We present the current status of the ULTIMATE-Subaru Tomography Adaptive optics Research experimenT (ULTIMATE-START) project, an upcoming laser tomography adaptive optics (LTAO) system on the Subaru telescope. The main goal of this project is to realize high Strehl ratio AO correction not only in near-infrared bands but also in visible bands above 600 nm. Our LTAO system will be operated with four 32 × 32 Shack Hartmann wavefront sensors (SH-WFSs) and four laser guide stars (LGSs). The LTAO WFSs will be installed behind AO188, which is the current AO system on the Nasmyth platform of the Subaru telescope. We will use the low-order WFS and DM of AO188 for Tip-Tilt measurements with a natural guide star (NGS) and wavefront correction. The DM of AO188 will be upgraded to a 3228 element DM. Assembling of the LTAO WFS system has completed in 2022. Currently WFS data acquisition and tomographic wavefront (WF) estimation testing are underway. We also performed test observations of a prototype single SH-WFS unit with a NGS and LGS with the Subaru telescope. A new laser launching system has been installed. A single LGS is under on-sky performance verification for the open-use observations, and four LGS system, which can make an asterism with 10-40 arcsec diameter, will be installed in 2022. The first light of the entire LTAO system is planned in early 2023.
ULTIMATE-Subaru is a next facility instrumentation program of the Subaru Telescope. The goal of this project is to extend the wide-field capability of the Subaru to near-infrared (NIR), by developing a wide-field ground-layer adaptive optics (GLAO) system and wide-field NIR instruments. The GLAO system will uniformly improve the image quality up to 20-arcmin field of view in diameter by correcting for the ground-layer turbulence. The expected image quality after the GLAO correction is FWHM~0".2 in K-band under moderate seeing conditions. In this presentation, we present preliminary design overview of the GLAO system at the Cassegrain focus, which consist of an Adaptive Secondary Mirror, NGS and LGS wavefront sensor system, a laser guide star facility, and control system. We also present the prototyping activities to validate the selected design of the GLAO system.
ULTIMATE-Subaru is an on-going project at the Subaru Telescope for the next-generation wide-field infrared astronomy. The adaptive secondary mirror optically conjugated close to the ground level, is an important subsystem of ground-layer adaptive optics. Because the ground-layer is the dominant component in the total atmospheric turbulence existing near the aperture of the telescope, the correction of the ground-layer turbulence improves the seeing size over a wide field-of-view. The design together with the plan of the Subaru ASM including the interface to the telescope and the calibration strategy is presented.
Compact refractive adaptive optics (CRAO) is a visible compact adaptive optics (AO) system optimized for small telescopes. It was mounted on the 1.3 m Araki telescope of Koyama Astronomical Observatory (KAO) in Kyoto Sangyo University, Japan. CRAO aims to improve the natural seeing 3” to 0.8” at 500 nm at the KAO site. Thus, it needs a large format and highly frequent camera for wide field survey (WFS) and a largely segmented depth map (DM) because the natural seeing ∼3” at the KAO site is especially poor for astronomical observations. To improve the performance of CRAO with a new WFS and DM, we searched for the optimal AO parameters (the number of WFS subapertures (NWFS), the number of DM actuators (NDM), and the loop frequency (fL) with two AO simulators using yao and COMPASS. Consequently, we found that NWFS > 12×12, NDM > 80, and fL > 800 Hz are necessary to achieve the full width at half maximum (FWHM) < 0.8” for point spread function (PSF) under the KAO site’s atmospheric conditions. Finally, we calculated the limiting magnitude (Vlim) with commercially available sensors for WFS and DMs. By combining ORCA-Lightning (Hamamatsu Photonics) and DM97-15 (ALPAO), a deeper limiting magnitude (Vlim ∼ 4.4) can be achieved, even with a 1 m-class telescope.
We develop a covariance-based analytical algorithm to efficiently predict the performance of complex tomographic AO systems based Shack-Hartmann WFSs (SH-WFS). The algorithm produces a predicted point spread function (PSF) and a decomposed wavefront error for each error term and is implemented using GPU and CUDA libraries for efficient computation. In this paper, we introduce the basis of our algorithm and show the prediction results, computational speed, and comparison with end-to-end simulations for the ULTIMATE-SUBARU GLAO and LTAO systems as test cases.
We are developing a multi-conjugate adaptive optics (MCAO) system for monitoring observations of the solar system planets. The current goal of this MCAO system is a moderate improvement of spatial resolution (several tenths of an arcsecond) of the planetary image over about 50-arcsec field of view in the visible wavelength (0.5–1 µm) for 1.5-m class telescopes (1.6-m Pirka telescope of Hokkaido University and 1.5-m Kanata telescope of Hiroshima University) at moderate seeing (1–2 arcsec) sites in Japan. The system has two 140-element MEMS deformable mirrors, which conjugate the telescope pupil and 2.6 km altitude, and four 11×11-subaperture ShackHartmann wavefront sensors with a field of view of about 16 × 16 arcsec. The wavefronts would be measured by the correlation tracking of the patterns on the planet such as the clouds of Jupiter, as similar in the solar adaptive optics systems. The system have been mostly constructed and is currently being tested in the laboratory, and we are planning test observations in 2021. We describe the design, construction, expected performance, and current status of our MCAO system for continuous planetary imaging.
ULTIMATE-Subaru Tomography Adaptive optics Research experimenT (ULTIMATE-START) is a laser tomography AO project on the Subaru telescope. The project is planned to achieve high Strehl Ratio AO correction in NIR bands, and moderate AO correction in visible bands above 600nm. An asterism of 4 laser guide stars (LGSs) will be launched from the laser launching telescope behind the secondary mirror. The tomography wavefront sensing unit with four 32$times$32 Shack-Hartmann wavefront sensors will be installed behind the current facility LGS AO system, AO188. The deformable mirror of AO188 will be upgraded to a 64$times$64 element DM. The corrected light will be fed to the optical integral field spectrograph, 3DII, and NIR camera and spectrograph, IRCS, through a beam switching optics for IR-side Nasmyth focus instruments under development. The first light of the laser launching system and wavefront sensing unit is planned in 2021.
