List of GPS satellites explained

, 83 Global Positioning System navigation satellites have been built: 31 are launched and operational, 4 are unhealthy or in reserve, 41 are retired, 2 were lost during launch, and 1 prototype was never launched. 4 Block III satellites have completed construction and have been declared "Available For Launch" (AFL). The next launch is GPS III SV07, originally scheduled for June 2024, currently NET January 2025.

The constellation requires a minimum of 24 operational satellites, and allows for up to 32; typically, 31 are operational at any one time. A GPS receiver needs four satellites to work out its position in three dimensions.^[1]

SVNs are "space vehicle numbers" which are serial numbers assigned to each GPS satellite. PRNs are the "pseudo-random noise" sequences, or Gold codes, that each satellite transmits to differentiate itself from other satellites in the active constellation.

After being launched, GPS satellites enter a period of testing before their signals are set to "Healthy". During normal operations, certain signals may be set to "Unhealthy" to accommodate updates or testing. After decommissioning, most GPS satellites become on-orbit spares and may be recommissioned if needed. Permanently retired satellites are sent to a higher, less congested disposal orbit where their fuel is vented, batteries are intentionally depleted and communication is switched off.^[2]

Satellites

Satellites by launch date

Satellite	Launch (UTC)	Carrier rocket	Launch site	Block	No.	SVN	PRN	Slot	LOS^[3]	Status
	Remarks
OPS 5111	23:44	Atlas E/F-SGS-1	VAFB, SLC-3E	I	^[4]	01	04			^[5]
OPS 5112	10:34	Atlas E/F-SGS-1	VAFB, SLC-3E	I	^[6]	02	07
OPS 5113	00:28	Atlas E/F	VAFB, SLC-3E	I	^[7]	03	06
OPS 5114	03:59	Atlas E/F	VAFB, SLC-3E	I	^[8]	04	08
	Used for testing between February 1990 and May 1990.
OPS 5117	23:08	Atlas E/F	VAFB, SLC-3E	I	^[9]	05	05
OPS 5118	22:00	Atlas E/F	VAFB, SLC-3E	I	^[10]	06	09
N/A (Navstar 7)	01:10	Atlas E/F	VAFB, SLC-3E	I		07	10		0
	Failed to reach orbit.
	10:21	Atlas E/F	VAFB, SLC-3W	I	^[11]	08	11
USA-1	11:37	Atlas E/F	VAFB, SLC-3W	I	^[12]	09	13
	Used for testing between February 1994 and June 1994.
USA-5	21:41	Atlas E/F	VAFB, SLC-3W	I	^[13]	10	12
	Used for testing between November 1995 and March 1996.
USA-10	02:53	Atlas E/F	VAFB, SLC-3W	I	^[14]	11	03
N/A (Prototype)				II	0	12			0
	Qualification vehicle built by Rockwell International to secure Block II contract; never launched.
USA-35	18:30	Delta II 6925-9.5	CCAFS, LC-17A^[15]	II	^[16]	14	14			^[17] ^[18]
USA-38	22:30	Delta II 6925-9.5		II	^[19]	13	02	B3
USA-42	05:58	Delta II 6925-9.5	CCAFS, LC-17A	II	^[20]	16	16
USA-47	09:31	Delta II 6925-9.5	CCAFS, LC-17A	II	^[21]	19	19	A5
USA-49	18:10	Delta II 6925-9.5	CCAFS, LC-17B	II	^[22]	17	17	D3
USA-50	22:55	Delta II 6925-9.5	CCAFS, LC-17A	II	^[23]	18	18
USA-54	02:45	Delta II 6925-9.5	CCAFS, LC-17A	II	^[24]	20	20
	Decommissioned after twice changing frequency without being commanded to.
USA-63	05:39	Delta II 6925-9.5	CCAFS, LC-17A	II	^[25]	21	21	E2
USA-64	21:56	Delta II 6925-9.5	CCAFS, LC-17A	II	^[26]	15	15	D5
