Wikipedia

GPS Block III

GPS Block III (previously Block IIIA) consists of the first ten GPS III satellites, which are used to keep the Navstar Global Positioning System operational. Lockheed Martin designed, developed and manufactured the GPS III Non-Flight Satellite Testbed (GNST) and all ten Block III satellites.[6] The first satellite in the series was launched in December 2018.[7][8][9]

GPS Block III
Artist's impression of a GPS Block III satellite in orbit
ManufacturerLockheed Martin
Country of originUnited States
OperatorUS Space Force
ApplicationsNavigation satellite
Specifications
BusLockheed Martin A2100M
Launch mass3,880 kg (8,550 lb)[1]
Dry mass2,269 kg (5,002 lb)
Power4480 watts (end of life)
BatteriesNickel–hydrogen battery
RegimeSemi-synchronous Medium Earth orbit
Design life15 years (planned)
Production
StatusProduction complete
Built10[2]
Launched6
Operational6[3]
Maiden launch23 December 2018[4]
Last launch18 January 2023[5]
Related spacecraft
Derived fromGPS Block IIF
← GPS Block IIF GPS Block IIIF →

History

edit

The United States' Global Positioning System (GPS) reached Full Operational Capability on 17 July 1995,[10] completing its original design goals. Advances in technology and new demands on the existing system led to the effort to modernize the GPS system. In 2000, the U.S. Congress authorized the effort, referred to as GPS III.

The project involves new ground stations and new satellites, with additional navigation signals for both civilian and military users, and aims to improve the accuracy and availability for all users.

Raytheon was awarded the Next Generation GPS Operational Control System (OCX) contract on 25 February 2010.[11]

The first satellite in the series was projected to launch in 2014,[12] but significant delays[13] pushed the launch to December 2018.[7][14] The tenth and final GPS Block III launch is projected in FY2026.[15]

Development

edit
 
GPS III SV-01 sits in Lockheed Martin's GPS III Processing facility after its successful core mate. SMC’s eighth next-generation GPS III satellite completed core mating on 15 April 2016. It is named after NASA trailblazer Katherine Johnson.

Block III satellites use Lockheed Martin's A2100M satellite bus structure. The propellant and pressurant tanks are manufactured by Orbital ATK from lightweight, high-strength composite materials.[16] Each satellite will carry eight deployable JIB antennas designed and manufactured by Northrop Grumman Astro Aerospace[17]

Already delayed significantly beyond the first satellite's planned 2014 launch,[12] on 27 April 2016, SpaceX, in Hawthorne, California, was awarded a US$82.7 million firm-fixed-price contract for launch services to deliver a GPS III satellite to its intended orbit. The contract included launch vehicle production, mission integration, and launch operations for a GPS III mission, to be performed in Hawthorne, California; Cape Canaveral Air Force Station, Florida; and McGregor, Texas.[18] In December 2016, the Director of the U.S. Air Force's Global Positioning Systems Directorate announced the first satellite would launch in the spring of 2018.[19] In March 2017, the U.S. General Accounting Office stated "Technical issues with both the GPS III satellite and the OCX Block 0 launch control and checkout system have combined to place the planned March 2018 launch date for the first GPS III satellite at risk".[20] The delays were caused by a number of factors, primarily due to issues found in the navigation payload.[13][21] Further launch date slippages were caused by the need for additional testing and validation of a SpaceX Falcon 9 rocket which ultimately launched the satellite on 23 December 2018.[22][23] On 22 August 2019, the second GPS III satellite was launched aboard a Delta IV rocket.[24]

On 21 September 2016, the U.S. Air Force exercised a US$395 million contract option with Lockheed Martin for the ninth and tenth Block III space vehicles, expected to be available for launch by 2022.[25]

Launch history

edit

6 of 10 GPS Block III satellites have been launched. 6 are currently operational, with 0 undergoing testing.

