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
Has 3 segments:
3 Geostationary Earth Orbiting (GEO)
Their range stretches over Europe, the
Mediterranean Sea and Africa
Connects to the Ground Segment
4 Mission Control Centers which contain
a Central Processing Facility (CPF)
34 Ranging and Integrity Monitoring
6 Navigation Land Earth Stations
Utilizes the EGNOS Network Time (ENT)
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
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
Why was it developed?
As opposed to GPS, which was
developed primarily for military uses,
Galileo was developed exclusively for
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
2 aspects of Galileo:
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
Each satellite has a period of 14 hours
and 22 minutes
Each satellite can last for 20 years,
although they may be replaced every
At any point on earth, at least 6
satellites will be in view.
2 Control Stations
Satellite control – monitors if the
satellite orbits are on path
Mission control - maintains the
synchronization of satellite clocks
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
OS can determine speed, velocity, and
Is free of charge and can be used on a
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
Guarantees a level of accuracy and
authenticity that OC does not.
Offered openly, just like OS.
Accurate to 4-6 meters
Must pay fee in order to get
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
Detects emergency beacons
Pinpoints the location of incoming
Allows rescuers to know exactly where
a victim is.
10 minute period between distress
signal and Galileo response.
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)
L1F Signal- OS; unencrypted
L1P Signal- PRS; encrypted
E6C Signal- Commercial Service;
E6P Signal- PRS; encrypted
E5a- OS; unencrypted
E5b- OS; unencrypted
Using this data, positioning for any user
on earth can be derived.
Indicates the position of the satellite
which is nearest the user.
Provides 17 different parameters from
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
Each satellite broadcasts a Time of
Satellite Time Corrections are employed.
Time Correction Formula:
♦ 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.
Mean of Semi-Major Access
Right Ascension of the Ascending Node
Argument of Perigree
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
Lindstrom, Gustav. “The Galileo
Satellite System and its Security
Implications”. European Union
Institute for Security Studies: 2003
Prasad, Ramjee. “Applied Satellite
Navigation Using GPS, Galileo, and
Augmentation Systems”. Artech House,
“Program Galileo”. Galileo Joint Undertaking.