blog

Joan Najita (NOIRLab)

16 February 2024

BaoBan, DESI’s ambassador for Education and Public Outreach, made a recent appearance at the 85th Annual Tohono O’odham Nation Rodeo and Parade, featuring prominently in the parade entry from Kitt Peak National Observatory (KPNO). A coyote from the wilds of Arizona, BaoBan has previously appeared in comic strips and other DESI-related public engagement activities. The DESI project is being carried out at KPNO, which is located atop I’oligam Du’ag, in the homeland of the Tohono O’odham Nation.

The story behind creating and naming our favorite coyote.

Samuel Brieden, The University of Edinburgh

May 12, 2023

Welcome our new DESI ambassador for Education and Public Outreach (EPO), BaoBan! You might have met him already, when he was presenting our powerful focal plane (see a virtual tour through it here) or wishing a happy new year. From now on, BaoBan is assisting us with science communications, as long as he is in the mood. Although BaoBan is very attracted to the Mayall telescope, he shows up at Kitt Peak quite rarely because, like other wild coyotes, BaoBan spends most of his time hunting in the Arizona mountains. But whenever we are lucky enough to be honored with his visit, an aura of ancient wisdom about life and the night sky surrounding him sparks new insights and creative ideas. It’s a bit magical!

This article is a chronology of our common history with BaoBan. From the story of his ancestors, to how he was brought to life and given a name, and finally his meaning to us, to our roots as a scientific collaboration, and to our environment.

The Tohono O’odham Nation

DESI resides in the Mayall telescope at Kitt Peak National Observatory (KPNO), which sits atop I’oligam Du’ag (audio below) in the homeland of the Tohono O’odham (audio below) Nation (TON). Since time immemorial the Tohono O’odham (TO), meaning “desert people”, have lived in the Sonoran desert and preserved their rich culture. The nation is governed by the TON Tribal Government, organized into 11 districts. You can learn more about the history and culture of the TON here. We are deeply grateful for their permission to undertake observations of the night sky within the TON homeland at KPNO, and we cannot emphasize enough that the success of our scientific mission would not be possible without the TON’s generosity.

Pronunciation of “I’oligam Du’ag”

Pronunciation of “Tohono O’odham”

The DESI logo

It is this relation to the TON that must have inspired Berkeley Lab engineer (and artist!) Robin Lafever when he created the DESI logo in 2013, and in particular the detail in the lower right corner: the profile of a howling coyote. In fact, the coyote plays an important role in the TO mythology. Robin had seven different names for the coyote in mind, his favorite being “Bao Wao Wao”. “Bao” is reminiscent of baryon acoustic oscillations (BAO), the primary cosmological observable DESI is measuring to infer the expansion history of the universe, and “Wao” represents the coyote’s howl.

A new coyote is born

The DESI logo inspired Claire Lamman, PhD student at Harvard University and member of the DESI EPO committee, to transform Robin’s profile-view creation into a fully-fledged comic figure.  As you can see in her comic strips, at first the coyote seems nice and harmless, but the sheer power of the Dark Energy Spectroscopic Instrument occasionally evokes his dark side. All Claire’s comic strips can be found here.

Amazed by his strong character, the EPO committee considered how to introduce Claire’s extraordinary art to the public. There was only one thing missing for Claire’s comic figure to become even more successful than Looney Tunes legend Wile E. Coyote: a proper name!

Setting up a poll

Several candidates emerged from our initial brainstorming, playing either on the location of the telescope (Coyote-Kitt, Maya), on the pursued science (Cosmo-Coyote, Bao), or simply on the survey name itself (Desiree). This was so much fun that we decided to poll the entire collaboration for suggestions. Other names received were Can-do Canis, Desita, and the name of the original coyote in Robin’s DESI logo: Bao Wao Wao. Around 60 collaboration members voted in just one day, and the majority decided to conduct a naming contest within the Tohono O’odham school district (see the compilation of Slack messages below).

Back to the roots

We first consulted Jacelle Erin Ramon-Sauberan, PhD Candidate at the University of Arizona, faculty at Tohono O’odham Community College, and information specialist for AURA/NOIRLab, and worked closely with KPNO. Jacelle put us in contact with the TON Youth Council  (TONYC). The TONYC consists of four representatives from each of the 11 districts, and their mission is to enhance the cultural awareness and self-esteem of TON youth within modern times by organizing social events. The Council holds monthly meetings, which are open to the public. Francine Senechal, the TONYC Manager, kindly invited us to present the coyote naming contest at a Council meeting.

At the same time we decided to reach out to the TON, two collaboration members independently raised the idea that the name include “Ban”, the word for “coyote” in the TO language. It was suggested that we connect “Ban” with the TO word “Ba:”, meaning “Where”, such that the combination “Ba:Ban” is extendable to “Where is coyote looking?” This would allude to the mysteries of dark energy DESI is trying to unravel, and sparked the obvious idea of “BaoBan”, combining “Ba:Ban” with the previous suggestions that include “Bao”.

The day of the TONYC meeting arrived, and fortunately it was held virtually so I could attend from Barcelona. After introducing DESI and the science we pursue with it, I talked about our plan to find a name for the DESI coyote. I provided a list of all the suggestions we had collected so far, as well as their variants, meanings, pronunciations, etc., and asked them to vote for the name they found most suitable. The TONYC members were interested and very keen to help. They agreed to bring the list of names into the local youth communities of the district each of them represents, engage their members to discuss the different options, and choose their favorite name.