Satellite SVN Launch date (UTC) Rocket Launch site Status Ref.
USA-289
GPS III-01
Vespucci 		74 23 December 2018, 13:51 Falcon 9 Block 5 Cape Canaveral, SLC‑40 In service [26][27]
USA-293
GPS III-02
Magellan 		75 22 August 2019, 13:06 Delta IV M+ (4,2) Cape Canaveral, SLC‑37B In service [28]
USA-304
GPS III-03
Matthew Henson 		76 30 June 2020, 20:10 Falcon 9 Block 5 Cape Canaveral, SLC‑40 In service [29]
USA-309
GPS III-04
Sacagawea 		77 5 November 2020, 23:24 Falcon 9 Block 5 Cape Canaveral, SLC‑40 In service [30]
USA-319
GPS III-05
Neil Armstrong 		78 17 June 2021, 16:09 Falcon 9 Block 5 Cape Canaveral, SLC‑40 In service [31]
USA-343
GPS III-06
Amelia Earhart 		79 18 January 2023, 12:24 Falcon 9 Block 5 Cape Canaveral, SLC‑40 In service [32][33][34][35]
GPS III-07
Sally Ride 		80 January 2025 Vulcan Centaur VC2S Cape Canaveral, SLC‑41 Available for launch [32][36]
GPS III-08
Katherine Johnson 		81 2025 Vulcan Centaur Cape Canaveral, SLC‑41 Available for launch [32][15][37]
GPS III-09
Ellison Onizuka 		82 FY2026 Vulcan Centaur Cape Canaveral, SLC‑41 Available for launch [38][15][39]
GPS III-10
Hedy Lamarr 		83 FY2026 Falcon 9 Block 5 Cape Canaveral, SLC‑40 Available for launch [38][15]

New navigation signals

edit
Main article: GPS signals

Civilian L2 (L2C)

edit

One of the first announcements was the addition of a new civilian-use signal to be transmitted on a frequency other than the L1 frequency used for the existing GPS Coarse Acquisition (C/A) signal. Ultimately, this became known as the L2C signal because it is broadcast on the L2 frequency (1227.6 MHz). It can be transmitted by all block IIR-M and later design satellites. The original plan stated that until the new OCX (Block 1) system is in place, the signal would consist of a default message ("Type 0") that contains no navigational data.[40] OCX Block 1 with the L2C navigation data was scheduled to enter service in February 2016,[41][42] but was delayed until 2022 or later.[43]

As a result of OCX delays, the L2C signal was decoupled from the OCX deployment schedule. All satellites capable of transmitting the L2C signal (all GPS satellites launched since 2005) began broadcasting pre-operational civil navigation (CNAV) messages in April 2014, and in December 2014 the U.S. Air Force started transmitting CNAV uploads on a daily basis.[40][44] The L2C signal will be considered fully operational after it is being broadcast by at least 24 space vehicles, projected to happen in 2023.[40] As of October 2017, L2C was being broadcast from 19 satellites; by June 2022 there were 24 satellites broadcasting this signal.[40] The L2C signal is tasked with providing improved accuracy of navigation, providing an easy-to-track signal, and acting as a redundant signal in case of localized interference.

The immediate effect of having two civilian frequencies being transmitted from one satellite is the ability to directly measure, and therefore remove, the ionospheric delay error for that satellite. Without such a measurement, a GPS receiver must use a generic model or receive ionospheric corrections from another source (such as a Satellite Based Augmentation System). Advances in technology for the GPS satellites and the GPS receivers have made ionospheric delay the largest source of error in the C/A signal. A receiver capable of performing this measurement is referred to as a dual frequency receiver. Its technical characteristics are:

  • L2C contains two distinct PRN sequences:
    • CM (for Civilian Moderate length code) is 10,230 bits in length, repeating every 20 milliseconds.
    • CL (for Civilian Long length code) is 767,250 bits, repeating every 1,500 milliseconds (i.e., every 1.5 second).
    • Each signal is transmitted at 511,500 bits per second (bit/s); however, they are multiplexed to form a 1,023,000 bit/s signal.
  • CM is modulated with a 25 bit/s navigation message with forward error correction, whereas CL contains no additional modulated data.
  • The long, non-data CL sequence provides for approximately 24 dB greater correlation protection (~250 times stronger) than L1 C/A.
  • L2C signal characteristics provide 2.7 dB greater data recovery and 0.7 dB greater carrier tracking than L1 C/A.
  • The L2C signals' transmission power is 2.3 dB weaker than the L1 C/A signal.
  • In a single frequency application, L2C has 65% more ionospheric error than L1.

