Tagged: LBL DESI Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 2:58 pm on October 5, 2016 Permalink | Reply
    Tags: , , , , LBL DESI, , , The Space between Stars and Galaxies,   

    From Cornell: Women in STEM – “The Space between Stars and Galaxies” Rachel E. Bean 

    Cornell Bloc

    Cornell University

    10.5.16
    Jackie Swift

    1
    Rachel E. Bean

    Mystery shrouds the birth of our universe. In a fraction of a second, the universe transformed from a size smaller than a subatomic proton through expanding exponentially faster than the speed of light, according to the Big Bang theory. At the heart of this event lies the explanation for all the constituents of the cosmos today. If the moment of the Big Bang can be understood, we may finally have the theory of everything that can reconcile the quantum Standard Model of particle physics with Einstein’s general theory of relativity, which holds that gravity is a result of the curvature of space and time.

    Even the most powerful particle physics experiments on Earth don’t have enough clout to recreate the conditions in the early universe. We can find evidence of them, however, in the cosmic microwave background (CMB), which functions like a fossil remnant of that very early universe, says Rachel E. Bean, Astronomy.

    CMB per ESA/Planck
    CMB per ESA/Planck

    “The CMB was made about 400 thousand years after the start of the universe,” she says. “It’s a pristine glimpse of what the universe was like at that instant, and buried inside that signal is a signature of what happened a trillionth of a second after the Big Bang.”

    The Early Universe and the Cosmic Microwave Background

    The CMB is a faint glow in the microwave wavelength that can be seen with telescopes that detect microwave radiation in the space between stars and galaxies. It has been traveling toward us for 13 billion years carrying information about those early moments. “At that time the universe was governed by quantum physics at a level that we don’t think we fully understand,” Bean says. “As we go back in time, the universe gets smaller, hotter and denser. At its very earliest instances, it was at temperatures and densities that we can never recreate on earth.”

    In an effort to understand physics at those extreme properties, Bean looks for tiny temperature fluctuations in the CMB. These were generated a trillionth of a second after the Big Bang during a process called primordial inflation when the universe is thought to have expanded faster than the speed of light for a brief time. “We have to describe how quantum properties behave with gravity and space and time,” says Bean. “We don’t know how to do that. The only way we can try to figure this out is to look at these very early moments.” Bean hopes to connect these temperature fluctuations in the CMB to one of the potential theories—especially string theory—that are candidates to reconcile quantum mechanics and the general theory of relativity.

    The CMB can also tell scientists about the effects of gravity on objects through time.

    “The CMB has essentially seen everything that has been created since it was formed,” says Bean. “It traveled through the universe as it evolved, and as it did that it had the signatures of that history imbued upon it.”

    Massive Galaxy Clusters, Dark Matter, and Dark Energy

    Bean is interested in the information the CMB carries about its travels through the most massive objects in the universe: galaxy clusters. These are about a thousand times larger than our galaxy. As the CMB passes through a cluster, the heat of the cluster and its movement leaves a sort of Doppler shift on the frequency of the light from the CMB. “We can use the CMB as a motion detector for these clusters,” Bean explains. “We can see how fast they were moving when the CMB passed through them. This is useful because those clusters were moving because of the properties of gravity at that time.”

    Bean will also be looking for evidence of the effects of dark matter and dark energy—two components of the universe that we cannot see. They do not emit light or absorb it, and none of our instruments can detect them. Scientists think that 95 percent of the matter in the universe is dark matter and dark energy, which change the properties of how gravity behaves. The only way to learn about the properties of these components is to look at their impact on astrophysical bodies such as galaxy clusters, Bean says. “By looking at how fast the galaxy clusters were moving in the past, we can test the properties of gravity and dark matter.”

    Big Bold Telescopes, Up Soon

    Astronomers will be able to do that in unparalleled detail over the next decade when four new telescopic surveys come online. These large-scale structure surveys will look at millions to billions of galaxies. They will either take multicolor images of them, revealing through color different physical properties, or they will record the galaxies’ spectra, the emission or absorption lines of light of particular wavelengths, which pinpoint the galaxies’ positions in space. “We’re going to be able to survey out billions of light years to be able to understand the structure of our universe with unprecedented precision,” Bean says.

    Two of the telescopes will be ground-based and two will be space-based. Bean is the leader of an international collaboration of approximately 500 scientists—the LSST Dark Energy Science Collaboration—that will be using the data from one of the ground-based photometric imaging telescopes, the Large Synoptic Survey Telescope (LSST), which is an international venture led by two United States agencies, the National Science Foundation and the United States Department of Energy.

    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
    LSST Interior
    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST telescope, currently under construction at Cerro Pachón Chile

    The LSST will be commissioned in 2019 with the first surveys coming online in 2021. Bean is scrambling to prepare for the challenge of analyzing all the anticipated data. “It’s going to be like a massive gush,” Bean says. “If we’re able to analyze it properly, we will get orders of magnitude improvement in our understanding of the properties of the cosmos.”

    The LSST will share the ground-based spotlight with another state-of-the-art telescope, the Dark Energy Spectroscopic Instrument (DESI), a United States Department of Energy initiative, which will come online in 2019.

    LBL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018
    “LBL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018

    The final two telescopes, both space-based, will be launched in the next decade: the European Space Agency’s Euclid in 2021 and the National Aeronautics and Space Administration’s Wide Field Infrared Survey Telescope (WFIRST) in the mid-twenties.

    ESA/Euclid spacecraft
    ESA/Euclid spacecraft

    NASA/WFIRST
    NASA/WFIRST

    Bean plans to take the new information on the nature of galaxies provided by the four surveys and combine it with data on the motions of galaxy clusters gleaned from the CMB. Altogether they should help her and other cosmologists uncover the true properties of dark matter and dark energy, “We’ll be able to test whether general relativity holds on a cosmic scale,” Bean says. “That’s really exciting!”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

    Advertisements
     
  • richardmitnick 12:11 pm on August 9, 2016 Permalink | Reply
    Tags: 3-D Galaxy-mapping Project Enters Construction Phase, , , LBL DESI   

    From LBL: “3-D Galaxy-mapping Project Enters Construction Phase” 

    Berkeley Logo

    Berkeley Lab

    August 9, 2016
    Glenn Roberts Jr.
    geroberts@lbl.gov
    510-486-5582

    DESI, the Dark Energy Spectroscopic Instrument, will measure light from 35M galaxies to provide new clues about dark energy.

