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Europe’s Quest for Satellite Navigation: The Structure of EGNOS and Galileo

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

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Europe’s Quest for Satellite Navigation: The Structure of EGNOS and Galileo

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  1. Europe’s Quest for Satellite Navigation: The Structure of EGNOS and Galileo Dominic De Mello April 24, 2006

  2. Europe and Satellite Navigation • 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.

  3. EGNOS • European Geostationary Navigation Overlay Service • Precursor to Galileo • Enhances GPS/GLONASS • Has 3 segments: • Space Segment • Ground Segment • User Segment

  4. Space Segment • 3 Geostationary Earth Orbiting (GEO) satellites. • Their range stretches over Europe, the Mediterranean Sea and Africa • Connects to the Ground Segment

  5. 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)

  6. User Segment • Consists of one of two receivers; one that uses GPS or one that uses GLONASS. • EGNOS is also programmed into that receiver. • EGNOS helps sharpen the receiver’s position from 20 meters of error to as little as 5 meters of error.

  7. EGNOS in Galileo • EGNOS will be used when Galileo is operational in order to decrease errors. • 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.

  8. Europe and Satellite Navigation • Search for their own system commenced in 1998. • By 1999, planning was under way, and the name Galileo was chosen for the system. • Was supposed to be fully operational by the end of 2008; looks like 2010 is more realistic

  9. 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.

  10. Galileo • Joint venture of European Space Agency (ESA) and European Union (EU) • 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

  11. Galileo Technology • 2 aspects of Galileo: • Space Segment • Ground Segment

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

  13. 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.

  14. http://images.google.com/imgres?imgurl=http://www.spaceflightnow.com/news/n0511/11giove/galileo.jpg&imgrefurl=http://www.spaceflightnow.com/news/n0512/28giovea/&h=370&w=398&szhttp://images.google.com/imgres?imgurl=http://www.spaceflightnow.com/news/n0511/11giove/galileo.jpg&imgrefurl=http://www.spaceflightnow.com/news/n0512/28giovea/&h=370&w=398&sz =24&tbnid=gChzcv1m2ZLUrM:&tbnh=111&tbnw=120&hl=en&start=28&prev=/images%3Fq%3Dgalileo%2Bsatellite %26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26rls%3DGGLD,GGLD:2004-19,GGLD:en%26sa%3DN

  15. Ground Segment • 2 Control Stations • Satellite control – monitors if the satellite orbits are on path • Mission control - maintains the synchronization of satellite clocks

  16. 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 (SAR)

  17. 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 delays • Accurate to 15 meters

  18. 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

  19. Commercial Service • Is encoded • Must pay fee in order to get encryption key • Is much more precise than Open Service • Is accurate to 1 meter • Generates revenue for Galileo

  20. 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

  21. 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.

  22. 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)

  23. Navigation Signals • L1F Signal- OS; unencrypted • L1P Signal- PRS; encrypted • E6C Signal- Commercial Service; encrypted • E6P Signal- PRS; encrypted • E5a- OS; unencrypted • E5b- OS; unencrypted

  24. Navigation Data • Ephemeris data • Time parameters • Almanacs • Using this data, positioning for any user on earth can be derived.

  25. Ephemeris Data • Indicates the position of the satellite which is nearest the user. • Provides 17 different parameters from each satellite

  26. Ephemeris Data http://www.galileoju.com/doc/Galileo%20standardisation%20document%20for%203GPP.pdf

  27. 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.

  28. 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 measurements. • ♦ (ΔtSV) X is the Satellite Time Correction for a specific signal X computed by the user using the data” • http://www.galileoju.com/doc/Galileo%20standardisation%20document%20for%203GPP.pdf

  29. 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.

  30. Almanacs • 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

  31. 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. • http://site.ebrary.com/lib/princeton/Doc?id=10081977

  32. Encoding • 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.

  33. Conclusion • EGNOS and Galileo will ensure that there Europe will always have a functioning form of Satellite Navigation. • Europe will not be reliant on other countries since Galileo’s signal will never be interrupted

  34. Works Cited • Lindstrom, Gustav. “The Galileo Satellite System and its Security Implications”. European Union Institute for Security Studies: 2003 <http://www.iss-eu.org/occasion/occ44.pdf>

  35. Works Cited Prasad, Ramjee. “Applied Satellite Navigation Using GPS, Galileo, and Augmentation Systems”. Artech House, 2005 http://site.ebrary.com/lib/princeton/Doc?id=10081977 “Program Galileo”. Galileo Joint Undertaking. 2005. http://www.galileoju.com/doc/Galileo%20standardisation%20document%20for%203GPP.pdf

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