It is defined in IS-GPS-200.[45]

Military (M-code)

edit

A major component of the modernization process, a new military signal called M-code was designed to further improve the anti-jamming and secure access of the military GPS signals. The M-code is transmitted in the same L1 and L2 frequencies already in use by the previous military code, the P(Y) code. The new signal is shaped to place most of its energy at the edges (away from the existing P(Y) and C/A carriers). Unlike the P(Y) code, the M-code is designed to be autonomous, meaning that users can calculate their positions using only the M-code signal. P(Y) code receivers must typically first lock onto the C/A code and then transfer to lock onto the P(Y) code.

In a major departure from previous GPS designs, the M-code is intended to be broadcast from a high-gain directional antenna, in addition to a wide angle (full Earth) antenna. The directional antenna's signal, termed a spot beam, is intended to be aimed at a specific region (i.e., several hundred kilometers in diameter) and increase the local signal strength by 20 dB (10× voltage field strength, 100× power). A side effect of having two antennas is that, for receivers inside the spot beam, the GPS satellite will appear as two GPS signals occupying the same position.

While the full-Earth M-code signal is available on the Block IIR-M satellites, the spot beam antennas will not be available until the Block III satellites are deployed. Like the other new GPS signals, M-code is dependent on OCX—specifically Block 2—which was scheduled to enter service in October 2016,[42][46] but which was delayed until 2022,[47] and that initial date did not reflect the two year first satellite launch delays expected by the GAO.[48][49]

Other M-code characteristics are:

  • Satellites will transmit two distinct signals from two antennas: one for whole Earth coverage, one in a spot beam.
  • Binary offset carrier modulation.
  • Occupies 24 MHz of bandwidth.
  • It uses a new MNAV navigational message, which is packetized instead of framed, allowing for flexible data payloads.
  • There are four effective data channels; different data can be sent on each frequency and on each antenna.
  • It can include FEC and error detection.
  • The spot beam is ~20 dB more powerful than the whole Earth coverage beam.
  • M-code signal at Earth's surface: –158 dBW for whole Earth antenna, –138 dBW for spot beam antennas.

Safety of Life (L5)

edit

Safety of Life is a civilian-use signal, broadcast on the L5 frequency (1176.45 MHz). In 2009, a WAAS satellite sent the initial L5 signal test transmissions. SVN-62, the first GPS block IIF satellite, continuously broadcast the L5 signal starting on 28 June 2010.

As a result of schedule delays to the GPS III control segment, the L5 signal was decoupled from the OCX deployment schedule. All satellites capable of transmitting the L5 signal (all GPS satellites launched since May 2010)[50] began broadcasting pre-operational civil navigation (CNAV) messages in April 2014, and in December 2014 the Air Force started transmitting CNAV uploads on a daily basis.[51] The L5 signal will be considered fully operational once at least 24 space vehicles are broadcasting the signal, currently projected to happen in 2027.[50]

As of 10 July 2023, L5 is being broadcast from 17 satellites, after the removal of the block IIF, SVM-63.[52]

  • Improves signal structure for enhanced performance.
  • Higher transmission power than L1 or L2C signal (~3 dB, or twice as powerful).
  • Wider bandwidth, yielding a 10-times processing gain.
  • Longer spreading codes (10 times longer than used on the C/A code).
  • Located in the Aeronautical Radionavigation Services band, a frequency band that is available worldwide.