    1
    The first “petal” machined for the Dark Energy Spectroscopic Instrument (DESI) is shown in these photos. Ten of these petals, which together will hold 5,000 robots (like the one in the lower right photo)—each pointing a thin fiber-optic cable at separate sky objects—will be installed in DESI. (Credit: Joe Silber/Berkeley Lab)

    LBL/DESI Dark Energy Spectroscopic Instrument Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA
    LBL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA
    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA

    A 3-D sky-mapping project that will measure the light of millions of galaxies has received formal approval from the U.S. Department of Energy to move forward with construction. Installation of the project, called DESI (Dark Energy Spectroscopic Instrument), is set to begin next year at the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz., with observations starting up in January 2019.

    This latest DOE approval step, known as Critical Decision 3, triggers spending for major components of the project, including the remainder of the 5,000 finger-width, 10-inch-long cylindrical robots that will precisely point the fiber-optic cables to gather the light from a chosen set of galaxies, stars, and brilliant objects called quasars. The spending will also be used to complete the set of 10 fiber-fed spectrographs that will precisely measure different wavelengths of incoming light.

    This light will tell us about the properties of the galaxies, stars, and quasars, and most importantly, how quickly they are moving away from us—light from objects that are moving away from us is shifted to redder wavelengths (“redshift”). These details can help us learn more about the nature of dark energy that is driving the accelerating expansion of the universe. DESI’s observations will provide a deep look back in time, up to about 11 billion years ago.

    “We’re very excited—ecstatic—that we’ve gotten to this step,” said DESI Director Michael Levi of Lawrence Berkeley National Laboratory’s (Berkeley Lab) Physics Division.

    “This brings DESI closer to its five-year mission to go where no map has gone before in the universe,” added David Schlegel of Berkeley Lab, a co-project scientist for DESI. “I can’t wait.”

    3
    The Dark Energy Spectroscopic Instrument (DESI), shown in this illustration, will be mounted on the 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, Ariz. It will collect data on light from 35 million galaxies and quasars to make the biggest 3-D map of the universe ever. (Credit: R. Lafever, J. Moustakas/DESI Collaboration)

    DESI’s robotic array will cycle through separate sets of objects several times each hour during its five-year mission. It will look at one-third of the sky and will capture more than 10 times as much data as a predecessor called BOSS, the Baryon Oscillation Spectroscopic Survey.

    DESI will provide a more detailed look at the patterned clustering of visible matter in the night sky across a larger range of distances. This clustering was set in motion by a cooling process in the early universe that produced sound wave-like oscillations through a combination of pressure and gravitational forces. DESI will also provide a more precise measure of how the universe has spread out over time, and help us understand galaxy evolution and dark matter, which is invisible but inferred from its gravitational effects on normal matter.

    “The DESI map of galaxies will reveal patterns that result from the interplay of pressure and gravity in the first 400,000 years after the Big Bang,” said Daniel Eisenstein of Harvard University, a DESI co-spokesperson. “We’ll be using these subtle fingerprints to study the expansion history of the universe.”

    The DESI collaboration has grown to include about 300 scientists and engineers from about 45 institutions around the globe. The leadership team includes Robert Besuner of the UC Berkeley Space Sciences Laboratory, who has stepped in as the new DESI project manager. He replaces Henry Heetderks of the Space Sciences Laboratory, who retired June 29.

    The project’s multiple sources of financial support and its use of an existing telescope have helped to keep DESI on a fast track, Levi said. “Now the hard work accelerates,” he added.

    With the latest approval, a pipeline of development efforts will move quickly toward completion. Six large lenses, each worth $1 million and measuring up to 1.1 meters in diameter, await treatment with an antireflective coating to improve their transparency.

    The lenses will be housed in a metal frame being constructed at Fermi National Accelerator Laboratory (FNAL) to form a minivan-sized stack known as an optical corrector. This device will be the first piece of equipment installed at the Mayall Telescope for DESI in 2018.

    To prepare for DESI data analysis, software engineers are using supercomputers at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC) to simulate the data gathered by DESI. NERSC is a DOE Office of Science User Facility.

    Also, three sky surveys are now collecting images of the faint galaxies that DESI will target. Data from these surveys is periodically released on a public site at http://legacysurvey.org, and observational data gathered by DESI will also be publicly released.

    “I like to think of the imaging surveys as building the 2-D maps, while DESI adds the third dimension,” said Dustin Lang, a DESI imaging scientist with the University of Toronto. ”The crucial third dimension allows us to measure how galaxies cluster together in space over the history of the universe.”

    4
    A view of the ProtoDESI setup during assembly at Berkeley Lab, with the underside of the robotic fiber-positioners visible at left. ProtoDESI is now installed at the 4-meter Mayall Telescope at Kitt Peak National Observatory near Tucson, Ariz. (Credit: Paul Mueller/Berkeley Lab)

    A prototype instrument called ProtoDESI is now installed at the Mayall Telescope for a two-month run. ProtoDESI uses four small robots to test out the fiber-positioning system and includes cameras and other components to prepare for the full DESI project.

    “This is a great time to be an astroparticle physicist. DOE’s program of building new instruments like DESI will provide the data that will let us take the next step in understanding the formation of our universe,” said Fermilab’s Brenna Flaugher, co-project scientist for DESI and project manager of DECam, the camera for the Dark Energy Survey, an ambitious imaging survey currently underway.

    DESI is one of several planned next-generation observatory projects designed to confront cosmic mysteries including dark energy, dark matter, and the universe’s first light, known as the cosmic microwave background.

    “DESI will be able to make a 3D map of the universe using an order of magnitude more redshifts than currently exist,” said Risa Wechsler of the SLAC National Accelerator Laboratory, Stanford University and DESI co-spokesperson. “This will allow us to probe the physics of the universe and discover the true nature of dark energy.”

    ###

    DESI is supported by the U.S. Department of Energy’s Office of Science; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico; the Ministry of Economy of Spain, and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.

