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 fabrication of the new medium-resolution grisms for MOIRCS onboard Subaru 8.2-m Telescope is presented. Our new grisms feature the state-of-the-art gratings that have amazing high efficiency and wide-spectral coverage manufactured by LightSmyth Technologies. The grating has the peak efficiency of over 96% and can cover the whole H-band wavelength range with over 90%. This is the first-time astronomical application case for the LightSmyth grating. We manufactured the custom-made H-band grism as well as the catalog product J-band grism. The cooling test of the grisms confirmed the stability of the wave-front error over the cooling cycle. On-sky performance test were achieved in July 2020, and we have confirmed the high sensitivity as well as the amazing flatness of the throughput of these grisms. We also confirmed that the anticipated ghosts by the 0-th order light does not affect to the science operation. We started opening the grisms to the Subaru community from August 2020.
We have developed an integral field unit (IFU) for the existing optical imaging spectrograph, Faint Object Camera And Spectrograph (FOCAS), on the Subaru telescope. FOCAS IFU finally saw a first light on March 2nd, 2018, and started the common use from 2019. In order to observe faint targets like distant galaxies, our IFU has a coarse sampling comparable to the best seeing size and high throughput. The field of view is 13.4 10.0 arcsec2 which is divided into 23 slices with the width of 0.435 arcsec. Our IFU has a slit separated by about 5.2 arcmin from an object field in order to simultaneously obtain a sky spectrum. We confirmed that the image quality is good enough for the 0.435-arcsec slice width and the best seeing size of 0.4 arcsec. Mean and median throughput of the IFU are respectively 85.0% and 87.3%. However some fields show lower throughput due to misalignment of the IFU optics and the worst throughput is 61.9% at one field corner. Flat fielding error is almost within ±3%, but worse errors are found at the low-throughput region. The worst error is 9% at the lowest throughput region.
The current status of IRIS imager at NAOJ is reported. IRIS (Infrared Imaging Spectrograph) is a first light instrument of TMT (Thirty Meter Telescope). IRIS has just passed the preliminary design review and moved forward to the final design phase. In this paper, optical and mechanical design of IRIS imager and prototyping activities conducted during the preliminary design phase are summarized.
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.
We report the current status of the laser guide star upgrade at Subaru Telescope with a new, more powerful TOPTICA/MPBC laser. While we recycle many of our existing components, such as laser launch telescope, we need to design a new mirror-based laser relay system to replace the current fiber-based relay to accommodate the high power beam. The laser unit has been delivered to Subaru office in March 2018 and installed in a testing lab in June 2018. We describe the preliminary design and its requirements and report future plans. This upgrade will not only improve our current adaptive optics system but also be the first step toward the future laser tomography and ground layer adaptive optics system at Subaru Telescope.
Alignment between the primary mirror of the telescope and wide field corrector (WFC) is necessary for Prime Focus Spectrograph (PFS) ,which is the next instrument for Subaru telescope in Hawaii. From 6 defocused star images we can align the optical axis of wide field corrector to primary mirror's optical axis with required accuracy.
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.
Wide-Field Optical Spectrograph (WFOS) is one of the first-light instruments of Thirty Meter Telescope (TMT), and developed in an international collaboration led by University of California Santa Cruz. It covers the wavelength range from 310 nm to 1 μm which is divided at around 550 nm by a dichroic mirror. Calcium Fluoride (CaF2) is very useful to reduce aberration and has good transmittance even at 310 nm. Because a large mono-crystal CaF2 is difficult to be manufactured, we might have to use a poly-crystal CaF2. Comparing a mono-crystal, the poly-crystal is expected to have worse optical index homogeneity and larger surface figure error after polishing. Those effects on an image quality are unclear. To verify those effects, we conducted a polishing test of a small poly-crystal CaF2 lens as a first step. As a result, we found figure error around the boundary. The figure error is ~139 nm PV and ~26 nm RMS. Comparing a Zemax simulation, it is confirmed that the figure error does not have significant effect on the image quality.
The PFS is a multi-object spectrograph fed by 2394 fibers at the prime focus of Subaru telescope. Since the F/# at the prime focus is too fast for the spectrograph, we designed a small concave-plano negative lens to be attached to the tip of each fiber that converts the telescope beam (F/2.2) to F/2.8. We optimized the lens to maximize the number of rays that can be confined inside F/2.8 while maintaining a 1.28 magnification. The microlenses are manufactured by glass molding, and an ultra-broadband AR coating (<1.5% for λ = 0.38 - 1.26μm) will be applied to the front surface.
