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Navstar GPS Constellation Status

CGSIC. Navstar GPS Constellation Status. Doug Louden Chief, GPS Liaison, USCG HQ AF Space Command GPSOC, Civil Analyst Colorado Springs, CO. Peterson AFB (719) 554-3582 Schriever AFB (719) 567-5093. 07 May 2006. Outline. Launch recommendations Empirical Clock Data

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Navstar GPS Constellation Status

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  1. CGSIC Navstar GPS Constellation Status Doug Louden Chief, GPS Liaison, USCG HQ AF Space Command GPSOC, Civil Analyst Colorado Springs, CO. Peterson AFB (719) 554-3582 Schriever AFB (719) 567-5093 07 May 2006

  2. Outline • Launch recommendations • Empirical Clock Data • Constellation Health Assessment • Nav Coverage • NAVCEN and Interference Reporting Procedures • Constellation Performance and Summary

  3. IIR-(M) Launch Considerations • So far, launch recommendations: • C4 (SVN 53), A2 (next launch, SVN 58) • Can re-phase to desired location if launch is within plane

  4. GPS IIR/MLV Launch Window Opening Time - 2006(Descending/Ascending Node Injection) IIR-15(M) Weather unstable at Cape during Sept 06 launch window for IIR-15(M)

  5. IIR-15(M) - Eclipse window • Recommended • launch window SVN25 (A2) eclipse season no factor for Sep 06 launch

  6. Weather/Eclipse Season • IIR-15(M) launch in Sep 06 to replace SVN25 at A2 • Weather unstable at Cape in Sep 06 for launch to A2 • Multiple weather delays with IIR-12 (Jul 04) and IIR-13 (Nov 04) • SVN25 at A2 has next eclipse season: mid-June to mid-July 06 • SVN25 will go through eclipse before replacement • SVN25 eclipse season poses no problem for a Sep 06 launch

  7. Launch Recommendations • Launch IIR-15(M) to A2 in Sep 06 to replace SVN25 • No need to decommission an SV, 29 PRNs in use, 1 is available • Launch IIR-16(M) NET Apr 07 (maybe Nov 07) • Determine IIR-16(M) plane/slot at future date • Determine a vehicle to remove from service for PRN prior to IIR-16(M) launch

  8. Cross-plane back-up:  A satellite in the 6 plane constellation providing back-up navigation coverage for a failed satellite in an adjacent plane thereby minimizing the impact of the failure. Close/Distant pairs:  The GPS Optimized 24 constellation is a non-symmetric 6 plane constellation.  Each plane in the Optimized 24 constellation has four satellites grouped as a close pair (separated by about 30 deg Argument of Latitude) and a distant pair (separated by about 130 deg Argument of Latitude).   On-orbit storage:  The time between when a satellite or component is launched and when it is initialized and operated.   Expandable slot: The B1, D2 or F2 slots of the Expandable 24 constellation which, when “expanded”, forms a “fore” and “aft” slot, straddling the original baseline slot, thus providing an additional close pair and better constellation performance than the 24 + 3.   Expanded slot:  An expandable slot in the Expandable 24 constellation that has been augmented by an additional satellite and has been slightly rephased so that the new close pair of satellites straddle the original location. Optimized 24 Constellation:  The non-symmetric six plane GPS constellation as documented in the currently approved SPS PS.  This structure has four satellites per plane grouped as a close pair and a distant pair. Also referred to as the “Baseline 24” constellation. Expandable 24 Constellation:  The Optimized 24 Constellation with three expandable baseline slots defined in the B, D, and F planes to create an additional close pair. Also referred to as the “Optimized 27” constellation. Glossary

