2b. Select an Infrared Wavelength


Tracking Icebergs During Nighttime Hours

Half the year the polar regions are in darkness, making detection of icebergs using satellite observations with solar wavelengths useless. Objects on Earth are always emitting infrared energy, which can be used during the day or night. For this reason satellite radiometers measure infrared, or IR, energy. You can use the IR to track icebergs if the temperature contrast between the ice surface and the unfrozen waters provides good contrast. In this exercise, you will select an optimal IR wavelength to identify an iceberg. As with the solar exercise, there is more than one correct answer.

Infrared wavelengths that differentiate between water and icecrescent moon

Images obtained by Low Earth Orbiting Satellites (LEOS) during nighttime hours come in various infrared wavelengths. (See Tutorial 1: Remote Sensing). In step 2 you need to select an infrared wavelength that clearly differentiates between water and ice.

Images of the same geographic region at different infrared wavelengths (range 3.5 - 100 micrometers)

Iceberg image, 11 micron infrared wavelength Iceberg image, 7.5 micron infrared wavelength Iceberg image, 14 micron infrared wavelength

The highlighted image aboves uses a wavelength value that provides good contrast between ice and surrounding water during the nighttime. The activity below will help you determine the optimal infrared wavelength value.

Determining an Infrared Wavelength

Use the graph to find a wavelength value with the greatest contrast between ice and ocean surface properties.

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This application demonstrates contrast between water and ice at infrared wavelengths

Click the forward arrow to continue to Step 3: Selecting the iceberg.

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