A new, higher-resolution infrared camera equipped with a variety of lightweight filters could study sunlight reflected from Earth’s upper atmosphere and surface, improve wildfire warning, and reveal the molecular composition of other planets.
The cameras use sensitive, high-resolution strained-layer superlattice sensors originally developed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with funding from IRAD (Internal Research and Development).
Their compact design, low mass and adaptability allow engineers like Tilak Hewagama to adapt them to the needs of a wide range of sciences.
“By attaching filters directly to the detector, we eliminate the significant mass of traditional lens and filter systems,” said Hewagama. “This creates a low-mass instrument with a compact focal plane that can now be cooled with smaller, more efficient coolers for infrared detection. Smaller satellites and missions can benefit from their resolution and accuracy.”
Engineer Murzy Jhabvala led initial sensor development at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and is also a leader in today’s filter integration efforts.
Jhabvala also led the Compact Thermal Imager experiment on the International Space Station, which demonstrated how the new sensor technology can survive in space while proving to be a major success for the Earth sciences. More than 15 million images captured in two infrared bands earned inventors Jhabvala and his NASA colleagues Don Jennings and Compton Tucker of Goddard the 2021 Invention of the Year award.
Data from the test provided detailed information about wildfires, enabled a better understanding of the vertical structure of Earth’s clouds and atmosphere, and captured an updraft caused by wind lifting off of Earth’s land structures – a so-called gravity wave.
The groundbreaking infrared sensors use layers of repeating molecular structures to interact with individual photons, or units of light. The sensors detect more wavelengths in the infrared range at higher resolution: 80 meters per pixel from orbit compared to 375 to 1,000 meters possible with current thermal imaging cameras.
The success of these thermal cameras has led to investments by NASA’s Earth Science Technology Office (ESTO), Small Business Innovation and Research, and other programs to further expand their reach and applications.
Jhabvala and NASA’s Advanced Land Imaging Thermal IR Sensor (ALTIRS) team are developing a six-band version for this year’s LiDAR, Hyperspectral, and Thermal Imager (G-LiHT) airborne project. This first-of-its-kind camera will measure surface heat and enable pollution monitoring and high-frame-rate fire observations, he said.
Earth scientist Doug Morton of the NASA Goddard Institute is leading an ESTO project to develop a Compact Fire Imager to detect and predict wildfires.
“We’re not going to see fewer fires, so we’re trying to understand how fires release energy over their life cycle,” Morton said. “That will help us better understand the new nature of fires in an increasingly combustible world.”
CFI will monitor both the hottest fires, which release more greenhouse gases, and cooler, smoldering coals and ash, which produce more carbon monoxide and airborne particles such as smoke and ash.
“These are key factors when it comes to safety and understanding the greenhouse gases released during combustion,” Morton said.
After testing the fire camera in aerial campaigns, Morton’s team plans to equip a fleet of 10 small satellites to provide information about fires worldwide with more images per day.
Combined with next-generation computer models, he said, “this information can help the Forest Service and other fire agencies prevent fires, improve the safety of firefighters on the front lines, and protect the lives and property of people living in the path of fires.”
Exploring clouds on Earth and beyond
Equipped with polarization filters, the sensor can measure how ice particles in clouds in the Earth’s upper atmosphere scatter and polarize light, said Dong Wu, an earth scientist at NASA’s Goddard Institute.
These applications would complement NASA’s PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) mission, Wu said, which released its first light images earlier this month. Both measure the polarization of the orientation of the light wave relative to the direction of travel from different parts of the infrared spectrum.
“The PACE polarimeters monitor visible and short-wave infrared light,” he explained. “The mission will focus on aerosol and ocean color science from daytime observations. At mid- and long-wave infrared wavelengths, the new infrared polarimeter would capture cloud and surface properties from day and nighttime observations.”
In another project, Hewagama is working with Jhabvala and Jennings to incorporate linear variable filters that provide even more detail in the infrared spectrum. The filters reveal the rotation and vibration of atmospheric molecules as well as the composition of the Earth’s surface.
This technology could also be useful for missions to rocky planets, comets and asteroids, said planetary scientist Carrie Anderson. She said they could identify ices and volatile compounds ejected in giant plumes from Saturn’s moon Enceladus.
“They are basically geysers of ice,” she said, “which are naturally cold, but emit light within the detection limits of the new infrared sensor. If we look at the fountains against the background of the sun, we can see their composition and vertical distribution very clearly.”
From Karl B. Hille
NASA Goddard Space Flight Center, Greenbelt, Maryland.