  9. Empirical Clock History • Recent experience shows IIA rubidium clocks that have been in storage for more than 8 years prior to use have had significantly shorter life times than clocks with less than 8 years of on-orbit storage • Clocks listed were turned on after more than 8 years on orbit • SVN 25 Rb FS #1 currently on last clock with erratic performance since turn-on • SVN 39 Rb FS #1 lasted approx. 50 days • SVN 35 Rb FS #2 lasted approx. 128 days • SVN 23 Rb FS #1 lasted approx. 48 days • SVN 27 Rb FS #2 lasted approx. 16 days • Early life failures on cesium clocks have occurred, but there is no obvious relationship between failure and on-orbit storage time • General reliability on cesium clocks has been better than rubidium clocks

  10. II/IIA Clock History Primary Slot Vehicles > 12 years old • Empirical clock history may influence expected reliability SVN 25, 35 and 36 have a high likelihood of failing due to clocks (all are II/IIAs)

  11. GPS Locations 1 Apr 06(GLAN) 37 Rephase 1 deg day drift 180 43 F3 36 C1 160 B4 35 51 E1 37 in April 140 30 B2 A1 39 GLAN (deg) 46 D2 29 120 33 C2 24 59 C3 100 F2 26 B1 56 40 E3 80 D4 34 25 A2 IIR-15(M) 60 61 D1 53 41 F1 C4 54 E4 Empty Slot 40 32 44 B3 E2 47 Block II A4 27 20 45 D3 Block IIA 60 F4 38 A3 0 Block IIR 15 Block IIR-M A B C D E F

  12. Constellation Status Health Total SVs in Category Changes Since Last Year • 17 (-1) SVs past design life • 12 (-1) SVs past pre-launch mean life estimate (MLE) • 14 (-1,+1) SVs one component away from nav mission failure • 9 (+0) SVs one component away from bus failure • Anomaly Summary • SVN39 (C5) Clock swap X2 • SVN25 (A2) Clock swap (on last clock) • SVN30 (B2) Clock swap SVN 31 disposal 15 Dec 05 SVN 25 last clock

  13. 1 2 3 4 Good Dead Suspect Unused Clock Status = SVN 00 PRN 00 Rubidium 1 2 3 4 Cesium NAV BUS Clocks Constellation Assessment As Of 1 Apr 06 A B C D E F Design Life: II/IIA - 7.5 yrs IIR - 10 yrs IIF - 15 yrs SVN 51 PRN 20 SVN36 PRN06 SVN 61 PRN 02 SVN 56 PRN 16 SVN 39 PRN 09 SVN 41 PRN 14 MLE: II= 12.05 IIA= 13.03 IIR= 14.18 IIR-M=8.60 yrs MMD: IIF= 11.0yrs SVN 30 PRN 30 SVN 33 PRN 03 SVN 47 PRN 22 SVN 26 PRN 26 SVN 25 PRN 25 SVN 46 PRN 11 SVN 38 PRN 08 SVN 43 PRN 13 SVN 44 PRN 28 SVN 59 PRN 19 SVN 40 PRN 10 SVN 45 PRN 21 Vehicle count: 29 total 1 IIs 15 IIAs 13 IIRs (includes 1st IIR-M) SVN 34 PRN 04 SVN 54 PRN 18 SVN 60 PRN 23 SVN 35 PRN 05 SVN 27 PRN 27 SVN 53 PRN 17 M SVN PRN SVN PRN SVN PRN SVN 37 PRN 07 SVN 29 PRN 29 SVN 15 PRN 15 IIRs : only 3 Rb clocks SVN PRN SVN PRN SVN 24 PRN 24 SVN PRN SVN 32 PRN 01 SVN PRN N:/Althouse/GPS-/Program Summary/Problem Vehicle Listing

  14. A-Plane Analysis • Average vehicle age: 12.13 years • SVN25, 27, 38 and 39 all past 7.5 year design life • SVN25, 27 and 39 past pre-launch MLE • Problem vehicles in primary slots: SVN 25, 27 and 38 • SVN27 is single string in nav, suspect TT&C, last clock • SVN25 solar array degradation, operating on 3 wheels, single string nav, last clock • SVN38 is single string in TT&C SVN 25 candidate for IIR-15(M)