    Current DESI Member Institutions: Aix-Marseille University; Argonne National Laboratory; Barcelona-Madrid Regional Participation Group; Brookhaven National Laboratory; Boston University; Carnegie Mellon University; CEA-IRFU, Saclay; China Participation Group; Cornell University; Durham University; École Polytechnique Fédérale de Lausanne; Eidgenössische Technische Hochschule, Zürich; Fermi National Accelerator Laboratory; Granada-Madrid-Tenerife Regional Participation Group; Harvard University; Korea Astronomy and Space Science Institute; Korea Institute for Advanced Study; Institute of Cosmological Sciences, University of Barcelona; Lawrence Berkeley National Laboratory; Laboratoire de Physique Nucléaire et de Hautes Energies; Mexico Regional Participation Group; National Optical Astronomy Observatory; Siena College; SLAC National Accelerator Laboratory; Southern Methodist University; Swinburne University; The Ohio State University; Universidad de los Andes; University of Arizona; University of California, Berkeley; University of California, Irvine; University of California, Santa Cruz; University College London; University of Michigan at Ann Arbor; University of Pennsylvania; University of Pittsburgh; University of Portsmouth; University of Queensland; University of Toronto; University of Utah; UK Regional Participation Group; Yale University. For more information, visit desi.lbl.gov.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 4:17 pm on June 13, 2016 Permalink | Reply
    Tags: , , , LBL DESI,   

    “From LBL: “Researchers Gear Up Galaxy-seeking Robots for a Test Run” 

    Berkeley Logo

    Berkeley Lab

    June 13, 2016
    Glenn Roberts Jr
    geroberts@lbl.gov
    510-486-5582

    1
    Parker Fagrelius of Berkeley Lab and UC Berkeley inspects ProtoDESI, a prototype system for the Dark Energy Spectroscopic Instrument. ProtoDESI will be tested at the Mayall Telescope in Arizona in August and September. (Credit: Paul Mueller/Berkeley Lab)

    A prototype system, designed as a test for a planned array of 5,000 galaxy-seeking robots, is taking shape at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

    Dubbed ProtoDESI, the scaled-down, 10-robot system will help scientists achieve the pinpoint accuracy needed to home in on millions of galaxies, quasars and stars with the Dark Energy Spectroscopic Instrument (DESI) planned for the Mayall Telescope at Kitt Peak National Observatory near Tucson, Ariz. ProtoDESI will be installed on the Mayall Telescope this August and September.

    LBL/DESI spectroscopic instrument
    LBL/DESI spectroscopic instrument

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA
    NOAO Mayall 4 m telescope interior
    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA

    The full DESI project, which is managed by Berkeley Lab, involves about 200 scientists and about 45 institutions from around the globe. DESI will provide the most detailed 3-D map of the universe and probe the secrets of dark energy, which is accelerating the universe’s expansion. It is also expected to improve our understanding of dark matter, the infant universe, and the structure of our own galaxy.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt
    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey
    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    2
    ProtoDESI will have 10 rodlike robots (above, left)—10 inches long and designed to point fiber-optic cables at sky objects and gather light—and 16 light-emitting devices (middle) to ensure the system is targeting correctly. The ProtoDESI setup (right, with robots and light rods shown in yellow circle) will be tested at the Mayall Telescope in Arizona from August-September.

    4
    DESI robots (right) will poke out from 10 wedge-shaped “petals” that will be fitted together in a Focal Plate Assembly (left).

    6
    DESI’s robots can point their fiber-optical cables (red dots, upper left) at any sky object (blue dots) within a 12-millimeter-diameter area. A rendering of the robotic array (right) with an overlay of a star field that can be reached by one robot.

    7
    A rendering of DESI inside the Mayall Telescope (left). The robotic array is contained in a gray-shaded structure pointed toward the top of the dome.

    (Credits: Berkeley Lab, University of Michigan, DESI Collaboration, NOAO.)

    The thin, cylindrical robots that will be tested in ProtoDESI each carry a fiber-optic cable that will be precisely pointed at selected objects in the night sky in order to capture their light. A predecessor galaxy-measuring project, called BOSS, required the light-gathering cables to be routinely plugged by hand into metal plates with holes drilled to match the position of pre-selected sky objects. DESI will automate and greatly speed up this process.

    Each 10-inch-long robot has two small motors in it that allow two independent rotating motions to position a fiber anywhere within a circular area 12 millimeters in diameter. In the completed DESI array, these motions will enable the 5,000 robots to cover every point above their metal, elliptical base, which measures about 2.5 feet across.

    That requires precise, software-controlled choreography so that the tightly packed robots don’t literally bump heads as they spin into new positions several times each hour to collect light from different sets of pre-selected sky objects.

    “The main goal of ProtoDESI is to be able to fix fibers on actual objects and hold them there,” said Parker Fagrelius, who is managing the ProtoDESI project at Berkeley Lab. Fagrelius is a UC Berkeley graduate student who is also an affiliate in the Physics Division at Berkeley Lab. ProtoDESI’s robots, assembled at University of Michigan and then shipped to Berkeley Lab, are positioned far enough apart that they won’t accidentally collide during their initial test run.

    While DESI’s robots will primarily target galaxies, ProtoDESI will use mostly bright, familiar stars to tune its robotic positioning system and ensure the system is accurately tracking with the motion of objects in the sky. Mounted next to the positioners is a custom digital camera known as the GFA (for guide, focus and alignment) that will remain targeted on a “guide star”—a bright star that will aid the tracking of other objects targeted by the robot-pointed fibers. Several Spanish research institutions in Barcelona and Madrid are responsible for this GFA system.

    “We’ll choose the fields we look at quite carefully,” Fagrelius said. The robots will initially fix on isolated sky objects so that they don’t mistakenly point at the wrong objects.

    In addition to the 10-robot system, ProtoDESI is equipped with a set of 16 light-emitting rods—shaped similarly to the robots—that project small points of blue light onto a camera to calibrate the positioning system. The completed project will include 120 of these devices, called “illuminated fiducials.”

    The fibers carried by the robots each have a core that is 107 microns (millionths of a meter) wide. After repositioning, the fibers will be backlit to project points of light on a camera that can help to fine-tune their individual positions, if needed. Yale University is supplying this fiber-view camera and also the fiducials.

    8
    A view of the ProtoDESI setup under assembly at Berkeley Lab, with the underside of the robotic fiber-positioners visible at left. (Credit: Paul Mueller/Berkeley Lab)

    Fagrelius will join a team of researchers at Kitt Peak’s 4-meter Mayall telescope in early August to run through a checklist of ProtoDESI tests. About 28 researchers from nine institutions in the DESI collaboration are working on ProtoDESI, including six Berkeley Lab researchers.

    Researchers will test the auto-positioning system by slightly shifting the pointing of the telescope and the fibers—a process known as “dithering”—to see how the components readjust to find the correct targets. A digital camera will measure light streaming in from the fibers to determine if the robots are properly targeting sky objects.

    9
    ProtoDESI will test 10 robots like the one in this diagram. Each one can rotate in two different ways and is designed to point a fiber-optic cable at sky objects to collect their light. (Credit: MNRAS, DOI: 10.1093/mnras/stv541)

    “ProtoDESI will show us how the software and positioners are working together,” Fagrelius said. “All of the things we learn along the way from ProtoDESI will be built back into the plans for DESI’s commissioning.” Some measurements and pre-testing with ProtoDESI will be conducted at Berkeley Lab even before ProtoDESI moves to the Mayall telescope, she added.

    The full robotic array planned for DESI will be segmented in 10 pie-wedge-shaped “petals” that each contains 500 robots. The first petal will be fully assembled by October at Berkeley Lab and tested at the lab through December. The multi-petal design will allow engineers to remove and replace individual petals.

