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: [email protected] 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