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.
The Spectrograph System (SpS) of Subaru Prime Focus Spectrograph is fed by 2400 fibers and consists of four identical spectrograph modules with 4 arms and 600 fibers each. This paper outlines the overall integration process for the spectrograph module series as completed at the Subaru Telescope. Many partners from the Subaru PFS Collaboration and industry contributed to this large multi-object spectrograph system. The initial integration of the so-called "one-channel prototype" began in 2015. The first spectrograph module was delivered to Subaru in 2019, and the fourth module was delivered in late 2023, with delays due to both technical difficulties and scheduling challenges, including the impact of COVID-19 on the large PFS spectrograph system collaboration. The integration and validation of each spectrograph module were performed at the Laboratoire d’Astrophysique de Marseille (LAM) prior to delivery and full integration at the Subaru Telescope. First, we briefly review the opto-mechanical design and development strategy for the SpS. We present the integration and testing procedures developed for this mini-series of four spectrograph modules. Several specific AIT tools were innovative and key to the process, and are worth reporting, including the software tools required for functional tests, housekeeping, and environment monitoring during integration, analysis of dimensional metrology, test and verification of optical alignment, and overall performance assessment. Specific processes were also developed for analyzing and resolving anomalies and issues encountered. We detail the strategies developed to resolve technical issues: thermal and vacuum performance; dimensional and optical metrology processes to correct for focus/tilt anomalies observed at the focal plane; handling, alignment, and optical testing of large optics such as the 340x340x20mm Volume Phase Holographic Grating (VPHG). We briefly report on a grating orientation issue discovered before the delivery of the last module, which is reported elsewhere. We quickly report the integration logistics: managing the shipping process, custom, and deliveries of many parts and modules among partners since 2014, and the final delivery and installation at the Subaru Telescope at the summit of Mauna Kea in Hawai`i in 2019, 2022, and 2023. We then dedicate a full section to the optical and thermal performance for the largest 8m-class multi-object spectrograph: the spectral channels and camera alignment performance results and the detailed optical performance of the four spectrograph modules (extracted from internal extended performance reports).
This paper presents thermal system and imaging performance test results from the first of four near infrared cameras for the SuMIRe (Subaru Measurement of Images and Redshifts) Prime Focus Spectrograph (PFS) being developed for the Subaru Telescope. The PFS near infrared camera is a large (330 mm entrance aperture to accommodate a 275 mm collimated beam diameter) cryogenically cooled vacuum Schmidt camera with a 300 mm focal length that images dispersed light onto a 4k x 4k, 15 µm pixel, HgCdTe substrate-removed Teledyne 1.7 µm detector. The 230 kg camera contains just four optical elements: a two-element refractive corrector, a Mangin mirror, and a field flattening lens. This simple optical design produces good imaging performance considering the wide field and wavelength range, and it does so in large part due to the use of a Mangin mirror for the Schmidt primary. Thermal background, both in-band and out-of-band, is reduced to a scientifically acceptable level using cryogenically cooled optics, very black geometrically optimized baffling, and a pair of thermal rejection coatings that reject photons between the edge of the science bandpass and the detector cutoff. System operating temperature is achieved by a pair of closed-cycle cryocoolers, one dedicated to cooling the optics, and one dedicated to cooling the detector. Here we discuss the lab performance of the near infrared camera, both from the perspective of the thermal system and the optical system, including in-band and out-of-band performance.
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.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~ 1.6-2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward.
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