    Each robot will have an electronic circuit board and wiring, and on the final DESI project each robot’s fiber-optic cable will be spliced to a 42-meter-long fiber-optic cable that will run to a light-measuring device known as a spectrograph (ProtoDESI will not have a spectrograph).

    The completed project will feature 10 high-resolution spectrographs, that will measure the properties of objects’ light to tell us about how fast faraway galaxies are moving away from us and their distribution, and will help us trace the universe’s expansion history back 12 billion years.

    9
    A camera test of a type of robotic fiber-optic positioner (left and center) that will be tested in ProtoDESI. (Credit: MNRAS, DOI: 10.1093/mnras/stv541)

    Joe Silber, a Berkeley Lab engineer working on DESI systems that include its robotics, said the fiber-optic cables are among the most sensitive components in DESI. “If there is too tight of a bend or you stress the fiber, it will degrade its performance,” he said, noting that there have already been tests of the repeated bends and twists to the cables caused by the movement of the robots. Over the lifetime of DESI the ends of the fiber-optic cables will be turned almost 200,000 times, he said. Installation of DESI is expected to begin in 2018.

    Fagrelius said she looks forward to the ProtoDESI run at Mayall. “September will have a lot more clear nights than August. There should be four weeks of decent time that we can get on sky,” she said, and other tests can be conducted even when viewing is obscured by weather.

    DESI is supported by the U.S. Department of Energy Office of Science; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under contract to the National Optical Astronomy Observatory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the National Council of Science and Technology of Mexico, and DESI member institutions. The DESI scientists are honored to be permitted to conduct astronomical research on Iolkam Du’ag (Kitt Peak), a mountain with particular significance to the Tohono O’odham Nation.


    This video shows the rotating motions of a robotic fiber-optic positioner. ProtoDESI will test a group of 10 robotic positioners, and DESI will feature 5,000 robots. (Credit: Berkeley Lab)
    Access mp4 video here .


    A simulation of the movements of 499 DESI robots, carefully choreographed to avoid bumping into one another, as seen from above. ProtoDESI is testing 10 robots for the completed DESI project, which will have 5,000 robots. (Credit: Joe Silber/Berkeley Lab)
    Access mp4 video here .

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:15 pm on March 15, 2016 Permalink | Reply
    Tags: , , LBL DESI, ,   

    From Symmetry: “A new pair of lenses for the Mayall” 

    Symmetry Mag

    Symmetry

    03/15/16
    Rashmi Shivni

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    NOAO Mayall 4 m telescope, interior and exterior

    Scientists hope the quarter-ton hunks of glass will help them see dark energy’s effects.

    The delicate process of lens crafting takes time and care. For your typical prescription eyeglasses, expect two weeks for proper sizing and glare-resistant coating. For a four-meter telescope with meter-wide lenses, a similar procedure takes well over a year.

    The Dark Energy Spectroscopic Instrument project is the latest in a line of sky surveys to obtain custom lenses for an existing telescope.

    LBL DESI Dark Energy Spectroscopic Instrument
    LBL DESI Dark Energy Spectroscopic Instrument

    DESI arranged for refurbishments to the Mayall Telescope at the Kitt Peak National Observatory in Arizona, where it will create a three-dimensional map of a third of the sky in a quest to measure dark energy.

    NOAO Kitt Peak
    NOAO Kitt Peak Observatory with the Mayall telescope standing tall

    “DESI’s ultimate goal is to precisely measure and map the expansion rate of the universe and when it started to accelerate in its expansion,” says Michael Levi, the DESI project director and a physicist at the Department of Energy’s Lawrence Berkeley National Laboratory. “We’re looking back in time about 11 billion years, and we can do this with the help of a new corrector and high-precision lenses.”

    The upgrade includes six new lenses, the two heaviest of which are ready for a final coating before integration into the brand new corrector barrel. Those nearly complete lenses, Corrector Lens 1 and Corrector Lens 4 (C1 and C4), have been in production since early 2015. Their journey began as a raw chunk of glass.

    NOAO C4 lens for the Mayall telescope.
    NOAO C4 lens for the Mayall telescope

    Adventures of the looking glass

    Early last year, a private electro-optical lens company in Pittsburgh began fabricating the two lenses. Machines spun the noncrystalline glass around a central axis while removing material, shaping it into its final form. Each lens is over 1 meter in diameter.

    “The lenses must be carefully polished to achieve a surface that’s accurate to tens of nanometers, with errors a fraction of a human hair,” says Tim Miller, an optical engineer for DESI and Berkeley Lab.

    C1 and C4 began production earlier than the other four lenses because they have the tightest specification requirements. This is a consequence of their large size: C1 and C4 weigh in at 444 pounds and 522 pounds, respectively. They’ll eventually work in concert with the two aspherical lenses that correct for defects and a pair of lenses with wedges, which hook to motors and rotate to correct for disturbances on Earth.

    Once the lenses were precisely shaped, they were ready for the cross-country move to the National Optical Astronomy Observatory in Arizona in January.

    C1 and C4 shipped in skid-proof crates with burly security straps for the two-day road trip. The padded crates traveled with monitors called “shock loggers,” which measured bumps and vibrations in the road that could damage the lenses. The loggers previously monitored components for the Dark Energy Camera as they were transported for the Dark Energy Survey.

    Dark Energy SurveyDark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    Dark Energy Survey, the DECam built at FNAL, and the CTIO Victor M Blanco 4 meter telescope which houses the DECAM

    The lenses arrived safely at NOAO, but their journey is far from over. The next big operation is applying antireflective coating, a process scheduled for April. Then they’ll head to University College London, where a team will install them in a new steel corrector barrel being fabricated by Fermilab.

    “The new corrector and lenses won’t help take pictures like the old corrector on Mayall,” says Gaston Gutierrez, the DESI manager of the corrector barrel and cage and a scientist at DOE’s Fermilab. “The lenses will focus on distant galaxies, and the corrector will collect the light in 5000 tiny fibers, which will disperse the light on the spectrograph.”

    By early 2018, the entire package will be ready to ship and install into Mayall.

    Cosmic cartography

    DESI will 3D-map most of the northern sky by collecting redshift data from over 35 million distant galaxies and quasars. A spectrograph shows scientists emission lines, or lines on the color spectrum, with colors linked to wavelengths. Depending on how much the lines have shifted toward the red, scientists can determine how far away a celestial body is from us.

    However, redshifts alone cannot make a perfect three-dimensional map, says Daniel Eisenstein, co-spokesperson for DESI and professor of astronomy at Harvard University. “When we collect the spectra of galaxies in DESI, we are making a 3D map, but it only shows relative distances. It’s as if we have a detailed map of the United States with no scale,” he says.