How much light from the astronomical object actually reaches the focal plane of a telescope? To what extent the sensitivity can be extended to both ends of the visible wavelengths – ultraviolet (UV) and infrared (IR) – as much as possible from the ground? And how to maintain good throughput of the telescope optics? In this report, we make a simplified model to show effect in the reflectivity change of the telescope mirror from the recoating and cleaning versus degradation focusing on a segmented primary mirror of a telescope. The better understandings and monitoring of these competing factors will help fine tune the scheduling of the in-situ cleaning such as CO2 cleaning. By maintaining the high throughput of the optics, it becomes more feasible to catch rare atmospheric condition whenever it becomes available for very sensitive UV or IR observations during Moon’s dark and bright phases, respectively. The degradation not recoverable by the cleaning is reset by replacing dirty segments with freshly coated ones. The importance of regular in-situ cleaning is evident when it takes long time to replace the large number of freshly coated segments. It is important to clean the entire aperture as much as possible when a wet condition is forecast; for once the contamination settles on the surface, CO2 cleaning alone won’t be able to recover good surface characteristics of reflectivity, scattering, and emissivity.
We present the results of the evaluation of the ensquared energy of eight commercially available and custom made Microlens arrays (MLAs) with different focal length Plano-Convex microlens. The highest efficiency is observed with a 300 μm pitch MLA with no AR-coating and square apertures, which show 79% light ensquared within the first dark ring compared to the uniform illumination of the sub-aperture. To quantitatively explain the observed difference in the ensquared energy, we measured the surface shape of these MLAs using a laser interferometer. The comparison between the ensquared energy and the surface shape inferred that the lower ensquared energy of a MLA than the other MLAs with same 300 μm pitch can be explained with the deviation of the ideal shape at the outer part of the each lens.
In order to measure the altitude profile of the atmospheric turbulence in real-time, we are applying a MASSDIMM method (Multi Aperture Scintillation Sensor and Differential Image Motion Monitor) to the ShackHartmann wavefront sensor data. Tomographic estimation of the atmospheric turbulence is a key technique in new generation of adaptive optics systems with multiple guide stars, and the real-time turbulence profiling provide a useful prior information for the tomography, which is an ill-posed inverse problem. By using the data of a Shack-Hartmann sensor, a turbulence profile in the same direction as the AO correction can be acquired. Moreover, since more information can be used compared with the traditional MASS-DIMM, the resolution in the height direction can be increased. This time, the data of the Shack-Hartmann sensor attached to Tohoku University 50cm telescope was analyzed, and the estimation of the turbulence profile was obtained. Similar profiles were obtained while the elevation of the star and the apparent distance to the turbulence changed in one hour monitoring measurements. The results supported the validity of the method.
We aim at improving solar images partially compensated by Adaptive Optics (AO) or Ground-Layer (GL) AO using a phase diversity (PD) method. To reduce computational time in the PD execution, we develop a computer cluster system that enables restoration of several images in parallel. We set a PD-observational system downstream of an AO system in the Hida Observatory in Japan. Driving the AO system, we recorded focused and defocused solar images. They were segmented to partial images, and then were restored by the PD method. We show the results of solar image restoration, and also demonstrate the reduction of processing time by the computer cluster.
We report experiments of solar ground-layer (GL) adaptive optics (AO) using the 60cm domeless solar telescope of the Hida Observatory, Japan. We developed an averaging-type GL wavefront sensor and confirmed that it properly worked in computer simulations. We set the wavefront sensor behind a conventional AO system and modified AO software so as to drive a deformable mirror using the GL sensor. We conducted solar observations with the GLAO system in September, 2017. It worked to improve observational images over wide fields.
This paper presents the overview of on-going and future adaptive optics (AO) activities at the Subaru telescope on the top of Maunakea in Hawaii. Currently, two AO systems are running at the Subaru telescope: AO188, a facility single-conjugate AO system with a bimorph deformable mirror and a curvature wavefront sensor with 188 elements, and SCExAO, an additional extreme AO system operating behind AO188 and specialized for exoplanet sciences. We recently started AO188 upgrade project to improve its performance for the next 5-10 years, which will also help improving SCExAO performance. These upgrades are in line with a development for the ULTIMATE-Subaru ground layer AO system.
We present on-sky results from the wide field ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea. We demonstrate improvements in image quality at visible wavelengths under a variety of seeing conditions. We discuss the gains for a variety of figures of merit including the full-width at half-maximum, the equivalent noise area, and the encircled energy diameter. These gains and figures of merit are discussed in the context of our GLAO science cases. In addition, we present the system image quality error budget, measurements of the dominant error terms, and their impact on the delivered focal plane images.
We have developed the near-infrared high-spatial resolution imaging and spectro-polarimetric modes with the laser guide adaptive optics system (AO188) and the Infrared Camera and Spectrograph (IRCS) of the 8.2-m Subaru telescope. A LiNbO3 Wollaston prism (as dual beam analyzer) and focal plane masks were installed into the camera section of the IRCS cryostat, enabling us to perform the low- and medium-resolution grism spectropolarimetry (λ/Δλ = 100-1960) as well as the imaging-polarimetry, in conjunction with a half-wave retarder, which had been introduced for the HiCIAO instrument originally, at the front of the AO188 system. The designed wavelength coverage of the Wollaston prism is 0.8-5 μm, although the polarimetry at the 0.95-2.5 μm region is presented in this paper because of the limitations on the current retarder and the dichroic beam splitter of AO188. The focal plane masks, which are reflecting mirror or slits made with tungsten carbide, provide two or four rectangular focal plane apertures with an individual field of view of 4.4 arcsec × 21 arcsec or 4.4 × 54 arcsec for the imaging-polarimetry, or two or four slits with a width of 0.10, 0.15, 0.225, and 0.60 arcsec and a length of 4.4 arcsec for the spectro-polarimetry. The Wollaston prism and polarimetry masks were installed on June and July 2013, and the polarimetric modes had the first light on October 2013. The polarization efficiency is 88-96% and 55-80% at maximum for the imaging- and spectro-polarimetry, respectively, and it depends heavily on the angle of image rotator of AO188. The measured instrumental polarization, which is introduced by the telescope tertiary mirror mainly, is 0.3-0.7%. We describe the design and current performance of the polarimetric function in the near-infrared region.
This letter proposes a method of configuring a testing target to evaluate the performance of adaptive optics microscopes. In this method, a testing slide with fluorescent beads is used to simultaneously determine the point spread function and the field of view. The point spread function is reproduced to simulate actual biological samples by etching a microstructure on the cover glass. The fabrication process is simplified to facilitate an onsite preparation. The artificial tissue consists of solid materials and silicone oil and is stable for use in repetitive experiments.
