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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

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
Outline
  • Launch recommendations
  • Empirical Clock Data
  • Constellation Health Assessment
  • Nav Coverage
  • NAVCEN and Interference Reporting Procedures
  • Constellation Performance and Summary
iir m launch considerations
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
slide4

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)

slide5

IIR-15(M)

- Eclipse window

  • Recommended
  • launch window

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

slide6

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
slide7

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
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.

Glossary
empirical clock history
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
ii iia clock history primary slot vehicles 12 years old
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)

slide11

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

slide12

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

slide13

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

slide14

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)

svn 39 and 53 out
SVN 39 and 53 out

6 N 128.7 E

PDOPmax = 10.33

UNCLASSIFIED

svn 25 status
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
SVN 25 and 39 Out

64 S 95.8 E

PDOPmax = 11.65

slide18

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
c plane analysis
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

d plane analysis
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
e plane analysis
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

f plane analysis
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)

slide23

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

Decommissioned/Out-of-Service

slide24

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

accuracy equation
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)

sps ps requirements
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).
navcen data broadcasts
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.
interference reporting
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.
interference reporting process
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 process1
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.
slide31
Navigation Information Service
  • http://www.navcen.uscg.gov
  • http://www.navcenter.org (mirror site)
  • E-mail: [email protected]
  • Phone: +1 703 313 5900
  • Fax: +1 703 313 5920
slide32

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
slide33

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
CGSIC GPS Constellation Status

Thank you

Doug Louden

Chief, GPS Liaison, USCG

07 May 2006

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