Enhancing Voyager Images By Gary Purinton Abstract Students have seen many of the images that the National Aeronautics and Space Administration (NASA) has released from the Voyager I and II missions as well as images from other spacecraft. Many of these images have been enhanced by digital image processing. In order to help students appreciate the meaning of the images and their value to scientists, this activity teaches students how to enhance a selected image using a variety of techniques. This activity is an introduction to planetology. Title: Enhancing Voyager Images 2061 Themes:Interaction of science and technology, information processing Major Concept: Astronomers use computers to study planetary bodies Process: Observation, Comparison, and Analysis Attitudes: Technology promotes understanding of the World. Disciplines:Astronomy/Earth Science Grade Levels: 7-12 Key Word Search: image processing, image enhancement, astronomy, planetology, moons, solar system, NASA, voyager, contrast Objectives: Students will learn how image enhancement increases our understanding of the solar system. Materials: JEdI B Disc, IMDISP program, PCMIPS program, PREPARE.BAT program BACKGROUND The Voyager images on the JEdI disc can be prepared for processing with the PREPARE program (see Appendix A). Groups can take turns performing image enhancements of the selected Voyager image(s) using the program PCMIPS, analyzing the results using the program IMDISP, and presenting their technique and results to the entire class. The enhancement techniques include contrast stretching, edge enhancement, high pass filtration, and first derivative (difference). The images that the students will be enhancing are located on the JEdI B disc in the PLANETS sub-directory. The full path name is L:\IMAGERY\PLANETS. The images of three of Jupiter's moons - Io, Callisto, and Europa - are good places to start. Io's full path name is "L:\IMAGERY/PLANETS/JUPITER\IO." The following two programs will be used to display and manipulate the images: IMDISP to display the image and PCMIPS to manipulate the image. The Voyager images have textual information about each image in a header located in the image file. You can use a text reader or the DOS "TYPE" command to read the header. IMDISP can "overlook" the header information to display the image; however, PCMIPS expects the label and data to be separated in two different files. Therefore, the image files need to be prepared for the students to use by removing the header and creating a separate label file. A batch file called PREPARE.BAT has been developed to make this process more manageable (see Appendix A). INTRODUCTION TO DIGITAL IMAGE PROCESSING The "pictures" from the Voyager spacecraft are actually digital images. If you look closely enough, you will see that the image is composed of tiny squares called pixels, short for "picture elements." Each Voyager image has 800 lines each containing 800 pixels (also called elements or samples), and each pixel has a brightness value between zero (darkest) and 255 (brightest). The reason for this particular range is that one byte of computer memory is able to represent 256 different values. A computer program called IMDISP was developed by NASA to display these types of images. Since the program was designed to display images with different numbers of pixels, the computer needs to know exactly how many lines and elements there are in the image you want to display. On the JEdI disc, that information is usually included in the image file as a "header" which IMDISP reads before displaying the image. In some cases, the header has been put in a separate file called a "label" which may have an .LBL extension. A label file includes the name and location of the file which contains the actual image data. The advantage of having these images available in digital format rather than a picture is that they can be manipulated and enhanced in order to extract more information from them. Image enhancement can increase the contrast in "flat" images, emphasize the edges of patterns in the image, emphasize details in the image, or smooth out unwanted clutter or noise. This activity allows the students to use some of the actual tools that scientists use to understand more about planets, moons, and comets. Getting the System Ready In order to use these images, some software programs should be loaded onto your hard drive. This will enable you to run these programs faster and without interruptions. Note: In all instructions "C:" is used as the hard drive. This may be changed for your own computer. Making Directories for IMDISP 1. Type CD \ and then strike [Enter]; this takes you to the root directory. 