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Full list of authors: Silber, Joseph Harry; Fagrelius, Parker; Fanning, Kevin; Schubnell, Michael; Aguilar, Jessica Nicole; Ahlen, Steven; Ameel, Jon; Ballester, Otger; Baltay, Charles; Bebek, Chris; Beard, Dominic Benton; Besuner, Robert; Cardiel-Sas, Laia; Casas, Ricard; Castander, Francisco Javier; Claybaugh, Todd; Dobson, Carl; Duan, Yutong; Dunlop, Patrick; Edelstein, Jerry; Emmet, William T.; Elliott, Ann; Evatt, Matthew; Gershkovich, Irena; Guy, Julien; Harris, Stu; Heetderks, Henry; Heetderks, Ian; Honscheid, Klaus; Maria Illa, Jose; Jelinsky, Patrick; Jelinsky, Sharon R.; Jimenez, Jorge; Karcher, Armin; Kent, Stephen; Kirkby, David; Kneib, Jean-Paul; Lambert, Andrew; Lampton, Mike; Leitner, Daniela; Levi, Michael; McCauley, Jeremy; Meisner, Aaron; Miller, Timothy N.; Miquel, Ramon; Mundet, Julia; Poppett, Claire; Rabinowitz, David; Reil, Kevin; Roman, David; Schlegel, David; Serrano, Santiago; Van Shourt, William; Sprayberry, David; Tarle, Gregory; Tie, Suk Sien; Weaverdyck, Curtis; Zhang, Kai; Azzaro, Marco; Bailey, Stephen; Becerril, Santiago; Blackwell, Tami; Bouri, Mohamed; Brooks, David; Buckley-Geer, Elizabeth; Penate Castro, Jose; Derwent, Mark; Dey, Arjun; Dhungana, Govinda; Doel, Peter; Eisenstein, Daniel J.; Fahim, Nasib; Garcia-Bellido, Juan; Gaztanaga, Enrique; Gontcho, Satya Gontcho A.; Gutierrez, Gaston; Horler, Philipp; Kehoe, Robert; Kisner, Theodore; Kremin, Anthony; Kronig, Luzius; Landriau, Martin; Le Guillou, Laurent; Martini, Paul; Moustakas, John; Palanque-Delabrouille, Nathalie; Peng, Xiyan; Percival, Will; Prada, Francisco; Allende Prieto, Carlos; Gonzalez de Rivera, Guillermo; Sanchez, Eusebio; Sanchez, Justo; Sharples, Ray; Soares-Santos, Marcelle; Schlafly, Edward; Weaver, Benjamin Alan; Zhou, Zhimin; Zhu, Yaling; Zou, Hu; DESI Collaboration.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10–20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. Over the next 5 yr, they will enable the newly constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5020 robotic positioners and optical fibers, DESI's Focal Plane System includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs. © 2022. The Author(s). Published by the American Astronomical Society., The authors in the Barcelona-Madrid Regional Participation Group (BCN-MAD RPG) wish to acknowledge support by MICIN under grants PID2019-111317 GB, PGC2018-094773, PGC2018-102021, SEV-2016-0588, SEV-2016-0597, MDM-2015-0509, and CEX2020-001058-M, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. M.A., S.B., N.F., F.P., G.G.R., and J.S. acknowledge support from the Spanish MICINN grants MultiDark CSD2009-00064, IFT-UAM/CSIC Severo Ochoa Award SEV-2012-0249 and AYA2014-60641-C2-1-P, CSIC-AVS contract through MICINN grant AYA2010-21231-C02-01 and CDTI grant IDC-20101033, and support from the Campus of International Excellence UAM+CSIC. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institutions., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

The Dark Energy Spectroscopic Instrument (DESI) is under construction to determine the expansion history of the Universe using the Baryon Acoustic Oscillation technique. Over the life of the experiment DESI will measure the spectra of 35 million galaxies and quasars over 14,000 square degrees out to a redshift of 3.5. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5,000 robotic fiber positioners located at the prime focus. The fibers in turn will feed ten broad-band spectrographs covering the wavelength range from 360nm to 980 nm. Rapid and accurate targeting of the fibers is provided by precision theta-phi robotic fiber positioners. The fiber positioners are manufactured at the University of Michigan. Following assembly each positioner passes through a burn-in and verification sequence. We describe the testing of the positioners and discuss the performance achieved.

