2005: S4 from February 22 to March 24
From February 22 to March 24 GEO600 and all three LIGO detectors have performed the fourth science run (S4). As for GEO, 30 operators in 58 shifts supervised the performance of the detector. If necessary, they could ask for help six 'experts' on site or on call, those people who managed to increase the sensitivity of GEO in order to make this run possible (Harald Lück, Martin Hewitson, Joshua Smith, Stefan Hild, Hartmut Grote, Benno Willke). There was one almost sleepless night, but no driving to the site at night was required.
The detector turned out to be very stable, with a duty cycle of about 97%; the longest lock was nearly 53 hours. Most disturbances came from the occasionally very strong wind, from a tractor tilling the ground between north and east end house, and from several earthquakes. The typical re-lock time was below 3 min.