R. Crouch, J. Oberling, I. Abouelfettouh, O. Patane

As Ibrahim reported here, we have completed the first round of BBS position alignment (I say first round as we still have to do the pitch/yaw alignment, and that has the potential to change the position alignment so we may be doing this again).  In the basis of our alignment equipment, which is set normal to the AR face of the BBS, the deviations from nominal are:

• Horizontal: +0.3 mm (right)
  • Tolerance: +/- 1.0 mm
• Vertical: -0.1 mm (low)
  • Tolerance: +/- 1.0 mm
• Longitudinal: +0.4 mm (long)
  • Tolerance: +/- 1.0 mm

If we rotate these deviations to the XYZ axes using the BBS yaw we get deviations along those axes.  I'm using the target BBS yaw for this (specifically, the AR surface yaw from the +X axis of 45.1056°), as we have yet to measure or align the actual BBS yaw, so this is more of an estimate at this point but will work for now (it takes a yaw change on the order of several degrees to change this calculation at the 0.1 mm level, so this is a pretty good estimate); this will be tightened up once we align the BBS pointing and revisit the positioning.  The results (the tolerances rotate with the deviations, hence the change in X and Y):

• X: -0.1 mm
  • Tolerance: +/- 1.4 mm
• Y: +0.5 mm
  • Tolerance: +/- 1.4 mm
• Z: -0.1 mm
  • Tolerance: +/- 1.0 mm

The below table gives the target position of the center of the BBS's AR surface and the current position based on the above estimate of the XYZ deviations (all units are in mm):

The next step in the alignment is to use the FARO to set up a total station/laser autocollimator combo looking along the target surface normal of the HR surface of the BBS.  This will be used to align the BBS pitch and yaw.  Once that is done we'll have to re-check the BBS position alignment (again, using the AR surface of the BBS) to ensure the pointing alignment did not change the optic's position (which may happen in this case as the BBS is currently, as Ibrahim reports, "quite yawed").