For more than 15 years, Georgia Tech has provided the City of Atlanta with the foundational data and insight that shape how the city tracks, understands, and plans for changes in its tree canopy. The latest cycle of this research — delivered through the Center for Urban Resilience and Analytics (CURA) — continues that legacy by offering a high-resolution, citywide canopy assessment using satellite imagery and field validation.

The assessment, funded by the city’s Tree Recompense Fund, uses advanced remote sensing tools such as WorldView-2 satellite data and a random forest classification model to categorize land into three land cover types. These include tree canopy, non-tree vegetation (grass, shrubs, and low lying vegetation) and non-vegetation (water, pervious surface). The methodology delivers a detailed spatial picture of land cover across the city.

“This is simply a tool in their planning arsenal,” said Anthony Giarrusso, who has led every canopy study since 2008. “Before they did any of this work in 2008, everything was anecdotal. It was reactionary.”

The new study is not advocacy — it’s information. Giarrusso emphasized that while researchers stay neutral in the politics of urban growth and conservation, their work equips city leaders with science-based knowledge to make more effective zoning and planning decisions.

In addition to mapping existing conditions, the Georgia Tech team developed the Potential Planting Index (PPI), a scalable tool that identifies where tree planting is physically possible based on current land cover. The tool quantifies the difference between tree canopy and non-tree vegetation, indicating zones with restoration potential.

Another key insight is the challenge of interpreting canopy change without understanding land use patterns. “It gives you a false sense of stability if you don’t understand the underlying land use,” said Giarrusso. “You might see canopy regrowth on paper, but that land could be cleared again tomorrow.” He explained that this false signal is particularly common in stalled development sites: “We saw a lot of properties where trees had regrown after initial clearing, but it was temporary and monoculture, low quality canopy. Several of those areas were cleared again for construction later.”

Giarrusso pointed to these “loss-gain-loss” cycles as one of the more misleading aspects of tree canopy analysis without strong land use context. “Some of them were pipe farms — land cleared for development with infrastructure like water and sewer lines installed, but then construction never happened. So trees grow back, and you get a canopy gain that doesn’t last and is nowhere near the quality of the trees originally cleared.”

He stressed that policymakers need to consider the permanence of canopy when using the data. “If it’s just going to be cleared again in two years, it’s not really a gain. That’s why long-term tracking and land use analysis together are so important.”

The city has incorporated these tools into broader planning efforts, including zoning reform and tree ordinance revisions. The research supports recommendations such as restricting full lot clearing in certain zoning categories and adjusting setback or lot coverage limits to better preserve existing canopy.

Giarrusso underscored the urgency of protecting larger, intact forested tracts. “If you can see it from space and it’s still forest — save it,” he said. “Once it’s cleared, you don’t get it back.”

From the humble beginnings of the three-wheeled Benz Patent-Motorwagen in 1886, the automobile has been a continuous story of technological progress. Each era has seen cars push the boundaries of innovation, evolving from early mechanical systems into sophisticated, computer-driven machines.

We’re now in a new generation of automobiles, where roadways are increasingly shared by electric vehicles (EVs) and autonomous vehicles (AVs). 

EVs are projected to dominate global car sales by 2030, according to an RMI report. Meanwhile, AVs are gradually entering the mainstream, with 37 percent of new passenger cars expected to be equipped with advanced driver-assistance technologies by 2035, according to McKinsey & Company.

Georgia Tech School of Electrical and Computer Engineering (ECE) researchers are at the forefront of advanced automotive technologies, working on everything from electric engines and computer vision, to modernizing the power grid to support EV charging.

Given current advancements and future possibilities, ECE is helping bring the future car into view, though many surprises and uncertainties remain. Learn what's on the horizon on the ECE Newspage.

In June, the Strategic Energy Institute (SEI) hosted the Energy and National Security Summer Cohort Meeting that convened seed grant awardees from the Energy and National Security Initiative. A partnership between SEI and the Georgia Tech Research Institute (GTRI), the initiative provides research support through a seed grant program that launched last summer.

“As national security needs rapidly evolve, Georgia Tech is leveraging its research ecosystem and seed funding programs to accelerate the development of transformational technologies and strategies that strengthen national resilience,” said Christine Conwell, interim executive director of SEI. “We designed this seed grant program to tackle pressing national security priorities of today, such as threats to the grid, nuclear security, supply chain resilience, and renewable integration.”

The event began with an introduction from John Tien, SEI distinguished external fellow, professor of the practice, and former deputy secretary for the Department of Homeland Security, who addressed the evolving and multifaceted challenges facing energy, national security, and policy today. Tien’s talk emphasized the importance of early, strategic research investments in driving sustainable progress and long-term solutions. 