The final decision

After thoroughly considering all names, discussing them within each district, and exchanging their ideas at a meeting, the TONYC voted, and Francine communicated the official result:

1. BaoBan
2. Cosmo Coyote

What a great choice! Within the EPO committee we immediately fell in love with the name BaoBan, as it nicely combined all the different ideas the collaboration had in mind throughout the process. “Ban” as the TO word for coyote, reminding us of the roots of where the DESI telescope is built, and “Bao” as both the sound the coyote makes, and a clear reference to DESI’s primary science goal: measuring BAO from galaxy maps. These ideas culminated in another new comic strip by Claire (below), which celebrates that together with the TONYC we found such a beautiful name for our DESI ambassador! And there is even more to the story…

An alternative meaning

Not only did the TONYC vote for the name, they also put me in contact with TO language experts Leslie Luna and Ronald Geronimo from the TO Community College, with whom I discussed the prospect of connecting “BaoBan” to the meaning behind the similar suggestion “Ba: Ban”, where “Ba:” = “Where?” as mentioned before. As it turns out, the TO expression “Ba: ‘o …” actually means “Where is …”, but this does not imply that “Ba: ‘o Ban” would mean “Where is coyote”, because “‘o” is an auxiliary verb that must be accompanied by a full verb. However, we can extend the expression to “Ba: ‘o ñia g Ban” (audio below), which literally means “Where is coyote looking?” and argue that “BaoBan” (audio below) is just the short form of that longer name. In this way, the name BaoBan also serves as a symbol that we and the TON may work together to explore new discoveries in our beautiful sky.

Pronunciation of “Ba: ‘o ñia g Ban”

Pronunciation of “BaoBan”

Final remarks

Throughout this process it has been amazing to see how an enjoyable drawing and a simple idea (finding a name for that drawing) can lead to something big, both engaging the collaboration and establishing a new link between DESI scientists and the TO community.

BaoBan symbolizes how the enormous scientific effort by ~70 member institutions with over 700 active collaboration members from all over the world is deeply connected with the TO, who share part of their homeland to discover the mysteries of our universe. BaoBan reminds us that the night sky is the same for everyone, independent of national or cultural identity. Furthermore, BaoBan reminds us to always respect our roots and our environment, and to never forget that the deeper our maps of the cosmos become, the deeper the relationships we will foster among different cultures and people.

It is no coincidence that Robin Lafever began this processes at the very moment his pencil touched paper to create the DESI logo. Robin was known as a man with a wonderfully warm and engaging personality, who delighted everyone around him with his creativity. Almost two years after his passing he would surely be flattered that people enjoy his creation enough that they continue to develop it, from Bao Wao Wao to BaoBan.

Acknowledgements

I would like to express deep thanks to all the wonderful DESI collaborators involved in this journey, those who participated in the poll and brought in their naming suggestions, and especially Claire Lamman, Angela Berti, Biprateep Dey, Parker Fagrelius, and everyone from the DESI EPO committee. Special thanks also to Daniel Eisenstein, Dustin Lang, Eric Linder, David Sprayberry, Lori Allen, Arjun Dey, Nathalie Palanque-Delabroullie, Kyle Dawson, and Michael Levi. Finally, I am indebted to Jacelle Erin Ramon-Sauberan, Francine Senechal, Leslie Luna, and Ronald Geronimo for all their effort and kindness giving me insight into their fascinating culture.

Claire Lamman, Harvard University

April 7, 2023

DESI’s planetarium show, “5000 Eyes”, was recently released to the public. It will be shown in hundreds of planetariums around the world and translated into ten languages. The support and contributions of many DESI members grew this project far beyond the little film I initially imagined. Here is how “5000 Eyes” went from the daydream of a first-year graduate student to a global production.

A couple months after delivering my final show at Fiske Planetarium, I was sitting in a session at DESI’s 2019 summer collaboration meeting. I had committed to starting graduate school at Harvard in the fall but was undecided about a research path. I was new to cosmology and just starting to learn about DESI. When a talk started to go over my head, which was often, I imagined what a planetarium show about DESI might look like.

Kitt Peak was building an outreach center and I thought it would be nice to record myself giving a short planetarium talk about DESI that could be shown at the center. A leader from our Education and Public Outreach Committee, Parker Fagrelius, encouraged me to reach out to DESI’s director, Michael Levi, and seek funding from the DESI Institutional Board. With the enthusiastic support from Parker and Michael, I formulated a proposal to create a small planetarium film. My idea was to use as much existing media as possible—such as 3D models of the Mayall telescope, footage on Kitt Peak, and DESI data, to make the best use of any resources given to the project. It received unanimous support from the Institutional Board and I found myself, a graduate student still unsure about what my thesis would be on, in charge of a full-scale production.

Fortunately, I helped Fiske make a series of short films during my time as an undergrad at CU Boulder and generally knew what went into making a planetarium film. I developed a script based on the media available and what I knew of Fiske’s software. After many iterations on the script and feedback from DESI people, we began working with Fiske to produce the movie.

There is so much to say about DESI (just check out all the blog posts below this one!), so it was not easy to decide what to include in a 20 minute movie. One idea we wanted to make sure to communicate was that advances in modern cosmology don’t magically spring from the minds of a couple scientists. It takes many people, including many young people, with a variety of backgrounds. We came up with a selection of six DESI members from four continents. The international participants all found ways to get high-quality recordings themselves! For those of us in the U.S., we were able to coordinate an in-person shoot on Kitt Peak.

Our visit to Kitt Peak was my favorite part of making the film. We had two days with the videographer from Fiske to shoot interviews and capture footage of the telescope and mountain. During this time, the Kitt Peak Staff was especially helpful and accommodating. I was even able to carry out one of my support observing shifts in person. Up until this trip, I was hesitant about representing DESI as such a new member. But observing on the mountain made me feel like I was truly part of the collaboration for the first time.

