Satellite Technologies in the Classroom
In May of 1998, the Wireless Communications World was set on its ear as the Galaxy 4 communications satellite spun out of its intended orientation. The incident not only served to expose some of the vulnerabilities in our high-tech society, but just exactly how pervasive the technology had become.
Satellite communications have become so much more than a means to get "cable TV" without the cable. As consumers, we continuously access information via satellite through the means of TV, radio, pagers, cellular phones, ATM machines and charge cards. While many of us appreciate and use the technology for these functions, vast resources of digital satellite communications lay largely unknown and unexplored.
In the summer of '98, I discovered the importance of many different applications of satellite technology as I had the opportunity to participate in two outstanding professional development activities. Through Florida SIFT (Summer Industrial Fellowship for Teachers), I was privileged to work on the Atlas Program for Lockheed Martin. The Atlas rocket deploys many of the communications satellites that we have come to rely upon. Besides this experience, I was also able to attend a Global Positioning Satellite workshop hosted by the University of Central Florida and funded by TRDA (Technological Research and Development Authority).
Satellites are typically deployed by means of a rocket booster under a payload faring containing the satellite spacecraft. Many different orbital configurations are used depending upon the nature of the work to be performed by the satellite. For instance, geosynchronous orbital patterns are used when it is desirable to have continuous access to only one certain portion of the globe.
By placing the spacecraft in a high enough orbit so that the revolutionary speed of the satellite is equal to the rotational speed of the earth, the spacecraft remains stationary relative to that point on the earth. The G'ES and METEOSAT satellites use this type of orbit.
Polar orbiting satellites orbit longitudinally around the earth in a fixed plane. By taking advantage of the earth's rotational movement beneath it, a polar orbiting satellite can scan the entire surface of the earth in a short period of time. P'ES and NOAA satellites are polar orbiting. Where continuous and complete earth coverage is required, constellations of satellites are established such as the NAVSTAR-GPS System.
While anyone can receive live feeds from our environmental satellites - provided they have an antenna and a receiver set to the correct frequency - the Internet abounds with downloadable satellite imagery (see p.60). Though the data is often not in real time, the ease of accessibility, the range and quantity of images, and the archival capabilities of the Internet make the use of satellite imagery a great educational activity.
For many students, the evening news weather report is the extent of their experience with satellite imagery. Pictures showing cloud formations and movement are very valuable to weather forecasting and storm tracking, but because they display only what the satellite is seeing in the visible spectrum of light, they constitute only a small portion of the data available from environmental satellites. Many of the satellites mentioned before have the ability to detect radiation beyond the limits of visible light, such as in the infrared spectrum. Infrared imaging provides an entirely different perspective of our world by measuring and displaying various levels of heat as well as locating areas of specific thermal events, such as volcan'es and forest fires.
Perhaps the most intriguing but least known uses for pictures from space deal with high-resolution photography. Developed during the Cold War, our ability to visually monitor the goings-on of friend and f'e has now reached incredible heights.
From the time of the Cuban Missile Crisis, where photographic evidence of nuclear armaments were provided from U2 spy planes, to our surveillance satellites of today where reading license plates from space is possible, high-resolution space photos are becoming more and more accessible to the common person.
One source of high-resolution photos is the Microsoft Terraserver. At this Internet site, you can find satellite photos for most of the populated regions of the U.S. and some of the more populated regions throughout the world, as well as distinctive landmarks such as the Parthenon in Greece or Yankee Stadium in the Bronx. While you won't necessarily be able to check out what the neighbors are doing in their back yard - the posted images are four to five years old - the resolution is good enough to view your street and house from space or at least what they looked like from space in 1994.
Global Positioning Satellites
Starting in the late 1970's the American Military began deployment of a constellation of satellites to be used for pinpoint navigation of the globe. Today, the NAVSTAR satellite constellation consists of 24 satellites on six different orbital planes.
Better known as GPS, global positioning satellites are located about 11,000 miles from earth, and transmit a fixed coded signal on a very accurate fixed time. Receivers on earth contain the same signal, which are synchronized with the satellites. As the receivers pick up the satellites' transmissions, they cross reference the signals and measure the lag time between them. Using this process, the GPS can then determine the distance the satellite must be from that point on earth.
Once a receiver has detected a satellite's signal and calculated the satellite's distance, the receiver is said to have "acquired" the satellite. To identify a spot on the earth by longitude and latitude, a GPS receiver uses a surveyor's technique known as triangulation, where three points are known. For this purpose, a receiver must have acquired at least three satellites. By acquiring four or more satellites, the user can also obtain information regarding the user's altitude.
Everybody can take advantage of this technology, since the military has graciously provided a consumer grade (less accurate) version, on a separate signal. The commercial GPS receiver models have an accuracy of about 100 meters and are available at many discount and sporting goods stores for less than $200. The U.S. military versions operate on a precise signal accurate to 1 meter or less and for what should be obvious reasons, are not available to the public. A commercial version that uses the Russian military's GPS constellation is also available.
Satellite communications have the potential to extend the limits of our classroom boundaries for, with its use, students have access to virtually every inch of the globe. While the technology naturally lends itself to geography and science, hands-on classroom activities using satellite data are easily developed and applied across all disciplines.
Cartography - Cartography is map-making. Aerial photography is the traditional source of the imagery used to construct maps. While this is probably not available to you and your students, high-resolution satellite photos are available. With the help of a computer design program with layering capability, your students can produce quick and easy maps of important areas in their community or any other place of interest. Math skills are used as students determine a scale for their map using known distances from the satellite image and translating them to the map.
City and Community Planning - High-resolution photos of particular areas of land to be developed may be acquired for the purpose of planning the layout of an intended community. Students can take the satellite photo of an area of land and identify traffic flow, tie-ins to existing roadways, and different zoning areas. In the same way, an existing city may be studied for proposing an addition to a major interstate corridor, utilities right of way, a shopping mall or a theme park.
The original and 3D versions of SimCity (Maxis) make an excellent companion resource to this activity, as students can then model their city development ideas.
Weather Pattern Analysis - Animated cloud formations provide opportunities for students to forecast weather on a daily basis. Weather histories, cross-referenced with satellite imagery, can be kept to be used for future forecasting. Thermal readings from ocean currents can likewise be used to forecast weather related events over longer periods of time (such as El Nio). Students can track storms such as tropical depressions and hurricanes from hour to hour to determine speed and bearing, independent of official weather reports. GPS receivers can measure linear distance between two points if their coordinates are known. The elapsed time between the images is the only other piece of information needed to calculate the storm's speed.
Identification of Landmarks and Features - Using a GPS receiver and mapping software (e.g., Street Atlas USA, Map & Go), students can plot features on a map such as buildings, landmarks or environmental habitats by walking around them and downloading the GPS path to the mapping program. With GPS location data of seismic events or volcan'es, students can plot these features on the map to derive their own patterns for analysis.
Steve Portz teaches technology at Space Coast Middle School, Cocoa, Florida.
Satellite Imagery FAQ
Microsoft's USGS Terraserver
NAVSTAR GPS Homepage
The Aerospace Corporations GPS Primer
Operational Significant Events Imagery Homepage
The Weather Underground
Current Satellite Photos
Street Atlas Product
Software for Garmen GPS Products
Garmen GPS Products
This article originally appeared in the 08/01/1999 issue of THE Journal.