Jump to content

List of GPS satellites

From Wikipedia, the free encyclopedia

Samples of three GPS satellites' orbits over a five-year period (2013 to 2018)
  USA-242 ·   USA-239 ·   USA-151 ·   Earth

As of 19 December 2024, 83 Global Positioning System navigation satellites have been built: 30 are launched and operational, 1 is launched and undergoing the commissioning process, 3 are in reserve or testing, 43 are retired, 2 were lost during launch, and 1 prototype was never launched. 3 Block III satellites have completed construction and have been declared "Available For Launch" (AFL). The next launch is GPS III SV08, currently targeted for 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

[edit]

Satellites by launch date

[edit]
  1. ^ Length Of Service in days. Includes testing period(s).

Satellites by block

[edit]
Block Launched Operational Testing/
Reserve
Unhealthy 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 6 2 0 4 1 Lockheed Martin
Block IIRM 8 7 1 0 0 0 Lockheed Martin
Block IIF 12 11 0 0 1 0 Boeing
Block III 7 6 1 0 0 0 Lockheed Martin
Block IIIF 0 0 0 0 0 0 Lockheed Martin
Total 79 30 4 0 43 2
As of 19 December 2024

Orbital slots (by SVN)

[edit]

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

As of 10 August 2023
Slot Plane
A B C D E F
1 65 56 57 61 69 70
2 52 62 66 80 73 55
3 64 72 45 50 68
4 48 58 53 67 51 74
5 71 59 78 76
6 79 77 75 43
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

[edit]

As of 23 August 2023, 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 R
IIRM O O O O O O O S
IIF R O O O O O O O O O O O
III T O O O O O O
Legend:
  • O – Operational
  • T – Testing in preparation for operation
  • S – On orbit Spare
  • U – Unhealthy and unusable
  • R – Retired

PRN to SVN history

[edit]

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 file[permanent dead link], 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

[edit]

Block III

[edit]
Date Rocket Launch site Satellite SVN Remarks
TBD 2025[110][111][112] Vulcan Centaur VC2S CCSFS SLC-41 GPS III SV08 Katherine Johnson 81 Space vehicle manufacturing contract awarded February 2013.[113] The satellite was named "Katherine Johnson" in June 2020 following its successful core mate assembly.[114]

Declared "Available for Launch" on 10 June 2021.[115]

End of 2025[116] Vulcan Centaur VC2S CCSFS SLC-41 GPS III SV09 Ellison Onizuka 82 Space vehicle manufacturing contract awarded September 2016.[117]

Declared "Available for Launch" on 23 Aug 2022.[116]

2026[118] Falcon 9 Block 5 CCSFS, SLC-40 GPS III SV10 Hedy Lamarr 83 Space vehicle manufacturing contract awarded September 2016.[117] Component build up stage as of June 2021.[119] Component deliveries continuing through May 2022.[120]

Declared "Available for Launch" on 08 Dec 2022.[121]

Block IIIF

[edit]

See also

[edit]

