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GPS Block IIIF

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GPS Block IIIF
ManufacturerLockheed Martin
Country of originUnited States
OperatorUnited States Space Force
ApplicationsSatellite navigation
Specifications
BusSV11-SV12: Lockheed Martin LM2100M[1],
SV13+: Lockheed Martin LM2100 Combat Bus[2]
RegimeSemi-synchronous MEO
Design life15 years
Production
StatusIn production
PlannedUp to 22[3]
On order10[4]
Built0
Maiden launch2027 (planned)[5]
Last launch2034 (planned)[6]
Related spacecraft
Derived fromGPS Block III
← GPS Block III

GPS Block IIIF, or GPS III Follow On (GPS IIIF), is the second set of GPS Block III satellites, consisting of up to 22 space vehicles. The United States Air Force began the GPS Block IIIF acquisition effort in 2016.[7] On 14 September 2018, a manufacturing contract with options worth up to $7.2 billion was awarded to Lockheed Martin.[8][9] The 22 satellites in Block IIIF are projected to start launching in 2027, with launches estimated to last through at least 2037.[5][6][10]

System enhancements

[edit]

Engineering efforts for Block IIIF satellites began upon contract award in 2016—a full 16 years after the government approved entry into the initial modernization efforts for GPS III in 2000.[7][11] As a result, GPS Block IIIF introduces a number of improvements and novel capabilities compared to all previous GPS satellite blocks.

Improvements

[edit]

Nuclear detonation detection system

[edit]

Block IIIF satellites host a redesigned U.S. Nuclear Detonation Detection System (USNDS) capability that is both smaller and lighter than previous systems.[11]

The USNDS is a worldwide system of space-based sensors and ground processing equipment designed to detect, identify, locate, characterize, and report nuclear detonations in the Earth's atmosphere and in space.[12]

Fully-digital navigation

[edit]

GPS IIIF satellites are the first to feature a 100% digital navigation payload.[13]

The fully-digital navigation payload introduced by Block IIIF (SV11+) produces improved accuracy, better reliability, and stronger signals compared to the 70% digital navigation payload used by GPS Block III (SV01-SV10).[14][15]

Improved satellite bus

[edit]

GPS IIIF-03 and beyond (GPS III SV13+) will incorporate the Lockheed Martin LM2100 Combat Bus, an improvement on the LM2100M bus used in GPS III SV01 through SV12. The LM2100 Combat Bus provides improved resilience to cyber attacks, as well as improved spacecraft power, propulsion, and electronics.[16][2]

Novel capabilities

[edit]

Energetic charged particle sensor

[edit]

GPS IIIF satellites will be the first GPS satellites to host an Energetic Charged Particle (ECP) sensor payload.[6]

In March 2015, the U.S. Secretary of the Air Force enacted policy mandating all new Air Force satellite programs must include ECP sensors.[17] Aggregating ECP data from multiple satellites allows for enhanced space domain awareness, enabling improved detection of space weather effects as well as differentiation between anomalies induced by hostile activity, the natural environment, or other non-hostile causes.[18][6][19]

Search and rescue distress beacon detection

[edit]

GPS IIIF will be the first GPS satellite block to have all space vehicles participate in the Cospas-Sarsat system. The Cospas-Sarsat system is an international collection of satellites spanning low-earth, medium-earth, and geostationary orbit satellites which all listen for 406 MHz distress signals generated by beacons on earth. Satellites relay distress signals to ground stations to initiate timely emergency response efforts.[20]

Laser retro-reflector array

[edit]

Adding laser retro-reflector arrays (LRAs) to all GPS IIIF Space Vehicles allows GPS monitoring stations on earth equipped with laser rangefinding equipment to determine much more precise 3D locations for every GPS IIIF satellite. This improves the ability of the GPS system to provide more accurate time/position fixes to GPS receivers. Estimates are that as more GPS satellites host LRAs, the location accuracy will improve from one meter achievable today to one centimeter accuracy, an improvement of several orders of magnitude.[21]

Unified S-band capability compliance

[edit]

Block IIIF will be compliant with the Unified S-Band (USB) capabilities, allowing for consolidation of radio frequencies used for telemetry, tracking, and commanding of Block IIIF satellites.[22][11]

Regional military protection capability

[edit]