Adaptive optics is useful not only for the suppression of the blur of image, but also for the reduction of the aberration on the transmitted light. Recent years, methods for optical manipulation of biological tissue under the microscope is becoming available, whereas the live tissue often causes the considerable amount of optical aberration that prevents the clear convergence of the laser beam onto the target cell. This research shows the basic experiments to improve the convergence of the laser beam focused on the tissue in microscope by correcting the optical aberration using adaptive optics.
Live-cell imaging using fluorescent molecules is now essential for biological researches. However, images of living cells are accompanied with blur, which becomes stronger according to the depth inside the cells and tissues. This image blur is caused by the disturbance on light that goes through optically inhomogeneous living cells and tissues. Here, we show adaptive optics (AO) imaging of living plant cells. AO has been developed in astronomy to correct the disturbance on light caused by atmospheric turbulence. We developed AO microscope effective for the observation of living plant cells with strong disturbance by chloroplasts, and successfully obtained clear images inside plant cells.
We present the integration status for 'imaka, the ground-layer adaptive optics (GLAO) system on the University of Hawaii 2.2-meter telescope on Maunakea, Hawaii. This wide-field GLAO pathfinder system exploits Maunakea's highly confined ground layer and weak free-atmosphere to push the corrected field of view to ∼1/3 of a degree, an areal field approaching an order of magnitude larger than any existing or planned GLAO system, with a FWHM ∼ 0.33" in the visible and near infrared. We discuss the unique design aspects of the instrument, the driving science cases and how they impact the system, and how we will demonstrate these cases on the sky.
Prior statistical knowledge of the turbulence such as turbulence strength, layer altitudes and the outer scale is essential for atmospheric tomography in adaptive-optics (AO). These atmospheric parameters can be estimated from measurements of multiple Shack-Hartmann wave-front sensors (SH-WFSs) by the SLOpe Detection And Ranging (SLODAR). In this paper, we present the statistics of the vertical CN2 and the outer scale L0 at Maunakea in Hawaii estimated from 60 hours telemetry data in total from multiple SH-WFSs of RAVEN, which is an on-sky multi-object AO demonstrator tested on the Subaru telescope. The mean seeing during the RAVEN on-sky observations is 0.475 arcsec, and 55% turbulence is below 1.5 km. The vertical profile of CN2 from the RAVEN SLODAR is consistent with the profiles from CFHT DIMM and MASS, and TMT site characterization.
This paper presents the AO performance we got on-sky with RAVEN, a Multi-Object Adaptive Optics (MOAO) technical and science demonstrator installed and tested at the Subaru telescope. We report Ensquared-Energy (EE) and Full Width at Half Maximum (FWHM) measured from science images on Subaru's IRCS taken during all of the on-sky observing runs. We show these metrics as function of different AO modes and atmospheric conditions for two asterisms of natural guide stars. The performances of the MOAO and Ground-Layer AO (GLAO) modes are between the classical Single-Conjugate AO (SCAO) and seeing-limited modes. We achieve the EE of 30% in H-band with the MOAO correction, which is a science requirement for RAVEN. The MOAO provides sightly better performance than the GLAO mode in both asterisms. One of the reasons which cause this small difference between the MOAO and GLAO modes may be the strong GL contribution. Also, the performance of the MOAO modes is affected by the accuracy of the on-sky turbulence profiling by the SLOpe Detection And Ranging (SLODAR) method.
We are conducting a concept study on a wide field of regard (FoR) Multi-Object Adaptive Optics (MOAO) system for Thirty Meter Telescope (TMT-AGE: TMT-Analyzer for Galaxies in the Early universe). The main science target of TMT-AGE is high-redshift galaxies. Considering the small number density of high-redshift galaxies, enlarging the FoR of an MOAO system up to around 100 is critical. In order to increase the FoR of an MOAO system, we propose a new tomographic reconstruction method. In the new method, we use atmospheric wind profiles and WFS measurements at previous time steps to increase the number of virtual measurement points of atmospheric turbulence layers for tomographic reconstruction. We present the results of numerical simulations with the new tomography method. The simulations show the new method can reduce the tomographic error in a wide FoR.
A future plan for the next-generation Subaru adaptive optics, is a system based on an adaptive secondary mirror. A ground-layer adaptive optics combined with a new wide-field multi-object infrared camera and spectrograph will be a main application of the adaptive secondary mirror. A preliminary simulation results show that the resolution achieved by the ground-layer adaptive optics is expected to be better than 0.2 arcsecond in the K-band over 15 arcminutes field-of-view. In this paper, the performance simulation is updated taking dependence on observation conditions, the zenith angle and the season, into account.
Current AO observations rely heavily on the AO188 instrument, a 188-elements system that can operate in natural or laser guide star (LGS) mode, and delivers diffraction-limited images in near-IR. In its LGS mode, laser light is transported from the solid state laser to the launch telescope by a single mode fiber. AO188 can feed several instruments: the infrared camera and spectrograph (IRCS), a high contrast imaging instrument (HiCIAO) or an optical integral field spectrograph (Kyoto-3DII). Adaptive optics development in support of exoplanet observations has been and continues to be very active. The Subaru Coronagraphic Extreme-AO (SCExAO) system, which combines extreme-AO correction with advanced coronagraphy, is in the commissioning phase, and will greatly increase Subaru Telescope’s ability to image and study exoplanets. SCExAO currently feeds light to HiCIAO, and will soon be combined with the CHARIS integral field spectrograph and the fast frame MKIDs exoplanet camera, which have both been specifically designed for high contrast imaging. SCExAO also feeds two visible-light single pupil interferometers: VAMPIRES and FIRST. In parallel to these direct imaging activities, a near-IR high precision spectrograph (IRD) is under development for observing exoplanets with the radial velocity technique. Wide-field adaptive optics techniques are also being pursued. The RAVEN multi-object adaptive optics instrument was installed on Subaru telescope in early 2014. Subaru Telescope is also planning wide field imaging with ground-layer AO with the ULTIMATE-Subaru project.
