Thermal IR

Thermal IR data has long been available with Landsat TM data yet is seldom used. A new generation of instruments is changing the way thermal IR data is viewed, and is a promising way to see materials not normally observable with optical data.

Thermal Data

The key to the resurgence of thermal data is the increase in the number of channels. Now, instead of deriving only a temperature of a target, an emissivity spectral curve may be generated that can be compared to existing thermal IR spectral libraries, much like what is being done with hyperspectral reflectance data. Certain mineral groups, like silicates, and gases that have little to no distinguishing features in reflectance, are quite distinctive in emittance. Two new sensors are leading the way in this field: Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)

• Presently in orbit
• 4 VNIR bands, 15m resolution
• 6 SWIR bands, 30m resolution
• 5 Thermal bands, 90m resolution
Spatially-Enhanced Broadband Array Spectrograph System (SEBASS)
• Airborne instrument
• 1 - 3m resolution
• 128 channels each in MWIR and LWIR

Multispectral thermal IR image of southern Peru

Application

Minerals have distinctive emission features

Multi and hyperspectral thermal IR sensors have opened the door to a new collection of applications. Geologic features composed predominantly of silicate minerals (such as igneous rocks, including lava flows) can be mapped in intricate detail. Minerals like pyrite and quartz, so difficult to account for with optical hyperspectral imagery, can be mapped to provide a more complete picture for use in mineral exploration. Gases emitted by refineries, landfills, natural or anthropogenic hydrocarbon leaks, and many other sources can be detected and quantified. This very young research field filled with unique challenges is growing rapidly, and MDA is there creating solutions.