We present a conceptual design to implement wide-field focal plane assembly with InGaAs image sensors which are being tested intensively and reveled to be promising for astronomical use. InGaAs image sensors are sensitive up to 1.7 microns and would open a new window for the wide-field near-infrared (NIR) imaging survey once large format sensors are developed. The sensors are not necessarily cooled down to below 100 K, which is the case for prevailing NIR image sensors such as HgCdTe, enabling us to develop the NIR camera based on the technique developed for the CCD camera in optical wavelength. The major technical challenges to employ InGaAS image sensors for wide-field NIR camera are implementation of focal plane assembly and thermal design. In this article, we discuss these difficulties and show how we can conquer based on our experience to build Hyper Suprime-Cam, which is a wide-field imager with 116 2k4k CCDs attached to Subaru Telescope.
We report the evaluation results of a commercially available InGaAs image sensor manufactured by Hamamatsu
Photonics K. K., which has sensitivity between 0.95μm and 1.7μm at a room temperature. The sensor format was
128×128 pixels with 20 μm pitch. It was tested with our original readout electronics and cooled down to 80 K by a
mechanical cooler to minimize the dark current. Although the readout noise and dark current were 200 e- and 20 e-
/sec/pixel, respectively, we found no serious problems for the linearity, wavelength response, and intra-pixel response.
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.
Hyper Suprime-Cam (HSC)1,2 is a wide field imaging camera with the field of view (FOV) 1.5 degree diameter, which is to be installed at the prime focus of the Subaru Telescope. The large FOV is realized by the 116 2K × 4K pixels fully depleted back-illuminated CCD (FDCCD) with 15 μm pixel square. The acceptance inspection of the CCDs started around the end of 2009 and finished June 2011. We measured basic characteristics such as charge transfer efficiency (CTE), dark current, readout noise, linearity and the number of the dead column for all CCDs, and measured the quantum effciency (QE) of 21 CCDs. As a result, we confirmed exceptional quality and performance fdor all CCDs ans were able to select the best pissible 116 CCDs. We also measured the flatness of each CCD at room temperature, and optimally placed them on the focal plane plate. In this paper, we report the results of the acceptance inspection asn the installation process into the HSC dewar3,4.
We introduce the detail of the control system of Hyper Suprime-Cam (HSC) and its performance. Although it
has almost 10 times as many CCDs (104) as existing camera (Suprime-Cam), it is controlled by the common
user interface, the Subaru Observation Software System (SOSS) with the Gen2 implementation through the
HSC local controller (OBCP). If we adopt parallel programming, the read-out time should be within 25 seconds
including 18.6 seconds of readout time which is comparable to the current Suprime-Cam.
We have developed a filter exchange unit (FEU) and a shutter of Hyper Suprime-Cam (HSC). FEU consists of two parts; the alignment mechanism of the filter in the optical path and a jukebox of the filters. The alignment mechanism can guarantee 10 μm position stability with respect to the focal plane CCDs. On the exchange sequence, a motorized cart grabs and pushes the filter from the jukebox. Each jukebox has 3 slots and we have two identical jukeboxes. The operation is fully automated and the entire exchange sequence takes 16 minutes. Also, we developed the focal-plane shutter with 1,030 mm diameter envelope and 60 mm thickness while having 600 mm aperture. We report the detail of design and implementation of the shutter and FEU, and installation procedure of FEU.
Hyper Suprime-Cam (HSC) is a next generation wide field optical camera developed for F/2 prime focus of the 8.2 m
Subaru telescope. The focal plane is about 600 mm in diameter where 116 CCDs (2k4k 15 micron square each) are
arranged and cooled down to -100°C. The HSC CCD cryostat system design is presented by Komiyama et al. (2010).
Since then, we made detail designs of the components, manufactured them and assembled the dewar. This paper presents
the actual performance of the system including flatness and parallelism of the SiC cold plate, stability of its temperature,
the amount of out-gassing.
