The Pointing Dance

This week, I have been engaged in an important, albeit tedious activity at the WIYN 3.5-meter telescope. I have been building pointing maps. Telescopes are large, bulky machines that have to point with extreme precision and track the almost literal clockwork motion of the sky. They are engineered carefully, but like any machine they are subject to wear and tear. What’s more, to keep getting the best science, telescopes have to be upgraded from time to time. This changes the telescope’s behavior with time.

The WIYN Telescope ready for a night of collecting pointing data

Because the Earth turns constantly, the sky overhead appears to move at a constant rate. To keep objects in the telescope’s field of view, the earliest telescopes were literally mounted to clocks that moved at the sky’s rate. To make these work, you have to imagine a line in the sky that’s a projection of the Earth’s equator. Then you have to tilt your tracking axis to be at the same angle as that imaginary line in the sky. Another way to think about it is that here at Kitt Peak National Observatory, we’re at 32 degrees north latitude, so you have to tilt your telescope 32 degrees up from the southern horizon to track the sky.

Now, if you look at the photo of the WIYN Telescope above, you’ll notice that it’s mounted flat to the floor and it’s not tipped to match our latitude. That’s because it’s expensive to engineer big heavy telescopes so they can be tipped up at an angle. So, the WIYN telescope actually has to track the sky in two axes: azimuth and elevation, kind of like a radar mount. To track the sky, we have to use computers to adjust the tracking rates constantly. The computers only know how fast to track in each axis if they know where we’re pointing in the sky. If there’s an error in pointing, there’s also an error in tracking.

When I tell people I’m a writer and an astronomer who operates telescopes, it’s often assumed that I have lots of free time on quiet nights at the telescope to write. That doesn’t happen on nights of pointing maps. Instead, it’s a busy night of pointing to a star, noting how far off it was from where we expected it and then moving on again. We do this for anywhere from 75 to 100 stars with a telescope like WIYN and the exercise takes about half the night.

The way pointing and tracking are interconnected also make me think of how I use outlines as a writer. With the telescope, we can imagine that I point to a star and correct the pointing at one spot, then let the telescope track. If the computer thinks the star will be a different point in an hour than it really will be, it will track toward that different point and it won’t follow the star. You need to know where the star really will be in an hour.

For me, an outline is like a little like a pointing map. It tells me where the plot is at point A and it tells me where I want to be once I reach point B. With the telescope, it better be pointed at the star at both points A and B. An outline is more flexible. It’s more like a guideline. I try to listen to my characters when I write my outlines and make sure that points A and B make sense for them. However, sometimes as I write, I find characters do things I didn’t quite imagine the first time. The beauty of an outline is I can change point B. The challenge is that when I do, I realize I may also have to change points C, D, and E as the plot progresses!

I’ve been having a lot of fun rewriting my novel, The Pirates of Sufiro for its 25th anniversary release. I actually wrote some of the original draft when the WIYN telescope was first being built in the 1990s. Rewriting the book is the ultimate case of writing to an outline, especially since I don’t want to change it so much that people can’t pick up older editions of the sequels and follow them. I’m expanding the story and letting my characters breathe more. I’m letting them guide me and asking if what they did entirely made sense for those characters. I’m taking them from point A to point B. Those points can’t really deviate, but I do allow myself to add points A.1, A.2, and A.3 to better explain how they moved from point A to point B.

You can read chapters from the previous edition and see how I’m following my version of a “pointing map” by following me Patreon. My site is at: http://www.patreon.com/davidleesummers

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

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

2019 Storms In

I spent New Year’s Eve at Kitt Peak National Observatory as a snow storm blew over the mountaintop. Operations are scheduled at the observatory every night of the year except for Christmas Eve and Christmas. Even then, we have staff on the mountain during the holiday to service the instruments and keep an eye on the site. My job requires that I be at the telescope even during inclement weather. That’s partly because the weather is capricious and we need to be available in case the weather unexpectedly clears. I also need to service the instruments and I’m also the guy who calls the Arizona Department of Transportation to let them know how much snow they can expect at the top of Highway 386, which is the highway that leads to the top of the mountain.

Partly because I was working and partly because Kitt Peak is located on the land of the Tohono O’Odham Nation, no alcohol is allowed on the site. So, I toasted the new year with a strong cup of coffee. Because it was a stormy night, I had a good book. I was working with an observer in Wisconsin, logged into the telescope remotely from his home. He got to see the new year come in an hour before I did. When the new year came in, I received celebratory emails from my family in New Mexico and Missouri.

