# Presentation: 741529

##  Navstar GPS Constellation Status  

**23 May 2006**

**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**

**         ****CGSIC**

## Outline

** ****Launch recommendations**
**Constellation Health Assessment **
**Nav Coverage**
**NAVCEN and Interference Reporting Procedures **
**Constellation Performance and Summary**

## IIR-(M) Launch Considerations

**So far, launch considerations:**
**C4 (SVN 53), A2 (next launch, SVN 58)**
**Can re-phase to desired location if launch is within plane**

## Weather unstable at Cape during Sept 06 launch window for IIR-15(M)

**GPS IIR/MLV Launch Window Opening Time - 2006****(Descending/Ascending Node Injection)**

**Weather *****unstable***** at Cape during Sept 06 launch window for IIR-15(M)**

**IIR-15(M)**

## SVN25 (A2) eclipse season no factor for Sep 06 launch

- - Eclipse window

- Recommended
-  launch window

**IIR-15(M)**

**SVN25 (A2) eclipse season no factor for Sep 06 launch**

## 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

## 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 **
**Determine IIR-16(M) plane/slot at future date**
**Determine a vehicle to remove from service for PRN prior to IIR-16(M) launch**

## Glossary

**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.

## GPS Locations 1 Apr 06(GLAN)

- Block II

- Block IIA

- Block IIR

- A

- C

- B

- E

- D

- F

- 80

- 100

- 120

- 160

- 180

- 0

- 20

- 40

- 60

**GLAN**
**(deg)**

- E2

- A3

- A1

- A2

- A4

- B3

- B4

- B2

- B1

- C1

- C2

- C3

- C4

- D1

- D2

- D3

- D4

- E1

- E3

- E4

- F1

- F2

- F3

- F4

- 38

- 27

- 25

- 39

- 30

- 56

- 44

- 35

- 36

- 33

- 59

- 37

- 34

- 61

- 45

- 46

- 40

- 54

- 60

- 43

- 26

- 41

- 15

- 29

- 51

- Empty Slot

- 47

- 53

- 32

- 24

***GPS Locations 1 Apr 06******(GLAN)***

- IIR-15(M)

- Block IIR-M

- Rephase
- 1 deg day drift

- 140

- 37 in April

## Constellation Status Health

**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**

***Constellation Status Health***

- Changes Since Last Year

- Total SVs in Category

**SVN 31 disposal 15 Dec 05**
**SVN 25 last clock**

## Constellation Assessment 

_**MLE:**_**   II= 12.05**
**             ****IIA= 13.03**
**             ****IIR= 14.18**
**             ****IIR-M=8.60 yrs**
_**MMD:**_**  IIF= 11.0yrs**

- Constellation Assessment

- N:/Althouse/GPS-/Program Summary/Problem Vehicle Listing

**As Of  1 Apr 06**

_**Design Life**_**:**
**II/IIA  ****	****-  7.5 yrs**
**IIR      ****	****-  10 yrs**
**IIF       ****	****-  15 yrs**

- IIRs : only 3 Rb clocks

**SVN**
**PRN**

- A  	    B	    C          D          E           F

**SVN36**
**PRN06**

**SVN 51**
**PRN 20**

**SVN 32**
**PRN 01**

**SVN 25**
**PRN 25**

**SVN 27**
**PRN 27**

**SVN 53**
**PRN 17**

**SVN 30**
**PRN 30**

**SVN 35**
**PRN 05**

**SVN 33**
**PRN 03**

**SVN 37**
**PRN 07**

**SVN 46**
**PRN 11**

**SVN 34**
**PRN 04**

**SVN 40 PRN 10**

**SVN 54**
**PRN 18**

**SVN 26**
**PRN 26**

- M

**SVN 38**
**PRN 08**

**SVN**
**PRN**

**SVN 44 PRN 28**

**SVN 39**
**PRN 09**

**SVN 15 PRN 15**

**SVN**
**PRN**

**SVN 56 PRN 16**

**SVN PRN **

**SVN 45 PRN 21**

**SVN**
**PRN**

**SVN 60 PRN 23**

**SVN 43**
**PRN 13**

**SVN 41 PRN 14**

**SVN 29**
**PRN 29**

**SVN**
**PRN  **

**SVN 24**
**PRN 24**

**SVN 47**
**PRN 22**

**SVN 59 PRN 19**

**SVN 61**
**PRN 02**

**SVN**
**PRN**

_**Vehicle count**_**: 29 total**
**1 IIs          **
**15 IIAs         **
**13 IIRs **
**     ****(includes 1st IIR-M)**

**Notes:**
	This is a constellation health status chart A3FS updates monthly.  This was developed by and is updated by our contractor support.  

	I’m going to walk you through how to read this quickly.  You can see our 24 primary slots and planes here.  You can also see that while we have 29 operational satellites, many of these are not in the best shape.

