I won't say modern submarines can or cannot be detected from space, but this should give you some ideas about what is publicly known: https://duckduckgo.com/?q=

I won't say modern submarines can or cannot be detected from space, but this should give you some ideas about what is publicly known: https://duckduckgo.com/?q=spotting%20submarines%20using%20magnetic%20fields%20&t=fpas https://duckduckgo.com/?q=spotting%20submarines%20using%20ma... This is fairly open secrets to the degree that it is secret at all so it probably also is no big secret that passive and active countermeasures are used to prevent these techniques.