WISH, Wide-field Imaging Surveyor for High-redshiftt, is a space mission concept to conduct very deep and widefield
surveys at near infrared wavelength at 1-5μm to study the properties of galaxies at very high redshift beyond the
epoch of cosmic reionization. The concept has been developed and studied since 2008 to be proposed for future
JAXA/ISAS mission. WISH has a 1.5m-diameter primary mirror and a wide-field imager covering 850 arcmin2. The
pixel scale is 0.155 arcsec for 18μm pitch, which properly samples the diffraction-limited image at 1.5μm. The main
program is Ultra Deep Survey (UDS) covering 100 deg2 down to 28AB mag at least in five broad bands. We expect to
detect <104 galaxies at z=8-9, 103-104 galaxies at z=11-12, and 50-100 galaxies at z<14, many of which can be feasible
targets for deep spectroscopy with Extremely Large Telescopes. With recurrent deep observations, detection and light
curve monitoring for type-Ia SNe in rest-frame infrared wavelength is also conducted, which is another main science
goal of the mission. During the in-orbit 5 years observations, we expect to detect and monitor <2000 type-Ia SNe up to
z~2. WISH also conducts Ultra Wide Survey, covering 1000deg2 down to 24-25AB mag as well as Extreme Survey,
covering a limited number of fields of view down to 29-30AB mag. We here report the progress of the WISH project
including the basic telescope and satellite design as well as the results of the test for a proto-model of the flip-type filter
exchanger which works robustly near 100K.
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe.
We will launch a 1.5m telescope equipped with 1000 arcmin2 wide-field NIR camera by late 2010's in order to conduct
unique ultra-deep and wide-area sky surveys at 1-5 micron. The primary science goal of WISH mission is pushing the
high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated
survey strategy. We expect to detect ~104 galaxies at z=8-9, ~3-6x103 galaxies at z=11-12, and ~50-100 galaxies at
z=14-17 within about 5 years of the planned mission life time. It is worth mentioning that a large fraction of these
objects may be bright enough for the spectroscopic observations with the extremely large telescopes. By adopting the optimized strategy for the recurrent observations to reach the depth, we also use the surveys to detect transient objects.
Type Ia Supernova cosmology is thus another important primary goal of WISH. A unique optical layout has been
developed to achieve the diffraction-limited imaging at 1-5micron over the required large area. Cooling the mirror and
telescope to ~100K is needed to achieve the zodiacal light limited imaging and WISH will achieve the required
temperature by passive cooling in the stable thermal environment at the orbit near Sun-Earth L2. We are conducting the
conceptual studies and development for the important components of WISH including the exchange mechanism for the
wide-field filters as well as the primary mirror fixation.
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.
We develop a prototype of data analysis system for the wide-field camera Hyper Suprime-Cam (HSC) at Subaru Telescope. The current prototype is optimized for data of the current Subaru prime-focus camera Suprime-Cam, which is a precursor instrument of HSC, to study the on-site data evaluation for wide-field imaging.
The system conducts realtime data evaluation for every data frame obtaining statistical information including seeing, sky-background level, astrometric solution, and photometric zeropoint when available.
Variations in time of the derived values are shown on a web-based status monitor. The on-demand analysis such as mosaicing analysis is performed using the data evaluation results.
This system consists of analysis pipelines responsible for data processing, and the analysis organizing software for controlling analysis tasks and data flow and the database.
The XML-based database maintains all the analysis results and analysis histories. Improvement of the analysis speed by parallel data processing is achieved with the aid of the organizing software.
This system has started operation in general observations since March 2010, and will be extended to process the 104 CCD's of HSC.
The system may be used for observing support and also possible to apply to another imaging-mode instruments in the future.
