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The Ionosphere and Its Effects on GNSS Systems MITRE Presentations The Ionosphere and its Effects on GNSS Systems MITRE Presentations 14 to 16 April 2008 Santiago, Chile Dr. M. Bakry El-Arini Ing. Roland O. Lejeune Dr. S. Vincent Massimini © 2008 The MITRE Corporation. All rights reserved. Sobre MITRE – Nota Informativa MITRE, una de las organizaciones más grandes en ingeniería de sistemas de Estados Unidos, es una institución de investigación no comercial, sin fines de lucro, dedicada a servir al interés público. Localizada en Washington, D.C. y Bedford, Massachusetts, cuenta con una planta de más de 6500 profesionales, en su mayoría ingenieros. Su Centro para el Desarrollo de Sistemas Avanzados de Aviación es la organización de investigación y desarrollo de ingeniería de sistemas aeroportuarios y de control de tráfico aéreo más grande de Estados Unidos. Muchos de los procedimientos aeronáuticos de la aviación civil internacional y los algoritmos de componentes electrónicos a bordo de aeronaves a nivel internacional fueron desarrollados por MITRE durante su medio siglo de existencia. MITRE ha colaborado con cerca de 50 naciones. Los orígenes de MITRE se remontan a años previos a 1958, cuando MITRE formaba parte del sistema de laboratorios del Massachusetts Institute of Technology (MIT), luego de lo cual pasó a convertirse en un laboratorio independiente de interés nacional. 2 of 301 © 2008 The MITRE Corporation. All rights reserved. Contacto con MITRE Para información y contacto con MITRE, escribir al Dr. Bernardo Lisker, Director Internacional, Internet [email protected] o llamar al teléfono +1 703 983 6970 (Estados Unidos) (español o inglés) 3 of 301 © 2008 The MITRE Corporation. All rights reserved. Table of Contents 1 of 3 • Principal Acronyms and Abbreviations 7 • Overview of GNSS Navigation Sources, 12 Augmentation Systems, and Applications • Ionospheric Effects on GNSS 92 • Description of a Real-Time Algorithm for Detecting Ionospheric Depletions for SBAS and the Statistics of Depletions in South America During the Peak of the Current Solar Cycle 125 4 of 301 © 2008 The MITRE Corporation. All rights reserved. Table of Contents 2 of 3 • Tropospheric Effects on GNSS 145 • Ionospheric Corrections for GNSS 166 • Tropospheric Corrections Model for GNSS 179 Receivers • General Description of MITRE’s Service 194 Volume Models • Modeling Effects of Ionospheric Delay on 210 GNSS Availability 5 of 301 © 2008 The MITRE Corporation. All rights reserved. Table of Contents 3 of 3 • Modeling Scintillation Effects on L1/L5 SBAS 232 Availability in North and South America • Performance Estimates for Current and 266 Future GNSS Systems and Augmented GNSS Systems (SBAS/GBAS/GRAS) • Short and Long-Term Planning Considerations 291 • Recommendations for GNSS Data Collection, Planning, and Implementation 297 6 of 301 © 2008 The MITRE Corporation. All rights reserved. Principal Acronyms and Abbreviations 1 of 5 A&K Altshuler and Kalaghan Model A/A/C Accuracy, Availability and Continuity ABAS Aircraft-Based Augmentation System ADS-B Automatic Dependent Surveillance - Broadcast mode APV Approach with Vertical Guidance ATC Air Traffic Control B&E Black and Eisner Model C/A Coarse/Acquisition CAT Category CDU Control Display Unit CMC Code-Minus-Carrier DF Dual Frequency DME Distance Measuring Equipment DoD Department of Defense DOP Dilution of Precision EGNOS European Geostationary Navigation Overlay Service FAA Federal Aviation Administration FDE Fault Detection and Exclusion FMS Flight Management System 7 of 301 © 2008 The MITRE Corporation. All rights reserved. Principal Acronyms and Abbreviations 2 of 5 FTE Flight Technical Error GA General Aviation GAGAN Indian Geo Aided GPS Augmented Navigation GATOM GNSS Air Traffic Operations Model GBAS Ground-Based Augmentation System GDOP Geometric Dilution of Precision GISM Global Ionospheric Scintillation Model GIVE Grid Ionospheric Vertical Error GNSS Global Navigation Satellite Systems GPS Global Positioning System GPWS Ground Proximity Warning System GRAS Ground-Based Regional Augmentation System HAL Horizontal Alert Limit HPE Horizontal Position Error HPL Horizontal Protection Level ICAO International Civil Aviation Organization IFOR Interagency Forum on Operational Requirements IFR Instrument Flight Rules IGP Ionospheric Grid Points 8 of 301 © 2008 The MITRE Corporation. All rights reserved. Principal Acronyms and Abbreviations 3 of 5 ILS Instrument Landing System INS Inertial Navigation System IPP Ionospheric Pierce Point IRS Inertial Reference System ITU International Telecommunication Union LAAS Local Area Augmentation System LNAV Lateral Navigation LORAN Long Range Navigation LOS Line of Sight LPV Localizer Performance with Vertical Guidance MLS Microwave Landing System MOPS Minimum Operational Performance Standard