The instrumentation of the Prime Focus Spectrograph (PFS), a next generation facility instrument on the Subaru telescope, is now in the final phase of its commissioning process and its general, open-use operations for sciences will provisionally start in 2025. The instrument enables simultaneous spectroscopy with 2386 individual fibers distributed over a very wide (∼1.3 degrees in diameter) field of view on the Subaru’s prime focus. The spectra cover a wide range of wavelengths from 380nm to 1260nm in one exposure in the Low-Resolution (LR) mode (while the visible red channel has the Medium-Resolution (MR) mode as well that covers 710−885nm). The system integration activities at the observatory on Maunakea in Hawaii have been continuing since the arrival of the Metrology Camera System in 2018. On-sky engineering tests and observations have also been carried out continually since September 2021 and, despite various difficulties in interlacing commissioning processes with development activities on the schedule and addressing some major issues on hardware and software, the team successfully observed many targeted stars as intended over the entire field of view (Engineering First Light) in September 2022. Then in parallel to the arrival, integration and commissioning of more hardware components, validations and optimizations of the performance and operation of the instrument are ongoing. The accuracy of the fiber positioning process and the speed of the fiber reconfiguration process have been recently confirmed to be ∼ 20−30μm for 95% of allocated fibers, and ∼130 seconds, respectively. While precise quantitative analyses are still in progress, the measured throughput has been confirmed to be consistent with the model where the information from various sub-components and sub-assemblies is integrated. Long integration of relatively faint objects are being taken to validate an expected increase of signal-to-noise ratio as more exposures are taken and co-added without any serious systematic errors from, e.g., sky subtraction process. The PFS science operation will be carried out in a queue mode by default and various developments, implementations and validations have been underway accordingly in parallel to the instrument commissioning activities. Meetings and sessions are arranged continually with the communities of potential PFS users on multiple scales, and discussions are iterated for mutual understanding and possible optimization of the rules and procedures over a wide range of processes such as proposal submission, observation planning, data acquisition and data delivery. The end-to-end processes of queue observations including successive exposures with updated plans based on assessed qualities of the data from past observations are being tested during engineering observations, and further optimizations are being undertaken. In this contribution, a top-level summary of these achievements and ongoing progresses and future perspectives will be provided.
In this paper, we present the beginning of the last phase of the integration process of the FOCCoS subsystem, "Fiber Optical Cable and Connector System", to be installed on the Subaru telescope as part of the PFS (Prime Focus Spectrograph) project [01]. FOCCoS consists of the 3 cables (A, B and C) to integrate and operate the instruments easily [02]. At the present stage, we are about to complete the integration of the 3 cables by building Cable B that intermediates the telescope’s light gathering and light output devices for the spectrographs. Cable B, which is ~55m long, is subdivided into 4 units. Each unit has 600 optical fibers inserted into segmented tubes that are helically stranded around the tensile core element and inserted into a flexible metal conduit, which was made by industrial process. The construction of Cable B unit involves a coherent fiber distribution for a required mapping between the light collecting ends and the output ends positioned on the slits. Multi-fiber connector bench, strain relief boxes, and connection monitoring fiber devices are being built as part of subsystem integration process. Specific FRD measurement procedures for Cable B have been fully developed and implemented. The measurements are so far indicating similarly good results to those obtained in the evaluation of fibers from Cables A and C. For Cable B, FRD of some fibers has been traced to monitor the impact of the integration process.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is now being tested on the telescope. The instrument is equipped with very wide (1.3 degrees in diameter) field of view on the Subaru’s prime focus, high multiplexity by 2394 reconfigurable fibers, and wide waveband spectrograph that covers from 380nm to 1260nm simultaneously in one exposure. Currently engineering observations are ongoing with Prime Focus Instrument (PFI), Metrology Camera System (MCS), the first spectrpgraph module (SM1) with visible cameras and the first fiber cable providing optical link between PFI and SM1. Among the rest of the hardware, the second fiber cable has been already installed on the telescope and in the dome building since April 2022, and the two others were also delivered in June 2022. The integration and test of next SMs including near-infrared cameras are ongoing for timely deliveries. The progress in the software development is also worth noting. The instrument control software delivered with the subsystems is being well integrated with its system-level layer, the telescope system, observation planning software and associated databases. The data reduction pipelines are also rapidly progressing especially since sky spectra started being taken in early 2021 using Subaru Nigh Sky Spectrograph (SuNSS), and more recently using PFI during the engineering observations. In parallel to these instrumentation activities, the PFS science team in the collaboration is timely formulating a plan of large-sky survey observation to be proposed and conducted as a Subaru Strategic Program (SSP) from 2024. In this article, we report these recent progresses, ongoing developments and future perspectives of the PFS instrumentation.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is a very wide- field, massively multiplexed, and optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed in the 1.3 degree-diameter field of view. The spectrograph system has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously deliver spectra from 380nm to 1260nm in one exposure. The instrumentation has been conducted by the international collaboration managed by the project office hosted by Kavli IPMU. The team is actively integrating and testing the hardware and software of the subsystems some of which such as Metrology Camera System, the first Spectrograph Module, and the first on-telescope fiber cable have been delivered to the Subaru telescope observatory at the summit of Maunakea since 2018. The development is progressing in order to start on-sky engineering observation in 2021, and science operation in 2023. In parallel, the collaboration is trying to timely develop a plan of large-sky survey observation to be proposed and conducted in the framework of Subaru Strategic Program (SSP). This article gives an overview of the recent progress, current status and future perspectives of the instrumentation and scientific operation.
The Fiber Optic Cable and Connector System, FOCCoS, is a set of optical cables to feed the Prime Focus Spectrograph, PFS, for Subaru telescope [01,02]. The extremity responsible for delivering light to spectrographs is called, FCA, Fiber Cable A. Cable A is the cable installed at the Spectrograph side and consists of the Fiber Slit Assembly, FSA, the routing with its support and the Fiber Input Assembly, FIA. FSA is composed of a set of optical fibers arranged linearly on the Slit device and supported by the Frame, protected by segmented tubes and routed between strain relief boxes and the connection interface. FIA is composed by the Connector Bench (Gang Connector) that allow connection with Cable B, at the Subaru Telescope interface, to receive light from Cable C where the fibers end is coupled with microlens. As four Spectrographs are considered for PFS/Subaru, four units of Cable A are necessary. In this paper, we present in details of a complete FCA to be installed in the spectrograph bench. We discuss about the general design, methods used to manufacture the involved devices.
FOCCoS, "Fiber Optical Cable and Connector System", is a part of subsystem of Prime Focus Spectrograph”, for Subaru telescope. FOCCoS are divided in 3 different segments called Cable A, Cable B and Cable C. Multi-fibers connectors assure precise connection among all optical fibers of the segments, providing flexibility for instrument changes. Cable B is permanently installed at Subaru Telescope structure starting in a Connector Bench device and finishing at another different Connector Bench device. By this way, Cable B represent a link between the light entrance, from Cable C, and the light delivery, to Cable A. This cable will be routed to minimize the compression, torsion and bending caused by the cable weight and telescope motion. In this work, we present the current stage of development of Cable B as well as the detailing of its structures. In addition, we present the optical fiber cabling methodology and the test procedures involved in its characterization. A prototype of Cable B was constructed to help us to better understanding the real situation and was tested at Subaru Telescope.
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