As main production ramped up, I directed the Fiske team and coordinated some additional contributions of DESI members. In particular, once I found out that David Kirkby could make a moving 3D model of the focal plane, I knew we absolutely had to include it. Who doesn’t want to fly through a forest of robots?? He put in an impressive amount of work to faithfully bring the focal plane to life and create a memorable scene.

Fiske’s team was also very excited about the film, especially once we had the go-ahead to use galaxy positions from DESI’s full year one data. This was somewhat of a technical challenge, since they were determined to render every single galaxy and, unlike DESI, did not have access to a supercomputer! The resulting fly-through is stunning. All the time I spent using DESI data in my research did not compare to soaring through the most detailed map ever made of our nearby universe in a planetarium. I am very impressed with the work of Fiske’s production team.

Because DESI is an international collaboration, it was important to make the film widely available and in multiple languages. Many DESI members have volunteered to help create translations. As of the writing of this blog, there are plans to translate the film into 10 different languages! Small planetariums all over the world are excited to have access to a free film in their local language. The film’s download site also includes an educational guide and outreach package filled with additional material that DESI people have put together. Our science will reach a large, diverse audience thanks to the work of our collaboration!

It has been exciting to see the ways that DESI members are using this film to engage with their local communities. At the premieres, it’s also been a joy to see our family members, especially kids, get a glimpse into what we work on. Looking back, it’s a bit staggering to see how much this project has grown and how many people contributed. This truly is a film about DESI, by DESI!

As of the writing of this blog, the film has been downloaded by 112 planetariums in 31 states and 24 countries.

…in Story and Science

Joan Najita, NOIRLab

April 4, 2023

One of the most spectacular things in the night sky is the Milky Way, which arches above the 4-meter Mayall Telescope in this image. The DESI survey is currently underway at the Mayall Telescope at Kitt Peak National Observatory, which is located in the Schuk Toak District of the Tohono O’odham Nation. Known as “tohmog” or “to:mog” in the language of the Tohono O’odham, the Milky Way looks like a pale band of bright specks entangled with dark clouds and glowing red wisps that shimmer like fireworks. In one Tohono O’odham story, the Milky Way was created when Coyote, the trickster, was playing in the kitchen and looking for something to eat. Hearing someone coming, he grabs a bag of flour and escapes into the sky in a great hurry. The bag tears open and flour spills out, creating the Milky Way.

There’s an echo of that story in how astronomers understand the Milky Way, just with the light and dark reversed. Here the bright white specks are not powdery flour, but stars in our galaxy. And a different kind of powdery substance, interstellar dust, creates the dark clouds, by scattering and absorbing the light from background stars. This dust isn’t the same stuff we sweep up from under our beds. Instead, it’s a kind of “soot” that forms in the atmospheres of some stars and is the stuff from which planets like Earth are made. It’s pretty valuable stuff—just like the flour that Coyote ran off with!

In this image, we can also see other interesting features. The familiar constellation of Orion the hunter is just above the Mayall Telescope to the left. And the glowing red fireworks spread across the sky are bright clouds of gas in the galaxy that are lit up by hot stars.

Recovering from the Contreras Fire

Benjamin Weaver, NOIRLab

January 24, 2023

DESI collaborators have previously reported on the Contreras Fire and how it initially affected DESI operations along with an update as personnel were able to return to Kitt Peak National Observatory (KPNO). Even as we were cleaning up KPNO and the DESI instrument in August 2022, we knew that it would possibly be several months before the Tohono O’odham Utility Authority (TOUA) could replace the infrastructure bringing electrical power and line internet (a fiber-optic link) to KPNO. In fact, line internet was not restored until December 7, 2022, almost exactly six months after the start of the fire.

The story of restoring electrical power and the generators used while restoration was in progress is definitely worth telling, and far more lengthy and detailed than the story I’d like to tell now, recovering from the missing internet connection.

The DESI Data Management team, working closely with the on-site NOIRLab personnel, developed a plan to work around the missing internet, even as DESI returned to full-night operations. It wasn’t a new plan; in fact, it was a very old plan: “Sneakernet”. The idea is that a human being (presumably wearing sneakers) can hand-carry data on physical media from one location to another, and in certain circumstances, the effective bandwidth of that transfer can be much, much higher than the bandwidth of an internet connection or other communication channel. This is actually even more true now than it was in the past, because the storage density of physical media has experienced exponential growth similar to that of Moore’s law for CPU performance. However, while Moore’s law has been showing signs of reaching fundamental physical limits, storage density trends continue to rise.

With that in mind, we purchased six 2 TB SanDisk solid-state drives (SSDs), and a few fast USB cables. There is nothing exotic about the hardware; these items would be available in many consumer electronics or department stores. Then with the 6 disks initially carried to KPNO, we would place an entire night of data (or sometimes several nights) on a SSD. One of the personnel working at KPNO would be designated to carry the SSD to Tucson at the end of the work day. Then we would pick up the disk either in person or from a drop box and copy the data to NERSC where it could be processed with the usual DESI data pipeline. Since we purchased six SSDs, that meant we always had several SSDs on standby at KPNO in case an already-transferred SSD could not be brought back from Tucson to KPNO the next day. On weekends, no one would be available to carry the SSDs, so we simply had several nights on Monday evening’s SSD.  From the point of view of the pipeline, the only difference was that an entire night (or several nights) would arrive all at once, after a delay of 1 to 3 days, instead of the normal operations procedure of one exposure at a time, almost immediately after the exposure is completed.