The seed grant awardees then presented the initial progress of their research projects through lightning talks and a Q&A session. The research projects included:

• Energy Infrastructure Security and Risk Assessment Through Interactive Wargaming.
• Evaluating Energy Storage Materials, Supplies, and Systems in the Context of National Security Requirements.
• Nanostructured Sensors for Monitoring of Nuclear Fuel Cycle.
• Resilient Critical Infrastructures via Provable Secure Control Algorithms.
• Robust Energy Systems Planning by Way of Novel Systems Engineering (RESPoNSE).
• SPARC: Severe-Weather Predictive Analytics and Resilient Communication.
• The Strategic Mineral Economy: Challenges and Opportunities for Critical Resources.

“That critical intersection between energy and national security is where both risk and opportunity lie. To mitigate those risks and take advantage of the opportunities, our project teams have developed research topic areas that align with the U.S. Department of Energy's nine pillars for American energy dominance and security, as well as ongoing U.S. Department of Defense priorities,” said Tien.

The meeting showcased Georgia Tech’s collaborative and forward-looking research at the intersection of energy and national security, aimed at shaping a more secure and resilient energy future. 

Written by: Katie Strickland & Priya Devarajan

Researchers at Georgia Tech have developed a new approach to cancer imaging and therapy.

The study, led by Costas Arvanitis, associate professor in the George W. Woodruff School of Mechanical Engineering and the Wallace H. Coulter Department of Biomedical Engineering, explores a noninvasive method for tracking immune cells in real time using ultrasound. The study was recently published in the journal Nature Communications.

Read the full story on the George W. Woodruff School of Mechanical Engineering website.

As more satellites launch into space, the satellite industry has sounded the alarm about the danger of collisions in low Earth orbit (LEO).  What is less understood is what might happen as more missions head to a more targeted destination: the moon.

According to The Planetary Society, more than 30 missions are slated to launch to the moon between 2024 and 2030, backed by the U.S., China, Japan, India, and various private corporations. That compares to over 40 missions to the moon between 1959 and 1979 and a scant three missions between 1980 and 2000.

A multidisciplinary team at Georgia Tech has found that while collision probabilities in orbits around the moon are very low compared to Earth orbit, spacecraft in lunar orbit will likely need to conduct multiple costly collision avoidance maneuvers each year. The Journal of Spacecraft and Rockets published the Georgia Tech collision-avoidance study in March.

“The number of close approaches in lunar orbit is higher than some might expect, given that there are only tens of satellites, rather than the thousands in low Earth orbit,” says paper co-author Mariel Borowitz, associate professor in the Sam Nunn School of International Affairs in the Ivan Allen College of Liberal Arts.

Borowitz and other researchers attribute these risky approaches in part to spacecraft often choosing a limited number of favorable orbits and the difficulty of monitoring the exact location of spacecraft that are more than 200,000 miles away.

“There is significant uncertainty about the exact location of objects around the moon. This, combined with the high cost associated with lunar missions, means that operators often undertake maneuvers even when the probability is very low — up to one in 10 million,” Borowitz explains. 

The Georgia Tech research is the first published study showing short- and long-term collision risks in cislunar orbits. Using a series of Monte Carlo simulations, the researchers modeled the probability of various outcomes in a process that cannot be easily predicted because of random variables. 

“Our analysis suggests that satellite operators must perform up to four maneuvers annually for each satellite for a fleet of 50 satellites in low lunar orbit (LLO),” said one of the study’s authors, Brian Gunter, associate professor in the Daniel Guggenheim School of Aerospace Engineering. 

He noted that with only 10 satellites in LLO, a satellite might still need a yearly maneuver. This is supported by what current cislunar operators have reported. 

Favored Orbits

Most close encounters are expected to occur near the moon’s equator, an intersection point between the orbit planes of commonly used “frozen” and low lunar orbits, which are preferred by many operators. Other possible regions of congestion can occur at the Lagrangian points, or regions where the gravitational forces of Earth and the moon balance out. Stable orbits in these regions have names such as Halo and Lyapunov orbits. 

“Lagrangian points are an interesting place to put a satellite because it can maintain its orbit for long periods with very little maneuvering and thrusting. Frozen orbits, too. Anywhere outside these special areas, you have to spend a lot of fuel to maintain an orbit,” he said.

Gunter and other researchers worry that if operators aren’t coordinated about how they plan lunar missions, opportunities for collision will increase in these popular orbits.

