Tag Archives: DESI

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.

Refitting the Mayall: Teardown

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

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

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

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

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

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

Hunting Asteroids

I rang in the new year by helping Robert McMillan, Jim Scotti, and Melissa Brucker from the University of Arizona hunt for potentially hazardous asteroids in our solar system at the Kitt Peak 4-meter telescope. This is important work since asteroid impacts are one of the few completely predictable and preventable natural disasters. Here I am at the telescope console.

As it turns out, this observing run was something of a bittersweet milestone. Bob, Jim, and Melissa are the last scheduled visiting observers on the 4-meter. At this point, we have about five more weeks of observing with a scheduled imaging survey program and then the telescope shuts down so it can be refitted with an instrument called the Dark Energy Spectroscopic Instrument, or DESI. DESI will measure the effect of dark energy on the expansion of the universe. It will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3-dimensional map spanning the nearby universe to 10 billion light years.

So, what about the asteroids? Well, the good news is that there are smaller telescopes on Kitt Peak devoted to the search. The reason Bob, Jim, and Melissa use the 4-meter is that it allows them to look for more distant asteroids on nights when the small telescopes are not as effective. In this case, we were attempting our observations during the full moon. Because the moon is so bright, it’s hard to see faint, distant objects with small telescopes because you need to expose on the sky for a long time. The 4-meter can take shorter exposures and still detect these faint objects without having the skylight swamp the exposures. In the meantime, Bob, Jim, and Melissa have applied for time on other telescopes around the world to do the work they were doing on the Kitt Peak 4-meter.

Often times when I’m involved in these runs, I’m asked if I’ll let people know if something is going to fall on us. Well, if I know, I’ll tell. However, what we often do is identify small objects a long ways away. It’ll usually take more than the observations we get to determine the object’s orbit and find out whether or not it presents a serious hazard.

So what actually happens if we discover an asteroid that might hit the Earth? I found this NASA video that gives a nice explanation. I notice there is also an image credit from my friend Mike Weasner, a talented amateur astronomer who is also a science fiction fan.

If you want to get more of a sense of what life is like behind the scenes at an astronomical observatory, be sure to read my novel The Astronomer’s Crypt. You can learn more about the novel and get a sneak peak at http://www.davidleesummers.com/Astronomers-Crypt.html

The Robots Are Taking Over

I spent this past weekend at Bubonicon in Albuquerque, New Mexico. Yesterday, I moderated a panel called “Are Robots Still Scary? Danger Will Robinson!” As it turns out, I suggested this panel to the event organizers because it occurred to me that I work with a robot quite a bit at Kitt Peak National Observatory and it’s a far cry from the anthropomorphic robots of pulp sci fi and probably more irritating at times than scary. The robot I’ve spent most of my time with is called the Hydra gripper. The reason it can be irritating, is that I’m one of the guys who has to go fix it when it breaks down!

hydra

The gripper is on the right-hand side of the photo above. Its job is to pick up the fibers on the left side and position them on the plate so that they line up with objects on the sky. When the telescope is pointed at the target, light from the objects will go downstairs to a spectrograph, where it will be broken into a spectrum and projected on a camera. Astronomers can take that light and analyze it to understand the chemical composition of the objects they’re studying. These objects can range from stars, to galaxies, to nebulae. Some objects are nearby, others are among the most distant in the universe.

The reason for this post’s title, is that we’re about to get another robotic spectrograph at Kitt Peak. This one is called DESI (which stands for Dark Energy Spectrographic Instrument). Hydra allows us to take spectra of upwards of 200 objects at a time. DESI will let us take spectra of 5000 objects. You can read more about DESI in this press release from the Department of Energy’s Berkeley Lab. The goal of the instrument is to get spectra of all the known galaxies obtainable by the 4-meter in order to understand the phenomenon that’s been dubbed “dark energy.” Along the way, we’ll build an incredible database of spectra available to the entire astronomical community.

This week, I’ll be helping to test a prototype of DESI on the Mayall 4-meter telescope. The fibers of DESI are so closely packed that they aren’t moved around by a system like a gripper. Instead, each fiber is a little robot that turns on its own to optimize its position on the sky. Because of this project and the number of people it takes to get a project like this off the ground, DOE has helped to fund a new, larger control room for the Mayall. You can see the original on the left below. The new control room is on the right.

New-Old Control rooms

As it turns out, ghosts and stories of haunted observatories feature prominently in my forthcoming novel, The Astronomer’s Crypt. Our new control room is one of the “haunted” spaces in the Mayall. It used to be an old lounge and there were two rocking chairs that would sometimes be seen to rock on their own even when no one is in there. It remains to be seen if there are any ghosts, or if this motion was just due to sway of the building. If there are ghosts in the building, I hope they like company, because there’s going to be a lot of it in the coming years!