I don't think unshielded nukes in orbit are easy to detect. Back on Earth you need to get up close (within a few meters) in order to distinguish the radiation s

I don't think unshielded nukes in orbit are easy to detect. Back on Earth you need to get up close (within a few meters) in order to distinguish the radiation signature from the background radiation, and in space the background level is much higher. Source: https://fas.org/sgp/crs/nuke/R40154.pdf https://fas.org/sgp/crs/nuke/R40154.pdf (see page 78 and onwards for a discussion about detecting nukes at a distance)