United States Armed Forces

====Missile warning====
{{main|Space Delta 4}}
[[File:STS-44 DSP deployment.jpg|thumb|Deployment of a [[Defense Support Program]] missile warning spacecraft from the [[Space Shuttle Atlantis|Space Shuttle ''Atlantis'']] on the [[STS-44]] mission]]

The Space Force's Space Delta 4 uses orbital spacecraft and ground-based radars to conduct theater and strategic missile warning for the United States and its international partners.<ref>{{cite web | url=https://www.spoc.spaceforce.mil/About-Us/Fact-Sheets/Display/Article/2334034/space-delta-4#:~:text=Space%20Delta%204%20(DEL%204,strategic%20and%20theater%20missile%20warning | title=Space Delta 4 }}</ref> This includes the network of [[Upgraded Early Warning Radar]]s at [[Beale Air Force Base]], [[Clear Space Force Station]], [[Cape Cod Space Force Station]], [[Pituffik Space Base]], and [[RAF Fylingdales]], along with the [[AN/FPQ-16 PARCS]] radar at [[Cavalier Space Force Station]].<ref>{{Cite news|url=https://www.raytheonmissilesanddefense.com/news/2022/09/16/all-five-uewrs-complete-second-generation-hardware-software-upgrades|title=All five Upgraded Early Warning Radars complete second generation hardware, software upgrades|date=19 September 2022|website=raytheonmisslesanddefense.com|url-status=dead|archive-url=https://web.archive.org/web/20221002201919/https://www.raytheonmissilesanddefense.com/news/2022/09/16/all-five-uewrs-complete-second-generation-hardware-software-upgrades|archive-date=2 October 2022}}</ref><ref>{{Cite web|url=https://www.afspc.af.mil/About-Us/Fact-Sheets/Display/Article/1126406/perimeter-acquisition-radar-attack-characterization-system/https%3A%2F%2Fwww.afspc.af.mil%2FAbout-Us%2FFact-Sheets%2FDisplay%2FArticle%2F1126406%2Fperimeter-acquisition-radar-attack-characterization-system%2F|title=Perimeter Acquisition Radar Attack Characterization System|website=Air Force Space Command (Archived)}}{{Dead link|date=August 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Currently the Space Force is working with the [[Missile Defense Agency]] to acquire the [[Long Range Discrimination Radar]] at Clear Space Force Station in Alaska. These ground-based radars also contribute to the Space Surveillance Network.<ref>{{Cite web|url=https://www.mda.mil/global/documents/pdf/lrdr.pdf|title=Long Range Discrimination Radar (LRDR), Clear Space Force Station (CSFS), Alaska|website=mda.mil}}</ref>

Space-based missile warning systems include the [[Defense Support Program]] and [[Space-Based Infrared System]] (SIBRS) spacecraft, which use infrared sensors to conduct missile defense and missile warning. SIBRS also has a battlespace awareness and technical intelligence mission.<ref>{{cite web | url=https://www.lockheedmartin.com/en-us/products/sbirs.html | title=SBIRS | date=9 August 2022 }}</ref> The Defense Support Program spacecraft are also capable of detecting nuclear detonations, in addition to space and missile launches.<ref>{{cite web | url=https://www.spaceforce.mil/About-Us/Fact-Sheets/Article/2197774/defense-support-program-satellites/ | title=Defense Support Program Satellites }}</ref>