The NISS (Near-infrared Imaging Spectrometer for Star formation history) have been developed by KASI as one of the scientific payloads onboard the first small satellite of NEXTSat program (NEXTSat-1) in Korea. The both imaging and low spectral resolution spectroscopy in the wide near-infrared range from 0.95 to 2.5µm and wide field of view of 2° x 2° is a unique capability of the NISS for studying the star formation in local and distant Universe. In the design of the NISS, special care was taken by implementing the off-axis system to increase the total throughput with limited resources from the small satellite. We confirmed that the mechanical structure of the NISS could be maintained in space through passive cooling of the telescope. To operate the infrared detector and spectral filters at 80K stage, the compact dewar module was assembled after the relay-lens module. The integrations of relay-lens part, primary-secondary mirror assembly and dewar module were independently performed, which alleviated the complex alignment process. The telescope and infrared sensor were validated for the operation at cryogenic temperatures of around 200K and 80K, respectively. The system performance of the NISS, such as focus, cooling efficiency, wavelength calibration and system noise, was evaluated by utilizing our constructed test facility. After the integration into the NEXTSat-1, the flight model of the NISS was tested under the space environments. The NISS is scheduled to be launched in late 2018 and it will demonstrate core technologies related to the future infrared space telescope in Korea.
The Korea Astronomy and Space Science Institute has developed NISS (Near-infrared Imaging Spectrometer for Star formation history) as a scientific payload for the first next generation of small satellite, NEXTSat-1 in Korea. NISS is a NIR imaging spectrometer exploiting a Linear Variable Filter (LVF) in the spectral passband from 0.95 um to 2.5 um and with low spectral resolution of 20. Optical system consists of 150mm aperture off-axis mirror system and 8-element relay-lenses providing a field of view of 4 square degrees. Primary and secondary aluminum mirrors made of RSA6061 are precisely fabricated and all of the lenses are polished with infrared optics materials. In principle, the optomechanical design has to withstand the vibration conditions of the launcher and maintain optical performance in the space environment. The main structure and optical system of the NISS are cooled down to about 200K by passive cooling for our astronomical mission. We also cool the detector and the LVF down to about 90K by using a small stirling cooler at 200K stage. The cooling test for whole assembled body has shown that the NISS can be cooled down to 200K by passive cooling during about 80 hours. We confirmed that the optomechanical structure is safe and rigid enough to maintain the system performance during the cooling, vibration and thermal vacuum test. After the integration of the NISS into the NEXTSat-1, space environmental tests for the satellite were passed. In this paper, we report the design, fabrication, assembly and test of the optomechanical structure for the NISS flight model.
NISS (Near-infrared Imaging Spectrometer for Star formation history) is a unique spaceborne imaging spectrometer (R = 20) onboard the Korea’s next micro-satellite NEXTSat-1 to investigate the star formation history of Universe in near infrared wavelength region (0.9 – 2.5 μm). In this paper, we introduce the NISS H2RG detector electronics, the test configuration, and the performance test results. Analyzed data will be presented on; system gain, dark current, readout noise, crosstalk, linearity, and persistence. Also, we present basic test results of a Korean manufactured IR detector, 640 x 512 InAsSb 15 μm pixel pitch, developed for future Korean lunar mission.
Korea Astronomy and Space Science Institute (KASI) successfully developed the Near-infrared Imaging Spectrometer for Star formation history (NISS), which is a scientific payload for the next-generation small satellite-1 (NEXTSat-1) in Korea and is expected to be launched in 2018. The major science cases of NISS are to probe the star formation in local and early Universe through the imaging spectroscopic observations in the near-infrared. The off-axis catadioptric optics with 150mm aperture diameter is designed to cover the FoV of 2x2 deg with the passband of 0.95-2.5μm. The linear variable filter (LVF) is adopted as a disperse element with spectral resolution of R~20. Given the error budgets from the optical tolerance analysis, all spherical and non-spherical surfaces were conventionally polished and finished in the ultraprecision method, respectively. Primary and secondary mirrors were aligned by using interferometer, resulting in residual wave-front errors of P-V 2.7μm and RMS 0.61μm, respectively. To avoid and minimize any misalignment, lenses assembled were confirmed with de-centering measurement tool from Tri-Optics. As one of the key optical design concepts, afocal beam from primary and secondary mirrors combined made much less sensitive the alignment process between mirrors and relay lenses. As the optical performance test, the FWHM of PSF was measured about 16μm at the room temperature, and the IR sensor was successfully aligned in the optimized position at the cryogenic temperature. Finally, wavelength calibration was executed by using monochromatic IR sources. To support the complication of optical configuration, the opto-mechanical structure was optimized to endure the launching condition and the space environment. We confirmed that the optical performance can be maintained after the space environmental test. In this paper, we present the development of optical system of NISS from optical design to performance test and calibration.
The NISS (Near-infrared Imaging Spectrometer for Star formation history) is the near-infrared instrument optimized to the first next generation of small satellite (NEXTSat-1) in Korea. The spectro-photometric capability in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the NISS will perform the large areal imaging spectroscopic survey for astronomical objects and low background regions. We have paid careful attention to reduce the volume and to increase the total throughput. The newly implemented off-axis optics has a wide field of view (2° x 2°) and a wide wavelength range from 0.9 to 3.8μm. The mechanical structure is designed to consider launching conditions and passive cooling of the telescope. The compact dewar after relay-lens module is to operate the infrared detector and spectral filters at 80K stage. The independent integration of relay-lens part and primary-secondary mirror assembly alleviates the complex alignment process. We confirmed that the telescope and the infrared sensor can be cooled down to around 200K and 80K, respectively. The engineering qualification model of the NISS was tested in the space environment including the launch-induced vibration and shock. The NISS will be expected to demonstrate core technologies related to the development of the future infrared space telescope in Korea.
Since the end of 2012, Korea Astronomy and Space Science Institute (KASI) has been developed the Near-infrared
Imaging Spectrometer for Star formation history (NISS), which is a payload of the Korean next small satellite 1
(NEXTSat-1) and will be launched in 2017. NISS has a cryogenic system, which will be cooled down to around 200K by
a radiation cooling in space. NISS is an off-axis catadioptric telescope with 150mm aperture diameter and F-number 3.5,
which covers the observation wavelengths from 0.95-3.8μm by using the linear variable filter (LVF) for the near infrared
spectroscopy. The entire field of view is 2deg x 2deg with 7arcsec pixel scale. Optics consists of two parabolic primary
and secondary mirrors and re-imaging lenses having 8 elements. The main requirement for the optical performance is
that the RMS spot diameters for whole fields are smaller than the detector pixel, 18μm. Two LVFs will be used for 0.9-
1.9μm and 1.9-3.8μm, whose FWHM is more than 2%. We will use the gold-coated aluminum mirrors and employ the
HgCdTe 1024x1024 detector made by Teledyne. This paper presents the conceptual opto-mechanical design of NISS.
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.