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Weather satellites take "pictures" of the atmosphere below, but not photographs. Sensors on the satellite measure energy waves that radiate and reflect from the Earth's atmosphere below. The energy waves include light waves, infrared waves, and microwaves. The sensors' energy wave data is then sent by radio to powerful computers on Earth. The energy wave patterns are translated by the computers and a corresponding image is generated for meteorologists to interpret. Variations in the energy wave patterns will indicate atmospheric conditions such as cloudiness, temperature, and moisture levels.

Not all satellites are the same. Some satellites, called geostationary satellites, circle the Earth at a very high orbit so that their speed matches the Earth's rotation. In relation to the Earth below, they appear to remain stationary. From their high point, geostationary satellites provide images of an entire hemisphere at once. Geostationary images allow meteorologists to track the development of large storms, like hurricanes and severe thunderstorms, over wide areas of the atmosphere.

Today, severe weather is observed all around the world using the geostationary satellites that are currently flying high in orbit. The United States has two: "GOES-East" and "GOES-West." The European Space Agency placed "Meteostat" in orbit. Japan has "Himawari," and India has "Insat." Together, these five geostationary satellites form the Global Atmospheric Research Program (GARP). Originally proposed by the United Nations, the GARP improved worldwide weather watching.

There are other satellites that make several orbits around Earth per day, passing over both the North and South poles on each orbit. These non-geostationary satellites, called polar-orbiting satellites, are in a low-orbit of only 530 miles above Earth. Every twenty-four hours they pass over the entire Earth's atmosphere as the planet rotates beneath them.

Polar-orbiting satellites were designed to monitor the entire atmosphere, recording precise measurements of the energy that Earth radiates and reflects into space. This data is interpreted by computers to make detailed models and images of atmospheric temperature, moisture level, and ozone layer integrity, as well as clouds.

 
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