2. With the prompt on your hard drive, type MD IMDISP and then strike [Enter]. 3. Type CD IMDISP [Enter] to get into the IMDISP sub- directory. Now type DIR [Enter]. While in this sub- directory make a directory for PALETTES. To do this type MD PALETTES [Enter]. This will allow you to copy the pre-made palettes into your IMDISP program. 4. Check to see if all your directories are in place by typing DIR [Enter]. You should see a path of \IMDISP and the PALETTES sub-directories which you have just added in the IMDISP sub-directory. Be sure that you are in the IMDISP sub-directory by typing DIR [Enter]. Copying the IMDISP Programs 1. Now change to the CD-ROM drive by typing L: [Enter]. 2. Type DIR [Enter] to access the directory. 3. Type CD DOS\IMDISP [Enter]. You should now be in the IMDISP sub-directory. To check for this, type DIR [Enter]. 4. Now type COPY *.* C:\IMDISP. (Note: "C:" is used here as the hard drive.) 5. To copy the PALETTES files into the PALETTES sub-directory, change your CD-ROM sub-directory to the PALETTES by typing CD PALETTES [Enter]. Now type COPY *.* C:\IMDISP\PALETTES [Enter]. 6. The IMDISP programs should now be in the IMDISP sub- directory of your hard disk. Making Directories for PCMIPS 1. Type C: [Enter] and then CD \ [Enter]. This takes you to the root directory of your hard disk. 2. With the prompt on your hard drive, type MD MIPS [Enter]. 3. Type CD MIPS [Enter]. Now while in this sub-directory (MIPS), make directories for AUX_FILE, BIN, and DOC. To do this, type MD AUX_FILE [Enter]. Repeat these commands by substituting BIN and DOC for the AUX_FILE. 4. Check to see if all your directories are in place by typing DIR [Enter]. You should see a path of \MIPS and the three directories that you have just added in the MIPS sub- directory. Copying the MIPS Programs 1. Now change to the CD-ROM by typing L: [Enter]. 2. Type DIR to access the directory and then strike [Enter]. 3. Type CD DOS\MIPS [Enter]. You should now be in the MIPS sub-directory. To check for this, type DIR [Enter]. 4. Now type COPY *.* C:\MIPS [Enter]. 5. Remain in the L: directory and then copy the three sub- directories (AUX_FILE, BIN, and DOC) of MIPS. To do this first change to their sub-directory, i.e., CD AUX_FILE [Enter] and then type: COPY *.* D:\MIPS\AUX_FILE [Enter]. Repeat these commands until you have copied the BIN and DOC sub-directories. 6. The MIPS programs should now be in the MIPS sub-directory of your hard disk. Putting IMDISP and MIPS in the DOS Path 1. Before IMDISP and MIPS can run, they must be put in the DOS path of the AUTOEXEC.BAT file. 2. Use the EDLINE or DOS editor to put \MIPS\BIN in the DOS path. 3. Also place \IMDISP in the DOS path and set the environment as set imdisp= (to your video card). 4. Mips can now be accessed by typing PCMIPS [Enter]. Imdisp can be accessed by typing either IMDISP44 [Enter] or IMDSP44X [Enter]. SELECTING AN IMAGE USING IMDISP 1. Insert the JEdI B disc in the CD-ROM drive. With the "C:\>" (where you have placed the IMDISP sub-directory) prompt on your screen, type IMDISP44 [Enter] or IMDSP44X [Enter] (use 44X for a Paradise card). 2. You should see the command prompt. Type FIL [Enter]. 3. Now change the active drive to the CD-ROM. Type D (Drive) and then [Enter] and then L [Enter]. 4. Select the IMAGERY sub-directory "3 [Enter]." Select the PLANETS sub-directory "6 [Enter]." Now select JUPITER "3 [Enter]" and IO "8 [Enter]." 5. The path should read "L:IMAGERY\PLANETS\JUPITER\IO." Select image "7" (C1637752). Wait until the command line appears and then type DIS [Enter]. You have now accessed an image using IMDISP. SOME IMDISP COMMANDS FILE or FIL Once in IMDISP, you can type FIL or FILE [Enter] at the command prompt for a list of files in the current sub-directory. If they will not fit on one screen, you will have to type N [Enter] to see more. Typing in the number that precedes a file and pressing the [Enter] key will load the file into memory. Q Whenever you are at the Option prompt, typing Q [Enter] will return you to the command prompt. DIS You may display the image only at the command prompt. To do this