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Wide Area Augmentation System (WAAS) Operations Team AJW-192

Offline Monitoring. Wide Area Augmentation System (WAAS) Operations Team AJW-192. WIPP. Stephen Gordon Chad Sherrell Brad Dworak May 17, 2010. Introduction. This presentation covers the 1 st Quarter of 2010 (2010-01-01 – 2010-03-31)

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Wide Area Augmentation System (WAAS) Operations Team AJW-192

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  1. Offline Monitoring Wide Area Augmentation System (WAAS) Operations TeamAJW-192 WIPP Stephen Gordon Chad Sherrell Brad Dworak May 17, 2010

  2. Introduction • This presentation covers the 1st Quarter of 2010 • (2010-01-01 – 2010-03-31) • The week of February 7-13, 2010 was used for some of the detailed analysis • Enhancements • Added GSQA Analysis • CCC and SQM • Analyzed data for the first 4 days of every week for the whole quarter • Next Steps • Add antenna offsets over time for launched or transitioned satellites • Migrate ephemeris database to oracle. • Analyze data for entire quarter

  3. Code Carrier Coherence Assertion The a priori probability of a CCC failure is less than 1x10-4 per set of satellites in view per hour for GPS satellites and 1.14x10-4 for GEO satellites.

  4. Code Carrier Coherence Monitoring Approach • Monitor for all CCC Trips • All CCC Monitor Trips are investigated • For GEO Satellites • Plots of the CCC test statistic for GEO satellites are analyzed whenever a trip occurs to determine the source of the trip • Used the first 4 days of every week for the entire quarter

  5. Code Carrier Coherence Trips Date GEO C&V 2010-01-04 19:52:09 138 ZTL 2010-01-04 19:53:50 138 ZLA 2010-01-04 20:58:47 138 ZDC 2010-01-04 20:58:50 138 ZLA 2010-01-25 06:21:29 138 ZLA ZTL 2010-01-28 03:26:32 138 ZLA ZTL 2010-02-19 19:53:43 138 ZDC 2010-02-19 19:53:46 138 ZTL 2010-02-26 18:17:59 138 ZDC 2010-02-26 18:18:00 138 ZTL

  6. Clock Runoff Assertion The a priori probability of a GPS satellite failure resulting in a rapid change in the GPS clock correction is less than 1.0x10-4 per satellite. Monitoring Approach Events typically result in a fast correction that exceeds 256 meters When this occurs, the satellite is set Do Not Use until the correction reaches a reasonable size Events where the satellite is set Do Not Use from excessively large fast corrections while the satellite is healthy are recorded

  7. Clock Runoff No Clock Runoff Events between 2010-01-01 and 2010-03-31

  8. Signal Quality Monitor Assertion The a priori probability of a signal deformation (SD) failure is less than 2.4x10-5 per set of satellites in view per hour for GPS or GEO satellites. The worst-case range errors due to nominal signal deformations are more than 25cm on any satellite signal relative to the other satellites in view. Monitoring Approach All SQM Trips will be monitored for and investigated Max and Median data for each metric will be plotted by Requested UDRE Monitoring for discrepancies between satellite Plots are for the first 4 days of every week for the entire quarter

  9. GEO Signal Quality • Assertion The WAAS SIS satisfies the requirements for code-carrier coherence and fractional coherence stated in sections 3.1.4.2 and 3.1.4.3 of the [draft] system specification FAA-E-2892c • Monitoring Approach • Collect WAAS SIS data from each GEO using GUST receivers connected to dish antennas • Compute and plot the metrics outlined in sections 3.1.4.2 and 3.1.4.3 of FAA-E-2892c • Examine plots, tabulate max metric values and pass/fail states, analyze failures in further detail to identify possible causes

  10. Performance Summary 16

  11. PRN 135 Short-term CCC Note: inordinate values occur on days with switchovers 17

  12. PRN 135 Long-term CCC Note: inordinate values occur on days with switchovers 18

  13. PRN 135 Short-term CC Note: inordinate values occur on days with switchovers 19

  14. PRN 135 Long-term CC Note: inordinate values occur on days with switchovers 20

  15. PRN 138 Short-term CCC Note: inordinate values occur on days with switchovers 21

  16. PRN 138 Long-term CCC Note: inordinate values occur on days with switchovers 22

  17. PRN 138 Short-term CC Note: inordinate values occur on days with switchovers 23

  18. PRN 138 Long-term CC Note: inordinate values occur on days with switchovers 24

  19. Ephemeris Assertion The CDF of GPS ephemeris errors in a Height, Cross-track, and Along-track (HCL) coordinate system is bounded by the CDF of a zero-mean Gaussian distribution along each axis whose standard deviations are osp-ephh, osp-ephc, and osp-ephl.The probability that a satellite’s position error is not characterized by this a priori ephemeris model is less than 10-4 per hour. Monitoring Approach Compare broadcast vs precise in HCL to ensure sigmas are less than 1m, 2.5m, 7.5m