Astronomy with ground-layer adaptive optics systems will push observations with AO to much larger fields of view than previously achieved. Observations such as astrometry of stars in crowded stellar fields and deep searches for very distant star-forming galaxies pushes the systems to the widest possible fields of view. Optical turbulence profiles on Maunakea, Hawaii suggest that such a system could deliver corrected fields of view several tens of arcminutes in size at resolutions close to the free-atmosphere seeing. We present the status of a pathfinder wide field of view ground-layer adaptive optics system on the UH2.2m telescope that will demonstrate key cases and serve as a test bed for systems on larger telescopes and for systems with even larger fields of view.
CRAO is a demonstrator of a compact and low-cost adaptive-optics (AO) with a double-pass lens configuration. Owing
to its compact optical layout compared to conventional reflective AOs, the instrument size can be reduced to only 0.03
square meters. We plan to apply this miniaturization technique into future AOs on a variety of telescopes ranging from 1m-
to 30m-class. CRAO is installed at a Nasmyth focus of the 1.3m Araki telescope at Koyama Astronomical Observatory
in Kyoto Sangyo University. CRAO adopts a closed-loop single-conjugate system with wavelength coverage of 400 -
700 nm and the field of view of 30 arcsec. For low cost, we also employ commercial products on its wavefront sensor
(WFS), deformable mirror (DM), and tip-tilt (TT) stage. CRAO is designed to improve the atmospheric seeing from 2.5
to 0.6arcsec under a typical condition at Koyama Astronomical Observatory with 12x12 subapertures in the WFS, 48
electrodes in the membrane DM and the control bandwidth of 200Hz. In order to examine key issues inherent in refractive
optical system such as chromatic aberration, temperature aberration and ghost images, room and on-sky experiments are
currently underway. CRAO has seen first light in May 2014, and we have confirmed that effects of chromatic aberration and
ghost images induced by its refractive optics are negligible for at least TT correction. In this paper, we present experimental
results as well as the design of optics, opto-mechanics and control system.
We introduce current status of the feasibility study on a wide field of regard (FoR) Multi-Object Adaptive Optics (MOAO) system for TMT (TMT-AGE: TMT-Analyzer for Galaxies in the Early universe). MOAO is a system which realize high spatial-resolution observations of multiple objects scattered in a wide FoR. In this study, we put emphasise on the FoR as wide as 10′ diameter. The wide FoR is crucial to effectively observe very high-redshift galaxies, which have low surface number density. Simulations of an MOAO system with 8 LGSs show close-to-diffraction-limited correction can be achieved within 5′ diameter FoR and moderate AO correction can be achieved within 10′ diameter FoR. We discuss overall system design of the wide FoR MOAO system considering the constraint from the stroke of small-size deformable mirror (DM). We also introduce current status of developments of key components of an MOAO system; high-dynamic range wavefront sensor (WFS) and large-stroke small-size DM, and real time computer (RTC) with fast tomographic reconstruction.
Raven is a Multi-Object Adaptive Optics (MOAO) technical and science demonstrator which had its first light at the Subaru telescope on May 13-14, 2014. Raven was built and tested at the University of Victoria AO Lab before shipping to Hawai`i. Raven includes three open loop wavefront sensors (WFSs), a central laser guide star WFS, and two independent science channels feeding light to the Subaru IRCS spectrograph. Raven supports different kinds of AO correction: SCAO, open-loop GLAO and MOAO. The MOAO mode can use different tomographic reconstructors, such as Learn-and-Apply or a model-based reconstructor. This paper presents the latest results obtained in the lab, which are consistent with simulated performance, as well as preliminary on-sky results, including echelle spectra from IRCS. Ensquared energy obtained on sky in 140mas slit is 17%, 30% and 41% for GLAO, MOAO and SCAO respectively. This result confirms that MOAO can provide a level of correction in between GLAO and SCAO, in any direction of the field of regard, regardless of the science target brightness.
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.
We propose a new high contrast imager for Kyoto 4m segmented telescope called SEICA (Second-generation
Exoplanet Imager with Coronagraphic Adaptive optics), aiming at detection and characterization of selfluminous
gas giants within 10AU around nearby stars. SEICA is aggressively optimized for high performance
at very small inner working angle, 10-6 detection contrast at 0".1 in 1-hour integration. We start the on-sky
commissioning test in 2016 and the science observations in 2017. Since it is the first time to realize the highcontrast
imaging on the segmented telescope, SEICA is an important step toward future high contrast
sciences on Extremely Large Telescopes (ELTs). This paper presents an overall of the SEICA program and
the conceptual design for ultimate performance under given atmospheric conditions.
Thirty Meter Telescope (TMT) will see the first light in 2019. We propose Second-Earth Imager for TMT (SEIT) as a
future instrument of TMT. The central science case of SEIT is direct imaging and characterization of habitable planets
around nearby late-type stars. Focusing on simultaneous spectroscopy of the central star and the planet, SEIT allows us
to remove an impact from the telluric absorption and then reveal the presence of oxygen molecules on the Earth-like
planets.
In order to achieve such a science goal, an extreme AO, a coronagraph, and a post-process technique for achieving high
contrast at the small inner working angle are key components. The combination of a shearing nulling interferometer and
a pupil remapping interferometer is applied to the first SEIT concept. The shearing nulling interferometer suppresses the
diffracted starlight after the extreme AO wavefront correction, and then the pupil remapping interferometer tackles the
speckle noise from starlight. Focusing on a fact that the pupil remapping interferometer has difficulty reconstructing the
wavefront from only the speckle noise, we found an unbalnced nulling technique enhances the performance of the pupil
remapping interferometer. We performed a numerical simulation to validate this concept and found this concept achieves
the 5-sigma detection contrast down to 8x10-8 at 10 mas for 5 hours. Thus, the SEIT concept detects habitable planets
with a radius two times that of the Earth around ten nearby M stars.
We present the current status of the development of the SPICA Coronagraph Instrument (SCI). SPICA is a next-generation
3-meter class infrared telescope, which will be launched in 2022. SCI is high-contrast imaging, spectroscopic
instrument mainly for direct detection and spectroscopy of extra-solar planets in the near-to-mid infrared wavelengths to
characterize their atmospheres, physical parameters and evolutionary scenarios. SCI is now under the international
review process. In this paper, we present a science case of SCI. The main targets of SCI, not only for direct imaging but
also for spectroscopy, are young to matured giant planets. We will also show that some of known exoplanets by ground-based
direct detection are good targets for SCI, and a number of direct detection planets that are suitable for SCI will be
significantly increased in the next decade. Second, a general design of SCI and a key technology including a new high-throughput
binary mask coronagraph, will be presented. Furthermore, we will show that SCI is potentially capable of
achieving 10-6 contrast by a PSF subtraction method, even with a telescope pointing error. This contrast enhancement
will be important to characterize low-mass and cool planets.
