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					Europe’s Quest for
Satellite Navigation: The
Structure of EGNOS and
Dominic De Mello
April 24, 2006
Europe and Satellite
   Search for a system started in 1995
   Developed the framework for EGNOS
   EGNOS went into operation in 2004
   EGNOS technology will be integrated
    into Galileo in 2006-2008.

   European Geostationary Navigation Overlay
   Precursor to Galileo
   Enhances GPS/GLONASS
   Has 3 segments:
   Space Segment
   Ground Segment
   User Segment
Space Segment

   3 Geostationary Earth Orbiting (GEO)
   Their range stretches over Europe, the
    Mediterranean Sea and Africa
   Connects to the Ground Segment
Ground Segment

   Consists of:
   4 Mission Control Centers which contain
    a Central Processing Facility (CPF)
   34 Ranging and Integrity Monitoring
    Stations (RIMS)
   6 Navigation Land Earth Stations
   Utilizes the EGNOS Network Time (ENT)
User Segment

   Consists of one of two receivers; one
    that uses GPS or one that uses
   EGNOS is also programmed into that
   EGNOS helps sharpen the receiver’s
    position from 20 meters of error to as
    little as 5 meters of error.
EGNOS in Galileo

   EGNOS will be used when Galileo is
    operational in order to decrease
   The systems will use independent
    technology to ensure that both
    systems will not fail at the same time
    if an error occurs.
   This will ensure that Europe will
    always have some form of functioning
    satellite navigation.
Europe and Satellite
   Search for their own system
    commenced in 1998.
   By 1999, planning was under way, and
    the name Galileo was chosen for the
   Was supposed to be fully operational
    by the end of 2008; looks like 2010 is
    more realistic
Why was it developed?

   As opposed to GPS, which was
    developed primarily for military uses,
    Galileo was developed exclusively for
    civilian use.
   There are zero militarily uses for
    Galileo as of right now, and no plans
    for military use in the future.

   Joint venture of European Space
    Agency (ESA) and European Union
   Estimated cost of 3.2 billion euros
   1.1 billion euros for the development.
   2.1 billion euros for the deployment.
   2 phases: EGNOS and Galileo
Galileo Technology

   2 aspects of Galileo:
   Space Segment
   Ground Segment
Space Segment

   Contains a total of 30 satellites; 27 are
   3 spare satellites
   Satellites are in 3 different planes,
    equally spaced around the plane.
   Altitude = 23, 600 km
   Satellites are in Medium Earth Orbit
Space Segment

   Each satellite has a period of 14 hours
    and 22 minutes
   Each satellite can last for 20 years,
    although they may be replaced every
    12 years
   At any point on earth, at least 6
    satellites will be in view.
Ground Segment

   2 Control Stations
   Satellite control – monitors if the
    satellite orbits are on path
   Mission control - maintains the
    synchronization of satellite clocks
Galileo’s Services

   Galileo’s transmitted signals are used
    to provide 5 distinct services:
   Open Service (OS)
   Safety of Life Service (SOLS)
   Commercial Service (CS)
   Public Regulated Service (PRS)
   Search and Rescue Support Service
Open Service
   OS can determine speed, velocity, and
    timing information
   Is free of charge and can be used on a
    handheld receiver
   Can also be used in car navigation systems
   Will never be intentionally jammed,
   Will have few ionospheric and tropospheric
   Accurate to 15 meters
Safety of Life Service

   Utilized mainly for marine, rail or
    aeronautical purposes
   Guarantees a level of accuracy and
    authenticity that OC does not.
   Offered openly, just like OS.
   Accurate to 4-6 meters
Commercial Service

   Is encoded
   Must pay fee in order to get
    encryption key
   Is much more precise than Open
   Is accurate to 1 meter
   Generates revenue for Galileo
Public Regulated Service
   The PRS is used for governmental purposes
   PRS is encoded; can be utilized by intelligence
    services, law enforcement, etc...
   Is guaranteed to always have a continuous
    signal; this is its main strength over OS.
   By utilizing “appropriate interference mitigation
    technologies”, the PRS is more accurate than OS.
   However, it is only accurate to about 10 meters
Search and Rescue
Support Service
   Detects emergency beacons
   Pinpoints the location of incoming
    distress signals
   Allows rescuers to know exactly where
    a victim is.
   10 minute period between distress
    signal and Galileo response.
Galileo Frequencies

   Each satellite transmits 6 navigational
    signals over 4 carrier frequencies
   The Carriers are:
   E5a (1176.450 Mhz)
   E5b (1207.140 Mhz)
   E6 (1278.75 Mhz)
   E2-L1-E1 (1575.42 Mhz) (same
    frequency as GPS L1)
Navigation Signals

   L1F Signal- OS; unencrypted
   L1P Signal- PRS; encrypted
   E6C Signal- Commercial Service;
   E6P Signal- PRS; encrypted
   E5a- OS; unencrypted
   E5b- OS; unencrypted
Navigation Data

   Ephemeris data
   Time parameters
   Almanacs

   Using this data, positioning for any user
    on earth can be derived.
Ephemeris Data

   Indicates the position of the satellite
    which is nearest the user.
   Provides 17 different parameters from
    each satellite
               Ephemeris Data or%203GPP.pdf
     Time Parameters
   By accurately measuring the time between
    transmission and reception, the location of a
    receiver can be determined.
   Galileo Standard Time (GST) is the time that
    Galileo uses.
   Each satellite broadcasts a Time of
    Transmission (TOT)
   Satellite Time Corrections are employed.
        Time Parameters
   Time Correction Formula:
   “TOT(X)c=TOT(X)m-(ΔtSV) X
   ♦ TOT(X)C is the corrected satellite signal X TOT
    in GST time
   ♦ TOT(X)m is the physical satellite signal X TOT,
    which is retrieved through pseudo-range
   ♦ (ΔtSV) X is the Satellite Time Correction for a
    specific signal X computed by the user using the
Galileo Standard Time

   Encrypted in Weeks and Time of Week
   4096 weeks (78 years)
   The Weeks integer will be set back to
    zero after 4096 weeks elapse
   Time of Week is encrypted in seconds
   604,800 seconds in a week.
   The seconds integer is set back to zero
    after a week elapses.
   Used to identify the position of all of the
    satellites that are in orbit.
   Will identify:
   Mean of Semi-Major Access
   Eccentricity
   Inclination
   Right Ascension of the Ascending Node
   Argument of Perigree
   Mean Anomaly
Satellite Signals
   Consist of a ranging code and data
   Ranging code – “sequence of +1 and -1
    with specific characteristics in the time
    (code length) and frequency (chip rate)”
   Each satellite transmits a ranging code, but
    part of that sequence will always be unique
    to one satellite, so a receiver can identify
    from which satellite the data came from.

   The signals are either encoded for OS,
    CS, or PRS.
   Based on what service you have, your
    receiver will decode the signal, and
    you will receive your coordinates.

   EGNOS and Galileo will ensure that
    there Europe will always have a
    functioning form of Satellite
   Europe will not be reliant on other
    countries since Galileo’s signal will
    never be interrupted
Works Cited

   Lindstrom, Gustav. “The Galileo
    Satellite System and its Security
    Implications”. European Union
    Institute for Security Studies: 2003
Works Cited
Prasad, Ramjee. “Applied Satellite
  Navigation Using GPS, Galileo, and
  Augmentation Systems”. Artech House,
“Program Galileo”. Galileo Joint Undertaking.