Satellite Images - If you look at the surface of the Earth from your yard or street, you can only see a short distance. If you climb a tree or go to the top floor of your apartment building, you can see further. If you flew over your neighborhood in a plane, you could see still further. Finally, if you orbited the Earth, you would be able to see a very large area of the Earth. This is the idea behind satellites. To see things on a large scale, you need to get the highest view.
Today, we have satellites with many different types of instruments that orbit the Earth. With these satellites, we can see hurricanes. Weather forecasters can follow hurricanes as they move from far out in the oceans to shore. Weather forecasters can warn people who live along the coasts. Their advanced warning gives people time to prepare for the storm, which helps save lives. Satellites orbit high above the Earth in several ways. One of the most useful ways is called the geostationary orbit.
The satellite orbits at a distance of 36,000 km. It takes 24 hours to complete one orbit. Since the satellite and the Earth both complete one rotation in 24 hours, the satellite appears to “hang” in the sky over the same spot. In this orbit, the satellite stays over one area of the Earth’s surface. Weather satellites use this type of orbit to observe changing weather conditions. Communications satellites, like satellite TV, also use this type of orbit.
Another useful orbit is the polar orbit. The satellite orbits at a distance of several hundred kilometers. It makes one complete orbit around the Earth from the North Pole to the South Pole about every 90 minutes. In this same amount of time, the Earth rotates slightly underneath the satellite. In less than a day, the satellite can see the entire surface of the Earth. Some weather satellites use a polar orbit to get a picture of how the weather is changing globally. Also some satellites that observe the lands and oceans use a polar orbit.
The National Aeronautics and Space Administration (NASA) has launched a fleet of satellites to study the Earth. The satellites are operated by several government agencies, including NASA, the National Oceanographic and Atmospheric Administration (NOAA) and the United States Geological Survey (USGS). By using different types of scientific instruments, satellites make many kinds of measurements of the Earth.
- Some satellites measure the temperatures of the land and oceans.
- Some record amounts of gases in the atmosphere such as water vapor and carbon dioxide.
- Some measure their height above the oceans very precisely.
From this information, they can get an idea of the sea surface below.
- Some measure the ability of the surface to reflect various colors of light. This information tells us about plant life.
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