	Used for testing from November 2006 until March 2007
USA-66	21:39	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[27]	23	23 32	E5		^[28]
	Decommissioned from active service using PRN23 on 13 February 2004. Set usable with PRN32 on 26 February 2008.
USA-71	02:32	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[29]	24	24	D1		^[30]
USA-79	22:29	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[31]	25	25	A2
USA-80	03:20	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[32]	28	28	C2
	Retired early, replaced by USA-117.
USA-83	09:20	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[33]	26	26	F5		^[34]
USA-84	08:57	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[35]	27	27	A6		^[36] ^[37]
USA-85	23:54	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[38]	32	31 01 30 NA	F4
	PRN changed from 32 to 01 in January 1993 due to receiver problems. Decommissioned 17 March 2008 and removed from slot F4. Briefly resumed L-band transmission in 2014 but signal unusable.
USA-87	22:16	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[39]	29	29	F5		^[40]
USA-88	02:55	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[41]	22	22	B1
USA-90	03:09	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[42]	31	31	C3
USA-91	00:07	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[43]	37	07 01 24	C4		^[44]
	Switched to PRN01 in October 2008 but was unusable. Switched to PRN24 in April 2012 but was unusable.^[45]
USA-92	13:27	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[46]	39	09	A5
	First satellite to complete initial operational 24-satellite constellation.
USA-94	12:38	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[47]	35	05 30	B5
	Decommissioned from active service using PRN05 in March 2009. Resumed activity using PRN30 in August 2011.
USA-96	17:04	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[48]	34	04 18	D6		^[49] ^[50]
	Decommissioned from active service using PRN04 in November 2015.^[51] Reactivated in March 2018 using PRN18.^[52] Decommissioned from active service using PRN18 in October 2019.^[53]
USA-100	03:40	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[54]	36	06 04^[55]	C6
USA-117	00:21	Delta II 7925-9.5	CCAFS, LC-17B	IIA	^[56]	33	03	C5		^[57]
USA-126	00:50	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[58]	40	10	E6		^[59]
USA-128	08:49	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[60]	30	30	B2
GPS IIR-1	16:28	Delta II 7925-9.5	CCAFS, LC-17A	IIR		42	12		0
	Failed to reach orbit.
USA-132	03:43		CCAFS, LC-17A	IIR		43	13	F6
	Longest-serving satellite in GPS history.
USA-135	00:30	Delta II 7925-9.5	CCAFS, LC-17A	IIA	^[61]	38	08	A3		^[62]
USA-145	12:51	Delta II 7925-9.5^[63]	CCAFS, SLC-17A	IIR		46	11	D5		^[64]
USA-150	01:48	Delta II 7925-9.5^[65]	CCAFS, SLC-17A	IIR		51	20	E4
USA-151	09:17	Delta II 7925-9.5^[66]	CCAFS, SLC-17A	IIR		44	28 22	B3		^[67] ^[68] ^[69]
USA-154	17:14	Delta II 7925-9.5^[70]	CCAFS, SLC-17A	IIR		41	14 22	F5		^[71]
	Retired . Subsequently reactivated on and decommissioned again on 25 January 2023.
USA-156	07:55	Delta II 7925-9.5^[72]	CCAFS, SLC-17A	IIR		54	18	E4		^[73] ^[74]
