lecture23 - ECE2984 Lecture23: APPLICATIONS...

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ECE 2984 Lecture 23: APPLICATIONS – SATELLITE COMMUNICATIONS Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications
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Last Lecture LAST LECTURE: Satellite Based Navigation: Basic Principles Applications THIS LECTURE: Satellite Based Communications: istory History Basic Principles Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications Modern Constellations
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Satellite Based Communications Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications
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Satellite Communication The basic function of a communication satellite is to act as a message forwarding system. A ground station transmits a message gnal e tellite “uplink”) signal to the satellite ( uplink ). The satellite receives the message, amp l if iesit ,andthenretransm itsitto nother round ation “downlink”) another ground station ( downlink ). Different frequencies are used for the uplink and downlink to avoid problems with signal interference. T h ed e v i c et h a tc o n v e r t st h e frequency of the message between receive and transmit is called a d Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications “transponder”.
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Communications Satellite e asic nctions f The basic functions of a communications satellite are: COLLECT microwave signals t h from a given zone on Earth. AMPLIFY the received signal. CONVERT the carrier signal of the received message from the uplink to downlink frequency. ANSMIT e ownlink gnal TRANSMIT the downlink signal to another zone on Earth. Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications
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SCORE Satellite (1958) The Signal Communications Orbit Relay Equipment (SCORE) spacecraft launched on December 18 th 1958 was the first “active communication satellite”. The spacecraft had two receive antennas, two transmit antennas, and two tape recorders for storing messages and data. The first transmitted message from space was the following by Dwight Eisenhower : "This is the President of the United States speaking. Through the marvels of scientific advance, y oice ming u ia tellite my voice is coming to you via a satellite circling in outer space. My message is a simple one: Through this unique means I nvey ou nd ll ankind, merica's Joseph Baker (ECE Dept) ECE 2984: Exploration of Space Lecture 23: Communications convey to you and all mankind, America s wish for peace on Earth and goodwill toward men everywhere."
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Echo 1 Satellite (1960) e CHO acecraft unched n 3 The ECHO 1 spacecraft launched on 13 th May 1960 was the first “passive communications spacecraft”. HO as 00 ot iameter alloon ECHO 1 was a 100 foot diameter balloon made of reflective “mylar” material from which signals originating from the ound uld e ounced ground could be bounced.
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This note was uploaded on 09/19/2011 for the course ENGE 1114 taught by Professor Twknott during the Fall '06 term at Virginia Tech.

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lecture23 - ECE2984 Lecture23: APPLICATIONS...

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