Practice Makes Perfect

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

Seeing Daylight Once Again

As I write this, the DESI Commissioning Instrument run at the Mayall 4-meter telescope at Kitt Peak National Observatory will be nearing completion. The Commissioning Instrument is an array of five digital cameras that view the sky through the telescope’s new optics. Once the Commissioning Instrument comes off, the actual DESI fibers and robot positioners will be assembled at the focal plane. This is a process that’s estimated to take about three months to complete. During that time, I’ll be returning to day shifts at the Mayall telescope, helping with the installation. The DESI fiber “wedges” are starting to arrive and assembly has actually begun on some components down on the telescope’s ground floor.

There is a terrific video describing the DESI project and showing these wedges being populated with the fibers in the lab that you can watch at: https://newscenter.lbl.gov/2018/10/17/dark-energy-project-robots-3d-map-universe/

The DESI fibers are the business end of getting light from distant galaxies where it needs to go to be analyzed. Light traveling for billions of light years will be sent through those fibers to be separated and photographed by spectrographs. Before light gets to the fibers, it has to be collected by the telescope, where it will pass through an optical corrector lens. The corrector makes sure that when the telescope is focused, each fiber will also see an equally focused object. Of course, to do this, the whole instrument has to be aligned well with the primary mirror so we know each target lines up with a fiber.

The goal of the Commissioning Instrument is to give us a simple camera that lets us check that the corrector lens is doing its job. It also allows us to test the alignment and focus mechanism, which we call the hexapod. We want to make sure these critical components work before going to all the work of assembling all those fibers at the top of the telescope. In fact, during the Commissioning Instrument run, we discovered that the corrector was eight millimeters too close to the primary mirror. This was a result of telescope blueprints from 1973 not being updated with as-built specs. Eight millimeters may not sound like much, but it’s enough to keep the fibers from being in focus during the warmest nights of the year! So, the hexapod and corrector assembly were moved, which is much easier to do now than when all the fibers are in place.

I have enjoyed my day shifts at the Mayall this past year. It’s given me a chance to interact with more of the maintenance and engineering crew than I normally do in my nighttime operations. I won’t be working exclusively during the daytime. I will still spend one week a month supporting nighttime observations at the WIYN 3.5-meter telescope. If you would like a behind the scenes look at what it’s like to work at an observatory at night, along with something of a scary story, check out my novel, The Astronomer’s Crypt. You can learn more about the novel at: http://www.davidleesummers.com/Astronomers-Crypt.html

The Backbeat of the Universe

This past week, I’ve been helping to re-commission the Mayall 4-meter telescope at Kitt Peak National Observatory and commission the first components of the new DESI spectrograph that we’ve been installing. In nautical terms, you can think of this as being like a shakedown cruise. We’re making sure the telescope is primed for taking scientific data and we want to assure we’ve worked out all the kinks from the telescope sitting idle for a year while it was rebuilt. We’re also making sure the components of the new instrument work as expected.

I have mentioned in previous posts that DESI is a spectrograph fed by 5000 optical fibers, each of which can be positioned to sit on a specific target in the sky. Those 5000 fibers have not yet been installed. What we have now is more of an optical camera installed at the top of the telescope in the black “can” at the top of the picture in this post. That allows us to evaluate the image quality through the telescope and make sure the light from objects on the sky will actually fall on those 5000 fibers when they’re installed.

We also have the guider that will be used with DESI. A telescope like the 4-meter is designed to track the sky with great precision, but because it’s such a large real-world machine, imperfections always creep in, so we have a camera that watches the sky and makes fine corrections to the telescope’s pointing as it tracks the sky. The commissioning instrument we have on now, will let us put the guider through its paces.

The goal of the DESI’s five-year mission is to make a three-dimensional map of about one-third of the entire sky, by giving us not only precise positions of every object we can see in that area, but by giving us distance as well. So, how can DESI do this? It takes advantage of something cool that happened in the early universe.

Everywhere you look in the sky, as far away as we can see, which also means as far back in time as we can look, is something called the cosmic microwave background. This is the universe as it looked about 400,000 years after the Big Bang. Given that the universe is 14 billion years old, that’s a long time ago! Before the epoch of the cosmic microwave background, light was bound up and couldn’t escape. At 400,000 years, the universe had expanded enough that that light and heat could escape, but there was enough gravity to try to keep that from happening. These competing forces set up acoustic waves throughout the universe. These acoustic waves were everywhere and they collided, setting up beat frequencies. These beat frequencies helped to set up localized points of gravity which drew material inwards. In the fullness of times, those localized points would become galaxies. Here’s what the universe looked like at that time.

