An Overview of An Overview of Civil GPS MonitoringCivil GPS Monitoring

John W. LavrakasJohn W. Lavrakas

ION Western Regional Vice PresidentION Western Regional Vice President

Presented to the So. California Section Presented to the So. California Section IONION

March 31, 2005March 31, 2005

Aerospace Corp. El Segundo, CAAerospace Corp. El Segundo, CAThe opinions expressed in this briefing are those of the author and do not

represent the views of the U.S. Government, the ION, or Overlook Systems

OverviewOverview

Background on civil GPS Background on civil GPS monitoringmonitoring

What has been going on recentlyWhat has been going on recently The new White House policy The new White House policy

directivedirective Implementation approachesImplementation approaches Future plansFuture plans

BackgroundBackground

GPS has extensive monitoring of GPS has extensive monitoring of the signal and the servicethe signal and the service– Worldwide network of monitor Worldwide network of monitor

stationsstations– 24-hour crews24-hour crews– Automated and manual checks of Automated and manual checks of

datadata Is it adequate? Not reallyIs it adequate? Not really

What’s missing?What’s missing?

Signal monitoringSignal monitoring C/A code not continuously monitoredC/A code not continuously monitored Not 100% coverage of signalsNot 100% coverage of signals Existing receivers can’t track large clock runoffsExisting receivers can’t track large clock runoffs

Navigation message monitoringNavigation message monitoring Nav message send/receive checked but not Nav message send/receive checked but not

contentcontent

Service monitoringService monitoring Only range errors, signal availability checkedOnly range errors, signal availability checked No formal checks of position and time accuracy, No formal checks of position and time accuracy,

service availabilityservice availability

What has gone wrong?What has gone wrong?

Single Frequency Iono CoefficientsSingle Frequency Iono Coefficients– 28 May - 02 Jun 2002, single frequency 28 May - 02 Jun 2002, single frequency

iono coefficients incorrectiono coefficients incorrect Partition reconciliation anomalyPartition reconciliation anomaly

– 12 Mar - 22 Mar 1993, time transfer 12 Mar - 22 Mar 1993, time transfer error, 15 ns over six dayserror, 15 ns over six days

SVN19/PRN19 “evil waveform”SVN19/PRN19 “evil waveform”– 1993 - 2-8 meter vertical position errors 1993 - 2-8 meter vertical position errors

What has gone wrong?What has gone wrong?

Invalid almanacInvalid almanac– 28 Mar 2000 GPS almanac contained 28 Mar 2000 GPS almanac contained

incorrect informationincorrect information When used in GPS modeling tools, When used in GPS modeling tools,

resulted in generation of incorrect PDOP resulted in generation of incorrect PDOP and SEP valuesand SEP values

What has gone wrong?What has gone wrong?

Clock failureClock failure– 28 Jul 2001 SVN22 clock failure28 Jul 2001 SVN22 clock failure

Range errors in excess of 200,000 metersRange errors in excess of 200,000 meters Occurred over southern Pacific OceanOccurred over southern Pacific Ocean

– For about a half an hour not in view of any OCS For about a half an hour not in view of any OCS monitor stationsmonitor stations

Clock failureClock failure– 1 Jan 2004 SVN23 clock failure1 Jan 2004 SVN23 clock failure

Transmission of ranging errors up to 280,000 Transmission of ranging errors up to 280,000 meters with duration of 2.75 hoursmeters with duration of 2.75 hours

How can this happen?How can this happen?

GPS developed for military useGPS developed for military use– Adequate for military operationsAdequate for military operations

Dropping bombs, search and rescue, landing military Dropping bombs, search and rescue, landing military planesplanes

Not built for high integrity applicationsNot built for high integrity applications– Not adequate for civilian operations involving Not adequate for civilian operations involving

safety of life and large-scale economicssafety of life and large-scale economics Landing commercial airliners, navigating in harbors Landing commercial airliners, navigating in harbors

and inter-coastal waterwaysand inter-coastal waterways Using GPS for time synchronization of networksUsing GPS for time synchronization of networks

What type of monitoring is What type of monitoring is needed?needed?

