GEG 1220 Satellite Navigation History and GPS Constellations

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GEG 1220Satellite Navigation History and GPS
Constellations

• Dr. Walter Goedecke
• Fall 2007

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Topics

• Satellite Navigation History
• Radio Navigation
• LORAN
• Satellite Navigation
• TRANSIT
• NAVSTAR
• GPS Civilian Use
• NAVSTAR GPS Segments
• Description of the U.S. GPS system segments
• Space segment
• Ground segment
• Foreign Navigation Systems
• Russian GLONASS
• European Galileo
• Chinese Beidou

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Satellite Navigation History

• Radio Navigation
• Radio navigation originated in the 1920s
• First this was the simple determination of a
  radio beacons location
• In early WWII LORAN (LOng Range Navigation),
  developed by the MIT Radiation Laboratory, used
  time-of-flight radio signals to determine
  distance.
• This was limited to 2-dimensional coordinates on
  the surface latitude and longitude

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Satellite Navigation History

• Diagram of two LORAN transmitters A B, with
  hyperbolic curves representing positions of
  constant time-of-arrival differences.
• http//en.wikipedia.org/wiki/Loran

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Satellite Navigation History

• LORAN Principle
• Two shore stations, A B, emit radio pulses
  simultaneously.

• A ship will receive the signals with a time delay
  between the signals.
• The ship will be on one of the hyperbolic curves,
  also known as a TD (time difference) line, shown
  in the figure.
• Since the ships position is still ambiguous, it
  takes another pair of received signals to locate
  on another set of curves intersecting these, and
  thus the actual position is determined.

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Satellite Navigation History

• Guidance by Artificial Star
• The space race begins - Sputnik (??????? means
  satellite) was launched into space by Russia on
  October 4th, 1957
• Later, that same evening, researchers of the
  Massachusetts Institute of Technology (MIT)
  determined its orbit by noting its radio signal
  increased as it approached, and decreased as it
  left.
• Because a satellite's position could be tracked
  from the ground implied that a ground position
  could be determined using transmitted radio
  signals from a satellite.

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Satellite Navigation History

• Transit
• Also known as NAVSAT, for Navy Navigation
  Satellite System
• Developed by Johns Hopkins University
• First satellite launched in 1959
• Constellation of five satellites required, with
  five extra backups.
• Ranging, line-of-sight distance, or slant range
  depended on the Doppler effect

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Satellite Navigation History

• NAVSTAR GPS
• The Navstar Global Positioning System was first
  conceived in 1973 at the Pentagon.
• This Global Positioning System (GPS) would be
  designed, built, operated, and maintained by the
  U.S. Department of Defense.
• 24 satellites would be placed in 12-hour inclined
  orbits.

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Satellite Navigation History

• NAVSTAR GPS
• On July 14, 1974 the very first NAVSTAR satellite
  is launched.
• These first satellites were used for concept
  validation purposes, or phase one of the project.
• They carried the first atomic clocks ever
  launched into space.
• February 22, 1978, the first Block I satellite is
  launched.
• A total of 11 Block I satellites were launched
  between 1978 and 1985 on the Atlas-Centaur
  rocket.
• By the mid-1990s the system was fully operational
  with 24 satellites.

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Satellite Navigation History

• INS
• Aircraft relied primarily on inertial navigation
  systems (INS) before GPS.
• INS is comprised of linear and angular
  accelerometers and a means of solving
  differential equations to calculate position from
  moment to moment over a short period of time.
• Accumulated errors creep in from drift and noise
  sources.
• INS is augmented with occasional positional fixes
  by radio beacons.

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Satellite Navigation History

• Civilian Use
• A catastrophic, and political example of
  navigational failure was the downing of Korean
  Airlines Flight 007 in 1983 after it strayed over
  territory belonging to the Soviet Union.
• While the Soviet Union couldnt justify the
  reason for shooting the civilian plane down, this
  event set a president for allowing civilian use
  of military technology for navigation.

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Satellite Navigation History

• INS GPS
• Together, both INS with GPS provide a virtual
  infallible navigation system that can operate in
  real-time even for speedy aircraft.
• The goal is to provide exact placement of the
  inertial platform, i.e., the aircraft,
  spacecraft, nautical ship, etc, relative to the
  Earth, over a reasonable time period to allow the
  completion of navigation.
• The NAVSTAR Global Positioning System is to be
  always available to any travelling body with an
  appropriate receiver, thus allowing triangulation
  to within several tens of meters.

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Satellite Navigation History

• National Security
• GPS was created for national defense.
• Now the inclusion of the civilian interests has
  greatly augmented the uses of GPS.
• Additionally the scale of manufacture has
  increased while the cost of building GPS
  receiving systems has significantly decreased.
• Nevertheless, the condition of the US GPS fleet
  has been one the most important space-based
  systems to the military, possibly a greater
  concern now than intercontinental missile
  launches.

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Satellite Navigation History

• National Security
• The military is still the largest buyer of GPS
  receivers, since the goal is to network the
  entire military with GPS sensing capabilities.
• The U.S. military have become very dependant on
  GPS for certain operations in under a decade.
• This reliance may become a total dependence on
  GPS within the next few years.

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Satellite Navigation History

• Civil Uses
• Increasing civilian uses of GPS along with
  military requirements have lead to a balancing
  act of priorities
• However, the US government does foster commercial
  uses for its technology
• While GPS is not fully functional, surveying
  becomes the first substantial commercial market.