For us, stormy nights are an exercise in watching the weather. As I say, we want to be ready to take advantage of any clearing. Also, even if it doesn’t clear, I need to report the conditions to the highway department and fellow staff who will drive up the mountain the next day. I’m also on standby to respond to any weather-related emergencies at night. I’ve had nights at the observatory where the wind has knocked out power but the generators haven’t turned on. In that case, I need to investigate. We need the generators so we can stay in touch with remote observers and clear skies don’t care whether or not we have utility power. Also, though it’s not the most exciting aspect of my job, I’m also the guy who compiles usage statistics for the mountain during a night, which are then reported to our funding agencies.

At the end of the night, I shoveled the snow from around the door to the telescope where I was working, drove down to the main parking lot, then tromped through about four inches of snow to my dorm room. I woke up later on New Year’s afternoon to find that the road to the summit had been plowed and to see our supervisor of mountain operations using a front end loader to clear the roads on the mountain’s summit.

If we had been observing, we would have been taking images of Comet 46P/Wirtanen as it made its closest approach to the Earth. Essentially comets are dirty snowballs that provide a window into the conditions and materials available in the early solar system. Instead of watching a dirty snowball in space, we got to watch snow fall right here on Earth.

Stormy nights like the one we experienced on New Year’s Eve were part of the inspiration for the storms in my novel, The Astronomer’s Crypt. Of course, one of my jobs is to keep the bad things that happen in that novel from happening at Kitt Peak. You can learn more about the novel and watch a short trailer at: http://www.davidleesummers.com/Astronomers-Crypt.html.

Exploring Galaxies

This past week, I’ve been working at Kitt Peak National Observatory’s WIYN telescope using one of the workhorse instruments called HexPak to help astronomers better understand how galaxies work. At left is a photo I took of the galaxy M51 with the New Mexico State University 1-meter telescope. While we can learn a lot studying photos like this, wouldn’t it be nice if we could learn more, and understand what chemical elements make up the different parts of a galaxy? The instrument HexPak is designed to do just that.

One of the best tools we have for understanding the chemistry of objects in space is spectroscopy. Back in the nineteenth century, it was discovered that if you looked at heated elements through a spectroscope, you would see a characteristic set of lines in the rainbow-like spectrum. These lines are like a fingerprint for each element. It turns out that stars are really good at heating up elements! Below is a photo of the WIYN telescope with HexPak mounted.

HexPak is the white hose-like thing on the right plugged into side of the telescope. Inside that hose-like unit is a bundle of optical fibers arrayed in a hexagonal pattern. They look like this:

We can then align those fibers with a galaxy like M51 above, so different parts of the galaxy line up with different fibers. When that’s done, it looks something like this:

Now, I should note, this image was created just for illustration purposes. I haven’t tried to match the scale or alignment of my NMSU 1-meter image of M51 with the HexPak fiber array. However, you will see that different parts of the galaxy now line up with different fibers. That light is now sent downstairs to a bench spectrograph where it’s broken into its component parts. Here’s WIYN’s bench spectrograph. You can even see the rainbow like spectra on the grating at left we use to analyze the light from galaxies.

Light from each of the fibers in the array becomes a single spectrum and the image of that spectrum is recorded on a camera, shown at the right of the image above. Each one of those spectra will tell us about the elements present in each of the parts of the galaxy as lined up above. So, for example, you can figure out if the spiral arms have different amounts of a certain element than the bulge in the center. You can see what’s going on in the space between the galactic arms. If you look closely at my photo of M51, you’ll see it has bright regions that line up with parts of the spiral arm. An instrument like HexPak can help an astronomer learn if those parts of the spiral arm are different from other parts of the spiral arm, and maybe see what those regions are made of.

As I’ve mentioned in other blog posts, this work does inspire my writing. Sometimes I look at a galaxy like one we study with HexPak and think what it would be like travel between the different parts of a galaxy. M51 has a lot in common with our own galaxy. What’s it like in the arms? What’s it like between the arms? What’s it like the galaxy’s center? What’s more, working with astronomers in the control room sometimes does feel like being a crewmember on a spaceship exploring uncharted reaches. All of these elements have influenced science fiction stories like Firebrandt’s Legacy and The Pirates of Sufiro. I’m getting ready to release the former and I’m rewriting the latter with help from supporters at my Patreon site.

You can get involved in the fun by becoming a patron. My patrons are the first people who get to read new stories in my science fiction universe and they get to download complete books when they’re available. What’s more, one of my goals at my Patreon site is to make this blog ad free. If you like behind-the-scenes looks into astronomy like this one, but don’t like the ads at the blog, please consider supporting my Patreon site at: http://www.patreon.com/davidleesummers

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