Lasers on Telescopes

For me, the phrase “lasers on telescopes” brings to mind super villains capturing top secret astronomical facilities in order to execute a nefarious plan. I think of Mr. Freeze capturing Gotham Observatory to build a giant freeze ray in the movie Batman and Robin. Perhaps a funnier and better example is Chairface Chippendale using a laser in a telescope to deface the moon with his name in the TV series The Tick.

Laser measuring tool (on yellow arm between black mirror covers) over the Mayall primary mirror.

In fact, lasers are used on telescopes. Perhaps the best known real-world examples are telescopes that use laser guide stars. This is a technique where astronomers fire a laser mounted on the telescope into the sky. The laser light is scattered by the atmosphere, but optics in the telescope correct that light back into the proper size beam and also correct the stars seen at the same time. We had a system like that at the 2.1-meter telescope at Kitt Peak run by CalTech. There was also a system like that at the 3.5-meter telescope at New Mexico’s Apache Point Observatory.

Now, these lasers are not ones that are likely to be co-opted for nefarious purposes by super villains. Lasers used for guide stars just aren’t that powerful. That said, they can’t be used with impunity. The artificial guide star laser at Kitt Peak was visible in the ultraviolet band and would interfere with optical telescopes also observing in that band. What’s more, I’ve been told Apache Point Observatory had to clear laser firings with the Air Force, who had a base nearby. The observatory’s laser wasn’t likely to shoot down planes, but we could imagine tragic results if a pilot happened to fly through a laser’s line of sight only to be blinded.

This past week, while working at the Mayall 4-meter telescope, we were also using a laser. In this case, it wasn’t fired at the sky, but the laser was mounted on the telescope’s mirror cell and fired at different surfaces on the telescope to get precise measurements. Now that the refit for DESI is nearing completion, the engineers need to make sure everything went back together as it was designed. They need to make sure all the new parts are placed in just the right place. If not, this is the time to make adjustments. Measurements of telescopes are important because they help to assure that astronomers can focus the telescope properly. Precise measurements are also critical to determine the proper weight distribution of the telescope, which in turn helps it track the sky precisely.

As it turns out, I also spent part of this past week working on an adaptive optics system a little like those laser systems I mentioned. However, the WIYN Tip-Tilt Module doesn’t actually use a laser. Instead, it takes precision measurements of an actual star and uses optics within the instrument to bring that star as close as possible to a precise point. I’ve seen it used to deliver incredible image quality with stars only 0.3 arcsecs across. To put that in perspective, star images with WIYN are typically more like 0.8 arcsec across. The size difference is the result of atmospheric blurring.

This all echoes something I’ve been saying in the past few blog posts. If something isn’t quite right, there are ways to fix it, even when its a multi-million dollar scientific project. By comparison, books are much easier to fix. It’s why beta readers and editors are so important to the writing process. They help us see places where we didn’t express ourselves clearly, made something work in an artificial way, or simply used the wrong word. It’s part of why reviews are so important. Reviews help customers, but they also help writers because they tell them what worked and didn’t work.

Over the years, reviews helped me refine my craft until I could write books like Owl Riders and Firebrandt’s Legacy. And yes, reviews are helping me shape the 25th anniversary edition of The Pirates of Sufiro, which I’m working on right now. I hope you’ll join me on a journey to one of the worlds I’ve created and, if you do, please leave a review to let me and others know what you thought. The titles in this paragraph are links where you can get more information about the books.

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Reassembling the Mayall

Back in July, I discussed some of the different components that had come in for the DESI instrument being installed at Kitt Peak National Observatory’s Mayall 4-meter telescope. You can read about them in the post, Assembling the Puzzle. The corrector optics and hexapod alignment system have been installed into the telescope’s top end. Here I am, hard at work torquing the bolts that hold it all together.

If all goes according to schedule, the new top end will be lifted to the top of the telescope next week. At that point, the telescope will look more like itself again. Control cables and network boxes for the top end assembly will then be assembled so astronomers working in the control room can talk to the instrument. At that point, the work platforms that are visible in the older post will be disassembled. Here’s a look at the top end, almost ready to lift up to the top of the top of the telescope.

Once the top end is back on the telescope, the primary mirror, which is currently out of the telescope, will need to be re-aluminized. Telescope mirrors are finely polished, curved glass. Over the top surface is a very thin layer of aluminum which is applied in a vacuum chamber. The vacuum chamber for this process is the biggest one in the southwestern United States. I describe a scary scene involving such a chamber in my novel The Astronomer’s Crypt. Fortunately, care is taken to operate the chamber very safely in real life.