References

[edit]
  1. ^ US Government. "GPS.gov". gps.gov. U.S. Government. Retrieved 21 March 2015. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ "2 SOPS disposes last GPS IIA satellite after 26 years". GPS World. 17 April 2020. Retrieved 7 July 2021.
  3. ^ "Navstar 1". NASA. Retrieved 21 November 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  4. ^ a b c d e f g h i j k l m n "USNO Block 1 Satellite Information". Retrieved 28 June 2015.[permanent dead link] Public Domain This article incorporates text from this source, which is in the public domain.
  5. ^ "Navstar 2". NASA. Retrieved 21 November 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  6. ^ "Navstar 3". NASA. Retrieved 21 November 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  7. ^ "Navstar 4". NASA. Retrieved 21 November 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  8. ^ "Navstar 5". NASA. Retrieved 24 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  9. ^ "Navstar 6". NASA. Retrieved 24 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  10. ^ "Navstar 8". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  11. ^ "Navstar 9". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  12. ^ "Navstar 10". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  13. ^ "Navstar 11". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  14. ^ a b c d e f g h i Wade, Mark. "Delta 6925". Encyclopedia Astronautica. Archived from the original on 22 May 2013. Retrieved 25 April 2013.
  15. ^ "Navstar II-1". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  16. ^ "NAVSTAR GPS II-1 - Summary". Space and Tech. Archived from the original on 12 December 2011. Retrieved 10 July 2012.
  17. ^ a b c d e f g h i j k l m n o p q "USNO Block 2 Satellite Information". Retrieved 28 June 2015.[permanent dead link] Public Domain This article incorporates text from this source, which is in the public domain.
  18. ^ "Navstar II-2". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  19. ^ "Navstar II-3". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  20. ^ "Navstar II-4". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  21. ^ "Navstar II-5". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  22. ^ "Navstar II-6". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  23. ^ "Navstar II-7". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  24. ^ "Navstar II-8". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  25. ^ "Navstar II-9". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  26. ^ "Navstar 2A-01". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  27. ^ "Notice Advisory To NAVSTAR Users (NANU) 2016008". U.S. Coast Guard Navigation Center. Retrieved 26 January 2016. Public Domain This article incorporates text from this source, which is in the public domain.
  28. ^ "Navstar 2A-02". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  29. ^ "NANU 2011088". Archived from the original on 8 April 2013. Retrieved 4 November 2011. Public Domain This article incorporates text from this source, which is in the public domain.
  30. ^ "Navstar 2A-03". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  31. ^ "Navstar 2A-04". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  32. ^ "Navstar IIA-05". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  33. ^ "NANU 20150106". Retrieved 7 January 2015. Public Domain This article incorporates text from this source, which is in the public domain.
  34. ^ "Navstar IIA-06". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  35. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af "Navigation Center". United States Coast Guard. Retrieved 17 June 2021.
  36. ^ a b "NAVSTAR GPS Constellation Status". University of New Brunswick. 4 December 2015. Retrieved 14 April 2016.
  37. ^ "Navstar IIA-07". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  38. ^ "Navstar IIA-08". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  39. ^ "2007144 NANU". Retrieved 28 July 2015.
  40. ^ "Navstar IIA-09". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  41. ^ "Navstar IIA-10". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  42. ^ "Navstar IIA-11". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  43. ^ Ray, Justin (31 March 2016). "Two GPS navigation birds retired after two decades in space". Spaceflight Now. Pole Star Publications Ltd. Retrieved 29 April 2021.
  44. ^ "Archive of 2012 NANU Messages". USNO. Retrieved 28 June 2015.[permanent dead link] Public Domain This article incorporates text from this source, which is in the public domain.
  45. ^ "Navstar IIA-12". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  46. ^ "Navstar IIA-13". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  47. ^ "Navstar IIA-14". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  48. ^ "Notice Advisory to GPS Users". navcen.uscg.gov. Retrieved 28 October 2019. Public Domain This article incorporates text from this source, which is in the public domain.
  49. ^ "Farewell to a Great Generation: GPS IIA". Inside GNSS – Global Navigation Satellite Systems Engineering, Policy, and Design. 15 April 2020. Retrieved 18 June 2021.
  50. ^ "NANU2015091". Celestrak. Retrieved 23 March 2018.
  51. ^ "NANU2018015". Celestrak. Retrieved 23 March 2018.
  52. ^ "Notice Advisory to GPS Users". navcen.uscg.gov. Retrieved 28 October 2019. Public Domain This article incorporates text from this source, which is in the public domain.
  53. ^ "Navstar IIA-15". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  54. ^ "NANU2019104". celestrak.com. Retrieved 26 July 2019.
  55. ^ "Navstar IIA-16". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  56. ^ "NANU 2014-063". Retrieved 28 June 2015.
  57. ^ "Navstar IIA-17". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  58. ^ "Two GPS navigation birds retired after two decades in space – Spaceflight Now".
  59. ^ "Navstar IIA-18". NASA. Retrieved 25 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  60. ^ "Navstar 43". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  61. ^ "Navstar 38". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  62. ^ "2nd Space Operations Squadron decommissions 22-year-old satellite". Air Force Space Command (Archived). Retrieved 18 June 2021.
  63. ^ "Navstar 46". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  64. ^ "CelesTrak Orbit Visualization".
  65. ^ "Navstar 47". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  66. ^ "Navstar 48". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  67. ^ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2021035 SUBJ: SVN44 (PRN28) DECOMMISSIONING
