HiCIAO is a near-infrared, high contrast instrument which is specifically designed for searches and studies for
extrasolar planets and proto-planetary/debris disks on the Subaru 8.2 m telescope. A coronagraph technique
and three differential observing modes, i.e., a dual-beam simultaneous polarimetric differential imaging mode,
quad-beam simultaneous spectral differential imaging mode, and angular differential imaging mode, are used
to extract faint objects from the sea of speckle around bright stars. We describe the instrument performances
verified in the laboratory and during the commissioning period. Readout noise with a correlated double sampling
method is 15 e- using the Sidecar ASIC controller with the HAWAII-2RG detector array, and it is as low as 5 e-
with a multiple sampling method. Strehl ratio obtained by HiCIAO on the sky combined with the 188-actuator
adaptive optics system (AO188) is 0.4 and 0.7 in the H and K-band, respectively, with natural guide stars that
have R ~ 5 and under median seeing conditions. Image distortion is correctable to 7 milli-arcsec level using
the ACS data as a reference image. Examples of contrast performances in the observing modes are presented
from data obtained during the commissioning period. An observation for HR 8799 in the angular differential
imaging mode shows a clear detection of three known planets, demonstrating the high contrast capability of
The 8 m SUBARU telescope atop Mauna Kea on Hawaii will shortly be equipped with a 188 actuator adaptive optics system (AO 188). Additionally it will be equipped with a Laser guide star (LGS) system to increase the sky coverage of that system. One of the additional tip-tilt sensor which is required to operate AO 188 in LGS mode will be working in the infrared to further enhance the coverage in highly obscured regions of the sky. Currently, various options for this sensor are under study, however the baseline design is a pyramid wavefront sensor. It is currently planned to have this sensor be able to provide also information on higher modes in order to feed AO 188 alone, i.e. without the LGS when NIR-bright guide stars are available. In this paper, we will present the results of the basic design tradeoffs, the performance analysis, and the project plan. Choices to be made concern the number of subapertures available across the primary mirror, the number of corrected modes, control of the AO system in combination with and without LGS, the detector of the wavefront sensor, the operation wavelength range and so forth. We will also present initial simulation results on the expected performance of the device, and the overall timeline and project structure.
PYRAMIR is a pyramid wavefront sensor (PWFS) for the 97-actuator AO system installed on the Calar Alto 3.5 m
telescope. With its linear pupil sampling of 18 pixels, its maximum loop frequency of 140 Hz, and its sensing
wavelength range from 1.1 micron to 2.4 micron it should be able to deliver reasonably high Strehl ratios at the sensing
wavelength. This feature is still unique in the world of pyramid sensors. The first on-sky test of the system was carried
out in March 2006. In this paper we will present the first results of this test. Strehl measurements medium atmospheric
conditions, using reference stars of mJ=8mag and mJ=4 mag and were performed during this first on-sky run. A detailed
comparison to simulation results will also be presented in order to confirm whether the system works up to expectances.
While this experiment has not yet the potential to show for the very first time the superiority of the pyramid principle
over corresponding Hartmann-Shack systems in a real telescope environment, it was confirmed that PYRAMIR
performs up to expectances and a detailed comparison to the Shack-Hartmann system can be carried out in the next run.
The Subaru Telescope LGSAO system is a 188 elements curvature AO system currently under construction, and scheduled to have first light in March 2006 for the Natural Guide Star mode and March 2007 for the Laser Guide Star mode. A particularity of this system will be to perform curvature wavefront sensing with several extra-pupil distances, which significantly improves the closed-loop performance.
An overview of the predicted performance of the system is given for Natural Guide Star and Laser Guide Star modes.
The laser guide star adaptive optics (AO) system for Subaru Telescope is presented. The system will be installed at the IR Nasmyth platform, whereas the current AO system with 36 elements is operating at the Cassegrain focus. The new AO system has a 188 element wavefront curvature sensor with photon counting APD modules which is the largest control element curvature sensor system ever. The system will have 4-10 W solid state sum-frequency laser to generate a laser guide star. The laser launching telescope with 50 cm aperture will be installed at behind the secondary mirror. The laser unit will be installed on the third floor of the dome and the laser beam will be transferred to the laser launching telescope using single mode photonic crystal fiber cable.
The field of view of the optics is 2.7 arcmin to maximize the probability to find tilt guide stars for laser guide star operation. The expected Strehl ratio as raw AO performance is 0.46 at H-band under 0.60" seeing with 12 th mag guide star, and 0.71 for 8 th mag stars. New wavefront modulation technique, dual stroke membrane mirror control, is developed to reduce the tilt error which is more dominant for curvature sensor AO system.