The Subaru adaptive optics system (AO188) is a 188-element curvature sensor adaptive optics system that is operated in both natural and laser guide star modes. AO188 is installed at Nasmyth platform of the 8m Subaru telescope as a facility AO system. The laser guide star mode for AO188 has been commissioned and offered for use in science operation since 2011. The performance of AO188 in the laser guide star mode has been well verified from on-sky data obtained with the infrared camera and spectrograph (IRCS). In this paper, we describe the operation procedure and observing efficiency for the laser guide star mode. We also show the result of the on-sky performance evaluation of AO188 in the laser guide star mode and the characterization of the laser guide star, together with the obtained science results.
A wide-field adaptive optics system based on an adaptive secondary mirror (ASM) is one of a future plan for
the next-generation Subaru adaptive optics system. The main application of ASM based AO will be a groundlayer
adaptive optics (GLAO) with field-of-view larger than 10 arc minutes. The high Strehl-ratio of on-source correction by high-order ASM (expected to be about 1000) and the reduction of emissivity are also attractive points. In this paper, we report a preliminary result of simulations for the these applications of ASM to study conceptual design of the next-generation wide-field Subaru adaptive optics.
We are conducting AO development activities in Tohoku university targeting Multi-Object Adaptive Optics (MOAO) system for the next generation ground-based large telescopes. In order to evaluate the accuracy of the tomographic estimation, which is a key of an MOAO system, we assembled a test optical bench to simulate an MOAO system in our optical lab. The system consists with 1) four light sources with single-mode fibers simulating three guide stars and one target object, 2) multiple phase plates simulating atmospheric turbulence structure, and 3) 4 Shack-Hartmann wavefront sensors. Wavefront data from the sensors are reduced with the tomographic algorithm. The evaluation of the accuracy of the tomographic wavefront reconstruction is underway. Additionally, evaluation of an open-loop control of an AO system is underway using an independent module. Once the accuracy of the open-loop control is established, the module will be installed in the tomography test bench and the entire system will be evaluated as an MOAO system. In parallel, we are conducting a development of a large stroke (20μm) Micro Electro Mechanical Systems (MEMS) deformable mirror with large number of elements (<3000). Current status of the development is described.
We report recent development in real-time control system of 188-element Laser Guide Star Adaptive Optics
for Subaru Telescope (Subaru LGSAO-188). The current status is reported, and plans for improvements to
enhance the performance are reported as well. A major item is to invoke the optimum gain control, which is
being implemented on the data handling system and to be attached to the real time control system. We also
explain about other new features on the control system including general response acquisition system as an
expansion of response matrix acquisition system.
In this paper, we present the science path ADC unit (atmospheric dispersion corrector) for the AO188 Adaptive
Optics System of the Subaru Telescope. The AO188 instrument is a curvature-based Adaptive Optics system with
188 subapertures and achieves good correction down to shorter wavelengths like J-band. At these wavelengths, the
atmospheric dispersion within the band becomes significant and thus a correction of the atmospheric dispersion
is essential to reach diffraction-limited image quality. We give an overview of the requirements, the final optical
and mechanical design of the ADC unit, as well as the structure of its control software.
We are developing a laser guide star (LGS) system for the
188-elements Adaptive Optics system (AO188) of the
Subaru telescope. In this paper we describe the results of the performance tests of the LGS system. The beam
that excites sodium atoms at 90 km altitude of the LGS is generated by the following sequence. The source
of the beam is a quasi-CW mode locked sum-frequency generating 589 nm laser. This laser beam propagates
through a diagnostics system for measuring the wavelength and the beam quality. Then it couples into a solidcore
photonic crystal fiber cable for transmitting the beam to a telescope for launching the beam (LLT: Laser
Launching Telescope). The output beam from this fiber cable is collimated by the optics mounted on the
LLT. This collimated beam is expanded by the LLT and launched into the sky. We executed several engineering
observations of the LGS system from 2009 for confirming the performance of all the components in this sequence.
We also report the quality of the LGS.
We report recent development in real time control system of Subaru adaptive optics system. The main topic is
modification of the real time control system for laser guide star operation. The primary change is appending lower order
wave-front sensor. And also, an auxiliary tip-tilt and focus control are appended before higher order waver-front sensor
to absorb the perturbation of the laser beam and height of sodium layer. Our implementations using the control gain
matrix are introduced thoroughly from the basis of the system design and down to the details. Also, other new function
and prospects in the near future will be presented for the cascaded average monitor and the time domain over sampling.
Subaru adaptive optics system (AO188) is an 188-elements curvature sensor adaptive optics system that is operated
in both natural and laser guide star modes. AO188 was installed at Nasmyth platform of the Subaru
telescope and it has been successfully operating in the natural guide star mode since October 2008. The performance
of AO188 in the natural guide star mode has been well verified from on-sky data obtained with the infrared
camera and spectrograph (IRCS). Under normal seeing condition, AO188 achieves K-band Strehl ratio between
60% and 70% using R = 9.0 magnitude natural guide stars and it works well with faint guide stars down to
R = 16.5 magnitude. We measured the FWHM and Strehl ratio of stellar images in globular clusters and found
that the isoplanatic angle is approximately 30 arcsec. In this paper, we describe an overview of the operation
procedure for AO188, as well as its performance such as angular resolution, Strehl ration, and sensitivity gain
for detecting faint objects.