WRC-2000 added a space signal component to this aeronautical band so the aviation community can manage interference to L5 more effectively than L2. It is defined in IS-GPS-705.[53]

New civilian L1 (L1C)

edit

L1C is a civilian-use signal, to be broadcast on the same L1 frequency (1575.42 MHz) that contains the C/A signal used by all current GPS users.

L1C broadcasting started when GPS III Control Segment (OCX) Block 1 becomes operational, scheduled for 2022.[43][19] The L1C signal will reach full operational status when being broadcast from at least 24 GPS Block III satellites, projected for the late 2020s.[54]

  • Implementation will provide C/A code to ensure backward compatibility.
  • Assured of 1.5 dB increase in minimum C/A code power to mitigate any noise floor increase.
  • Non-data signal component contains a pilot carrier to improve tracking.
  • Enables greater civil interoperability with Galileo L1.

It is defined in IS-GPS-800.[55]

Improvements

edit

Increased signal power at the Earth's surface:

  • M-code: −158 dBW / −138 dBW.
  • L1 and L2: −157 dBW for the C/A code signal and −160 dBW for the P(Y) code signal.
  • L5 will be −154 dBW.

Researchers from The Aerospace Corporation confirmed that the most efficient means to generate the high-power M-code signal would entail a departure from full-Earth coverage, characteristic of all the user downlink signals up until that point. Instead, a high-gain antenna would be used to produce a directional spot beam several hundred kilometers in diameter. Originally, this proposal was considered as a retrofit to the planned Block IIF satellites. Upon closer inspection, program managers realized that the addition of a large deployable antenna, combined with the changes that would be needed in the operational control segment, presented too great a challenge for the then existing system design.[56]

Control segment

edit

The GPS Operational Control Segment (OCS), consisting of a worldwide network of satellite operations centers, ground antennas and monitoring stations, provides Command and Control (C2) capabilities for GPS Block II satellites.[60] The latest update to the GPS OCS, Architectural Evolution Plan 7.5, was operationally accepted in 2019.[61]

Next-Generation operational control segment (OCX)

edit

In 2010, the United States Air Force announced plans to develop a modern control segment, a critical part of the GPS modernization initiative. OCS will continue to serve as the ground control system of record until the new system, Next Generation GPS Operational Control System (OCX), is fully developed and functional.[62]

OCX features are being delivered to the United States Air Force in three separate phases, known as "blocks".[63] The OCX blocks are numbered zero through two. With each block delivered, OCX gains additional functionality.

In June 2016, the U.S. Air Force formally notified Congress the OCX program's projected program costs had risen above US$4.25 billion, thus exceeding baseline cost estimates of US$3.4 billion by 25%, also known as a critical Nunn-McCurdy breach. Factors leading to the breach include "inadequate systems engineering at program inception", and "the complexity of cybersecurity requirements on OCX".[64] In October 2016, the Department of Defense formally certified the program, a necessary step to allow development to continue after a critical breach.[65]

In July 2021, all OCX monitor station installations had been completed.[66] OCX monitoring stations are expected to transition to operations in "early 2023," and the U.S. Space Force hopes to complete operational acceptance for all of OCX in 2027.[66]

OCX Block 0 (launch and checkout for Block III)

edit

OCX Block 0 provides the minimum subset of full OCX capabilities necessary to support launch and early on-orbit spacecraft bus checkout on GPS III space vehicles.[19]

Block 0 completed two cybersecurity testing events in April and May 2018 with no new vulnerabilities found.[67]

In June 2018, Block 0 had its third successful integrated launch rehearsal with GPS III.[67]

The U.S. Air Force accepted the delivery of OCX Block 0 in November 2017, and is used it to prepare for the first GPS launch in December 2018.[68]

As of May 2022, OCX Block 0 has successfully supported the launch and checkout of GPS III SV 01–05.[69]

OCX Block 1 (civilian GPS III features)

edit

OCX Block 1 is an upgrade to OCX Block 0, at which time the OCX system achieves Initial Operating Capability (IOC). Once Block 1 is deployed, OCX will for the first time be able to command and control both Block II and Block III GPS satellites, as well as support the ability to begin broadcasting the civilian L1C signal.[19]

