Different Types of Artificial Satellites

There is different types of artificial satellites, each for different uses. For example :

 Weather satellites help meteorologists predict the weather or see what's happening at the moment. Typical weather satellites include the TIROS, COSMOS and GOES satellites. The satellites generally contain cameras that can return photos of Earth's weather, either from fixed geostationary positions or from polar orbits.

 





 



Communications satellites allow telephone and data conversations to be relayed through the satellite. Typical communications satellitesinclude Telstar and Intelsat. The most important feature of a communications satellite is the transponder - a radio thatreceives a conversation at one frequency and then amplifies it and retransmits it back to Earth on anotherfrequency. A satellite normally contains hundreds or thousands of transponders. Communications satellites are usually geosynchronous. Broadcast satellites broadcast television signals from one point to another.

        
       








  
Scientific satellites perform a variety ofscientific missions. The Hubble Space Telescope is themost famous scientific satellite, but there are many others looking at everything from sun spots to gammarays. ( See the article of the telescopes)

 
       

 

 

-> Hiten scientific satellite  







Navigational satellites help ships and planes navigate. The most famous are the GPS NAVSTAR satellites, r escue satellites respond to radio distress signals.

 

             

 

-> NAVSTAR satellite

 

 






•   Earth observation satellites observe the planet for changes in everything from temperature toforestation to ice-sheet coverage.

 

           

-> ENVISAT 

 


 

 



Military satellites are up there, but much of the actual application information remains secret. Intelligence-gathering possibilities using high-tech electronic and sophisticated photographic-equipment reconnaissance are endless. Applications may include relaying encrypted communication, nuclear monitoring, observing enemy movements, early warning of missile launches, eavesdropping on terrestrial radio links, radar imaging, photography (using what are essentially large telescopes (see the article on the telescopes ) that take pictures of militarily interesting areas)

       






               Despite the significant differences between all of these satellites, they have several things in common. For example:

   All of them have a metal or composite frame and body, usually known as the bus. The bus holds everything together in space and provides enough strength to survive the launch.

           All of them have a source of power (usually solar cells) and batterie for storage. Arrays of solar cells provide power to charge rechargeable batteries. Newer designs include the use of fuel cells. Power on most satellites is precious and very limited. Nuclear power has been used on space probes to other planets. Power systems are constantly monitored, and data on power and all other onboard systems is sent to Earth stations in the form of telemetry signals.  All of them have an onboard computer to control and monitor the different systems. All of them have a radio system and antenna. At the very least, most satellites have a radio transmitter/receiver so that the ground-control crew can request status information from the satellite and monitor its health. Many satellites can be controlled in various ways from the ground to do anything from change the orbit to reprogram the computer. All of them have an attitude control system. The ACS keeps the satellite pointed in the right directi

The satellite's functional versatility is imbedded within its technical components and its operations characteristics. Looking at the "anatomy" of a typical satellite, one discovers two modules. Note that some novel architectural concepts such as Fractionated Spacecraft somewhat upset this taxonomy.

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