Every few years, new satellite images of the earth's surface are acquired from remote sensors aboard a space craft. Because the technology associated with satellite imagery improves so rapidly, these new images generate a wave of excitement throughout the scientific community, representing an opportunity to view the earth's surface at a level of detail (resolution) and accuracy never achieved before. In what is being hailed by some ecologists as the best use of the NASA Space Program (e.g., studying planet Earth), a combined effort led by NASA is now underway to map roughly 80 percent of the Earth's topographical surface during an eleven-day mission. What makes this mission particularly important is that it represents the first opportunity to produce high resolution, accurate, three-dimensional digital maps for nearly the whole earth's surface. Although high-resolution (30 m) satellite images exist for some parts of the Earth (the US, much of Europe, Australia and New Zealand), the vast majority of our planet is not mapped at high resolution, and many areas lack reliable maps altogether. The reason behind this lack of maps is that most high-resolution satellite images have been taken in the visible spectrum, requiring sunlight and clear skies (tropical regions are notoriously cloudy). SRTM radar, by contrast, has long wavelengths that can penetrate clouds and create images based on electromagnetic signals outside the visible spectrum (i.e., independent of daylight). With the help of a dual-antenna imaging radar, which uses a 60m boom, scientists are now mapping terrain elevation in a single pass. This week's In The News focuses on the Shuttle Radar Topography Mission (SRTM). The nine resources listed above describe the mission and the methods used to map the Earth's surface.
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