type DIS [Enter]. Actually, you are only displaying part of the image, because the program represents each sample in the image as one pixel on the screen, and most displays do not display 800 by 800 pixels. To see the entire image, you can type DIS SUB 2 [Enter] which displays a sub-sample of every other line and every other sample. ZOOM The zoom command allows you to enlarge parts of the image. This could be used in a presentation introducing the concept of pixels and brightness values. Type DIS ZOOM 5 [Enter] to see a magnification of five. SL and SS With further exploration, you can display a particular area of the image using the SL and SS commands to specify the "starting line" and "starting sample" which will be the upper left hand pixel of your display. BROWSE If you want to sit back and browse through all the images in the current sub-directory, type BROWSE or BRO *.* [Enter]. This command will display each image in the sub-directory one after the other with the file name shown in the upper left corner of the screen after the image is displayed. Once you have selected an image to manipulate, make a note of its filename. QUIT Type QUI [Enter] to quit IMDISP (this command may have to be repeated). CONTRAST STRETCHING ACTIVITY Background If you look closely enough at the images from the Voyager spacecraft, you will see that they are composed of many tiny boxes. These boxes are called pixels, and they can have different brightnesses. The brightness of each pixel has a value from zero (black) to 255 (white). Depending on the object, the lighting, and the exposure time, the image may have a great range of brightness in it or a very narrow range. If the range of brightness is very small, the image has low contrast. It looks very flat and details are hard to see. Using the computer, however, you can increase the amount of contrast. This is called "contrast stretching." A graph showing the number of pixels for each brightness value is called a histogram. There are usually more pixels of average brightness values than there are pixels with very low or very high brightness values, so ordinarily the histogram has a "bell" shape. In a low contrast (flat) image, the brightness values would be clustered around one value, and the "bell" on the histogram would be narrow. Contrast stretching redistributes the brightness values of each pixel, so the resulting histogram would have a wider "bell." A contrast stretched image makes better use of the available brightness of the display. Procedure Accessing the Data 1. Insert the JEdI B disc in the CD-ROM drive. With the C:\> type CD IMDISP [Return] to get into the IMDISP directory. Now with the C:\IMDISP prompt on your screen, type IMDISP44 [Return] or IMDSP44X [Return] (use 44X for a Paradise card). 2. You should see the command prompt. Type FIL [Enter]. 3. To change the active drive to the CD-ROM, type D (Drive) [Enter] and then L [Enter]. 4. Select the IMAGERY sub-directory 3 [Enter] then select the PLANETS sub-directory 6 [Enter]. Now select 3 [Enter] (JUPITER) and 8 [Enter] (IO). 5. The path should read L:IMAGERY\PLANETS\JUPITER\IO. Type the number of the file that you will enhance (use # 7, C1637752), [Enter]). Displaying the Image Now you should see the command prompt again. Type DIS [Enter]. Displaying a Histogram 1. You should now see the image which you will be enhancing. Notice the contrast of the image. To see a histogram of the image, type HIS [Enter]. 2. When the histogram is displayed, observe the range of DN values. These DN values represent the brightness values of each pixel (see Introduction). The x axis represents the brightness values of the samples (pixels) in the original image from 0 to 255, and the y axis represents the number of pixels of each brightness (DN) value. Locate the DN values for the lower and upper edges of the "bell" and write down those numbers. Also note the DN value for the top of the curve. If there are two distinct humps on the histogram, use the range for the biggest of the two humps (toward the right side of the graph) for your contrast stretching activity. Sub-Sampling the Image 1. The image at which you are now looking (from the command DIS) is actually only the upper left portion of the entire image. 2. Clear the old image by typing Erase [Enter]. 