In November 2016, the GAO reported that OCX Block 1 had become the primary cause for delay in activating the GPS III PNT mission.[70]

Block 1 completed the final iteration of Critical Design Review (CDR) in September 2018.[67] Software development on Block 1 is scheduled to complete in 2019, after which the Block 1 software will undergo 2.5 years of system testing.[67]

OCX Block 2 (military GPS III features, civilian signal monitoring)

edit

OCX Block 2 upgrades OCX with the advanced M-code features for military users and the ability to monitor performance of the civilian signals.[63] In March 2017, the contractor rephased its OCX delivery schedule so that Block 2 will now be delivered to the Air Force concurrently with Block 1.[71] In July 2017, an additional nine months delay to the schedule was announced. According to the July 2017 program schedule, OCX will be delivered to the U.S. Air Force in April 2022.[47]

OCX Block 3F (launch and checkout for Block IIIF)

edit

OCX Block 3F upgrades OCX with the ability to perform Launch & Checkout for Block IIIF satellites.[72][66] Block IIIF satellites are expected to start launching in 2026.

The OCX Block 3F contract, valued at $228 million, was awarded to Raytheon Intelligence and Space on 30 April 2021.[73]

Contingency operations

edit

GPS III Contingency Operations ("COps") is an update to the GPS Operational Control Segment, allowing OCS to provide Block IIF Position, Navigation, and Timing (PNT) features from GPS III satellites.[19] The Contingency Operations effort enables GPS III satellites to participate in the GPS constellation, albeit in a limited fashion, without having to wait until OCX Block 1 becomes operational (scheduled for 2022).

The United States Space Force awarded the US$96 million Contingency Operations contract in February 2016.[74] Contingency Ops was operationally accepted by in April 2020.[61]

Deployment schedule

edit
Date Deployment Space Vehicles Remarks
Command & Control Satellites Delivering Navigation Data
OCS OCX
December 2018[67][68] OCX Block 0 Block II Block III
(Launch and Checkout only)[19] 		Block II OCS and OCX operate in parallel
April 2020[61] Contingency Operations Block II
and
Block III
March 2023[75] OCX Block 1 and OCX Block 2 Block II & Block III OCS no longer used, L1C transmissions begin, full GPS III functionality achieved.
July 2025[72] OCX Block 3F Block II & Block III (complete), Block IIIF (Launch and Checkout only)[72]

