Virgo Logbook

As observed by Shourov, the dark fringe shows some large glitches every 5000 seconds. Attached figure shows a zoom of the suspension signals for one of the events, which shows a clear glitch at the WE. This is caused by one sample that is send by Gc (Gc_WE_z) but never received by the DSP (Sc_WE_zGc), it probably got lost somewhere in the 1500m west building.

This problem looks very similar to some glitches seen earlier at the NE, except for the fact that they appear at a regular interval. Is there some counter inside the DSP or the DOL which has a period of 5000 seconds? And why is there still a 5 kHz oscillation?