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 Transneptunian Automated Occultation Survey (TAOS II) is a three robotic telescope project to detect stellar occultation events generated by TNOs. TAOS II aims to monitor about 10000 stars simultaneously at 20Hz to generate a significant event rate. The TAOS II cameras are designed to cover the 1.7 degree diameter field of view of the 1.3m telescopes with a mosaic of ten 4.5k × 2k e2v CIS 113 CMOS sensors. The CIS 113 has a back-illuminated thinned structure to provide similar performance to that of back-thinned CCDs. The CIS 113 device has 16 micron pixels with 8 outputs, with a plate scale about 0.63”/pixel. With the freedom of direct row and column addressing, star boxes with sizes of 8 × 8 pixels in each sensor can be sampled at 20 Hz or higher with a pixel rate of 1M pixel/sec per channel. The sensors, mounted on a single Invar plate, are cooled to an operating temperature of about 200K by a cryogenic cooler. The gap between two sensors is about 0.5mm. The control electronics consist of an analog part and a Xilinx FPGA based digital circuit. One FPGA is needed to control and process the signal from each CIS 113 chip. Two large PCBs were used to fanout signals from the 10 CMOS devices through the vacuum chamber wall. A synchronization circuit receives a pulse from the control building to ensure the timing error of exposures of the three cameras is within 1 ms. The cameras were delivered and installed on the TAOS telescopes in 2023 and series of tests and adjustments have been carried out to optimize the performance. In this presentation, the camera performance in the full frame mode and the window mode will be detailed. The synchronization and the adjustment among the three cameras will also be presented.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degrees diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners and fiducial fibers are located. In addition, the acquisition and guiding cameras (AGCs), the cable wrapper, the fiducial fiber illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy. The assembly, integration and verification of PFI was completed in 2021. The performance of PFI meets the requirements and it was delivered to Subaru telescope in June 2021. Consequently, various tests and engineering runs were carried out to calibrate the PFI and verify the performance of the PFI with the telescope.
The Transneptunian Automated Occultation Survey (TAOS II) is a three robotic telescope project to detect stellar occultation events generated by TransNeptunian objects (TNOs). TAOS II aims to monitor about 10000 stars simultaneously at 20Hz to generate a significant event rate. The TAOS II cameras are designed to cover the 1.7 degree diameter field of view of the 1.3m telescopes with a mosaic of ten 4.5k × 2k Teledyne e2v CIS 113 CMOS sensors. The CIS 113 has a back-illuminated thinned structure to provide similar performance to that of back-thinned CCDs. The CIS 113 device has 16 micron pixels with 8 outputs, with a plate scale about 0.63”/pixel. With the freedom of direct row and column addressing, star boxes with sizes of 8 × 8 pixels in each sensor can be sampled at 20 Hz or higher with a pixel rate of 1M pixel/sec per channel. The sensors, mounted on a single Invar plate, are cooled to an operating temperature of about 200K by a cryogenic cooler. The surfaces of the sensors were mounted to be within 30 microns to maintain a flat focal plane. The gap between two sensors is about 0.5mm. The control electronics consist of an analog part and a Xilinx FPGA based digital circuit. One FPGA controls and processes the signal from each CIS 113 chip. Two large PCBs were used to fanout signals from the 10 CMOS devices through the vacuum chamber wall. A synchronization circuit receives a pulse from the control center to ensure the timing accuracy of exposures of the three cameras is within 1 ms.
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 Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degrees diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners and fiducial fibers are located. In addition, the acquisition and guiding cameras (AGCs), the cable wrapper, the fiducial fiber illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy. The delivery of PFI components started in 2017. After the verification of these components, the mechanical structure of the PFI is fully assembled in early 2019 and all Cobra positioners are integrated in summer 2020. A temperature controlled chamber with precise x-y scanner was setup for the verification of the fiber positioners. The testing of the target convergence performance of Cobra positioners is now in progress.
We report the testing results of the Teledyne e2v CIS 113 CMOS sensor at temperatures from room temperature down to 168K. The CIS 113 sensor is a customized device for the Transneptunian Automatic Occultation Survey (TAOS II) project. The sensor has 1920 × 4608, 16 μm pixels with 8 outputs. The pixels have a 5T design to provide anti-blooming capability with 18 μm thick high resistivity epitaxial silicon. The sensor provides two parallel and eight serial registers so the region of interests can be addressed and rapidly read out separately through different output channels. More than one thousand 8 × 8 star boxes can be sampled at a frame rate higher than 20 Hz. With a package similar to large format Teledyne e2v CCDs, the CIS 113 is three-side buttable. The device shows peak QE about 77% in 500-600 nm, readout noise around 3eand dark current lower than 2 e-/s/pix at -40 ℃. The linear full well for the device is higher at lower temperature and it is about 14400 e- at temperature lower than 210K. The device performance meets the science requirements with the operation temperature around 200K for TAOS II.