We are commissioning the Laser Guide Star Adaptive Optics (LGS/AO188) system for Subaru Telescope at
Hawaii, Mauna Kea. This system utilizes a combination of an
all-solid-state mode-locked sum-frequency generation
(SFG) laser (1.7GHz-bandwidth, 0.7ns-pulse width) as a light source and single-mode optical fiber for beam
transference. However, optical fibers induce nonlinear scattering effects, such as stimulated Raman scattering
(SRS) and stimulated Brillouin scattering (SBS), beyond certain threshold levels in high-power lasers. We measured
the laser transmission characteristics of a photonic crystal fiber (PCF) whose mode field diameter (MFD)
was 11 μ m, and a step index fiber (SIF) cable whose MFD was 4.2 μ m to evaluate the threshold levels for
non-linear effects. We observed SRS in the 200-m-long SIF when we input 1.3W. The material losses of them
were 10db/km and 6.4dB/km, respectively. However, SRS and SBS were not induced in the 200-m-long PCF,
even for an input power of 5.3W. As a result, we estimated the threshold of SRS to be 33W for the 35-m-long
PCF designed for the Subaru LGSAO system.
Other than SRS and SBS, we found self phase modulation (SPM) in our PCF. SPM makes the spectrum
of the laser beam broaden and it causes less efficiency of generating bright LGS. We measured width of the
spectrum by spectrum analyzer. As the result, we found it was 9.1GHz of full width half maximum (FWHM)
in comparison with the original FWHM of our laser spectrum, 2.1GHz. This shows 70% of the laser energy for
brightening the LGS was lost.
We also measured the brightness of the LGS and evaluated its relationship with wavelength of the laser.
The LGS's brightness showed a peculiar tendency that did not be extinguish even though the wavelength has
varied about 2pm. The tendency was not shown with the experiment using sodium gas cell. Therefore, it may
be concerned the environment of the sodium layer in the mesosphere.
The Subaru laser guide star adaptive optics system (AO188) was installed at the Nasmyth focus of the Subaru
Telescope on October 2006 and it is in operation with the natural guide star (NGS) mode. The operation of
the laser guide star (LGS) mode started on January 2010. A visible low-order wavefront sensor (LOWFS) was
built to measure tip-tilt and defocus terms of wavefront by using a single NGS within a 2.7 arcmin diameter field
when an LGS is used for high-order wavefront sensing with the 188-element curvature based wavefront sensor.
This LOWFS is a 2 × 2 sub-aperture Shack-Hartmann sensor with 16 photon-counting avalanche photodiode
(APD) modules. A 4×4-element lenslet array is located after the 2 × 2 sub-aperture Shack-Hartmann lenslet
array and it is coupled with the APD modules through optical fibers. The field of view of the LOWFS is 4 arcsec
in diameter. It has own guide star acquisition unit, acquisition and pupil cameras, and atmospheric dispersion
corrector. We describe the design, construction, and integration of this low-order wavefront sensor.
KEYWORDS: Telescopes, Mirrors, Adaptive optics, Telecommunications, Secondary tip-tilt mirrors, Infrared telescopes, Digital signal processing, Control systems, Infrared radiation, Data conversion
A tip/tilt off-load function from AO188 deformable mirror mount to Subaru telescope infrared secondary mirror
has been implemented and tested. The function is effective to reduce the influence of strong background pattern
at thermal infrared wavelengths. We describe the function and report the test results in this paper.
We started adaptive optics (AO) development activities in Tohoku university targeting Multi-Object Adaptive
Optics (MOAO) system for the next generation ground-based large telescopes. In order to realize an MOAO
system, we are currently conducting two R&Ds. First one is a development of a large stroke (20μm) Micro Electro
Mechanical Systems (MEMS) deformable mirror with large number of elements (>3000) which is necessary to
achieve mild Strehl Ratio in an AO systems for 30m class telescopes. Based on our original design to achieve
the requirements, prototyping of the device is currently underway using the MEMS development facility in our
university. Second one is a consideration of tomographic algorithm for the wavefront estimation required for
an MOAO system. The algorithm will be tested on a test bench simulating multiple guide stars and wavefront
sensors. Concept design of the test bench is shown. MEMS-DM and MOAO testbed developments will be
concluded by 2013.
The current status of commissioning and recent results in performance of Subaru laser guide star adaptive optics
system is presented. After the first light using natural guide stars with limited configuration of the system in
October 2006, we concentrated to complete a final configuration for a natural guide star to serve AO188 to an
open use observation. On sky test with full configurations using natural guide star started in August 2008, and
opened to a public one month later. We continuously achieved around 0.6 to 0.7 of Strehl ratio at K band using
a bright guide star around 9th to 10th magnitude in R band. We found an unexpectedly large wavefront error
in our laser launching telescope. The modification to fix this large wavefront error was made and we resumed
the characterization of a laser guide star in February 2009. Finally we obtained a round-shaped laser guide star,
whose image size is about 1.2 to 1.6 arcsec under the typical seeing condition. We are in the final phase of
commissioning. A diffraction limited image by our AO system using a laser guide star will be obtained in the
end of 2010. An open use observation with laser guide star system will start in the middle of 2011.
The image derotator is an integral part of the AO188 System at Subaru Telescope. In this article software control,
characterization and integration issues of the image derotator for AO188 System presented. Physical limitations of the
current hardware reviewed. Image derotator synchronization, tracking accuracy, and problem solving strategies to
achieve requirements presented. It's use in different observation modes for various instruments and interaction with the
telescope control system provides status and control functionality. We describe available observation modes along with
integration issues. Technical solutions with results of the image derotator performance presented. Further improvements
and control software for on-sky observations discussed based on the results obtained during engineering observations.
An overview of the requirements, the final control method, and the structure of its control software is shown. Control
limitations and accepted solutions that might be useful for development of other instrument's image derotators presented.
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
AO188+HiCIAO.
In the context of instrumentation for Extremely Large Telescopes (ELTs), an Integral Field Spectrographs
(IFSs), fed with a Multi-Object Adaptive Optics (MOAO) system, has many scientific and technical advantages.
Integrated with an ELT, a MOAO system will allow the simultaneous observation of up to 20 targets in a several
arc-minute field-of-view, each target being viewed with unprecedented sensitivity and resolution. However,
before building a MOAO instrument for an ELT, several critical issues, such as open-loop control and calibration,
must be solved. The Adaptive Optics Laboratory of the University of Victoria, in collaboration with the Herzberg
Institute of Astrophysics, the Subaru telescope and two industrial partners, is starting the construction of a
MOAO pathfinder, called Raven. The goal of Raven is two-fold: first, Raven has to demonstrate that MOAO
technical challenges can be solved and implemented reliably for routine on-sky observations. Secondly, Raven
must demonstrate that reliable science can be delivered with multiplexed AO systems. In order to achieve these
goals, the Raven science channels will be coupled to the Subaru's spectrograph (IRCS) on the infrared Nasmyth
platform. This paper will present the status of the project, including the conceptual instrument design and a
discussion of the science program.
