Satellites

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					Satellites




Adam Friedrichsen
  Collin Frierson
  Jeremy Gragg
              Introduction
• Collin Frierson
  – Business MIS, Economics, Psychology
  – Server Support Group (OSU)


• Adam Friedrichsen
  – Business MIS, AFROTC
  – OSU Desktop Support


• Jeremy Gragg
  – Business MIS & Int. Bus., Computer Sci.
  – BSG, Sigma Phi Epsilon
                 Overview


•   History
•   Transmission
•   Orbits
•   Military Applications
•   Commercial Applications
•   Cost
•   Forward Error Correction
                            History


• Sputnik 1 – USSR
  – Oct 4 57’ – Jan 3 58’

• Explorer 1 - USA
  –   Jan 31 58’ – March 31 70’

• Technology grew from the Space Race
• Commercial and Military Applications
                              History
         Payloads                     Debris
Source   On                                      Decaye
                 Decayed      Total   On Orbit          Total
         Orbit                                   d


All      3,163        2,737   5,900      8,030   16,865   24,895



           All

           On Orbit              Decayed                  Total


                       11,193                    19,602    30,795
Transmission - Uplink
     • Uplink facilities transmit
       the original signal to the
       satellite.
     • Antennas are pointed at
       specific satellites to
       transmit.
     • Frequency ranges, specific
       satellites tune into specific
       frequencies.
       Transmission – Relay

• Satellites receive transmissions from the
  uplink station.
• Based on the signal frequency, the
  satellite relays and rebroadcasts the signal
  on another frequency.
Transmission – Downlink

     • All Satellite receivers are
       tuned to specific frequencies.
     • Most receivers need LoS
       (line of sight).
     • Receivers can be large (TV
       Dish) or small (XM Radio
       Receiver).
       Transmission Frequencies

BAND   UP-LINK (GHz)   DOWN-LINK (GHz)   ISSUES

C      3.7-4.2         5.925-6.425       Interference with ground links.

Ku     11.7-12.2       14.0-14.5         Attenuation due to rain.

Ka     17.7-21.7       27.5-30.5         High equipment cost.

L/S    1.610-1.625     2.483-2.500       Interference with ISM band.
        LEO – Low Earth Orbit
• Altitude: 124-1240 miles
  – Little, Big, Mega
  – All Shuttle Flights

• Plane: Varies
  – Sun-Synchronous Capability

• Period: 90 minutes – 3 Hours
  – Approximate Speed: 17,000 mph
        LEO – Low Earth Orbit
• Advantages:
  – Low Transmission Delay
  – Smaller Receiver Requirement

• Disadvantages:
  – Shorter Life
  – Smaller Coverage Area
     MEO – Medium Earth Orbit
• Altitude: 1241- approx. 22,239 miles
  – GPS, GLONASS Constellations


• Plane: Varies
  – Sun-Synchronous Capability


• Period: 2 – 12 Hours
GEO – Geosynchronous Earth Orbit
• Altitude: Approximately 22,240 miles
  – Weather, Telecommunications Relays


• Plane: Equatorial or Polar

• Period: 24 Hours
GEO – Geosynchronous Earth Orbit

• Hohmann Transfer

• Geostationary Transfer Orbits
Supersnychronous/Graveyard Orbit
• Above Geosynchronous Orbit




• Used for Storage and Dead Objects
           Military Applications

• Intelligence Gathering

• Battlefield Weather

• Communications Uplinks

• GPS – Navigation + Targeting
         Anti-Satellite Warfare


• Possessed Capability                  F-15 Eagle
  to Shoot Down LEOs
  Since Late 1950s

• F-15 ASATs Since
  mid-1980s

                         ASM-135 ASAT
Other Applications
     • GPS Technology
       – Owned by GM
       – Pinpoints specific location of
         vehicles.

     • XM & Sirius Radio
       – Recently Merged
       – Transmit exclusive radio
         content while maintaining
         excellent sound quality.
       – Reaches locations traditional
         radio signals cannot.
             Other Applications
• Internet Communications
  – Requires Southern Sky Line
    of Sight
  – Now reasonably fast, cheap
    and reliable ($50 for
    1.5Mbps/256 kbps)

• Weather Satellites
  – GOES-8
  – Monitors weather patterns,
    fires, and other
    environmental changes.
               Cost of Satellites
• Being sent into orbit
  – Construction, Liftoff &
    Maintenance Costs
  – Approximately $40-500 million
  – Shuttle missions can carry
    several satellites into orbit.
  – Crashes and other problems

• Cost Comparisons
  – Relative to other transmission media.
  – Benefits vast geographic separation
                 Hamming Code
• Forward Error Correction
  – Parity Bit based error detection
    and correction.
  – Can correct single bit errors
    but only detect multiple bit
    errors.
  – Even and Odd parity schemes.
• Example
    Data is sent as “1011” with parity bits applied. By
    checking the parity, we can determine if an error
    occurred:
                  0110011         0111011
                           Sources
•   http://en.wikipedia.org/wiki/Low_Earth_orbit
•   http://en.wikipedia.org/wiki/Medium_Earth_Orbit
•   http://en.wikipedia.org/wiki/Geosynchronous_orbit
•   http://liftoff.msfc.nasa.gov/academy/rocket_sci/satellites/hohma
    nn.html
•   http://en.wikipedia.org/wiki/Anti-satellite_weapon
•   http://www.tbs-satellite.com/tse/online/sat_sputnik_02.html
•   http://hubble.esa.int/science-e/www/area/index.cfm?fareaid=31
•   http://www.spacetelescope.org/images/html/heic0301a.html
Questions?

				
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posted:8/14/2011
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