3L - Satellite Communication Systems

3L - Satellite Communication Systems

1. GPS

   • Uses NAVSTAR Contellation
     • 24 satellites
     • Orbits twice a day
     • Minimum of 4 satellites in view at any point
   • Communicates with at least 3 satellites
   • Uses trialeration
     • Calculates distance to each satellite
     • Determines its own location
   • Advantages
     • Accuracy - 30cm
     • Finds lost people
   • Disadvantages
     • Blindsopts
     • Affected by atmospheric conditions

2. Weather

   • Monitor conditions such as:
     • Snow cover
     • Pollution
     • Hot/cold water movements
     • Smog
     • Weather patterns
   • Geosynchronous Orbit
     • 37000 km height
     • Follows line of equator
     • Used to watch cloud formations
   • Low Earth Orbit
     • Follow north-south and south-north pole orbits
     • 850 km height
     • High quality photography
     • Thermal and infrared images
     • Can calculate land and water temperatures
   • Advantages
     • Monitoring fires
     • Can warn against hurricanes
     • Monitor energy usage
     • Can warn about sand and cloud movement
   • Disadvantages
     • Expensive
     • Not 100% accurate
     • Privacy conncerns about photographs

3. Satellite Television

   • Lots of channels available due to high bandwidths
   • Set-top box
     • Required to decode signals
     • Viewers can only view channels they've subscribed to
     • Decompresses signals
   • Satellite dish
     • Specialised aeiral
     • Receives microwave signals
   • Signal is broadcasted using DBS
     • Direct Broadcast Signal
     • Encrypted
     • Compressed
   • Advantages
     • Hundreds of channels
     • Signals in remote areas
     • Pay per view for single programmes
   • Disadvantages
     • Equipment is expensive
     • Need extra set-top box for each TV
     • Interferance from severe weather
     • Satellite dishes are unslightly