A Rare Optical Alignment!

The first day of work in 2017 at the Richard F. Caris Mirror Lab and what should I find, but a first-ever (that I'm aware of) alignment of the first 3 mirrors of the Giant Magellan Telescope! There are 4 mirrors in various stages of completion in the lab, but today GMT1 was moved from the test tower where it has resided over the holiday shutdown, out into the integration lab while both machines are undergoing some upgrades. So as seen at left, from right-to-left are GMT1, GMT2, and GMT3!

GMT1, the blue-colored one at right is finished, but will likely serve as reference to measure all the other mirrors, so may be the last to be delivered! It has a brush-on blue coating to protect the finely-polished surface.

The center mirror (with Leslie standing in front for scale!) is GMT2 and is diamond generated and awaiting fine-abrasive lapping and polishing. In the rear is GMT3 - currently face-down, with rear work of applying load-spreaders and thermocouples complete. It will soon be flipped over and work started on the front concave surface.

All of these mirrors are our standard-size 8.4 meter diameter substrates. That converts to nearly 28 feet in diameter. If you go to the GMT website above, that telescope will consist of 7 of these mirrors combining to form a single HUGE telescope... As seen at left, these 3 mirrors nearly fill the integration lab completely, with barely room to walk between them. You can see that both polishing cells are nearly identical, with a plumbing skirt to contain polishing and generating fluids around the outside. Visible on the GMT2 cell at left is the inflatable pressure seal at the backplate which allows pressurizing the cell plus mirror to match the polishing pressure to reduce print-through in the finished mirror surface.

And some of you may well wonder why the rear of the GMT3 mirror is covered with foam. Nothing secret certainly, just protecting the rear surface with the now-attached load spreaders which will interface with the supports in the polishing cell and the eventual telescope cell. At left I've pulled back one of the foam sheets to show loadspreaders and the thermocouple wiring so that mirror and air temperatures can be monitored during polishing or in the telescope.



And just because it is MY blog, here are some 3D anaglyphs! Grab your red/blue 3D glasses and enjoy the following shots. By adding another shot an inch or two away from the loadspreader shot above, you can make the 3D shot at left.

And while I was on a ladder taking the above shots, Looking back across the lab, I took another stereo pair of GMT1 and GMT2, shown at right.

We're continuing machine upgrades, and need to run some experiments to checkout machinery and software before continuing work on the GMT mirrors. Stay tuned!