    DESI scientists use baryon acoustic oscillations, subtle correlations in the way galaxies are spread throughout the cosmos, to infer the scale of the map and our distance from those galaxies. DESI’s precise measurement of that changing distance may reveal how dark energy acts on the universe.

    This spectroscopic survey is the next innovation of telescopic observation. Because of the difficulty of 3D mapping large parts of the sky, high-performance optics with a wide field of view are essential.

    “The DESI field of view will be 8 square degrees, about 40 times the disk of the full moon and nearly 3,000 times larger than the field of view of the Hubble Space Telescope,” Eisenstein says. “Even with this large field of view, it will take DESI about a year of observing time to cover one-third of the sky.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 9:35 pm on February 3, 2016 Permalink | Reply
    Tags: , , LBL DESI, Mosaic-3 camera,   

    From LBL: “New Galaxy-hunting Sky Camera Sees Redder Better” 

    Berkeley Logo

    Berkeley Lab

    February 2, 2016
    Glenn Roberts Jr. 510-486-5582

    A newly upgraded camera that incorporates light sensors developed at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is now one of the best cameras on the planet for studying outer space at red wavelengths that are too red for the human eye to see.

    Very distant astronomical objects appear much redder when observed on Earth due to an effect known as redshift, so this sensitivity to red light enables the camera to detect objects many billions of light years away.

    The camera has begun its two-year mission to quickly survey the sky, amassing images of hundreds of millions of galaxies and stars.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    The 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, AR, USA

    The rebuilt camera, dubbed Mosaic-3, was installed in October on the 4-meter Mayall telescope at Kitt Peak National Observatory near Tucson, Ariz. It will survey the northern sky at infrared wavelengths from 850 nanometers to 1 micron, a range known as the “z-band.”

    Mosaic-3 will capture images nearly twice as fast as its predecessor camera, and can see galaxies 10 times fainter than those detected in a previous survey called the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    Mosaic-3 is the product of a small collaboration of scientists and engineers at Berkeley Lab, Yale University, and the National Optical Astronomy Observatory (NOAO).

    It will help to scout out galaxies that can be targeted for further observations by DESI, the Dark Energy Spectroscopic Instrument, which is scheduled to be installed on the Mayall telescope in 2018.

    DESI Dark Energy Spectroscopic Instrument
    DESI

    DESI, which will be built by a Berkeley Lab-led collaboration, will produce a 3-D map of the universe out to a distance of 12 billion light years. By measuring the velocities of millions of galaxies and extremely bright and distant objects known as quasars, DESI will chronicle the expansion history of the universe to unprecedented precision. It will yield a better understanding of “dark energy,” a mysterious form of energy that is causing this universal expansion to accelerate.

    Mosaic-3’s primary mission is to carry out a survey of roughly one-eighth of the sky (5,500 square degrees). This survey, known as the Mayall z-Band Legacy Survey (MzLS), will span about 220 nights of observations this year and next, and all of the camera’s data will be immediately available to the public. During the remaining nights, Mosaic-3 will be available to astronomers for other research.

    The z-band survey is just one layer in the galaxy survey that is locating targets for DESI. Data from this survey are being combined with data from other telescopes to produce images of galaxies in many colors, and the combined data will be publicly released twice per year on the Legacy Survey website.

    The Mosaic-3 camera is an upgrade that brings new cutting-edge sensors developed at Berkeley Lab to an existing, decade-old camera at the Mayall Telescope. The cryostat (a device used to maintain a supercool temperature) from this camera was refurbished to incorporate the new light sensors, and the electronics were replaced.

    “We rebuilt the whole camera,” said Charles Baltay, a Yale physics professor who oversaw the university’s work on Mosaic-3. “We started in early February and delivered it in August—we had to hustle. At first, people said we couldn’t do it this fast.”

    He added, “Mosaic-3 can measure the same object in half the time compared to its predecessor. It allows us to do the target-selection survey in time—it moves it from impossible to comfortable.”

    The piece of glass used as Mosaic-3’s filter for gathering infrared light appears perfectly black to the naked eye but transmits 98 percent of the incoming infrared light at the wavelengths it is scanning.

    Berkeley Lab supplied the charge-coupled devices (CCDs) that capture light and the readout system that translates the light into images, and Yale was responsible for new mechanical components and software. David Rabinowitz at Yale oversaw the software development, working closely with NOAO astronomers and engineers.

    Mosaic-3 is equipped with four CCDs, each measuring about 6 square inches and containing 16 megapixels. Each pixel in the CCDs is about 100 times larger in area than a pixel in an iPhone 6 camera sensor, and each Mosaic-3 CCD is about 50 times larger in area than the iPhone 6 camera sensor.

    “It’s really the light-gathering power that matters,” said Armin Karcher, a Berkeley Lab design engineer who built a compact, flexible readout system for the camera.

    The large pixel size and overall CCD size are key in gathering light, and the 0.5-millimeter thickness of the CCDs helps the CCDs see deeper into the infrared wavelengths.

    Steve Holland, an engineer at Berkeley Lab who invented these red-sensitive CCDs, said he was already engaged in the design of similar CCDs for the DESI project when Mosaic-3 launched. “It was serendipitous,” he said.

    Christopher Bebek, who manages Berkeley Lab’s CCD group and served as the lab’s liaison on the Mosaic-3 project, added, “This was like a dress rehearsal for detectors and electronics for DESI.” An updated CCD design is now in production for DESI, which will require 20 of these CCDs for its spectrograph system.

    The Mosaic-3 instrument upgrade was funded by the U.S. Department of Energy Office of Science through the DESI project, and by NOAO. The DESI project is managed by the Lawrence Berkeley National Laboratory.

    For more information about DESI, go here.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 4:56 pm on September 21, 2015 Permalink | Reply
    Tags: , , LBL DESI   

    From LBL: “DESI, an Ambitious Probe of Dark Energy, Achieves its Next Major Milestone” 

    Berkeley Logo

    Berkeley Lab

    September 21, 2015
    Paul Preuss 415-272-3253

    DOE approves Critical Decision 2 for DESI, based at Berkeley Lab

    LBL DESI Dark Energy Spectroscopic Instrument
    DESI at LBL

    DESI, the Dark Energy Spectroscopic Instrument, is an exceptional apparatus designed to improve our understanding of the role of dark energy in the expansion history of the universe; it will do this by measuring the redshifts of more than 30 million galaxies and quasars, with unprecedented precision. The U.S. Department of Energy has announced its approval of Critical Decision 2 (CD–2), authorizing the project’s scientific scope, schedule, and funding profile.

