leibniz University Hannover in Germany. Specifically, geodesists would use the clock measurements to validate their geoid model, which they currently do with ground- and plane-based surveying techniques. They think that a clock network should be considerably less expensive.

ACES is just a first step. It is capable of measuring altitudes at various points around Earth with 10-centimeter precision, says Cacciapuoti. But the point of ACES is to prototype the clock network. It will demonstrate the optical and microwave technology needed to use a clock in space to connect some of the most advanced ground-based clocks together. In the next year or so, Müller plans to use ACES to connect to clocks on the ground, starting with three in Germany. Müller’s team could then make more precise measurements at the location of those clocks.

These early studies will pave the way for work connecting even more precise clocks than ACES to the network, ultimately leading to an improved geoid. The best clocks today are some 50 times more precise than ACES. “The exciting thing is that clocks are getting even stabler,” says Michael Bevis, a geodesist at Ohio State University, who was not involved with the project. A more precise geoid would allow engineers, for example, to build a canal with better control of its depth and flow, he says. However, he points out that in order for geodesists to take advantage of the clocks’ precision, they will also have to improve their mathematical models of Earth’s gravitational field. 

Even starting to build this clock network has required decades of dedicated work by scientists and engineers. It took ESA three decades to make a clock as small as ACES that is suitable for space, says Cacciapuoti. This meant miniaturizing a clock the size of a laboratory into the size of a small fridge. “It was a huge engineering effort,” says Cacciapuoti, who has been working on the project since he began at ESA 20 years ago. 

Geodesists expect they’ll need at least another decade to develop the clock network and launch more clocks into space. One possibility would be to slot the clocks onto GPS satellites. The timeline depends on the success of the ACES mission and the willingness of government agencies to invest, says Sanchez. But whatever the specifics, mapping the world takes time.

The world’s biggest space-based radar will measure Earth’s forests from orbit

Forests are the second-largest carbon sink on the planet, after the oceans. To understand exactly how much carbon they trap, the European Space Agency and Airbus have built a satellite called Biomass that will use a long-prohibited band of the radio spectrum to see below the treetops around the world. It will lift off from French Guiana toward the end of April and will boast the largest space-based radar in history, though it will soon be tied in orbit by the US-India NISAR imaging satellite, due to launch later this year.

Roughly half of a tree’s dry mass is made of carbon, so getting a good measure of how much a forest weighs can tell you how much carbon dioxide it’s taken from the atmosphere. But scientists have no way of measuring that mass directly. 

“To measure biomass, you need to cut the tree down and weigh it, which is why we use indirect measuring systems,” says Klaus Scipal, manager of the Biomass mission. 

These indirect systems rely on a combination of field sampling—foresters roaming among the trees to measure their height and diameter—and remote sensing technologies like lidar scanners, which can be flown over the forests on airplanes or drones and used to measure treetop height along lines of flight. This approach has worked well in North America and Europe, which have well-established forest management systems in place. “People know every tree there, take lots of measurements,” Scipal says. 

But most of the world’s trees are in less-mapped places, like the Amazon jungle, where less than 20% of the forest has been studied in depth on the ground. To get a sense of the biomass in those remote, mostly inaccessible areas, space-based forest sensing is the only feasible option. The problem is, the satellites we currently have in orbit are not equipped for monitoring trees. 

Tropical forests seen from space look like green plush carpets, because all we can see are the treetops; from imagery like this, we can’t tell how high or thick the trees are. Radars we have on satellites like Sentinel 1 use short radio wavelengths like those in the C band, which fall between 3.9 and 7.5 centimeters. These bounce off the leaves and smaller branches and can’t penetrate the forest all the way to the ground. 

This is why for the Biomass mission ESA went with P-band radar. P-band radio waves, which are about 10 times longer in wavelength, can see bigger branches and the trunks of trees, where most of their mass is stored. But fitting a P-band radar system on a satellite isn’t easy. The first problem is the size. 

“Radar systems scale with wavelengths—the longer the wavelength, the bigger your antennas need to be. You need bigger structures,” says Scipal. To enable it to carry the P-band radar, Airbus engineers had to make the Biomass satellite two meters wide, two meters thick, and four meters tall. The antenna for the radar is 12 meters in diameter. It sits on a long, multi-joint boom, and Airbus engineers had to fold it like a giant umbrella to fit it into the Vega C rocket that will lift it into orbit. The unfolding procedure alone is going to take several days once the satellite gets to space. 

Sheer size, though, is just one reason we have generally avoided sending P-band radars to space. Operating such radar systems in space is banned by International Telecommunication Union regulations, and for a good reason: interference. 

ESA-CNES-ARIANESPACE/OPTIQUE VIDéO DU CSG–S. MARTIN

“The primary frequency allocation in P band is for huge SOTR [single-object-tracking radars] Americans use to detect incoming intercontinental ballistic missiles. That was, of course, a problem for us,” Scipal says. To get an exemption from the ban on space-based P-band radars, ESA had to agree to several limitations, the most painful of which was turning the Biomass radar off over North America and Europe to avoid interfering with SOTR coverage.

“This was a pity. It’s a European mission, so we wanted to do observations in Europe,” Scipal says. The rest of the world, though, is fair game.

The Biomass mission is scheduled to last five years. Calibration of the radar and other systems is going to take the first five months. After that, Biomass will enter its tomography phase, gathering data to create detailed biomass maps of the forests in India, Australia, Siberia, South America, Africa—everywhere but North America and Europe. “Tomography will work like a CT scan in a hospital. We will take images of each area from various different positions and create the 3D map of the forests,” Scipal says. 

Getting full, global coverage is expected to take 18 months. Then, for the rest of the mission, Biomass will switch to a different measurement method, capturing one full global map every nine months to measure how the condition of our forests changes over time. 

“The scientific goal here is to really understand the role of forests in the global carbon cycle. The main interest is the tropics because it’s the densest forest which is under the biggest threat of deforestation and the one we know the least about,” Scipal says.

Biomass is going to provide hectare-scale-resolution 3D maps of those tropical forests, including everything from the tree heights to ground topography—something we’ve never had before. But there are limits to what it can do. 

“One drawback is that we won’t get insights into seasonal deviations in forest throughout the year because of the time it takes for Biomass to do global coverage,” says Irena Hajnsek, a professor of Earth observation at ETH Zurich, who is not involved in the Biomass mission. And Biomass is still going to leave some of our questions about carbon sinks unanswered.

“In all our estimations of climate change, we know how much carbon is in the atmosphere, but we do not know so much about how much carbon is stored on land,” says Hajnsek. Biomass will have its limits, she says, since significant amounts of carbon are trapped in the soil in permafrost areas, which the mission won’t be able to measure.

“But we’re going to learn how much carbon is stored in the forests and also how much of it is getting released due to disturbances like deforestation or fires,” she says. “And that is going to be a huge contribution.”