The DESI instrument resumed taking data starting with night 20220825 (August 25, 2022). The first SSD was brought to Tucson on September 2, 2022. This process continued until line internet was restored on December 7, 2022. The original data transfer system was ready to go at that point and was reactivated almost immediately after line internet was restored. Thus the last night of data transferred by sneakernet was 20221206 (December 6, 2022). In total, 16,726 exposures over 100(!) nights were hand-carried to Tucson. This amounts to 6.1 TB of data.

The bandwidth of hand-carried SSDs is impressive, but so is the bandwidth of modern USB cables. After some experimentation, we discovered that we could transfer data directly from the external SSD to NERSC via Globus Online, with bandwidth performance indistinguishable from the case where the data were first copied to a workstation, then transferred via Globus. In other words, the limiting bandwidth was the internet itself between Tucson and NERSC, not the internal systems of the receiving workstation.

While we were transferring DESI data with a very old system (but with the latest SSDs), we were also experimenting with a new one: Starlink. In fact there were at least two separate Starlink installations active at KPNO during the recovery.  One, which we’ll call the “DESI Starlink”, was a strictly limited command and control channel for use by instrument experts. The DESI Starlink was not used for any significant data transfer. The other, which we’ll call the “NOIRLab Starlink” was used for more general access to all of KPNO. We did use the NOIRLab Starlink for some data transfer, with mixed results.

At least currently, Starlink works best with a point-to-point style networking connection, optimized for individuals or residences, much like a residential cable modem. Since the uplink bandwidth is currently a factor of 10-20 times slower than the downlink bandwidth, it is less practically suited as a two-way connection between two substantially-sized networks, such as between KPNO and the Tucson base facilities. This manifested as a significant, recurring routing problem. Although bandwidth was adequate for interactive use and for the transfer of small data files, the connection was frequently not working and the routing systems had to be monitored constantly. Nevertheless, we were able to use the NOIRLab Starlink to maintain an off-site copy of the DESI operations database. This copy would have been impractical to maintain using daily SSD transfers, because the copy is a real-time mirror of a live database; it is more of a stream than a set of files. There were occasions where the database mirror fell behind due to interruptions in the Starlink connection. In these cases files created by the database were transferred manually on the SSDs and then once in Tucson the data files were manually added to the database mirror.

It was interesting and a good experience to transfer data over sneakernet. It was also a lot of work and hours. I want to give credit to a big team who all contributed to this effort: Keith Blaine, Paul Demmer, Matthew Evatt, Steve Grandi, Bob Marshall, Rod Rutland, David Sprayberry, Christopher Stone, Bob Stupak (NOIRLab), Martin Landriau (LBNL), and Klaus Honscheid (OSU). Here’s one job we hope we never have to do again!

January 18, 2023

The all-sky camera on the Mayall telescope were the DESI instrument is located provides a view of the entire sky above Kitt Peak National Observatory. This camera helps observers monitor weather conditions and visibility, and confirm when it is safe to open the dome above the telescope. While the skies above Kitt Peak are very often clear, that is not always the case, as shown below in a series of camera images from the night of September 23, 2022. The night began with clouds and rain, and for over an hour flashes of lightning lit up both the sky and the camera view. Finally, toward the end of the night the storm gave way to thin clouds that allowed some stars to peek through. The final frame shows the Milky Way stretched across a mostly clear sky before the series starts over.

Credit: Luke Tyas

The all-sky camera can also capture celestial events, like the lunar eclipse that occurred on the night of November 8, 2022. DESI Lead Observer Luke Tyas created the timelapse below of the eclipse from 108 individual images from the all-sky camera. At first the full moon shines brightly just right of center, reflecting so much light into the sky that only a few bright stars are visible. As the eclipse begins the moon dims to a red dot scarcely brighter than the brightest stars, and the Milky Way can be seen following the eclipsed moon across the sky. As it nears the western horizon the moon emerges from the Earth’s eclipsing shadow, re-illuminating the telescope domes visible on the horizon and washing out the Milky Way.

Credit: Luke Tyas

David Sprayberry, NOIRLab

August 25, 2022

After the Contreras Fire swept over part of Kitt Peak in June, July was devoted to restoring electrical power and water service to the mountaintop. We also carefully assessed every structure for safety, possible fire damage, and the extent of cleaning required. Currently electricity at the summit is provided solely by back-up generators (more on that later). Because the water system lost pressure during the power outage, it was necessary to flush it with chlorine and then fresh water from the storage tanks, and then have the water tested to ensure it meets EPA standards for safe drinking water (it passed!). Work at the telescopes during July was limited to skeleton crews going up for specific tasks to prevent further issues with sensitive scientific equipment. At the Mayall, this included restarting the building’s cooling system, changing filters in the purified dry air system that purges the focal plane enclosure, and changing filters in the HVAC system serving the spectrograph clean room (fondly known as “the Shack”). We also performed regular inspections in all the NOIRLab domes for leaks and electrical faults.

Beginning August 1, telescope staff were allowed to resume almost normal on-site work. At the Mayall we spent the first week cleaning everything we could find a way to reach inside the dome, and any other areas potentially affected by ash or smoke intrusion. The interior of the dome wasn’t particularly dirty, but we cleaned everything thoroughly anyway. We also removed the protective tarp and plastic sheeting from the primary mirror and prime focus corrector, and made a preliminary inspection of the optics, which look fine. During the second week of August we caught up on overdue preventive maintenance of the telescope and dome, and worked to provide a low-bandwidth internet connection to the Mayall.

