More Lessons from the Sky · Web view– schematic diagram, sensor parts list, construction tips, and bottom view of transistor wire connections Sensor Construction – drawings of

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Modeling Satellite Remote SensingBuild and Operate a Working Model Remote Sensor

IntroductionA covert military operation examines “intel” from images obtained using satellites and cameras on unmanned airplanes. A meteorologist at the National Severe Storm Laboratory in Norman, Oklahoma, analyzes a series of satellite images and other data to predict the path and potential for destruction of a mounting tropical storm in the Atlantic Ocean. A video cameraman records a report by a television journalist at the edge of a growing forest fire that is broadcast live to homes hundreds of miles away. A radiologist uses an x-ray to “see” the broken bone in a young child’s arm. A geologist working for a petroleum company studies a multispectral image from a Landsat satellite to determine the probable presence of subterranean gas and oil in a specific region. What do they all have in common? Remote sensing – using a sensor to detect changes in reflected light at a place other than one we can directly see with our own eyes. That is a loose definition, but the concept is not. Though some remote sensing shown in motion picture stories is fiction, the evolving technology is very real and increasing accessible. During the more than half century since the first launch of an artificial satellite, the body of knowledge about which wavelengths of the electromagnetic spectrum are most reflected by which features of the Earth’s surface and various components of the atmosphere has grown immensely. In this lesson, you will build a simple electronic light sensor that transmits a radio signal when activated by light. The transmitted signal can be received with any FM radio and heard as an audible tone. The quality of the tone varies with the intensity of the light striking the sensor. You will use the sensor to observe and measure the amount of light of various colors when reflected from different surfaces.

More Lessons from the Sky, 2018, Satellite Educators Association Modeling Remote Sensing 16

Student Activity

17 Modeling Remote Sensing More Lessons from the Sky, 2018, Satellite Educators Association

Student Activity

PreparationAttached here are several tutorials to help guide you through the construction, testing and use of your model remote sensor. Your teacher will tell you which ones to use.

What’s That? – reference sheet with definitions, component descriptions, drawings of components, and component symbols used on schematic diagrams

Winding the Coil – specific directions for making the inductor by winding your own coil

Building a Remote Sensor Model – schematic diagram, sensor parts list, construction tips, and bottom view of transistor wire connections

Sensor Construction – drawings of a breadboard and a completed sensor model to help you visualize the instructions on other guide sheets

Testing – complete guide to testing and troubleshooting for a properly working sensor model

Gathering Reflectance Data – procedure for using your remote sensor model to gather reflectance data with the assistance of specialized computer-based probes and data acquisition software

Data Table – a blank data table for recording your raw data by hand before setting up the spreadsheet

Determining Relative Reflectance – guidelines for organizing your raw data, setting up the spreadsheet and graphing your data using Excel

Analyzing Reflectance Data – questions to guide your analysis of the graphs and application of the conclusions to the Your Turn section

Your Turn – closure activities to extend your understanding by applying the concepts learned to new scenarios


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Clean wire from the ends using fine sand paper

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What’s That?This reference sheet contains definitions, drawings of components, the symbols for the components used in schematic diagrams, and supplemental information about the components and what they do.

Resistor = device to slow electrons in an electronic circuit; measured in Ohms (Ω).

Capacitor = device to store static electric charge in an electronic circuit; measured in Farads (F). Charge is stored and then discharged across the capacitor plates at regular intervals depending on the value of the capacitor. Electrolytic capacitors have an electrolyte between the plates where the charge is stored but then continuously leaked in very small amounts of current between discharges.

Inductor = Inductance is the property of an electric circuit by which a varying current produces a varying magnetic field that induces voltages in the same circuit or in a nearby circuit; measured in henrys (H). You will build your own inductor by winding lacquered wire around a coil form


Resistor Color Code

1st & 2nd Color Band 3rd Color Band 4th Color BandBlack 0 Black x1 Tolerance:Brown 1 Brown x10 Gold 5%Red 2 Red x100 Silver 10%Orange 3 Orange x1k None 20%Yellow 4 Yellow x10kGreen 5 Green x100kBlue 6 Blue x1 megViolet 7 Silver /100Gray 8 Gold /10White 9

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CBCBE

2N2222 Bottom View

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(section of soda straw). Using the safety pin, carefully poke three holes all the way through the straw as indicated. Pass the wire through the first hole to hold the wire in place. Wind the wire around the straw 10 times and pass through the second hole. Leaving about 3 inches of wire extended through the second hole, loop the wire back through the same second hole. Continue winding the wire around the straw in the same direction as before for another 20 turns. Pass the wire through the third hole to hold it in place. The result is a coil of 30 turns with a connecting wire at each end and a connecting wire 1/3 of the way through the coil (called a “center tap”). Use the sand paper to carefully clean the lacquer from about ½ inch of the end of each of the wire leads.

