The Russian nuclear-powered submarine Kazan, part of the Russian naval detachment visiting Cuba, leaves Havana Harbour.YAMIL LAGE/AFP via Getty ImagesRussian submarines have recently been spotted in Cuba and the Baltic Sea.US and allied anti-submarine warfare planes can collect valuable information on these vessels.Building an acoustic profile of the submarine can help make it easier to identify and track them.Russian submarines have surfaced on the doorsteps of the US and other NATO allies in recent weeks.