Spy Ship - Operation

Operation

A spy ship usually stays in international waters (or at least outside of territorial waters), so as to not violate territorial borders. From there, it will use its electronic equipment to monitor sea and air traffic, radio and radar frequencies and also try to intercept and decrypt coded radio or phone communications. This is mostly done via passive means such as radio receivers or passive sonar. Sometimes however, active measures such as radar or sonar may also be used to detect the movement of aircraft, missiles, ships or other vehicles or troops. However, this risks revealing the ship's purpose.

As it is located much closer to the surveilled area than a fixed installation (given a close-by shoreline), the monitoring is usually much more efficient and in some respects better than even that of spy satellites.

Tracking vessels for space missions/control stations for satellites/spy satellites also have some of the capabilities of spy ships, and as they are controlled by their national governments, they are also intermittently used for similar purposes, such as tracking enemy missile tests.