Cosmic Cartography

When plotting out my stories, I spend a lot of time looking at maps. This can be especially useful when writing historical fiction. Boundary lines change and even physical features can change because of human activity or natural phenomena such as earthquakes. Also, maps reveal the limitations of those who made them. Before the modern era, mapmakers didn’t have satellites to define coastlines or mountain ranges. People on the ground had to do their best to measure and calculate distances and translate those into maps.

While working on the DESI survey at Kitt Peak’s Mayall survey, I feel a little like one of those early cartographers. Of course, our job is to measure the distance to as many galaxies as we possibly can and make a map of the known universe. As it turns out, I’m not alone feeling this way. Graduate Student Claire Lamman at the Harvard-Smithsonian Center for Astrophysics was inspired to create an illustration in the form of an antique map called Cosmic Cartography. You can see the artwork in detail and read about it at a post Claire wrote for the DESI blog at https://www.desi.lbl.gov/2021/08/19/cosmic-cartography/

Recently, my wife celebrated her birthday. Like me, she enjoys old maps and she also enjoys challenging puzzles, so I gave her a 1000-piece puzzle of the Cosmic Cartography artwork.

Cosmic Cartography Puzzle

Not only am I reminded of cartographers from long ago who made maps, but I’m reminded of science fiction stories where starships on patrol had the job of making maps. Of course, such starships require a team of highly trained people and one of the great ways to build teamwork is to have a set of common logos. In science fiction, these often take the form of badges or patches on uniforms. In my world, these might be stickers on laptops, T-shirts or ball caps. With that in mind, the DESI team actually created a place where you can order these kinds of items. One of the items is a poster of Claire’s Cosmic Cartography artwork, which can be ordered as a jigsaw puzzle, which inspired the present for my wife. If you want to show your support for our project mapping the universe, you can find all the cool DESI Swag at the project’s Redbubble shop: https://www.redbubble.com/people/DESIsurvey/shop

As it turns out, the puzzle was a bit more of a challenge than some other similar puzzles my wife and I have done. Redbubble is a print on demand company and the puzzle was printed on somewhat thin cardboard and the jigsaw cuts didn’t have a lot of variation, so it was possible for pieces that didn’t belong together to attach better than they should. Still, my wife and I persevered and assembled the puzzle. It was fun to discuss the different elements of the artwork. Some notable elements are the Mayall telescope and dome and an area of the map itself representing the MzLS survey, which I helped with. There’s a circle showing the Sloan Digital Sky Survey map. I was at that telescope’s dedication ceremony in the 1990s. There’s even Baoban, the DESI coyote. The coyote gets his name from two sources. BAO stands for Baryonic Acoustic Oscillations, which is the science which allows us to accurately determine distances to galaxies and “Ban” which is the Tohono O’Odham word for coyote.

Working on the puzzle proved a good opportunity to both spend some time with my wife and to reflect on the talented and bright group of people I’m privileged to work with.

Breaking Records

It occurred to me it’s been a while since I’ve shared a behind-the-scenes look at my work at Kitt Peak National Observatory. Now that the DESI spectrograph is on the Mayall Telescope and the NEID spectrograph is on the WIYN Telescope, we’ve fallen into a fairly regular routine where, most nights, I check in with the observing team at 4pm via video chat, then go to the control room where I’ll eat dinner, open the telescope and start observing through the night. We wrap up as the sun starts lightening the sky in the morning. Targets for the night are predetermined before observing begins for the night. Once observing begins, much of my job is watching that the telescope doesn’t try to move to a position where it physically can’t and I’m the first line of defense in case the telescope or instrument malfunctions. I also watch the weather to make sure rain, wind, or snow don’t damage the telescope.

A slice through the 3D map of galaxies from the first few months of the Dark Energy Spectroscopic Instrument (DESI). The Earth is at the center, with the furthest galaxies plotted at distances of 10 billion light years. Each point represents one galaxy. This version of the DESI map shows a subset of 400,000 of the 35 million galaxies that will be in the final map. Image courtesy NOIRLab.

