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SATELLITE LAUNCHING
INTRODUCTION
SATELLITE: A satellite is any object that orbits another object. In popular usage, the term 'satellite' normally refers to an artificial satellite.
The first artificial satellite, launched by Russia in the 1957.Since then, dozens of countries have launched satellites, with more than 3000 currently operating space craft going around the earth.
Artificial satellites can have range of missions, including scientific research, weather observation, military support, navigation, earth imaging and communications. In a communications context, a satellite is a specialized wireless receiver/transmitter that is launched by a rocket and placed in orbit around the earth
TYPES OF SATELLITES 
Satellites are classified as following types at the basis of their
working property:-
Astronomical satellites: These are used for observation of distant planets, galaxies, and other outer space objects.
Communications satellites: These are artificial satellites stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits.
Earth observation satellites : These satellites are specifically designed to observe Earth from orbit, similar to reconnaissance satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc.
Weather satellites : These are satellites that primarily are used to monitor the weather and/or climate of the Earth.
TYPES OF SATELLITE ORBITS
There are three basic kinds of orbits, depending on the
satellite's position relative to Earth's surface:
GEOSTATIONARY ORBITS :Geostationary orbits are orbits in which the satellite is always positioned over the same spot on Earth with an altitude of about 22,223 miles.
ASYNCHONOUS ORBIT : The scheduled Space Shuttles use a much lower, asynchronous orbit, which means they pass overhead at different times of the day. Other satellites in asynchronous orbits average about 400 miles (644 km) in altitude.
POLAR ORBIT : In a polar orbit, the satellite generally flies at a low altitude and passes over the planet's poles on each revolution. The polar orbit remains fixed in space as Earth rotates inside the orbit.
LAUNCHING OF SATELLITE INTO ORBITS
Placing a satellite into geosynchronous orbits requires
enormous amount of energy. The launch process can be
divided into two phase:
THE LAUNCH PHASE :
During the launch phase, the launch vehicle places the satellite into the transfer orbit an elliptical orbit that has at its farthest point from earth( apogee) the geosynchronous elevation of 22238 miles and at its nearest point (perigee) an elevation of usually not less than 100 miles.
THE ORBIT INJECTION PHASE :
The energy required to
move the satellite from
the elliptical transfer.
orbit into the geosynchronous
orbit is supplied by the
satellite’s apogee kick
motor (AKM). This is
known as the orbit
injection phase.
LAUNCH VEHICLE
Launch vehicle places the satellite into transfer orbit. There
are two types of launch vehicles:
EXPENDABLE ROCKETS :Expendable rockets are destroyed while completing their mission.
SPACE SHUTTLE : the space shuttle, which is reusable.
LAUNCHING STAGES
There are three stages to expendable space shuttle to
complete its job.
The first stage has a huge amount of liquid oxygen mixture, and solid fuel rocket, Turbo-boosters that produce a tremendous amount of flame and noise as the rocket lifts off. This stage lives the satellite at the height of about 49 miles of the surface of earth.
The second stage is a little more complex and when successfully completed, the satellite is left at the height of about 102 miles.
The third stage, then places the shuttle in the transfer orbit. Once the satellite is placed in its orbit, the rocket or its remnants are allowed to return to earth. The energy required to move the satellite from the elliptical transfer orbit into the geosynchronous orbit is supplied by the satellite’s apogee kick motor(AKM).
SATELLITE ALTITUDE
Looking up from Earth, satellites are orbiting overhead in
various bands of altitude . Proceeding roughly from the
nearest to the farthest, here are the types of satellites
whizzing around Earth:
80 to 1,200 miles -satellites, typically orbiting at altitudes from 300 to 600 miles (480 to 970 km), are used for tasks like photography
3,000 to 6,000 miles - Science satellites are sometimes in altitudes of 3,000 to 6,000 miles (4,800 to 9,700 km). They send their research data to Earth via radio telemetry signals.