Regional Military Protection (RMP) is an anti-jamming technology for military GPS consumers. RMP involves directing a massively-amplified spot beam which only includes military GPS signals over a small geographic area. US/allied military GPS receivers located within the RMP spot beam's signal footprint are significantly more difficult for adversaries to jam due to the extremely-amplified signal strength in the area.[16]

On-orbit servicing

[edit]

GPS IIIF-03 and newer satellites (GPS III SV13+) will incorporate Lockheed-Martin's LM2100 Combat Bus.[2] Satellites based on the Combat Bus are capable of hosting the "Augmentation System Port Interface" (ASPIN), an interface that allows for future on-orbit servicing and upgrade opportunities.[16][23]

Launch history

[edit]

The first GPS Block IIIF satellite is planned to launch in 2027.[24]

GPS Block IIIF satellites
Satellite SVN Launch Date (UTC) Rocket Launch Site Status Ref
GPS IIIF-11 2027 Falcon Heavy Kennedy, LC-39A In production [25][26]
GPS IIIF-12 In production [25]
GPS IIIF-13 Ordered [27]
GPS IIIF-14 Ordered [27]
GPS IIIF-15 Ordered [2]
GPS IIIF-16 Ordered [2]
GPS IIIF-17 Ordered [2]
GPS IIIF-18 Ordered [4]
GPS IIIF-19 Ordered [4]
GPS IIIF-20 Ordered [4]


[edit]
Main article: GPS signals

Note: none of the navigation signals that GPS Block IIIF satellites transmit are new in Block IIIF; all signals were first supported in previous generation (Block I, Block II, or Block III) GPS satellites.

Civilian

[edit]
Signal name Frequency (MHz) First satellite generation (Year first launched) Status Navigation data No. of satellites Remarks
L1 C/A 1575.42[28] Block I (1978; 46 years ago (1978)) Fully operational Yes 31[29] Legacy GPS navigation signal
L1C 1575.42[30] Block III (2018; 6 years ago (2018))[30] Developmental (marked "unhealthy", no navigation payload)[30] No[30] 6 (as of April 2024)[30] Developed as a common civil signal for GPS and Galileo GNSS systems.[30]
L2C 1227.60[31] Block IIR-M (2005; 19 years ago (2005))[31] Pre-Operational (marked "Healthy")[31] Yes[31] 25 (as of April 2024)[31] Specifically designed to meet commercial needs. Broadcast at a higher effective power level than L1 C/A, improving reception in locations that L1 C/A struggles, such as under heavy trees or inside buildings.[31]
L5 1176.45[32] Block IIF (2010; 14 years ago (2010))[32] Pre-Operational (marked "unhealthy")[32] Yes[32] 18 (as of April 2024)[32] Designed for safety-of-life applications.[32]

Design

[edit]

GPS IIIF is an evolution of GPS III, which uses the A2100 bus as its core. The new models use the modernized LM2100 bus along with a fully digital navigation payload from L3Harris, a significant upgrade from the previous 70% digital payload used in GPS III.[33][34][35]

An upgraded version known as the LM2100 Combat Bus will be used starting with the third service vehicle. It will enable on-orbit servicing at a later date, which may include hardware upgrades, component replacement, or refuelling.[36][37]

Medium Earth Orbit Search and Rescue (MEOSAR) payloads are being provided by the Canadian government on behalf of the Canadian Armed Forces. The time it takes to detect and locate a distress signal will be reduced from an hour to five minutes, along with greatly improved accuracy in locating a distress beacon.[38][39]

Laser Retroreflector Arrays (LRAs) will be built by the United States Naval Research Lab. This is a passive reflector system that improves accuracy and provides better ephemeris data. The National Geospatial-Intelligence Agency (NGA) will fund the integration costs of the LRA.

Other significant enhancements include: unified S-Band (USB) interface compliance, integration of hosted payloads including a redesigned United States Nuclear Detonation (NUDET) Detection System (USNDS) payload, Energetic Charged Particles (ECP) sensor, and Regional Military Protection (RMP) capabilities that provide the ability to deliver high-power regional Military Code (M-Code) signals in specific areas of intended effect.[40]

The U.S. Air Force has identified four "technology insertion points" for GPS Block IIIF.[41] These four points are the only four times during the block's lifecycle where new capabilities will be allowed to be introduced to Block IIIF satellites.