Before the COVID-19 pandemic, we expected that both the telescope operator and lead observer for the night would be working in the same room, possibly with some support scientists. As it turns out, I wrote a post recently describing how these plans had to change so we could operate safely in these times. As things currently stand, I work in a control room alone and coordinate with the rest of the team via video conference. You can read that post here: https://www.desi.lbl.gov/2021/11/17/social-distancing-while-mapping-the-universe/

All this steady plugging away, observing the sky night after night with DESI is paying off. It was just announced that after just seven months of operation, DESI has already surpassed 7.5 million galaxies mapped, which means it has already generated the largest 3D map of the universe to date. And we’ve only completed about 10 percent of the survey. When we’re done, we expect to have mapped over 35 million galaxies. The picture with the post is a slice of the map so far. The map is presented such that Earth is at the center. Each point on the map is a galaxy. I encourage you to take a look at the press release about the DESI results so far. It’s at: https://noirlab.edu/public/news/noirlab2203/

One of my favorite images at the press release is an interactive image where you can look the map above and compare it to all the data from the Sloan Digital Sky Survey in New Mexico. Sloan has been an on-going, ground-breaking project in its own right. I was fortunate enough to be on hand when that telescope was dedicated and the survey began. At the time, I worked as an engineer for a 1-meter telescope just a few yards away from the Sloan at Apache Point Observatory. I think it’s fair to say that DESI would not have been able to achieve what it has so far if Sloan hadn’t paved the way.

As it turns out, DESI’s value isn’t limited to creating a big map of the universe. Yes, that’s important and hopefully it’ll give astronomers clues about how the universe is expanding and how that may be related to this thing called dark energy. However, DESI is also creating a giant database of all these spectra that researchers will be able to use for years to come to understand more about the different types of galaxies and quasars we’re observing along the way.

On a good night up here, everything seems quiet and routine, which doesn’t give me a lot to share here, but it is producing lots of data and expanding our knowledge of the universe. Of course, routine nights also give me a chance to ponder the universe and continue to inspire me. As always, you can find links to my books and stories at http://www.davidleesummers.com

Summer Shutdown 2021

I returned to work on site at Kitt Peak National Observatory in November 2020. Social distancing regulations were put in place along with several other protocols to minimize the risk of COVID-19 infection. In that time, we’ve been making great strides commissioning the DESI spectrograph and starting it’s five-year survey, which is intended to result in the most comprehensive 3D map of the universe yet made. The instrument is already getting results. For those who don’t recall earlier posts about DESI, it has 5000 optical fibers mounted at the prime focus of the Mayall 4-meter telescope. Each fiber can be positioned to align precisely with an object on the sky. The fibers run to a spectrograph where the light is analyzed and redshifts of distant objects such as galaxies and quasars can be measured. The following image shows how much sky DESI gets in one pointing. It shows the nearby Andromeda Galaxy taking up much of the field, but as an example, you see that one fiber has landed on a distant quasar. It’s spectrum is displayed in the inset box. Each of the pizza-slice segments represents the 500 fibers in one petal of the DESI instrument.

The disk of the Andromeda Galaxy (M31), which spans more than 3 degrees across the sky, is targeted by a single DESI pointing, represented by the large circular overlay. The smaller circles within this overlay represent the regions accessible to each of the 5000 DESI robotic fiber positioners. In this sample, the 5000 spectra that were simultaneously collected by DESI include not only stars within the Andromeda Galaxy, but also distant galaxies and quasars. The example DESI spectrum that overlays this image is of a distant quasar that is 11 billion years old. Credit: DESI collaboration/DESI Legacy Imaging Surveys/LBNL/DOE & KPNO/CTIO/NOIRLab/NSF/AURA/unWISE

Summer in Arizona is monsoon season. In short, we get a lot of rain. Clear skies can be few and far between. As a result, this is the time of year engineers often choose to shut down the telescopes to do maintenance and make modifications. The DESI instrument has been performing well, but that doesn’t mean it can’t be improved. The fibers in each of those pizza-slice shapes are aligned by a system called the “Command Action Network” or CAN-Bus for short. It was determined that the CAN-Bus system in DESI could be improved. To do this, each petal has to be removed from the Mayall’s prime focus and placed in an area where it can be worked on. We’re able to do this work this summer because of the availability of COVID vaccines. We do take care to practice social distancing where possible and, especially in the wake of the Delta variant’s rise, we’re staying masked throughout the day. This next photo shows DESI with four of the petals removed.