One thing to note about the top end in the photos above is that there is no actual instrument mounted yet. Astronomers rarely sit at an eyepiece actually looking through a telescope anymore. Most of the time, there’s a high precision digital camera looking through the telescope. Sometimes that high precision camera is designed to look at a specific wavelength region, such as optical light or infrared light. Sometimes that camera doesn’t look at the sky directly, but at light that’s been reflected off a grating. A grating is just a reflecting surface that breaks up light like a prism. The advantage to a grating is that you lose less light than you do when you shoot it through a chunk of glass. Breaking up light then allows you to see lines in spectra that tell you about the chemistry of the object you’re looking at.

In a nutshell, that’s the kind of instrument DESI is. Astronomers are interested in the chemistry of the objects they’re looking at. However, there’s one other feature you get by studying these spectral lines. When an object moves, the lines shift toward the blue end of the spectrum if the object is moving toward the observer or toward the red end of the spectrum if the object is moving away. That’s what we mean when we talk about blue shift and red shift. What’s more, how far the chemical lines have shifted is a measure of the object’s velocity through space. The goal of DESI is to measure the velocity of some 5000 objects every time the telescope points to a new target. That said, this data will be available to everyone and it contains all the fundamental chemical information about the objects the telescope is pointing at.

Before the final DESI instrument goes on, there will be a commissioning instrument. That will be more like a regular camera—more like looking through an eyepiece. The goal of the commissioning instrument will be to align the telescope on the sky after all this work has been done and assure that the telescope has good pointing so that we can get the best data when we’re using the spectrographs later.

Once the commissioning instrument goes on the telescope, I’ll return to my regular nighttime duties at the Mayall, shaking down the rebuilt telescope and getting it ready for its next five year mission. My novel, The Astronomer’s Crypt, which I mentioned in passing, is not just a horror novel, but it provides a look behind the scenes at an observatory. If you’re interested in seeing what goes on at night at a facility like Kitt Peak, or one of the other observatories where I’ve worked over the years, it’s a great place to start. Just be warned, not only will you encounter astronomers, engineers and technicians, but some ghosts, a monster from Apache lore, and a few other surprises as well. You can get more information about the novel at: http://www.davidleesummers.com/Astronomers-Crypt.html


Assembling the Puzzle

This has been another week helping to install the Dark Energy Spectrographic Instrument or DESI at the Mayall 4-meter telescope at Kitt Peak. In short, the goal of DESI is to study the effect of dark energy on the expansion of the universe. We plan to collect spectra of tens of billions of galaxies and quasars with the goal of making a three-dimensional map of the universe out to about 11 billion light years. You can read more about the DESI project at https://www.desi.lbl.gov/

The DESI project is spearheaded by Lawrence Berkeley Lab in California and being installed at Kitt Peak in Arizona. However, it really represents a worldwide collaboration. There are scientists working on this project from England, France, Spain, Italy, South Korea, China, France, Canada, Colombia, Australia, and others plus numerous institutions within the United States. All of these agencies are not only contributing expertise, but actually building components that will go into the finished instrument.

In an earlier post, I spoke about how we worked to remove the Mayall telescope’s original top end. The top end originally housed both a secondary mirror and a prime focus camera. Both of these have been used to make groundbreaking discoveries over the last five decades. The Mayall was the telescope Vera Rubin used to study rotation curves of galaxies, which led to the discovery of dark matter. I’ve helped with observations that have led to the confirmation of numerous exoplanets. We’re now replacing the telescope’s original top end with a new one that will hold 5000 fibers at prime focus. Each of those fibers will run to spectrographs that will break up the light from objects in the sky so it may be analyzed and the position of the object can be measured. In the photo above, you can see the new top end being assembled to the left of the telescope.

To get light from the sky onto the fibers, the telescope will collect it with the primary mirror. That sits in the big white structure at the center of the big blue horseshoe-like structure in the photo above. The mirror will direct that light to the top end. Because the mirror is curved, allowing the light to be collected and redirected, it means the focus changes across the field of view. To deal with that, you need to put some lenses in front of the fibers, sort of like glasses. Another real world problem of telescopes is that as you point toward the horizon, light gets spread out. So you need optics to compensate for where you’re pointing in the sky. Sort of like glasses that automatically adjust themselves for where you’re looking.

Scientists from England assembled those specialized “glasses” for the telescope. Those arrived last week and I was on hand during their assembly at Kitt Peak. You see those assembled optics in the lower photo. Scientists from Italy built the “Hexapod” pointing system, which keeps those optics aligned. That arrived and was tested about a month ago. Scientists from Fermilab in Chicago are responsible for integrating those systems and putting them together in the top end ring. That process will start next week. It’s all quite a puzzle and it’s been remarkable to see it all come together. It’ll be even more amazing to see what science it yields.