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.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS will cover a 1.3 degree diameter field with 2394 fibers to complement the imaging capabilities of Hyper SuprimeCam. To retain high throughput, the final positioning accuracy between the fibers and observing targets of PFS is required to be less than 10 μm. The metrology camera system (MCS) serves as the optical encoder of the fiber positioners for the configuring of fibers. MCS provides the fiber positions within a 5 microns error over the 45 cm focal plane. The information from MCS will be fed into the fiber positioner control system for the closed loop control. MCS locates at the Cassegrain focus of Subaru telescope to cover the whole focal plan with one 50M pixel Canon CMOS camera. It is a 380 mm aperture Schmidt type telescope which generates uniform spot size around 10 µm FWHM across the field for reasonable sampling of the point spreading function. An achromatic lens set is designed to remove the possible chromatic error due to the variation of the LED wavelength. Carbon fiber tubes are used to provide stable structure over the operation conditions without focus adjustments. The CMOS sensor can be read in 0.8 s to reduce the overhead for the fiber configuration. The positions of all fibers can be obtained within 0.5 s after the readout of the frame. This enables the overall fiber configuration to be less than 2 minutes. MCS is installed inside a standard Subaru Cassgrain Box. All components generate heat are located inside a glycol cooled cabinet to reduce the possible image motion due to the heat. The integration of MCS started from fall 2017 and it was delivered to Subaru in April 2018. In this report, the performance of MCS after the integration and verification process in ASIAA and the performance after the delivery to Subaru telescope are presented.
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 is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS will cover a 1.3 degree diameter field with 2394 fibers to complement the imaging capabilities of Hyper SuprimeCam. To retain high throughput, the final positioning accuracy between the fibers and observing targets of PFS is required to be less than 10 microns. The metrology camera system (MCS) serves as the optical encoder of the fiber motors for the configuring of fibers. MCS provides the fiber positions within a 5 microns error over the 45 cm focal plane. The information from MCS will be fed into the fiber positioner control system for the closed loop control. MCS will be located at the Cassegrain focus of Subaru telescope in order to cover the whole focal plane with one 50M pixel Canon CMOS camera. It is a 380mm Schmidt type telescope which generates a uniform spot size with a ~10 micron FWHM across the field for reasonable sampling of the point spread function. Carbon fiber tubes are used to provide a stable structure over the operating conditions without focus adjustments. The CMOS sensor can be read in 0.8s to reduce the overhead for the fiber configuration. The positions of all fibers can be obtained within 0.5s after the readout of the frame. This enables the overall fiber configuration to be less than 2 minutes. MCS will be installed inside a standard Subaru Cassgrain Box. All components that generate heat are located inside a glycol cooled cabinet to reduce the possible image motion due to heat. The optics and camera for MCS have been delivered and tested. The mechanical parts and supporting structure are ready as of spring 2016. The integration of MCS will start in the summer of 2016. In this report, the performance of the MCS components, the alignment and testing procedure as well as the status of the PFS MCS will be presented.
The Transneptunian Automated Occultation Survey (TAOS II) is a three robotic telescope project to detect the stellar occultation events generated by TransNeptunian Objects (TNOs). TAOS II project aims to monitor about 10000 stars simultaneously at 20Hz to enable statistically significant event rate. The TAOS II camera is designed to cover the 1.7 degrees diameter field of view of the 1.3m telescope with 10 mosaic 4.5k×2k CMOS sensors. The new CMOS sensor (CIS 113) has a back illumination thinned structure and high sensitivity to provide similar performance to that of the back-illumination thinned CCDs. Due to the requirements of high performance and high speed, the development of the new CMOS sensor is still in progress. Before the science arrays are delivered, a prototype camera is developed to help on the commissioning of the robotic telescope system. The prototype camera uses the small format e2v CIS 107 device but with the same dewar and also the similar control electronics as the TAOS II science camera. The sensors, mounted on a single Invar plate, are cooled to the operation temperature of about 200K as the science array by a cryogenic cooler. The Invar plate is connected to the dewar body through a supporting ring with three G10 bipods. The control electronics consists of analog part and a Xilinx FPGA based digital circuit. One FPGA is needed to control and process the signal from a CMOS sensor for 20Hz region of interests (ROI) readout.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus of the 8.2m Subaru telescope. PFS will cover 1.3 degree diameter field with 2394 fibers to complement the imaging capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber positioners are located. In addition, the acquisition and guiding cameras (AGCs), the optical fiber positioner system, the cable wrapper, the fiducial fibers, illuminator, and viewer, the field element, and the telemetry system are located inside the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations within the required accuracy. In this report, the latest status of PFI development will be given including the performance of PFI components, the setup and performance of the integration and testing equipment.