3. To see the entire image, type DIS SUB 2 [Enter]. This command tells the computer to display every other sample of every other line. (This is optional.) Contrast Stretching 1. To see the effect of contrast stretching, type SET DNLO 48 DNHI 192, [Enter] (where 48 and 192 are the low and high values you observed for the edges of the bell on the histogram). 2. Next type DIS or (DIS sub 2) [Enter] again to see the stretched image. 3. Type QUI [Enter] to quit the IMDISP program. Preparing for PCMIPS 1. To prepare for PCMIPS, first change to the sub-directory where you plan to store the prepared image (e.g. Type C: [Enter] and then CD IMAGES [Enter]). If a sub-directory to store the images does not exist, you can create one using the DOS command "md" (make directory), e.g., MD IMAGES [Enter]. 2. If you have not already done so, copy the program PREPARE.BAT from the JEdI A disc into this sub-directory. (Note: PREPARE.BAT is on the Jedi A disc. A printout of this batch file is found in APPENDIX A.) Using PREPARE.BAT 1. Make sure that you are in the sub-directory where your image resides. For example if the image is on the CD-ROM drive (usually L: ) type L: [Enter] and then CD \IMAGERY\PLANETS\JUPITER\IO [Enter]. This will ensure that the image will be accessed. The entire path name for the original image file is not necessary if its sub-directory is the current sub-directory for the L: drive [the CD-ROM]. In fact, the PREPARE program will probably not accept the entire path because it is too long. 2. Return to the C: drive and the images sub-directory by typing C:\IMAGES [Enter]. 3. Type PREPARE L:C1637752.img IOIMGONE [Enter]. This command will prepare the image #7 of IO (C1637752.img) as the new name you want give to the prepared image file and its label file (IOIMGONE is used as IO IMaGe ONE). Do not give the output file an extension. 4. At the prompt "Strike A key when ready," strike any KEY. Do not strike any keys again until the screen reads: "Preparation completed. Returning to DOS. D:\IMAGES>." 5. Allow the computer to work on this image. It will return you to the DOS prompt when it is finished processing the image. Do not enter any information until you are returned to the DOS prompt. Using PCMIPS for this Image 1. To create and save the contrast stretched image, use a program called PCMIPS. Type PCMIPS [Enter] at the DOS prompt/sub-directory where you have installed MIPS. 2. You should see a list of operations that PCMIPS can perform. Pressing the Enter key should show you the bottom of the list. 3. Type 29 [Enter] to select the STRTCH (contrast stretch) option. 4. When you see the "FILES>" prompt, type in strech1=IOIMGONE [Enter]. This names the image you want to save (strech1) and tells the computer that it will be (= to) the enhanced image which you have just saved through the PREPARE.BAT program. Use eight letters maximum and an "=" (no spaces in the entire file name) to name these images. 5. When you see the prompt "Enter number of stretch intervals:", type 1 [Enter]. 6. When you see the prompt "Enter IN_LOW, IN_HIGH, OUT_1, OUT_2 for interval 1:" type in the brightness value for the low end of the histogram, a comma, the brightness value for the high end of the histogram, another comma, 0, another comma, and 255 [Enter] (e.g. "48,192,0,255 [Enter]"). In the example, you would be telling the computer to take brightness values from 48 to 192 and spreading them out between brightness values from zero to 255. 7. This will take some computer time. When you see the "FILES>" prompt again, press the [Enter] key. 8. When the computer asks you if you want to display your image, type Y [Enter]. 9. When you see the command prompt, you are back in the IMDISP program, so type DIS [Enter] or DIS SUB 2 [Enter] to display your image. (DIS will display a larger but not complete image. DIS SUB @ will display a smaller but complete image.) 10. To quit IMDISP, type QUI [Enter]. 