CME 574 Satellite Communications Fall, 2007 Dr Hazem Al-Otum Ref. Ellwood Brem, Instructor To orbit the Earth is to fall down and miss the ground!
Topics we will cover: History Satellite Mechanics Orbital Mechanics Launch Vehicles Space Segment Earth Segment Link Budget Multiple Accessing Satellite Services: VSAT, MSAT, GPS
It wasn t easy!
It wasn t easy! http://webphysics.ph.msstate.edu/javamirror/ntnujava/projectileorbit/projectileorbit.html
Historical Background 1945 Arthur C. Clarke publishes an essay about Extra Terrestrial Relays 1957 first satellite SPUTNIK 1960 first reflecting communication satellite ECHO 1963 first geostationary satellite SYNCOM 1982 first mobile satellite telephone system INMARSAT-A
Historical Background 1988 first satellite system for mobile phones and data communication INMARSAT-C 1993 first digital satellite telephone system 1998 global satellite systems for small mobile phones
Historical Background Passive Sats Moon: (1954-62) USA Navy TX the first message Earth-moon-earth. (1956)-Relay established between WD and Hawaii
Historical Background Passive Sats Echo: (1960) 100ft-diameter balloon
Historical Background Then Came: Sputnik 1, Explorer1 Launched October 14, 1957 from the Baikonur Cosmodrome in Kazakhstan 184 pounds Orbital period 90 minutes Broadcast beep beep 20 and 40 MHz Shocked the US into action Started space race
Historical Background Active Sats (1960) USA Courier First transponder-type Sat. (3W) (1963-64) USA Syncom-III attempt to place a GEO Sat. (1965) IntelSat 1 (Early Bird) 480 VB + 1 TV
Now: Boeing 702 DBS Satellite 134.5 feet long 2645 lbs payload 11,464 lbs takeoff weight Over 100 high-power transponders (94 active/24 spare) Up to 25 kw power Xenon-Ion Propulsion System
Satellite Regions Utilization: 24% - USA; 13%-UK; 6% France Region 1: Europe, Africa, Former Sov. Union & Mongolia Region II: North, South America and Greenland P Region III: Asia, Australia, South and West Pacific
Uses of Satellites (in somewhat chronological order) Intercontinental telephone, data, and video Photo Reconnaissance Scientific research Network TV distribution Private multipoint data networking (VSATs) Strategic military communications Signals intelligence Mobile satellite services (Inmarsat) Satellite radiolocation (GPS/Glonass) Direct broadcast satellite (DBS Primestar/Echostar) Handheld voice/data communications (Iridium/ICO/Globalstar) Internet backbone services
A Platform in Space! In 1945 Arthur C. Clarke wrote an article in Wireless World magazine outlining a system of geo-stationary broadcast satellites in orbit 22,000 miles above the equator. The proverbial Sky Hook!
Intercontinental telephone, data, and video relay Initially satellite links were only: One-way video and data traffic Backup to undersea telephone cables Because: Nominal 1-2 second time delay for a round-trip voice message.
Imagery Reconnaissance Military saw the value! Over-fly enemy Early scientific satellite programs were cover stories Discoverer scientific satellites carried cameras returned exposed film by a parachute Modern systems digitally encode imagery Radio transmission to earth. Newer systems include radar imaging Low Earth Orbit (LEO) - typically 200 miles
Scientific research First, scientific satellites Space environment near earth Unexpected discovery - Van Allen radiation belts in 1958 Later, scientific satellites took pictures of earth Based on military reconnaissance systems Weather forecasting GOES series of spacecraft now in orbit. Today, scientific satellites study The Earth The solar system Deep space Hubble Space Telescope, Chandra X-ray Telescope, ISS
Network TV distribution Early TV network video Terrestrial microwave networks C-band satellite systems Networks - greater control Cable TV big boost! TVRO - dishes in backyards Ku band Increased capacity Direct broadcast (DBS)
VSAT - Private Networks VSAT Very Small Aperture Terminal Replaces wireline data connections to businesses Convenience stores, malls, restaurants, gas stations Common uses Muzak background music Credit card transactions Corporate communications 64kbps to 2Mbps
Strategic Communications Strategic communications Previously relied on telephone and HF radio systems. Satellites High data rates Increased security Early satellites used UHF Today frequencies to EHF Example Milstar Communications system Satellite constellation
Signals Intelligence LEO and GEO systems deployed beginning in the 1960 s. Designed to intercept radio communications and radar signals. Antennas up to 100m in diameter are in orbit now. Receives signals from weak handheld cellular sets Other systems allow the tracking of ships and aircraft based on their transmissions.
Mobile Satellite Services Inmarsat - communications to ships at sea. Expanded Aircraft Trucks Rail locomotives. Suitcase sized terminals Used extensively in disaster situations and remote exploration. Not suitable for handheld equipment Antennas and terminals required Analog and digital services are used.
Satellite Radiolocation and Navigation Global Positioning System (GPS) Constellation of LEO satellites Timing from onboard clocks Earth receivers Use stored ephemeris data Who uses GPS? Trucks, ships, planes, hikers Almost everyone!
DBS - Direct Broadcast Satellite Digital video & audio to home users DishNetwork & DirecTV High quality pictures Competes with cable television Access by subscription Set top box 18 inch dish antenna Ka & Ku Satellites - Big Ones! New Satellite to automobile digital radio Sirius & XM Satellite Radio
Handheld telephone/data Iridium & Globalstar Many LEO satellites Iridium went bankrupt! High costs Cannot compete with cellular systems Globalstar - niche market $1 - $3 per call Iridium was reborn US DOD investment > $4 per call
In the Future? Internet backbone services Teledesic Internet in the sky 120 Mb uplink 720 Mb downlink. Ka band LEO constellation Inter-satellite links Scalable Viability in question Iridium debacle System scaled back From 240 satellites To only 30 satellites Nothing launched yet