6,000 to 12,000 miles - For navigation, the U.S. Department of Defense built the Global Positioning System, or GPS. The GPS uses satellites at altitudes of 6,000 to 12,000 miles to determine the exact location of the receiver
ORBIT VELOCITY
Orbital velocity is the velocity needed to achieve balance between gravity's pull on the satellite and the inertia of the satellite's motion -- the satellite's tendency to keep going. A rocket must accelerate to at least 25,039 mph (40,320kph.) to completely escape Earth's gravity and fly off into space
The orbital velocity of the satellite depends on its altitude above Earth.The nearer Earth, the faster the required orbital velocity. At an altitude of 124 miles (200 kilometers), the required orbital velocity is just over 17,000 mph (about 27,400kph).
To maintain an orbit that is 22,223 miles (35,786 km) above Earth, the satellite must orbit at a speed of about 7,000 mph (11,300kph). That orbital speed and distance permits the satellite to make one revolution in 24 hours. Since Earth also rotates once in 24 hours, a satellite at 22,223 miles altitude stays in a fixed position relative to a point on Earth's surface. Because the satellite stays right over the same spot all the time, this kind of orbit is called "geostationary." Geostationary orbits are ideal for weather satellites and communications satellites
APPLICATION IN COMMUNICATION:
Any information can be transmitted or received easily with the help of communication satellite. An information transmit from the originating ground station in the signal form , which is received by communication satellite & after this satellite transmit it to the destination ground station . The transmission system from the earth station to the satellite is called the uplink, and the system from the satellite to the earth station is called the downlink.
IN GPS
The Global Positioning System (GPS) is a space-based global navigation satellite system (GNSS) that provides reliable location and time information in all weather and at all times and anywhere. A GPS receiver calculates its position by precisely timing the signals sent by GPS satellites high above the Earth.
Three satellites might seem enough to solve for position since space has three dimensions and a position near the Earth's surface can be assumed. However, even a very small clock error multiplied by the very large speed of light the speed at which satellite signals propagate — results in a large positional error. Therefore receivers use four or more satellites to solve for the receiver's location and time. The very accurately computed time is effectively hidden by most GPS applications, which use only the location..
LIFE SPAN OF SATELLITE
The useful lifetime of a satellite can range from a few months to 7-8 years or more. This rarely depends on the quality of the mission-related equipment; usually, it is limited by the amount of fuel on board or, in some cases, by degradation of solar cells or loss in battery capacity.
Many factors can contribute to the slowing down or even the death of a satellite. The atmosphere in space is less dense than on Earth and approximately 124 miles above the Earth. There is no part of the space's atmosphere which is an absolute vacuum. In time, a satellite will lose velocity or speed and won't be able to go high enough and will eventually fall out of orbit.
Falling into the atmosphere means that the satellite will be exposed to intense heat as it collides with large numbers of molecules and ions and this causing the satellite to burn up in flames even before it reaches Earth.
FUTURE OF SATELLITE SYSTEM
The nature of future satellite systems will depend on the demands of the market place the costs of manufacturing, launching, and operating various satellite configurations; and the costs and capabilities of competing systems - telephone conversations or television channels.
Advanced Communications Technology Satellite (ACTS) consists of a relatively large geosynchronous satellite with many uplink beams and many downlink beams, each of which covers a rather small spot on the earth. However, many of the beams are "steer able". The ACTS satellite is also unique in that it operates at frequencies of 30 GHz on the uplink and 20 GHz on the downlink. It is one of the first systems to demonstrate and test such high frequencies for satellite communications.
By planning the orbits carefully, some number of satellites could provide continuous contact with the entire earth, including the poles. By providing relay links between satellites, it would be possible to provide communications between any two points on earth, even though the user might only be able to see any one satellite for a few minutes every hour. Obviously, the success of such a system depends critically on the cost of manufacturing and launching the satellites.
CONCLUSION
With the help of satellite any information sends instantly at any place. Various task such as Mapping Locating environmental situations , Locating mineral deposits , finding crop problems etc. perform by satellite easily.
They are used in the fields of communications, in the areas of television, the Internet, and phones; observation, in the areas of espionage, and geology; and navigation, in the area of transportation as well as many topics and sub-topics.
The life and death of satellites are a very crucial factor to the world today. Every day, new discoveries are being made on how to make the launching and retrieving process easier and effective& economic.
Satellites are a very important part of our communication system and without it our daily life would be totally different.