A follow up from the alog17973

A HWS operates at 1Hz at the corner station and 57Hz at the End stations. The first plot attached is a quiet DARM and PEM magnetometer reference during a full interferometer lock when none of the HWS cameras were on. The second plot shows spectra from the same channels when only the ITM HWS were on. It is difficult to determine the 1-Hz line due to high DARM noise floor while there is no clear evidence in the corner station magnetometer channel. The third plot shows the DARM spectrum and the PEM floor magnetometer when both ITM abd ETM HWS were on. A tiny peak just above the noisefloor appears in the EX magnetometer together with a peak in DARM. The choice of the chosen magnetometer axis was arbitary. The last three plots are the trend of HWS camera switches.