Satellites
By: Sydney Perrca
What is a Satellite?
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A satellite is any object that orbits or revolves around another object. For,
example the moon is a satellite of Earth, and Earth is a satellite of the Sun.
The earth and the moon are natural satellites. An example of a man made
satellite is the Hubble space telescope. Man made satellites are highly
specialized tools that’s do thousands of tasks every day. Each of these
satellites has many parts, but two parts common to all satellites are called the
pay load and the bus.
The payload for a satellite is all the equipment a satellite needs to do its job.
This can include antennas, cameras, radar, and electronics. The payload is
different for every satellite.
The bus is the part of the satellite that carries the payload and all its
equipment into space. It holds all the satellite’s parts together and provides
electrical power, computers, and propulsion to the space craft. The bus also
contains equipment that allows the satellite to communicate with Earth.
Natural satellites
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This is a picture of the
moon orbiting Earth and
the Earth orbiting the
Sun. These satellites are
natural satellites. (You
have to go into the slide
show feature to see the
heavenly bodies orbit
around each other).
Satellite pictures
The many uses of satellites
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Astronomy satellites: An astronomy satellite is a telescope orbiting around
Earth. Because it is in orbit around Earth, the satellite’s vision is not clouded
by the gases that make up the Earth’s atmosphere, and its infrared imaging
equipment is not confused by the heat of the Earth. Therefore, Astronomy
satellites can observe objects farther in space than a telescope of similar
strength on Earth. An example of an astronomy satellite is the Hubble Space
Telescope. Astronomy satellites have many different applications which
include, uses involving making star maps, studying mysterious phenomena
such as black holes and quasars, taking pictures of the planets in the solar
system, and making maps of different planetary surfaces.
Atmospheric Studies satellites: Atmospheric studies satellites were some of
the very first satellites launched into space. They generally have low Earth
orbits so that they can study the Earth’s atmosphere. An example of an
atmospheric studies satellite was Alouette. Alouette was the world’s first
atmospheric studies satellite, which was launched by Canada to study the
Earth’s ionosphere. Canadian scientists were trying to learn about the aurora
borealis.
The many uses of satellites
continued….communication
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Communication satellites: Communications satellites allow radio,
television, and telephone transmissions to be sent live any where
in the world. Before satellites, transmissions were difficult or
impossible at long distances. The signals, which travel in straight
lines, could not bend around the round Earth to reach a
destination. Because satellites are in orbit, the signals can be sent
instantaneously into space and then redirected to another satellite
or directly to their destination. The satellite can have a passive
role in communications like bouncing signals from the Earth
back to another location on the Earth, while some satellites carry
electronic devices called transponders for receiving, amplifying,
and re – broadcasting signals to Earth. Communications satellites
are often in geostationary orbit but they can also be in highly
elliptical orbits. This type of orbit is roughly egg shaped, with
the Earth near the top of the egg.
The many uses of satellites
continued…
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Navigation satellites: Satellites for navigation were developed in
the late 1950’s as a direct result of ships needing to know exactly
where they were at any given time. The idea for navigation began
with the launch of Sputnik 1 on October 4, 1957. The Navstar
satellites are examples of navigation satellites.
Reconnaissance satellites: Reconnaissance satellites are used to
spy on other countries. They provide intelligence information on
the military activities of foreign countries. These satellites can
even detect missile launches or nuclear explosions in space.
Reconnaissance satellites can pick up and record radio and radar
transmissions while passing over a country. Finally, they can be
used as an orbital weapon by placing war heads on a low orbit
satellite to be launched at a ground target.
The many uses of satellites
continued…
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Remote Sensing satellites: Remote sensing is observing and
measuring our environment from a distance. So, remote sensing
satellites are usually put into space to monitor resources
important for humans. For examples, remote sensing satellites
might track animal migration, locate mineral deposits, watch
agricultural crops for weather damage, or see how fast the forests
are being cut down. All of these things can be done from space
because a satellite in orbit can normally take photographs of
larger expanses of land all over the world.
