When most people think about satellites, they picture scientists peering into space to unravel its secrets. But for Knut Stamnes, professor in the Department of Physics at Stevens Institute of Technology, those satellites are tools that can help understand our own planet.
Scientists use remote sensing to gather valuable information about Earth based on how light scatters as it travels from the sun to Earth and then bounces back to the satellite. But the way light scatters as it passes through layered material like the atmosphere is complicated, and current algorithms aren’t sufficient to address those complications. That limits how accurately scientists can interpret the data. Stamnes recently received a grant of $450,055 from NASA for his project “Laser Beam (Lidar) Propagation in the Atmosphere-Ocean System in Support of Active Remote Sensing from Space” to solve that problem.
Building Algorithms to Better Understand Climate Change
Stamnes has focused his career on constructing algorithms that help scientists more accurately measure and model the way energy reflects from Earth. In fact, his 1988 paper in Applied Optics introduced a new mathematical algorithm for measuring how radiation transfers through layered material—and by 2012, it was recognized as the most cited paper in the journal.
In Stamnes’ Light and Life Laboratory at Stevens, researchers use the algorithms to study the colors of the coastal and open areas of the oceans and the physical properties of snow and ice—and they hope to develop ways to monitor the health of coral reefs from space.
“We are basically trying to come up with techniques to learn as much as we can from information that you receive from satellites in space looking at the earth,” said Stamnes. “We are trying to receive information that would be useful for addressing the climate problem in terms of what aerosols are in the atmosphere and what is in the ocean and so on. That's part of the puzzle if you want to understand the climate problem.”
The Scattering Problem
Stamnes’ recent grant will fund his work to tackle a problem that’s been troubling the scientific community for a long time. The current algorithms used in remote sensing assume that light bounces right back to the satellite sensors—but the path back to the satellite isn’t direct as the light travels through the layered atmosphere.
“The assumption is that you only have one scattering event—so-called single scattering—but if this layer is thick enough, there will be more than one scattering event. The light will bounce around before it turns back to the sensor,” Stamnes explained. “So, the question is, ‘how do you correct for this multiple scattering?’ That's a problem that has been vexing the community for a long time, and we will be proposing a new way of looking at that to try to mitigate that problem or actually make use of it.”
To test the solution he comes up with, Stamnes will run his algorithm on satellite data from the Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, which has been studying how air particles affect Earth’s weather and climate since 2006.
Turning to Tissues in Cancer Patients
An algorithm that properly addresses multiple scattering would be a big deal for researchers studying a broad range of questions that rely on remote sensing, but Stamnes thinks it could make a difference for cancer patients, too. Along with his brother, he formed a company in Norway that harnesses the same principles of light scattering to detect cancer in human tissue.
“We can use the same algorithm that we use for modeling the atmosphere and the ocean to model what's coming back from the skin,” he explained. “If we have an instrument to measure the spectral composition of the light that comes back from the tissue, we can use that to try to infer what's in the tissue and whether a lesion is malignant or benign.”
So far, the company holds several patents and hopes to secure funding to work toward FDA approval for the instrument.
Stamnes says his work is driven by curiosity and the desire to solve problems, but the thing he’s most proud of is his teaching career at Stevens and the opportunity that’s given him to guide so many Ph.D. students who have gone on to have successful careers. “I'm basically an educator,” he said. “I do research, of course, but I work for a university, so I like this interaction with students, many of whom are smarter than me—because that keeps you on your toes…and that's very satisfying to me.”
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