Technology Insertion Point 1 (estimated FY2026)

[edit]
  • First Space Vehicle: GPS IIIF-01
  • Proposed/possible new functionality:
    • On Orbit Reprogrammable Digital Payload[42][43][44]
    • High Power Amplifiers (SSPA's)[44]
    • Regional Military Protection (RMP)[45]

Technology Insertion Point 2 (estimated FY2028)

[edit]
  • First Space Vehicle: GPS IIIF-07
  • Proposed/possible new functionality:
    • M-Code Space Service Volume[46]

Technology Insertion Point 3 (estimated FY2030)

[edit]
  • First Space Vehicle: GPS IIIF-13
  • Proposed/possible new functionality:
    • Near Real-Time Commanding
    • Advanced Clocks[44]

Technology Insertion Point 4 (estimated FY2033)

[edit]
  • First Space Vehicle: GPS IIIF-19
  • Proposed/possible new functionality:
    • TBD

Development

[edit]

Space Segment (Satellites)

[edit]

The U.S. Air Force employed a two-phase competitive bid acquisition process for the GPS Block IIIF satellites.

Phase One: Production Feasibility Assessment

[edit]

On 5 May 2016, the U.S. Air Force awarded three Phase One Production Readiness Feasibility Assessment contracts for GPS III Space Vehicles (SV's) 11+, one each to Boeing Network and Space Systems, Lockheed Martin Space Systems Company, and Northrop Grumman Aerospace Systems.[9][47] The phase one contracts were worth up to six million dollars each.[48] During the phase one effort, both Boeing and Northrop Grumman demonstrated working navigation payloads.[49]

Phase Two: Satellite Manufacturing

[edit]

On 19 April 2017, the U.S. Air Force Space Command announced the start of the second phase of its acquisition strategy with the publication of a special notice for an "Industry Day" for companies planning on bidding for the contract to manufacture GPS III vehicles 11+.[48] During the Industry Day event, the Air Force shared the tentative acquisition strategy which it will use to evaluate proposals, then solicited feedback from potential bidders.

In July 2017, the Deputy Director of the U.S. Air Force GPS Directorate stated the acquisition strategy for GPS Block IIIF would be to award the manufacturing contracts for all 22 Block IIIF satellites to the same contractor.[41]

In November 2017, the Deputy Director of the U.S. Air Force's GPS Directorate announced the name of the second tranche of GPS III satellites was "GPS Block IIIF".[50]

Also in November 2017, it was announced that development of the fully digital navigation payload for GPS Block IIIF satellites had completed.[51] The Block IIIA program schedule was delayed multiple times due to issues with the navigation payload.[52][53]

Bidding
[edit]

While the Air Force originally expected to publish the formal Request For Proposals (RFP) for GPS Block IIIF production in September 2017, it was not released until 13 February 2018.[54] The RFP was for a firm-fixed price (FFP) contract for a single company to manufacture all 22 space vehicles. All three participants from phase one (Boeing, Lockheed Martin, and Northrop Grumman) were believed to be likely to submit proposals.[48] The government held a pre-proposal conference in El Segundo, California, to be held on 15 March 2018 for potential bidders to ask the Air Force questions about the solicitation. The submission deadline for proposals was 16 April 2018.[55]

The bid status of companies who participated in phase one, in alphabetical order:

  • Boeing: declined to submit a proposal[56]
  • Lockheed Martin: submitted a proposal[56]
  • Northrop: declined to submit a proposal[8]
Funding
[edit]

On 14 September 2018, the Air Force awarded a manufacturing contract with options worth up to US$7.2 billion to Lockheed Martin.[8]

GPS Block IIIF Space Segment Funding History
Date Description USD (millions) Percent of Contract Ceiling Funded Space Vehicles Remarks
Authorized Remaining to Contract Ceiling Funded (Max of 22) Average Price Per SV (USD in millions)
Incremental Cumulative
September 2018 Development costs, production of SV's 11–12[57] 1300 1300 5900 18% 11–12 (2) 650 Price per satellite includes research & development costs
October 2020 Production of SV's 13–14[27] 511 1811 5389 25% 11–14 (4) 453
October 2021 Production of SV's 15–17[2] 737 2548 4652 35% 11–17 (7) 364
December 2022 Production of SV's 18–20[4] 744 3292 3908 46% 11–20 (10) 329

Control Segment (Ground-Based Command & Control)

[edit]

GPS Block IIIF's ground control system of record will be the same used for GPS Block III, the Next Generation GPS Operational Control System (OCX).

