 Knowledge of this guarantee was by the Swedish governments kept from the Swedish public until 1994, when a Swedish research commission found evidence for it.As part of the military cooperation the U.S. provided much help in the development of the Saab 37 Viggen, as a strong Swedish air force was seen as necessary to keep Soviet anti-submarine aircraft from operating in the missile launch area.In return Swedish scientists at the Royal Institute of Technology made considerable contributions to enhancing the targeting performance of the Polaris missiles.