See also

edit

References

edit
  1. ^ "GPS III fact sheet" (PDF). LockheedMartin. Archived from the original (PDF) on 6 September 2015. Retrieved 6 May 2016.
  2. ^ "Sixth GPS III Satellite Built By Lockheed Martin Launches As Part Of Constellation Modernization". Lockheed Martin. 18 January 2023. Retrieved 31 January 2023.
  3. ^ "GPS Constellation Status". Retrieved 11 March 2023.
  4. ^ Clark, Stephen (23 December 2018). "SpaceX closes out year with successful GPS satellite launch". Spaceflight Now. Retrieved 24 December 2018.
  5. ^ "Space X stream". youtube.com. 18 January 2023. Retrieved 18 January 2023.
  6. ^ "U.S. Air Force Awards Lockheed Martin Contracts to Begin Work on Next Set of GPS III Satellites" (Press release) Lockheed Martin 25 February 2013
  7. ^ a b Whitney, Steven (1 December 2017). "Directions 2018: The GPS year in review". GPS World. Retrieved 2 December 2017.
  8. ^ Brissett, Wilson (7 November 2017). "SMC Releases Draft RFP for Five EELV Launches". Air Force Association. Air Force Magazine. Retrieved 13 December 2017.
  9. ^ "Global Positioning System: Better Planning and Coordination Needed to Improve Prospects for Fielding Modernized Capability" (PDF). US Government Accountability Office (GAO). December 2017. Retrieved 18 December 2017.   This article incorporates text from this source, which is in the public domain.
  10. ^ U.S. Coast Guard Navigation Center. "GPS FAQ". U.S. Department of Homeland Security.   This article incorporates text from this source, which is in the public domain.
  11. ^ "Raytheon Awarded $886 Million GPS OCX Contract". Via Satellite. 1 March 2010. Retrieved 5 December 2022.
  12. ^ a b "U.S. Air Force Awards Lockheed Martin GPS III Flight Operations Contract" (Press release) Lockheed Martin 31 May 2012
  13. ^ a b "GPS III satellite delivery slips because of capacitor". GPS World. 15 September 2016. Retrieved 25 December 2016.
  14. ^ Gleckel, Gerry (15 November 2017). "GPS Status and Modernization Program" (PDF). gps.gov. U.S. Air Force. Retrieved 1 December 2017.   This article incorporates text from this source, which is in the public domain.
  15. ^ a b c d "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.
  16. ^ "Lockheed Orders GPS 3A Satellite Buses from ATK". Archived from the original on 2 February 2013.
  17. ^ "Northrop Grumman Corporation: News and Events – News Release". Archived from the original on 4 April 2014.
  18. ^ "Contracts for April 27, 2016". U.S. Department of Defense.   This article incorporates text from this source, which is in the public domain.
  19. ^ a b c d e f Whitney, Steven (2 December 2016). "Directions 2017: GPS navigates the future". gpsworld.com. North Coast Media LLC. Retrieved 3 December 2017.
  20. ^ "Assessments of Selected Weapon Programs" (PDF). US General Accounting Office. March 2017. Retrieved 20 June 2017.   This article incorporates text from this source, which is in the public domain.
  21. ^ "US Air Force 'not happy' with delays on Lockheed GPS satellite – the Economic Times". economictimes.indiatimes.com. Archived from the original on 25 May 2014. Retrieved 13 January 2022.
  22. ^ Clark, Stephen (17 December 2018). "Air Force requirements will keep SpaceX from landing Falcon 9 booster after GPS launch". Spaceflight Now. Retrieved 18 December 2018.
  23. ^ "SpaceX Caps Record 2018 With Launch of Air Force GPS Satellite". Bloomberg. 23 December 2018. Retrieved 23 December 2018.
  24. ^ "The last single-stick Delta rocket launched Thursday, and it put on a show". 22 August 2019.
  25. ^ Gruss, Mike (21 September 2016). "Lockheed Martin to build two more GPS 3 satellites for U.S. Air Force". Space News. Retrieved 22 September 2016.
  26. ^ Clark, Stephen (23 December 2018). "SpaceX closes out year with successful GPS satellite launch". Spaceflight Now. Retrieved 24 December 2018.
  27. ^ "NANU 2020-004". Retrieved 13 January 2020.   This article incorporates text from this source, which is in the public domain.
  28. ^ "NANU 2020-015". Retrieved 2 April 2020.   This article incorporates text from this source, which is in the public domain.
