ICAO CAR/SAM ATN/GNSS SEMINARPresentation GNSS 4.2 by H. Cabler

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Modernization HistoryNeed for GPS Modernization recognized by US as GPS entered Full Operational Capability (1995)Recognized growing importance of GPS to both sectorsNational Policy imperative to enhance GPS as single world standardBetter, more reliable civilian service Need to rethink GPS architecture for the futureMultiple studies indicated diverse set of needsNew signals, Higher Power, Greater AccuracyGreater focus on dual-use natureSystem Integrity, Survivability, and Prevention of hostile useBetter Spectrum Management

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Background1996 Presidential Decision Directive (PDD) and 1998/99 Vice Presidential announcements committed US to modernization and improvement pathSelective Availability (SA) turned to zero NLT 2006Two new civil signals and new military signalsFree world-wide useMove from studies to action initiated in FY 2000SA Set to zero in May 00directed changes to existing and future satellitesIIF program terminated at 12 satellites and GPS III development beganModernization Now in Full Swing

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GPS Modernization at a GlanceGPS IIA/IIRGPS IIIGPS IIR-M, IIFIIR-M: Improved on all IIA capabilities and added2nd Civil Signal on L2New L1 & L2 M-CodeIIF: IIR-M capability and:Add 3rd Civil Signal on L5Standard Service (~100 m)Precise Service (~16 m)Two Nav frequencies L1: Civil (C/A) & Precise code, Navigation L-2: P-code NavGPS-III:Increased power (+20dB)Increased AccuracyGreater AvailabilityControlled IntegrityGreater Survivability

Basic GPSL2C on L2Full Civil RqmtsAddl CapabilitiesNew Civil Signal L5Increasing System CapabilitiesIncreasing Civil/Defense BenefitSA Setto 0

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New Civil SignalsMany consider setting SA = 0 as the 1st step in modernizationNew Signals can be considered the 2nd/3rd StepsCivil Users Currently Limited to One GPS SignalC/A-code at L1 frequency (1575.42 MHz)Adding a Second Civil SignalC/A-type code at L2 frequency (1227.60 MHz)Adding a Third Civil SignalP-type codes at L5 frequency (1176.45 MHz)Higher power signal, intended for precision navigation

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SA Set to Zero on 2 May 2000Selective Availability (SA) = Intentional DegradationPresident decided to discontinue SA to aid peaceful civil usersCivil user accuracy dramatically increased on 2 May 2000

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Block IIR ModernizationPre-Modernization/IIR

Heritage SignalsL1 C/AL1, L2 P(Y)

On Orbit Life~10.6 Years MMD*Post Modernization/IIR-M

Modernized SignalsFlexible, Higher PowerL1 C/A, L2C** (or C/A)L1, L2 P(Y)L1, L2 M-Code)On-Orbit Life~8.6 Years MMD * Design Life/MMD analysis completed Nov 01.** L2 Second Civil signal design supports varying code length and data structure

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Block IIF ModernizationPre-Modernization

Heritage SignalsL1, L2 C/AL1, L2 P(Y)

Design Life15 Years

* L2 Second Civil signal design supports varying code length and data structure** L5 Third Civil signal at -154dBwPost Modernization

Modernized SignalsFlexible, Higher PowerL1 C/A, L2C*L1, L2 P(Y)L1, L2 M-CodeL5 Third Civil** Design Life12 Years10 Year MMD

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Second Civil Signal (L2C) - Block IIR-M SatellitesFirst launch in 2003, then every satellite thereafterProvides a redundant signal for civil users Improved continuity in case L1 signal reception is lostImproved accuracy via dual-frequency ionosphere correctionWide-lane for extremely-precise local area differential GPSThird Civil Signal (L5) - Block IIF SatellitesFirst launch in 2005, then subsequent satellites thereafterProvides redundant dual-frequency capability for civil users Improved continuity in case L1 or L2 signal reception is lostImproved accuracy via triple-frequency ionosphere correctionTri-lane for ultra-precise local area differential GPS New Civil Signal Roll-Out

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SAASMM-CodeSystemMilestonesSpace Segment18010203040506070809101112131415161719FYModernized (IIR-M/IIF) LaunchesHeritage LaunchesGPS-IIIFOCGPS-IIIIOCGPS III Launches1st IIR-M1st IIFGPS III LaunchesL5IOCL5FOCEMD1st GPS-III SV1stL5 SV1stL2C SV1st GPS IIINew Capability ScheduleL2CIOCL2CFOC

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GPS III System VisionSecond Civil SignalThird Civil SignalThe GPS IIISystemRelook at Entire GPS Architecture to:Achieve long term GPS performance goalsReduce long term total ownership costsEnsure GPS III is Synergized with:Military and Civil Needs/SystemsPossible augmentation opportunitiesBuild Best GPS for the Next 30 Years