MSAS MTSAT Satellite-based Augmentation System (Japan) MTSAT Multi-function Transport Satellite (Japan) NAS National Airspace System NAVAID Navigational Aid NDB Non-Directional Beacon NM Nautical Miles NPA Non-Precision Approach 9 of 301 © 2008 The MITRE Corporation. All rights reserved. Principal Acronyms and Abbreviations 4 of 5 NWRA North West Research Associates, PIM Parameterized Ionosphere Model PPS Precise Positioning Service PRN Pseudo Random RAIM Receiver Autonomous Integrity Monitoring RDM Range Domain Monitor RNAV Area Navigation RNP Required Navigation Performance S/A Selective Availability SAAAR Special Aircrew and Aircraft Authorization Required SARPS Standards and Recommended Practices SBAS Satellite-Based Augmentation System SCM Service Continuity Model SF Single Frequency SID Standard Instrument Departure SPS Standard Positioning Service SSN Sun Spot Number STAR Standard Terminal Arrival SV Satellite Vehicle 10 of 301 © 2008 The MITRE Corporation. All rights reserved. Principal Acronyms and Abbreviations 5 of 5 SWAT SBAS Worldwide Availability Tool TAWS Terrain Awareness Warning System TEC Total Electron Content TSO Technical Standard Order UDRE User Differential Range Error URA User Range Accuracy USAF United States Air Force VNAV Vertical Navigation VORTAC Very High Frequency Omnidirectional Range Collocated with Tactical Air Navigation Station VPE Vertical Position Error VPL Vertical Protection Level WAAS Wide Area Augmentation System WATUSI WAAS Analysis Testbed for Unavailability-of-Service Investigations WBMOD WideBand Model WRS WAAS Reference Station 11 of 301 © 2008 The MITRE Corporation. All rights reserved. Overview of GNSS Navigation Sources, Augmentation Systems, and Applications The Ionosphere and its Effects on GNSS Systems 14 to 16 April 2008 Santiago, Chile Dr. S. Vincent Massimini © 2008 The MITRE Corporation. All rights reserved. Global Navigation Satellite Systems (GNSS) • Global Positioning System (GPS) – U.S. Satellites • GLONASS (Russia) – Similar concept • Technically different • Future: GALILEO – “Euro-GPS” • Future: Beidou/Compass 13 of 301 © 2008 The MITRE Corporation. All rights reserved. GPS 14 of 301 © 2008 The MITRE Corporation. All rights reserved. Basic Global Positioning System (GPS) Space Segment User Segment Ground Segment 15 of 301 © 2008 The MITRE Corporation. All rights reserved. GPS Nominal System • 24 Satellites (SV) • 6 Orbital Planes • 4 Satellites per Plane • 55 Degree Inclinations • 10,898 Miles Height • 12 Hour Orbits • 16 Monitor Stations • 4 Uplink Stations 16 of 301 © 2008 The MITRE Corporation. All rights reserved. GPS Availability Standards and Achieved Performance “In support of the service availability standard, 24 operational satellites must be available on orbit with 0.95 probability (averaged over any day). At least 21 satellites in the 24 nominal plane/slot positions must be set healthy and transmitting a navigation signal with 0.98 probability (yearly averaged).” Historical GPS constellation performance has been significantly better than the standard. Source: “Global Positioning System Standard Positioning Service Performance 17 of 301 Standard” October 2001 © 2008 The MITRE Corporation. All rights reserved. GPS Constellation Status (30 March 2008) • 30 Healthy Satellites – 12 Block IIR satellites – 13 Block IIA satellites – 6 Block IIR-M satellites • 2 additional IIR-M satellites to launch • Since December 1993, U.S. has met/exceeded GPS service performance commitments • U.S. committed to improving GPS service 18 of 301 © 2008 The MITRE Corporation. All rights reserved.18 GPS Signals • L1 Carrier Signal (1575.42 MHz) – Coarse/Acquisition (C/A) Code – P (Y) Code (P code is encrypted to Y code) – Nav/system data (50 bps) • Almanacs (reduced-precision subset of the clock and ephemeris parameters) • Ephemeris Data (exact satellite and clock info) • L2 Carrier Signal (1227.60 MHz) – P (Y) Code – Public code (L2C) being added in future SVs for civil use • Five L2C SVs now in orbit • L5 (New frequency in future) (1176.45 MHz) 19 of 301 – Available for full use 2015 or so © 2008 The MITRE Corporation. All rights reserved. Current Positioning Systems • Standard Positioning Service (SPS) – Single frequency receiver (L1) – C/A code and navigation/system data • Precise Positioning Service (PPS) – Dual frequency receiver (L1 and L2) • Technical advantages to using two frequencies – C/A code, navigation/system data, and P(Y) code – Generally available to DOD and other approved users – Will not discuss further in this briefing 20 of 301 © 2008 The MITRE Corporation. All rights reserved. Range and Velocity Measurement (SPS) • Each satellite vehicle (SV) has a different 1023 bit pseudo random (PRN) code from which the user can determine the time of transmission – Repeats each millisecond
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