Transistor = A semiconductor device commonly used as an amplifier or an electrically controlled switch. The three leads from the transistor case are the base (B), emitter (E), and collector (C).

Battery = An enclosed storage container for a chemical reaction (dry cell) that supplies a source of electrons to move (current) in an external circuit and the electromotive force (voltage) to move them. Electrons move out of the negative pole and into the positive pole of the battery.

Photoresistor = An electronic component whose resistance decreases with increasing incident light intensity.

Antenna = A transducer designed to transmit or receive radio waves (electromagnetic waves). Antennas convert radio frequency electrical currents into electromagnetic waves and vice versa.

Breadboard = A board with connection points where electronic components can be arranged in a trial circuit with temporary connections. In the


Bottom View 2N2222A

Student Activity

breadboard diagram below, each dot is a connection point. Five points are connected together internally as indicated by the lines joining the points in the diagram.


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First hole made with a straight pin

3/8”3/16”

Student Activity

Winding the Coil

Procedure1. Cut a section of plastic soda straw about 1½” long.2. Measure ¼” from one end of the straw and poke a hole all the way through both

sides of the straw with a straight pin. Do not push the pin into your finger! 3. Measure 3/8” from the first hole and make a second hole in the straw.4. Measure 3/16” from the second hole and make a third hole in the straw.

5. Magnetic wire is copper wire that has a coating of lacquer instead of vinyl insulation. It is used in making coils that produce a magnetic field when the coils are used as inductors. When working with magnetic wire it is very important that you avoid kinks in the wire and do not scrape the lacquer off the wire.

6. Carefully thread one end of your magnetic wire through the first hole so that the wire goes all the way through the straw. Pull about 3” of wire through the hole for connecting the coil in the circuit later.

7. Hold the 3” wire lead in place and carefully wrap the wire neatly until you have exactly twenty turns around the straw. As you coil the wire, place each wrap immediately next to the previous wrap. Pull the wire tight, but do not deform the straw. Then thread the other end of the wire through the second (middle) hole until the wire goes all the way through the straw. Gently pull the wire snug so the 20 turns of coil stay in place.

8. Double back and thread the end of the wire through the second hole again in the reverse direction leaving about 3” of doubled wire sticking out.

9. Now continue to wrap the wire around the straw until you have exactly 10 more turns of wire.

10. Thread the end of the wire through the third hole and gently pull the wire so that the additional 10 turns stay in place.

11. Cut the excess wire leaving about 3” for connecting the coil in the circuit later.12. With sand paper, carefully clean the

lacquer from the about ½” of the end of each of the three connecting wires. Leave the lacquer on all turns of the coil. Gently twist together the doubled wire from the second hole.


Student Activity

Building a Remote Sensor Model

Purpose To build a photo sensitive transmitter in order to simulate the identification of Earth’s surface materials by a satellite remote sensor using various frequencies of the electromagnetic spectrum reflected from surface objects

MaterialsTransmitter: Q1 NPN transistor, 2N2222 or 2N2222A

I1 Inductor: 30 winds tapped 1/3 of the way from one end

Bat 1.5VDC AA battery in battery holder with leadsC1 4.7f polarized electrolytic capacitorR1 47K resistor, carbon film, ¼ wattR2 Photo resistorA1 Antenna: 22-guage solid hook up wire, 6-12 inches

FM receiverColor filters: Monochromatic blue, green, red

Procedure1. Check to be sure all parts are present and they are the correct parts.2. Make the inductor: Cut a piece of plastic tubing about 1½ inch long

and about 40 inches of magnetic wire. Wind 20 turns of the coil then 10 more turns with a connector protruding from the coil between turn 20 and 21.