	You can see the little key on the lower left, which explains what all these colors mean.  We have spots for the BUS, the NAVigation payload, and the clocks on the satellite.  If either is yellow, the vehicle is down to a single string in that area, causing the vehicle status to be yellow.  Block II/IIA satellites have four clocks and Block IIRs have three clocks.  Let’s look at SVN 30, which is in slot B2.  The satellite is yellow because the NAV payload is yellow.  We have a backup chart with much more detail as to why it’s yellow.  You can also see that the satellite is on clock 1.  It also has a dead clock, a used clock that may be recoverable, and an unused clock.
	Let’s say you come back from Gen Klotz’s office and you hear that SVN 43’s clock died.  You can quickly look at this chart and see that SVN 43 has two unused clocks.  It takes up to two weeks for a clock to stabilize before we declare it Fully Mission Capable.
	For another example, let’s assume the last clock on SVN 25 fails before we launch to that spot in the fall.  You can see the A plane is already hurting and has no in-plane spares.  This means we’ve violated many policy statements and written GPS standards.  What is the impact and what would we do?
	<NEXT SLIDE>
Note to self:  IIF satellites will have 2 Cesiums and 1 Rubidiums

## SVN 39 and 53 out

**6 N  128.7 E**
**PDOPmax = 10.33**

## 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)**

## SVN 25 and 39 Out

**64 S   95.8 E**
**PDOPmax = 11.65**

## GPS On-orbit Satellite Predicted Life Remaining (Oct 05 Reliability) 

***GPS On-orbit Satellite Predicted Life Remaining****** (Oct 05 Reliability)****** ***

## GPS Satellite Age

**Blk II**

**Blk IIA**

**Blk IIR**

**Deactivated**

**Satellite Vehicle**

**Blk IIR-M**

**Years**

**24**

**25**

**28**

**26**

**27**

**32**

**29**

**37**

**39**

**35**

**34**

**36**

**33**

**40**

**30**

**43**

**38**

**46**

**51**

**15**

**44**

**41**

**54**

**56**

**45**

**47**

**59**

**60**

**61**

**53**

**2**

**4**

**6**

**8**

**10**

**Block IIR MLE**

**Block II & IIA MLE**

**12**

**14**

**Block IIR-M MLE**

**(as of:  1 Apr 06)**

**16**

**Operational for 4.5 yrs – Used for Test & Checkout**

***GPS Satellite Age***

_**Design Life**_**:**
**II/IIA  ****	****-  7.5 yrs**
**IIR      ****	****-  10 yrs**
**IIRM   ****	****-  8.5 yrs**
**IIF       ****	****-  15 yrs**

**Notes:**
This chart shows you the age of each operational satellite as well as one Test and Checkout bird.  The dashed lines are the design life and the Mean Life Expected, or MLEs, are depicted by the shaded areas.  MLEs are averaged per block and are based on historical performance data.

One may look at SVN 15 and say, “Obviously these satellites are lasting much longer than planned.  What’s the danger?”  Well, SVN 15 is the anomaly and not the norm.  You can see there are a bunch of missing satellites between 15 and 24.  Those are all dead.  You can see a large number of satellites approaching, or beyond, their MLEs

The average life of Block II and IIA vehicles is just under 10 years.

## Accuracy Equation

**Accuracy****  =  ****Statistical Conversion ***** DOP *   ****URE****2**** ****+**** ****UEE****2**** **

**~68% (~DRMS)**

**UEE**

**Nav**
**Message**

**~95% (~2DRMS)**

**50% (CEP)**

**  ****GA         MCS             MS**

**True**
**Range**

**Accuracy; DOP is a big part of the accuracy equation**

**URE**

## 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).**

| PDOP Availability Standard | Conditions and Constraints |
| --- | --- |
| ≥ 98% global Position Dilution of Precision (PDOP) of 6 or less

≥ 88% worst site PDOP of 6 or less |   Defined for position solution meeting the representative user conditions and operating within the service volume over any 24-hour interval.
  Based on using only satellites transmitting standard code and indicating “healthy” in the broadcast navigation message (sub-frame 1). |

##  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.**

**Notes:**
Subscription services that deliver GPS Status and NANU notifications within 60 minutes of delivery from the USAF.
Presently over 5500 users have subscribed to our GPS status and NANU e-mail lists.

## 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****.**

**Notes:**
We have initiated a new Tracking, Analysis, and Resolution process. Actions are designed to provide users feedback to their reports.

## 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.**

## 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.***

## 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

**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**

**Notes:**
Please feel free to contact the NAVCEN/NIS with questions, comments, suggestions, or concerns. We welcome your input. Thank You.

## 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**

## 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**

## CGSIC GPS Constellation Status

**                                    ****Thank you**

**Doug Louden**
**Chief, GPS Liaison, USCG**

**07 May 2006**