I've not blogged about the Mirror Lab in an age, so after this, you will officially be up to date! It has been over 2 months (!) since last blogging about the Large Synoptic Survey telescope (LSST). We at the Mirror Lab (Steward Observatory Mirror Lab ) are working on the primary mirror fabrication, and since the last post on 20 February, we've finished the backplate generation to the proper thickness, edged the mirror to the proper outer and inner diameter, polished edges and fine ground the bevels and boss reference surfaces. All that is left before loose abrasive grinding and polishing is to machine 24 of the backplate holes for stress relief.
The LSST Telescope is unlike any other telescope in a number of ways. The most important point for the tasks at hand is that after the brief sky exposures, the telescope has only a few seconds to reposition to it's new location in the sky as the previous exposure downloads from the 3.2 gigapixels. The potentially large sky movements in a few seconds puts huge loads and stresses into the telescope and mirror, and as a result, the hard points defining the mirror position must be as strong and stress-free as possible. A mill head has been mounted to the Large Optical Generator (LOG), and with an assortment of diamond tools we are attacking the backplate. The crew and I are going through the 6 areas where the hard points will be mounted, cleaning up the as-cast backplate holes and generating radii into the extra-thick cast backplate (for extra strength). With 6 locations and 4 backplate holes per location, and several hours per hole, nearly a couple weeks will be required for this work before moving on to conventional grinding and polishing of the rear surface.
The coolest part is that they've installed a webcam to either monitor progress or keep an eye on the employees! You can check in to see what is happening real time in the lab by going here. You should see an image update every 2 seconds. I'm currently working 6am till something after noon (Mountain Standard), at which time the second shift comes in till about 8pm. Of course, most everyone is off weekends, and I'll also be gone early next week with Melinda for a short Midwest trip. But do check in and at least wave to me if I'm there working hard!
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