Keita, Aidan (remotely), TVo

The odd noise that has been tricking the ITMX HWS software's calculation of the spherical power seems to come from some sort of dead pixel.  In the attached screenshots, the large gradient vector in the upper section comes from a place where there isn't a physical hole from the Hartmann plate which gets included in the calculation for the spherical power.

• The upper right image in the attachment is an overlay of the gradient field, the raw image with the plate on, and the raw image with the plate off.  This shows that the large gradient vector is not located at a place which shows clipping but rather, in a place which seems like a bad pixel.  The dark brown area is from the aperture of the SR3 baffle.
• The lower right image shows a "pinching" effect in the integrated wavefront.
• The upper left image is the plot of the centroid field which is determined by the Hartmann code and used to calculate the polynomial coefficients which get turned into the Seidel coefficients which then get converted into a spherical power. 
• The lower left image is the gradient field when no heating is applied and clearly shows the outlaying large gradient vector and a few others which seem to come from dead pixels. 

According to Aidan, Adelaide has started to develop some code that will identify dead pixels so maybe we can implement it at the sites soon.  As a side note, it is unclear whether or not the tight aperture that the beam goes through will drastically affect the overall sensitivity but maybe we won't know until we try measuring the self-heating from the absorption of the IFO beam and see the overall noise in our estimates.