All light that goes through the atmosphere gets distorted. “Think about when you’re driving in summer on the highway. It kind of seems twinkling and wet in the distance,” said Miranda van Iersel, assistant professor of electro-optics and photonics. “That kind of effect is what I study.”
This past summer, van Iersel conducted an experiment with a group of undergraduate and graduate students at John Bryan State Park Observatory.
The team used a weather balloon to measure atmospheric turbulence at different heights. After inflating the balloon and elevating it 30 meters in the air, they recorded temperature data for 30 minutes.
Once time was up, the group brought the balloon down 5 meters and repeated recording data for another 30 minutes. They continued this process for a few additional height levels. “Turbulence in the air changes with height above the ground,” said van Iersel. This turbulence causes distortions of a light beam and affects imaging, as well as optical communication applications.
Current models help to correct for this distortion, but do not take into account the environment. Therefore, the models predict the same outcome regardless of whether the source is near water or in a forest, a city or a field. “But we all know that in the city there’s a lot of concrete that soaks up the heat, which causes more turbulence than in an open grass field.”
To study how the environment affects light, van Iersel was awarded a three-year grant from the Air Force Office of Scientific Research. For this study, van Iersel will add the use of a drone and a grid of LED lights to measure the amount of turbulence in the atmosphere at different heights as well as the distortion on the light beam.
While the weather balloon method recorded temperatures, the drone method will use images of light from the LED grid. The distance between each light on the grid is known and can be used to calculate how much the light was distorted when propagating between the source and the camera on the drone.
Using both the weather balloon and drone methods, van Iersel plans to combine and compare the results. “The aim will be to update the models to include the environment.”