The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. The robotic Focal Plane System (FPS) carries 500 robotic fiber positioners, 60 stationary Fiber-Illuminated Fiducials (FIFs), and 6 Guide, Focus, and Acquisition cameras (GFAs). The GFAs find and use guide stars to compute target positions for the robots. The FIFs provide a reference basis against which precise measurements of the robot positions can be made using the Fiber Viewing Camera (FVC). Once imaged by the FVC, closed loop control allows the robots to reach their commanded positions to within 12 microns of precision. This paper discusses the metrology process for the FIFs and GFAs, thus allowing for accurate robot moves and reliable FVC measurements.
We describe the on-sky performance of the robotic Focal Plane System (FPS) units that replace the fiber plug-plate systems at the Sloan and duPont telescopes for the SDSS-V survey. The first FPS was arrived at Apache Point in December 2021, and the second unit will be delivered to Las Campanas in spring 2022. Each FPS carries 500 zonal fiber positioners carrying three fibers: two science fibers for the BOSS and APOGEE spectrographs and a back-illuminated metrology fiber. The FPS enables the SDSS-V Milky Way and Black Hole Mapper surveys that will begin survey operations in 2022.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of ≥ 6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe.1 The robotic Focal Plane System (FPS)2 will carry 500 robots each with three fibers for science and metrology. The science fibers feed the BOSS3 and APOGEE4 spectrographs, while the metrology fibers are back illuminated to aid in robot positioning. Blind initial x/y positional precision of the robots is expected to be better than 50µm. The robots must position the fibers to better than 5µm in order to meet the science requirements. The FPS fiber viewing camera (FVC) consists of optomechanical components that look back through the telescope optics at light from back-lit fiducial and metrology fibers to measure the positions of the robots in the telescope focal plane. The FVC takes an image of the robots in the telescope focal plane, measures their positions to an accuracy of better than 3µm, and then feeds back error commands to the robot control system to meet the 5µm positional requirement. This paper details the optomechanical design, and initial results of an engineering run on the du Pont telescope.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. This paper describes the design and construction of two robotic Focal Plane System (FPS) units that will replace the traditional SDSS fiber plug-plate systems at the Sloan and du Pont telescopes for SDSS-V. Each FPS deploys 500 zonal fiber positioners that allow us to reconfigure the fibers onto a new target field within 2-3 minutes of acquisition. Each positioner carries three fibers: two science fibers that feed the BOSS and APOGEE spectrographs and a third back-illuminated metrology fiber is used in conjunction with a telescopemounted Fiber Viewing Camera (FVC) to measure the absolute positions of the fiber heads. The 300 APOGEE fibers are distributed among the 500 positioners to maximize common field coverage. A set of fiber-illuminated fiducials distributed in and around the positioner array establish a fixed reference frame for the FVC system. Finally, six CCD cameras mounted around the periphery of the focal plane provide acquisition, guiding, and focus monitoring functions. The FPS is a key enabling technology of the SDSS-V Milky Way and Black Hole Mapper surveys.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of > 6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe.1 This paper describes the design of the theta/phi fiber positioner robots that are being produced to be integrated in the Focal Plane System (FPS) of the SDSS-V telescopes. For each installation, 500 robots are being manufactured, more than 800 units have already been received from the manufacturer and validated. Mechanical, electronic and firmware designs are presented in the current paper in detail. We will expose the different iterations of the prototypes that were developed, built and tested and ultimately allowed to achieve the end version that meets the requested science requirements. The fiber positioner robot is carrying 3 optical fibers integrated into a single snowflake ferrule. Two of the fibers are science fibers connected to two different spectrographs, and the third fiber is used for metrology. The robot is capable of positioning the fibers with a planar accuracy better than 50 microns with a first blind move within its workspace of a diameter of 44.8mm. With a complementary fiber viewing camera (FVC) and the backlighted metrology fiber to perform a few small corrections moves, the positioner can reach a sub 5-micron precision on the fiber position.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of < 6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. Collaboratively, organizations across both academia and industry have partnered to overcome technical challenges and execute operational directives associated with commissioning the various mechanical, electrical, and software subsystems of SDSS-V. While this type of collaboration is not unique, the scale and complexity of next generation astronomical instruments is an emerging challenge that requires industrial systems and process engineering practices at a quasi-industrial scale. Driven by the success of multiplexed spectroscopic surveys, instrumentation is evolving to include systems with hundreds to thousands of components and sub-assemblies procured or produced from various sources. This trend requires the adoption of new and existing processes and best practices in the design, integration, and test of next generation astronomical instruments. The following discussion outlines those industrial systems and process engineering processes, methods, and practices, currently in the operational phase, for the design, integration, and test of the SDSS-V Focal Plane System (FPS). An emphasis is placed on processes, methods, and practices related to coordination of multiple contract manufacturing vendors and operational execution of small batch manufacturing.
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