DESI opened up. The red device in the foreground is used to carefully extract the petals.

The trickiest part of this operation is that the DESI petals are all attached by several yards of fiber optic cable to the spectrographs two stories below. When we remove the petals, we don’t want to torque or strain those cables too much. The petals are lifted down and placed on the floor beside the telescope. Once there, they’re placed into clean tents where they’re worked on. Here we see two members of the DESI team diligently working on the CAN-Bus electronics behind the fiber positioners.

Working on the petals. The fiber optic cables come out of the tent, run along the top and then over the rail to the spectrographs below.

Finally when all the new electronics are installed, the petals have to be tested. Among other things, we need to make sure we didn’t break any of the fibers as we handled the petals. DESI is designed to be able to shine light from the spectrograph up through the fibers. We call these “back illuminators” and a camera mounted just below the telescope’s primary mirror can take an image of the back illuminated fibers to see what position they’re in. Here we see the petal out of the telescope with the back illuminators turned on.

DESI’S fibers glowing a friendly blue, telling us all is well after the work has been completed.

Once the upgrades are completed, the petals are reattached to the telescope. This is a big collaborative effort involving many people from around the country and around the world. Once it’s done, we should have made what was already a powerful machine designed to answer questions about dark energy into an even more powerful machine.

New Year’s Eve at Kitt Peak

Earlier this week, I rang in the new year while on the job, helping observers commission the DESI spectrograph on the Mayall 4-meter Telescope at Kitt Peak National Observatory. Looking back, I see I rang in eight years of the last decade at the observatory. So, working on New Year’s Eve is getting to be something of a tradition for me.

Working at the observatory on New Year’s Eve is much like working on any other night of the year. It all starts out with me evaluating the weather. In the photo, I’m standing in front of the Mayall, watching the sunset. Throughout the week I had watched a forecasted storm for the night get downgraded to the point that we expected reasonable observing conditions. The night actually arrived with dark clouds and light snow. Not only was this unwelcome for observing, but New Year’s Eve was the last night of my shift and I didn’t relish the idea of driving on snowy roads.

The poor weather didn’t keep us from our commissioning work. On an instrument where 5000-robotic fibers must be precisely aligned with targets on the sky and then send the light from those targets to ten spectrographs, there’s still plenty of work that may be accomplished with the dome closed. We started with some spectrograph calibration tests, trying to answer whether it matters where the telescope is pointed when we calibrate the instrument. There was some concern about whether or not twisting of fibers at different telescope orientations might make subtle changes to the light going through them and affect the measurements we hope to make. This is important to understand and characterize before we start making measurements.

Another job we had was to test a camera that looks at the fibers on the telescope. That’s how we know the fibers are on the correct objects. We can test this camera because DESI includes some fibers that can be illuminated. This means the fiber view camera can see the position of some fibers even when we’re not looking at the sky. The telescope itself is big and flexes as it points around the sky. Understanding how objects appear on the fiber view camera depending on where we point is also an important job. We can do a lot by pointing the telescope in the closed dome with the test fibers illuminated.

Testing a new, complex system also uncovers software bugs and errors in procedure. The lead software developer on this project is fond of using barnyard sounds like a chicken clucking or a cow mooing when an error occurs. So, these sounds do occasionally intrude into our work, which means the software people need to debug code or help observers refine procedures. This is also productive work for a cloudy, snowy night. I’m also convinced that I need to find a way to work barnyard noises into some future high-tech science fiction space opera!

At 10pm, we tuned into the live feed from Times Square in New York to watch the ball drop while we worked. At midnight, we took enough of a break to toast the new year with mugs of coffee. Kitt Peak National Observatory is on the land of the Tohono O’Odham, so no alcohol is allowed, even if we weren’t working.

When the decade started, I thought of myself as “the temp” on the operations staff at Kitt Peak. I returned to Kitt Peak after nearly fifteen years to help the observatory with a staffing challenge and stabilize my income long enough to achieve some personal goals. Ten years later, I’ve achieved most of my goals, but I still think of myself as “the temp.” It’s an attitude that serves me well.