USA-166	18:06	Delta II 7925-9.5^[75]	CCAFS, SLC-17B	IIR		56	16	B1
USA-168	22:09	Delta II 7925-9.5^[76]	CCAFS, SLC-17A	IIR		45	21	D3
USA-175	08:05	Delta II 7925-9.5^[77]	CCAFS, SLC-17A	IIR		47	22	E6		^[78]
USA-177	17:53	Delta II 7925-9.5^[79]	CCAFS, SLC-17B	IIR		59	19	C5
USA-178	22:54	Delta II 7925-9.5^[80]	CCAFS, SLC-17B	IIR		60	23	F4		^[81]
USA-180	05:39	Delta II 7925-9.5^[82]	CCAFS, SLC-17B	IIR		61	02	D1
USA-183	03:37	Delta II 7925-9.5^[83]	CCAFS, SLC-17A	IIRM		53	17	C4
	Also known as IIR-14; first to broadcast L2C signal.
USA-190	18:50	Delta II 7925-9.5^[84]	CCAFS, SLC-17A	IIRM		52	31	A2
	Also known as IIR-15.
USA-192	19:12	Delta II 7925-9.5^[85]	CCAFS, SLC-17A	IIRM		58	12	B4
	Also known as IIR-16; first satellite to complete the full operational 31-satellite constellation.
USA-196	12:23	Delta II 7925-9.5^[86]	CCAFS, SLC-17A	IIRM		55	15	F2
	Also known as IIR-17.
USA-199	20:04	Delta II 7925-9.5^[87]	CCAFS, SLC-17A	IIRM		57	29	C1
	Also known as IIR-18.
USA-201	06:10	Delta II 7925-9.5^[88]	CCAFS, SLC-17A	IIRM		48	07	A4
	Also known as IIR-19.
USA-203	08:34	Delta II 7925-9.5^[89]	CCAFS, SLC-17A	IIRM		49	01 27 30 06 NA	B6
	Also known as IIR-20; broadcasts demonstration L5 signal. Never entered service due to poor quality signal; decommissioned on 6 May 2011 but subsequently reactivated for testing. Broadcast PRN-01 before decommissioning, PRN-27 after reactivation. Shifted to PRN-30 as of 8 May 2013 and to PRN-06 as of 3 April 2014. Currently not assigned a PRN.
USA-206	10:35	Delta II 7925-9.5	CCAFS, SLC-17A	IIRM		50	05	E3
	Originally scheduled for launch in 1999 as IIR-3 but damaged during processing.^[90] Also known as IIR-21; L5 services disconnected from J2 port before launch. Final Delta II launch with a United States Air Force payload,^[91] final launch from SLC-17A, and final Delta II 7925.
USA-213	03:00	Delta IV M+ (4,2)	CCAFS, SLC-37B	IIF		62	25	B2
	First to broadcast operational L5 signal.
USA-232	06:41	Delta IV M+(4,2)	CCAFS, SLC-37B	IIF		63	01	D2		^[92] ^[93]
USA-239	12:10	Delta IV M+(4,2)	CCAFS, SLC-37B	IIF		65	24	A1
USA-242	21:38	Atlas V 401	CCAFS, SLC-41	IIF		66	27	C2
USA-248	01:59	Delta IV M+ (4,2)	CCAFS, SLC-37B	IIF		64	30	A3
USA-251	00:03	Delta IV M+ (4,2)	CCAFS, SLC-37B	IIF		67	06	D4
USA-256	03:23	Atlas V 401	CCAFS, SLC-41	IIF		68	09	F3
USA-258	17:21	Atlas V 401	CCAFS, SLC-41	IIF		69	03	E1
USA-260	18:36	Delta IV M+ (4,2)	CCAFS, SLC-37B	IIF		71	26	B5
USA-262	15:36	Atlas V 401	CCAFS, SLC-41	IIF		72	08	C3
USA-265	16:13	Atlas V 401	CCAFS, SLC-41	IIF		73	10	E2		^[94]
USA-266	13:38	Atlas V 401	CCAFS, SLC-41	IIF		70	32	F1		^[95]
USA-289 Vespucci^[96]	13:51	Falcon 9 Block 5	CCAFS, SLC-40	III		74	04	F4		^[97]
USA-293 Magellan	13:06	Delta IV M+ (4,2)	CCAFS, SLC-37B	III		75	18	D6		^[98]
USA-304 Matthew Henson	20:10:46	Falcon 9 Block 5	CCAFS, SLC-40	III		76	23	E5
	Initially nicknamed Columbus.^[99] ^[100]
USA-309 Sacagawea	23:24:23	Falcon 9 Block 5	CCAFS, SLC-40	III		77	14	B6
USA-319 Neil Armstrong	16:09^[101]	Falcon 9 Block 5^[102]	CCSFS, SLC-40^[103]	III	5	78	11	D5
USA-343 Amelia Earhart	12:24	Falcon 9 Block 5	CCSFS, SLC-40	III	6	79	28	A6