    Two hundred physicists and astronomers make up the international DESI Collaboration, which is based at DOE’s Lawrence Berkeley National Laboratory (Berkeley Lab). Using DESI’s redshift data they will create a three-dimensional map of the universe reaching deeper in space and time than any yet made. The map will reveal how dark energy and gravity have competed over time to shape the structure of the universe—both the regular clustering of galaxies and dark matter on the largest scales, and the idiosyncratic motion of individual galaxies.

    DESI Director Michael Levi, of Berkeley Lab’s Physics Division, says, “We’ll study four kinds of targets to gather a continuous range of redshifts: nearby bright galaxies to redshift 0.4; luminous red galaxies to redshift 1; emission line galaxies to redshift 1.6; and very distant quasars all the way to redshift 3.5.”

    Redshift, literally the shift of a distant astronomical object’s spectrum to longer (redder) wavelengths, is a direct measure of how much space stretched while the light was en route from object to observer. The bigger the redshift, the older the object. To capture light whose journey started up to 12 billion years ago—corresponding to a redshift of 3.5, when the universe was less than one seventh its present age—the DESI instrument will be mounted on the 4–meter Mayall telescope at Kitt Peak National Observatory near Tucson, Arizona.

    DESI’s deep-space science

    Daniel Eisenstein, of Harvard University, and Risa Wechsler, of Stanford University and DOE’s SLAC National Accelerator Laboratory, are the DESI Collaboration’s Spokespersons. Eisenstein says, “DESI aims to use the fossil imprint of sound waves from the first 400,000 years of the universe”—still detectable as a pattern of temperature variations in the cosmic microwave background radiation (CMB)—“to study the mysterious composition of today’s universe.”

    Those temperature differences map early variations in density (sound waves) that subsequently evolved into the clustering of galaxies, intergalactic gas, and dark matter at recurrent intervals throughout space. Called baryon acoustic oscillations (BAO), these regularly spaced clusterings are consistent over time—like a ruler to gauge the universe, with the CMB at one end—allowing direct measures of dark energy’s effect on expansion.

    Wechsler says BAO is the beginning of what DESI can do. “Because large accumulations of mass have gravitational effects on individual galaxies, known as redshift space distortions, DESI can also test the accuracy of General Relativity, Einstein’s theory of gravity.”

    In related investigations, DESI will “weigh” the total mass of neutrinos in the universe, with a good chance of learning which of the three known kinds of neutrinos is the heaviest. DESI will also compare models of the inflationary epoch, when the universe expanded exponentially within a sliver of a second after the big bang, leaving it extraordinarily uniform in composition.

    Charting the universe in 3D

    DESI’s technology is as intriguing as its science. The National Science Foundation’s (NSF’s) 4-meter Mayall telescope, operated by the National Optical Astronomy Observatory (NOAO), was completed in the early 1970s and recently recommended for divestment. NSF then made it possible for DOE to mount the DESI spectrometer on the telescope.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    4-meter Mayall telescope at Kitt Peak

    “The Mayall telescope is built like a battleship,” says Natalie Roe, Director of Berkeley Lab’s Physics Division and a member the DESI Executive Committee. The telescope’s moving weight is 375 tons, and it is “so well engineered it can support this very heavy new instrument”—which weighs five tons—“suspended way up there in the air.”

    The DESI spectrometer will upgrade this old battleship to world-leading capability. The telescope’s top end will be replaced with DESI’s optical corrector and focal-plane system. The corrector’s six glass lenses, each a meter across, will focus the light from the existing 4-meter mirror onto the new focal plane. The lenses were funded by the Gordon and Betty Moore Foundation and the Heising-Simons Foundation.

    2
    A few of the 5,000 close-packed robotic positioners that place the ends of optical fibers to collect the light from a single galaxy or quasar. The blue circle represents a patch of sky with numerous astronomical targets reachable by a single robot. In seconds it can rotate, extend, or retract to place its fiber in position with millionths of a meter precision. (Image R. Lafever, DESI Collaboration)

    The focal plane, eight-tenths of a meter in diameter, will consist of 5,000 tiny robot arms, each holding an optical fiber. The closely packed robots position the fiber ends to capture the spectrum of a single galaxy or quasar. After a 15 to 20-minute exposure, the telescope aims at a new patch of sky; in less than a minute the robots rotate and reposition thousands of fibers.

    “What’s impressed me most over the years since DESI was first proposed is that the technical capability of the instrument is even better than we hoped,” says Berkeley Lab’s David Schlegel. Schlegel and Brenna Flaugher, of the Fermi National Accelerator Laboratory, are DESI’s Project Scientists. “For example, the final design of the robot positioners has very few moving parts—about 25 parts overall, with only two critical connections.”

    Says Flaugher, “Next year we’ll install a small version we call ProtoDESI, with 10 fiber positioners, on the Mayall telescope. It will let us test our ability to aim the fibers at galaxy targets, to keep the targets in focus and on the fibers as the telescope tracks the sky.”

    The DESI redshift survey will richly complement other aspects of DOE’s interest in dark energy, including partnerships with NSF in such imaging surveys as the ongoing Dark Energy Survey, which uses the Dark Energy Camera on the Blanco telescope in Chile (the Mayall telescope’s South American twin), and the Large Synoptic Survey Telescope under construction in Chile [being built under the direction of SLAC] , whose run is scheduled to start in 2021. DESI traces its heritage to the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey [SDSS], but in number of galaxies and volume of space surveyed, DESI will be more than 10 times bigger than BOSS.

    Dark Energy Survey
    Fermilab DECam
    DECam built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter telescope in CHile whihc houses the DECam

    LSST Camera
    LSST Camera
    LSST Interior
    LSST Interior
    LSST Exterior
    Proposed telescope to house the LSST in Chile

    LBL BOSS
    SDSS telescope

    Key to DESI’s present and future success is its robust scientific collaboration, supported by many organizations, among them 31 universities and 18 government and private institutions, both U.S. and foreign, including five DOE national labs. DOE and NSF will shortly begin joint support for Mayall telescope operations, preparatory work, and installation of the DESI instrument. Beginning in fiscal year 2019, DOE will support the full operations of the telescope throughout the five-year DESI survey.