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multifiber spectrograph with 2394 science fibers distributed across a 1.3-deg diameter field of view at the Subaru 8.2-m telescope. The wide wavelength coverage from 0.38 μm to 1.26 μm, with a resolving power of 3000, simultaneously strengthens its ability to target three main survey programs: cosmology, galactic archaeology and galaxy/AGN evolution. A medium resolution mode with a resolving power of 5000 for 0.71 μm to 0.89 μm will also be available by simply exchanging dispersers. We highlight some of the technological aspects of the design. To transform the telescope focal ratio, a broad-band coated microlens is glued to each fiber tip. A higher transmission fiber is selected for the longest part of the cable system, optimizing overall throughput; a fiber with low focal ratio degradation is selected for the fiber-positioner and fiber-slit components, minimizing the effects of fiber movements and fiber bending. Fiber positioning will be performed by a positioner consisting of two stages of piezo-electric rotary motors. The positions of these motors are measured by taking an image of artificially back-illuminated fibers with the metrology camera located in the Cassegrain container; the fibers are placed in the proper location by iteratively measuring and then adjusting the positions of the motors. Target light reaches one of the four identical fast-Schmidt spectrograph modules, each with three arms. The PFS project has passed several project-wide design reviews and is now in the construction phase.
The Transneptunian Automated Occultation Survey (TAOS II) is a three robotic telescope project to detect the stellar
occultation events generated by Trans Neptunian Objects (TNOs). TAOS II project aims to monitor about 10000 stars
simultaneously at 20Hz to enable statistically significant event rate. The TAOS II camera is designed to cover the 1.7
degree diameter field of view (FoV) of the 1.3m telescope with 10 mosaic 4.5kx2k CMOS sensors. The new CMOS
sensor has a back illumination thinned structure and high sensitivity to provide similar performance to that of the backillumination thinned CCDs. The sensor provides two parallel and eight serial decoders so the region of interests can be
addressed and read out separately through different output channels efficiently. The pixel scale is about 0.6"/pix with the
16μm pixels. The sensors, mounted on a single Invar plate, are cooled to the operation temperature of about 200K by a
cryogenic cooler. The Invar plate is connected to the dewar body through a supporting ring with three G10 bipods. The
deformation of the cold plate is less than 10μm to ensure the sensor surface is always within ±40μm of focus range. The
control electronics consists of analog part and a Xilinx FPGA based digital circuit. For each field star, 8×8 pixels box
will be readout. The pixel rate for each channel is about 1Mpix/s and the total pixel rate for each camera is about
80Mpix/s. The FPGA module will calculate the total flux and also the centroid coordinates for every field star in each
exposure.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus
of the 8.2m Subaru telescope. PFS will cover 1.3 degree diameter field with 2394 fibers to complement the imaging
capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the
interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber
positioners are located. In addition, the acquisition and guiding (AG) cameras, the optical fiber positioner system, the
cable wrapper, the fiducial fibers, illuminator, and viewer, the field element, and the telemetry system are located inside
the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match
those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations
within the required accuracy.
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime
focus of the 8.2m Subaru telescope. The metrology camera system of PFS serves as the optical encoder of the COBRA
fiber motors for the configuring of fibers. The 380mm diameter aperture metrology camera will locate at the Cassegrain
focus of Subaru telescope to cover the whole focal plane with one 50M pixel Canon CMOS sensor. The metrology
camera is designed to provide the fiber position information within 5μm error over the 45cm focal plane. The positions
of all fibers can be obtained within 1s after the exposure is finished. This enables the overall fiber configuration to be
less than 2 minutes.
We report the testing result of e2v CIS 107 CMOS sensor for temperature from 300K to 170K. The CIS 107 sensor is a prototype device with 10 different variations of pixel designs. The sensor has 1500 × 2000, 7 μm pixels with 4 outputs. Each variation covers 1500 × 200 pixels. These are 4T pixels with high resistivity epitaxial silicon and back thinned to 11μm. At room temperature, the several variants of pixels show peak QE higher than 90%, readout noise around 5e- and dark current around 50e-/s/pix. The full well is about 15000 e- due to the limitation of the transfer gate capacitor. The CIS 107 device was further characterized at different device temperatures from 170K to 300K. The readout noise decreases and the full well increases as the device is operated at lower temperature.
