Refitting the Mayall: Teardown

I was in 8th grade when Star Trek: The Motion Picture came out. One of the things that fascinated me in that movie was the refit of the Starship Enterprise. I was captivated by how the ship looked at once much the same and yet completely different. It looked sleeker and more powerful and familiar space on the ship such as the bridge, sickbay, and the transporter room had all been updated. I’m getting to experience something much like the Enterprise refit in real life. In this case, I’m involved in refitting the Mayall 4-meter telescope at Kitt Peak National Observatory.

Like the Starship Enterprise, the Mayall has a forty-five year history of discovery. Originally built to use photographic plates, the telescope has played an important role in such discoveries as establishing the role of dark matter in the Universe from measurements of galaxy rotation, and determining the scale and structure of the Universe. Over the years, new instrumentation has been added to the telescope including advanced digital cameras and spectrographs.

The purpose of the refit is to install a new instrument called DESI, which stands for Dark Energy Spectroscopic Instrument. 5000 optical fibers will be installed at the telescope’s prime focus (the top end of the telescope) and run to cameras in another room. The goal is to observe tens of millions of galaxies and quasars, constructing a three-dimensional map spanning the nearby universe to 10 billion light years.

In order to achieve this goal, the entire top end of the telescope has to be replaced and much of the control software and electronics are being redone so that it’s truly state of the art. To achieve this goal, we literally have to gut the telescope and install new components from the inside out. During my most recent shifts at the telescope, I’ve been involved in just that. In the photo to the right, you can see that the bottom of the telescope is missing and replaced with scaffolding. That’s because the large 4-meter mirror is out for recoating. Also, all the optics are missing from the secondary mirror assembly at the top of the telescope. Ultimately, that will be removed completely and replaced with a new secondary ring. The men in the photo are removing a counterweight assembly used to precisely balance the telescope when instruments are added and removed. Electrical panels are open on the side of the telescope where control cabling going back to the photographic days will be removed and replaced with new control cabling. Modern electronics mean the telescope will have about 10% of the cables as it did when originally built!

The refit has also allowed me a rare opportunity to see parts of the telescope I’ve never been to before, even after operating it for some thirteen years. Earlier this week I got to help the electronics technicians work on some cabling in the “horseshoe.” That’s the big, blue horseshoe-shaped mount you see in the photos above. We actually ended up working down in the broad, blue, oval-shaped tube you see in the photo just above. I dubbed it the sinking submarine, because it’s a cramped space and we were standing at a 32-degree angle relative to the ground!

It’s going to be exciting to watch the telescope take shape again after the teardown process. New parts will be arriving in the coming months. A large crane will be deployed outside the 4-meter to lift out the old secondary ring and bring in the new one. The plan is to be back on sky to test components of the new instrument later this year. Once those tests are completed, other components will be finished, revised if needed and then installed. At that point, the Mayall’s new five-year mission to map the universe will begin.


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Finder Scopes

One of the things I like about working at Kitt Peak National Observatory is that my job has a lot of variety. I contribute to important science projects and I help with engineering that helps to achieve the observatory’s science goals. Sometimes I act as something of a councilor, commiserating with observers during inclement weather. I even get to employ my writing skills when documenting tasks for our operations manuals.

This past week, one project I helped with was testing a new finder scope for the 4-meter telescope. Finder scopes don’t often get a lot of attention, but they serve an important function. Telescopes often give you such an enhanced view of the sky that it’s difficult to know exactly where you’re pointed. A finder scope is simply a smaller telescope mounted to the bigger telescope that lets you see a wide swath of the sky and confirm that you’re looking where you think you should be. Even my 90mm telescope has a finder scope on it. It’s the little tiny telescope piggybacked on the bigger telescope.

Here’s a view of the finder scope mounted to the top of the 4-meter telescope at Kitt Peak. Note that it’s basically just a camera lens directing light into a little digital camera.

This will prove vitally important when we start using the DESI spectrograph on the 4-meter. With that instrument, we’ll have fibers directing most of the light to spectrographs instead of a direct view of the sky. We will have a guide camera, but if, for some reason, the telescope pointing is off, it may be hard to find where we are. Because of that, it’s nice to have a widefield view of the sky. The images taken with the finder scope won’t be the ones you see in most magazines, but still, we played a little while testing and took a nice photo of the Andromeda Galaxy, M31 and it’s companion, M110.

We also took an image of the Pleiades, which is a nearby open cluster visible with the naked eye. These are young stars with nebulosity still around them. Even with our small telescope, it only took 30 seconds to see some of the nebular clouds.

Speaking of variety, another job I did this week was help an astronomer monitor a Jupiter-sized planet as it transited its star. This planet had a rotational period of only 1.6 days and we monitored it with the WIYN telescope at the same time the Kepler Space Telescope monitored it. Having two telescopes monitoring it at the same time allows for scientists to confirm and double check results. The system we were watching is very much like system I wrote about in the anthology A Kepler’s Dozen. You can learn more about the book and find places to order at http://www.davidleesummers.com/Keplers-Dozen.html. The book gives a unique look at the types of worlds discovered by the Kepler Space Telescope. My co-editor on the project was Dr. Steve B. Howell, head of the Astronomy and Astrobiology Division at NASA’s Ames Research Center.