By Gary Davis

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Launch">

A satellite is built in such a way that it is as light as
possible. This way it can carry more fuel with it, which
increases its life in orbit. The total weight is determined by
the rocket(s) that carry the satellite into space. The rocket is
able to bring a certain amount of weight into orbit and this is
something the manufacturer of the satellite has to take into
account when designing a new satellite.

In order to bring a satellite into space it needs to first enter
a low earth orbit (LEO). To get into LEO the rocket needs to
reach an altitude of at least 200 km (120 miles) and a speed of
no less than 29.000 km per hour (18.000 miles per hour). This is
the most difficult and expensive part of the launch of a
satellite. There is an enormous amount of energy needed to reach
LEO.

Generally 2 rocket stages are needed to bring a satellite into
LEO. The first rocket stage brings the rocket up into the
thinner air at higher altitudes and speeds the rocket up enough
to have the second stage bring the rest into LEO. Depending on
the mission a third rocket stage is used to bring the satellite
into higher orbits, for instance a geostationary orbit.

Operations in Space

Once they are in space satellites need to be completely
self-sustained, since they can not receive power from earth.
They also need to be able to survive the launch, which is not a
soft ride. Once in space the satellite needs to generate its own
power, being able to orient it self, dissipate heat, deal with
cosmic radiation and protect it self from micro meteors.

Power

Electricity is the main form of energy for all equipment on
board and for orientation. Fuel is on board for moving the
position or changing the orbit. In case of a geostationary
orbit, the satellite needs to be kept inside a imaginary box so
that it always stays in the same place as seen from earth. In
case of other satellites, fuel can be used to change the orbit,
or maintain an orbit. A satellite in low earth orbit for
instance still receives a tiny bit of friction from the
atmosphere which causes it to slow down and eventually fall back
to earth. A slight boast every now and then to speed the
satellite up ensures that it stays in orbit.

Electricity comes from solar panels with a battery back for when
the solar panels do not receive sunlight and for when the solar
panels aren’t deployed yet.

Orientation

Orientation of the satellite is extremely difficult. In case of
a geostationary satellite it is like aiming a light beam on a
dartboard that has been placed 300 feet away, while at the same
time going around the dartboard in 24 hours. When you do that,
you have a reference, the ground. A satellite doesn’t have
this fixed reference and needs to create this reference by it
self.

A satellite creates its own reference through the use of
spinning wheels. A spinning wheel has the property that the axis
maintains it position due to the centrifugal force as it spins.
- This effect can also be seen in a spinning top. It maintains
its upright position when it spins. - Slowing the wheels down or
speeding them up a bit is also used to change the orientation of
the satellite, hence ensuring that the antennas always point in
the direction of the covered area on the earth.

Heat Dissipation

Space is cold; its temperature is almost absolute zero. But
objects in space can be hot, especially when close to a hot
celestial body like the sun. Our very existence depends on the
energy the sun gives us. The same goes for satellites; their
main source of energy is the sun. A satellite heats up because
it is exposed to sunlight. Also the electronic equipment inside
the satellite generates heat.

On earth there are 3 ways to dissipate heat from a body. Through
convection heat energy can be given to the passing air which
then transports the heat away. Through conduction, which means
the heat is transferred to another body. Another possibility is
through radiation.

A satellite has no other option than to use radiation to
dissipate heat as there are no other bodies around and no air to
cool them. It radiates the heat energy through louvered panels,
meaning that they do not face the sun so that they don’t
collect heat, but just radiate the heat in the direction of
black space, which is very cold.

Cosmic Radiation and Micro meteor
Protection

The earth is protected by its atmosphere from most cosmic
radiation and small meteors. In space a satellite needs to have
its own protection. Shielding of all electronic equipment is
necessary, especially computer circuits which are so small that
very low levels of radiation can already do damage. A satellite
collides with very small meteors which damage solar panels and
other equipment that is exposed to space.

Even though small meteors do not disable a satellite, it does
have an impact on its life span. Solar panels will gradually
produce less power because more and more solar sells will be
disabled over time.

Another effect that radiation has is that materials can become
brittle. This effect can also be seen in plastics that have been
exposed to sunlight for a long time.

Over all a satellite has a hard time living in space. Even
though Space seems to be just an empty whole of nothing, it
actually is a very unfriendly environment full of invisible
damaging radiation and tiny particles (meteors) that are
dangerous because of their high speeds.

About the author:
Gary Davis is owner of href="http://www.dish-network-satellite-tv.ws/">Dish Network
Satellite TV, has several years experience in the Satellite
TV Industry and has written several articles on satellite TV.

Author : Gary Davis
Site : www.goarticles.com

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