Types of satellites
Navigation satellites
The GPS (global positioning system) is made up of 24 satellites that orbit at an
altitude of 20,000 km above the surface of the Earth. The difference in time for
signals received from four satellites is used to calculate the exact location of a
GPS receiver on Earth.
Communication satellites
These are used for television, phone or internet transmissions, for example, the
Optus D1 satellite is in a geostationary orbit above the equator and has a coverage
footprint to provide signals to all of Australia and New Zealand.
Weather satellites
These are used to image clouds and measure temperature and rainfall. Both
geostationary and low Earth orbits are used depending on the type of weather
satellite. Weather satellites are used to help with more accurate weather
forecasting.
Earth observation satellites
These are used to photograph and image the Earth. Low Earth orbits are mainly
used so that a more detailed image can be produced.
Astronomical satellites
These are used to monitor and image space. A satellite such as the Hubble Space
Telescope orbits at an altitude of 600 km and provides very sharp images of stars
and distant galaxies. Other space telescopes include Spitzer and Chandra.
International Space Station (ISS)
This is a habitable space laboratory. At an altitude of 400 km, the ISS travels at a
speed of 28,000 km/h and orbits the Earth once every 92 minutes. Scientists inside
the ISS are able to perform many valuable experiments in a microgravity
environment.
Worksheet - What are Satellites?
A satellite is a small body orbiting or circling a larger body. The complete path it
follows is called an orbit. The moon is an example of a natural satellite of the
earth. Manmade, or artificial satellites are placed into orbit by rockets or space
shuttles.
After World War II, the former Soviet Union successfully launched Sputnik, the
first artificial satellite, into space. In 1958, the United States launched its first
artificial satellite Telstar I into orbit. Since then, many more satellites were made
by different countries and launched into space.
These satellites help people in different ways. Communication satellites carry our
telephone calls. Weather satellites help meteorologists predict the weather. Earth-
survey satellites help scientists to study the earth's surface and the living things
on it.
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