TIR Remote Sensing

Snapshot Geology

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By Jasmine Blennau

Deanne Rogers holds her digital camera with two hands as she looks at the screen, slowly rotating until she finds the picture she wants. If she were anywhere else, she would seem like an average photographer. But standing on Mount Kilauea’s cooled lava flows, Rogers is there strictly for science, and what she’s holding is not just any camera.

It uses infrared light, or heat energy, to map the mineral components of a given area of a surface. The screen shows the 1974 flow as a rainbow of colors. Her modifications of an off-the-shelf Forward Looking Infrared (FLIR) T640 thermal imaging camera produced a prototype for equipment that might one day make it to the Moon.

With the help of the Andover Corporation in New Hampshire, Rogers, a geoscientist at Stony Brook University, designed custom filters that would allow the camera to take in different wavelengths of light.
“Just think of it like a strainer,” Rogers said. “You want to strain some pasta, you’ve got to let the water through, but let the pasta stay. The filters are letting specific wavelengths of light through, and blocking all the other ones.”

By using custom filters one at a time and then layering the different images, Rogers enabled the camera to produce what is called a multispectral image. It’s the accumulation of many spectral images that shows a larger spectrum of wavelengths of light than a single image.

Meet the team

Deanne Rogers

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Gen Ito

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Marcie Yant

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Rogers and two of her graduate students, Gen Ito and Marcie Yant, made up the thermal infrared team—TIR—on the RIS4E trip to Hawaii. On the simulated extra-vehicular activities (EVAs), Team TIR took spectral images of potential rock samples to help the crew decide which rocks to collect.

Choosing a variety of samples is crucial to returning home with materials that can provide the most information about an area. The TIR team can tell which areas of a site are more likely to have rocks with different compositions than those around them by looking at which areas are warmer or cooler than their surroundings. Those that stand out from the rest are likely to be more interesting to examine.

Rogers was happy with the outcrop she saw on the screen. It had potential for a variety of samples. Ito and Yant began unpacking the equipment needed for the imaging process. Ito took out a standard black tripod and clicked the camera into place.

He and Rogers had practiced taking images at home and on previous fieldwork in Hawaii, but it was Yant’s first time in the lava fields with the team. She set up three square panels, one black, one white, and one aluminum foil, in the distance near the potential samples that Rogers eyed. The panels are calibration targets that have different temperatures.

The black target is heated with a battery at a constant temperature while the aluminum foil and the white remain neutral with the environment. The temperatures of these calibration targets will later be used to convert the colors seen in the spectral image into usable measures of temperature.

The aluminum foil target is used to measure the constant radiance from the atmosphere. Everything can absorb and emit radiation in the form of heat. For example, the human body gives off heat naturally and also absorbs heat from the sun. Because atmospheric radiance reflects off rocks, the aluminum foil target is used to get the radiance of the atmosphere so that it can be subtracted from the total heat signal from the rocks.

Next Rogers dropped coin-sized circular mirrors around the site with the reflective side facing the camera. Ito zoomed in and out until he found the sweet spot where he could see the samples, the targets and the mirrors. All are needed for the imaging process. He will take regular visible light digital images of the site, and thermal infrared images at different wavelengths. Later the little mirrors will be used as markers to help align the images perfectly to create the multispectral image.

The filters were kept in a briefcase where they were specially protected in foam and individual boxes. Yant carefully slid the cloth-covered filter out of its labeled box and handed it to Ito, who attached it to the lens. Each individual filter is exposed only for a short time and a few shots. With each click of the camera Ito called out the image number and Rogers became the note taker, writing down the filter being used and its corresponding image numbers.

After the photos were taken it was time to collect the samples. As the group carefully bagged the rocks they chose, they placed aluminum foil balls where the samples were and took another round of images. The photos with the foil balls would help the scientists remember where each sample came from.

Back at Stony Brook, Rogers, Ito and Yant will perform detailed geochemical and mineralogical analyses on the samples and compare the results against how different the samples seemed to be according to the thermal images. Ultimately their findings will analyze how useful the thermal data from the camera was in making sampling decisions.

Using this camera in space would allow astronauts without geological training to identify rocks that differ from their surroundings. It could also be applied to unmanned space exploration if it were attached to a rover.

“It could be used strategically, on the fly, where you take it out and point it at a scene and it spits out an image that says, ‘Take this rock,’ ” Rogers said. “Or it could be used as a documentation tool, where they [astronauts] start acquiring data but don’t necessarily use it as a guide to collect samples but instead can document the different rocks.”

Although the future of the camera’s purpose in spaceflight exploration is unknown, the team will continue to test its abilities and collect data that can be used by other geologists in the future.