After almost four decades under US administration as the easternmost part of the UN Trust Territory of the Pacific Islands, the Marshall Islands attained independence in 1986 under a Compact of Free Association. Compensation claims continue as a result of US nuclear testing on some of the atolls between 1947 and 1962. The Marshall Islands hosts the US Army KwajaleinAtoll Reagan Missile Test Site, a key installation in the US missile defense network. Kwajalein also hosts one of four dedicated ground antennas (the others are on Ascension (Saint Helena, Ascension, and Tristan da Cunha), Diego Garcia (British Indian Ocean Territory), and at Cape Canaveral, Florida (US)) that assist in the operation of the Global Positioning System (GPS) navigation system.