3. Carefully place all parts in order following the circuit diagram. Give particular attention to polarity. Determine which transistor lead is the emitter (E), the base (B), and the collector (C) using the diagram below.

4. Do not allow any wire component leads to make connection where no connection is shown in the circuit diagram.

5. Connect each component by soldering, or with a crimp connector, or use a breadboard. If soldering, protect the component from excess heat with a heat sink during soldering.


CBE

2N2222Bottom View

2N2222ABottom View

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CB

Q1

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Sensor Construction With Breadboard Module


Diagram A: Breadboard Socket Internal Connections(top view)

Diagram B: Layout of Senor Components when Connected to Breadboard

Note: The positions of the emitter, base, and collector wires on the transistor can be deceiving in this drawing.

Always rely on the schematic with base diagram (bottom view) of the transistor.

Student Activity

TestingAnd Troubleshooting

Procedure1. Compare the placement and connection of each component to the

schematic diagram to verify correct connection.2. Place the battery in the battery holder.3. Turn on the FM radio and tune to a relatively silent frequency between

stations. Expose the photo resistor to a light source. Listen for clicks on the radio.

4. If you hear the clicks on the radio, skip to Step 7.5. If you do not hear clicks on the radio, try the following steps:

a. Retune the radio to a different frequency.b. Check each connection to insure its integrity. Remember, if using a

breadboard, the contacts in the breadboard may not be clean. If may help to slip a piece of wire into and out of each contact hole several times to “scrape” the contact clean.

c. Check the connecting ends of all wires including the antenna. Use the sand paper to insure all have been scraped free of any oxide or lacquer coating.

d. Check the battery with a voltmeter to insure it is producing at least 1.5 volts.

e. Check the battery holder is connected correctly in the circuit. Insure the battery contacts on the holder are clean.

f. Check the transistor installation to ensure it is connected correctly. It not, it may be necessary to replace the transistor.

g. Check the coil to insure it is wound correctly and correctly connected in the circuit. Use a continuity tester from the farthest ends to check for breaks in the wire. There should be no breaks even though there is a center connection wire (center tap).

h. Check the capacitor to make sure it is connected correctly. Remember, the capacitor is polarized so connecting it backwards makes a difference.

i. Remove and check the resistor with an Ohm meter. It must be (1) conductive and (2) the correct resistance.

j. Try using a different photoresistor.6. If clicks are still not heard, repeat Step 5.7. If clicks are heard, you are ready to experiment with the reflectance of

various substances.


Student Activity

Gathering Reflectance Data

Procedure1. Set up your sensor with the photoresistor in a black plastic tube, if

available, to make sure the measured light is reflected from a test surface and not received directly from the light source.

2. Adjust the end of the tube 5 cm from the reflective sample. Place the lamp 7 cm from the source to make sure light does not enter the tube directly from the light source and that the lighting will be consistent. Use white paper for the reflective surface.

3. Set up the microphone, computer interface, and data acquisition software. The software may auto-ID the interface and microphone sensor. In that case, you can use the default screen for data collection. Set the sampling rate to 10,000 samples per second and a collection time of 1.0000 second.

4. Tune a standard FM radio receiver to a frequency with little or no station broadcasting so the clicking pulses can be heard clearly. Place the microphone near the radio speaker.

5. Click Collect to ingest sound data with the computer. When the graph is displayed, each click is apparent as a major peak. The minor peaks are background noise and static.

6. Drag the cursor from an average major peak to the next successive major peak to measure the number of samples between successive pulses. In the menu bar, click Analyze and select Statistics. The number of points between peaks will be counted and listed in a pop-up information box. In Table A on your Data Analysis sheet, record the number of counts (samples) between peaks.

7. Repeat Steps 4-6 using a colored filter in front of the sensor so that the sensor receives only light of that color. Use blue, green, and red filters respectively. Record the counts between peaks for each.

8. Repeat Steps 4-7 changing the reflective surface each time to blue paper, green paper, red paper, and any other surface such as yellow paper, green leaves, or sand. Record the counts between peaks for each.


