Hugh, Jim, Krishna

This is regarding the idea of placing a seismometer on the BRS-Y platform in order to improve coherence and hence tilt-subtraction. The brief summary is that we found excess low-frequency noise in the seismometer when it was placed on the table on BRS-Y. Hugh had attempted to reduce the noise by adding thermal insulation to the table and the instrument. The last alog on this is 35426.

In the recent data I looked at, this excess noise looks non stationary - it seems to get worse with elevated wind. This suggests it is likely not thermal. The seismometer data shows that the table has much higher motion in the 10-100 Hz as compared to the ground. Since the seismometer isn't held securely on the table, it is possible this excess high-frequency motion is causing it to move ever so slightly, which could look like excess low-frequency noise (step changes). We are attempting to mount the seismometer securely to the table using M10X1.0mm threaded rods and holes to be machined into the table. Results and plots will be posted in a few days.