Radar Means: Radio Detection And Ranging

Teacher Sheet(s)
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Objective:

To learn how radar works.

Level: K-4
Subjects(s): Geography, Science, Technology
Prep Time: More than 30 minutes
Duration: One-two class periods
Materials Category: Special Requirements

National Education Standards
Science: 2a3, 2a4, 5a, 6a
Math:
Technology (ISTE):
Technology (ITEA): 1b, 3a, 7a
NGS Geography Standards: 1a, 1b, 1c

Materials:
  • Shoeboxes
  • Red, green, and blue clay
  • Straws
  • Red, green, and blue crayons
  • Drawing paper

Related Links:

NASA Jet Propulsion Laboratory—Space Radar

NASA Visible Earth—Radar

National Oceanic And Atmospheric Administration

The Weather Channel

 

Supporting NASAexplores Article(s):

Avoiding In-Air Collisions


Pre-Lesson Instructions:
  • Prepare the shoeboxes.  Distribute the blue clay on the bottom of the shoebox.  Add a layer of red clay next, leaving some of the blue exposed.  A small amount of green clay should be placed on top of the red to create the highest level.
  • Measure each height.  Add or reduce the amount of clay so that the measurements will all be on inch marks.  This will help younger students complete the activity.

    topographical map

  • Tape the lid on securely.  Make enough for each group of two.
  • Using a ruler and pencil, draw a pattern on the top of the box indicating where students will poke holes to take measurements.  These holes should be evenly spaced, and the pattern should include enough holes to get an accurate reading of the content of the box.  After the box top is marked, poke a small hole through each mark. The hole should be just big enough to allow the straws to pass through.

Background Information:

Typical radar measures the strength and round-trip time of the microwave signals that are emitted by a radar antenna and reflected off a distant surface or object.  The radar antenna alternately transmits and receives pulses at particular microwave wavelengths and polarizations.  At the Earth's surface, the energy in the radar pulse is scattered in all directions, with some reflected toward the antenna.  This backscatter returns to the radar as a weaker radar echo and is received by the antenna in a specific polarization.  These echoes are converted to digital data and passed to a data recorder for later processing and display as an image.

radar signals bounce off of objects and return to the radarRadar images are composed of many dots, or picture elements.  Each picture element (pixel) in the radar image represents the radar backscatter for that area on the ground. Darker areas in the image represent low backscatter, brighter areas represent high backscatter.  Bright features mean that a large fraction of the radar energy was reflected to the radar, while dark features imply that very little energy was reflected.

Scientists measure backscatter in units of area.  The backscatter is often related to the size of an object, with objects approximately the size of the wavelength or larger appearing bright and objects smaller than the wavelength appearing dark.

Backscatter is also sensitive to the target's electrical properties, including water content.  Wetter objects will appear bright, and drier targets will appear dark.  The exception to this is a smooth body of water, which will act as a flat surface and reflect incoming pulses away from a target; these bodies will appear dark.


Guidelines:
  1. Read the NASAexplores K-4 article, “Avoiding In-Air Collisions.”
  2. Discuss the importance of using unmanned planes for this project.
  3. Point out the word radar in the story.  Read the definition.  Ask students to describe what they think of when they hear the word radar.
  4. Display several radar images.  See related links section for a list of several different sites that have radar images.
  5. Tell students that today they are going to get to make a map by reading a radar image.
  6. Distribute the boxes and straws.
  7. To take a measurement, students should insert the straw until it meets resistance.  Tell them not to press down too hard.  Students should make a mark on the straw at the point where it meets the box top.  They will remove it from the box, and measure the length from the mark to the end of the straw.  This will give a distance reading from the box top to the landscape.
  8. Once all the measurements have been made, each group should draw a topographic map.  Tell each group to make a mark on its papers to show the height of each hole.  They should connect all the marks that measure the same length.  Then, they should fill in the circles with the corresponding color.  In the example above, the 6-inch circle would be colored green, the 3-inch circle would be colored red, and the rest of the box would be filled in with the blue crayon.

Discussion/Wrap-up:
  • After the maps are completed, each group should open their box lid and compare the map to the real thing.
  • As a class, discuss how the maps symbolize the radar picture.
  • Discuss how radar would help a keep airplanes avoid hazards.  What kinds of things might radar pick up that would help a plane?
  • Discuss how radar helps predict the weather.

Extensions:
  • Have students collect examples of topography maps.
  • Have a local meteorologist come to the classroom and share how radar is used to forecast weather.

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