Image courtesy WMAP Science Team

Now here’s the cool part, because we understand acoustic theory, we can predict how far apart these localized points will be and we can look to see if galaxies tend to be distributed as you would predict from looking at these acoustic waves. In fact, they are. Galaxies today tend to be separated by factors of about 500 million light years. Statistically, they’re much more likely to be at some factor of that than say, 400 or 600 million light years.

If you know how far apart galaxies are today and you know how far apart the acoustic beats were in the primordial universe, you can use geometry to look at more distant galaxies. We used to use how far a galaxy’s chemical fingerprint was shifted toward the red end of the spectrum as a way to measure distance to those galaxies. However, that assumes you understand the rate the universe is expanding. The separation between galaxies at the same redshift, will tell you how far away they actually are without making assumptions about the way the universe expands.

I will be speaking more about this and the DESI project at two astronomy club meetings in the next month. The first presentation will be for the Astronomical Society of Las Cruces on Friday, April 26 at 7pm. The meetings are held at the Good Samaritan Village in Las Cruces, New Mexico. More information about the location is available at: https://aslc-nm.org/MonthlyMeeting.html.

My other presentation will be given to the Phoenix Astronomical Society in Phoenix, Arizona on May 9 at 7:30pm. You can find more details about the location at: http://www.pasaz.org/index.php?pageid=meetings.

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


October Adventures Continue

In my last post, I shared some of my adventures traveling around the country this month. Admittedly, a travelogue may seem a little out of place for a post appearing just two days before Halloween, but I’ll share a book at the end to put you in the spirit of the season and it’s even a quick read.

I left Kansas City on the train on Sunday night, October 14. By the time I woke up on Monday morning, the ground was covered in snow. I like traveling by train when I can. It’s a great way to see the countryside and although it takes longer than traveling by plane, it feels much more civilized. I enjoy flying, but the hassle of crowds, airport security, and flights filled to the brim take away much of the fun. Besides, my grandfather, dad, and brother all worked on the railroad, so I feel a certain family connection when I travel by rail.

I met my wife in Albuquerque where she brought my faithful Smart Car in for a service. We then drove down to Las Cruces with a brief stop in Socorro for some chicken mole enchiladas. For me, chocolate and chile come together to form the ultimate comfort food. After a four-hour sleep, I then drove to Tucson for a daytime shift at Kitt Peak where we’re continuing to refit the Mayall 4-meter for the Dark Energy Spectroscopic Survey.

After three days on the mountain, I gritted my teeth for another short sleep, got up early in the morning to drive to the airport where I caught a plane for Denver, Colorado. There, I celebrated MileHiCon 50. The highlight of the event was that every living convention guest was invited back as a guest. Here you see them assembled at opening ceremonies.

MileHiCon is always a special for me because I get to connect with so many people I’ve worked with over the years. These include Bob Vardeman who was one of the honored guests and who created the Empires of Steam and Rust Series,  David B. Riley one of the co-authors of Legends of the Dragon Cowboys, J Alan Erwine and Carol Hightshoe who have edited many anthologies I’ve been in and who appeared in A Kepler’s Dozen. Denver is also home to Laura Givens, the talented artist who has done many of my covers, and also the co-author of Legends of the Dragon Cowboys.

A particular high point of MileHiCon was the annual poetry reading. This year it was moderated by Stace Johnson. Ronnie Seagren joined us and read poems by several different people. Sadly, Gail Barton, a staple of past MileHiCon poetry readings had passed away, but I was fortunate enough to have a copy of the poetry journal she often handed out at the event, which allowed me to share some of her poems. It was lovely to have her voice at the event at least one more time.

Once MileHiCon was finished, I returned to Kitt Peak to continue work on the DESI spectrograph. This time, I helped a team from Ohio State University build the racks that will hold the spectrographs themselves once they all arrive. I have to admit, building the racks was a process not unlike assembling a piece of Ikea furniture!

At last, I am back home for Halloween. I’m turning my attention to some editorial projects, including a new novella from David B. Riley and two great books from Greg Ballan. In my off hours, I’m reading some spooky comic books and watching a few hair-raising films.

If you’re looking for something good to read between trick-or-treaters on Wednesday night, may I recommend the collection Blood Sampler? This book collects thirty-five vampire flash fiction stories written by Lee Clark Zumpe and me. The cover is by Laura Givens and the book features interior illustrations by Marge Simon. Chris Paige, writing for the fan newspaper ConNotations in Arizona said, “If you like vampire stories, this may be the best seven dollars you can spend.” Admittedly the new edition of the paperback went up to $8.00, but the ebook is only $4.00. You can learn how to get your claws on a copy by visiting  http://www.davidleesummers.com/Blood-Sampler.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.