In order to be able to command and control Block IIIF satellites, in April 2021 the U.S. Space Force awarded a $228 million contract to Raytheon Intelligence and Space called OCX Block 3F, which builds on the existing OCX Block 2 system and adds the ability to perform Launch and Checkout of Block IIIF satellites.[58][59]

OCX Block 3F delivery was expected in July 2025, with operational acceptance expected in late 2027.[59][60]

Date Deployment Space Vehicles Remarks
Command & Control System Satellites Delivering Navigation Data
Block II Block III Block IIIF Block II Block III Block IIIF
March 2023[61] OCX Block 2 OCX N/A Yes No Full GPS III functionality achieved, L1C navigational signals begin transmitting
July 2025[62] OCX Block 3F OCX (limited) Block IIIF: OCX only able to be used for Launch & Checkout Services (LCS)

See also

[edit]

References

[edit]
  1. ^ "GPS-3F (Navstar-3F)". space.skyrocket.de. Retrieved 23 January 2021.
  2. ^ a b c d e f g Luccio, Matteo (16 November 2021). "U.S. Space Force contracts Lockheed Martin for 3 more GPS IIIF satellites". GPSWorld.com. Retrieved 21 January 2023.
  3. ^ Divis, Dee Ann (15 September 2018). "Lockheed Awarded $7.2 billion GPS IIIF Contract". InsideGNSS.com. Retrieved 22 January 2023.
  4. ^ a b c d e Cozzens, Tracy (5 December 2022). "Space Force orders 3 more GPS IIIF satellites from Lockheed". GPSWorld.com. Retrieved 21 January 2023.
  5. ^ a b "Military Communications & Positioning, Navigation, and Timing Overview & GPS Enterprise Update" (PDF). U.S. Space Force Space Systems Command. 16 November 2022. Retrieved 21 January 2023.
  6. ^ a b c d Gleckel, Gerry (15 November 2017). "GPS Status and Modernization Program" (PDF). gps.gov. U.S. Air Force. Retrieved 1 December 2017. Public Domain This article incorporates text from this source, which is in the public domain.
  7. ^ a b "SMC releases RFP for GPS III Space Vehicles 11+ Phase 1 Production Readiness Feasibility Assessment". U.S. Air Force Space and Missile System Center Public Affairs Office. 8 January 2016. Retrieved 22 January 2023.
  8. ^ a b c "AF Announces selection of GPS III follow-on contract". Secretary of the Air Force Public Affairs. 14 September 2018. Retrieved 22 June 2021.
  9. ^ a b "Air Force's Space and Missile Systems Center Awards Global Positioning System III Space Vehicles 11+ Phase 1 Production Readiness Feasibility Assessment Contracts". U.S. Air Force Space and Missile Systems Center. 5 May 2016. Retrieved 1 December 2017. Public Domain This article incorporates text from this source, which is in the public domain.
  10. ^ "GPS MODERNIZATION – Delays Continue in Delivering More Secure Capability for the Warfighter – Report to Congressional Committees" (PDF). U.S. Government Accounting Office. For further information contact Jon Ludwigson. United States Government Accounting Office (GAO-24-106841). September 2024. Retrieved 1 November 2024.{{cite web}}: CS1 maint: others (link) CS1 maint: url-status (link)
  11. ^ a b c "GPS III Selective Acquisition Report" (PDF). U.S. Space Force. 1 December 2019. Retrieved 22 January 2023.
  12. ^ "(U) Evaluation of the Space-Based Segment of the U.S. Nuclear Detonation Detection System" (PDF). U.S. Department of Defense Inspector General. 28 September 2018. Retrieved 22 January 2023.
  13. ^ "Four More Digital Mission Data Units for GPS IIIF Satellites to Come from L3Harris". InsideGNSS.com. 23 February 2021. Retrieved 22 January 2023.
  14. ^ "L3Harris Technologies passes Critical Design Review For New Fully Digital GPS IIIF Satellite Navigation Payload". L3Harris Technologies. 11 February 2020. Retrieved 22 January 2023.
  15. ^ Strout, Nathan (12 February 2020). "The next GPS payload will be fully digital". C4ISRNet.com. Retrieved 22 January 2023.
