An Overview of Civil GPS Monitoring John W. Lavrakas ION Western Regional Vice President Presented to the So. California Section ION March 31, 2005 Aerospace Corp. El Segundo, CA The 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

Overview n Background on civil GPS monitoring n What has been going on recently n The new White House policy directive n Implementation approaches n Future plans

Background n GPS has extensive monitoring of the signal and the service –Worldwide network of monitor stations –24-hour crews –Automated and manual checks of data n Is it adequate? Not really

What’s missing? n Signal monitoring n C/A code not continuously monitored n Not 100% coverage of signals n Existing receivers can’t track large clock runoffs n Navigation message monitoring n Nav message send/receive checked but not content n Service monitoring n Only range errors, signal availability checked n No formal checks of position and time accuracy, service availability

What has gone wrong? n Single Frequency Iono Coefficients –28 May - 02 Jun 2002, single frequency iono coefficients incorrect n Partition reconciliation anomaly –12 Mar - 22 Mar 1993, time transfer error, 15 ns over six days n SVN19/PRN19 “evil waveform” – meter vertical position errors

What has gone wrong? n Invalid almanac –28 Mar 2000 GPS almanac contained incorrect information n When used in GPS modeling tools, resulted in generation of incorrect PDOP and SEP values

What has gone wrong? n Clock failure –28 Jul 2001 SVN22 clock failure n Range errors in excess of 200,000 meters n Occurred over southern Pacific Ocean –For about a half an hour not in view of any OCS monitor stations n Clock failure –1 Jan 2004 SVN23 clock failure n Transmission of ranging errors up to 280,000 meters with duration of 2.75 hours

How can this happen? n GPS developed for military use –Adequate for military operations n Dropping bombs, search and rescue, landing military planes n Not built for high integrity applications –Not adequate for civilian operations involving safety of life and large-scale economics n Landing commercial airliners, navigating in harbors and inter-coastal waterways n Using GPS for time synchronization of networks

What type of monitoring is needed? n Expected service levels –“No worse than current performance” –“Find and fix problems promptly” n Specified service levels –GPS System Specification n Service commitments –GPS Standard Positioning Service (SPS) Performance Standard

Expected service levels

Civil Monitoring Features n Monitor all civil signals and data n Monitoring tailored to GPS failure modes n Instant reporting of anomalies to satellite operators n Instant notification of service failure impacts to users n Ability to archive data

Civil Monitoring Benefits n Adding new measuring capability means we can measure things we could not previously –more robust tracking –position domain assessments n … and use these new capabilities to our advantage –Effects-based operations –More rapid correction of problems –Awareness of problems before the phone rings

White House Policy n U.S. Space-Based Positioning, Navigation, and Timing Policy –Authorized by the President –Authorized December 8, 2004 –GPS civil performance monitoring funded by agencies requiring these capabilities –Secretary of Transportation to ensure the performance monitoring of U.S. civil space- based PNT services

White House Policy n “The continuing growth of services based on the GPS presents opportunities, risks, and threats to U.S. national, homeland, and economic security. The widespread and growing dependence on the GPS of military, civil, and commercial systems and infrastructures has made many of these systems inherently vulnerable to unexpected interruption in positioning, navigation, and/or timing services.” Page 2 para 4 n “The US must continue to improve and maintain the GPS, augmentations, and backup capabilities to meet growing national, homeland, and economic security requirements, for civil requirements, and to meet commercial and scientific demands. In addition, the diverse requirements for and multiple applications of space-based positioning, navigation, and timing services, require stable yet adaptable policies and management mechanisms.” Page 2, para 5

White House Policy n “GPS civil signal performance monitoring… will be funded by the agency or agencies requiring those services or capabilities, including out-year procurement and operations costs.” Page 5, para 6 n “The SECTRANS shall ensure, in cooperation with the Secretary of Defense and Secretary of Homeland Security, the performance monitoring of U.S. civil space-based positioning, navigation, and timing services.” Page 8, para 5

How to implement... n What architecture? n Who should do the monitoring?

Architecture (my view) n Real time monitoring done by OCS –Range and position domain assessments n Non-real time monitoring done by external agencies –Signal waveform and power levels

Agency roles (my view) n Office Secretary of Transportation (DOT) –coordinate; establish MOUs n US Air Force (DoD) –Operate real-time monitoring services –Respond to anomalies n US Coast Guard (DHS) and FAA (DOT) –Respond to civilian complaints –Coordinate non-real-time monitoring n Coordinate with USAF when non-compliant

Defining Civil Monitoring n DOT is defining what is meant by civil GPS monitoring –GPS Civil Service Monitoring Performance Specification –To be used when implementing GPS civil monitoring capability n Applies only to core GPS service n Not application specific

The Future: General Steps n Consider ways to implement civil monitoring into current and future infrastructure –Add capabilities to the Legacy OCS –Incorporate monitoring in the new OCX n Address direction in White House policy relative to civil performance monitoring

The Future: Specific Steps n GPS Operations Center –New vision for GPS operations in 2 SOPS n 24 hour operation begun in Feb 2005 n Focused on effects-based operation n Legacy Accuracy Improvement Initiative –Addition of six NGA monitor stations n 100% redundant coverage of all signals n C/A code tracking

When will this all be done? (my view) n Expanded coverage, improved situational awareness –This year n Formal civil performance monitoring –Next 2 to 5 years n Comprehensive monitoring capability –OCX

Summary n Civil monitoring is important –Satellite operators need it –Users need it –GPS needs it to stay competitive n Steps are being taken –Capabilities are being defined and incorporated –Implementation will be incremental

Further Reading n ION GPS 1993, “GPS Integrity: An MCS Perspective” n GPS World, “GPS for the Rest of Us: Monitoring the Civil Signals”, 1 Sep 2003 n ION National Technical Meeting 2003, “Defining the Elements of a Civil GPS Monitoring Service” n ION National Technical Meeting 2005, “D n ION National Technical Meeting 2005, “Development of a Performance Specification for Civil Monitoring” n n GPS Operations Center Web Site: “Archives”