    The DESI Project is funded by the U.S. Department of Energy, Office of Science; additional support has been provided by the U.S. National Science Foundation, the Gordon and Betty Moore Foundation, the Heising-Simons Foundation, the Science and Technologies Facilities Council of the United Kingdom, the Consejo Nacional de Ciencia y Tecnología, Mexico, the Chinese Academy of Sciences, and the DESI Membership from: Aix-Marseille University; Argonne National Laboratory; Barcelona-Madrid Regional Participation Group; Brookhaven National Laboratory; Boston University; Carnegie Mellon University; CEA-IRFU, Saclay; China Participation Group; Cornell University; Durham University; École Polytechnique Fédérale de Lausanne; Eidgenössische Technische Hochschule, Zürich; Fermi National Accelerator Laboratory; Granada-Madrid-Tenerife Regional Participation Group; Harvard University; Korea Astronomy and Space Science Institute; Korea Institute for Advanced Study; Institute of Cosmological Sciences, University of Barcelona; Lawrence Berkeley National Laboratory; Laboratoire de Physique Nucléaire et de Hautes Energies; Mexico Regional Participation Group; National Optical Astronomy Observatory; Siena College; SLAC National Accelerator Laboratory; Southern Methodist University; Swinburne University; The Ohio State University; Universidad de los Andes; University of Arizona; University of California, Berkeley; University of California, Irvine; University of California, Santa Cruz; University College London; University of Michigan at Ann Arbor; University of Pennsylvania; University of Pittsburgh; University of Portsmouth; University of Queensland; University of Toronto; University of Utah; UK Regional Participation Group; Yale University. For more information, visit desi.lbl.gov.

    The National Optical Astronomy Observatory (NOAO) is the national center for ground-based nighttime astronomy in the United States (http://www.noao.edu) and is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation Division of Astronomical Sciences.

    Established in 2007 by Mark Heising and Elizabeth Simons, the Heising-Simons Foundation (www.heisingsimons.org) is dedicated to advancing sustainable solutions in the environment, supporting groundbreaking research in science, and enhancing the education of children.

    The Gordon and Betty Moore Foundation, established in 2000, seeks to advance environmental conservation, patient care and scientific research. The Foundation’s Science Program aims to make a significant impact on the development of provocative, transformative scientific research, and increase knowledge in emerging fields. For more information, visit http://www.moore.org.

    The Science and Technology Facilities Council (STFC) of the United Kingdom coordinates research on some of the most significant challenges facing society, such as future energy needs, monitoring and understanding climate change, and global security. It offers grants and support in particle physics, astronomy and nuclear physics, visit http://www.stfc.ac.uk.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
  • richardmitnick 1:45 pm on June 25, 2015 Permalink | Reply
    Tags: , , , LBL DESI   

    From Symmetry: “Exploring dark energy with robots” 

    Symmetry

    June 25, 2015
    Glenn Roberts Jr.

    The Dark Energy Spectroscopic Instrument will produce a 3-D space map using a ‘hive’ of robots.

    1
    Courtesy of NOAO

    Five thousand pencil-shaped robots, densely nested in a metal hive, whir to life with a precise, dizzying choreography. Small U-shaped heads swivel into a new arrangement in a matter of seconds.

    This preprogrammed routine will play out about four times per hour every night at the Dark Energy Spectroscopic Instrument. The robots of DESI will be used to produce a 3-D map of one-third of the sky. This will help DESI fulfill its primary mission of investigating dark energy, a mysterious force thought to be causing the acceleration of the expansion of the universe.

    DESI Dark Energy Spectroscopic Instrument
    DESI

    The tiny robots will be arranged in 10 wedge-shaped metal “petals” that together form a cylinder about 2.6 feet across. They will maneuver the ends of fiber-optic cables to point at sets of galaxies and other bright objects in the universe. DESI will determine their distance from Earth based on the light they emit.

    DESI’s robots are in development at Lawrence Berkeley National Laboratory, the lead in the DESI collaboration, and at the University of Michigan.

    2
    Courtesy of: DESI collaboration

    The robots—each about 8 millimeters wide in their main section and 8 inches long—will be custom-built around commercially available motors measuring just 4 millimeters in diameter. This type of precision motor, at this size, became commercially available in 2013 and is now manufactured by three companies. The motors have found use in medical devices such as insulin pumps, surgical robots and diagnostic tools.

    At DESI, the robots will automate what was formerly a painstaking manual process used at previous experiments. At the Baryon Oscillation Spectroscopic Survey, or BOSS, which began in 2009, technicians must plug 1000 fibers by hand several times each day into drilled metal plates, like operators plugging cables into old-fashioned telephone switchboards.

    “DESI is exciting because all of that work will be done robotically,” says Risa Wechsler, a co-spokesperson for DESI and an associate professor of the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of Stanford University and SLAC National Accelerator Laboratory. Using the robots, DESI will be able to redirect all of its 5000 fibers in an elaborate dance in less than 30 seconds (see video).

    “DESI definitely represents a new era,” Wechsler says.

    In addition to precisely measuring the color of light emitted by space objects, DESI will also measure how the clustering of galaxies and quasars, which are very distant and bright objects, has evolved over time. It will calculate the distance for up to 25 million space objects, compared to the fewer than 2 million objects examined by BOSS.

    The robots are designed to both collect and transmit light. After each repositioning of fibers, a special camera measures the alignment of each robot’s fiber-optic cable within thousandths of a millimeter. If the robots are misaligned, they are automatically individually repositioned to correct the error.

    Each robot has its own electronics board and can shut off and turn on independently, says Joe Silber, an engineer at Berkeley Lab who manages the system that includes the robotic array.

    In seven successive generations of prototype designs, Silber has worked to streamline and simplify the robots, trimming down their design from 60 parts to just 18. “It took a long time to really understand how to make these things as cheap and simple as possible,” he says. “We were trying not to get too clever with them.”

    The plan is for DESI to begin a 5-year run at Kitt Peak National Observatory near Tucson, Arizona, in 2019. Berkeley and Michigan scientists plan to build a test batch of 500 robots early next year, and to build the rest in 2017 and 2018.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 8:09 am on May 20, 2015 Permalink | Reply
    Tags: , , LBL DESI   

    From LBL: “How a New Telescope Will Measure the Expansion of the Universe” 

    Berkeley Logo

    Berkeley Lab

    May 01, 2015
    No Writer Credit

    1
    Two-dimensional map of the sky that will identify the galaxies that will be the targets for our spectroscopic measurements once DESI is built.Image credit: http://legacysurvey.org/viewer

    For the past several years, scientists at the U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab) have been planning the construction of and developing technologies for a very special instrument that will create the most extensive three-dimensional map of the universe to date. Called DESI for Dark Energy Spectroscopic Instrument, this project will trace the growth history of the universe rather like the way you might track your child’s height with pencil marks climbing up a doorframe.

    But DESI will start from the present and work back into the past.

    DESI will make a full 3D map pinpointing galaxies’ locations across the universe. The map, unprecedented in its size and scope, will allow scientists to test theories of dark energy, the mysterious force that appears to cause the accelerating expansion and stretching of the universe first discovered in observations of supernovae by groups led by Saul Perlmutter at Berkeley Lab and by Brian Schmidt, now at Australian National University, and Adam Riess, now at Johns Hopkins University.