We are developing an integral field unit (IFU) with an image slicer for the existing optical spectrograph, Faint Object Camera And Spectrograph (FOCAS), on the Subaru Telescope. The slice width is 0.43 arcsec, the slice number is 23, and the field of view is 13.5 × 9.89 arcsec2. Sky spectrum separated by about 5.7 arcmin from an object field can be simultaneously obtained, which allows us precise background subtraction. Slice mirrors, pupil mirrors and slit mirrors are all glass, and their mirror surfaces are fabricated by polishing. Our IFU is about 200 mm × 300 mm × 80 mm in size and 1 kg in weight. It is installed into a mask storage in FOCAS along with one or two mask plates, and inserted into the optical path by using the existing mask exchange mechanism. This concept allow us flexible operation such as Targets of Opportunity observations. High reflectivity of multilayer dielectric coatings offers high throughput (>80%) of the IFU. In this paper, we will report a final optical layout, its performances, and results of prototyping works.
The project, "ULTIMATE- SUBARU", stands for "Ultra-wide Laser Tomographic Imager and MOS with AO for Transcendent Exploration at SUBARU Telescope." ULTIMATE-SUBARU provides a wide-field near infrared instrument at Cassegrain focus with GLAO. Performance simulation of GLAO at Subaru Telescope indicates that uniform PSFs can be obtained across the field of view up to 20 arcmin in diameter. This paper describes a current status of ULTIMATE-SUBARU project, science objectives, performance simulation update, system overview, feasibility of adaptive secondary mirror, and laser system.
Hyper Suprime-Cam (HSC) is an 870 Mega pixel prime focus camera for the 8.2 m Subaru telescope. The wide field corrector delivers sharp image of 0.25 arc-sec FWHM in r-band over the entire 1.5 degree (in diameter) field of view. The collimation of the camera with respect to the optical axis of the primary mirror is realized by hexapod actuators whose mechanical accuracy is few microns. As a result, we expect to have seeing limited image most of the time. Expected median seeing is 0.67 arc-sec FWHM in i-band. The sensor is a p-ch fully depleted CCD of 200 micron thickness (2048 x 4096 15 μm square pixel) and we employ 116 of them to pave the 50 cm focal plane. Minimum interval between exposures is roughly 30 seconds including reading out arrays, transferring data to the control computer and saving them to the hard drive. HSC uniquely features the combination of large primary mirror, wide field of view, sharp image and high sensitivity especially in red. This enables accurate shape measurement of faint galaxies which is critical for planned weak lensing survey to probe the nature of dark energy. The system is being assembled now and will see the first light in August 2012.
Hyper Suprime-Cam (HSC) is the wide-field CCD camera which is attached to the prime focus of Subaru
Telescope. It covers the field of view of 1.5 degree in diameter by 116 2k x 4k fully-depleted CCDs. In this
paper, we present the conceptual design of optics and mechanics how to introduce spectroscopic mode to this
simple imager HSC. The design is based on the idea that the optical elements such as collimeter, grisms and
camera lenses are integrated as a ’filter’ of HSC. The incident light is folded by pickup mirror at filter layer and
introduced to the filter space. After passing the slit, the incident light is collimated by the collimeter lens and
divided into three wavelength ranges by dichroic mirrors. The collimated beam in each wavelength range is fed
to the grism and dispersed. The dispersed beam is converged by the camera lens and folded by 45 degree mirror
to the direction parallel to the optical axis. The resultant spectra are imaged on the main CCDs on the focal
plane. The space allowed for filters is 600 mm in diameter and 42 mm thick, which is very tight but we are
able to design spectroscopic optics with some difficulties. The spectral resolution is designed to be more than
1000 and the wavelength coverage is targeted to be 370–1050 nm to realize medium-resolution spectroscopy for
various type of objects. We show the optical design of collimeter, grism and camera lenses together with the
mechanical layout of the spectroscopic optics.
Hyper Suprime-Cam (HSC) employs 116 pieces of 2k×4k fully-depleted CCD with a total of 464 signal outputs to cover
the 1.5 degrees diameter field of view. The readout electronics was designed to achieve ~5 e of the readout noise and
150000 e of the fullwell capacity with 20 seconds readout time. Although the image size exceeds 2G Bytes, the readout
electronics supports the 10 seconds readout time for the entire CCDs continuously. All of the readout electronics and the
CCDs have already been installed in the camera dewar. The camera has been built with equipment such as coolers and an
ion pump. We report the readout performance of all channels of the electronics extracted from the recent test data.