Expected service levelsExpected service levels– ““No worse than current performance”No worse than current performance”– ““Find and fix problems promptly”Find and fix problems promptly”

Specified service levelsSpecified service levels– GPS System SpecificationGPS System Specification

Service commitmentsService commitments– GPS Standard Positioning Service GPS Standard Positioning Service

(SPS) Performance Standard(SPS) Performance Standard

Expected service levelsExpected service levels

GPS SIS User Range Error Trend: 1 January 1997 - 31 December 2002

0

1

2

3

4

5

6

7

8

9

10

RM

S E

stim

ated

Ran

ge

Dev

iati

on

(E

RD

)

Worst Daily SV RMS ERD Daily Constellation RMS ERD Best Daily SV RMS ERD

Does not include data from PRN22 failure on 28 July 2001

1997 1998 1999 2000 2001 2002

Constellation User Range Error Specification

Civil Monitoring Features Civil Monitoring Features

Monitor all civil signals and dataMonitor all civil signals and data Monitoring tailored to GPS failure Monitoring tailored to GPS failure

modesmodes Instant reporting of anomalies to Instant reporting of anomalies to

satellite operatorssatellite operators Instant notification of service failure Instant notification of service failure

impacts to usersimpacts to users Ability to archive dataAbility to archive data

Civil Monitoring Benefits Civil Monitoring Benefits

Adding new measuring capability means Adding new measuring capability means we can measure things we could not we can measure things we could not previouslypreviously– more robust trackingmore robust tracking– position domain assessmentsposition domain assessments

… … and use these new capabilities to our and use these new capabilities to our advantageadvantage– Effects-based operationsEffects-based operations– More rapid correction of problemsMore rapid correction of problems– Awareness of problems before the phone ringsAwareness of problems before the phone rings

White House PolicyWhite House Policy

U.S. Space-Based Positioning, U.S. Space-Based Positioning, Navigation, and Timing PolicyNavigation, and Timing Policy– Authorized by the PresidentAuthorized by the President– Authorized December 8, 2004Authorized December 8, 2004– GPS civil performance monitoring funded GPS civil performance monitoring funded

by agencies requiring these capabilitiesby agencies requiring these capabilities– Secretary of Transportation to ensure Secretary of Transportation to ensure

the performance monitoring of U.S. civil the performance monitoring of U.S. civil space-based PNT services space-based PNT services

White House PolicyWhite House Policy ““The continuing growth of services based on the GPS presents The continuing growth of services based on the GPS presents

opportunities, risks, and threats to U.S. national, homeland, and opportunities, risks, and threats to U.S. national, homeland, and economic security. The economic security. The widespread and growing dependencewidespread and growing dependence on on the GPS of military, civil, and commercial systems and the GPS of military, civil, and commercial systems and infrastructures infrastructures has made many of these systems inherently has made many of these systems inherently vulnerablevulnerable to unexpected interruption in positioning, navigation, to unexpected interruption in positioning, navigation, and/or timing services.” Page 2 para 4and/or timing services.” Page 2 para 4

““The US The US must continue to improve and maintainmust continue to improve and maintain the GPS, the GPS, augmentations, and backup capabilities to meet growing national, augmentations, and backup capabilities to meet growing national, homeland, and economic security requirements, for civil homeland, and economic security requirements, for civil requirements, and to meet commercial and scientific demands. requirements, and to meet commercial and scientific demands. In addition, the diverse requirements for and multiple applications In addition, the diverse requirements for and multiple applications of space-based positioning, navigation, and timing services, of space-based positioning, navigation, and timing services, require stablerequire stable yet adaptable policies and yet adaptable policies and management management mechanismsmechanisms.” Page 2, para 5.” Page 2, para 5

White House PolicyWhite House Policy ““GPS GPS civil signalcivil signal performance monitoringperformance monitoring… will be … will be funded funded

by the agencyby the agency or agencies requiring those services or or agencies requiring those services or capabilities, including out-year procurement and capabilities, including out-year procurement and operations costs.” Page 5, para 6operations costs.” Page 5, para 6

““The The SECTRANS shall ensureSECTRANS shall ensure, in cooperation with the , in cooperation with the Secretary of Defense and Secretary of Homeland Security, Secretary of Defense and Secretary of Homeland Security, the the performance monitoring of U.S. civil space-based performance monitoring of U.S. civil space-based positioning, navigation, and timing servicespositioning, navigation, and timing services.” Page 8, para .” Page 8, para 55

How to implement...How to implement...