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GPS III Addresses MultipleGPS Needs Significantly Increased IntegrityCrucial for anticipated civil aviation usesAlso important for military useHigh level of Signal AvailabilityEqually important to both military and civilianSignificantly Increased AccuracyDriven by evolving nature of warfare and civil usesAdditional GPS needs: Future flexibility, nav related messaging, reprogramabilityThese Needs not able to be addressed without significant architectural change

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GPS III Integrated ApproachGPS Originally Designed without benefit of an Established User BaseCivil Users Previously Solicited for Suggested Changes to Existing System to Meet their NeedsGPS III has Novel Approach for Integrating Needs of the DoD, DOT, FAAJust completed System Architecture and Requirements Definition phase gathered and identified future requirementsInteragency Forum for Operation Requirements created to identify and assemble new requirements for GPSCivil and military requirements to be approved in totality by joint committeeCoast Guard Navigation Center soliciting requirements via website

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Stressing Civil MissionsOther Civil Missions (over 140 total) Other Civil Missions

Category IIIB/C instrument landing at approved airportPrecision automatic highway vehicle guidance (including collision avoidance), including in urban canyon conditionsMobile personal systems wireless communications synchronization for advanced performance signaling protocolsComputing/communications network synchronizationElectric power grid synchronizationPrecision construction equipment guidanceConstruction surveyingCrustal motion monitoringWeather monitoring (tropospheric water content)Scientific instrument synchronizationOpen loop antenna pointing for mobile satcomm users, other instrument pointingHiker navigationCivilian spacecraft position and attitude determination for sensor pointingStressing Civil Missions...

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GPS III Increased CapabilityAssured Delivery of GPS Signals Higher Power Military & Civil SignalsHigher Accuracy Service for All UsersIncreased Integrity Inherent in GPS

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GPS III Assured DeliveryDual-Use GPS is more than just Adding Civil SignalsAssuring availability and continuity of signalsRealization that GPS is considered a Critical Part of Worldwide InfrastructureAvailability/Continuity Key Factors in GPS III DesignCrosslink architectureNumber of orbital planesNumber of satellitesSparing strategyReplacement strategy Control segment

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GPS III Increased AccuracyAugmented and standalone missions identified that require more accuracy than modernized GPSSignal-in-space improvements must keep pace with those in users equipmentAdvanced technology clocksInter-satellite rangingImproved ephemeris and orbital modelsAge of Data reduction and more timely updates via crosslinks

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GPS Accuracy

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GPS III Increased IntegrityAviation applications one of key driversGPS III architectural changesImproved monitoring and reportingPlanned interfaces between GPS and augmentationsPotential for meeting broad array of civil and military needs via GPS alone

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Sufficient Means of Navigation?Sufficient to be used anywhere, anytimeWithout precluding use of other systems or augmentationsWithout requiring use of other systems or augmentationsExcept for most demanding applications (LAAS)With assured deliveryAvailability and continuity (and higher power)With high accuracyWith high integrity

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Ground AugmentationBy itself, GPS III will have very good Accuracy and IntegrityGood enough for most navigation applicationsGround Augmentation Gives Major ImprovementsFor Ultra High Accuracy~1 m with Local Area Differential GPS (LADGPS)~1 cm with Real-Time Kinematic (RTK)For Ultra High Integrity1-1x10-9/operation or even better is achievablePrecision Landing Needs High Accuracy/IntegrityPrime example of GPS ground augmentation system usageCivil: Local Area Augmentation System (LAAS)

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ChallengesMaintaining a healthy constellation while adding system capabilitiesConstellation sustainment strategiesOperational Control Segment (OCS) upgradesTesting / validating new signals - design and operationsTransition to modernized OCSSpectrum ProtectionInternational Cooperation

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International CooperationNeed a strategic view for US interaction with GalileoWork the policy and technical issues on how these two system can coexist and leverage one anotherOpportunity is now for us to begin working to ensure a single, integrated Navigation service Improves civil aviation, interoperability, and spectrum protectionWill save money if done properlyGPS III Acquisition effort is the right place to push for this to happen

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SummaryGPS Modernization activities well underwayGPS Modernization offers superb opportunity to satisfy both military requirements and civil needsGPS III exploring complementary DoD/civil augmentation opportunitiesWorking through challengesGPS III Architecture Working hard toward a robust, supportable, flexible, international capability for the next 30 years

GMSP concept is afforded by GPS-III modernization. As a GPS-III augmentation alternative, GMSP may provide a more efficient way to satisfy multiple space needs.

This chart depicts how Signal in Space pseudorange accuracy has evolved during the past six years and projected accuracy with AII and GPS III.AII = Accuracy Improvement Initiative. Includes Control segment improvements and integration of NIMA ground stations.This is really PPS accuracy. Today, the accuracy is 6 m in the SPS Performance Standard.