  16. ^ a b c "GPS III/IIIF: The New Generation Of Positioning, Navigation and Timing". Lockheed Martin. 18 January 2023. Retrieved 22 January 2023.
  17. ^ Starks, Michael (2 December 2016). "White Paper on ECP Energy Range and Flux Requirements" (PDF). Air Force Research Laboratory Space Vehicles Directorate. Retrieved 22 January 2023.
  18. ^ U.S. Air Force (30 November 2016). "Automatic Exploitation of Energetic Charged Particle Sensor Data". SBIR.gov. Retrieved 22 January 2023.
  19. ^ Erwin, Sandra (14 November 2019). "Air Force: SSA is no more; it's 'Space Domain Awareness'". SpaceNews.com. Retrieved 22 January 2023.
  20. ^ "Search and Rescue Satellites". U.S. National Oceanic and Atmospheric Administration. Retrieved 22 January 2023.
  21. ^ GPS World Staff (1 September 2013). "Expert Advice: Laser Reflectors to Ride on Board GPS III". GPSWorld.com. Retrieved 22 January 2023.
  22. ^ "GPS Future and Evolutions". European Space Agency. 1 January 2011. Retrieved 22 January 2023.
  23. ^ "Lockheed Martin Contracted To Build Three GPS III Follow On Satellites By USSF". satnews.com. 15 November 2021. Retrieved 22 January 2023.
  24. ^ "Final GPS III Missions, First GPS IIIF Satellites Part of SSC's Latest Launch Assignments". Inside GNSS. 5 November 2023. Retrieved 21 November 2023.
  25. ^ a b "Lockheed Lays Out GPS IIIF Upgrade Roadmap". Aviation Week. 8 April 2022. Retrieved 15 May 2023.
  26. ^ "After Vulcan slips, Space Force ends up awarding more missions to SpaceX". Ars Technica. 2 November 2023. Retrieved 28 November 2023.
  27. ^ a b c "Lockheed Martin gets $511 million contract for two GPS satellites". SpaceNews. 10 December 2020. Retrieved 21 June 2021.
  28. ^ Gabor, Michael. "GPS Overview". University of Texas at Austin. Retrieved 22 January 2023.
  29. ^ "GPS Constellation". U.S. Coast Guard Navigation Center. Retrieved 22 January 2023.
  30. ^ a b c d e f "Fourth Civil Signal: L1C". GPS.gov. 1 June 2022. Retrieved 22 January 2023.
  31. ^ a b c d e f "Second Civil Signal: L2C". GPS.gov. 1 June 2022. Retrieved 22 January 2023.
  32. ^ a b c d e f "Third Civil Signal: L5". GPS.gov. 1 June 2022. Retrieved 22 January 2023.
  33. ^ "L3Harris Contracted for 4 Mission Data Units for GPS IIIF Satellites". Via Satellite. 24 February 2021. Retrieved 14 June 2021.
  34. ^ GNSS, Inside (23 February 2021). "Four More Digital Mission Data Units for GPS IIIF Satellites to Come from L3Harris". Inside GNSS – Global Navigation Satellite Systems Engineering, Policy, and Design. Retrieved 14 June 2021.
  35. ^ "Most Advanced SBIRS Missile Warning Satellite Ready For 2021 Launch". Media – Lockheed Martin. Retrieved 14 June 2021.
  36. ^ Martin, Lockheed. "Lockheed Martin's First Modernized SBIRS Missile Warning Satellite Now Under U.S. Space Force Control". www.prnewswire.com (Press release). Retrieved 14 June 2021.
  37. ^ "Lockheed Martin to upgrade GPS satellites for in-orbit servicing". SpaceNews. 26 February 2021. Retrieved 18 June 2021.
  38. ^ "MDA to build search-and-rescue repeaters for GPS 3F satellites". SpaceNews. 13 May 2019. Retrieved 14 June 2021.
  39. ^ Canada, Public Services and Procurement. "Government of Canada awards contract for new space-based search and rescue technology". www.newswire.ca. Retrieved 14 June 2021.
  40. ^ "Department of Defense Fiscal Year 2022 Budget Estimates" (PDF). Assistant Secretary of the Air Force, Financial Management and Comptroller. May 2021.
  41. ^ a b Divis, Dee Ann (17 July 2017). "GPS Official: Expect One Follow-on GPS III Contractor, Tech Insertion Points". insidegnss.com. Gibbons Media & Research. Archived from the original on 18 February 2018. Retrieved 15 August 2017.
