compressed recent trend
TRANSCRIPT
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RECENT TRENDS IN SPACECOMMUNICATION
THE ROLE OF
OPTICAL FREE-SPACE ON INTER-SATELLITE
COMMUNICATION
EEE 506- Current Trends in Electronic and Electrical Engineering
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INTRODUCTION
The notion of satellite communication was proposed by Arthur C.Clarke in his article on Wireless World in 1945.
From inception gamut of technologies and operators have beenoperating to uphold satellite communication systems
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Category Year Activity Person/Agency/Country
Geostationary
concept1945
Suggestion of Geostationary satellite communication
feasibility
A. Clark ( U.K )
MoonReflection
1946Detection of Lunar Echo by Radar
J. Mofenson (U.S.A.)
1954Passive relaying of voice by moon reflection.
J.H. Trexler( U.S.A. )
1960Hawaii-Washington, D.C. Communication by
Moon Reflection.
Low altitude
orbit
1958 Observation of signals from Sputnik -1 Satellite.U.S.A. Navy.
1958Tape-recorded voice transmission by Satellite
SCORE.
U.S.S.R., Japan and others.
1960Meteorological facsimile Trans mission by
Satellite Tiros-1.U.S.A. Air Force.
1960Passive relaying of telephone and television by
Satellite Echo-1.U.S.A. NASA
1960Delayed relaying of recorded voice by Satellite
Courier-1B.U.S.A. Army.
1962Active transatlantic relaying of communication by
Satellite Telstar-1.U.S.A. Army.
1962 Communication between manned SatellitesVostok-3 and 4; Space television transmission.
U.S.A., U.K., France.
1963Scatter communication by tiny needles in Orbit.
( West Ford Project 6 )
U.S.A. MIT.
1963Active transpacific relaying of communication by
Satellite Relay 1.U.S.A. NASA, Japan.
Synchronous
Satellite
1963USA-Europe-Africa communication by Satellite
Syncom 2.U.S.A. NASA
1964Olympic Games television relaying by Satellite
Syncom 3
U.S.A., NASA Japan.
1965Commercial Communication (Semi-experimental)
by Satellite Early Bird.INTELSAT.
MAJOR MILESTONES OF SPACE RADIO COMMUNICATIONS
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INTRODUCTION
Motivation to use Satellites
Satellite missions.
Satellite System Elements
Space segment
Ground segment
Transponders
Bent-pipe
Onboard processing
Footprints
Orbits
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Satellite System Elements
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INTRODUCTION
Motivation to use Satellites
Satellite missions.
Satellite System Elements
Space segment
Ground segment
Transponders
Bent-pipe
Onboard processing
Footprints
Orbits
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Satellite Orbits
Geosynchronous Orbit (GEO):
36,000 km above Earth, includes
commercial and military
communications satellites,
satellites providing early warning of
ballistic missile launch.
Medium Earth Orbit (MEO): from
5000 to 15000 km, they include
navigation satellites (GPS, Galileo,
Glonass).
Low Earth Orbit (LEO): from 500 to
1000 km above Earth, includesmilitary intelligence satellites,
weather satellites.
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Advantages of Satellite Communication
Can reach over large geographical area
Easy to install new circuits
Circuit costs independent of distance
Broadcast possibilities Terrestrial network "by-pass"
Provision of service to remote or underdevelopedareas
User has control over own network 1-for-N multipoint standby possibilities
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OPTICAL FREE SPACE COMUNICATION IN SPACE
In space, radio frequencies (RFs) are usually used for long-distance
linkage. However, recent progress in optics and laser technologies,
especially in fiber optics, is ushering in an era of inter-orbit communications
using laser beams. Both RFs and optical waves are electromagnetic waves,
but optical waves offer many advantages in space.
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FEATURES OF OPTICAL FREE
SPACE COMMUNICATION LINK SMALLER SIZE
LESS WEIGHT AND POWER CONSUMPTION
HIGH DATA RATE
SECURED
NO REGULATORY RESTRICTION
LESS OVERALL EXPENSES IN ORDER TO ACHIEVETHE SAME MISSION
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LIMITATIONS OF OPTICAL
FREESPACE COMMUNICATION
VIBRATION
INTERNATIONAL INTEROPERABILITY
POINT AHEAD PROBLEM
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POINT AHEAD PROBLEM
RF, even EHF, spreadswhile propagating
Laser light doesnt
spread as much as RF
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FUTURE TREND
LASER COMMUNICATIONS RELAY DEMONSTRATIONMISSION (LCRD) as part of the launches anticipated in2015 and 2016 by NASA Goddard Space Flight Center inGreenbelt MD USA.
LCRD Mission will- Enable reliable, capable and cost effective optical
communication for near earth application and deep spacemissions
- Demonstrate high data rate optical technology
-Identify and develop requirement for future operational opticalcommunication systems
- Develop industrial base for future space optical communicationsystem