We are developing an integral field unit (IFU) with an image slicer for the existing optical imaging spectrograph,
Faint Object Camera And Spectrograph (FOCAS), on the Subaru Telescope. Basic optical design has already
finished. The slice width is 0.4 arcsec, slice number is 24, and field of view is 13.5x 9.6 arcsec. Sky spectra
separated by about 3 arcmin from an object field can be simultaneously obtained, which allows us precise
background subtraction. The IFU will be installed as a mask plate and set by the mask exchanger mechanism
of FOCAS. Slice mirrors, pupil mirrors and slit mirrors are all made of glass, and their mirror surfaces are
fabricated by polishing. Multilayer dielectric reflective coating with high reflectivity (< 98%) is made on each
mirror surface. Slicer IFU consists of many mirrors which need to be arraigned with high accuracy. For such
alignment, we will make alignment jigs and mirror holders made with high accuracy. Some pupil mirrors need
off-axis ellipsoidal surfaces to reduce aberration. We are conducting some prototyping works including slice
mirrors, an off-axis ellipsoidal surface, alignment jigs and a mirror support. In this paper, we will introduce our
project and show those prototyping works.
Hyper Suprime-Cam (HSC) is the next generation wide-field imager for the prime focus of Subaru Telescope,
which is scheduled to receive its first light in 2011. Combined with a newly built wide-field corrector, HSC
covers 1.5 degree diameter field of view with 116 fully-depleted CCDs. In this presentation, we summarize the
details of the camera design: the wide-field corrector, the prime focus unit, the CCD dewar and the peripheral
devices. The wide-field corrector consists of 5 lenses with lateral shift type doublet ADC element. The novel
design guarantees the excellent image quality (D80 <0".3) over the field of view. On the focal plane, 116 CCDs
are tiled on the cold plate which is made of Silicon Carbide (SiC) and cooled down to -100 degrees by two pulse
tube coolers. The system is supported by the prime focus unit which provides a precise motion of the system to
align the wide-field corrector and the CCD dewar to the optical axis of the telescope.
Hyper Suprime-Cam (HSC) employs 116 of 2k×4k CCDs with 464 signal outputs in total. The image size
exceeds 2 GBytes, and the data can be readout every 10 seconds which results in the data rate of 210 Mbytes /
sec. The data is digitized to 16-bit. The readout noise of the electronics at the readout time of 20 seconds is
~0.9 ADU, and the one with CCD is ~1.5 ADU which corresponds to ~4.5 e. The linearity error fits within ±
0.5 % up to 150,000 e. The CCD readout electronics for HSC was newly developed based on the electronics
for Suprime-Cam. The frontend electronics (FEE) is placed in the vacuum dewar, and the backend electronics
(BEE) is mounted on the outside of the dewar on the prime focus unit. The FEE boards were designed to
minimize the outgas and to maximize the heat transfer efficiency to keep the vacuum of the dewar. The BEE
boards were designed to be simple and small as long as to achieve the readout time within 10 seconds. The
production of the system has been finished, and the full set of the boards are being tested with several CCDs
installed in the HSC dewar. We will show the system design, performance, and the current status of the
development.
We summarize the design of the camera dewar for Hyper Suprime-Cam (HSC) which is the next generation prime
focus camera for the Subaru Telescope. The camera dewar consists of six main components; base flange, focal
plane assembly, window assembly, wall assembly, front-end electronics asembly and back assembly. It is about 700
mm in diameter and 500 mm in height, accommodating 116 2k×4k full depletion type CCDs inside. The CCD
packages, whose heights are accurately controlled (P-V ~ 25μm), are installed on a silicon-carbide cold plate of 10 μm
flatness to ensure that the surface of CCDs is flat within the focal depth of the wide-field corrector (~ 34μm).
The cold plate is supported rigidly and thermally isolated by support posts which are made of Zirconia. We
carried out the deformation analysis and the thermal analysis of the dewar based on the finite-element analysis,
and demonstrate that the design is feasible. We also show the assembly sequence of the dewar.
We present methodology of the autoguider (AG) and Shack-Hartmann (SH) sensing systems which will be used for a wide-field camera, Hyper Suprime-Cam (HSC), on the prime focus of the Subaru 8.2-m telescope. For both systems, stellar images are formed on the HSC science CCDs. Although light from AG stars must pass
through bandpass filters, we can obtain enough photons for AG stars brighter than mAB < 14 mag in any bandpass filter assumed in order to achieve accurate autoguiding. Spatial number density of such bright stars from the SDSS database requires an area
of about two 2k×4k CCDs for AG stars. The optics of SH system except for the imaging CCDs is located within the HSC filter unit.
Hyper Suprime-Cam is planned to employ about 120 2k×4k fully-depleted CCDs with 4 signal outputs for each. The
data size of an image becomes larger than 2Gbytes. All of the CCDs are designed to be readout parallel within 20
seconds, and the readout noise is expected to be 5e. The frontend electronics will be mounted in a vacuumed cryostat,
and connected to the backend electronics mounted on the outside of the cryostat. The frontend electronics includes entire
analog circuits for CCD including CCD drivers, preamplifiers and ADC. The backend electronics consists of newly
developed gigabit Ethernet modules combined with 2Gbytes memory modules, and several supporting boards. We will
present the current status of the CCD readout electronics developments for HSC.
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