Persistent Surveillance is a term of art used by the military to describe the ability to surveill--or observe--changes on a landscape over time and make use of them in a networked environment.
In a 2002 interview, John Stenbit (who was at that time the U.S. Assistant Secretary of Defense for Command, Control, Communications, and Intelligence), described the distinct characteristics of persistent surveillance:
Stenbit emphasizes that persistent surveillance is not the same as constant surveillance. �The ability to observe everything continuously, all the time, would be awful,� he declares. �Who wants to see all the world all the time with enough resolution to find every person? What would we do with it?�
The defining concept of persistent surveillance is time. Someone observing a scene need not re-examine it any faster than the period of time in which changes take place. �We spend a lot of time taking pictures of radars and other electronics,� he notes. �But, as long as things don�t change, you don�t have to take another picture because you know everything that is there.�
It is when dealing with targets that do change that the observation interval must be coordinated with the frequency of those changes. �If what you�re interested in has time associated with it, unless you change the rapidity with which you come back and look, you are going to miss something. You will have a picture in your mind that is no longer true,� he states.