Image Credits: Ivan Smuk/shutterstock.com
Originally developed for military purposes during the late 1940s, thermal imaging allowed soldiers in combat to see and target opposing forces through the darkest hours of the night or across a smoke-covered battleground1. Since it was introduced during the Korean War, thermal imaging cameras have allowed armies to successfully operate 24 hours a day with an enhanced ability to automatically target, detect, identify, and track threats. Today, thermal imaging applications extend to law enforcement, physiological tests, and vast aeronautic purposes
Converting Heat into Visible Light
Thermal imaging cameras translate thermal energy (heat) into a visible light that projects a particular object or scene of interest2. The electromagnetic spectrum consists of various forms of electromagnetic radiation, the infrared ray being one of them. All forms of electromagnetic radiation emit energy at the speed of light, in the form of electromagnetic waves. Thermal imaging devices detect the waves produced from infrared energy, which is radiated by the motion of atoms and molecules on the surface of an object.
With a wavelength measuring between 0.78-1000 μm, the intensity of infrared energy becomes greater as temperature increases, allowing thermal imaging cameras to convert this energy into a reproducible image. The typical temperatures a thermal imaging camera can measure are between -4ºF to 2200ºF.
Thermal Infrared Technology for NASA's Landsat Program
There are numerous satellite systems circulating space, and the National Aeronautics and Space Administration (NASA) employs several thermal infrared technologies to enhance the ability of these satellites to properly document and capture various parts of our galaxy and beyond. NASA's Landsat program, a significant contributor to understanding environmental changes, through satellite technology, has provided NASA with the longest continuous space-based record of Earth’s land existence3.
Image Credits: NASA/USGS Landsat/Jesse Allen/NASA Earth Observatory/Matthias Baeye et al
In an effort to increase Landsat satellite sensitivity, NASA utilizes the Thermal Infared Sensory (TIRS). Initially added to the satellite mission in response to environmental concerns regarding water consumption, TIRS has become an invaluable tool in determining Landsat data to assess damage from natural disasters, monitor water quality, record population growth, and much more4.
Thermal Infrared Sensory in combination with Quantum Well Infrared Photodetectors
In conjunction with Quantum Well Infrared Photodetectors (QWIPs), TIRS is able to detect long wavelengths of light emitted by the Earth, where the intensity of these wavelengths depends on the surface temperature of Earth itself3. The QWIPs TIRS applies two thermal infrared wavelength bands, which allows a successful separation of the temperature of the Earth’s surface from that of the atmosphere, in order to ensure accurate measurements.
Based on the complex principles of quantum mechanics, gallium arsenide semiconductor chips within the QIPs TIRS system traps electrons in an energy state ‘well’ until the sensed thermal infrared light is able to elevate electrons to a higher state. These elevated electrons create an electrical signal that can be recorded to create a digital image3.
Successful Imaging of the Earths Surface
Betsy Forsbacka, TIRS instrument manager at NASA, recently celebrated the ability of the TIRS and Landsat technology to create a comprehensive image of the Pacific’s Paluweh volcano in mid-eruption.
Each instrument by itself is magnificent. When you put them together, with the clues that each give you on what you’re seeing on Earth’s surface, it’s greater than either could do by themselves5.
Betsey Forsbacka, TIRS Instrument Manager, NASA
In order for this image to be produced to such a degree of refinement, TIRS engineers tested and calibrated the instrument pre-launch, pixel-by-pixel, ensuring TIRS’ ability to capture specific volcanic activity and color.
Able to detect subtle shifts of temperatures to within a tenth of one degree Celsius, the TIRS instrument provides NASA with the chance to continue to expand universal applications of thermal imaging. With Landsat 9 currently in progress, NASA hopes to continue to share these intricate images to increase our understanding of our home planet, improve lives, and safeguard our future on Earth6.
References and Further Reading
- History of Thermal Imaging
- Thermal Imaging Cameras Explained
- Thermal Infrared Sensor (TIRS)
- Data - Landsat Science
- NASA Observes Volcanoes From Space Using Thermal Imaging - Redorbit
- NASA, USGS Begin Work on Landsat 9 to Continue Land Imaging Legacy