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
A dichroic mirror/filter can divide light into two different wavelength bands by the principle of interference. We proposed to use more than a dozen of these mirrors, and make a simultaneous imager in many color bands. This also enables us to make a powerful spectrograph which uses many CCDs. We here report the first light of UT 15-band Dichroic-Mirror Camera. We successfully obtained the first light at the Cassegrain focus of the 1.5-m Kanata telescope in May 2007. We also carried out the second observing run in March 2008. Our instrument covers a wide wavelength range (390-930nm), and the field of view is about 4.5 arcmin in diameter with 0.27arcsec/pixel. Image quality was limited by seeing (~1.2 arcsec at best). We describe basic design, characteristics, and performance of our instrument as well as early observational results. Future prospect of dichroic mirrors instruments will also be briefly discussed.
We report our activity on development of data analysis system dedicated for the Hyper Suprime-Cam (HSC),
which is a future wide-field camera at Subaru Telescope. The data analysis system (HSC-ANA) is intended for
the following achievements: (1) automated processing of an unprecedentedly huge amount of data frames without
frequent human interactions to achieve required depth and area of the key survey projects (2) immediate release
of best-effort object catalogs together with calibration information to user communities to maximize scientific
outputs. The system also enables general users to efficiently use archive data by providing appropriate meta data
describing data quality. We start with constructing a prototype data analysis system which involves minimal
functions to process data for the current prime-focus camera (Suprime-Cam). The prototype system is developed
based on combination of newly developed and existing software packages for imaging data and the framework
middleware which communicates with databases. This system is planned to help observers to perform their
observations with Suprime-Cam. Once the prototype system is evaluated, it will be scaled up to the full HSCANA
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.
The next generation wide field camera HSC (Hyper Suprime-Cam) on Subaru telescope is planned to
cover 1.5 degree diameter field with a focal plane size about 650mm. To minimize the impact to the telescope,
the design for the elements of the camera is constraint to the tight space and weight limits. In order to fit the
available space, the screen winding shutter and petal shape filter exchanger are designed for the HSC. The
CFRP is used for the structure to minimize the load. In this report, the design and analysis for the shutter and
filter exchanger system will be presented. The result for the shutter membrane tests will also be discussed.
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.
Proc. SPIE. 6269, Ground-based and Airborne Instrumentation for Astronomy
KEYWORDS: Microelectromechanical systems, Telescopes, Electronics, Digital signal processing, Computing systems, Signal processing, Cadmium sulfide, Charge-coupled devices, Analog electronics, Digital electronics
A next generation wide-field camera HyperSuprime proposed for the 8.2m Subaru telescope is planed to employ 176 2kx4k CCDs to cover a 2 degrees diameter field of view. The readout electronics is one of important parts of the instrument. The CCD has four signal outputs, and all of the CCDs are readout in 10 to 20 seconds. The total image size becomes 2.8 Gbytes which should be transferred to the observing room within the readout time. Furthermore, the instrument will be mounted on the prime focus of the telescope. To decrease the size, weight, and power consumption are important themes for HyperSuprime. We will present our effort and the possibilities discussed to realize the readout electronics.
A next generation wide-field camera, HyperSuprime, proposed for the 8.2m Subaru telescope is planned to employ 126 2k x 4k CCDs to cover a 1.5 degrees diameter field of view. This field of view is nearly ten times wider than the current prime focus camera, Suprime-Cam. The larger HyperSuprime must be designed to minimally impact the Subaru Telescope when installed. It should fit in the existing Inner-Hub and also the Top Unit Exchanger. The space and weight constraints are severe considering the tight optical tolerance. To achieve this, the we will adopt CFRP (Carbon Fiber Reinforced Plastic) for major mechanical structure.
We summarize the optical design of the wide-field corrector for HyperSuprime which is being considered as a next generation prime focus camera for Subaru Telescope. Two optical designs are investigated under several design constraints such as image quality, field curvature, focal length, etc. The corrector with 2 degree field of view attains good image quality at the wavelength between 600 nm and 1100 nm although the first lens is large (1.2 m in diameter) and three aspherical surfaces are required. The image quality for shorter wavelength than 600 nm is fair. The incident light blocked at the edge of the field is only 20% and the transmission is more than 80% if the multi-layer coating applied for the current Subaru prime focus corrector is available. The corrector with 1.5 degree field of view is designed as a smaller version of 2 degree corrector. The properties and performance of 1.5 degree corrector resemble those of 2 degree corrector, but 1.5 degree corrector has a merit that the focal plane is flat. The availability of large fused-silica blank up to about 200 kg is promising.
