See pictures in album PR2 Remedying Work.

In order to have an accurate idea of how much we will need to move the GAS filter keystones up, I measured the height of the mirror under the following conditions:

• SF keystone locked at nominal height of 65.5 mm from the base plate per the 3D-CAD. I measured is indirectly with respect to another reference with a vernier calliper and then checked the height with a ruler. See this photo. The SF LVDT readout at this position was 1604.4 units (the LVDT doesn't seem to be calibrated properly).
• The BF keystone at the setpoint per the LVDT. This position is arbitrary becuase the LVDT doesn't seem to be calibrated.
• Laser level at the vertical centre of the flange.

The mirror was 6.5 mm below the centre of the flange.

Given this large difference I checked the relative position of other components:

• The RM, with respect to the security structure, is lower than the nominal height by 2.5 mm. The nominal value per the 3D-CAD is 31 mm (see this screenshot) and the measured value is 28.5 mm (see this picture).
• The security structure, with respect to the center of the flange, is lower than the nominal value by 3 mm. The nominal value per the 3D-CAD is 175 mm (see this screenshot) and the measured value is 178 mm (see this notebook page).

The values above add to 5.5 mm. There is 1 mm missing out of the 6.5 mm. Please note that the laser level line is around  2 mm thick as seen by the bare eye. In pictures the thickness may vary depending on the camera.

For the sake of gathering additional information I measured the height of the SF keystone when the LVDT readout was zero: 0.6 mm below the 65.5 mm level. See this notebook page for details.