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
Infrared wavelengths that differentiate between water and ice
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)
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.