11. You should now be back in MIPS. Hold down the key and tap C to exit. FIRST DERIVATIVE (DIFFERENCE) ACTIVITY Background Digital images such as the ones from Voyager contain a lot of information that you cannot see at first glance. If you look closely at these images, you can see that they are made of thousands of tiny squares called pixels. Each pixel can be one of 256 different brightness or shades of gray. One of the advantages in having the images in digital form is that you can use a computer to enhance them to bring out the unseen details. One such technique is called "first derivative" or "first difference." It is a type of edge enhancement which detects differences in brightness values in the image and emphasizes them. It works by comparing each pixel (or "sample") to its neighbor. Where it detects no difference, it makes the pixel gray. Where it detects an increase in brightness, it makes the pixel white. Where it detects a decrease in brightness, it makes the pixel black. The result is an image which is gray except for the places where there is a difference in the brightness - i.e. an "edge." Procedure Finding and accessing the Image 1. Move to the sub-directory where your enhanced images are stored. To do this use the DOS CD command (e.g. CD IMAGES or CD\IMAGES). You will be using IOIMGONE, the # 7 image from the IO sub-directory prepared by PREPARE.BAT. 2. Run the Image Display program by typing IMDISP [Enter]. 3. You should see the command prompt. Type FIL [Enter]. 4. Find the image you want to enhance by the same procedures you used in the first activity. In this case you will be accessing the # 7 image of the IO file. 5. Now you should see the command prompt again. Type DIS [Enter]. 6. You should now see the image you will be enhancing. 7. You are actually looking at only the upper left portion of the entire image. To see the entire image, type DIS SUB 2 [Enter]. This command tells the computer to display every other sample of every other line. 8. Type QUI [Enter] to quit the IMDISP program. PREPARE.BAT 10 NOTE: Only do this if you have not prepared this image before using PREPARE.BAT. Follow the instruction for using PREPARE.BAT found under Appendix A.. PCMIPS for the First Derivative PCMIPS: 1. To create and save a first derivative image, use PCMIPS. Type PCMIPS [Enter] at the DOS prompt. 2. You should see a list of operations that PCMIPS can perform. Press [Enter] to see the remainder of the menu. 3. Type 3 [Enter] to select the DERIV (first derivative) option. 4. When you see the "FILES>" prompt, type in deriv1=IOIMGONE [Enter]. This names the image you want to save (deriv1) and tells the computer that it will be (= to) the enhanced (IOIMGONE) image. Use eight letters maximum and an "=" (no spaces) to name these images. 5. The computer will prompt you for parameters with "PARAM>". Type HORZ, IADB=40 [Enter] (be sure to type in the comma and the space for this command). This will enhance horizontal edges in the image and add a brightness value of 40 from the original image. 6. When you see the "FILES>" prompt again, press the [Enter] key. 7. When the computer asks you if you want to display your image, type Y [Enter]. 8. When you see the command prompt, you are back in the IMDISP program, so type DIS [Enter] to display your image. 9. Note the difference between this image and the original. Write down your observations. Explain in your own terms what you think has happened and what the computer did. 10. Your image will look "flat." Now type HIST to perform a histogram. Note the histogram and now type SET DNLO 16 DNHI 64 [Enter]. 11. Now type DIS and the image will be displayed with more contrast. 12. If you have time, you may also want to experiment with different values for the IADB or try a vertical or diagonal enhancement by typing VERT or DIAG in place of HORZ at the "PARAM>" prompt. 13. To quit IMDISP, type QUI [Enter]. 14. You should now be back in IMDISP. Hold down the key and tap "C" to exit. EDGE ENHANCEMENT P, type QUI [Enter]. 14. You should now be back in IMDISP. Hold down the key and tap "C" to exit. EDGE ENHANCEMENT (LAPLACIAN TRANSFORM) ACTIVITY Background Edge enhancement detects differences in brightness values in the image and emphasizes them. The type of edge enhancement you will be doing in this activity works by comparing the brightness of neighboring pixels in the image and looking for differences. Where it detects a difference, that is an edge, it makes the pixel on the brighter side of the edge brighter and makes the pixel on the darker side of the edge darker. The result is an image in which the edges are more pronounced. Keep in mind that the "edges" in the image are boundaries between areas of different brightness and may or may not represent physical surface features. Procedure Finding and accessing the Image 1. Move to the sub-directory where your enhanced images are stored. To do this use the DOS CD command (e.g. CD IMAGES or CD\IMAGES). You will be using the IOIMGONE again. 