  20. Ephemeris – Radial PRN: 26 2010-03-24 06:45:00 5.5184810167 PRN: 31 2010-01-13 06:45:00 2.38501512664 PRN: 15 2010-01-11 10:45:00 -2.092707392 PRN: 30 2010-01-20 02:30:00 -2.11129087523 PRN: 10 2010-01-13 06:45:00 -3.40434475736

  21. Ephemeris – In Track PRN: 26 2010-03-24 06:45:00 17.4014078019 PRN: 27 2010-01-14 06:00:00 8.45302081503 PRN: 27 2010-01-08 18:15:00 7.84084014132 PRN: 24 2010-03-26 09:15:00 7.80477731973 PRN: 27 2010-03-05 11:30:00 -8.74223583895

  22. Ephemeris – Cross Track PRN: 26 2010-03-24 06:45:00 6.62752789471 PRN: 18 2010-03-16 10:45:00 -3.82543157174

  23. RIC Outliers

  24. Ionospheric Threat Model Monitoring Assertion The values of and iono adequately protect against worst case undersampled ionosphere over the life of any ionospheric correction message, when the storm detectors have not tripped. Monitoring Approach Monitor for Chi^2 trips in the four regions CONUS > 1% Alaska > 2% Caribbean > 10% Other > 3%

  25. Monitoring Regions

  26. MAX 2010-01-06 MAX 2010-03-27

  27. MAX 2010-03-11 MAX 2010-01-20

  28. Daily Max Trips by Region CONUS C&V: ZDC Max Trips: 10 Date: 2010-01-06 ALASKA C&V: ZLA Max Trips: 6 Date: 2010-03-11 CARRIB C&V: ZDC Max Trips: 348 Date: 2010-03-27 OTHER C&V: ZLA Max Trips: 113 Date: 2010-01-20

  29. Antenna Monitoring Assertion The position error (RSS) for each WAAS reference station antenna is 10cm or less when measured relative to the ITRF datum for any given epoch. (Mexico City is allowed 25cm). The ITRF datum version (realization) is the one consistent with WGS-84 and also used for positions of the GPS Operational Control Segment monitoring stations.

  30. Purpose Accurate antenna positions needed to support DGPS applications Correct for Time Dependent Process Tectonic Plate Movement Subsidence Correct for Shift Events Seismic Maintenance WIPP Review for integrity issues Greater than 10 cm WIPP should review Greater than 25 cm WIPP must review Special case for Mexico City (25 cm for review) Project the need for a WAAS Antenna Coordinate Update

  31. Survey Details Survey Date 2010-01-15 (1566d5) used for most sites 2010-01-16 (1566d6) used for ZDV and CDB Cross Compared Against CSRS-PPP WFO Release 1 All Coordinates Projected to midpoint of WFO Release 2 and WFO Release 3 2011-04-01

  32. Results Against CSRS-PPP All sites less than 5 cm. Against WFO Release 1 All sites less than 5 cm except CDB. Average Deltas

  33. Results - Continued MMX The subsidence rate for MMX was computed using data over a span of the past two years and the estimated subsidence rate is now 25.85 cm/yr which is down from last year's estimate of 26.1 cm/yr.

  34. Code Noise and Multipath (CNMP) Overbounding • Assertion • The Code Noise and Multipath (CNMP) error bound is sufficiently conservative such that the error in linear combinations of L1 and L2 measurements is overbounded by a Gaussian distribution with a sigma described by the Root Sum Square (RSS) of L1 and L2 CNMP error bounds except for biases, which are handled separately.3 • Monitoring Approach • Bounding for L1, IFPR, Delay • Aggregate and WRE Slices • All bounding failures analyzed in further detail

  35. Equations Used • Cumulative distribution function (CDF): • For examining the behavior at larger values of x: • Pass is Δx > 0 for all |x|>0.25

  36. Aggregate Plot of CNMP Delay

  37. Aggregate Plot of CNMP IFPR

  38. Aggregate Plot of CNMP RDL1

  39. CNMP Tabular Results from WRE Slices *This is a subset of sites as an example

  40. Summary Quarterly monitoring results continue to support specific assertions called for in the HMI document Further investigation planned for PRN-10 SQM observations since Metric 3 appeared “out of family” PRN-18 SQM performance was nominal The CCC Test Statistic for the GEOs is near the trip threshold frequently

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