Student Activity

Data Table

Distance: Light source to reflective surface cmDistance: Reflective surface to photoresistor cm

Number of Counts Between Pulses(sampled at 10,000 samples per second)

Reflective FilterSubstance None Blue Green Red

White paper Blue paper Green paper Red paper Unknown:____________


Student Activity

Determining Relative ReflectanceUsing Excel to Analyze Reflectance Data

Thinking About Your DataOn your Data Table, you recorded the number of samples (or counts) between each peak (click). Recall the total data collection time you set was 1.0000 seconds, and 10,000 samples were taken in that time. Now you will convert that number into a relative reflectance value for each data collection run. The relative reflectance value will be the click rate (number of clicks or pulses per second) for each reflective surface and filter combination tested. Divide the number of samples between peaks into 10,000 samples per second to find relative reflectance. For example, suppose the number of samples between peaks for white light on white paper was 2620. Then:

10000 samplessecond

2620 samplesclick

=3 . 817 clickssecond

Notice a higher click rate (and therefore less time or fewer samples between pulses) means the reflected light received by your sensor is more intense. Thus, the relative reflectance value is a number that increases with light intensity.

The relative reflectance values are not absolute; they are only important relative to each other for your particular sensor. For graphing purposes, it may be easier if these values were integers instead of fractions. So, the next step is to multiply each relative reflectance value by 100 or 1000 to obtain integers. Then you will use the spreadsheet Chart function to produce your graphs.

Setting Up the SpreadsheetYou will set up two tables on the same Excel worksheet. The first table should look just like Table A below.

Table ANumber of Counts Between Pulses(sampled at 10,000 points per second)




Student Activity

In each cell, list the average number of samples or counts between clicks as listed on your handwritten Data Table. Give special attention to font styles, column width, border lines, and completeness when setting up the Excel tables.

Make Table B by copying Table A and pasting the copy below Table A on the same Excel worksheet. Be sure the tables are separated by 2 blank rows. Then edit the cells to change the titles and delete the numbers from the columns on the copy so it looks just like Table B below.

Table BRelative Reflectance((10,000/number of counts) x 100)



Don’t try to use a calculator to fill Table B. Let Excel do the work for you. Now you are ready to create formulas that will build the contents of Table B for you.

Adding FormulasTo create a formula in an Excel spreadsheet cell, place the mouse cursor on the cell and click once to activate the cell. Then type an = sign and follow it with the formula for the needed calculation. If necessary, the calculation formula may contain references to the contents of other cells by typing the cell reference (such as A12 or G75). Press Enter to complete the formula.

Do the following to set up formulas in each cell of Table B so that the relative reflectance values will be calculated from Table A automatically.

Click cell B18 or the cell in Table B for Reflective Substance = White paper and Filter = None.

Type =((10000/

Do NOT press the Enter key yet . Instead, click on cell B6 or the cell in Table A for Reflective Substance = White paper and Filter = None.

Cell B18 should now contain this: =((10000/B6 or =((10000/#### where #### is the count from cell B9 in Table A.

Do NOT press the Enter key yet . Instead, type )*100)

Now, cell B18 should contain this: =((10000/B6)*100) or


Student Activity

=((10000/####)*100)Now press the Enter key. A number will appear in cell B18.

Click cell B18 to select it as the active cell, and then click COPY.

Highlight cells B19 through B22 and click PASTE.

Highlight cells B19 through B22 and click COPY.

Highlight cells C18 through E18 and click PASTE. All empty cells in Table B should now have numbers.

Highlight cells B18 through E22. On the menu bar, click Format Cells and select the Number tab. Select Number from the Category list. Change the number of Decimal places to 0 and click OK. All of the numbers in Table B should now be rounded off to whole numbers.

Now, it is time to create your graph in the same spreadsheet.

Graphing with Excel Highlight all of Table B. Then click on the chart icon (looks like a bar graph)

on the tool bar at the top of the screen.

From Chart type, select Line and click the sample on the right described as Line with markers displayed at each data value. Click Next.

On the Data Range tab, click the Series in Columns radio button and click Next.

Type a title for your graph in the box for Chart title. Try a title like Relative Reflectance of Various Materials.

Leave the Value (X) axis box blank.

In the Value (Y) axis box, type a label for the Y axis. Try a label like Relative Reflectance. Click Next.

Place the chart in the spreadsheet by clicking the radio button As object in: Sheet 1. Click Finish.