HyperSuprime is a next generation wide field camera proposed for the 8.3 m Subaru Telescope. The targeted field of view is larger than 1.5 deg in diameter, which will give us roughly 10 times increase of the survey speed compared with the existing prime focus camera (Suprime-Cam). An overview of the current status of the feasibility study is given.
We summarize the design and the specification of a next generation instrument for Subaru Telescope: a very wide-field (2°φ) CCD camera which we name HyperSuprime. The latest design of the corrector ensures 80% encircled energy diameter of 0".3 from 600 nm to 1100 nm over the 2°φ field of view. The size of the focal plane is 612 mm in diameter and covered by about 170 four side buttable 2kx4k CCDs. Fully depleted CCD which is now being developed is the primary candidate for HyperSuprime. The readout electronics is connected behind the CCD and this CCD package is screwed to the cold plate with three positioning pins. The large entrance window of the dewar is supported with additional ribs so that the dewar is evacuated and CCDs are cooled down to about -80°C. HyperSuprime equips with a filter exchanger which can accommodate four large mosaicked filters and a roll-type shutter.
The Suprime-Cam is a CCD camera which is attached to the prime focus of the Subaru Telescope. Ten MIT/LL CCDs are tiled with small gaps to realize large field of view (34' x 27') with 0.2 arcsec sampling. This makes the Suprime-Cam very powerful and unique instrument
among 8-10m class telescopes. We present basic design, key techniques, current status and performance of the Suprime-Cam. We also mention ongoing survey programs with the Suprime-Cam,
followed by future upgrade plans of the camera.
The Subaru telescope has an excellent performance of wide field of view at the prime focus. A big area of 30 feet times 24 feet is observable at a time with the prime focus camera. Making the best use of the wide view, we are constructing narrowband (NB) filter system consisting of 20 bands. This system covers the wavelengths between 4,000 angstrom and 10,000 angstrom. The band width (BW) varies form 200 angstrom to 400 angstrom depending on the center wavelength (CW). The resolving power of the system is 23. Each filter has a big dimension of 205mm times 170mm and excellent uniformities on CW, BW and peak transmittance. Employing this filter system, spectroscopy for all objects recorded in fields of view is possible at the wavelength resolution of R23. The limiting magnitude would reach 27AB in reasonable observation time even at long wavelength bands. Such deep NB imaging spectroscopic survey should provide huge catalogue on cosmological objects. Especially, photometric redshift analyses with higher spectral resolution of R23 than ordinary broadband system of R approximately equals 4, will revolutionarily develop studies on formation and evolution of galaxies together with search for large scale structures at high redshift, based on enormous statistics, for example, 104 or more galaxies at high redshift of z > 3. Also, a lot of objects having strong emission lines as QSO/AGNs and Ly(alpha) or more galaxies will be discovered, because NB filter is strong in detection of emission line. The use of NB filter is strong in detection of emission line. The use of NB filter system in survey observations is surely quite conservative in concept and time consuming in general. However, combining this method with the wide field of view provided in the largest class telescope, new window to the universe is going to open.
We are building an 8192 X 10240 CCD mosaic camera for 8 m Japanese Telescope (Subaru). The mosaic will consist of 2 X 5 arrays of 3-edge buttable 4096 X 2048 15 micrometer pixel imagers. Although several vendors have just started supplying the type of large format CCD, it is still in the development phase. Therefore, careful characterization and optimizations of individual CCD are critical. We describe the system used to evaluate several kinds of the CCDs. In addition to the CCD characterization, we also present the mechanical design of the mosaic focal plane which is an another issue to realize the large mosaic.