Efficient, Hi-Res IR Cameras

A new camera expands Goddard’s legacy of broad spectrum infrared imagers by capturing more infrared wavelengths in an easy-to-reproduce format appropriate for many science applications.

Researchers using Goddard’s Type II Strained-Layer Superlattice (SLS) detectors say the new camera will be able to resolve molecular spectral signatures in the infrared fingerprint region (approximately 2 to 14 microns in wavelength) with accuracy and resolution.

The expanded range enables a variety of science investigations: measuring atmospheric trace gases, sea ice properties, infrared ocean color, analyzing vegetation, identifying and characterizing wildfires, mineral surveys, and studying how Earth’s atmosphere stores and emits heat.

The camera provides both high spectral resolution and sufficient image sharpness for these investigations, Principal Investigator Dr. Tilak Hewagama said.

“When you start looking at molecular compositions in the atmosphere,” he said, “then you need to have higher spectral resolution to resolve molecules’ signatures as seen in their reflected sunlight and thermal emission.”

His current project builds on a strong Goddard Internal Research and Development heritage. The innovative SLS detectors were developed by Murzy Jhabvala and his engineering team. Hewagama’s spectrometer builds on the successful Compact Thermal Imager (CTI) that flew on the International Space Station (CuttingEdge, Summer 2018, Page 19), and was also based on the SLS detector. CTI yielded 15 million images with a range of earth scenes at 40-meter spatial resolution in two spectral bands.

The new instrument's hyperspectral capabilities take advantage of the SLS detectors' resolution and their dependability, Hewagama said. “We can reliably manufacture those detectors with their proven performance and adaptability.”

These cameras operate at cryogenic temperatures using compact, low-power, commercial coolers and are cost efficient compared to competing mercury- cadmium-telluride IR sensors. The SLS-based cameras can also be adapted with a variety of gratings and filters to cater to specific missions.

Hewagama is working with researchers including Jhabvala, Don Jennings, and Emily Kan to build the new spectrometer in close collaboration with Goddard Earth scientists Doug Morton, Luke Oman, Dong Wu, and others. The current project also builds on the Goddard-developed Thermal Infrared Composite Imaging Spectrometer (TIRCIS) by Planetary Scientist Terry Hurford.

Enabling high resolution spectroscopy out to longer wavelengths using SLS can bring the sensor’s resolvingn capabilities to benefit crucial science investigations in infrared, said Goddard research scientist Luke Oman, from studying the ionized upper atmosphere, or aeronomy, to geology to climate studies.

“When you have finer spectral resolution,” Oman said, “it becomes easier to separate carbon dioxide from ozone while also enabling measurement of concentrations of different trace gases in the atmosphere. Those trace gasses are important for looking at changes over time and understanding processes going on in the atmosphere. It’s often very subtle changes – 10s of parts per billion can be very important. That’s what you need the higher spectral resolution to confirm.”

The broad-spectrum camera also allows scientists to see the difference between sunlight reflected off an object or gas molecule in visible and nearinfrared light, and thermal radiation emitted by that source, typically in longer-wavelength infrared. This helps improve scientists’ understanding of solar heating and other changes in the environment, Hewagama said.