Below is a listing of the ten launch missions involving the first ten GPS III series satellites showing the space vehicle number, launch date, the interval between missions, the launch provider, and the booster rocket used. The space vehicle number is a hyperlink to more details about the launch.
GPS III Launch Dates / intervals / provider / booster
SV-01 23 Dec 2018 day-0 SpaceX Falcon 9
SV-02 22 Aug 2019 303-days ULA Delta IV Medium
SV-03 30 Jun 2020 313-days SpaceX Falcon 9
SV-04 05 Nov 2020 129-days SpaceX Falcon 9
SV-05 17 Jun 2021 225-days SpaceX Falcon 9
SV-06 18 Jan 2023 581-days SpaceX Falcon 9
SV-07 16 Dec 2024 699-days SpaceX Falcon 9 (originally ULA Vulcan)
SV-08 30 May 2025 165-days SpaceX Falcon 9 (originally ULA Vulcan)
SV-09 27 Jan 2026 242-days SpaceX Falcon 9 (originally ULA Vulcan)
SV-10 21 Apr 2026 60-days SpaceX Falcon 9 (originally ULA Vulcan)
The significant speed-up in the pace of GPS III launches for the last four spacecraft--four launches in a span of just 467-days--is no doubt a reaction to the use of GNSS jamming in the Middle East and Ukraine as a result of war and hostilities in those regions. The GPS III satellites transmit stronger and more robust signals that improve resistance to jamming, particularly for USA forces that are able to use encrypted signals from the satellites.
The original contract arrangements called for SpaceX and ULA (United Launch Alliance) to share the ten GPS III mission, but delays in the readiness of the ULA Vulcan booster rocket resulted in SpaceX performing nine of the ten missions. A number of launch missions originally assigned to ULA were changed to SpaceX due to delays in the ULA booster or concerns about its performance.
The only GPS III series ULA launch mission used their legacy but very expensive Delta IV Medium booster. Another ULA rocket, the Atlas 5, uses Russian-made first stage RD-180 engines. In 2019 a 2015 federal law banning use of Russian-made rocket engines for Air Force space missions came into effect, effectively preventing ULA from using the less expensive Atlas 5 for GPS missions. The ban on Russian engines was a reaction to the Russian invasion and war against Ukraine. ULA was in the process of developing their Vulcan booster rocket, but the Space Force was not confident about using it for launching mission-critical and very expensive (about $600-million each on average) GPS III spacecraft.
The GPS III F (follow-on) spacecraft are now in production at contractor Lockheed-Martin, and the first launch is anticipated for the third quarter of 2028. The first two launch missions for GPS III F satellites have been allocated to ULA and their Vulcan Centaur VC2S booster. The third and fourth missions will be launching a slightly different GPS III F spacecraft, which will use a new platform LM2100 Combat Bus, which is perhaps why they are are planned for the more powerful Vulcan Centaur VC4S booster.
Of significance to boaters, the GPS III F series will include a receiver and relay transmitter for the COPAS SARSAT rescue system. For more information about the MEO satellites in the SARSAT system, see
SARSAT MEO 406-MHz Systems on GPS Satellites
https://continuouswave.com/forum/viewto ... 52&p=16842
and
SARSAT MEO 406-MHz System on GALILEO FOC Satellites
https://continuouswave.com/forum/viewto ... 51&p=29270
The inclusion of return channel capability in the SARSAT payload for the GPS III satellites in not known at this time.