Satellites by block

Block	Launched	Operational	Testing/ Reserve	Unhealthy/ Spare	Retired	Launch Failures	Manufacturer	Remarks
Block I	11	0	0	0	10	1	Rockwell International
Block II	9	0	0	0	9	0	Rockwell International	One unlaunched prototype
Block IIA	19	0	0	0	19	0	Rockwell International
Block IIR	13	7	0	2	3	1	Lockheed Martin
Block IIRM	8	7	0	1	0	0	Lockheed Martin
Block IIF	12	11	0	0	1	0	Boeing
Block III	6	6	0	0	0	0	Lockheed Martin
Block IIIF	0	0	0	0	0	0	Lockheed Martin
Total	78	31	0	3	42	2

Orbital slots (by SVN)

Refer to GPS Constellation Status for the most up-to-date information.

Block	IIR	IIRM	IIF	III

Numbers in parentheses refer to non-operational satellites.

Once launched, GPS satellites do not change their plane assignment but slot assignments are somewhat arbitrary and are subject to change.

PRN status by satellite block

, 31 of 32 PRNs are in use; PRN 01 is unassigned. Two additional satellites are designated as on-orbit spares.

PRN	01	02	03	04	05	06	07	08	09	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	--
IIR		O									S		O			O		S	O	O	O	O
IIRM					O		O					O			O		O												O		O		S
IIF	R		O			O		O	O	O														O	O	O	O			O		O
III				O							O			O				O					O					O

PRN to SVN history

This section is for the purpose of making it possible to determine the PRN associated with a SVN at a particular epoch. For example, SVN 049 had been assigned PRNs 01, 24, 27, and 30 at different times of its lifespan, whereas PRN 01 had been assigned to SVNs 032, 037, 049, 035, and 063 at different epochs. This information can be found in the IGS ANTEX [ftp://igs.org/pub/station/general/igs14.atx file], which uses the convention "GNN" and "GNNN" for PRNs and SVNs, respectively. For example, SVN 049 is described as:

BLOCK IIR-M         G01                 G049      2009-014A TYPE / SERIAL NO    
  2009     3    24     0     0    0.0000000                 VALID FROM          
  2011     5     6    23    59   59.9999999                 VALID UNTIL         
BLOCK IIR-M         G24                 G049      2009-014A TYPE / SERIAL NO    
  2012     2     2     0     0    0.0000000                 VALID FROM          
  2012     3    14    23    59   59.9999999                 VALID UNTIL         
BLOCK IIR-M         G24                 G049      2009-014A TYPE / SERIAL NO    
  2012     8     9     0     0    0.0000000                 VALID FROM          
  2012     8    22    23    59   59.9999999                 VALID UNTIL         
BLOCK IIR-M         G27                 G049      2009-014A TYPE / SERIAL NO    
  2012    10    18     0     0    0.0000000                 VALID FROM          
  2013     5     9    23    59   59.9999999                 VALID UNTIL         
BLOCK IIR-M         G30                 G049      2009-014A TYPE / SERIAL NO    
  2013     5    10     0     0    0.0000000                 VALID FROM          

whereas for PRN 01 the following excerpt is relevant:

BLOCK IIA           G01                 G032      1992-079A TYPE / SERIAL NO    
  1992    11    22     0     0    0.0000000                 VALID FROM          
  2008    10    16    23    59   59.9999999                 VALID UNTIL         
BLOCK IIA           G01                 G037      1993-032A TYPE / SERIAL NO    
  2008    10    23     0     0    0.0000000                 VALID FROM          
  2009     1     6    23    59   59.9999999                 VALID UNTIL         
BLOCK IIR-M         G01                 G049      2009-014A TYPE / SERIAL NO    
  2009     3    24     0     0    0.0000000                 VALID FROM          
  2011     5     6    23    59   59.9999999                 VALID UNTIL         
BLOCK IIA           G01                 G035      1993-054A TYPE / SERIAL NO    
  2011     6     2     0     0    0.0000000                 VALID FROM          
  2011     7    12    23    59   59.9999999                 VALID UNTIL         
BLOCK IIF           G01                 G063      2011-036A TYPE / SERIAL NO    
  2011     7    16     0     0    0.0000000                 VALID FROM          

A table extracted out of the ANTEX file is made available by the Bernese GNSS Software.

Planned launches

Block III

See main article: article and GPS Block III.

Date	Rocket	Launch site	Satellite	SVN	Remarks
TBD 2025	Vulcan Centaur	CCSFS SLC-41	GPS III SV07 Sally Ride	80	Space vehicle manufacturing contract awarded February 2013.^[104] It was in assembly in December 2018.^[105] Declared "Available for Launch" on 20 May 2021.^[106] ^[107]
TBD 2025^[108] ^[109] ^[110]	Vulcan Centaur	CCSFS SLC-41	GPS III SV08 Katherine Johnson	81	Space vehicle manufacturing contract awarded February 2013. The satellite was named "Katherine Johnson" in June 2020 following its successful core mate assembly.^[111] Declared "Available for Launch" on 10 June 2021.
End of 2025	Vulcan Centaur	CCSFS SLC-41	GPS III SV09 Ellison Onizuka	82	Space vehicle manufacturing contract awarded September 2016.^[112] Declared "Available for Launch" on 23 Aug 2022.^[113]
2026^[114]	Falcon 9 Block 5	CCSFS, SLC-40	GPS III SV10 Hedy Lamarr	83	Space vehicle manufacturing contract awarded September 2016. Component build up stage as of June 2021.^[115] Component deliveries continuing through May 2022.^[116] Declared "Available for Launch" on 08 Dec 2022.^[117]

Block IIIF

See main article: article and GPS Block IIIF.

