The Korea Microlensing Telescope Network (KMTNet) is a network of three new 1.6-m, wide-field telescopes spread over three different sites in Chile, South Africa and Australia. Each telescope is equipped with a four square degree wide-field CCD camera, making the KMTNet an ideal facility for discovering and monitoring early supernovae and other rapidly evolving optical transients by providing 24-hour continuous sky coverage. We describe our inaugurating program of observing supernovae and optical transients using about 20% of the KMTNet time in 2015−2019. Our early results include detection of infant supernovae, novae and peculiar transients as well as numerous variable stars and low surface brightness objects such as dwarf galaxies.
We present the design, assembly, alignment, and verification process of the wide field corrector for the Korea Microlensing Telescope Network (KMTNet) 1.6 meter optical telescope. The optical configuration of the KMTNet telescope is prime focus, having a wide field corrector and the CCD camera on the topside of Optical Tube Assembly (OTA). The corrector is made of four lenses designed to have all spherical surfaces, being the largest one of 552 mm physical diameter. Combining with a purely parabolic primary mirror, this optical design makes easier to fabricate, to align, and to test the wide field optics. The centering process of the optics in the lens cell was performed on a precision rotary table using an indicator. After the centering, we mounted three large and heavy lenses on each cell by injecting the continuous Room Temperature Vulcanizing (RTV) silicon rubber bonding via a syringe.
Korea Astronomy and Space Science Institute have been developing the Korea Microlensing Telescope Network aka KMTNet consists of three identical 1.6-m wide-field optical telescopes. Each telescope covers 2 deg by 2 deg FOV with an 18k by 18k mosaic CCD camera to discover Earth mass extrasolar planets using a microlensing method. A predefined 4 deg by 4 deg Bulge area will be monitored for 24-hours with the help of almost equally located three southern observatories: Cerro Tololo Inter-American Observatory in Chile, South African Astronomical Observatory in South Africa and Siding-Spring Observatory in Australia. One of the required photometric performances of the system to accomplish its scientific goal is to secure 1% of magnitude uncertainty in the range of 13 < I < 18 at the heavily crowded Galactic bulge area. To minimize the blending effect and to maximize the photometric accuracy in the photometric process, we use the difference image analysis method for a data reduction pipeline that requires precise alignment and constant point spread function profile in the observed images. In this paper we present the test observation results and verify the observational performance of the first telescope installed at CTIO. From the test observation we obtained a pointing accuracy of 8.5 arcsec RMS, an open loop tracking accuracy of 0.166 arcsec for two minutes without autoguiding, a delivered image quality of 0.86, 0.86, 0.93, 0.98 arcsec in I, R, V, B–bands, and a photometric error of 1% for the stars with 17.0 magnitude in I-band using a prescience CCD camera which has a quantum efficiency of 30%.
The Immersion Grating Infrared Spectrometer (IGRINS) is a compact high-resolution near-infrared cross-dispersed
spectrograph whose primary disperser is a silicon immersion grating. IGRINS covers the entire portion of the
wavelength range between 1.45 and 2.45μm that is accessible from the ground and does so in a single exposure with a
resolving power of 40,000. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for
separate spectrograph arms covering the H and K bands. On the 2.7m Harlan J. Smith telescope at the McDonald
Observatory, the slit size is 1ʺ x 15ʺ and the plate scale is 0.27ʺ pixel. The spectrograph employs two 2048 x 2048
pixel Teledyne Scientific and Imaging HAWAII-2RG detectors with SIDECAR ASIC cryogenic controllers. The
instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly
identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows
the spectrograph collimated beam size to be only 25mm, which permits a moderately sized (0.96m x 0.6m x 0.38m)
rectangular cryostat to contain the entire spectrograph. The fabrication and assembly of the optical and mechanical
components were completed in 2013. We describe the major design characteristics of the instrument including the
system requirements and the technical strategy to meet them. We also present early performance test results obtained
from the commissioning runs at the McDonald Observatory.
IGRINS, the Immersion GRating INfrared Spectrometer, is a near-infrared wide-band high-resolution spectrograph
jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS
employs three HAWAII-2RG focal plane array (FPA) detectors. The mechanical mounts for these detectors and for the
final (field-flattening) lens in the optical train serve a critical function in the overall instrument design: Optically, they
permit the only positional compensation in the otherwise “build to print” design. Thermally, they permit setting and
control of the detector operating temperature independently of the cryostat bench. We present the design and fabrication
of the mechanical mount as a single module. The detector mount includes the array housing, housing for the SIDECAR
ASIC, a field flattener lens holder, and a support base. The detector and ASIC housing will be kept at 65 K and the
support base at 130 K. G10 supports thermally isolate the detector and ASIC housing from the support base. The field
flattening lens holder attaches directly to the FPA array housing and holds the lens with a six-point kinematic mount.
Fine adjustment features permit changes in axial position and in yaw and pitch angles. We optimized the structural
stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis.
Based on the computer simulation, the designed detector mount meets the optical and thermal requirements very well.
The KMTNet telescope Project, sponsored by The Korea Astronomy and Space Science Institute (KASI), is fabricating
three wide-field equatorial mount telescopes of 1.6 meter aperture to conduct continuous observations of the Galactic
bulge region to search for extra-solar planets. Southern latitude sites secured for these telescopes are SAAO (South
Africa), CTIO (Chile), and SSO (Australia). A prime-focus configuration, along with a four-lens corrector achieves the
2.8 degree diagonal FOV. The basic mechanical design utilizes a scaled-up version of the successful 2MASS Telescopes
built by the authors in the late 1990's. Scaling up of components has presented challenges requiring several iterations of
the detailed mechanical analysis as well as the optical analysis due to interaction with mounting assemblies for the
optical components. A flexure-style focus mechanism, driven by three precision actuators, moves the entire headring
assembly and provides real-time focus capability, and active primary mirror cooling is implemented for the Zerodur
primary. KMTNet engineering specifications are met with the current design, which uses Comsoft's Legacy PCTCS for
control. A complete operational telescope and enclosure are scheduled for installation in Tucson, AZ prior to shipping
the first hardware to CTIO in order to verify tracking, optical characteristics at various attitudes, and overall observatory
functionality. The cameras, being fabricated by The Ohio State University Department of Astronomy, Imaging Sciences
Laboratory (ISL), are proceeding in parallel with the telescope fabrication, and that interface is now fixed. Specifics of
the mechanical and optical design are presented, along with the current fabrication progress and testing protocols.
We are developing three 1.6m optical telescopes and 18k by 18k mosaic CCD cameras. These telescopes will be
installed and operated at three southern astronomical sites in Chile, South Africa, and Australia for the Korea
Microlensing Telescope Network (KMTNet) project. The main scientific goal of the project is to discover earth-like
extrasolar planets using the gravitational microlensing technique. To achieve the goal, each telescope at three sites will
continuously monitor the specific region of Galactic bulge with 2.5 minute cadence for five years. Assuming 12 hour
observation in maximum for a night, the amount of 200GB file space is required for one-night observations at each
observatory. If we consider the whole project period and the data processing procedure, a few PB class data storage,
high-speed network, and high performance computers are essential. In this paper, we introduce the KMTNet data
management plan that handles gigantic data; observation data collecting, image calibration, data reduction pipeline,
database archiving, and backup.
We present the design for the 340 Mpixel KMTNet CCD camera comprising four newly developed e2v CCD290-99
imaging sensors mounted to a common focal plane assembly. The high performance CCDs have 9k x 9k format, 10
micron pixels, and multiple outputs for rapid readout time. The camera Dewar is cooled using closed cycle coolers and
vacuum is maintained with a cryosorption pump. The CCD controller electronics, the electronics cooling system, and the
camera control software are also described.
TBR Construction and Engineering (TBR) has under development for the Korea Astronomy and Space Science Institute (KASI), a project to provide three 1.6 meter optical telescopes observatories in three southern countries: Chile, South Africa, and Australia. The contracting team has chosen to develop a full scale prototype of the observatory. This will become a functional assembly and testing facility for all three project telescopes in Tucson, Arizona. This prototyping concept is meant to allow the optics team to make changes to the observatory as needed for the scientific mission while minimizing the expense of making changes in remote countries.
The Korea Astronomy and Space Science Institute (KASI) are under development three 1.6m optical telescopes for the
Korea Micro-lensing Telescope Network (KMTNet) project. These will be installed at three southern observatories in
Chile, South Africa, and Australia by middle 2014 to monitor dense star fields like the Galactic bulge and Large
Magellanic Cloud. The primary scientific goal of the project is to discover numerous extra-solar planets using the
gravitational micro-lensing technique. We have completed the final design of the telescope. The most critical design
issue was wide-field optics. The project science requires the Delivered Image Quality (DIQ) of less than 1.0 arcsec
FWHM within 1.2 degree radius FOV, under atmospheric seeing of 0.75 arcsec. We chose the prime-focus configuration
and realized the DIQ requirement by using a purely parabolic primary mirror and four corrector lenses with all spherical
surfaces. We present design results of the wide-field optics, the primary mirror coating and support, and the focus system
with three linear actuators on the head ring.
Multi-purpose Infra-Red Imaging System (MIRIS) is a near-infrared camera onboard on the Korea Science and
Technology Satellite 3 (STSAT-3). The MIRIS is a wide-field (3.67° × 3.67°) infrared imaging system which employs a
fast (F/2) refractive optics with 80 mm diameter aperture. The MIRIS optics consists of five lenses, among which the
rear surface of the fifth lens is aspheric. By passive cooling on a Sun-synchronous orbit, the telescope will be cooled
down below 200 K in order to deliver the designed performance. As the fabrication and assembly should be carried out
at room temperature, however, we convert all the lens data of cold temperature to that of room temperature. The
sophisticated opto-mechanical design accommodates the effects of thermal contraction after the launch, and the optical
elements are protected by flexure structures from the shock (10 G) during the launch. The MIRIS incorporates the wide-band
filters, I (1.05 μm) and H (1.6 μm), for the Cosmic Infrared Background observations, and also the narrow-band
filters, Paα (1.876 μm) and a specially designed dual-band continuum, for the emission line mapping of the Galactic
interstellar medium. We present the optical design, fabrication of components, assembly procedure, and the performance
test results of the qualification model of MIRIS near-infrared camera.
Multi-purpose Infra-Red Imaging System (MIRIS) is the main payload of the Korea Science and Technology Satellite-3
(STSAT-3), which is being developed by Korea Astronomy & Space Science Institute (KASI). MIRIS is a small space
telescope mainly for astronomical survey observations in the near infrared wavelengths of 0.9~2 μm. A compact wide
field (3.67 x 3.67 degree) optical design has been studied using a 256 x 256 Teledyne PICNIC FPA IR sensor with a
pixel scale of 51.6 arcsec. The passive cooling technique is applied to maintain telescope temperature below 200 K with
a cold shutter in the filter wheel for accurate dark calibration and to reach required sensitivity, and a micro stirling cooler
is employed to cool down the IR detector array below 100K in a cold box. The science mission of the MIRIS is to
survey the Galactic plane in the emission line of Paschen-α (Paα, 1.88 μ;m) and to detect the cosmic infrared background
(CIB) radiation. Comparing the Paα map with the Hα data from ground-based surveys, we can probe the origin of the
warm-ionized medium (WIM) of the Galaxy. The CIB is being suspected to be originated from the first generation stars
of the Universe and we will test this hypothesis by comparing the fluctuations in I (0.9~1.2 um) and H (1.2~2.0 um)
bands to search the red shifted Lyman cutoff signature. Recent progress of the MIRIS imaging system design will be
MIRIS is a compact near-infrared camera with a wide field of view of 3.67°×3.67° in the Korea Science and
Technology Satellite 3 (STSAT-3). MIRIS will be launched warm and cool the telescope optics below 200K by pointing
to the deep space on Sun-synchronous orbit. In order to realize the passive cooling, the mechanical structure was
designed to consider thermal analysis results on orbit. Structural analysis was also conducted to ensure safety and
stability in launching environments. To achieve structural and thermal requirements, we fabricated the thermal shielding
parts such as Glass Fiber Reinforced Plastic (GFRP) pipe supports, a Winston cone baffle, aluminum-shield plates, a
sunshade, a radiator and 30 layers of Multi Layer Insulation (MLI). These structures prevent the heat load from the
spacecraft and the earth effectively, and maintain the temperature of the telescope optics within operating range. A micro
cooler was installed in a cold box including a PICNIC detector and a filter-wheel, and cooled the detector down to a
operating temperature range. We tested the passive cooling in the simulated space environment and confirmed that the
required temperature of telescope can be achieved. Driving mechanism of the filter-wheel and the cold box structure
were also developed for the compact space IR camera. Finally, we present the assembly procedures and the test result for
the mechanical parts of MIRIS.
The Korea Astronomy and Space Science Institute (KASI) is building the KASI Near Infrared Camera System (KASINICS) for the 61-cm telescope at the Sobaeksan Optical Astronomy Observatory (SOAO) in Korea. With KASINICS we will mostly do time monitoring observations, e.g., thermal variations of Jovian planet atmospheres, variable stars, and blazars. We use a 512 x 512 InSb array (Aladdin III Quadrant, Raytheon Co.) for L-band observations as well as J, H, and Ks-bands. The field-of-view of the array is 6 x 6 arcmin with 0.7 arcsec/pixel. Since the SOAO 61-cm telescope was originally designed for visible band observations, we adopt an Offner relay optical system with a Lyot stop to eliminate thermal background emission from the telescope structures. In order to minimize weight and volume, and to overcome thermal contraction problems, we optimize the mechanical design of the camera using the finite-element-method (FEM) analysis. Most of the camera parts including the mirrors are manufactured from the same melt of aluminum alloy to ensure homologous contraction from room temperature to 70 K. We also developed a new control electronics system for the InSb array (see the other paper by Cho et al. in this proceedings). KASINICS is now under the performance test and planned to be in operation at the end of 2006.