EE 497F Satellite Communications

1
EE 497F Satellite Communications

• Fall, 2003
• Ellwood Brem, Instructor
• To orbit the Earth is to fall down and miss the
  ground !

2
EE 497F Satellite Communications

• Ellwood Brem
• 224 E.E. East
• 865-0950
• eeb149_at_psu.edu
• Office Hours
• M, W 300 400 PM
• By appointment
• Web page http//ee.psu.edu/courses/ee497f/

3
EE 497F Satellite Communications

• Interactive discussion, web, multi-media course
• Emphasis on system-level understanding
• Industry based guest speakers
• Satellite software term project
• Earth station field trip
• Video presentations

4
EE 497F Satellite Communications

• Grading Policy

5
Topics we will cover

• Uses of Satellites
• History
• Orbital Mechanics
• Launch Vehicles
• Antennas
• Radio Propagation
• Transponders

• Power
• Propulsion/Stability
• Reliability
• Ground Terminals
• Military Systems
• Commercial Systems
• Scientific Systems

6
It wasnt easy!
7
It wasnt easy!
http//webphysics.ph.msstate.edu/javamirror/ntnuja
va/projectileOrbit/projectileOrbit.html
8
Especially when you are trying something
revolutionary

• We hope the professor from Clark College
  Robert. H. Goddard is only professing to be
  ignorant of elementary physics if he thinks that
  a rocket can work in vacuum.
• Editorial, New York Times, 1920

9
And Then Came Sputnik 1

• 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

10
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
• Built for direct broadcast and point to point
  services.

11
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

12
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 !

13
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.

14
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

15
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

16
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)

17
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

18
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

19
Signals Intelligence

• LEO and GEO systems deployed beginning in the
  1960s.
• 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.

20
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.

21
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!

22
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

23
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
• gt 4 per call

24
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