# Presentation: 544540

##  Navstar GPS Constellation Status  

**07 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**
**Empirical Clock Data**
**Constellation Health Assessment **
**Nav Coverage**
**NAVCEN and Interference Reporting Procedures **
**Constellation Performance and Summary**

**Notes:**
Talk to chart

## 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**

**Notes:**
Launch considerations......

## 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)**

**Notes:**
Here is the window of opportunity and time of day to launch IIR(M)-15 in Sep 06 into the A-plane. Notice the weather at Cape Canaveral is unstable during this time due to hurricane season. 

## 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**

**Notes:**
Look at the RED circle this represents the Eclipse time frame of mid June and July. The GREEN circle represents the recommended launch window. SVN 25 is the candidate for replacement for the IIR(M)-15. The eclipse of SVN 25 will have no impact on the IIR(M)-15 launch and replacemant.

## 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

**Notes:**
This slide gives more detail of the SVN 25 eclipse and weather delay history.

## 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**

**Notes:**
Here are the recommendations that were put forth in the Constellation Sustainment and Assessment Team meeting (CSAT). A launching date for IIR(M)-16 has not been determined yet but here are the some proposals. 

## 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.

**Notes:**
I have here a glossary of terms that help explain some terminology of the slides in this presentation. I will not use all of them but they are helpful to know as we are incorporating these processes in constellation.  

## 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 **

**Notes:**
Based on these factors of past clock performance we are monitoring these satellites very closely.  “Could be asking for a STO to get rid of this bird very very quickly” at some point

## 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)**

| SV/slot | Current Clock | Storage time for current clock (Years) | Clock operating time (Years) | Clocks remaining | Current Age of Vehicle (Years) |
| --- | --- | --- | --- | --- | --- |
| 25/A2 | Rb#1 | 13.8 | 0.2 | None | 14.0 |
| 26/F2 | Rb#1 | 5.7 | 8.0 | 1 Rb, 1 Cs | 13.6 |
| 27/A4 | Cs#4 | 12.7 | 0.8 | None | 13.5 |
| 34/D4 | Rb#1 | 4.9 | 7.4 | 1 Rb, 1 Cs | 12.3 |
| 35/B4 | Rb#1 | 12.0 | 0.5 | None | 12.5 |
| 36/C1 | Rb#1 | 10.0 | 1.9 | None | 12.0 |
| 39/A1 | Cs#4 | 12.5 | 0.2 | 1 Rb | 12.7 |

**Notes:**
Again these satellites are being “watched” closely and based on clock modeling and performance factors we have high confidence these birds are very reliable. Again this is just a snapshot.

## 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

**Notes:**
GPS locations as of 01 April 06. Notice the A2 slot where SVN 25 is located we have marked in yellow IIR(M)-15 in that slot as a future satellite. Also in yellow is SVN 37 that has now been rephased for cross plane coverage it is now located in a GLAN of 139 degrees in slot 

## 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**

**Notes:**
The constellation status health, and changes since 2005: We have 17 vehicles past their design life minus one satellite (SVN 31).
 12 past mean life estimates minus SVN 31
14 one componet away from failure minus 31 and plus one SVN this year.
Anomaly summary: We have had clock swaps on three birds this year and one has had two clock swaps.

## 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.  This was developed by and is updated by our contractor support.  

First lets go over RED, YELLOW and GREEN and Satellite status. If a satellite is RED it is NMC (non mission capable) if it is yellow (PMC) it is partial mission capable and green is full mission capable.
Now what do these really mean...I don’t know...really they are statuses of the different functions of the satellite. If a satellite is RED or NMC then the NAV payload is not functioning, if the satellite is yellow or PMC there is a loss of redundancy in one of the trhree area of NAV payload, Clocks or BUS.
Green of course is Full  mission capable.

	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 we have 29 operational satellites. % more satellites than the primary slots.

	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.  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.
SENARIO:.....Let’s say you see a NANU that says SVN 43’s is set unhealthy and later you find out the 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 (FOC).

ALSO note:  IIF satellites will have 2 Cesiums and 1 Rubidiums

## 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)**

***A-Plane Analysis***

**Notes:**
A-Plane analysis  4 satellites in the plane,  here are the particulars 
Age: 
Problem vehicles: 

## SVN 39 and 53 out

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

**UNCLASSIFIED**

**Notes:**
This slide is to show you how significant it is for coverage when we have two satellites out for a plane. Here is a post assessment from the GPSOC on PDOP (positional Dilution of Precision) from Oct 05 before SVN 53 was set healthy and after SVN 31 was decommissioned and SVN 39 was out for maintenance, also remember we had already decommissioned  SVN 31 also. Now you will notice this is averaged over a 24 hour period and the color coded legend in the bottom right give the DOP measurements. DOP is over 6 for a time over the Philippines (worst site)and the western pacific with these two satellites out.  

## 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)**

**Notes:**
Continuing with the A plane analysis; since we want to replace SVN 25 when we launch next then we should go over why we want to replace SVN 25. 

## SVN 25 and 39 Out

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

**Notes:**
This is another post assessment from the GPSOC from DEC 05 that shows two satellites that were Unusable Until Further Notice. A few days before this happened we had brought SVN 53 PRN 17 healthy so that satellite helped in this situation, but the effects here with PDOP over 6 averaged over a 24 hour period are felt over northern Africa, the Eastern coast of South America 

## 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 **

***B-Plane Analysis***

**Notes:**
B-Plane analysis Youngest in Satellite age of all the planes.

## 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**

**Notes:**
C-Plane 

## D-Plane Analysis

**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**

**Notes:**
15 will probably end up getting boosted (taken out) before it ever gets to the exp-slot position (although it’s on the way)...

## 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**

**Notes:**
Most robust of all the planes

## 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)**

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

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

**Notes:**
Satellite predicted life remaining Notice SVN 25 and SVN 24. Why not decommission SVN 24 first? Because even though it is an older satellite, SVN 25 is in worst shape and D-plane is a more robust plane than A-plane.

## 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 missing satellites between 15 and 24.  Those are all dead.  

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**

**Notes:**
Try to explain chart!!! 

## 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). |

**Notes:**
Explain chart

##  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. 

## 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**

**Notes:**
To put all of this into a summary, here are is the current status. 
Satellite decommissioned and disposed is SVN 31
SVN 30, 25 and 39 all had clock swaps and 39 had three.

## 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**

**Notes:**
Talk about chart

## CGSIC GPS Constellation Status

**                                    ****Thank you**

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

**07 May 2006**

**Notes:**
Questions?????