Rescale the graph by double clicking one of the Y axis values. Select the Scale tab. Change the minimum value to a convenient whole number less than the lowest relative reflectance value. Similarly set the maximum value. For example, if the data points in Table B are all between 280 and 390, then setting minimum and maximum values to 200 and 400, respectively would work. You may need to adjust these values to spread out your graph lines as much as possible and show all of your data points on the graph. When finished, click OK.

To adjust the size of the graph, click once inside the graph frame so the frame handles are displayed. Grab the top handle and drag it up on the screen to lengthen the graph. This will spread out the colored lines making them easier to see. Click outside the graph frame to hide the handles.

To adjust the color of each line so it matches the reflective paper color,


Student Activity

double click the colored lines in the graph one at a time. On the Patterns tab, in the Line section, click the drop down arrow for Color and select a color matching the filter color for that line. Similarly change Weight to a thicker line.

In the Marker section, click the drop down arrow for Foreground and select the same color. Select the same color again for Background. Change Size to 10. Click OK.

Repeat the last two steps for each of the other lines on the graph.

Ask your teacher to check and approve your graph.

Save your file with a file name and location designated by your teacher.

Check with your teacher about printing your graph.


Student Activity

Analyzing Reflectance Data1. Compare the relative reflectance of red, blue, and green light reflected from red

paper.

2. Similarly, compare the relative reflectance of each color of light reflected from blue paper and green paper.

3. How does this compare with the relative reflectance from white paper?

4. What happens to the electromagnetic radiation colors with less reflectance?

5. Explain the relative reflectance values for sand.

6. Might it be possible to identify different surface features on the Earth from a remote sensor on a satellite orbiting at an altitude of 580 miles? In terms of relative reflectance, explain how this could be done.


Student Activity

YOUR TURN


Typical weather satellite images are typed “visible,” “infrared,” and “water vapor.” Investigate the wavelength bands that produces each type of image. Do images of different wavebands but the same time and place appear the same? How are they alike? How are they different? What is detected in each that is not in the other two? How are these images useful in predicting the weather for the next day? The next week? Do one of the following: (1) In a written report that includes labeled image samples (many are downloadable freely via the Internet), compare the image types. Submit your report to your teacher. (2) Prepare a presentation supported by PowerPoint about the two sensors, their capabilities, and how they are used. With your teacher’s approval, deliver the presentation to your class or other suitable audience.

The Advanced Very High Resolution Radiometer (AVHRR) sensor is also carried on most polar-orbiting weather satellites. Investigate the various wavebands available in AVHRR data sets. List them and describe how each might be used to distinguish various surface features. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensor is carried on two of NASA’s environmental satellites. Similarly investigate the wavebands available in MODIS image data sets. Which surface features are most easily detected by each? How are the data from each used primarily today? Do one of the following: (1) In a written report that includes labeled image samples (many are downloadable freely via the Internet), compare the image types. Submit your report to your teacher. (2) Prepare a presentation supported by PowerPoint about the two sensors, their capabilities, and how they are used. With your teacher’s approval, deliver the presentation to your class or other suitable audience.

Using your model sensor, devise an experiment to differentiate between at least 10 different materials, both naturally occurring and human-made “cultural features” found outdoors and in the sunlight, in an effort to define a “spectral signature” for each material. Do one of the following: (1) In a written report that includes relative reflectance graphs of the substances tested and, if possible, digital photographs of the substances tested, compare and explain the relative reflectance of each substance. Submit your report to your teacher. (2) Prepare a presentation supported by PowerPoint about the relative reflectance graphs of the tested substances. With your teacher’s approval, deliver the presentation to your class or other suitable audience.

Explore the design of your model sensor. What function does each component play in the operation of the your sensor? Questions to be considered might include: (1) If the coil is made following the same instructions but on a straw that has twice or half the diameter, will it operate the same way? (2) Will a capacitor that has a voltage rating of 500V instead of 50V do the same job in the circuit? (3) What effect might reversing the leads on the polarized capacitor have on the operation of the circuit? (4) What would happen to the transistor if it was incorrectly connected in the circuit? Research these and/or questions of your own to develop a hypothesis based on scientific knowledge. Plan a careful experiment to test your hypothesis including considerations for cost and available materials. Consult your teacher about the best way to carry out the experiment and present a report of the results to your class.

Documents

More Lessons from the Sky · Web view– schematic diagram, sensor parts list, construction tips, and bottom view of transistor wire connections Sensor Construction – drawings of