Road Conditions

Throughout August, road and weather conditions have significantly limited the time our team can spend on-site. The fire damaged guardrails along the road, and there has been a lot of erosion from burned areas washing across the road during heavy rains. This extraordinary erosion has clogged many of the drainages that cross the road, sometimes causing impassible mudflows. Additionally, the fire damaged several drainage culverts under the road. The Arizona Department of Transportation (ADOT) is making progress on repairs, but they are hampered by frequent heavy summer “monsoon” thunderstorms since late July. Finally, erosion is worsening the normal amount of rockfall along the road during storms. Combined with this year’s strong, frequent storms, we are encountering more rocks and boulders in the road.

Road restrictions are still in place. Repair work frequently requires closing both lanes, and so that we interfere as little as possible ADOT requires us to go up and down the mountain in one convoy at the same times every morning and afternoon, weather permitting. NOIRLab is also concerned for site safety due to the possibility of road closures caused by mudflows or rockfall. Whenever rain begins or is threatening, everyone on the site ceases work, makes their work site safe, and assembles for departure in an early convoy.

Electrical Power and Internet

The fire damaged between 10 and 20 utility poles that bring electricity and fiber optic data to the summit. Our utility provider, the Tohono O’odam Utility Authority (TOUA), is working hard to replace the damaged poles, but they face a number of obstacles. Many of the poles are in very remote locations. Other lines and poles elsewhere on Tribal lands were also damaged by storms. And like everyone else TOUA is grappling with supply chain disruptions. It will be at least several weeks until power is restored, and then fiber optic lines will be replaced.

The observatory is currently powered by on-site backup generators. One serves the Mayall and adjacent University of Arizona buildings, and another serves the rest of the mountaintop. This is expensive in terms of refueling needs, and leaves the site without back-up power sources if one of the generators were to fail. We are in the process of renting additional generators and connecting them to use as primary power sources. Once this is done the permanent back-up generators can return to back-up status.

Keeping the generators fueled is a challenge. Not all vendors will deliver diesel fuel to our remote site. Recently our normal supplier was unable to make our regular delivery when their truck broke down, and the Mayall generator ran out of fuel before an alternate supplier could reach the summit. Storms and road conditions further complicate the situation.

For temporary internet service DESI has obtained a Starlink system and service for the Mayall. The equipment is installed and connected to one network switch in the Mayall building, but that connection requires a standalone DNS server in the Mayall to allow normal access to the many other computers and switches in the building. DNS within NOIRLab is normally provided by one central server in Tucson, but that is obviously not an option right now, so work is underway to construct this standalone DNS system.

Optics Cleaning

We want to clean both the primary mirror and front surface of the prime focus corrector with carbon dioxide “snow”, and do a wet wash of the primary mirror. However, these operations require a relative humidity of < 50%, sustained through the day, to prevent condensation after the “snow” cleanings and promote drying after the wet wash. We haven’t seen a relative humidity reading that low since the August 1 return to the summit. DESI very much wants the optics cleaned before going back on-sky, as relative throughput measurements using the guide cameras are the first tests called for. We’re waiting for the first relatively dry day to seize an opportunity for optics cleaning.

Restarting DESI

Restart of the DESI equipment can’t really begin until some internet connectivity is restored and remote monitoring of the equipment’s health is possible. The expected order of events is to re-establish a fully-functioning network with internet connectivity; then bring the DESI computer cluster back on line; and then change filters inside the focal plane cooling system, restart focal plane cooling, and test basic focal plane and fiber view camera functions.

Once the focal plane guiders are running we can perform a simple throughput test if the optics have been cleaned and observing conditions are good. The next major phase will be restoring spectrograph operations. This involves restarting the cryostat control systems, pumping down cryostats, turning on the cryocoolers, and waiting for the CCDs to reach working temperature. The spectrograph restarts do not depend on weather conditions, but we do need a back-up electrical power supply or to know that one is on the way, so we don’t risk another unplanned warm-up were the back-up generator to fail.

We don’t yet have a firm timeline for restarting DESI, as so much depends on the weather and other things we have little or no ability to control. We’re doing the best we can, and will continue to post updates as developments warrant.

Anand Raichoor and Christophe Yeche

August 22, 2022

We are glad to announce the publication on arXiv on Friday, August 19, 2022 of eight papers from Year 1 Key Project 1 (Y1KP1). These papers describe:

• how the DESI Main Survey targets are selected, along with their photometric and main spectroscopic properties (MWS: Cooper et al. 2022, BGS: Hahn et al. 2022, LRG: Zhou et al. 2022, ELG: Raichoor et al. 2022; QSO: Chaussidon et al. 2022);
• the pipeline to process those targets for DESI observations (Myers et al. 2022);
• the building of redshift truth tables based on visual inspections (Lan et al. 2022, Alexander et al. 2022).

Targets are selected from the Legacy Survey DR9 photometric catalogs, which are derived from three optical imaging surveys in the grz-bands—primarily assembled for that exact purpose, completed with the near-infrared WISE and the Gaia data.

They summarize the long-term effort by many researchers from the DESI collaboration to design a key part of the DESI experiment. All the different algorithms were tested and optimized during the Survey Validation (SV). At the end of the first part of the SV, the team has provided a final version of the target selection for all the tracers. They were finally validated during the One-Percent Survey.

With this target selection work coming to an end, the effort is now focusing on participating in the preparation of the large-scale structure analysis of the first year of data.

A second batch of papers will be published on arXiv in the coming months, prior to the SV data release…so stay tuned!

