Unit 5 Activity 6: Atmospheric Effects in Remote Sensing

About this Activity

In this activity students explore how the atmosphere affects the Sun's energy as it travels down to the Earth's surface.  Students will interpret graphs showing information about atmospheric effects.

Questions

  1. The electromagnetic energy travels through the atmosphere from the sun to target remote sensing sensors. Certain sensors pick up visible and infrared radiation. Each wavelength belongs to a characteristic band, which is just a range of wavelengths. Each band can be described by a color  (for example 'blue') if the observed wavelength is within the range of visible light.   If not visible light, then the band represents other wavelengths in the electromagnetic spectrum, like infrared.
    3. This table shows the 'bands' or channels 
    received by a remote sensing devise,  and 
    the wavelengths assigned to each band.
     
     
     
     
     
     
     
     
     
     
     
    Bands Wavelengths
    1  blue
    2  green
    3  red
    4  near infrared
    5  near infrared
    6  thermal infrared
    7 near infrared
The atmosphere absorbs, transmits, and scatters energy.
  1. Some Energy is Transmitted   Which type of energy do you think passes through the atmosphere and reaches the sensor unchanged?

    2.  

     
     
     

  2.    Some Energy is Absorbed  When the Sun's energy is absorbed by the air or the ground,  what type of radiation is re-emitted.  Why?

 
  1. Some Energy is Scattered   What effect do you think atmospheric scattering does to the image being scanned? Answer:  Scattering  results in haze and diminished image clarity.  Scattering- the redirection of light by particles or molecules in the atmosphere.  Try to think of an example of the results of scattering and describe it.  (Hint)

 
  1. Study the following graph. Write down how you would interpretation this graph.  What does it show?

    2. [Graph of Bands vs. Scattering %]
                                       Key:     B = blue
                                                   G = green
                                                   R = red
                                                   IR = infrared

     
  2.   Study the graph below.  Only certain wavelengths can get through the atmosphere well.  These

    3. regions are called atmospheric windows.   This graph shows how various wavelengths in the electromagnetic spectrum pass through the atmosphere.  The yellow area shows the percentage of the wavelength that gets all the way down to the surface of the Earth.   The Earth's atmosphere screens out most of the sun's wavelengths that are shorter than those of  visible light by absorbing them when the short wavelengths strike atmospheric molecules.  Other wavelengths get through the atmosphere in varying degrees dependent on the amount of moisture, smoke, dust, clouds, carbon dioxide and even the angle at which the sun's light strikes the Earth which is dependent upon the seasons and the time of day.  More or less light waves get through, depending on different atmospheric conditions.  The variations result in the different colors of the sky and clouds at noon or at sunset.
     
     
    Read this website for a really  good illustration and discussion about radiation and the Earth's atmosphre.

    1.  Which wavelengths get all the way through the atmosphere to the Earth's surface?
     

    2.   Which wavelengths do not get all the way through the atmosphere to the Earth's surface?
     
     

    3.  What percent of  visible light gets transmitted?   Does the full range of visible light get equally transmitted?
     

    4.  Describe what happens in the Infrared range.
     
     
     

    5.  According to the Windows through the atmosphere graph, for which wavelengths could you use for a telescope from the Earth's surface?   Which wavelengths could not be easily studied with a telescope from the Earth's surface?