  15. SVN 39 and 53 out 6 N 128.7 E PDOPmax = 10.33 UNCLASSIFIED

  16. SVN 25 Status • Age = 14 years • Single String in Nav • NDU power supply failed 23 Dec 05 • Rubidium 1 (last clock) selected 25 Dec 05, performance variable • Single String in Bus • Operating on three wheels • Wheel #3 electronics failed in 2003 • Double lubed wheels additional failures unlikely • Solar array degradation • Currently being power managed • High constellation coverage value • SVN 32 and SVN 37 will provide cross plane backup • SVN25 recommended for replacement by IIR-15(M)

  17. SVN 25 and 39 Out 64 S 95.8 E PDOPmax = 11.65

  18. B-Plane Analysis • Average vehicle age: 6.14 years • Youngest average vehicle age of any plane • SVN 30 and 35 past 7.5 year design life • SVN 35 past pre-launch MLE • Problem vehicles in primary slots: SVN 30, 35 and 56 • SVN 30 is single string in nav • SVN 56 MDU redundancy uncertain • SVN 35 operating on last clock • Swapped to RFS#1 on 2 Sep 05 • SVN44 reaction wheel restored with Flight Software Patch • Fifth slot vehicle: None • Primary Slot for Expanded Constellation

  19. C-Plane Analysis • Average vehicle age: 8.34 years • ALL SVN’s EXCEPT SVN53 and 59 past design life • All SVN’s EXCEPT SVN33, 53 and 59 past pre-launch MLE • Problem vehicles in primary slots: SVN36 • SVN36 is on its last clock • SVN31 Disposed • SVN37 has multiple component failures; array issues • SVN28 maintained by 1 SOPS • Non mission capable • Re-phasings: SVN37 was rephased to provide cross plane back up of slot A2 SVN37 on station as of Mid April

  20. D-Plane Analysis D SVN 61 g y SVN 46 g y SVN 45 y g SVN 34 g g SVN 15 y y SVN 24 y y • Average vehicle age: 8.85 years • SVN15, 24 and 34 are past 7.5 year design life • SVN15, 24 and 34 are past pre-launch MLE • Problem vehicles in primary slots: SVN 45, 46 and 61 • SVN61 MDU Baseband failure • SVN 46 is single string in nav • SVN24 is a three-wheeled vehicle operating on last clock • Fifth slot vehicle: None

  21. E-Plane Analysis • Average vehicle age: 7.6 years • SVN40 is past 7.5 year design life • Problem vehicles in primary slots: SVN40 • SVN40 FSDU and NDU are single string • SVN23 maintained by 1 SOPS (Non-Operational) • Potentially mission capable E Plane robust overall

  22. F-Plane Analysis • Average vehicle age: 10.82 years • SVN26, 29, 32 and 43 are past 7.5 year design life • SVN26, 29 and 32 past pre-launch MLE • Problem vehicle in primary slot: SVN26 • SVN26 single string in both bus and nav; solar array degradation • Fifth slot vehicle: SVN29 • Additional DCEA power instability could force disposal • Primary Slot for Expanded Slot Constellation • Re-phasing: None SVN32 acting as cross plane back-up for SVN25 and 36 (operating on last clock since 1996)

  23. GPS On-orbit Satellite Predicted Life Remaining (Oct 05 Reliability) Decommissioned/Out-of-Service

  24. GPS Satellite Age (as of: 1 Apr 06) 16 Blk II 14 Block IIR MLE Block II & IIA MLE Blk IIA 12 Blk IIR 10 Design Life: II/IIA - 7.5 yrs IIR - 10 yrs IIRM - 8.5 yrs IIF - 15 yrs Blk IIR-M 8 Operational for 4.5 yrs – Used for Test & Checkout Deactivated Block IIR-M MLE 6 4 2 Years Satellite Vehicle 15 24 25 28 26 27 32 29 37 39 35 34 36 33 40 30 38 43 46 51 44 41 54 56 45 47 59 60 61 53