Angela Berti, University of Utah

June 29, 2022

On Saturday, June 11 a lightning strike started a wildfire in the Arizona mountains less than ten miles from the Kitt Peak National Observatory (KPNO), where DESI observing is done with the Mayall 4-meter telescope. Besides the Mayall, Kitt Peak is home to over 20 telescopes and other buildings that support scientific observations on the mountain, including dormitories where staff sleep. All of these structures were potentially threatened by the wildfire.

By Tuesday, June 14 the wildfire (now called the Contreras Fire) had spread to thousands of acres and was less than five miles from Kitt Peak. Around noon local time KPNO safety staff and the fire Incident Commander told everyone on site to immediately prepare to evacuate the mountain. Observing would have to be put on hold. The night of June 13 would be DESI’s final look at the sky for at least several weeks. Within hours a convoy was organized and began to bring those at the summit down the mountain to safety. A skeleton crew of four remained at the summit overnight for full-time fire watch.

On Wednesday, June 15 about 15 firefighters were at KPNO clearing defensive space around observatory buildings. Eight NOIRLab staff were also allowed to return for a few hours to protect critical equipment. This included taping plastic sheets and tarps over DESI’s prime focus corrector and the Mayall telescope’s primary mirror. These sensitive components could be damaged by smoke and ash should the fire get too close.

Nearly 200 firefighters were by then battling the Contreras fire, which was now only three miles away to the south. By the evening at least seven large air tankers were dropping fire retardant near KPNO.

The fire was just two miles away by the morning of June 16. Firefighting teams dropped over 100 loads of fire retardant along the perimeter of the observatory, and local news reported that the Contreras fire was the “#1 priority to wildland fire in the entire United States” due to the value of KPNO.

By early morning on Friday, June 17, the fire swept over the Southwest Ridge section of the observatory, home to MDM Observatory (two optical telescopes), the Arizona Radio Observatory, and the NRAO Very Long Baseline Array radio dish. KPNO webcams mounted on some of the telescopes stopped returning images not long after as the fire disrupted electricity and internet service on the mountain. DESI collaborators around the world could no longer monitor instruments remotely due to the loss of connectivity.

Good news finally came around midday on June 17 as light rain began to fall in nearby Tucson, Arizona. In the afternoon word came from two employees of NOIRLab who were on the mountain assisting firefighters with KPNO’s water system that no fire had reached the Mayall telescope. By the time the Contreras fire was 100% contained it had spread to nearly 30,000 acres. The fire destroyed four “non-scientific” structures, but none of the more than 20 telescopes atop Kitt Peak were burned!

On Tuesday, June 21, the DESI collaboration gathered in Berkeley, California for its first in-person meeting since 2019 due to the covid-19 pandemic. Many collaboration members who couldn’t be there in person joined remotely, and everyone expressed their gratitude for the incredible firefighters who saved DESI and KPNO from the Contreras fire.

Claire Lamman, Harvard University

February 28, 2022

We all know the recipe for a great scientific collaboration: novel technology, topical science goals, and cool stickers.

In November 2021 we achieved the final ingredient with the launch of our official DESI Swag Shop.

The DESI shop is hosted on the third-party site Redbubble. This is a place for independent artists to sell their designs on a variety of products—everything from t-shirts to shower curtains. While not specifically designed for organizations to distribute swag, it is a convenient way to make a large selection of items easily available to individuals around the world. We set our shop settings to 0% profit margin—which means DESI makes no money and the prices are as low as possible.

In honor of the opening of our online shop, I made a special DESI-gn that highlights both the science and instrumentation parts of our collaboration. “Dark Energy” is represented by a map of large-scale structure, and “Spectroscopic Instrument” is represented by our focal plane and its 5,000 robotic positioners.

Four months later, 486 items have been purchased from our shop. The most popular are:

1. DESI Logo sticker
2. DESI Plane sticker
3. DESI Logo magnet
4. DESI Plane t-shirt
5. M31 Focal Plane sticker

Beyond stickers and t-shirts the shop also has masks, mugs, puzzles, posters, and even socks. Here’s a look at how the popularity of these items compare:

Stats like this may be helpful for conference organizers deciding what types of merch products to use. The key takeaway here: never forget the stickers!

Edmond Chaussidon, CEA Saclay

January 12, 2022

Although DESI will be able to collect 5,000 spectra simultaneously, galaxies are still too numerous to be all observed during the next five years of observation. Target Selection (TS) is a crucial step to identify which objects to observe during the spectroscopic survey.

To constrain the cosmic expansion history through measurements of Baryon Acoustic Oscillations, DESI probes the matter in the Universe with four different tracers:

• Bright galaxies (BGS) in the redshift (z) range 0.05 < z < 0.4
• Luminous Red Galaxies (LRG) for 0.4 < z < 1.0
• Emission Line Galaxies (ELG) for 0.6 < z < 1.6
• Quasars (QSO) for 0.9 < z < 2.1

Quasars will also probe the Universe at higher redshift (z > 2.1) through Lyman-alpha forest studies measuring the light absorption by the gas in front of quasars.

Easy to say that we want to select different galaxy types, but how? The main information we need are the galaxy colors, which we can determine thanks to the measurements provided by photometric surveys. We used the catalogs of the DESI Legacy Imaging Surveys, a program conducted over more than 14,000 square degrees of sky from the Northern hemisphere, in three optical bands: g (in the blue-green), r (in the red), and z (in the red/near-infrared, and not to be confused with redshift!). The data were collected via three independent programs:

• The Beijing–Arizona Sky Survey (BASS) observed ∼5,100 square degrees of the North Galactic Cap (NGC) in g and r using the 2.3-meter Bok Telescope.
• The Mayall z-band Legacy Survey (MzLS) provided z-band observations over the same footprint as BASS using the 4-meter Mayall Telescope.
• The Dark Energy Camera Legacy Survey (DECaLS) was performed with the Dark Energy Camera (DECam) on the 4-meter Blanco Telescope. DECaLS observed the bulk of the Legacy Imaging Surveys footprint in g, r, and z.