“The close approaches were much more common than I would have intuitively anticipated,” says lead study author Stef Crum.

The 2024 graduate of Georgia Tech’s aerospace engineering doctoral program notes that, considering the small number of satellites in lunar orbit, the need for multiple maneuvers was “really surprising.”

Crum, who is also co-founder of Reditus Space, a startup he founded in 2024 to provide reusable orbital re-entry services, adds that the cislunar environment is so challenging because “it’s incredibly vast.”

His research also examines ways to improve object monitoring in cislunar space. Maintaining continuous custody of these objects is difficult because a target’s position must be monitored over the entire duration of its trajectory. 

“That wasn’t feasible for translunar orbits, given the vast volume of cislunar orbit, which stretches multiple millions of kilometers in three dimensions,” he says.

By estimating a satellite’s orbit using observed data and constraining the presumed location and direction of the satellite, rather than continuous tracking (a process known as continuous custody), Crum greatly simplified the process. 

“You no longer need thousands of satellites or a set of enormous satellites to cover all potential trajectories,” he explains. “Instead, one or a few satellites are required, and operators can lose custody for a time as long as the connection is reacquired later.”

Since the team started their study, there has been a lot of interest in the moon and cislunar activity — both NASA and China’s National Space Administration are planning to send humans to the moon. In the last two years, India, Japan, the U.S., China, Russia, and four private companies have attempted missions to the moon. 

Why the Moon

Spacefaring nations’ intense interest in exploring the lunar surface comes as no surprise given that the moon offers a variety of resources, including solar power, water, oxygen, and metals like iron, titanium, and uranium. It also contains Helium-3, a potential fuel for nuclear fusion, and rare earth metals vital for modern technology. With the recent discovery of water ice, it could be a plentiful source for rocket fuel that can be created from liquifying oxygen and hydrogen needed to launch deep space missions to destinations like Mars. In February, Georgia Tech announced that researchers have developed new algorithms to help Intuitive Machines’ lunar lander find water ice on the moon.

Commercial space companies like Axiom Space and Redwire Space, as well as space agencies, are actively building lunar infrastructure, from satellite constellations to orbital platforms to support communication, navigation, scientific research, and eventually space tourism. 

A key project involves the Lunar Gateway, a joint venture of NASA and international space agencies like ESA, JAXA, and CSA, as well as commercial partners. Humanity’s first space station around the moon will serve as a central hub for human exploration of the moon and is considered a stepping stone for future deep space missions.

Getting Ahead of a Gold Rush to the Moon

All this activity underscores the urgency to get out in front of potential crowding issues — something that hasn’t occurred in LEO, where near-miss collisions, or conjunctions, are frequent. LEO, which is 100 to 1,200 miles above the Earth’s surface, is host to more than 14,000  satellites and 120 million pieces of debris from launches, collisions, and wear and tear, reports Reuters.

“Using the near-Earth environment as an example, the space object population has gone from approximately 6,000 active satellites in the early 2020s to an anticipated 60,000 satellites in the coming decade if the projected number of large satellite constellations currently in the works gets deployed. That poses many challenges in terms of how we can manage that sustainably,” observed Gunter. “If something similar happens in the lunar environment, say if Artemis (NASA’s program to establish the first long-term presence on the moon) is successful and a lunar base is established, and there is discovery of volatiles or water deposits, it could initiate a kind of gold rush effect that might accelerate the number of actors in cislunar space.”

For this reason, Borowitz argues for the need to begin working on coordination, either in the planning of the orbits for future missions or by sharing information about the location of objects operating in lunar orbit. She pointed out that spacecraft outfitted for moon missions are expensive, making a collision highly costly. Also, debris from such a scenario would spread in an unpredictable way, which could be problematic for other objects.

Gunter agreed, noting, “If we’re not careful, we could be putting a lot of things in this same path. We must ensure we build out the cislunar orbital environment in a smart way, where we’re not intentionally putting spacecraft in the same orbital spaces. If we do that, everyone should be able to get what they want and not be in each other’s way.”

Borowitz says some coordination efforts are underway with the UN Committee on the Peaceful Uses of Outer Space and the creation of an action team on lunar activities; however, international diplomacy is a time-consuming process, and it can be a challenge to keep pace with advancements in technology.

She contends that the Georgia Tech study could provide baseline data that “could be helpful for international coordination efforts, helping to ensure that countries better understand potential future risks.”

