HONOR-RESPECT-DEVOTION TO DUTY

1UNCLASSIFIED

Navstar GPS Navstar GPS Constellation StatusConstellation Status

07 May 2006

Doug LoudenChief, GPS Liaison, USCGHQ AF Space Command

GPSOC, Civil AnalystColorado Springs, CO.

Peterson AFB (719) 554-3582Schriever AFB (719) 567-5093

CGSIC

2UNCLASSIFIED

Outline

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

3UNCLASSIFIED

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

4UNCLASSIFIED

0:001:002:003:004:005:006:007:008:009:00

10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:000:00

240 260 280 300

Gre

enw

ich

Mea

n T

ime,

hr.

UNSTABLE WEATHER

AT LAUNCH SITE

10 20 31

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

10 20 31 10 20 28 10 20 31 10 20 30 10 20 31 10 20 30 10 20 31 10 20 3110 20 3010 20 3110 20 30

0 20 40 60 80 100 120 140 160 180 200 220 320 340 360

UNSTABLE WEATHER AT LAUNCH SITE

0:001:002:003:004:005:006:007:008:009:00

10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:000:00

240 260 280 300

Gre

enw

ich

Mea

n T

ime,

hr.

UNSTABLE WEATHER

AT LAUNCH SITE

10 20 31

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

10 20 31 10 20 28 10 20 31 10 20 30 10 20 31 10 20 30 10 20 31 10 20 3110 20 3010 20 3110 20 30

0 20 40 60 80 100 120 140 160 180 200 220 320 340 360

UNSTABLE WEATHER AT LAUNCH SITE

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)

5UNCLASSIFIED

- Eclipse window

-Recommended launch window

IIR-15(M)

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

6UNCLASSIFIED

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

7UNCLASSIFIED

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

8UNCLASSIFIED

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.

9UNCLASSIFIED

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

10UNCLASSIFIED

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/slotCurrent Clock

Storage time for current clock

(Years)

Clock operating time

(Years)Clocks

remainingCurrent 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

11UNCLASSIFIED

Block II

Block IIA

Block IIR

A CB ED F

80

100

120

160

180

0

20

40

60

GLAN(deg)

E2

A3

A1

A2

A4B3

B4

B2

B1

C1

C2C3

C4 D1

D2

D3

D4

E1

E3

E4F1

F2

F3

F438

27

25

39 30

56

44

35

36

3359

37

34

61

45

46

40

54

60

43

26

41

15

29

51

Empty Slot47

53

32

24

GPS Locations 1 Apr 06(GLAN)

IIR-15(M)

Block IIR-M

Rephase1 deg day drift

14037 in April

12UNCLASSIFIED

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

Constellation Status Health

Changes Since Last Year

Total SVs in Category

SVN 31 disposal 15 Dec 05SVN 25 last clock

13UNCLASSIFIED

MLE: II= 12.05 IIA= 13.03 IIR= 14.18 IIR-M=8.60 yrsMMD: IIF= 11.0yrs

Constellation Assessment

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

As Of 1 Apr 06

Design Life:II/IIA - 7.5 yrsIIR - 10 yrsIIF - 15 yrs

SVN 00

PRN 00

BU

S

NA

V

Clo

cks

RubidiumCesium

1 23 4

GoodDeadSuspectUnused

Clock Status =

IIRs : only 3 Rb clocks

SVNPRN

A B C D E F

SVN36PRN06

SVN 51PRN 20

SVN 32PRN 01

SVN 25PRN 25

SVN 27PRN 27

SVN 53PRN 17

SVN 30PRN 30

SVN 35PRN 05

SVN 33PRN 03

SVN 37PRN 07

SVN 46PRN 11

SVN 34PRN 04

SVN 40 PRN 10

SVN 54PRN 18

SVN 26PRN 26

M

SVN 38PRN 08

SVNPRN

SVN 44 PRN 28

SVN 39PRN 09

SVN 15 PRN 15

SVNPRN

SVN 56 PRN 16

SVN PRN

SVN 45 PRN 21

SVNPRN

SVN 60 PRN 23

1

2

3

4

SVN 43PRN 13

SVN 41 PRN 14

SVN 29PRN 29

SVNPRN

SVN 24PRN 24

SVN 47PRN 22

SVN 59 PRN 19

SVN 61PRN 02

SVNPRN

Vehicle count: 29 total1 IIs 15 IIAs 13 IIRs (includes 1st IIR-M)

14UNCLASSIFIED

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)

SVN 25

SVN 38

SVN 27

A

y y

SVN 39

y

g

y

g g

y

BU

S

NA

V

SVN

A-Plane Analysis

15

SVN 39 and 53 out

6 N 128.7 EPDOPmax = 10.33

UNCLASSIFIED

16UNCLASSIFIED

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)

