Troubleshooting

My friend Darla Hallmark sells buttons that say, “The problem with troubleshooting is that trouble often shoots back.” In my job operating telescopes at Kitt Peak National Observatory, I often get to see the truth of that statement. Here I am in my natural habitat at the control station of the WIYN telescope.

My actual title at Kitt Peak is “Senior Observing Associate” and my job is more than being a telescope driver. I see myself as the person whose job it is to make sure the astronomers who use the telescopes actually get the data they hope to obtain. At night, especially at the WIYN telescope, I’m often the only person in the building. It’s quite common for observers using the telescope to control the cameras over the internet and talk to me all night on a Skype connection.

The observatory has a daytime staff of engineers, electricians, mechanics and more. Most of them are tucked snug in their beds when I’m working through the night. So, if something goes wrong, I’m the guy who has to fix it, or find a workaround until the next day when the daytime staff returns to work. I think its a real testament to the design and maintenance of the telescopes at Kitt Peak that serious problems don’t crop up all that often, but when they do, they can be a challenge.

We had one such problem this week at WIYN. We were using the Hydra spectrograph. Instead of an eyepiece or a camera looking directly at the sky, there is a metal plate. Fiber optics in magnetized housings sit on that metal plate and face the sky. A robot within Hydra can move those around so they’re in a position to capture light from distant objects. This week, each fiber was placed to catch light from galaxies approximately 11 billion light years away. As you can imagine, you need to place that fiber in just the right place to catch that tiny bit of light. This is what the inside of the Hydra spectrograph looks like. You can see the fibers on the left-hand side. The robot that moves the fibers is on the right.

The problem we had was that some of these fibers were missing the light. To confuse matters, not all the fibers were missing the light. We saw light from some galaxies. We saw light from all the stars that let us do fine corrections to our pointing on the sky. My first thought was that there was a calculation error and not all the fibers were being placed correctly. The astronomer looking at these galaxies checked and eliminated that possibility. Next, we used a camera on the robot to watch the fibers as they were being moved to see if they were being placed where we put them. The robot did just what it was supposed to do.

The final step in this procedure is that the metal plate on the left gets warped, because the telescope’s focal plane isn’t actually flat. We watched the fibers as the plate was warped. The fibers in the center “jumped.” That’s not supposed to happen. As of this writing, I’m not sure why warping the plate made some fibers jump but not others, but the obvious workaround is not to warp the plate. What this means is that some galaxies will be better focused than others, when we take data, but since we’re taking spectra, that’s not a showstopper. We just care that the light makes it down the fiber. Once that happens, the astronomer can see what elements exist in that galaxy and get information about how far away it is and how fast its moving. As the weeks goes on, that team of engineers and technicians will take the information I learned about the problem and work to find a solution.

If you enjoyed this behind-the-scenes look at my job operating telescopes, you might enjoy my novel, The Astronomer’s Crypt. It tells the story of ghosts, gangsters, astronomers, and a dangerous Apache spirit colliding at a New Mexico observatory on a dark and stormy night. You can learn more about the novel and watch a cool trailer at: http://www.davidleesummers.com/Astronomers-Crypt.html.

If spooky stories aren’t your thing, but you’ll be in Phoenix, Arizona on Thursday, May 9, you can join me at the next meeting of the Phoenix Astronomical Society, where I’ll be talking about the DESI project on the Mayall 4-meter telescope and sharing some behind the scenes photos of the installation. You can get more details about the meeting at: http://www.pasaz.org/index.php?pageid=meetings

2 comments on “Troubleshooting

  1. Jack "Blimprider" Tyler says:

    A. As a lay-science nerd (big fan of the Anton Petrov channel), I always enjoy reading about what you’re up to there.

    B. All fans of thinking man’s horror are directed to read The Astronomer’s Crypt forthwith. With isolation, ghoulies, criminals, atmosphere, and unlikely heroes, this is likely to be one of the best books you read this year and maybe next!

    C. What are you people looking at now? The information I get from casual studies tells me that Earth sits at the center of an observable sphere with a 13.8 billion light year radius, so am I to assume there is a conspiracy afoot to keep us amateurs from knowing the true size of the universe, and you’ve just let something slip? Please say no; if my son has to take one more conspiracy theory aboard, his head will explode!

    • Many thanks, Jack, and as always, a delight to hear from you. It may come as a surprise, but the size of the universe in light years is not a number I carry around with me — and I suspect it’s a number that most astronomers don’t carry around with them unless they’re giving talks or lectures on the subject. Mostly we speak in terms of “redshift” which is a directly measurable number. The “radius” you give comes with some assumptions, including the expansion rate of the universe, but given our understanding of the expansion of the universe, that’s about the right number. (And I’ll note that is the the distance of the “observable universe” — the point at which light is actually free to move.)

      The astronomer I was working with told me she was observing galaxies at redshift 3. Because it’s been a while since I’ve had a reason to convert redshift to light years, so I went to one of many cosmology calculators that astronomers have posted on line. In short, I goofed and posted the wrong number. The 84 billion light year distance I gave is the “apparent luminosity distance.” Basically, it’s the distance you would get if all you know is the luminosity of the galaxy and assume light takes zero time to travel and the universe is not expanding. In short, it’s the distance you would get if you compared the brightness of the galaxy to the brightness of the same type of galaxy right next door.

      The more correct distance factors in light travel time and the approximate expansion rate of the universe. That’s how you get 13.8 billion light years to the edge of what can be observed. I have corrected the number to 11 billion light years, which is the number you get if you take the factors into account.

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