2. Now you should see the command prompt again. Type DIS [Enter]. 3. You should now see the image you will be enhancing. 4. You are actually looking at only the upper left portion of the entire image. To see the entire image, type DIS SUB 2 [Enter]. This command tells the computer to display every other sample of every other line. 5. Type QUI [Enter] to quit the IMDISP program. PREPARE.BAT NOTE: Only do this if you have not prepared this image before using PREPARE.BAT. Follow the instruction for using PREPARE.BAT. See Appendix A. PC MIPS for Edge Enhancement 1. To create and save an edge enhanced image, use a program called PCMIPS. Before you access PCMIPS, make sure that you are in the same sub-directory as the image you saved from the PREPARE.BAT. When you are in the correct sub-directory, type PCMIPS [Enter] at the DOS prompt. 2. You should see a list of operations that PCMIPS can perform. Press the [Enter] key to get to the command line. 3. Type 4 [Enter] to select the EDGENH (edge enhancement) option. 4. When you see the "FILES>" prompt, type in the name you want to give your enhanced image (eight letters maximum), an "=" (no spaces), the name of the image file you are going to enhance, and press the [Enter] key (e.g. edge1=IOIMGONE [Enter]). 5. The computer will prompt you to enter the fraction of Laplacian transform to be added. You may want to experiment with different fractions later, but for now type 0.5 [Enter]. This number affects how much edge enhancement will be added to the image; the higher the number, the greater the enhancement of the edge. 6. When you see the "FILES>" prompt again, press the [Enter] key. 7. When the computer asks if you want to display your image, type Y [Enter]. 8. When you see the command prompt, you are back in the IMDISP program, so type DIS [Enter] to display your image. 9. Note the difference between this image and the original. Write down your observations. Explain in your own terms what you think has happened and what the computer did. 10. If your image looks "flat," you may want to go back later and perform a "contrast stretch" using the instructions for that activity. If you have time, you may also want to experiment with different values for the fraction of Laplacian transform to be added. 11. To quit IMDISP, type QUI [Enter]. 12. You should now be back in IMDISP. Hold down the key and tap "C" to exit. HIGH-PASS FILTRATION ACTIVITY Background One of the advantages of digital images is that you can use a computer to enhance them to bring out the unseen details. One such technique is called "high-pass filtration." Within most images, there are areas where the rate of change in pixel brightness is high and other areas where the rate of change is low. Low-pass filtration emphasizes the areas where the rate of change is low, bringing out large areas of gradual differences. High-pass filtration emphasizes the areas of high rate of change, bringing out fine detail and edges. Procedure PCMIPS for High-Pass Filter 1. View the image as you have done in the first three exercises. 2. To create and save a high-pass filtered image, use PCMIPS. Change to the sub-directory in which your IOIMGONE image is and then type PCMIPS [Enter] at the DOS prompt. 3. You should see a list of operations that PCMIPS can perform. Press the [Enter] key for the command line. 4. Type 6 [Enter] to select the FLT8B (filters) option. 5. When you see the "FILES>" prompt, type in the name you want to give your enhanced image (eight letters maximum), an "=" (no spaces), the name of the image file you are going to enhance, and press the [Enter] key (e.g., filter1=IOIMGONE [Enter]). 6. The computer will prompt you for parameters with "PARAM>." Type HPF [Enter]. This will select high-pass filtration. 7. The computer will again prompt you with "PARAM>." Type LINE=9, SAMP=9 [Enter]. This sets the size of the areas that the computer will analyze for changes in brightness. In this case, the computer will be analyzing areas of five pixels wide by five pixels high. The optimum area depends on the image. You can experiment with different area sizes later by changing the LINE and SAMP values. You may also want to experiment with adding low and high DN (brightness values) to this parameter line to screen out the extremes of brightnessfrom the analysis (e.g., "LINE=5,SAMP=5,LOW=112,HIGH=144 [Enter]"). 