GLOBE high school and middle school students in Canutillo and El Paso, Texas study satellite images

Students at Canutillo High School in Canutillo, Texas and Slider Middle School in El Paso, Texas have been involved in the GLOBE (Global Learning and Observations to Benefit the Environment) Program for several years. As part of their GLOBE instruction teachers Joel Gilbert (Canutillo HS) and Sharon Mitchell (Slider MS) introduce their students to the basic concepts of remote sensing. Both Gilbert and Mitchell\´s courses include the study of satellite imagery. The students are first shown how the images are composed of tiny dots called "pixels", and that a pixel represents the instantaneous field of view of the ground surface imaged. Students are also taught that the ground surface area represented by one pixel in a satellite image is called "ground resolution\´\´ and that the greater the number of pixels per inch, the greater the resolution. The students also learn that satellites transmit these pixel images to ground stations as digital signals, which represent the ground surface being imaged. It is through this lesson, ground surface reflectivity and light\´s behavior as it is sent back to a satellite\´s sensors, that Gilbert is able to build his course upon the TEKS (Texas Essential Knowledge and Skills) standards with relevant instruction. In this lesson, a grayscale image, which may vary in tone, is presented to the class. Then false color is added to emphasize a particular feature, such as vegetation. The class is then introduced to the electromagnetic spectrum and is shown how different wavelengths of light produce the false color images that appear in satellite imagery. Gilbert\´s IPC (integrated physics and chemistry) classes study the properties of light as part of their course work, and since satellite sensors operate by picking up the way light is reflected from various surfaces, it is easy for him to incorporate the studying of these images into his lesson plans. For the last several years, Mitchell has been studying remote sensing with her eighth grad- e classes at Slider Middle School. Using a set of six Landsat images of El Paso that she received from PACES (Pan American Center for Environmental Studies) at UTEP, for the years 1984, 1988, 1991, 1994, 1997 and 2001, she instructs the students (working in teams of two) to study the changes (urban sprawl) that had taken place over that seventeen-year period. First, she has the students tape transparent sheets over the images and then gives them a list of major streets and sites e.g. their school to identify and label. They are then asked to study the images to see which year each site first appeared on the image. Through studying and comparing the images the students are able to see how much change has taken place. Both Gilbert and Mitchell end their lessons discussing how urban sprawl puts a strain on area water supplies, and what, given the crisis drought situation in the west, what the future consequences can be