Gunter and Borowitz say that follow-on research for the team could involve looking into the Lunar Gateway orbit and other special orbits to see how crowded that space will likely get, and then do an end-to-end simulation of these orbits to determine the most effective way to build them out to avoid collision risks. Ultimately, they intend to develop guidelines to help ensure that future space actors headed to the moon can operate safely.

The Laser Interferometer Gravitational-Wave Observatory (LIGO)’s LIGO-Virgo-KAGRA (LVK) collaboration has detected an extremely unusual binary black hole merger — a phenomenon that occurs when two black holes are pulled into each other's orbit and combine. Announced yesterday in a California Institute of Technology press release, the binary black hole merger, GW231123, is the largest ever detected with gravitational waves.

Before merging, both black holes were spinning exceptionally fast, and their masses fell into a range that should be very rare — or impossible. 

“Most models don't predict black holes this big can be made by supernovas, and our data indicates that they were spinning at a rate close to the limit of what’s theoretically possible,” says Margaret Millhouse, a research scientist in the School of Physics who played a key role in the research. “Where could they have come from? It raises interesting questions.”

A binary black hole merger absorbs characteristics from both of the contributors, she adds. “As a result, this is not only the most massive binary black hole ever seen but also the fastest-spinning binary black hole confidently detected with gravitational waves.”

“GW231123 is a record-breaking event,” says School of Physics Professor Laura Cadonati, who has been a member of the LIGO Scientific Collaboration since 2002. “LIGO has been observing the cosmos for 10 years now. This discovery underscores that there is still so much that this instrument can help us learn.”

A Cosmic View

The findings challenge current theories on how smaller black holes form, says School of Physics Assistant Professor and LIGO collaborator Surabhi Sachdev. Smaller black holes are the result of supernovae: dying and collapsing stars. During that collapse, explosions can tear apart or eject part of the star’s mass — limiting the size of the black hole that forms.

“Black holes from supernovae can weigh up to about 60 times the mass of our Sun,” she says. “The black holes in this merger were likely the mass of hundreds of suns.”

Because of its size, GW231123 also allowed the team to study the merger in unprecedented detail. “LIGO has observed scores of black hole mergers,” says Cadonati. “Of these, GW231123 has provided us with the clearest view of the ‘grand finale’ of a merger thus far. This adds a new clue to solve the puzzle that are black holes, including their origins and properties.”

“While we saw that our expectations matched the data, the extreme nature of this event pushed our models to their limits,” Millhouse adds. “A massive, highly spinning system like this will be of interest to researchers who study how binary black holes form.”

Decoding a Split-Second Signal

Millhouse and School of Physics Postdoctoral Fellow Prathamesh Joshi used Einstein’s equations for general relativity to confirm LIGO’s detections.

To find black holes, LIGO measures distortions in spacetime — ripples that are created when two black holes collide. These patterns in gravitational waves can be used to find the signature signal of black hole collisions. 

“In this case, the signal lasted for just one-tenth of a second, but it was very clear,” says Joshi. "Previously, we designed a special study to detect these interesting signals, which accounted for all the unusual properties of such massive systems — and it paid off!”

“To ensure it wasn’t noise, the Georgia Tech team first reconstructed the signal in a model-agnostic way,” Millhouse adds. “We then compared those reconstructions to a model that uses Einstein's equations of general relativity, and both reconstructions looked very similar, which helped confirm that this highly unusual phenomenon was a genuine detection.”

Sachdev says that seeing the signal at both LIGO Observatories — placed in Hanford, Washington and Livingston, Louisiana — was also critical. “These short signals are very hard to detect, and this signal is so unlike any of the other binary black holes that we've seen before,” she says. “Without both detectors, we would have missed it.”

A Decade of Discovery

While the team has yet to determine how the original black holes formed, one theory is that they may have resulted from mergers themselves. “This could have been a chain of mergers,” Sachdev explains. “This tells us that they could have existed in a very dense environment like a nuclear star cluster or an active galactic nucleus.” Their spins provide another clue as spinning is a characteristic usually seen in black holes resulting from a merge.

The team adds that GW231123 could provide clues on how larger black holes are formed — including the mysterious supermassive black holes at the center of galaxies.

“Gravitational wave science is almost a decade old, and we're still making fundamental discoveries,” says Millhouse. “It’s exciting that LIGO is continuing to detect new phenomena,  and this is at the edge of what we've seen thus far. There's still so much we can learn.”

The team expects to update their catalogue of black holes in August 2025, which will provide another window into how this exceptionally heavy black hole might fit into the universe, and what we can continue to learn from it.

 

Funding: The LIGO Laboratory is supported by the U.S. National Science Foundation and operated jointly by Caltech and MIT.