8. When you see the "FILES>" prompt again, press the [Enter] key. 9. When the computer asks if you want to display your image, type Y [Enter]. 10. When you see the command prompt, you are back in the IMDISP program. Type DIS [Enter] to display your image. 11. Note the difference between this image and the original. Write down your observations. Explain in your own words what you think has happened and what the computer did. 12. If your image looks "flat," you may want to go back later and perform a "contrast stretch" using the instructions for that activity. 13. To quit IMDISP, type QUI [Enter]. 14. You should now be back in IMDISP. Hold down the key and tap C to exit. QUESTIONS FOR ALL ACTIVITIES 1. Describe how your enhanced image looks compared to the original image. 2. How do the various image enhancements differ from each other? 3. What do you think are the advantages of your group's enhancement technique? 4. What are the advantages of the other techniques? 5. How might the features in an image affect your choice of enhancement technique? What images might be good to test your hypothesis? 6. Note the differences between the original image and the ones manipulated and then stretched. Write down your observations. Explain in your own terms what you think has happened and what the computer did. ANALYSIS Each group will compare its enhanced image to others and discuss the value of the particular process which they can then share with the entire class. CONCLUSION Students should conclude that image processing can reveal information in an image and that different enhancement techniques yield different results giving scientists a choice of tools to use in analyzing images. EXTENSIONS Depending on the ability level of the students, the size of the class, and availability of computers systems, students may extend their activity to enhancement of other Voyager images. Students may also research books and magazine articles on how specific enhancement techniques are used in the field and what new techniques have been developed by scientists to learn more about the universe. REFERENCES Jensen, John R., Introductory Digital Image Processing. Englewood, Cliffs, NJ: Prentice-Hall, 1986. McEwen, Alfred S. and Soderblom, Laurence A., "Imaging - Pixels, not Pictures," The Planetary Report, Jan/Feb 1984, 6-10. Prentice, Gary S., "Do-It-Yourself Image Processing," and "Practical Image Processing," Sky and Telescope, August 1988, 142-146, 184-185. Time-Life Books, Inc.,eds. "Electronic Manipulations," The Visible Universe. Alexandria, Va.: Time-Life Books, 1990. MAGAZINES Scientific American, Sky and Telescope, Astronomy, Smithsonian, Planetary Report, NASA Report to Educators. ORGANIZATIONS NASA Teacher Resource Centers Educational Technology Branch, Educational Affairs Division Mail Code XE NASA Headquarters Washington, DC 20546 (202) 453-8388 The Planetary Society 65 North Catalina Avenue Pasadena, CA 91106 Astronomical Society of the Pacific 390 Ashton Avenue San Francisco, CA 94112 Office of Education, P-700 National Air and Space Museum Smithsonian Institution Washington, DC 20560 (202) 786-2106 BOOKS Castleman, Kenneth R. Digital Image Processing. Englewood Cliffs, NJ: Prentice-Hall, 1979. Davis, John C., 1986, Statistics and Data Analysis; John Wiley and sons; N.Y. 646 pp. Holzmann, Gerald J, and AT&T Bell Laboratories Staff. Beyond Photography - The Digital Darkroom. Englewood Cliffs, NJ: Prentice-Hall, 1988. APPENDIX A Prepare Batch File Here is the PREPARE.BAT batch file which is used to prepare the original Voyager images for manipulation by PC-MIPS. You may have to create this file with a text editor (such as the DOS line editor, EDLIN) unless it is supplied to you on disk. It will be included on the Jedi A disc. (Note: The program below is typed here in all capital letters, it does not have to be this way when you enter it.) @ECHO OFF CLS ECHO (If you did not specify the image and output file names, press the "control.") ECHO and "C" keys at the same time to quit and start over. ECHO (e.g. PREPARE L:C2065572.IMG EUROPA1) ECHO ( After the next keystroke, no response to prompts is necessary.) PAUSE CLS ECHO %1 >COPIM.INF ECHO TEMP.IMG >>COPIM.INF ECHO 1 >>COPIM.INF ECHO 1 >>COPIM.INF ECHO X >>COPIM.INF ECHO X >>COPIM.INF ECHO 1 >>COPIM.INF ECHO 1 >>COPIM.INF ECHO TEMP.IMG >STRIPPER.INF ECHO %2 .IMG >>STRIPPER.INF ECHO %2 >>STRIPPER.INF ECHO N >>STRIPPER.INF ECHO Y >>STRIPPER.INF COPIM