Subspace Deformation Detection And Ranging (SUDDAR) is a long-range sensor system that is used as kind of a "subspace radar".
When Bob awakens in his replicant form, he is informed that science has made a breakthrough discovery in the early 22nd Century, which led to the development of both SUDDAR and the SURGE drive.
The SUDDAR systems that the Bobs use have an effective range of two to three light minutes.
The Others use a SUDDAR beam to transmit power to a drone. They also have a SUDDAR mega-ping that will light up everything, even a cloaked object, within a range of 2 light minutes.