  68. ^ "CelesTrak Orbit Visualization".
  69. ^ "CGSIC Bulletin: GPS Constellation Change: SVN-63". 10 August 2023.
  70. ^ NOTICE ADVISORY TO NAVSTAR USERS (NANU) 2024067 SUBJ: SVN44 (PRN22) DECOMMISSIONING 19 DEC 2024
  71. ^ "Navstar 49". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  72. ^ "NANU2023006". Celestrak. 15 January 2023. Retrieved 18 February 2023.
  73. ^ "Navstar 50". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  74. ^ "NANU2018009". Retrieved 6 March 2018.
  75. ^ "CelesTrak Orbit Visualization".
  76. ^ "Navstar 51". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  77. ^ "Navstar 52". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  78. ^ "Navstar 53". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  79. ^ "Notice Advisory to NAVStar Users". 17 January 2022.
  80. ^ "Navstar 54". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  81. ^ "Navstar 55". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  82. ^ "GPS constellation changes with addition of second GPS III satellite". 2 April 2020.
  83. ^ "Navstar 56". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  84. ^ "Navstar 57". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  85. ^ "GPS 2R-15". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  86. ^ "Navstar 59". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  87. ^ "GPS 2R-17". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  88. ^ "GPS 2R-18". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  89. ^ "Navstar 62". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  90. ^ "Navstar 62". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  91. ^ Harland, David (31 May 2005). Space Systems Failures: Disasters and Rescues of Satellites, Rocket and Space Probes (2005th ed.). Praxis. p. 325. ISBN 978-0387215198.
  92. ^ "Navstar 63". NASA. Retrieved 26 April 2013. Public Domain This article incorporates text from this source, which is in the public domain.
  93. ^ "NANU 2023-004". Retrieved 12 November 2023. Public Domain This article incorporates text from this source, which is in the public domain.
  94. ^ "CGSIC Bulletin: GPS Constellation Change: SVN-63". 10 August 2023.
  95. ^ "NANU 2015-093". Retrieved 10 December 2015. Public Domain This article incorporates text from this source, which is in the public domain.
  96. ^ "NANU 2016-011". Retrieved 9 March 2016. Public Domain This article incorporates text from this source, which is in the public domain.
  97. ^ Clark, Stephen (23 December 2018). "SpaceX closes out year with successful GPS satellite launch". Spaceflight Now. Retrieved 24 December 2018.
  98. ^ "NANU 2020-004". Retrieved 13 January 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  99. ^ "NANU 2020-015". Retrieved 2 April 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  100. ^ "NANU 2020-046". USCG Navigation Center. Retrieved 23 November 2020.
  101. ^ Clark, Stephen (2 October 2020). "Space Force announces new nicknames for GPS satellites". Spaceflight Now. Retrieved 2 October 2020.
  102. ^ https://www.losangeles.af.mil/News/Article-Display/Article/2082387/gps-iii-space-vehicle-03-safely-arrives-in-florida/ Public Domain This article incorporates text from this source, which is in the public domain.
  103. ^ "NANU 2020-086". USCG Navigation Center. Retrieved 2 December 2020.
  104. ^ "Fifth GPS III Satellite Takes to the Skies". Lockheed Martin. Retrieved 17 June 2021.
  105. ^ "Air Force Awards Launch Services Contracts to SpaceX and ULA". losangeles.af.mil. US Air Force Space and Missile Command Public Affairs. 14 March 2018. Retrieved 16 March 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  106. ^ Clark, Stephen. "Five launches planned from Florida's Space Coast in June – Spaceflight Now". Retrieved 29 May 2021.
  107. ^ "NANU 2022-025". USCG Navigation Center. Retrieved 25 May 2022.
  108. ^ "NANU 2023-013". USCG Navigation Center. Retrieved 26 February 2023.
  109. ^ Erwin, Sandra (16 December 2024). "SpaceX launches U.S. Space Force 'rapid response' GPS mission". SpaceNews. Retrieved 20 December 2024.
  110. ^ "GPS MODERNIZATION: Space Force Should Reassess Requirements for Satellites and Handheld Devices" (PDF). 5 June 2023. Space Force is projected to launch the 27th M-code capable GPS satellite in February 2025.
  111. ^ "Department of Defense Fiscal Year (FY) 2024 Budget Estimates" (PDF). March 2023.
  112. ^ "Space Force assigns 12 national security missions to SpaceX and ULA". 8 June 2023.
  113. ^ "Air Force Awards Lockheed Martin Contracts for Next Set of GPS III Satellites". GPS World. 26 February 2013. Retrieved 2 December 2017.
  114. ^ "GPS III SV08 Core Mate Complete, Space Vehicle Named for NASA Trailblazer". Space and Missile Systems Center. Los Angeles Air Force Base. 10 June 2020. Retrieved 12 June 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  115. ^ "Military Communications & Positioning, Navigation, and Timing Overview & GPS Enterprise Update" (PDF). U.S. Space Force Space Systems Command. 16 November 2022. Retrieved 21 March 2023.
  116. ^ a b "GPS III Space Vehicle 09 declared "Available for Launch"" (PDF). Space Systems Command. 26 August 2022. Retrieved 19 January 2023.
  117. ^ a b "SMC exercises contract options to procure two additional GPS III satellites" (Press release) United States Air Force 21 September 2016 Public Domain This article incorporates text from this source, which is in the public domain.
  118. ^ Dunn, Michael (6 March 2023). "Directions 2023: Advancing GPS to Meet the Future". GPSWorld.com. Retrieved 21 March 2023.
  119. ^ "SpaceX launches GPS satellite to provide PNT services". GPS World. 18 June 2021. Retrieved 18 June 2021.
  120. ^ Dunn, Michael (2 May 2022). "Directions 2022: GPS positioned for the future". GPSWorld.com. Retrieved 21 January 2023.
  121. ^ "Sixth GPS III Satellite Built By Lockheed Martin Launches As Part Of Constellation Modernization". Lockheed Martin. 18 January 2023. Retrieved 31 January 2023.
  122. ^ "GAO-23-106059 Weapon Systems Annual Assessment" (PDF). Government Accountability Office.
  123. ^ a b c d "Modernized Selected Acquisition Report (MSAR) Global Positioning System III Follow-On Production (GPS IIIF)" (PDF). US DOD. 31 December 2023. Retrieved 21 August 2024.
  124. ^ a b c d e f g h "Department of Defense Fiscal Year (FY) 2025 Budget Estimates" (PDF). April 2024.
  125. ^ a b c d e Gleckel, Gerry (15 November 2017). "GPS Status and Modernization Progress" (PDF). gps.gov. Retrieved 1 December 2017. Public Domain This article incorporates text from this source, which is in the public domain.
  126. ^ https://www.gao.gov/assets/gao-24-106841.pdf
[edit]