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394 science fibers, which
are distributed in 1.3 degree diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide wavelength
coverage from 0.38 μm to 1.26 μm, with the resolving power of 3000, strengthens its ability to target three main survey
programs: cosmology, Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with resolving
power of 5000 for 0.71 μm to 0.89 μm also will be available by simply exchanging dispersers. PFS takes the role for the
spectroscopic part of the Subaru Measurement of Images and Redshifts (SuMIRe) project, while Hyper Suprime-Cam
(HSC) works on the imaging part. HSC’s excellent image qualities have proven the high quality of the Wide Field
Corrector (WFC), which PFS shares with HSC. The PFS collaboration has succeeded in the project Preliminary Design
Review and is now in a phase of subsystem Critical Design Reviews and construction.
To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated microlens is glued to each fiber tip.
The microlenses are molded glass, providing uniform lens dimensions and a variety of refractive-index selection. After
successful production of mechanical and optical samples, mass production is now complete. Following careful
investigations including Focal Ratio Degradation (FRD) measurements, a higher transmission fiber is selected for the
longest part of cable system, while one with a better FRD performance is selected for the fiber-positioner and fiber-slit
components, given the more frequent fiber movements and tightly curved structure. Each Fiber positioner consists of two
stages of piezo-electric rotary motors. Its engineering model has been produced and tested. After evaluating the statistics
of positioning accuracies, collision avoidance software, and interferences (if any) within/between electronics boards,
mass production will commence. Fiber positioning will be performed iteratively by taking an image of artificially back-illuminated
fibers with the Metrology camera located in the Cassegrain container. The camera is carefully designed so
that fiber position measurements are unaffected by small amounts of high special-frequency inaccuracies in WFC lens
surface shapes.
Target light carried through the fiber system reaches one of four identical fast-Schmidt spectrograph modules, each with
three arms. All optical glass blanks are now being polished. Prototype VPH gratings have been optically tested. CCD
production is complete, with standard fully-depleted CCDs for red arms and more-challenging thinner fully-depleted
CCDs with blue-optimized coating for blue arms. The active damping system against cooler vibration has been proven to
work as predicted, and spectrographs have been designed to avoid small possible residual resonances.
The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project has been
endorsed by Japanese community as one of the main future instruments of the Subaru 8.2-meter telescope at Mauna Kea,
Hawaii. This optical/near-infrared multi-fiber spectrograph targets cosmology with galaxy surveys, Galactic archaeology,
and studies of galaxy/AGN evolution.
Taking advantage of Subaru’s wide field of view, which is further extended with the recently completed Wide Field
Corrector, PFS will enable us to carry out multi-fiber spectroscopy of 2400 targets within 1.3 degree diameter. A
microlens is attached at each fiber entrance for F-ratio transformation into a larger one so that difficulties of spectrograph design are eased. Fibers are accurately placed onto target positions by positioners, each of which consists of two stages
of piezo-electric rotary motors, through iterations by using back-illuminated fiber position measurements with a widefield
metrology camera. Fibers then carry light to a set of four identical fast-Schmidt spectrographs with three color arms
each: the wavelength ranges from 0.38 μm to 1.3 μm will be simultaneously observed with an average resolving power
of 3000.
Before and during the era of extremely large telescopes, PFS will provide the unique capability of obtaining spectra of
2400 cosmological/astrophysical targets simultaneously with an 8-10 meter class telescope. The PFS collaboration, led
by IPMU, consists of USP/LNA in Brazil, Caltech/JPL, Princeton, and JHU in USA, LAM in France, ASIAA in Taiwan,
and NAOJ/Subaru.
The Prime Focus Spectrograph (PFS) is a new multi-fiber spectrograph on Subaru telescope. PFS will cover around 1.4
degree diameter field with ~2400 fibers. To ensure precise positioning of the fibers, a metrology camera is designed to
provide the fiber position information within 5 μm error. The final positioning accuracy of PFS is targeted to be less than
10 μm. The metrology camera will locate at the Cassegrain focus of Subaru telescope to cover the whole focal plan. The
PFS metrology camera will also serve for the existing multi-fiber infrared spectrograph FMOS.
We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe
Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four
identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each
spectrograph will have three channels covering wavelength ranges 3800 Å - 6700 Å, 6500 Å - 10000 Å, and 9700 Å -
13000 Å, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red
channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For
the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for
short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical
design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in
the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling
scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics.
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