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Satellite Navigation History

• Early Civil Uses
• Conventional meets-and-bounds surveying is very
  equipment intensive and requires much effort to
  tie land areas to be surveyed to already
  established datum points.
• The early period cost savings using GPS was still
  better than using conventional surveying
  techniques.
• Also, most surveying does not require fast
  real-time measurements, therefore allowing
  sufficient time for proper satellite coverage
• Also, time averaging of measurements could be
  applied for greater accuracy

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Satellite Navigation History

• Early Civil Uses
• Even though there were a limited number of
  satellites then, surveyors turned to a number of
  GPS accuracy enhancement techniques including
  differential GPS and carrier phase tracking.
• Obviously, private research and development from
  early GPS commercial uses such as surveying
  spurred advances that the DoD could integrate
  into future advances.
• Now, most national geodetic data is based upon
  GPS aided surveys

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The NAVSTAR GPS Segments GPS Description

• The Global Positioning System is divided into
  three segments space, control, and user.
• The space segment comprises the GPS satellite
  constellation.
• The control segment comprises ground stations
  around the world that are responsible for
  monitoring the flight paths of the GPS
  satellites, synchronizing the satellites' onboard
  atomic clocks, and uploading data for
  transmission by the satellites.
• The user segment consists of GPS receivers used
  for both military and civilian applications.

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The NAVSTAR GPS Segments GPS Description

• The system cost is about 400 million / year.
• There are two levels of service
• Precise Positioning Service (PPS) for exclusive
  military use
• Accuracy within 95 probability is 16 meters for
  horizontal component and 23 m for the vertical
• Standard Positioning Service (SPS) for public use
• Accuracy 100 meters for horizontal component and
  156 m for the vertical

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GPS Space SegmentGPS Orbital Details

• The system consists of 24 satellites in medium
  Earth orbit (MEO)
• This insures a ground station has access to at
  least four satellites at any given time, but as
  much as ten are possible.
• Period is half a sidereal day, 11 hours and 58
  minutes
• 20,200 km nominal altitude in circular orbit
• 550 inclination from equatorial plane
• 6 orbital planes of 550 inclination with a
  constellation of 4 satellites in each plane
  spaced 600 in orbital longitude

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GPS Space SegmentGPS Orbits

• After Dana

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GPS Ground Segment

• Spacecraft operated from the GPS master control
  station (MCS) by the US Air Force at Schriever
  Air Force Base (formerly Falcon AFB) near
  Colorado Springs, Colorado, and four other
  monitor stations, located in
• Hawaii
• Ascension Island in the Atlantic Ocean
• Diego Garcia in the Indian Ocean
• Kwajalein in the Pacific Ocean
• - Includes antenna for uploading to satellite

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GPS Ground Segment GPS Control Sites

• El-Rabbany

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Other Navigation Systems Russian GLONASS

• The Russian Global Navigation Satellite System
  (GLONASS) is managed for the Russian Federation
  Government by the Russian Space Forces
• GLONASS is very similar to the NAVSTAR GPS
• This is an all weather global navigation system
• There are 21 operational satellites with 3 spares
• The satellite mass is about 1,300 kg
• The size is 2.35 m diameter

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Russian GLONASS

• GLONASS Satellite, Russian Federation Ministry of
  Defense

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Russian GLONASSIntegration of GLONASS with GPS

• Integration of GLONASS may be possible with GPS
• Several applications use both now
• This would allow extra coverage during poor
  visibility
• However, there are problems
• Two different coordinate frames used
• GPS uses WGS 84 system
• GLONASS uses Earth Parameter System 1990 (PZ-90)
• Because of different reference times, this
  difference drifts
• This problem could be solved by considering the
  time error as an additional variable for solution

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Other Navigation Systems European Galileo

• The European Global Satellite Navigation System
  (GNSS), or Galileo, will be a European civil
  controlled satellite system
• Europes reason for development is for a
  navigation system not dependant on the U.S.
  NAVSTAR system.
• The venture is a joint public and private
  partnership
• There will be two types of service
• A free, basic service
• A premium chargeable service with additional
  features

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European GalileoDevelopment

• The Galileo development plan has three phases
• The definition phase that ended in 2000
• The development and validation phase, that began
  in 2001, to include
• Ground control infrastructure
• Prototype satellites
• Communication allocation
• Constellation deployment to begin in 2006

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European GalileoDevelopment

• Galileo should be available by 2008, with
  additional ground control and satellite
  improvements
• The European Geostationary Navigation Overlay
  System (EGNOS) will augment the system

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Other Navigation Systems Chiness Regional
Satellite Navigation System (Beidou)

• China has launched two navigation satellites
• These geostationary orbits are at 36,000 km
  altitude
• These are intended for land and marine
  transportation
• The second generation system is being planned

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• References
• Ahmed El-Rabbany, Introductions to GPS The
  Global Positioning System, Publisher Artech
  House.
• Dana, Peter H., Department of Geography,
  University of Texas at Austin, 1994http//www.col
  orado.edu/geography/gcraft/notes/gps/gps_f.html
• Pratt, Timothy, Bostian, Charles, Allnutt,
  Jeremy, Satellite Communications, 2003, John
  Wiley Sons.
• Scott Pace, Gerald P. Frost, Irving Lachow, Dave
  Frelinger, Donna Fossum, Don Wassem, Monica M.
  Pinto, The Global Positioning System Assessing
  National Policies, Rand Corporation Study

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References Cont.

• Russian Federation Ministry of Defense,
  Coordinational Scientific Information Center,
  http//www.glonass-center.ru/frame_e.html
• Wertz, James R., Wiley J. Larson, Space Mission
  Analysis and Design, Publisher Microcosm Press.
• Wikipedia, http//en.wikipedia.org/wiki/LoranHist
  ory