In the current political climate, I can’t guarantee my job will always be funded so I don’t take for granted I’ll have this job for an indefinite period of time. More importantly having the attitude of being “the temp” assures that I always feel free to speak my mind when needed and avoid self censorship, which is important in a job where I’m responsible for the safety of visitors. Also like any good temporary employee, I want to stay in the good graces of my employers, so it assures that I always try to do my best and constantly hone my craft.

As one decade finishes and another begins, I’m thankful to have a good and interesting job expanding humankind’s knowledge of the universe, but I also stand ready to take on whatever challenges that universe decides to throw at me in the coming decade.

Stars, Galaxies, and Fiber Optics

The first time I remember learning about fiber optics was in a behind-the-scenes article published in 1980 or so about the making of Star Trek: The Motion Picture. The article talked about how they got light to all the buttons on the bridge set and showed them illuminated with bundles of optical fiber. Nowadays, as I’ve mentioned in several earlier posts, I work with instruments that use optical fiber to carry light collected by each of the telescopes I work with to the instrumentation where its analyzed.

On the telescope side, those fibers are attached to an optical assembly that must be placed at just the right spot to catch focused light. If the star or galaxy is out of focus, not all the light goes down the optical fiber. We also have guider cameras that work to keep the object precisely aligned on the fiber so all the light gets to the spectrograph. It’s a lot of complex hardware to work right to precisely measure the the redshift of distant galaxies or look at a star and determine whether or not it has planets in orbit. This past week, we’ve been commissioning both the DESI spectrograph at the Mayall 4-meter and the NEID spectrograph at the WIYN 3.5-meter. One of the most important milestones is to get light from the object you want to measure to the spectrograph and see if you get the flux you expect. Here’s the NEID team at WIYN looking at early test results.

Yes, light leaves a star dozens of light years away, enters our telescope, goes down the optical fiber and is photographed with the spectroscope, then all that data can be viewed and analyzed on a laptop computer. When I filmed the trailer for The Astronomer’s Crypt a couple of years ago, I was asked why we didn’t use a room full of fancy computers and monitors. We just had a couple of computers, one of which was a laptop. The reason is that I’ve seen a lot of control rooms where simple computers are the only ones present!

As you can imagine, it’s quite a relief to see all the work pay off in a spectrum that shows the flux level you expect. All of this is pretty exciting stuff and, as it turns out, my birthday fell during this past week’s tests. Seeing NEID as it nears readiness for scientific use is pretty exciting in its own right, but we had another surprise on the day of my birthday. Ethan Peck, who plays Spock on Star Trek Discovery, was on a road trip and decided to visit the observatory. A tour was arranged and he spent the beginning of the night at the WIYN telescope. For me, it was quite a thrill to have Spock, of all people, wish me a happy birthday! He brought a Polaroid camera with him and we snapped a photo of us standing by my control station. Here we are at WIYN. Ethan Peck is in the center (in white) and I’m to the left.

Meanwhile, across the mountain at the Mayall 4-meter, commissioning has continued on the DESI instrument. The instrument had its official “first light” a couple of weeks ago and a wonderful image was released that, I think, really illustrates the power of DESI.

Image credit: DESI Collaboration, Legacy Surveys; NSF’s National Optical-Infrared Astronomy Research Laboratory/NSF/AURA

Here you see an image of all 5000 DESI fibers superimposed on the sky. At the bottom of the fiber array is M33, the Triangulum Galaxy. Below that is a view of the spectrum from just one of the 5000 fibers showing the light from that little piece of the galaxy. In it, you can see the lines labeled that denote the presence of hydrogen, oxygen, nitrogen, and even sulfur. Now remember that each fiber in that picture gives the same kind of data for the piece of sky its on. You can read the full press release about DESI’s first light at: https://nationalastro.org/news/desis-5000-eyes-open-as-kitt-peak-telescope-prepares-to-map-space-and-time/

All of the robotic positioners moving those fibers at the top of the Mayall telescope get hot and there’s a chiller system to keep them cool. This week, that chiller system will be automated, but last week, we had to monitor it by eye and it requires a person to turn the system on and off by hand. The person doing that remarked how spooky it is to be in the depths of the Mayall with all the lights out and remarked how she kept looking over her shoulder, wondering if someone was there. This is another aspect of my job that definitely helped to inspire The Astronomer’s Crypt. You can learn more about the novel and see the trailer I mentioned earlier at http://www.davidleesummers/Astronomers-Crypt.html.