    Michael Levi and David Schlegel, physicists at Berkeley Lab, have been key players in DESI from the beginning. The LBNL news office sat down to discuss the future of the project and how this forthcoming map will help scientists better understand dark energy.

    What does it mean to make a 3D map of the universe and how big will it be?

    Michael Levi: To start, DESI will use 2D imaging surveys to pick tens of millions of galaxies to study. Then the DESI instrument will give us redshifts of about 25 million galaxies. The redshifts are what gives you the depth information.

    David Schlegel: The size of this survey will be huge. In the first five years of operation, we will have measured the distance to more galaxies than previously measured by all other telescopes in the world combined.

    2
    Exterior of Kitt Peak Observatory in Tucson, Arizona.Image credit: NOAO/AURA/NSF

    How does the redshift give you the depth information?

    ML: We’re collecting spectra, or wavelengths of light, from galaxies. From the spectra, we get a galaxy’s redshift, the ratio of the wavelength we see, to the wavelength the light had when it left the galaxy. The light will stretch exactly the way the universe stretches. For some galaxies, we look for light that starts with a wavelength of 373 nanometers. If we then see it at 746 nanometers, we know the universe stretched by a factor of 2 while the light was making its way to us.

    What kind of telescope collects this kind of spectra?

    DS: We’re actually retrofitting a 4-meter telescope at Kitt Peak in Arizona called the Mayall telescope. We’re adding enormous lenses that give a huge field of view. A set of 5000 optical fibers, each like the ones used for long-distance Internet connections, are used to pick off light from up to 5000 galaxies at a time.

    The fibers direct light to the 30 cameras and spectrographs we have connected to the whole rig. We’ll observe these galaxies for about 20 minutes, then we will point the telescope in a new direction and 5000 little robots will rearrange these fibers to look at a new collection of up to 5000 galaxies, one fiber per galaxy. In other words, the positions of the optical fibers mimic the positions of the galaxies so that each fiber collects light from one galaxy. Point the telescope in a different direction and the fibers need to take on a new configuration.

    ML: The telescope was built like a battleship in the 1970s, and one of the advantages of this venerable telescope is that it can support the weight of these instruments, which weigh as much as a school bus. This heavy equipment would overwhelm a modern telescope.

    2
    Mayall Telescope at Kitt Peak.Image credit: NOAO/AURA/NSF

    How much of the sky will DESI be able to see?

    ML: You can’t see through the Milky Way—its dust cuts out about a third of the sky. So it works out that from one spot on earth, you can see about one third of the sky.

    DS: If we had another telescope in the southern hemisphere, we could get another third of the sky. But as it is, we’re expecting DESI to see 20 to 30 million galaxies, looking out over a distance of about 10 billion light years. The universe is 13.7 billion years old, and so at a distance of 10 billion light years, we’re looking back in time some 70 percent of the age of the universe. The map from DESI will be both much larger than any previous map and extend much further into the past.

    Aside from virtual tours of our universe, what scientific purpose does a map like this have? How do we use it to understand dark energy?

    ML: What we know is that dark energy, which was discovered in 1998, seems to be responsible for the present accelerating expansion of the universe. But we still don’t know what it is, and we also haven’t made very good measurements of it.

    A project called BOSS started to scratch the surface of this question using spectroscopic techniques similar to DESI’s.

    LBL BOSS
    LBL BOSS

    Other imaging surveys like the Dark Energy Survey and the Large Synoptic Survey Telescope measure dark energy in a different way, by observing how matter that lies between observed galaxies and us distorts that light. All of these projects are working together to better understand what dark energy actually is.

    Dark Energy Camera
    DECam, built at FNAL and housed in the Victor M Blanco Telescope
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Victor M. Blanco Telescope

    LSST Camera
    LSST Interior
    LSST Exterior
    LSST Camera and telescope

    Once we have our very large and very precise map from DESI, we can measure the distances between pairs of galaxies. These distances enable us to track the expansion of the universe.

    More than that, the 3D clustering of the galaxies lets us calculate the gravitational field between them, testing how cosmic structure grew over time. It can even check whether Einstein’s theory of gravity works in both the early and late universe.

    Has the universe always been expanding like it is today?

    DS: In the early universe, dark energy didn’t dominate like it does now and we believe that the expansion was slowing down then. But we only have one data point from that time. All the other data we have is when the universe’s expansion was speeding up, thanks to dark energy.

    ML: Maybe the expansion speed comes and goes, but our data are not sufficient to tell us.

    Where does DESI come in?

    DS: DESI helps us understand the accelerating universe through the structure of this 3D map because the features on this map—the positions and clusters of galaxies—could vary significantly as we look deeper into the universe.

    For instance, the map close to us is stretched out a lot more than it should be because of this acceleration due to dark energy. And then in the early universe, when there’s not as much dark energy, it shouldn’t be as stretched out, but this is where we don’t have much data yet. Depending on when dark energy was pushing the universe apart, it will push apart different parts of the map. This data will help us eliminate a number of theories about the way dark energy works.

    What’s Berkeley Lab’s role in all this?

    DS: We’re running the construction project. We’ve also raised the money for the large corrector optics, which are in the process of being made. We’re designing and manufacturing two-thirds of the CCD cameras used in the spectrographs. And we’re designing and building miniaturized electronics and actuators for the robotic elements that automate the positions of the fiber optics. Also, our supercomputing center, NERSC, is handling the hundreds of terabytes of data DESI will produce.

    How many researchers and institutions are involved in DESI and who’s funding it?

    ML: The U.S. Department of Energy is expected to provide the majority of the project construction funds with additional contributions from the UK, France, Switzerland, and Spain. We have 180 collaborators from 25 institutions. DESI’s very fortunate to have donations from the Heising-Simons Foundation and the Gordon and Betty Moore Foundation, and support from the Science and Technology Facilities Council in the UK. We’re also supported by the National Optical Astronomy Observatory.

    What are your next steps?

    DS: We’re releasing the first data from the initial 2D map of the sky that will identify the galaxies that will be the targets for our spectroscopic measurements once DESI is built. This preliminary survey contains a huge amount of data, and we’re still just getting warmed up.

    In March, we passed a “CD-1 review,” an early stage “critical decision” process by the DOE’s Office of Project Assessment that tracks the progress on projects. We’ll start installation at Kitt Peak in 2017, and we’re aiming for first light by the end of 2018.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    A U.S. Department of Energy National Laboratory Operated by the University of California

    University of California Seal

    DOE Seal

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: