Okayama Astrophysical Observatory Wide Field Camera is a near-infrared (0.9-2.5 μm) survey telescope, built as a renewal of 0.91 m classical Cassegrain telescope. The optics is composed of forward Cassegrain and quasi Schmidt, which yield an effective image circle of Φ51 mm. A HAWAII-1 PACE detector is placed at the focal plane, which gives a field of view of 0.48 deg.×0.48 deg. with image scale of 1.67 arcsec/pix. OAOWFC is used to monitor the Galactic plane for variability and search for EM counterpart of gravitational wave sources.
We have prepared remote observing environment for the 188 cm telescope at Okayama Astrophysical Observatory. A KVM-over-IP and a VPN gateway are employed as core devices, which offer reliable, secure and fast link between on site and remote sites. We have confirmed the KVM-over-IP has ideal characteristics for serving the remote observing environment; the use is simple for both users and maintainer; access from any platform is available; multiple and simultaneous access is possible; and maintenance load is small. We also demonstrated that the degradation of observing efficiency specific to the remote observing is negligibly small. The remote observing environment has fully opened since the semester 2016A, about 30% of the total observing time in the last semester was occupied by remote observing.
We have built a control system for a mini survey facility dedicated to photometric monitoring of nearby bright (K<5) stars in the near-infrared region. The facility comprises a 4-m-diameter rotating dome and a small (30-mm aperture) wide-field (5 × 5 sq. deg. field of view) infrared (1.0–2.5 microns) camera on an equatorial fork mount, as well as power sources and other associated equipment. All the components other than the camera are controlled by microcomputerbased I/O boards that were developed in-house and are in many of the open-use instruments in our observatory. We present the specifications and configuration of the facility hardware, as well as the structure of its control software.
We report a development of a multicolor simultaneous camera for the 188-cm telescope at Okayama Astrophysical Observatory in Japan. The instrument, named MuSCAT (Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets), has a capability of three-color simultaneous imaging in optical wavelengths where CCDs are sensitive. MuSCAT is equipped with three 1024 × 1024 pixel CCDs which can be controlled independently. The three CCDs detect lights in g2′ (400 to 550 nm), r2′ (550 to 700 nm), and zs,2 (820 to 920 nm) bands using Astrodon Photometrics Generation 2 Sloan filters. The field of view of MuSCAT is 6.1×6.1 arc min2 with the pixel scale of 0.358 arc sec/pixel. The principal purpose of MuSCAT is to perform high-precision multicolor transit photometry. For this purpose, MuSCAT has the capability of self-autoguiding which enables it to fix the positions of stellar images within ∼1 pixel. We demonstrate relative photometric precisions of 0.101%, 0.074%, and 0.076% in g2′, r2′, and zs,2 bands, respectively, for GJ 436 (magnitudes in g′=11.81, r′=10.08, and z′=8.66) with 30-s exposures. The achieved precisions meet our objective, and the instrument is ready for operation.
Okayama Astrophysical Observatory Wide Field Camera: OAOWFC is a near-infrared (0.9-2.5 μm) survey telescope, whose aperture is 0.91m. It works at Y, J, H, and Ks bands. The optics are consisted of forward Cassegrain and quasi Schmidt which yield the image circle of Φ 52 mm or Φ 1.3 deg at the focal plane. The overall F-ratio is F/2.51 which is one of the fastest among near infrared imagers in the world. A HAWAII-1 detector array placed at the focal plane cuts the central 0.48 deg. x 0.48 deg. with a pixel scale of 1.67 arcsec/pix. It will be used to survey the Galactic plane for variability and search for transients such as Gamma-ray burst afterglows optical counterpart of gravitational wave sources.
We are now investigating and studying a small satellite mission HiZ-GUNDAM for future observation of gamma-ray bursts (GRBs). The mission concept is to probe “the end of dark ages and the dawn of formation of astronomical objects”, i.e. the physical condition of early universe beyond the redshift z > 7. We will consider two kinds of mission payloads, (1) wide field X-ray imaging detectors for GRB discovery, and (2) a near infrared telescope with 30 cm in diameter to select the high-z GRB candidates effectively. In this paper, we explain some requirements to promote the GRB cosmology based on the past observations, and also introduce the mission concept of HiZ-GUNDAM and basic development of X-ray imaging detectors.
ISLE is a near-infrared imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at
Okayama Astrophysical Observatory. It is upgraded instrument with a new detector, HAWAII-1 HgCdTe array
and new optics. ISLE provides imaging capabilities which covers 4.2 × 4.2 arcmin2 field-of-view at 0.25 arc-sec/
pixel and long-slit (4 arcmin) spectroscopic capabilities at λ/Δλ = 1000 - 4000 using reflection gratings.
The noise performance of the detector is excellent. The read noise of 2.5 electrons with 25 Fowler pairs has
been achieved, that is one of the world's lowest level among the instruments which use HAWAII-1 array as the
detector. We discuss the technical performance of ISLE and examine the upgrade effectiveness.
ISLE is a near-infrared (1.0-2.5μm) imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at Okayama Astrophysical Observatory. The detector is a HAWAII 1024 × 1024 HgCdTe Array, which covers 4.2 × 4.2 arcmin2 field of view with a pixel scale of 0.25 arcsec/pixel. ISLE also provides medium (R=300 - 4800) resolution long-slit (4 arcmin long spectroscopic capabilities using reflection gratings. A dedicated front-end electronics for the detector achieved a readout noise of 8 electrons by the conventional Fowler sampling, and a operation scheme that combined with a number of discarded readout greatly suppressed the reset anomaly. The measured limiting magnitudes were J=18.6 and K=17.7 (imaging of point sources at S/N=10 for 10 min.
TUFPAC (Tohoku University Focal Plane Array Controller) is an array control system originally designed for flexible control and efficient data acquisition of 2048 x 2048 HgCdTe (HAWAII-2) array. A personal computer operated by Linux OS controls mosaic HAWAII-2s with commercially available DSP boards installed on the PCI bus. Triggered by PC, DSP sends clock data to front-end electronics, which is isolated from the DSP board by photo-couplers. Front-end electronics supply powers, biases and clock signals to HAWAII2. Pixel data are read from four outputs of each HAWAII2 simultaneously by way of four channel preamps and ADCs. Pixel data converted to 16 bit digital data are stored in the frame memory on the DSP board.
Data are processed in the memory when necessary. PC receives the frame data and stores it in the hard disk of PC in FITS format. A set of the DSP board and front-end electronics is responsible for controlling each HAWAII-2. One PC can operate eight mosaic arrays at most. TUFPAC is applicable to the control of CCDs with minor changes of front-end electronics.
We developed two DIMMs (Differential Image Motion Monitor) for simultaneous seeing measurements at multiple sites. Simultaneous seeing measurements enable us to distinguish temporal variation and site to site variation of seeing, and clarify which site has better seeing. We set the aperture separation of the DIMM at 50 cm for accurate measurements under good (~0.3 arcsec) seeing conditions for Mauna Kea. Our system can also be tuned for moderate to bad seeing conditions by changing the effective focal length of the optics. The frame of our DIMM device is made of CFRP in order to avoid deformation with temperature change and to reduce its weight. We will present the details of our DIMM system and some results of simultaneous seeing measurements at Mauna Kea, Hawaii.
We use the HAWAII-2 (2048 × 2048 HgCdTe) FPAs in MOIRCS (Multi-Object Infra-Red Camera and Spectrograph) for the astronomical use on the Subaru telescope. MOIRCS, which is currently being constructed by Tohoku University and the National Astronomical Observatory of Japan, is one of the second generation instruments for Subaru. It will provide the wide-field imaging mode (4 × 7 arcmin2) and the multi-object spectroscopy mode with the wavelength range of 0.8 to 2.5 μm.
To achieve the large field of view with the high spatial resolution, we use two large-format near-infrared arrays, HAWAII-2. We have developed an infrared array control system specially designed for flexible control and efficient data acquisition of the HAWAII-2 arrays. The array control system, TUFPAC, consists of a personal computer operated by LINUX OS and commercially available DSP boards. By using TUFPAC and the cryostat for array tests, we have made tests of the HAWAII-2 array. In this paper, we report on our array control system and the results of various performance tests for the HAWAII-2 array.
We developed the telescope control software for the 188cm telescope of Okayama Astrophysical Observatory (OAO) based on Java technology. Basically, the software consists of two processes running on separate Java virtual machines; one of which is the “Command Dispatcher (CD)” and the other is the “User Interface (UI)”. Among the two, CD is the main engine/server of the telescope control, whereas UI is just a client. The “standard” UI we provide is a graphical user interface written in Java/Swing. CD communicates with the local control units (LCUs) of the telescope through RS232C. CD is a Java multi-thread program, in which a number of threads run simultaneously. The threads running in CD are the follows: UNIX socket servers for external communications, socket opener for on-demand open/close of a socket port, socket client manager, auto-guider and dome watcher, internal command dispatcher, status manager, status collector, RS232C writer and reader, logger, and control units. The above “control units” are software models (“objects”) of the telescope system. We introduced four control units- “Telescope”, “Dome”, “Weather-Monitor”, and “Pointing”- for telescope control. The first three units are simple software models of the real-worlds devices. The last one, “Pointing”, is a unit which abstracts pointing procedure of the telescope. CD and UI communicate with each other using UNIX socket. The command protocol of this communication is fairly simple, and observation instruments, auto guider, or additional UI for remote observation are also able to communicate with CD through socket using this protocol. CD opens and closes socket ports for communication on demand according to the request of client process (UI, instruments etc.), so that any clients can be connected to CD dynamically.
To built a 3K X 3K pixel near-IR FPA, we have made a package and a multi-chip module for Mitsubishi 1040 X 1040 PtSi CSD, which is one of the largest SWIR FPAs. Mosaicing demands smallest gaps between chips to achieve a large fill-factor and controlled flatness to fit a camera focal plane. The package of 52-pin half-pitch PGA has been designed to be smaller than the bear chip. After the chip is glued on the package and wire-bonded, nine packages with the chip are arrayed in three by three on a multi chip module (MCM) of 6 cm X 6 cm area. The fill-factor of the imaging area is 89 percent. The package and MCM are made of AlN ceramic of high thermal conductivity. MCM, therefore, plays a role of an efficient heat sink. The surface of the package, with which the chip is in contact, has been polished with accurate flatness as well as MCM. As the result, the height of nine chips built on MCM are uniform within approximately 20 micrometers in 6 cm X 6 cm area. The mosaic array will be equipped in a near-IR camera for astronomical observations of a wide field view.
We present the performance of the 1040 by 1040 PtSi CSD manufactured by Mitsubishi Electric Co. for an application of astronomical imaging. The sensor was evaluated both in laboratory and in real observing conditions. The results of noise, quantum efficiency, linearity, dark current and photometric accuracy are presented.
A new infrared camera equipped with a 1040 by 1040 PtSi CSD array is in operation as a common-use instrument at Kiso Observatory of the University of Tokyo. The camera attached to the prime focus (F/3.1) of the 105 cm Schmidt telescope gives a field of view of 18'.4 by 18'.4 with a spatial resolution f 1'.1 per pixel. The image resolution, detection limit, and other performances in an astronomical application are presented. Based on the observations of nearby galaxies and Galactic objects, we demonstrate that the camera is very powerful for wide-field imaging in astronomy.
We have constructed a near-infrared camera with a 1040 by 1040 PtSi CSD array for astronomical use. The camera is attached to the prime focus (f/3.1) of the 105 cm Schmidt telescope at Kiso observatory. The field of view is 18.4 by 18.4 arcmin2 and the spatial resolution is 1.06 by 1.06 arcsec2/pixel. The camera can be used mainly in J ((lambda) eff equals 1.25 micrometer), H (1.65 micrometer), and K' (2.15 micrometer) bands. Since thermal emissions from the atmosphere and room-temperature bodies are main background noise sources in the near-infrared, we designed a cold baffle inside the camera to minimize the effect of the thermal radiation from the telescope. Both the charge transfer efficiency and the dark current of PtSi arrays are sensitive to the array temperature. Therefore we carefully control the temperature at 60 +/- 0.05 K by using a refrigerator and a temperature controller. The readout noise was reduced to 70 e by adopting a correlated multiple sampling technique. The array response was linear within 0.7% accuracy below 25% of the full well capacity (< 4.0 X 105 e).