Dr. Azad Hossain didn’t expect to hear from NASA, so when an email from NASA’s Science Systems and Applications Inc. showed up in his inbox, he took a second look.
“I didn’t have any idea,” said Hossain, an environmental geoscientist and associate professor in UTC's Department of Biology, Geology and Environmental Science. “I saw the email come through and I couldn’t understand it. I looked closer and thought, ‘OK, this is interesting. I need to respond.’”
That email turned into a full interview and collaboration that led to Hossain’s research projects being featured as NASA’s Earth Observatory “Image of the Day.” The article, “Building Out Chattanooga,” compares satellite images of Chattanooga from 2001 and 2024 to show how much the city has grown.
Hossain said NASA was intrigued by his use of Landsat, an Earth-observing satellite program launched in the 1970s by NASA and the U.S. Geological Survey. The satellite takes images of the Earth’s surface, documenting its changes over time. There have been nine Landsat satellites launched since the program’s origin, with significant technological improvements with each launch.
Hossain recalled using Landsat data for his master’s thesis in the late ’90s when the technology was slow and expensive. Now, data access is free and near instantaneous.
“Around that time, I was in charge of mapping the Bay of Bengal near the Indian Ocean,” he explained. “It took more than two months to get the image. It was a great day for everyone in our group just to be able to see the image.
“If I tell you now that we need to get a Landsat scene today for Chattanooga, after one hour, I can show you the image.”
Another reason for the selection of Hossain’s research, he said, was Chattanooga’s recent designation as North America’s first National Park City.
“Chattanooga is a unique place. If you look for urbanization, you’ll find it here,” Hossain said.
This is the basis for his research. Hossain came to UTC in 2016 and quickly saw a need for more research into Chattanooga’s growth.
“One of the things when I joined UTC was urbanization, urban canopies, urban heat islands, landslides—but there weren’t any published articles for that,” he said. “If you don’t have anything published, you can’t be part of an effective dialogue.”
With the help of UTC students and colleagues, Hossain began tracking the region’s growth using satellite data. One of his first graduate students, Jonah Hall, co-authored a paper with Hossain that used Landsat to show how Chattanooga changed between 1986 and 2016.
The research also looked at development around major creeks and streams which shows how urbanization can impact local waterways.
“We were able to put numbers to it,” Hossain said. “That was the first time we had data showing how much growth had happened and where.”
Understanding how Chattanooga is growing and how that growth affects the local environment has been a primary goal of Hossain’s research.
“If we know the relationship between this growth and our environment, we’d be able to do it in a sustainable manner and make everybody happy,” he said. “What we’re doing here with Landsat gives us confidence. It gives us the feeling that what we’re doing is important—not just for us, but for others to see and follow. Chattanooga, we call it a smart city. We call it the Scenic City.”
NASA’s Earth Observatory article links to previous research by Hossain and his co-authors. He was quick to credit their role in reaching this point.
“It’s not only for me,” he said of the NASA recognition. “It’s the work I did, but it’s also my students’ work. When I got this article published, I was in class and I told my students, ‘Look, this is public. You can go there and see it.’ I feel pretty good. I’m sure they also feel good.”
Hossain said his goal has always been to do research that’s both useful and accessible, and to help train the next generation to keep it going.
“We like complex research, but sometimes it doesn’t need to be complex,” he said. “We can solve things using simple techniques and understand things better. And that’s what this work shows.”