  29. ^ "NANU 2020-046". USCG Navigation Center. Retrieved 23 November 2020.
  30. ^ "NANU 2020-086". USCG Navigation Center. Retrieved 2 December 2020.
  31. ^ "NANU 2022-025". USCG Navigation Center. Retrieved 25 May 2022.
  32. ^ a b c "Fifth GPS III Satellite Takes to the Skies". Lockheed Martin. Retrieved 16 June 2021. Lockheed Martin's sixth, seventh and eighth GPS III satellites are already complete, "Available for Launch" and just waiting for launch date arrangements.
  33. ^ "Sixth GPS III satellite safely arrives in Florida for January launch" (PDF). Space Systems Command. 25 October 2022. Retrieved 7 November 2022.
  34. ^ "NAVSTAR 82 (USA 343)". N2YO. Retrieved 21 January 2023.
  35. ^ "Falcon 9 Block 5 | GPS III-6". Retrieved 7 November 2022.
  36. ^ "GPS Status and Modernization" (PDF). U.S. Space Force Space Systems Command. 12 September 2023. Retrieved 5 October 2023.
  37. ^ "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.
  38. ^ a b "SpaceX launches GPS satellite to provide PNT services". GPS World. 18 June 2021. Retrieved 22 June 2021.
  39. ^ "GPS III Space Vehicle 09 declared "Available for Launch"" (PDF). Space Systems Command. 26 August 2022. Retrieved 7 November 2022.
  40. ^ a b c d "New Civil Signals: Second Civil Signal". National Coordination Office for Space-Based Positioning, Navigation, and Timing. 23 September 2016. Retrieved 20 April 2017.   This article incorporates text from this source, which is in the public domain.
  41. ^ "Control Segment: Next Generation Operational Control System". National Coordination Office for Space-Based Positioning, Navigation, and Timing. 26 September 2013. Retrieved 21 November 2013.   This article incorporates text from this source, which is in the public domain.
  42. ^ a b Kolibaba, Ray (14 November 2012). "GPS OCX Program Status" (PDF). Stanford 2012 PNT Challenges and Opportunities Symposium. Retrieved 2 May 2017.
  43. ^ a b "GAO: New GPS Ground System, Not GPS III Engineering, Primary Cause for Delays". Inside GNSS. 30 November 2016. Archived from the original on 26 December 2016. Retrieved 25 December 2016.
  44. ^ Jewell, Don (12 August 2015). "L2C and Next-Generation Smart PNT Receivers". GPS World. Retrieved 28 December 2016.
  45. ^ "Interface Specification IS-GPS-200, Revision E" (PDF). Coast Guard Navigation Center. 8 June 2010.   This article incorporates text from this source, which is in the public domain.
  46. ^ Divis, Dee Ann (January–February 2013). "More Than Money Worries: OCX and the New Civil Signals". Inside GNSS. Archived from the original on 2 December 2013. Retrieved 21 November 2013.
  47. ^ a b Divis, Dee Ann (31 July 2017). "OCX Delayed Again as Development Jumps to $6 Billion". InsideGNSS.com. Archived from the original on 16 August 2017. Retrieved 15 August 2017.
  48. ^ "Future GPS: The USA's GPS-III Programs". Defense Industry Daily. 14 May 2014. Retrieved 17 May 2014.
  49. ^ "Defense Acquisitions: Assessments of Selected Weapon Programs". Report Number GAO-13-294SP. U.S. Government Accountability Office. 28 March 2013.   This article incorporates text from this source, which is in the public domain.
  50. ^ a b "Civil Signals – Third Civil Signal: L5". GPS.gov. 23 September 2016. Retrieved 20 April 2017.   This article incorporates text from this source, which is in the public domain.
  51. ^ "DOD Announces Start of Civil Navigation Message Broadcasting". U.S. Department of Defense. 25 April 2014. Archived from the original on 29 December 2016. Retrieved 28 December 2016.   This article incorporates text from this source, which is in the public domain.
  52. ^ Amerisurv-Editor (10 August 2023). "CGSIC Bulletin: GPS Constellation Change: SVN-63". The American Surveyor. Retrieved 16 October 2024. {{cite web}}: |last= has generic name (help)
  53. ^ "Interface Specification IS-GPS-705, Revision A" (PDF). Coast Guard Navigation Center. 8 June 2010.   This article incorporates text from this source, which is in the public domain.
  54. ^ "Civil Signals – Fourth Civil Signal: L1C". GPS.gov. 23 September 2016. Retrieved 28 December 2016.   This article incorporates text from this source, which is in the public domain.