17UNCLASSIFIED

SVN 25 and 39 Out

64 S 95.8 EPDOPmax = 11.65

18UNCLASSIFIED

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

BU

S

NA

V

SVN

BSVN 56

SVN 44

SVN 35

y

g

g

y

SVN 30

g

g

g

y

B-Plane Analysis

19UNCLASSIFIED

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

BU

S

NA

V

SVN

y

CSVN 36

SVN 33

SVN 59g

g

g

g

gSVN 53g

g

SVN 37y y

SVN37 on station as of Mid April

20UNCLASSIFIED

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

BU

S

NA

V

SVN

y y

y

g

DSVN 61g

g y

y

SVN 46

SVN 45

SVN 15

g

gSVN 34

SVN 24y y

21UNCLASSIFIED

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

BU

S

NA

V

SVN

SVN 40

g

g

SVN 51g

SVN 47

g

g

E

SVN 54g

g y

22UNCLASSIFIED

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)

BU

S

NA

V

SVN

SVN 41

SVN 43

g

y

g

ySVN 26

F

gg

g

g

g

ySVN 29

SVN 32g y

SVN 60

23UNCLASSIFIED

Mar-06

Mar-07

Mar-08

Mar-09

Mar-10

Mar-11

Mar-12

Mar-13

Mar-14

Mar-15

Mar-16

Mar-17

Mar-18

Mar-19

Mar-20

Mar-21

Mar-22

Mar-23

SVN26SVN29SVN32SVN43SVN41SVN60SVN23SVN40SVN51SVN54SVN47SVN15SVN24SVN34SVN46SVN45SVN61SVN37SVN36SVN33SVN53SVN59SVN35SVN30SVN44SVN56SVN25SVN27SVN39SVN38

Time as of March 2006

1.0 > Reliability >.75

.75 > Reliability >.50

.50 > Reliability >.25A

B

C

D

E

FReliability = 0.75 0.50 0.25

Mar-06

Mar-07

Mar-08

Mar-09

Mar-10

Mar-11

Mar-12

Mar-13

Mar-14

Mar-15

Mar-16

Mar-17

Mar-18

Mar-19

Mar-20

Mar-21

Mar-22

Mar-23

SVN26SVN29SVN32SVN43SVN41SVN60SVN23SVN40SVN51SVN54SVN47SVN15SVN24SVN34SVN46SVN45SVN61SVN37SVN36SVN33SVN53SVN59SVN35SVN30SVN44SVN56SVN25SVN27SVN39SVN38

Time as of March 2006

1.0 > Reliability >.75

.75 > Reliability >.50

.50 > Reliability >.25A

B

C

D

E

FReliability = 0.75 0.50 0.25Reliability = 0.75 0.50 0.25

Decommissioned/Out-of-Service

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

24UNCLASSIFIED

Blk II

Blk IIA

Blk IIR

Deactivated

Satellite Vehicle

Blk IIR-M

Yea

rs

24 25 28 26 27 32 29 37 39 35 34 36 33 40 30 4338 46 5115 44 41 54 56 45 47 59 60 61 53

2

4

6

8

10

Block IIR MLEBlock II & IIA MLE

12

14

Blo

ck I

IR-M

ML

E

(as of: 1 Apr 06)16

Ope

rati

onal

for

4.5

yrs

– U

sed

for

Tes

t &

Che

ckou

t

GPS Satellite Age

Design Life:II/IIA - 7.5 yrsIIR - 10 yrsIIRM - 8.5 yrsIIF - 15 yrs

25UNCLASSIFIED

Accuracy Equation

Good DOP Poor HDOP Poor VDOP

Accuracy = Statistical Conversion * DOP * URE2 + UEE2

~68% (~DRMS)

UEE

NavMessage

~95% (~2DRMS)

50% (CEP) GA MCS MS

Good Moderate Poor

0 1 2 3 4 5 6

DOP

TrueRange

Accuracy; DOP is a big part of the accuracy equation

URE

26UNCLASSIFIED

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).

27UNCLASSIFIED

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.

1. 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.

2. 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.

3. CGSIC List server: This service provides the subscriber with an e-mail containing GPS and CGSIC announcements.

28UNCLASSIFIED

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.

29UNCLASSIFIED

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.

30UNCLASSIFIED

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.

31UNCLASSIFIED

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

32UNCLASSIFIED

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

33UNCLASSIFIED

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

34UNCLASSIFIED

CGSIC GPS Constellation Status

Thank you

Doug LoudenChief, GPS Liaison, USCG

07 May 2006