A method to characterize the vibrating shape of a bimorph deformable mirror by measurement using a laser displacement sensor is presented. The displacement of the deformable mirror surface at a point is recorded as a frequency response function. The surface profile is synthesized from the response functions obtained at multiple points on a deformable mirror by postprocessing. The method has a wide frequency range and high-frequency resolution, suitable to investigate the resonance behavior of a deformable mirror. Although the spatial resolution is low compared with an interferometer, it is sufficient to identify low-spatial-order shapes at resonance frequencies. The accuracy of the displacement measurement is estimated to be comparable with interferometric data.
We have developed a dichroic beam splitter for the Subaru AO188, which reflects optical light (0.4-0.9 &mgr;m) for
wavefront sensing and transmits near-infrared light (0.93-5.2 &mgr;m) for science observations. The beam splitter
is made of 145mm × 200mm calcium fluoride substrate coated by fluoride and metal chalcogen compound
multilayer, which should be a best way to realize high transmittance over wide wavelength range in the near
infrared. However, since typical fluoride soft coating is less resistant to the moisture in the air, the fluoride
coating become damaged as we use on the AO188 optical bench which is placed in the room temperature
condition. We have performed several accelerated endurance tests of the beam splitter under high-humidity
condition by changing the design of the coatings, and found an optimal solution with an oxide protection layer
which prevents the damage of the dichroic coating and keeps high transmittance at near-infrared wavelength. In
this paper, we report the results of the endurance tests and the performance of our dichroic beam splitter.
The Subaru laser guide star adaptive optics (AO) system was installed at the Nasmyth focus of the Subaru
Telescope, and had the first light with natural guide star on October 2006. The AO system has a 188-element
curvature based wavefront sensor 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' diameter
field. The AO system 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 cone
effect for the LGS beam. We describe the design, construction, and integration of the curvature wavefront sensor
and calibration source unit.
Actual measurement of vibrating shape of a bimorph deformable mirror is presented to discuss the characteristics
of resonance. Understanding the vibration properties of a bimorph deformable mirror is a key issue to overcome
resonance problem, a major drawback of this type of deformable mirror, and to make full use of its advantages.
Two-dimensional vibrating shape of the deformable mirror surface, not only at a point, is essential to figure out
the resonance behavior. The results are informative for improvement of mechanical design or control software.
The current status and recent results, since last SPIE conference at Orlando in 2006, for the laser guide star adaptive optics system for Subaru Telescope is presented. We had a first light using natural guide star and succeed to launch the sodium laser beam in October 2006. The achieved Strehl ratio on the 10th magnitude star was around 0.5 at K band. We confirmed that the full-width-half-maximum of the stellar point spread function is smaller than 0.1 arcsec even at the 0.9 micrometer wavelehgth. The size of the artificial guide star by the laser beam tuned at the wavelength of 589 nm was estimated to be 10 arcsec. The obtained blurred artificial guide star is caused by the wavefront error on the laser launching telescope. After the first light and first launch, we found that we need to modify and to fix the components, which are temporarily finished. Also components, which were postponed to fabricate after the first light, are required to build newly. All components used by the natural guide star adaptive optics system are finalized recently and we are ready to go on the sky. Next engineering observation is scheduled in August, 2008.
We developed a high power and high beam quality 589 nm coherent light source by sum-frequency generation in order to utilize it as a laser guide star at the Subaru telescope. The sum-frequency generation is a nonlinear frequency conversion in which two mode-locked Nd:YAG lasers oscillating at 1064 and 1319 nm mix in a nonlinear crystal to generate a wave at the sum frequency. We achieved the qualities required for the laser guide star. The power of laser is reached to 4.5 W mixing 15.65 W at 1064 nm and 4.99 W at 1319 nm when the wavelength is adjusted to 589.159 nm. The wavelength is controllable in accuracy of 0.1 pm from 589.060 and 589.170 nm. The stability of the power holds within 1.3% during seven hours operation. The transverse mode of the beam is the TEM00 and M2 of the beam is smaller than 1.2. We achieved these qualities by the following technical sources; (1) simple construction of the oscillator for high beam quality, (2) synchronization of mode-locked pulses at 1064 and 1319 nm by the control of phase difference between two radio frequencies fed to acousto-optic mode lockers, (3) precise tunability of wavelength and spectral band width, and (4) proper selection of nonlinear optical crystal. We report in this paper how we built up each technical source and how we combined those.
We are developing Laser Guide Star Adaptive Optics (LGSAO) system for Subaru Telescope at Hawaii, Mauna Kea. We achieved an all-solid-state 589.159 nm laser in sum-frequency generation. Output power at 589.159 nm reached 4W in quasi-continuous-wave operation. To relay the laser beam from laser location to laser launching telescope, we used an optical fiber because the optical fiber relay is more flexible and easier than mirror train. However, nonlinear scattering effect, especially stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), will happen when the inputted laser power increases, i.e., intensity at the fiber core exceed each threshold. In order to raise the threshold levels of each nonlinear scattering, we adopt photonic crystal fiber (PCF). Because the PCF can be made larger core than usual step index fiber (SIF), one can reduce the intensity in the core. We inputted the high power laser into the PCF whose mode field diameter (MFD) is 14 μm and the SIF whose MFD is 5 μm, and measured the transmission characteristics of them. In the case of the SIF, the SRS was happen when we inputted 2 W. On the other hand, the SRS and the SBS were not induced in the PCF even for an input power of 4 W. We also investigated polarization of the laser beam transmitting through the PCF. Because of the fact that the backscattering efficiency of exciting the sodium layer with a narrowband laser is dependent on the polarization state of the incident beam, we tried to control the polarization of the laser beam transmitted the PCF. We constructed the system which can control the polarization of input laser and measure the output polarization. The PCF showed to be able to assume as a double refraction optical device, and we found that the output polarization is controllable by injecting beam with appropriate polarization through the PCF. However, the Laser Guide Star made by the beam passed through the PCF had same brightness as the state of the polarization.