Projected Available For Launch (AFL) Date	Rocket	Launch site	Satellite	SVN	Remarks
Nov 2026^[118] ^[119]	Falcon Heavy	KSC, LC-39A	GPS IIIF SV11		Construction contract awarded in September 2018. In production.
Apr 2027			GPS IIIF SV12		In production.
Mar 2028			GPS IIIF SV13
April 2027^[120]			GPS IIIF SV14
Oct 2027			GPS IIIF SV15
Jun 2029			GPS IIIF SV16
June 2028			GPS IIIF SV17		Technology Insertion Point
Oct 2028			GPS IIIF SV18
Feb 2029			GPS IIIF SV19
June 2029			GPS IIIF SV20
FY2029^[121]			GPS IIIF SV21
Oct 2032			GPS IIIF SV22
FY2030			GPS IIIF SV23		Technology Insertion Point
			GPS IIIF SV24
FY2031			GPS IIIF SV25
			GPS IIIF SV26
FY2032			GPS IIIF SV27
			GPS IIIF SV28
FY2033			GPS IIIF SV29		Technology Insertion Point
			GPS IIIF SV30
FY2034			GPS IIIF SV31
			GPS IIIF SV32

See also

• List of BeiDou satellites
• List of Galileo satellites
• List of GLONASS satellites
• List of NAVIC satellites

External links

• Boeing Delta launch schedule
• United States military launch record
• NAVCEN GPS Constellation
• NIMA GPS Constellation Status
• UNB GPS Constellation Status
• [ftp://ftp.agi.com/pub/Catalog/Almanacs/SEM/GPSData.txt AGI-CSSI GPS Constellation Status]

