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{{Short description|Anti-satellite weapons program of the U.S. military}}
{{More citations needed|date=February 2008}}

[[File:Program 437 Thor missile.jpg|thumb|Thor 278 missile, Johnston Island, Program 437]]
[[File:Johnston Island Layout Program 437.jpg|thumb|Program 437 layout on Johnston Island]]
[[File:Program 437 Layout.jpg|thumb|Program 437 Launch Site Layout]]
'''Program 437''' was the second [[Anti-satellite weapon|anti-satellite]] weapons program of the [[Military of the United States|U.S. military]].<ref name=Peebles>Peebles, Curtis. "High Frontier: The United States Air Force and the Military Space Program", 1997</ref> The US anti-satellite weapons program began development in the early 1960s and was officially discontinued on 1 April 1975. Program 437 was approved for development by [[United States Secretary of Defense|U.S. Secretary of Defense]] [[Robert McNamara]] on November 20, 1962, after a series of tests involving [[high altitude nuclear explosion]]s. The program's facilities were located on [[Johnston Island]], an isolated island in the north central [[Pacific Ocean]].

==History==
The US's first anti-satellite system was [[Program 505]], based at the [[Kwajalein Missile Range]], about halfway between Hawaii and the Philippine islands. This system became operational in 1962, based on the [[Nike Zeus]] [[anti-ballistic missile]] that had been tested at that site. These missiles had been modified for greater range, but even with these modifications the system could only intercept satellites that flew very close to the base, with a maximum altitude around {{convert|150|nmi}}. A system with longer range was an obvious requirement.

Program 437 was based on the much more powerful [[PGM-17 Thor|PGM-17]] [[Thor (rocket family)|Thor]] [[ballistic missile]]. It used Thor DSV-2E missiles armed with a [[W49]] or [[W50 (nuclear warhead)|W50]] [[nuclear weapon]], which would destroy or disable targets through [[nuclear explosion]] or the resulting [[electromagnetic pulse]]. Eight Thor DSV-2E missiles were launched between May 2, 1962, and November 1, 1962. Though the program would routinely run successful tests with unarmed Thor missiles, the only high altitude nuclear explosions were conducted through Operations [[Operation Argus|Argus]], [[Operation Hardtack I|Hardtack I]], and [[Operation Dominic|Dominic]]/[[Operation Fishbowl|Fishbowl]] between 1958 and 1962. Operation Argus operated out of the South Atlantic, while Hardtack and Dominic conducted their high altitude tests from the Johnston Island facilities. "Tightrope" was part of "Fishbowl" but was a lower altitude detonation.<ref name="afspacemuseum.org">{{Cite web|url=http://afspacemuseum.org/johnston/|title = Air Force Space & Missile Museum}}</ref>

Some results of these tests, Dominic's 1962 [[Starfish Prime]] test in particular, presented concerns throughout the program's existence. In addition to the widespread effects of the nuclear explosion's electromagnetic pulse, which inadvertently damaged many [[satellite]]s as well as land based electronics as far as {{convert|1500|km}} away, a large amount of [[charged particle]] radiation was released by the nuclear explosion. This radiation became trapped by the [[Earth's magnetic field]], creating artificial belts of radiation 100 to 1,000 times stronger than [[background radiation|background levels]]. The heightened levels of radiation eventually crippled one-third of all satellites in low orbit, while rendering seven others completely useless, including the first commercial [[communication satellite]] ever, [[Telstar]].

It was eventually concluded that the due to the wide radius of damage, wartime deployment of Program 437 would result in indiscriminate destruction of friendly and enemy satellites, potentially destabilizing or escalating otherwise non-nuclear conflicts. In addition to these problems, the [[Soviet Union|Soviet]]s deployed numerous [[military satellite]]s, making specific targeting impractical or ineffective. Furthermore, the [[United States Air Force]] had a limited supply of Thor missiles, and all military resources (especially financial) had become increasingly strained with the US involvement in the [[Vietnam War]].

In October 1970, the [[United States Department of Defense|Department of Defense]] transferred Program 437 to standby status as an economic measure. Test launches were no longer run, and the weapons system would take fourteen to thirty days to intercept targets, requiring components stored at [[Vandenberg Air Force Base]] to be [[airlift]]ed by a [[C-124 Globemaster II]] to Johnston Island for deployment. These obstacles further degraded the weapon's suitability and effectiveness for war.

Part of Program 437 was '''437 Alternate Payload (AP)''' which was used for satellite inspection. Thor DSV-2J missiles were used for the 437 Alternate Payload program. Eighteen DSV-2J Thors were launched from the Atoll between February 14, 1964, and November 6, 1975.<ref name="afspacemuseum.org"/>

===Demise===
On 19 August 1972, [[Hurricane Celeste (1972)|Hurricane Celeste]] destroyed most of the facilities and guidance [[computer]]s at Johnston. Though the systems were able to be restored by September 1972, unspecified damage caused them to fail on 8 December. The program became fully repaired and restored by 29 March 1973, and remained in standby status until the anti-satellite mission on the Johnston Island facilities were ceased on 10 August 1974. Program 437 was officially terminated on 6 March 1975 at the request of [[NORAD]], and on 1 April 1975 the [[United States Department of Defense|Department of Defense]] terminated funding for any anti-satellite programs or development. In January 1977, at the end of his term of office, then [[President of the United States|President]] [[Gerald Ford]] issued a directive for the DoD to again enter research and development on an operational anti-satellite program. It was an order his successor, President [[Jimmy Carter]], followed through on, and anti-satellite technology has continued to be in some form of research or development since.