The superb contrast imaging capability will be expected as natural guide star system.
The first light as the natural guide star system is planned in March 2006, the laser first light will be expected in March 2007.
As an upgrade plan of Subaru adaptive optics facility, laser-guide-star adaptive-optics (LGSAO) project is on going. One of key components of the project is a deformable mirror (DM). The DM for LGSAO is a bimorph type of PZT with 188 control elements. The specification of design is presented together with the analysis of stroke and vibration properties by FEM.
We present the development status of the laser system for Subaru Laser Guide Star Adaptive Optics System. We are manufacturing the quasi-continuous-wave sum frequency laser as a prototype. The optical efficiency of sum frequency generation normalized by the mode-locked fundamental YAG (1064 nm) laser output power is achieved to be 14 % using the non-linear crystal, periodically poled potassium titanyl phosphate (PPKTP). Output power at sodium D2 line was about 260 mW. The optical relay fiber and the laser launching telescope are also described in this paper. For the optical relay fiber, we are testing an index guided photonic crystal fiber (PCF), whose core material is filled by fused silica, and whose clad has close-packed air holes in two dimension. The coupling efficiency was evaluated as about 80 % using 1mW He-Ne laser. We introduce the design of laser launching telescope (LLT), which is a copy of VLT laser launching telescope, and the interface to the Subaru Telescope.
The laser guide star adaptive optics (AO) module for the Subaru Telescope will be installed at the f/13.9 IR Nasmyth focus, and provides the compensated image for the science instrument without change of the focal ratio. The optical components are mounted on an optical bench, and the flexure depending on the telescope pointing is eliminated. The transferred field of view for the science instrument is 2 arcmin diameter, but a 2.7 arcmin diameter field is available for tip-tilt sensing. The science path of the AO module contains five mirrors, including a pair of off-axis parabolic mirrors and a deformable mirror. It has also three additional mirrors for an image rotator. The AO module has a visible 188-element curvature based wavefront sensor (WFS) with photon-counting avalanche photodiode (APD) modules. It measures high-order terms of wavefront using either of a single laser (LGS) or natural guide star (NGS) within a 2 arcmin diameter field. The AO module has also a visible 2 x 2 sub-aperture Shack-Hartmann WFS with 16 APD modules. It measures tip-tilt and slow defocus terms of wavefront by using a single NGS within a 2.7 arcmin diameter field when a LGS is used for high-order wavefront sensing.
The module has also an infrared 2 x 2 sub-aperture Shack-Hartmann WFS with a HgCdTe array as an option. Both high- and low-order visible WFSs have their own guide star acquisition units with two steering fold mirrors. The AO module has also a source simulator. It simulates LGS and NGS beams, simultaneously, with and without atmospheric turbulence by two turbulent layer at about 0 and 6 km altitudes, and
reproduces the isoplanatism and the cone effect for the LGS beam.
We report on the significantly improved performance of the Infrared
Camera and Spectrograph (IRCS) for the Subaru Telescope. The IRCS
consists of the camera side for imaging and grism spectroscopy and the spectrograph side for echelle spectroscopy. Due to the low sensitivity of the previous Aladdin-II engineering grade InSb infrared array on the camera side, the capability of imaging and grism spectroscopy was reduced. Thus, we replaced the array on the camera side into the new Aladdin-III array in August 2001. The newly installed Aladdin-III array has 1.9 times higher quantum efficiency (95%), 2/3 lower read-out noise (12e- with 16 non-destructive-readout at 27.5K of the array temperature) and better cosmetics than the old Aladdin-II array. We have also obtained grism spectra for a comparison of performances with the old and the new arrays. The spectra with the new array show about twice better signal-to-noise for each spectral element and almost no systematic noise. Currently we have two different types of arrays: Aladdin-II array on the spectrograph side and the science grade Aladdin-III array on the camera side. We will also present dark current, read-out noise, linearity curve and the other characteristics as a function of array temperatures to summarize the current performance of both arrays. We plan to upgrade the Aladdin-II array on the spectrograph side to a new Aladdin-III array in summer 2003.
