What purpose do intelligence-gathering ships serve in the twenty-first century, and what specifications should modern or future vessels have?
Short answerThe mission determines the ship: electronic surveillance needs antennas, close-coast survey favors expendable uncrewed craft, and satellite monitoring requires large specialist sensor ships.
NotesAn intelligence vessel should be designed around the information it must collect. Electronic surveillance can be performed by ordinary ships with capable antenna masts, since they can gather emissions without a dedicated hull. Risky coastal survey favors expendable uncrewed surface craft that can stream data back while operating close inshore. Watching satellites over the open ocean demands a much larger specialist ship with powerful radars and supporting systems. Electronic intelligence can require deciphering extremely weak emissions by the time they reach the listening ship.