Of course, work at Kitt Peak helps to inspire my science fiction. As a reminder, this is the last weekend of the Smashwords Summer/Winter sale. You can learn about my science fiction books that are on sale at:

We also have fantasy and steampunk titles on sale. You can learn about them at:

Ramping up the Refit

This past week, I’ve continued my work supporting the refit of the Mayall 4-meter telescope for the upcoming DESI spectrograph. DESI is the Dark Energy Spectroscopic Instrument and it will be capable of measuring of the spectra of 5000 objects at a time. Its mission objective is to collect data to help us understand the nature of Dark Energy in the universe. We don’t yet know what Dark Energy is, all we really know is that appears to make the expansion of the universe accelerate with time. To be able to collect these 5000 spectra, the telescope needs a new top end. Indeed, the first thing I saw when I came to work on Monday morning was the old top end sitting on a flatbed trailer outside the telescope being ready to go into storage.

The Mayall 4-meter is a reflecting telescope and the primary optical component is a big 4-meter diameter mirror at the bottom. The light from that mirror is then focused at that top end and either collected by a camera sitting there at “prime focus” or a sent down to an instrument underneath the telescope using a secondary mirror. The top end held both the prime focus and the secondary mirror and could be flipped end-for-end to allow either to happen. DESI will have its 5000 fibers in a new top end and indeed, part of the reason for selecting the Mayall was to have a telescope sturdy enough to handle that large an instrument. At the moment, the telescope is missing its top end, but the new one will be installed soon. There are work platforms, which enabled people to loosen the old top end so it could be lifted out with a crane. The work platforms also keep the telescope structurally stable while there’s no top end in place.

The top end only holds part of the instrument. It will have 5000 optical fibers which may be precisely positioned onto target objects. The light from those fibers is sent along the fibers to spectrographs in an environmentally controlled room where the light will be spread out and photographed so it can be analyzed. In the dark energy survey itself, most people will be looking at the so-called redshift—how far the characteristic spectral “fingerprint” of certain chemicals shifts to the red as a result of its velocity away from us. However, those same chemical fingerprints may be used to understand properties of the objects being looked at and this data will be available to anyone who wants to use it.

Because dark energy is an exciting topic in its own right, but also because this project will be generating so much raw data that’s useful to so many astronomers, it’s a major worldwide undertaking. To break the light from the fibers into spectra will require ten spectrographs which will reside in a carefully climate-controlled room. An exciting milestone I got to watch this week, was unpacking the first of those spectrographs when it arrived from France. Below, you can see the engineers inspecting the optical elements. Note the rainbow visible on the corrector plate of the right-most optical element. That’s exactly what this device is built to do! Break the light into rainbows.

Today finds me in Phoenix, Arizona for Leprecon 44. If you’re in town, I hope you’ll drop by and check out some of the panels and workshops.

Astronomy on Independence Day

I spent my Independence Day this week in the operator’s chair at the Mayall 4-meter telescope at Kitt Peak. Astronomers typically work every single clear night, regardless of weekends or holidays. I’ve worked during many Thanksgivings, Memorial Days, Presidents’ Days and more. In particular, I was supporting a project looking at stars with planets or planet candidates identified by the Kepler Space Probe and getting spectra of them. Spectra tell us things like the chemical composition of the star and the temperature, which in turn helps us know whether any planets discovered are potentially habitable.

4meter Console

Basically, when operating the 4-meter, I spend the night at the console shown above. It’s not as colorful as watching a fireworks show, but it’s still pretty thrilling to point the telescope at faint stars, then take a glimmer of light, spread it out through a spectrograph, and understand an object that’s hundreds or even thousands of light years away.

Quiet nights at the telescope can be a good time for reflection and on this weekend after Independence Day I do find myself privileged to be an American. I’m fascinated by the history of this great land, and I’ve turned to expressing that fascination through my steampunk writing. That said, I recognize this country is far from perfect and its leaders have made more than their share of mistakes, but one of the things that makes America great is perhaps that it’s easier to correct those mistakes here than it is in other countries. We’re still generally free to form our own opinions and express them.

I express my thoughts and explore ideas through my writing. Recently I came across a review of one of my books, claiming I was clearly a member of a certain political party because of some remarks a character made. It left me scratching my head. Sure, if a character expresses an idea, it’s something I’ve thought about, but my character and I may have very different outlooks. What’s more, even if I do share an opinion about one subject with a political party, it doesn’t mean I agree with others.

If there’s one thing that concerns me about America today, it’s a tendency to view things along very polarized party lines. If a person believes A, they must by necessity believe B,C, and D also. The truth is that like starlight, there’s a whole spectrum of ideas.

As the fireworks fade and light shows end this weekend after Independence Day, I encourage you to form your own opinions and take constructive action when you see a need for a change. Don’t be afraid to disagree with a friend and remember you can still be friends even if you disagree. I think that’s a viewpoint most of the protagonists in my novels and stories would agree with and it summarizes why this country really is so great.