Thursday, July 29, 2010

A target for squaring up the Rho ring

The alignment telescope & a large optical flat borrowed from Sunspace were used to check the performance of the stage assembly that will move the Apogee camera around the telescope's focal plane.  Some shimming & adjustment will be needed, but otherwise it all looks good.

Next, an alignment target needed to be placed on the tracker to allow us to get the Rho ring (to which the non-rotating structure, that will hold the SAC, is attached) squared up with the telescope's optical axis.  The CGH mount + tip/tilt & decentre actuator assembly was recycled for this purpose.

The mount + target was bolted onto the top of the payload.

In this CCAS tower view we see Charl sitting inside the non-rotating structure, ~13 m below us with the primary mirror a further 13 m below the tracker.  The mirror segments at the bottom of the array have been removed as a safety precaution in preparation for the SAC lift next week.

The alignment telescope in the CCAS tower had been set up on the central segment of the primary mirror so then the tracker was moved to its central position.  The Rho stage was rotated & with feedback from Darragh at the alignment telescope, Charl could mechanically adjust the target carrier. 

The target only had to be aligned with the telescope's cross hair to within the capture range of the target's actuator assembly - the fine adjustment will be done later with the precision stages.

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