  55. ^ "Interface Specification IS-GPS-800, Revision D" (PDF). National Coordination Office for Space-Based Positioning, Navigation, and Timing. 24 September 2013.   This article incorporates text from this source, which is in the public domain.
  56. ^ Lazar, Steven (Summer 2002). "Modernization and the Move to GPS III" (PDF). Crosslink. 3 (2): 42–46. Archived from the original (PDF) on 4 April 2014. Retrieved 29 June 2012.
  57. ^ "ILRS Meeting on Retroreflector Arrays" (PDF).   This article incorporates text from this source, which is in the public domain.
  58. ^ "Slides from ILRS Meeting on Retroreflector Arrays" (PDF). April 2006.   This article incorporates text from this source, which is in the public domain.
  59. ^ "NASA Search and Rescue Mission Office : Distress Alerting Satellite System (DASS)". Archived from the original on 4 March 2016.   This article incorporates text from this source, which is in the public domain.
  60. ^ "GPS Operational Control Segment". U.S. Air Force. 27 November 2012. Retrieved 25 December 2016.   This article incorporates text from this source, which is in the public domain.
  61. ^ a b c Colonel John Claxton (12 December 2019). "Directions 2020: Delivering GPS Capabilities". GPSWorld.com. Retrieved 21 January 2023.
  62. ^ "GPS Advanced Control Segment (OCX)". Archived from the original on 3 May 2012.   This article incorporates text from this source, which is in the public domain.
  63. ^ a b "GPS Control Segment". gps.gov. Retrieved 25 December 2016.   This article incorporates text from this source, which is in the public domain.
  64. ^ "Air Force declares Nunn-McCurdy breach on GPS ground system". SpaceNews.com. 1 July 2016.
  65. ^ Insinna, Valerie (17 October 2016). "Raytheon's OCX Offering Survives Nunn-McCurdy Breach". DefenseNews. Retrieved 25 December 2016.
  66. ^ a b c Dunn, Michael (2 May 2022). "Directions 2022: GPS positioned for the future". GPSWorld.com. Retrieved 21 January 2023.
  67. ^ a b c d e "GPS Status and Modernization Progress: Service, Satellites, Control Segment, and Military GPS User Equipment" (PDF). US Air Force Space and Missile Systems Center. 26 September 2018. Retrieved 10 November 2018.   This article incorporates text from this source, which is in the public domain.
  68. ^ a b SMC Public Affairs Office (2 November 2017). "Air Force accepts delivery of GPS Next Generation Operational Control System". U.S. Air Force Space Command, Space and Missile System Center. Retrieved 3 December 2017.   This article incorporates text from this source, which is in the public domain.
  69. ^ "Directions 2022: GPS positioned for the future – GPS World". 2 May 2022.
  70. ^ Divis, Dee Ann (30 November 2016). "GAO: New GPS Ground System, Not GPS III Engineering, Primary Cause for Delays". InsideGNSS. Gibbons Media & Research LLC. Archived from the original on 2 December 2017. Retrieved 1 December 2017.
  71. ^ Divis, Dee Ann (27 April 2017). "OCX Passes Deep Dive Review; GAO Says Program Risk Remains High". InsideGNSS.com. Archived from the original on 28 April 2017. Retrieved 28 April 2017.
  72. ^ a b c "Counting 0, 1, 2, 3F: The Long Hello of GPS OCX". InsideGNSS.com. 6 May 2021. Retrieved 21 January 2023.
  73. ^ U.S. Space Force Space and Missile Systems Center Public Affairs (3 May 2021). "OCX 3F Contract Awarded to Raytheon Intelligence and Space". Retrieved 21 January 2023.
  74. ^ Seligman, Lara (3 March 2016). "Weapons Tester Warns of Risk to Air Force's GPS Contingency Plan". Defense News. Retrieved 25 December 2016.
  75. ^ "Next Generation Operational Control System (OCX) Selected Acquisition Report" (PDF). U.S. Department of Defense. 8 April 2022. Retrieved 21 January 2023.
edit
Library resources about
GPS Block III
  • Capozza, Paul T.; Betz, John W.; Fite, John D. (1 April 2005). "Getting to M". GPS World. Archived from the original on 9 July 2011.
Retrieved from "https://en.wikipedia.org/w/index.php?title=GPS_Block_III&oldid=1255018440"
  NODES
Association 1
COMMUNITY 1
Note 1
Project 8
USERS 5