A 36-elements curvature adaptive optics (AO) system has been operating on the Subaru telescope for about one and a half year. We achieved a Strehl ratio of 0.3 in the K-band, which is a rather smaller value than we expected. While we are investigating the discrepancy between the obtained performance and the simulated performance of the current AO system and we are also improving the current AO system in terms of the Strehl performance and the observing efficiency. Meanwhile we have started to plan a next generation of Subaru AO system. Two major upgrades are proposed in this paper. One is to increase the number of subapertures as much as possible. Practically, the number of subapertures lies between 100 and 200. The size of subaperture becomes half to one-third of that of the current system and we expected that the K-band Strehl ratio will improve to more than 0.6. The first light of the higher order curvature AO system is scheduled for 2004. Another upgrade plan is to use a laser guide star (LGS). A single LGS is projected at the sodium layer with an output power of 4 W. Conceptual designs for the laser system, beam relay system, laser launching telescope and control system have begun. The first test of launching laser from Subaru telescope will be in 2005.
We present a note on low to medium resolution spectroscopy using adaptive optics (AO) system. A special focus is put on the problem of spectral slope variations. In principle a stellar image compensated by AO has a varying point spread function (PSF) strongly dependent on the observing wavelength. Even when the AO is working perfectly, the fraction of the energy in a finite size slit will change with the wavelength. The performance of AO correction is very sensitive to the observing conditions. Spectral slope variations directly connected to the wavelength dependency of the enclosed energy in the slit. Those features common and relatively harmless in conventional spectroscopy such as temporal variation in the seeing, brightness of the targets, imperfect slit peaking, atmospheric differential refraction, and fixed aperture size at spectral extraction, all introduce artificial continuum slopes. The degree of uncertainty in the spectral slope could be serious enough to interfere the observing goals in AO spectroscopy. A case for a spectroscopic observation for low mass stars is presented to demonstrate the problem. We found a steep continuum slope that is unrealistic for a low mass star. We undertook laboratory experiments with a calibration source in the AO system to test if the unrealistic continuum slope could be accounted for by the varying AO performance. In the experiments the "bluing" of the continuum slopes have been confirmed when the light source is dropping off of the slit or the wavefront reference source is faint. The effects are also qualitatively reproduced with calculations done by an AO simulation code.
We report current status of the IR Camera and Spectrograph (IRCS) for the Subaru Telescope. IRCS is a Subaru facility instrument optimized for high-resolution images with adaptive optics (AO) and tip-tilt at 1-5 micrometers . IRCS consists of two parts: one is a cross-dispersed spectrograph providing mid to high spectral resolution, the other is a near-IR camera with two pixel scales, which also serves as an IR slit-viewer for the echelle spectrograph. The camera also has grisms for low to medium resolution spectroscopy. We have just completed the first engineering run about one month before this SPIE conference. It was an initial performance evaluation without AO or tip-tilt to check IRCS and its interface to the telescope. We confirmed the basic imaging and spectroscopic capability we had estimated.
LEWIS is an IR spectrograph designed primarily for spectroscopy in the 3 micrometers region. It is an echelle type spectrograph using a coarse groove grating together with a prism as a cross-disperser. Using LEWIS, we can observe the whole L-band in one exposure with a resolving power over 1250, which makes observations very efficient. A Santa Barbara Research Center 256 X 256 InSb array is employed as a detector. The grating used is characterized by large groove spacing of 125 micrometers and is utilized at very high orders, 25th-37th order in the L-band. A closed-cycle cooler is employed to keep the optics at 90K, and to maintain the detector at 30K. So far, scientific observations have been made at the Steward Observatory 60 inch telescope on Mt. Lemmon, the Steward Observatory 61 inch telescope on Mt. Bigelow, and the Wyoming IR Observatory 88 inch telescope on Mt. Jelm. The achieved throughput of the spectrograph including the quantum efficiency of the detector is about 20 percent. With the present detector control system, observations are background limited at 3.5 micrometers using multiple correlated sampling, and a limiting magnitude of 8.2 mag is achieved for S/N equals 20 in 30 min integration time with 1.5m class telescopes.
CISCO is an IR camera and spectrograph based on a single 1024 X 1024 HgCdTe array detector, which has been developed as a back-end spectrograph of OHS. It is also designed to be mounted on the Cassegrain or Nasmyth focus directly as an independent instrument. In addition to the normal imaging and spectroscopy modes, CISCO has a slitless prism spectroscopy mode at resolving power of approximately 30. This mode is primarily aimed at detecting the H(alpha) emission line of forming galaxy at z equals 2.05-2.65. The development of CISCO is in near completion, showing results of test observations carried out using a 1.5m telescope.