With the detectors currently in operation, there are two possibilities to achieve the first direct measurement of gravitational waves: Either it so happens that, not too far away from Earth, there is a cosmic event producing strong gravitational waves, such as the merger of two black holes (the image shows a snapshot from a simulation). Or a computer-aided long-term analysis of detector data reveals the presence of a periodic wave signal, such as that of a rotating neutron star.
But even in the unlucky case of no direct detection within the next few years, today's detectors would serve their main purpose: as stepping stones towards the next generation of detectors. For Advanced LIGO, starting in 2007, the LIGO detectors are to be upgraded using advanced technology such as that already being used in GEO 600. Even by the most pessimistic estimates, cosmic events whose gravitational waves can be detected by these detectors of the second generation should happen several times a year.