Notes and References

1. Web site: US Government. GPS.gov. gps.gov. U.S. Government. 21 March 2015.
2. Web site: 17 April 2020. 2 SOPS disposes last GPS IIA satellite after 26 years. 7 July 2021. GPS World. en-US.
3. Length Of Service in days. Includes testing period(s).
4. Web site: Navstar 1. NASA. 21 November 2020.
5. Web site: [ftp://tycho.usno.navy.mil/pub/gps/gpsb1.txt USNO Block 1 Satellite Information]. 28 June 2015.
6. Web site: Navstar 2. NASA. 21 November 2020.
7. Web site: Navstar 3. NASA. 21 November 2020.
8. Web site: Navstar 4. NASA. 21 November 2020.
9. Web site: Navstar 5. NASA. 24 April 2013.
10. Web site: Navstar 6. NASA. 24 April 2013.
11. Web site: Navstar 8. NASA. 25 April 2013.
12. Web site: Navstar 9. NASA. 25 April 2013.
13. Web site: Navstar 10. NASA. 25 April 2013.
14. Web site: Navstar 11. NASA. 25 April 2013.
15. Encyclopedia: Delta 6925. Mark. Wade . Encyclopedia Astronautica. 25 April 2013. dead. https://web.archive.org/web/20130522122554/http://www.astronautix.com/lvs/dela6925.htm. 22 May 2013.
16. Web site: Navstar II-1. NASA. 25 April 2013.
17. Web site: NAVSTAR GPS II-1 - Summary. Space and Tech. 10 July 2012. dead . https://web.archive.org/web/20111212055828/http://www.spaceandtech.com/spacedata/logs/1989/1989-013a_gps-2-1_sumpub.shtml. 12 December 2011.
18. Web site: [ftp://tycho.usno.navy.mil/pub/gps/gpsb2.txt USNO Block 2 Satellite Information]. 28 June 2015.
19. Web site: Navstar II-2. NASA. 25 April 2013.
20. Web site: Navstar II-3. NASA. 25 April 2013.
21. Web site: Navstar II-4. NASA. 25 April 2013.
22. Web site: Navstar II-5. NASA. 25 April 2013.
23. Web site: Navstar II-6. NASA. 25 April 2013.
24. Web site: Navstar II-7. NASA. 25 April 2013.
25. Web site: Navstar II-8. NASA. 25 April 2013.
26. Web site: Navstar II-9. NASA. 25 April 2013.
27. Web site: Navstar 2A-01. NASA. 25 April 2013.
28. Web site: Notice Advisory To NAVSTAR Users (NANU) 2016008. U.S. Coast Guard Navigation Center. 26 January 2016.
29. Web site: Navstar 2A-02. NASA. 25 April 2013.
30. Web site: NANU 2011088. 4 November 2011. dead . https://web.archive.org/web/20130408132218/https://gps.afspc.af.mil/gps/archive/2011/NANUS/2011088.nnu. 8 April 2013.
31. Web site: Navstar 2A-03. NASA. 25 April 2013.
32. Web site: Navstar 2A-04. NASA. 25 April 2013.
33. Web site: Navstar IIA-05. NASA. 25 April 2013.
34. Web site: NANU 20150106. 7 January 2015.
35. Web site: Navstar IIA-06. NASA. 25 April 2013.
36. Web site: Navigation Center . United States Coast Guard . 17 June 2021.
37. Web site: NAVSTAR GPS Constellation Status . University of New Brunswick. 4 December 2015. 14 April 2016.
38. Web site: Navstar IIA-07. NASA. 25 April 2013.
39. Web site: Navstar IIA-08. NASA. 25 April 2013.
40. Web site: 2007144 NANU. 28 July 2015.
41. Web site: Navstar IIA-09. NASA. 25 April 2013.
42. Web site: Navstar IIA-10. NASA. 25 April 2013.
43. Web site: Navstar IIA-11. NASA. 25 April 2013.
44. Web site: Ray . Justin . Two GPS navigation birds retired after two decades in space . Spaceflight Now . Pole Star Publications Ltd . 29 April 2021 . 31 March 2016.
45. Web site: [ftp://tycho.usno.navy.mil/pub/gps/gpsnanu2012.txt Archive of 2012 NANU Messages]. USNO. 28 June 2015.
46. Web site: Navstar IIA-12. NASA. 25 April 2013.
47. Web site: Navstar IIA-13. NASA. 25 April 2013.
48. Web site: Navstar IIA-14. NASA. 25 April 2013.
49. Web site: Notice Advisory to GPS Users. navcen.uscg.gov. 28 October 2019.
50. Web site: 15 April 2020. Farewell to a Great Generation: GPS IIA. 18 June 2021. Inside GNSS – Global Navigation Satellite Systems Engineering, Policy, and Design. en-US.
51. Web site: NANU2015091 . Celestrak. 23 March 2018.
52. Web site: NANU2018015 . Celestrak. 23 March 2018.
53. Web site: Notice Advisory to GPS Users. navcen.uscg.gov. 28 October 2019.
54. Web site: Navstar IIA-15. NASA. 25 April 2013.
55. Web site: NANU2019104. celestrak.com. 26 July 2019.
56. Web site: Navstar IIA-16. NASA. 25 April 2013.
57. Web site: NANU 2014-063. 28 June 2015.
58. Web site: Navstar IIA-17. NASA. 25 April 2013.
59. Web site: Two GPS navigation birds retired after two decades in space – Spaceflight Now.
60. Web site: Navstar IIA-18. NASA. 25 April 2013.
61. Web site: Navstar 38. NASA. 26 April 2013.
62. Web site: 2nd Space Operations Squadron decommissions 22-year-old satellite. 18 June 2021. Air Force Space Command (Archived). en-US.
63. Web site: Navstar 46. NASA. 26 April 2013.
64. Web site: CelesTrak Orbit Visualization.
65. Web site: Navstar 47. NASA. 26 April 2013.
66. Web site: Navstar 48. NASA. 26 April 2013.
67. NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2021035SUBJ: SVN44 (PRN28) DECOMMISSIONING
68. Web site: CelesTrak Orbit Visualization.
69. Web site: CGSIC Bulletin: GPS Constellation Change: SVN-63 . 10 August 2023 .
70. Web site: Navstar 49. NASA. 26 April 2013.
71. Web site: NANU2023006. Celestrak. 15 January 2023. 18 February 2023.
72. Web site: Navstar 50. NASA. 26 April 2013.
73. Web site: NANU2018009. 6 March 2018.
74. Web site: CelesTrak Orbit Visualization.
75. Web site: Navstar 51. NASA. 26 April 2013.
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