These optical data were complemented by two infrared bands from the all-sky data of the WISE satellite, namely: W1 (3.4 μm) and W2 (4.6 μm).

The selection of the BGSs, LRGs and ELGs was mostly done based on conditions on the source colors. For the QSOs, however, which are harder to select because their colors are quite similar to those of the overwhelming stellar background, we developed a more complex approach based on machine learning. To further reduce the contamination of the sample from unwanted stars or galaxies, we applied an additional constraint on source magnitude. All these conditions were tuned on previous spectroscopic samples as those from the BOSS/eBOSS program. But of course, we also intensively tested them during the Survey Validation (SV) phases emulating a nominal observation with DESI. Voilà! Lo and behold, they all give very satisfying results.

DESI is now on sky, observing every night the quasars and the galaxies that we selected using these algorithms, on its way to build the largest 3D map of the Universe to date!

The Target Selection and Survey Validation steps are described in great detail in the upcoming eight scientific papers (one Overview, two for the SV, four for the TS and one for the Milky Way Survey). Pipeline and algorithms for data reductions and operations will be described in another set of five scientific papers later. So, stay tuned!

For the curious, below are more details on how we proceed for the four classes of targets, and some information about the density of objects we thus select.

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Bright Galaxy Target Selection

Star–galaxy separation in BGS is performed using a G_Gaia – r_raw cut. This criterion exploits the fact that the Gaia magnitude is measured with an aperture of a space-based point-spread function (PSF) while the Legacy Imaging Surveys magnitude captures the light from the entire source. This cut separates point sources (stars) from extended sources (galaxies). This selection will observe ~850 targets per square degree. (See Hahn et al., in prep.)

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Luminous Red Galaxy Target Selection

LRG selection is done by the cut (red line) in the (r – z) – (z – W1) space. This selection uses the W1 infrared band to separate galaxies (color points) from stars (grey points). The different colors show the redshift of the galaxies in the color–color space. This selection will observe ~615 targets per square degree. (See Zou et al., in prep.)

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Emission Line Galaxy Target Selection

To avoid stellar contamination (black smooth line) in the target selection, ELG selection uses a cut in (r – z) – (g – r) space. The color histogram is the redshift distribution of ELGs in the color space. This selection will observe ~2,387 targets per square degree. (See Raichoor et al., in prep.)

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Quasar Target Selection

Only point sources are considered during the selection and the target selection aims to separate quasars from stars. However, the separation between these two classes is less obvious than in the previous cases. A more sophisticated selection has to be applied. Quasars are selected via a Random Forest classification instead of the classical color cuts selection done in previous spectroscopic surveys. The idea of the selection is to separate quasars from stars based on the “infrared excess” of QSOs. The stellar locus is illustrated by the red line and the quasars by the blue/green/yellow points. This selection will observe ~308 targets per square degree (see Chaussidon et al., in prep.).

David Lee Summers, Kitt Peak National Observatory

November 17, 2021

Many people who hear the word “astronomer” imagine a scientist spending long nights in an observatory dome peering through a telescope’s eyepiece. In fact, when the Nicholas U. Mayall telescope was commissioned in 1973, astronomers could sit at the telescope’s focus to operate the cameras. In those early days, the telescope operator worked at an analog console in a control room inside the dome. Over the years those telescope controls migrated to computers and the astronomers joined the telescope operators in the control room.

The control room is a cozy space. It’s a long, narrow room. The old analog console dominates one wall. Desks and shelves line the other walls. The closest restroom is two floors below the control room and the control room didn’t even have a sink until one was installed circa 2010. A small microwave allowed the operator and observers to heat their night lunches. When planning for the DESI survey began, people soon realized this space was far too small for the number of scientists who would need to collaborate on a given night while commissioning the instrument. Even during regular observing, it was expected that three or four people would need to be in the control room at the same time.

A new, larger space within the Mayall building was identified to serve as the control room. A former recreation room on the so-called Utility floor was renovated into a modern control room in 2017. Even before DESI operations began, we moved into the new control room to finish the Mosaic Z-band Legacy Survey. The new control room allowed several scientists to collaborate during the night. There was plenty of desk space for computers and monitors to watch all the telescope and DESI functions. An adjoining room held a small kitchenette and a meeting room. What’s more, restrooms were only one room further on. The U-floor control room seemed a vast improvement as a practical workspace—at least until the unexpected happened and operations had to be stopped in March 2020 for the COVID-19 pandemic.

Although we paused on-sky DESI commissioning, much thought was given to safe operations. Clearly we couldn’t have several people working together in one enclosed room, especially in the days before a vaccine had been developed and before the effectiveness of masks had been demonstrated.

Before the DESI installation began, some astronomers who used Kitt Peak facilities already observed remotely from their home institutions. They could log in and control an instrument through the internet and communicate with the telescope operator through video conferencing software. This idea became the core for new, safe DESI operations. The telescope operator would return to the old control room next to the telescope. A lead DESI observer would work in the new U-floor control room. All other collaborators would work either from home or their home institutions and communicate with the team at the telescope over Zoom.

