I spent last week at Kitt Peak National Observatory assisting with the installation of the Dark Energy Spectrographic Instrument on the Mayall 4-meter Telescope. We spent a couple of months running the refurbished telescope through its paces on the sky with a simple commissioning camera and now it’s time to finish installing the complete instrument. As we get ready to install this complex array of 5000 robot-positioned fibers that feed ten spectrographs, I find myself thinking of the old saw “practice makes perfect.” Well, how exactly do you practice building and installing an instrument no one has built and installed before? As it turns out, there are ways to do this.
One of the major tasks this week has been “dummy” petal installation. The photo above shows a view of the 4-meter telescope from the top. We’re facing the primary mirror (which is covered with white covers that say “Danger: No Step”). In front of that, and right in front of the camera is the prime focus assembly. The 4-meter mirror focuses light into the prime focus assembly. In the old days, a camera sat there. Now there will be 5000-optical fibers aligned with objects on the sky by robot positioners. Those robot positioners are quite delicate and take up a lot of room, so a test petal has been created. The petals fit in the pie-shaped wedges you see in the photo. The dummy petal is the one with Swiss cheese, like holes. It’s carefully guided into position by the red mechanical assembly. Lasers are used to make sure the petal is positioned very carefully and put in at just the right place. Here’s what one of the real petals looks like.
The entire fiber petal sits in the silver box. The black structure on the right is the same size and shape as the Swiss cheese dummy petal. Behind that is a tightly packed array of delicate fibers. The real petal above will have to be placed precisely without breaking anything. So, in this case, we practice by creating a mockup to try out all the procedures and check that we know what we’re doing before we start installing all the really delicate, expensive instrumentation. There will be ten petals like the one in the photo above and light from their fibers will go down to ten spectrographs two floors below the telescope. We currently have six of those spectrographs installed in a clean room.
Currently, three of the spectrographs are in the lower layer of racks. Three are in the upper layer of racks. The spectrographs are where the real science happens. Light that comes down the fibers is spread apart into a literal rainbow and we can see the characteristic fingerprint of the chemical elements of the objects that each fiber in the spectrograph is pointed to.
The spectrographs and the petals remind us that practice makes perfect when you do things repeated times. We’re practicing with the dummy petal, but then we’ll install ten real petals. We’ve installed six spectrographs and we have four more to go. Each time we take another step forward, the easier the process becomes.
Of course, practice made perfect on our way to building these spectrographs in the first place. We built other, smaller fiber spectrographs and learned lessons from their construction. We’ve learned about robotics and we’ve learned lessons from other people who also work in the field by following their work.
Writing is much like this. You practice by doing. You might start with some short stories to get the hang of writing. Then you might try your hand at a novel chapter, then you’ll write another. All the while, you should keep reading to see what others are doing and have done. You’ll learn techniques as you try them out. You will likely encounter difficulties, but as you keep reading, you’ll be sensitive to those difficulties and you’ll see how others have solved them. This is just one of the ways that science has taught me to be a better writer and being a writer has taught me to be better at the science work I do.
You can learn more about my writing at http://www.davidleesummers.com
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