Subaru telescope is currently in the process of upgrading its laser guide star (LGS) system. The newest upgrade will have a TOPTICA SodiumStar laser source (operates at ~22W and 589nm) which is then sent to a laser launch telescope (LLT) just behind the secondary mirror of the telescope. In order to send the laser light to the LLT, a system of 6 mirrors has been designed to relay the laser light. Since the distances between these mirrors are quite large (the largest is ~9m), it was necessary to model the system in order to determine the correct placement and proper alignment procedure of each of these mirrors. For simplicity, the complete mirror relay system (including parts of the LLT up to the beam expander lens) has been modeled as an 8 mirror system in order to complete a tolerance analysis. The results of this analysis suggest that alignment of the system should be possible to do with a simple pinhole alignment procedure.
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.
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.
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.
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 introduce a near-infrared camera named coronagraph imager with adaptive optics (CIAO) mounted on the Subaru 8m telescope. Combined with the Subaru 36 elements adaptive optics (AO), CIAO can produce nearly diffraction limited image with approximately 0.07 arcsec FWHM at K band and high dynamic range imaging with approximately 10 mag difference at 1 arcsec separation under typical seeing conditions. We have carried out performance tests of imaging without and with coronagraph mask since its first light observation held on 2000 February. Because of limited weather conditions, the performance under best seeing conditions has not been tested yet. At a typical natural seeing condition of 0.4 - 0.8 arcsec, halo component of PSF using 0.2 - 0.8 arcsec mask can be reduced up to 70% comparing with that without mask using AO. Even after correction, residual wave front error has typically 1.2 rad2 which corresponds to the Strehl ratio of approximately 0.3 at K band. Such wave front errors degrades the image quality; this is a common problem of coronagraph on the ground-based telescope with non high-order AO. Nevertheless we emphasize that there are various advantages on our coronagraph: the clean PSF of CIAO, reduction of readout noise, and less effect of detector memory problem. Compared with coronagraphs on smaller telescopes, the PSF shape is sharper and it brings higher detectability of sources around bright objects.
We report the development and performance of a near-IR polarimeter for the Subaru 8.2m telescope. The polarimeter is currently used with one of the Subaru instruments, CIAO, the stellar coronagraphic imager with adaptive optics. CIAO is the instrument specialized to obtain high contrast images of faint objects in the vicinity of bright objects. For achieving both high spatial resolution and high dynamic range, the instrument is used wiht the Subaru adaptive optics and has a dedicated cold coronagraphic capability. The polarimeter comprises two components. One component consists of an achromatic half-waveplate, an achromatic quarter-waveplate, and a calibration wire grid. Both half- and quarter-waveplates are rotatable and retractable, while the calibrator is only retractable. This componetn is placed upstream of any opticla components including adaptive optics system, which minimizes the effect of various mirros on instrumental polarization. The other component consists of two anlayzers, a cold wire grid and acold Wollastron prism. These are placed in the filter wheels of CIAO cryostat and can be chosen. The whole system is remotely controlled.
MIRTOS, Mid-IR Test Observation System, is a high spatial resolution mid IR (MIR) camera for the Subaru Telescope. It consists of two IR imagers. One is for MIR bands with a Si:As array with 320 by 240 pixels. It has 21 by 16 arcsec field of view (FOV) with a pixel scale of 0.067 arcsec. It also images the pupil of the telescope. The other is a near IR camera. A 256 by 256 InSb array with 0.028 arcsec/pixel is used to image 7 by 7 arcsec FOV at one corner of the MIR FOV. We apply Shift-and-Add (SAA) technique; a technique that shifts images detecting the displacements and adds them to cancel seeing. However it is often difficult to shift and add MIR images using a reference within because of low sensitivity in MIR for short exposure time. We solve this problem utilizing NIR images taken simultaneously as position references. We call this method two-wavelength shift-and-add (TWSAA). In this paper we show result from the test observations. 1) Pupil image was taken. It shows hot structures around the secondary mirror that are now planned to be covered by reflecting plates to direct the beam to the sky. 2) Correlation of motion between MIR peak position and NIR centroid position shows that NIR images can be used as TWSAA reference for MIR observations. 3) On a standard star and the core NGC 1068, SAA method was applied to reconstruct images. Resulting images show higher spatial resolution than previous observations.
We describe a near-IR coronagraphic camera built for use with the Subaru 8.2-m telescope and its adaptive optics system. The purpose of this instrument CIAO is to obtain high-resolution images of faint objects in close vicinity of bright objects at IR wavelengths. Such a desire is strong in astronomy, especially in the study of companion brown dwarfs and extra-solar planets, circumstellar disks around both young stellar objects and main-sequence stars, jets and outflows form both young stellar objects and main-sequence stars, jets and outflows from both young stars and evolved stars, circumnuclear regions around AGNs, and host galaxies of QSOs. CIAO is a 1-5 micron camera with tow focal plate scales: 22 milli-arcsec/pixel and 11 milli-arcsec/pixel. The camera is equipped with the standard broad-band filters as well as a number of narrow-band filters. Choice of masks, filters and camera lenses and optical alignment with collimator and detector are made with cryogenic motors. CIAO utilizes one ALLADIN II 'science'-grade detector array manufactured by SBRC. Occulting masks whose diameter ranges from 0.1 to 3 arcsec and several types of pupil masks are selectable, all cooled down to about 60 K and the detector is cooled to about 30 K. Also available are a R <EQ 1000 grism with coronagraphic slits and a polarimetric module. We also present preliminary results from the first commissioning run at the Subaru telescope.