The purpose of this paper is to report on the current status of developing the new laser guide star (LGS) facility for the Subaru LGS adaptive optics (AO) system. Since two major R&D items, the 4W-class sum-frequency generating laser1 and the large-area-core photonic crystal fiber2, have been successfully cleared, we are almost ready to install the LGS facility to the Subaru Telescope. Also we report the result for LGS generation in Japan.
The performance of a deformable mirror with 188 electrodes is reported in this paper. The deformable mirror has been manufactured by CILAS for a new adaptive optics system at Subaru Telescope equipped with laser-guide-star. The type of deformable mirror is bimorph PZT with the blank diameter of 130 mm (beam size 90 mm).
The laser guide star adaptive optics (AO188) system for Subaru Telescope is presented. The system will be installed at the IR Nasmyth platform of Subaru 8 m telescope, 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 and 188 element bimorph mirror. The laser guide star system has a 4.5 W solid state sum-frequency laser on the Nasmyth platform. The laser launching telescope with 50 cm aperture will be installed at behind the secondary mirror. The laser beam will be transferred to the laser launching telescope using photonic crystal single mode fiber cable. The instrument with the AO system is IRCS, infrared camera and spectrograph which has been used for Cassegrain AO system and new instrument, HiCIAO, high dynamic range infrared camera for exsolar planet detection. The first light of the AO system is planned in 2006.
Subaru AO-188 is a curvature adaptive optics system with 188 elements. It has been developed by NAOJ (National Astronomical Observatory of Japan) in recent years, as the upgrade from the existing 36-element AO system currently in operation at Subaru telescope. In this upgrade, the control scheme is also changed from zonal control to modal control. This paper presents development and implementation of the modal optimization system for this new AO-188. Also, we will introduce some special features and attempt in our implementation, such as consideration of resonance of deformable mirror at the lower order modes, and extension of the scheme for the optimization of the magnitude of membrane mirror in wave front sensor. Those are simple but shall be useful enhancement for the better performance to the conservative configuration with conventional modal control, and possibly useful in other extended operation modes or control schemes recently in research and development as well.
KEYWORDS: Adaptive optics, Telescopes, Stars, Mirrors, Wavefront sensors, K band, Laser systems engineering, Wavefronts, Deformable mirrors, Control systems
The performance of the Cassegrain Adaptive Optics (AO) system of the 8.2 m Subaru Telescope is reported. The system is based on a curvature wavefront sensor with 36 photon-counting avalanche photodiode modules and a bimorph wavefront correcting deformable mirror with 36 driving electrodes. This AO system has been in service since 2002 April for two open-use instruments, an infrared camera and spectrograph (IRCS) and a coronagraph imager with adaptive optics (CIAO). The Strehl ratio in the K-band is around 0.3 when a bright guide star is available under 0".4 seeing condition. High sensitivity of the wavefront sensor allows significant improvement in the image quality, even for faint guide stars down to R=18 mag. The design of the new Nasmyth Adaptive Optics system with 188 control elements under construction is described. This new system with fivefold increase in the number of control elements will provide twice higher Strehl ratio of 0.7. To increase the sky coverage for this new system, a power laser system to produce an artificail guide star in the upper atmosphere is also under construction. The AO system with laser guide capability enables the coverage up to 80% of the entire sky and offers diffraction limited observation for almost any target in the sky. An all solid-state 4W laser to generate the sodium D line emission by summing the two YAG laser frequencies is under development. The generated laser beam is tranmitted through a photonic crystal fiber to the laser launching telescope attached at the backside of the secondary mirror. Expected performance of this laser guide Nasmyth AO system is shown.
Subaru adaptive optics is a system of curvature wavefront sensor
coupled with bimorph type deformable mirror. The number of element for each component is 36. The system is attached on the Cassegrain focus of the telescope. The open-use observation of the AO system has been started from April of 2002. In this paper, we report experiences obtained from Subaru adaptive optics system for two years of open-use operation. These experiences will be of value for development of
future AO systems.
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.
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.
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.
Observation of stellar speckle-patterns is a useful optical remote-sensing technique of terrestrial atmospheric turbulence. The wind velocity (magnitude and direction) at the turbulence layer is determined by movement of the speckle patterns. The altitude and refractive index structure constant of the turbulence layer are also deduced from the peak height and width of speckle-pattern correlation-peak. A new simple system, which consists of an image intensified CCD and a photomultiplier tube attached on a 50 cm telescope, has been developed for observing the speckle-patterns. The system is utilized to continuously monitor the parameters of atmospheric turbulence ranging from 2 km to 20 km. Results of the monitoring measurement over a year are presented.
Prototype laser guide star system for Subaru telescope has been developed at Communications Research Laboratory (CRL). The laser system comprises two commercially available lasers: a modified continuous wave (CW) dye laser and a 10 W all-solid CW laser of 532 nm wavelength for pumping the dye laser. The natural guide star adaptive optics system for Subaru telescope on Cassegrain focus will be upgraded to a laser guide star adaptive optics system using this laser system. The experiment of transmitting laser beam to the sodium layer is performed at CRL using a 1.5 m telescope. The laser beam is emitted from a 20 cm telescope mounted next to the 1.5 m telescope. A laser guide star is observed by a cooled CCD camera, which is equipped on the Nasmyth platform. We report the preliminary results of the experiment of observing a sodium laser guide star.
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.
The infrared instrumentation plan for the Subaru telescope is described. Four approved infrared instruments and one test observation system are now in the construction phase. They are coronagraph imager using adaptive optics (CIAO), cooled mid- infrared camera and spectrograph (COMICS), infrared camera and spectrograph (IRCS), OH-airglow suppressor spectrograph (OHS) and mid-infrared test observation system (MIRTOS). Their performance goals and construction schedules are summarized. The plan for procurement and evaluation of infrared arrays required by these instruments is briefly described.
A specially designed faint object spectrograph in the near-IR region from 1 to 2 micrometers is proposed for the Japanese National Large Telescope: SUBARU. The proposed instrument called OHS for SUBARU is kind of a pre-optics system capable of eliminating most of intense OH airglow emission lines from the incident beam in the J- and H-passbands. The detectivity for objects in the faintest end is supposedly enhanced with this spectroscopic filter system by removing nearly 95% of the natural sky background: the non-thermal night airglow emission. The sensitivity gain in terms of limiting magnitude in these wavelength bands is expected to be 1 to 1.5 mag, depending on the modes of observations. The expected performance of the prototype OHS when attached to SUBARU will also be presented.
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