When re-locking after maintence day today, we have what looks like large scattering shelves in DARM (starting around 2:03 UTC march 6th).  

Update: I accidentally increased the gain in the OMC ASC loops during maintence today, which caused large scattering shelves.  We can use this data to estimate scatter noise from the OMC for normal ASC drive levels. 

While looking for the cause of the large scattering shelves, we also found that turning off the cut-off filter for MICH P greatly reduced the scatter, and the 0.5Hz noise in our ASC signals.   After reducing the OMC ASC gains, we tried to engage the MICH P low pass again, which caused a large scattering shelf, and caused the ASC signals to ring up.  

The high gains were on in lock from about 2:30 UTC until about 9:05 UTC on March 6th.  The MICH P low pass was off from 8:13 UTC to 8:43 UTC, while the OMC ASC was still in high gain.  This would be a good time to use to estimate the ambient level of the scatter.