Search and Rescue satellites: Search and rescue satellites are
designed to provide a way for vessels at sea and in the air to
communicate from remote areas. These satellites can detect and
locate emergency beacons carried by ships, aircrafts, or
individuals in remote dangerous areas.
The many uses of satellites
continued…
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Space Exploration satellites: Space exploration satellites
are not really satellites but are better known as space
probes. A satellite is defined as something that’s
orbiting something else, but space probes instead travel
deep in the solar system. However, they are similar to
orbiting satellites in design and function. On their
journeys, space probes send back detailed pictures and
other data of far away planets and other stellar
phenomena. An example of a space exploration satellite
is NASA’s Galileo.
Weather satellites: Citizens and Meteorologists rely on
weather satellites for reliable weather information.
LOW earth orbit
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A Low Earth Orbit is an orbit in which satellites
revolve around Earth at an altitude between 350 – 1400
above the Earth’s surface. Orbits lower than this are not
stable, and will decay rapidly because of the
atmospheric drag. Satellites in Low Earth orbits travel
at 27, 400 km/hr (8 km/s), this is one revolution in one
and a half hours. A Low Earth orbit is very useful for
communications satellites because of its proximity to
Earth. It requires less energy to place a satellites into a
LEO and the satellite needs less powerful transmitters
for data transfer, the down side is that a network of
satellites are required to provide continuous coverage.
Picture of low earth orbit
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This is a picture of a
satellite in low earth orbit
around the Earth. (You
can view the satellite
revolve around the Earth
using the slide show
feature).
Geosynchronous orbit
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A geosynchronous orbit is an orbit that has the same
rotational period and direction as the rotation of the
Earth. A satellite in geostationary orbit circles the Earth
once each day. The time it takes for a satellite to orbit
the Earth is called its period. For a satellite’s orbit
period to be one sidereal day, it must be approximately
35, 786 kilometres above the Earth’s surface. When a
geostationary satellite is viewed from Earth, it appears
to stay in the same spot and never move. For this to
happen the satellite must be placed directly over the
Earth’s equator. Otherwise, from the Earth the satellite
would appear to move in a north-south line every day.
Geosynchronous orbit
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This is a picture of a
satellite in
geosynchronous orbit.
Global positioning system
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The global positioning system is a constellation of twenty seven earth
orbiting satellites (twenty four which are operational and three extras in case
one fails). The U.S military developed and implemented this satellite network
as a military navigation system, but soon opened it up to everyone else. Each
of these 3,000 – to 4,000 pound solar powered satellites circles the Earth at
about 12,000 miles, making two complete rotations every day. The orbits are
arranged so that at any time, anywhere on Earth, there are at least four
satellites visible in the sky. A GPS receiver's job is to locate four or more of
these satellites, figure out the distance to each, and use this information to
deduce its own location. GPS receivers use triangulation of the GPS satellites’
navigational signals to determine their location. The satellites provide two
different signals that provide different accuracies. Coarse – acquisition code is
intended for civilian use and has a typical accuracy of about one hundred
meters. The military’s precision code provides an accuracy of about 20
meters. GPS satellites are controlled at the GPS Master Control Station
located at Falcon Air force base outside Colorado Springs, Colorado. The
ground segment also includes four active tracking ground antennas and five
passive tracking monitor stations.
GPS Pictures
Bibliography
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http://spacelink.nasa.gov/Instructional.Material
s/Curriculum.Support/Space.Science/Satellites/
.index
www.gpsy.com/gpsinfo/
www.encyclopedia.com
Interpreting satellite
photographs, #1-3
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1. Picture A was taken in geosynchronous orbit because you can
see the curvature of the Earth and a great amount of land is
viewed in the picture.
2. The advantages of photograph A is that there is greater area
of land viewed and both hurricanes and the tropical storm can
be viewed in the photograph as well there direction can be
viewed more easily. The advantages of picture B are that the
exact location of the storm can be determined more easily.
3. The information discovered in the photographs can be put to
use determining the location and direction of the storms and
warning the people who live in the areas where the storms might
hit.