Slide 1

Introduction and Fundamentals

Slide 2

Airborne thermal image of warm creek flowing into ocean near Anchorage, AK

Slide 3

Thermal sensors can measure the amount of emitted long wave IR that is upwelling from the surface Different materials give off (emit) thermal radiation in different proportions (depends on emissivity) Thermal can operate day or night (thermal lag) Objects that are warm or cold relative to their surroundings stand out in thermal imagery

Slide 4

IR = 0.76 um to 1000 um Reflective IR = 0.7 3.0 um (NIR and SWIR) Thermal IR for remote sensing = 7 18 um (FIR) IR beyond 18 um is not used for thermal remote sensing Experiences almost no atmospheric scattering Butlots of absorption by atmospheric gases (e.g., CO 2 ) Must use atmospheric windows for remote sensing Reason for the greenhouse effect

Slide 5

The infrared portion of the electromagnetic spectrum Emitted Thermal

Slide 6

Atmospheric transmission by

Slide 7

Univ. of Maryland

Slide 8

Many satellites have thermal IR bands Landsat TM and ETM+ (1 thermal band), and Landsat 8 (2 thermal bands) MODIS (multiple thermal bands) ASTER (multiple thermal bands) CBERS (1 thermal band) Thermal bands usually lower spatial resolution than optical bands due to low total thermal energy Some sensors are devoted to thermal remote sensing and collect several thermal bands simultaneously TIMS JPL instrument

Slide 9

Closer view: TIMS Death Valley composite

Slide 10

All objects with temperature > 0 o K emit thermal radiation Amount of radiation and peak wavelength emitted depend on temperature (Stefan-Boltzman Law and Wiens Displacement Law) and emissivity Hotter objects emit more thermal radiation for a given emissivity Objects absorb radiation and then emit it based on their emissivities

Slide 11

Wiens Displacement Law

Slide 12

Emissivity () is measure of ability of a material to absorb and re-emit EMR Emissivity is the ratio of the emittance of an object to that of a Black Body A black body has = 1 (Absorbs and re-emits all radiation that hits it) A white body has = 0 (Reflects all radiation that hits it) Water has emissivity close to 1 Most vegetation has close to 1 (because mostly water) Many minerals have