International audience; We describe here a novel design of a fast high-density robotized fiber positioner system for massive spectroscopic surveys. The fiber positioners are compact, robust, and they can be coordinated, allowing for a high spatial density. Furthermore, the high absolute accuracy removes the need for a metrology system and reduces the reconfiguration time. First, we present the requirements for such a high-density fiber positioner system and put them in relation with the science goals. Then, we discuss the positioner design that accomplishes these requirements (including mechanical design, local control electronics board, overall communication solution, and observation sequencing). Finally, the performance of the proposed design is measured using 25 mm pitch prototypes of the positioners, through a dedicated novel designed test-bench. The related results show that our prototypes fulfil the requirements particularly in terms of positioning precision (

One of the big research topics in modern cosmology is the mystery of dark Energy. To unveil the secret, cosmologists want to measure precisely the evolution of large scale structures in the universe. One way of doing so is to measure the 3D location of a high number of galaxies. By measuring the redshift of a galaxy, it is possible to find its distance. In order to measure a high number of galaxies in a practical amount of time, we need to observe multiple objects in parallel. Instead of a spectrograph, thousands of optical fibres are placed in the focal plane of a telescope. They will transmit the light of many objects to a spectrograph. Each fibre has to be positioned to several μm precision in the focal plane of a telescope for each exposure. Each fibre is positioned by a 2-axis fibre positioner. In this paper such a fibre positioner with 24-mm diameter is presented. It is driven by two brushless DC motors in combination with a backlash free gearbox. The positioner has an optimal central fibre path and improved angular alignment. The fibre runs through the centre of the positioner and is only bent at the top to reach its target position. In this way, the flexion and torsion of the fibre are minimal. In addition to the high positioning accuracy, the design is optimized to allow a minimal tilt error of the fibre. This is demonstrated using a novel optical tilt measurement system.

Every year, several ten thousand patients die on mechanical ventilation. This happens because the lungs can currently not be monitored adequately in real-time, and thus sub optimal ventilator settings can cause severe lung tissue damage. Electrical Impedance Tomography (EIT) produces a real-time image sequence of the breathing lungs. So far, no automatic method has been available to detect the physiological regional lung states. We propose an algorithm that clusters the raw pixel based data of the EIT image sequence into clinically relevant regions with similar physiological behavior. Our implementation is very robust regarding bad signal quality due to low signal to noise ratio (SNR). It is also highly efficient in terms of computational complexity by considering additional physiological knowledge. The functionality of the algorithm has been verified using EIT data of a human subject with acute lung failure at various Positive End-Expiratory Pressure (PEEP) levels. The results are in agreement with the study protocol. This method brings EIT treatment one step closer towards protective ventilation therapy.

The next generation of large-scale spectroscopic survey experiments such as DESI, will use thousands of fiber positioner robots packed on a focal plate. In order to maximize the observing time with this robotic system we need to move in parallel the fiber-ends of all positioners from the previous to the next target coordinates. Direct trajectories are not feasible due to collision risks that could undeniably damage the robots and impact the survey operation and performance. We have previously developed a motion planning method based on a novel decentralized navigation function for collision-free coordination of fiber positioners. The navigation function takes into account the configuration of positioners as well as their envelope constraints. The motion planning scheme has linear complexity and short motion duration (~2.5 seconds with the maximum speed of 30 rpm for the positioner), which is independent of the number of positioners. These two key advantages of the decentralization designate the method as a promising solution for the collision-free motion-planning problem in the next-generation of fiber-fed spectrographs. In a framework where a centralized computer communicates with the positioner robots, communication overhead can be reduced significantly by using velocity profiles consisting of a few bits only. We present here the discretization of velocity profiles to ensure the feasibility of a real-time coordination for a large number of positioners. The modified motion planning method that generates piecewise linearized position profiles guarantees collision-free trajectories for all the robots. The velocity profiles fit few bits at the expense of higher computational costs., Comment: SPIE Astronomical Telescopes + Instrumentation 2014 in Montr\'eal, Quebec, Canada. arXiv admin note: substantial text overlap with arXiv:1312.1644

In the large-scale, Dark Energy Spectroscopic Instrument (DESI), thousands of fiber positioners will be used. Those are robotic positioners, with two axis, and having the size of a pen. They are tightly packed on the focal plane of the telescope. Dedicated micro-robots have been developed and they use 4mm brushless DC motors. To simplify the implementation and reduce the space occupancy, each actuator will integrate its own electronic control board. This board will be used to communicate with the central trajectory generator, manage low level control tasks and motor current feeding. In this context, we present a solution for a highly compact electronic. This electronic is composed of two layers. The first is the power stage that can drive simultaneously two brushless motors. The second one consists of a fast microcontroller and deals with different control tasks: communication, acquisition of the hall sensor signals, commutation of the motors phases, and performing position and current regulation. A set of diagnostic functions are also implemented to detect failure in the motors or the sensors, and to sense abnormal load change that may be the result of two robots colliding., Comment: 7 pages, 10 figures, SPIE Digital Library