==Operations==
Two missiles were kept on alert at Johnston Island, and two were kept in war reserve at [[Vandenberg AFB]], [[California]].<ref name=Peebles/>

Program 437 Thors could intercept [[low Earth orbit]]ing satellites up to an altitude of {{convert|700|nmi|km}} and a cross-range distance of {{convert|1500|nmi|km}}. Two missiles were readied for launch, one as primary launcher and the other as a hot back-up in case of primary failure. Launch windows were as small as one second, also necessitating the dual missiles. Once the missile's trajectory hit the target's orbital path, the one megaton Mark 49 warhead would explode, setting off a blast radius of {{convert|5|mi|km|spell=in}}.

==Chronology==
*1964
**28 May - first Combat Training Launch (CTL)
**29 May - Program 437 declared Initial Operating Capability (IOC)
**10 Jun - Program 437 declared Full Operating Capability (IOC)
**20 Sep - President Lyndon Johnson reveals existence of Nike-Zeus and Program 437 anti-satellite weapons during campaign speech
*1965
**7 Dec - first 437AP launch
*1966
**18 Jan - second 437AP launch (successful)
**12 Mar - third 437AP launch (successful)
**Late 1966 - [[Air Defense Command]] and [[Air Force Systems Command]] plan for ten 437AP launches, under Program STONE MARTEN
**30 Nov - Program 437AP is formally cancelled by Headquarters USAF
*1967
**31 Mar - CTL conducted
*1968
**14 May - CTL conducted
**20 Nov - CTL conducted
*1970
**27 Mar - Final Program 437 CTL launched
**4 May - Deputy Defense Secretary David Packard directs the Air Force to accelerate the phase down of Program 437 to standby status by end of fiscal year.
*1972
**19 Aug - Hurricane Celeste hits Johnston Island, damaging Program 437 launch facilities and computers
*1975
**1 Apr - Department of Defense officially terminates Program 437

==Photo gallery==
<gallery>
File:Program 437 1.PNG|Program 437 Thor at SLC-10W
File:Program 437 2.PNG|Program 437 Thor at SLC-10W
File:Program 437 3.PNG|Program 437 Thor at SLC-10W
File:Program 437 4.PNG|Program 437 Thor at SLC-10W
File:Program 437 Tech Order Cover.jpg|Program 437 Technical Order ("Dash-1") cover
File:Thor missile at Johnston Island.jpg|PGM-17 Thor missile at Johnston Island
File:Bluegill Prime Thor Missile Explodes.JPG|Thor missile launch failure and explosion contaminates Johnston Island with Plutonium during the Operation "Bluegill Prime" nuclear test, July 25, 1962
File:Contaminated Johnston Island Launch Emplacement 1, Bluegill Prime, Thor failure, July 25, 1962..jpg|Johnston Island Launch Emplacement 1, contaminated during Thor missile launch failure, Operation Bluegill Prime, July 25, 1962.
File:Dominic Bluegill Prime radiation cleanup.jpg|Inspection of Thor rocket engine remains after failure of Bluegill Prime nuclear test attempt on 25 July 1962.
</gallery>

==See also==
*[[10th Aerospace Defense Squadron]] and [[10th Aerospace Defense Group]] - operators of Program 437
*[[Fractional Orbital Bombardment System]] – the Soviet orbital nuclear missile system, deployed operationally 1969–1983
*[[Nuclear weapon delivery systems]]
*[[Outer Space Treaty]]

==References==

{{Reflist}}

==Notes==
* {{cite book |url=http://handle.dtic.mil/100.2/ADA377346 |archive-url=https://web.archive.org/web/20160919150617/http://handle.dtic.mil/100.2/ADA377346 |url-status=dead |archive-date=September 19, 2016 |title=Shooting down a star: the US Thor Program 437, nuclear ASAT, and copycat killers |last=Chun |first=Clayton K. S. |year=1999 |publisher=Air University Press |isbn=1-58566-071-X |access-date=15 September 2016}}
* {{cite web |url=https://www.dtra.mil/Portals/125/Documents/NTPR/newDocs/18-DOMINIC%20I%20-%202021.pdf |title=Operation DOMINIC I |publisher=[[Defense Threat Reduction Agency]] Department of Public Affairs |date=September 2021 |access-date=9 February 2006}}
* {{cite web |url=http://www.redstone.army.mil/history/hardtack/welcome.html |archive-url=https://web.archive.org/web/20101105015135/http://www.redstone.army.mil/history/hardtack/welcome.html |archive-date=5 November 2010 |title=Operation Hardtack |publisher=[[United States Army]] |access-date=8 February 2006}}
* {{cite book |url=http://jya.com/sh/shall.htm |archive-url=https://web.archive.org/web/20080924110524/http://jya.com/sh/shall.htm |archive-date=24 September 2008 |title=Space Handbook: A War Fighter's Guide to Space |volume=One |last1=Muolo |first1=Major Michael J. |last2=Hand |first2=Major Richard A. |publisher=[[Air University (United States Air Force)|Air University]] [[Air Command and Staff College]] |date=December 1993 |access-date=9 February 2006}}

[[Category:American nuclear weapons testing]]
[[Category:Anti-satellite missiles]]
[[Category:United States government secrecy]]

Program 437 - Revision history

imported>Citation bot: Added publisher. | Use this bot. Report bugs. | Suggested by Abductive | Category:Articles needing additional references from February 2008 | #UCB_Category 494/913