As an operator who has worked at Kitt Peak since the 1990s, it’s been gratifying to watch DESI’s development and see this next step in the Mayall Telescope’s illustrious history. It’s also been gratifying to see how elements of the telescope’s legacy along with new technology have kept us operating through these challenging times.

Adam Bolton, NOIRLab

November 1, 2021

DESI collaborator Dr. Frank Valdes, a scientist at NSF’s NOIRLab, has been honored with the 2021 ADASS Prize for an Outstanding Contribution to Astronomical Software. The award recognizes Frank and two other colleagues for their foundational roles in creating the Image Reduction and Analysis Facility (IRAF) software system. IRAF was launched over three decades ago as a pioneering project to create general-purpose software tools that would allow astronomers to translate the images taken by telescopes into calibrated data products suitable for quantitative scientific analysis. In the years since its initial release, IRAF has been used in nearly 25,000 scientific publications. Most significantly for DESI, all the images collected by the Legacy Surveys (DECaLS, MzLS, and BASS) to enable DESI’s spectroscopic target selection were processed through an IRAF-based pipeline created by Frank and operated by him and other NOIRLab staff members. The DESI Collaboration congratulates Frank on this well-deserved recognition!

John Della Costa, University of Florida

October 2, 2021

Astronomy is fun. But have you ever wanted to make it even better? Then why not try upgrading your 100 million dollar world class astronomical instrument! This may sound like an extremely difficult challenge that would require more than 30 people and many weeks of labor intensive work around the clock, and you’d be right! But with this handy DIY guide, you’ll be able to contribute in no time at all! So, follow along with this step-by-step tutorial and you’ll be observing the universe with your unrivaled, upgraded instrument faster than you can say, “Oh no, I only see 12 positioners but I plugged in 13. Please don’t make me take the whole petal apart again!”

Step 1: Get to the mountain
Remote mountaintops in dry locations are the best places to house telescopes. If you’re lucky, your amazing instrument will be located on the top of one in Southern Arizona. But first, you have to get to it! After your 4 hour plane ride in the lap of luxury, rent a vehicle and drive for 50 minutes until you get to the mountain road gate. Make sure to remember the combination for the lock (you still have the email with it, right?). Next, drive up the winding path to the summit. Try not to break any vertebrae as your neck becomes rubber from the occasional glimpses of the massive telescope your instrument desperately clings to. You’ve done it, you’re on the mountain!

Step 2: Get your safety briefing
Your safety briefing is one of the most important steps required for you to upgrade your instrument. When you’re on the mountain, there will likely be many creatures just waiting to kill you! So, be prepared, and never, ever, leave your food next to your bed as you sleep with the window open.

Step 2.5: Did you get food for your stay?
Did you really forget to get food for your 3 week stay on a mountain? Did you think you were going to subsist off of cacti and spiders? Now, drive back down the mountain, go to the grocery store another hour away, and drive back another hour again. Make sure you bought enough food to completely fill the freezer in the house so that you’ll have extra to throw out when you leave.

Step 3: Start disassembly of the first petal
By the time you get back to the dome after gluing your freezer shut, Petal 4 should be out of the telescope. But, before you start disassembly, make sure to test those pesky positioners with their mysterious ailment that nobody can understand. Now you’re ready to start disassembly! Just kidding, you have to take off the covers first. Make sure you use the correct tool or you might strip the… You stripped the screws, didn’t you? Well, that’s ok! Just make sure you have your hammer and drill close by so you can start going to town on your extremely fragile, multi-million dollar petal! But luckily, no other screws will be stripped on any other petal (foreshadowing). Now that you’ve spent many precious hours on this, you can start to disassemble the petal! Make sure as you pull out each positioner’s connector you really get your thumb and index finger in there. Don’t worry though, this definitely won’t leave you with nubs after doing it 5000 times… Wow, you’re fast! It only took you 3 hours of nonstop work! You should probably go home now and get some rest. Luckily your accommodations are only a 5 minute drive away (on the top of a mountain in complete darkness)!

Step 4: Start petal reassembly
Once the petal is completely taken apart, all 500 positioners are successfully unplugged, and all the transverse boards are out, you can get started on petal reassembly! Make sure not to snap any fibers, it’s not like they’re irreplaceable or anything. Finally, after two to three days of nonstop work, you’ll have your petal completely put back together. Now, just put it back in the telescope with that giant crane attached to the dome that lifts the 200 pound petal 30 feet into the air (seriously though, this part is terrifying to watch).

Step 5: Rinse and repeat!
Now all you have to do is repeat steps 3 and 4 seven more times (you’ll probably only be able to get 8 petals done during your 3 weeks on the mountain)!

Step 5.5: Take some time off
Make sure to take a day off here and there. Go for a hike, see some cacti (make sure to pick up their fruit with no hesitation, they can’t hurt you!), drive down the mountain and back up again, and enjoy the 110 degree weather (it’s a dry heat)!

Step 6: Make sure it’s not too easy
Be sure that Petal 6 has a lot of issues so that you have to take it apart and put it back together. Twice! But don’t worry, it’s great practice, and your thumbs will thank you later.

Step 7: Bask in the glory of an upgraded instrument
Now that you’ve completed the disassembly and reassembly of your world class multi-object spectrograph, you can start observing, again, and get back to deciphering the mysteries of the universe!

Step 7.5:
Wait, you’re telling me we have to test the instrument for weeks after reassembling it? Will we ever get to start observing again?

Well, while you wait, you can look back at the over 5000 pictures you took while you were on the mountain and think back at the amazing, once in a lifetime experience you had while helping to upgrade one of the best astronomical instruments on planet Earth, and remember all the skills you learned and all of the amazing people you met along the way.