  42. ^ "Lockheed Martin to upgrade GPS satellites for in-orbit servicing". SpaceNews. 26 February 2021. Retrieved 27 February 2021.
  43. ^ "On-Orbit Reprogrammable Digital Waveform Generator (ORDWG) for the GPS Spaceccraft Navigation Payload". govtribe.com. US Air Force Research Lab. 8 January 2014. Retrieved 10 November 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  44. ^ a b c "Advanced GPS Technologies" (PDF). gps.gov. US Air Force Research Lab. 1 May 2015. Retrieved 10 November 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  45. ^ "Military GPS Receiver Advances Could Help Trim Satellite Costs" (PDF). Inside GNSS. June 2016. Retrieved 10 November 2018.
  46. ^ Bauer, Frank (11 June 2015). "GPS Space Service Volume (SSV) Ensuring Consistent Utility Across GPS Design Builds for Space Users" (PDF). gps.gov. Retrieved 10 November 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  47. ^ U.S. Air Force Space and Missile Systems Center, Public Affairs (8 January 2016). "SMC releases RFP for GPS III Space Vehicles 11+ Phase 1 Production Readiness Feasibility Assessment". Retrieved 2 December 2017. Public Domain This article incorporates text from this source, which is in the public domain.
  48. ^ a b c Divis, Dee Ann (27 April 2017). "Door Open to New Bidders as Air Force Moves Closer to GPS III Buy". insidegnss.com. Gibbons Media & Research. Archived from the original on 2 December 2017. Retrieved 3 May 2017.
  49. ^ Capaccio, Anthony (2 November 2017). "Air Force Plans US$10 Billion GPS III Contest Amid Lockheed Delays". bloomberg.com. Bloomberg. Retrieved 2 December 2017.
  50. ^ Divis, Dee Ann (22 November 2017). "Next Tranche of GPS Satellites to be called GPS IIIFs". insidegnss.com. Gibbons Media & Research. Archived from the original on 2 December 2017. Retrieved 1 December 2017.
  51. ^ "Harris Completes Development of Fully Digital Navigation Payload for Future GPS III Satellites". 9 November 2017. Archived from the original on 3 December 2017. Retrieved 2 December 2017.
  52. ^ "GPS III Payload Facing Delays". gpsworld.com. North Coast Media. 11 February 2014. Retrieved 2 December 2017.
  53. ^ Gruss, Mike (14 September 2016). "Lockheed Martin says first GPS 3 satellite delayed until December". SpaceNews. Retrieved 2 December 2017.
  54. ^ Divis, Dee Ann (16 January 2018). "Industry Awaits GPS III RFP As Delays Mount". insidegnss.com. Gibbons Media & Research. Archived from the original on 20 January 2018. Retrieved 18 January 2018.
  55. ^ "GPS IIIF Request For Proposal (RFP)". fbo.gov. 13 February 2018. Retrieved 13 February 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  56. ^ a b Divis, Dee Ann (18 April 2018). "Boeing Declines to Bid on GPS III". insidegnss.com. Gibbons Media & Research. Archived from the original on 19 April 2018. Retrieved 20 April 2018.
  57. ^ "Space Systems Command Exercises Contract Option for Three Additional GPS IIIF Satellites" (PDF). U.S. Space Force Space Systems Command. 28 November 2022. Retrieved 22 January 2023.
  58. ^ Dunn, Michael (2 May 2022). "Directions 2022: GPS positioned for the future". GPSWorld.com. Retrieved 21 January 2023.
  59. ^ a b "Counting 0, 1, 2, 3F: The Long Hello of GPS OCX". Inside GNSS. 6 May 2021. Retrieved 21 January 2023.
  60. ^ "Military Communications & Positioning, Navigation, and Timing Overview & GPS Enterprise Update" (PDF). U.S. Space Force Space Systems Command. 6 November 2022. Retrieved 21 January 2023.
  61. ^ "Next Generation Operational Control System (OCX) Selected Acquisition Report" (PDF). U.S. Department of Defense. 8 April 2022. Retrieved 21 January 2023.
  62. ^ "Counting 0, 1, 2, 3F: The Long Hello of GPS OCX". InsideGNSS.com. 6 May 2021. Retrieved 21 January 2023.
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