Making Instruments Work

Today, I’m at the TusCon Science Fiction Convention in Tucson, Arizona. You can get all the details about the event at http://tusconscificon.com. One of the topics I’ll be speaking about is the work we’ve been doing for the last year, installing the DESI Spectrograph on the Mayall 4-meter telescope. At this point, installation is nearing completion and we’re beginning the process of commissioning the instrument. In short, we’re actually making it work with the telescope so we can get the data we hope to obtain.

DESI isn’t the only instrument that we’ve recently installed. We’ve also installed the NEID spectrograph on the WIYN telescope. While DESI has the goal of making a 3D map of about one-third of the sky, NEID has the goal of looking for planets around other stars. I’ve shared quite a bit about the DESI installation because that instrument is of a scale that it required a major refit of the telescope. The NEID spectrograph has involved a similar amount of time in development, but much of that development has happened off site at places such as Penn State University and the University of Wisconsin. NEID, which rhymes with fluid, takes its name from the Tohono O’Odham word meaning “to see.”

Two weeks ago, the port adapter, built by the University of Wisconsin, and the spectrograph, built at Penn State University, both arrived at WIYN and have been installed at the telescope. You can see the port adapter on the side of the telescope in the photo above. It’s job is to capture light coming through the telescope from a distant star and feed it into fiber optics that run downstairs to a high precision spectrograph.

The spectrograph itself lives in a clean room on the WIYN Observatory’s ground floor. To get the kind of precision needed to see planets around other stars, the temperature within the spectrograph must be carefully maintained and the spectrograph elements must be kept in the same relative position. Footsteps nearby could disturb this device. Because of that, the spectrograph itself is built inside a coffin-like housing. Once the Penn State team gets everything set up, they’ll seal up the coffin and, unless there’s a serious problem, no one will look inside again. I got to peak inside the spectrograph a few days ago and it may be my only view.

Now that the instrument is installed at the telescope, we have to make sure everything works as it should and programmers are working to make sure we have software to assure we can efficiently get the data we need. We’re starting with the port adapter itself. I point the telescope at stars and a team of scientists and engineers check the function of the various parts within the adapter to make sure they understand the alignments on the sky, which are necessary for tracking the stars. They check the tip-tilt electronics, which make sure we get as much of the star’s light as possible down the fiber, and make sure all the calibration functions work. After this, work will begin commissioning the spectrograph itself. This is a process which takes a few months to complete to assure we’re getting the performance out of this instrument that we want.

Commissioning nights are very different from normal observing nights at a telescope. On a normal observing night, it’s often me and an observer. Often the observer isn’t even at the telescope, but working from their home institution, controlling a camera on the telescope over the internet and talking to me through computer chat. On a commissioning night, I can have anywhere from five to fifteen people in the control room with me, all working on different elements of the instrument. This marks a busy and exciting time as we get these new instruments ready for service at Kitt Peak National Observatory.

Cable Wrangling

In previous posts about the DESI spectrograph being installed at Kitt Peak’s Mayall 4-meter telescope, I’ve focused on the 5000 robotic positioners at the telescope’s focal plane, which is up at the top of the telescope, and the ten spectrographs located in a climate controlled room at the telescope’s base. However, I haven’t talked a lot about how the light from the 5000 positioners gets down to those spectrographs. The light travels along optical fibers that run from the telescope’s focal plane down to the room with the spectrographs. The whole distance is roughly 40-meters (or a little less than the length of half a football field).

In the photo to the left, you can see the cables running along the front of the telescope at this angle. They’re draped over the blue horseshoe structure in the foreground. Several of the cables are draped down in the lower left-hand side of the photo. There are ten cables that run from the top of the telescope to the room with the spectrographs. Each cable contains 500 individual optical fibers. Each of these cable bundles feeds one of the spectrographs at the telescope’s base. Since each cable contains 500 optical fibers, they are heavy cables. They’re also very fragile. It would be challenging enough to run these fibers from one point to another if they could be locked down in one position. However, the telescope actually has to move, so we can look at different parts of the sky. This means these heavy, fragile cable bundles have to move too.

