Editing UGM-27 Polaris (section)

=== Chevaline ===
{{Main|Chevaline}}
[[File:Polaris missile launch from HMS Revenge (S27) 1986.JPEG|thumb|A Polaris missile is launched by {{HMS|Revenge|S27|6}} in 1986]]
The original U.S. Navy Polaris had not been designed to penetrate [[anti-ballistic missile]] (ABM) defenses, but the Royal Navy had to ensure that its small Polaris force operating alone, and often with only one submarine on deterrent patrol, could penetrate the ABM screen around Moscow. Britain's submarines featured the Polaris A3T missiles, a modification to the model of the Polaris used by the U.S. from 1968 to 1972. Similar concerns were present in the U.S. as well, resulting in a new American defense program.<ref>{{cite journal |last1=Parr |first1=Helen |title=The British Decision to Upgrade Polaris, 1970–4 |journal=Contemporary European History |date=May 2013 |volume=22 |issue=2 |pages=253–274 |id={{ProQuest|1323206104}} |doi=10.1017/S0960777313000076 |s2cid=163187309 }}</ref>

The program became known as Antelope, and its purpose was to alter the Polaris. Various aspects of the Polaris, such as increasing deployment efficiency and creating ways to improve the penetrative power were specific items considered in the tests conducted during the Antelope program. The British's uncertainty with their missiles led to the examination of the Antelope program. The assessments of Antelope occurred at [[Aldermaston]]. Evidence from the evaluation of Antelope led to the British decision to undertake their program following that of the United States.<ref name=":0" />

The result was a programme called ''[[Chevaline]]'' that added multiple decoys, [[Chaff (radar countermeasure)|chaff]], and other defensive [[countermeasure]]s. Its existence was only revealed in 1980, partly because of the cost overruns of the project, which had almost quadrupled the original estimate given when the project was finally approved in January 1975. The program also ran into trouble when dealing with the British [[Labour Party (UK)|Labour Party]]. Their Chief Scientific Adviser, [[Solly Zuckerman, Baron Zuckerman|Solly Zuckerman]], believed that Britain no longer needed new designs for nuclear weapons and no more nuclear warhead tests would be necessary. Though the Labour Party provided a clear platform on nuclear weapons, the Chevaline program found supporters. One such individual who supported modification to the Polaris was the Secretary of State for Defence, [[Denis Healey]].<ref name=":0">{{cite journal |last1=Spinardi |first1=Graham |title=Aldermaston and British Nuclear Weapons Development: Testing the 'Zuckerman Thesis' |journal=Social Studies of Science |date=August 1997 |volume=27 |issue=4 |pages=547–582 |doi=10.1177/030631297027004001 |jstor=285558 |s2cid=108446840 }}</ref>

Despite the approval of the program, the expenses caused hurdles that augmented the time it took for the system to come to fruition. The cost of the project led to Britain's disbanding the program in 1977. The system became operational in mid-1982 on {{HMS|Renown|S26|6}}, and the last British [[SSBN]] submarine was equipped with it in mid-1987.<ref>[http://nuclearweaponarchive.org//Uk/UKArsenalDev.html History of the British Nuclear Arsenal], Nuclear Weapons Archive website</ref> Chevaline was withdrawn from service in 1996.

Though Britain adopted the Antelope program methods, no input on the design came from the United States. Aldermaston was solely responsible for the Chevaline warheads.