  25. Accuracy Equation Poor HDOP Poor VDOP Good DOP Good Moderate Poor DOP 01 2 3 4 5 6 Accuracy = Statistical Conversion * DOP * URE2+UEE2 Accuracy; DOP is a big part of the accuracy equation URE True Range Nav Message UEE GA MCS MS 50% (CEP) ~68% (~DRMS) ~95% (~2DRMS)

  26. SPS PS Requirements • Sec 3.2, table 3-2: • Sec 3.2, paragraph 2: • In support of the service availability standard, 24 operational satellites must be available on orbit with 0.95 probability (averaged over any day).

  27. NAVCEN & Data Broadcasts Subscription services that deliver Operational Advisory Broadcast (GPS Status Messages) and/or the Notice Advisory to NAVSTAR Users (NANU) via List servers. • GPS Status List server:This service provides the subscriber with an e-mail containing the newly updated Status Message that is sent by the NAVCEN within 60 minutes of notification by the Air Force of a change to the GPS Constellation. • NANU List server: This service provides the subscriber with an e-mail containing the NANU that is sent by NAVCEN within 60 minutes of notification by the Air Force of a change to the GPS Constellation. • CGSIC List server: This service provides the subscriber with an e-mail containing GPS and CGSIC announcements.

  28. Interference Reporting • The Navigation Center appreciates your reports regarding service degradations, outages, or other incidents. • Please report problems via our GPS Problem Report Page. • After a GPS user completes these forms, they are sent to a database for tracking, analysis, and resolution. • Reports may be received via phone/fax.

  29. Interference Reporting Process • User contacted for additional information, if necessary. • If the report is aviation related it will be directed to the FAA for tracking, analysis, and resolution. • Maritime and terrestrial related reports will be processed simultaneously by the USCG GPS Liaison to the GPS Operations Center at Schriever AFB and NIS personnel for resolution. • Check for constellation events during reported outage period by using NANU. • Perform analysis of constellation activity during reported outage times.

  30. Interference Reporting Process • Upon finding a resolution, the NIS will notify the user; if the report is not resolved for 30 days, the user will be notified of the situation. • 30 days after reporting findings to the user, the NIS will again contact the user to assess the situation and submit a new report if necessary. • Focus is on Customer Service and Satisfaction.

  31. Navigation Information Service • http://www.navcen.uscg.gov • http://www.navcenter.org (mirror site) • E-mail: TIS-PF-NISWS@uscg.mil • Phone: +1 703 313 5900 • Fax: +1 703 313 5920

  32. Constellation Summary • 29 satellites on-orbit • 29 satellites set healthy to users • 0 satellites launched(2006) • 1 satellites decommissioned • 1 satellite disposed (SVN 31) • Component changes since Oct 2005 • SVN 39 Clock swap: Cs to Rb to Cs • SVN 25 Clock swap: (Cs to last Rb) and NDU power supply failure • SVN 30 Clock swap: (Rb to Rb) • Constellation changes since Oct 2005 • SVN 53 operational 16 Dec 05 • SVN 37 rephase started Jan 06 arrived target GLAN 27 April

  33. Summary and GPS Future Recommendations • Launch IIR-15(M) to A2 in Sep 06 to replace SVN25 • No need to decommission an SV, 29 PRNs in use, 1 is available (PRN 31) • Launch IIR-16(M) NET Apr 07 • Determine IIR-16(M) plane/slot in future • Determine a vehicle to remove from service for PRN prior to IIR-16(M) COMPAT test at a future date

  34. CGSIC GPS Constellation Status Thank you Doug Louden Chief, GPS Liaison, USCG 07 May 2006

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