|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
|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:
The European Space Agency
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
|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.