Before construction even began on the DESI spectrograph, engineers spent time figuring out the best way to run the cables that minimized how much they had to move. Also, there are devices called e-chains that help assure cables stay nice and neat as the telescope moves. This past week, one of the engineers snapped a photo of me helping to prepare one of the e-chains for installation. He was in a lift up near the telescope’s top and looked down at me and another one of the telescope engineers hard at work. I’m the one in the yellow hard hat.

As I mentioned earlier, these cables are both heavy and fragile. That means there’s been a lot of heavy lifting that requires a great deal of care about where we step and place the cables. We don’t want to bend them too tightly, or they could break. The upshot is that this has been exhausting work. Everyone feels wiped out at the end of the day.

Still, we see the proverbial light at the end of the tunnel, or perhaps that should be the light at the end of the fiber! Once the cables are run, we only need to install the last three spectrographs, then the system will be complete. How soon we’ll start observing with the DESI spectrograph will depend on the results of preliminary testing which has already commenced and will be finished soon after the installation is complete. That said, I am told there’s a very good chance we’ll be pointing DESI at targets on the sky in less than a month. At that point, we may start to understand more about this mysterious thing that astronomers have dubbed dark energy.

DESI Naked!

This weekend finds me at Bubonicon 51 in Albuquerque, New Mexico. I’m moderating panels about space cowboys and large scale scientific surveys. If you’re in town, click the link to get the details and drop by. I’d love to see you there. Of course, part of my interest in large scale scientific surveys has to do with the work I’ve been helping with over the last year and a half, installing the DESI Spectrograph at the Mayall 4-meter telescope at Kitt Peak National Observatory. During my my recent shift at the observatory, I got a rare look at the new instrument not just “under the hood” but before the hood even went on.

In the photo above, you see DESI on the left, just over the orange platform. Standing on the ground floor in the foreground are just a few of the telescope engineers and technicians who have been installing this new, innovative instrument which will be used to make a 3D map of about a third of the known universe. DESI itself is an array of 5000 fibers mounted on robot positioners that can be precisely centered on targets each time the telescope moves. The light from those objects then travels down fibers two stories below. The fiber bundles are ready to be run along the telescope. You see them coiled up on the white carts to the lower right of the photo above. Each black cable contains 500 fibers. One of my jobs this week was labeling those cables so people can keep it straight which cable is which as they run them along the telescope.

Here are all the DESI fiber positioners mounted to the telescope. You can see each of the ten cables coming up into ten sets of fiber positioner “petals.” Each of these petals was installed into the telescope with great care about a month ago. Light was placed on all the fibers and it was confirmed that in all the transportation and installation, none of the fibers were broken. All of them transmit light as expected! This week, the control electronics are being wired up and routed through the telescope. Once this chore is complete, more testing will happen to assure that the fibers still transmit light and each of the robot positioners moves as expected using the electronics routed through the telescope.

All of those fibers will eventually come into a clean room downstairs to a series of ten spectrographs. Do you begin to sense a pattern? Ten petals, ten cables, ten spectrographs. As it turns out, another job of mine this week was helping to install the seventh spectrograph, which you see in the lower right of the photo above. Western fan that I am, I feel like you can now cue Elmer Bernstein’s score for The Magnificent Seven. Of course, that won’t last long. soon we’ll have an eighth, ninth, and tenth spectrograph.

Each of those spectrographs will be used to examine the light from 500 fibers. To make the map, we’ll be using these spectrographs to see how far characteristic chemical lines in spectra have shifted from where they normally sit within the rainbow toward the red end, which is one measure of how far away those objects are. We’ll compare that to statistics of how far apart they are, which turns out to be another measure of how far away they are. That said, just because we’re mostly looking for the redshifts, there will be all kinds of other spectral data available that can tell astronomers all kinds of information about properties of galaxies all over the sky. One of the most exciting things about the DESI program is that this data will be available to all. In this post, I may be laying DESI bare for all to see, but the whole project will be laying much of the universe bare, and in the process expanding the body of astronomical knowledge.

  • For a fictional and frightening look behind the scenes at an astronomical observatory, read The Astronomer’s Crypt.
  • To take a tour through the wonders of the solar system, read The Solar Sea.
  • To travel back in time to the Old West, check out Owl Dance!

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