What architecture?What architecture? Who should do the monitoring?Who should do the monitoring?

Architecture (my view)Architecture (my view)

Real time monitoring done by OCSReal time monitoring done by OCS– Range and position domain Range and position domain

assessmentsassessments

Non-real time monitoring done by Non-real time monitoring done by external agenciesexternal agencies– Signal waveform and power levelsSignal waveform and power levels

Agency roles (my view)Agency roles (my view)

Office Secretary of Transportation (DOT)Office Secretary of Transportation (DOT)– coordinate; establish MOUscoordinate; establish MOUs

US Air Force (DoD)US Air Force (DoD)– Operate real-time monitoring servicesOperate real-time monitoring services– Respond to anomaliesRespond to anomalies

US Coast Guard (DHS) and FAA (DOT)US Coast Guard (DHS) and FAA (DOT)– Respond to civilian complaintsRespond to civilian complaints– Coordinate non-real-time monitoringCoordinate non-real-time monitoring

Coordinate with USAF when non-compliantCoordinate with USAF when non-compliant

Defining Civil MonitoringDefining Civil Monitoring

DOT is defining what is meant by DOT is defining what is meant by civil GPS monitoringcivil GPS monitoring– GPS Civil Service Monitoring GPS Civil Service Monitoring

Performance SpecificationPerformance Specification– To be used when implementing GPS To be used when implementing GPS

civil monitoring capabilitycivil monitoring capability Applies only to core GPS serviceApplies only to core GPS service Not application specificNot application specific

The Future: General StepsThe Future: General Steps

Consider ways to implement civil Consider ways to implement civil monitoring into current and future monitoring into current and future infrastructureinfrastructure– Add capabilities to the Legacy OCSAdd capabilities to the Legacy OCS– Incorporate monitoring in the new OCXIncorporate monitoring in the new OCX

Address direction in White House Address direction in White House policy relative to civil performance policy relative to civil performance monitoringmonitoring

The Future: Specific StepsThe Future: Specific Steps

GPS Operations CenterGPS Operations Center– New vision for GPS operations in 2 SOPSNew vision for GPS operations in 2 SOPS

24 hour operation begun in Feb 200524 hour operation begun in Feb 2005 Focused on effects-based operationFocused on effects-based operation

Legacy Accuracy Improvement Legacy Accuracy Improvement InitiativeInitiative– Addition of six NGA monitor stationsAddition of six NGA monitor stations

100% redundant coverage of all signals100% redundant coverage of all signals C/A code trackingC/A code tracking

When will this all be done? When will this all be done? (my view)(my view)

Expanded coverage, improved Expanded coverage, improved situational awarenesssituational awareness– This yearThis year

Formal civil performance monitoringFormal civil performance monitoring– Next 2 to 5 yearsNext 2 to 5 years

Comprehensive monitoring capabilityComprehensive monitoring capability– OCX - 2012+OCX - 2012+

SummarySummary

Civil monitoring is Civil monitoring is importantimportant– Satellite operators need itSatellite operators need it– Users need itUsers need it– GPS needs it to stay competitiveGPS needs it to stay competitive

Steps are being takenSteps are being taken– Capabilities are being defined and Capabilities are being defined and

incorporatedincorporated– Implementation will be incrementalImplementation will be incremental

Further ReadingFurther Reading ION GPS 1993, “GPS Integrity: An MCS Perspective”ION GPS 1993, “GPS Integrity: An MCS Perspective” GPS World, “GPS for the Rest of Us: Monitoring the GPS World, “GPS for the Rest of Us: Monitoring the

Civil Signals”, 1 Sep 2003Civil Signals”, 1 Sep 2003 ION National Technical Meeting 2003, “Defining the ION National Technical Meeting 2003, “Defining the

Elements of a Civil GPS Monitoring Service”Elements of a Civil GPS Monitoring Service” ION National Technical Meeting 2005, “DION National Technical Meeting 2005, “Development

of a Performance Specification for Civil Monitoring” GPS Operations Center Web Site:

www.schriever.af.mil/GpsSupportCenterwww.schriever.af.mil/GpsSupportCenter “Archives”