• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.208.2-208.2
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• 2012

The Slewing Mirror Telescope (SMT) is a key telescope of Ultra-Fast Flash Observatory (UFFO) space project to explore the first sub-minute or sub-seconds early photons from the Gamma Ray Bursts (GRBs) afterglows. The first realization of UFFO is the 20kg UFFO-Pathfinder (UFFO-P) to be launched on board the Russian Lomonosov satellite in 2013 by the Soyuz-2 rocket. Once the UFFO Burst Alert & Trigger Telescope (UBAT) detects the GRBs, Slewing mirror (SM) will rotate to bring the GRB into the SMT's field of view instead of slewing the entire spacecraft. SMT can image the UV/Optical counterpart with about 4-arcsec accuracy. However it will provide a important understanding of the GRB mechanism by measuring the sub-minute optical photons from GRBs. SMT can respond to the trigger over $35^{\circ}{\times}35^{\circ}$ wide field of view within 1 sec by using Slewing Mirror Stage (SMS). SMT has 10-cm Ritchey-Chretien telescope and $256{\times}256$ pixilated Intensified Charge-Coupled Device (ICCD) on focal plane. In this paper, we discuss the overall design of UFFO-P SMT instrument and payloads development status.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.2 s.191
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• pp.13-18
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• 2007

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.30.3-30.3
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• 2011

한국천문연구원은 Giant Magellan Telescope Fast Steering Mirror prototype을 개발 중이고, 반사경 제작과 tip-tilt 시스템 제작을 목표로 하고 있다. 반사경은 직경이 1.06m, 두께가 약 140mm, 질량이 약 100kg인 meniscus 타입인 비축 비구면 반사경이다. Tip-tilt 시스템은 바람에 의한 반사경의 진동과 망원경의 tracking jitter를 보정하기 위한 장치로써 tip-tilt 각도가 ${\pm}20"$ 범위 내에서 약 30Hz로 작동하는 시스템이다. 반사경 cell은 반사경 뒷면에 조립되어 반사경 cell 내부에 주입되는 진공과 함께 반사경의 무게를 지지하고, tip-tilt 시스템을 작동시키는 액츄에이터가 장착되는 base structure 역할을 한다. 이 논문에서는 반사경 cell의 초기설계와 반사경 cell에 발생할 수 있는 하중 조건에 따른 응력과 변위, 반사경 cell의 두께에 따른 고유진동수를 해석한 결과들에 대해 논한다.

• Journal of the Optical Society of Korea
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• v.9 no.2
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• pp.68-73
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• 2005

When aligning catoptric or catadioptric telescopes for space cameras, it is difficult to align precisely if the field of view is large or there are several reflective surfaces. The quantitative knowledge of mirror misalignments greatly helps align a misaligned telescope precisely, and also reduce the alignment time. This paper describes a generalized reverse-optimization alignment solution algorithm using Zernike sensitivity, and proposes the minimum number of fields to take interferograms. This method was successfully applied on a Cassegrain telescope design for Earth observation from space with arbitrary misalignments and a model including some primary mirror deformation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.66-66
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• 2012

We describe the space project of Ultra-Fast Flash Observatory (UFFO), which will observe early optical photons from gamma-ray bursts (GRBs) with a sub-second optical response, for the first time. The UFFO will probe the early optical rise of GRBs, opening a completely new frontier in GRB and transient studies, using a fast-response rotatable mirror system which redirects opitical path to telescope instead of slewing of telescopes or spacecraft. In our small UFFO-Pathfinder experiment, scheduled to launch aboard the Lomonosov satellite in June 2012, we use a motorized mirror in our Slewing Mirror Telescope instrument to achieve less than one second optical response after X-ray trigger. We describe the science and the mission of the UFFO project, including a serious version called UFFO-100 which will be launched in 2014. With our program of ultra-fast optical response GRB observatories, we aim to gain a deeper understanding of GRB mechanisms, and potentially open up the z>10 universe to study via GRB as point source emission probes.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.56.4-57
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• 2017

The Schwarzschild-Chang off-axis telescope is a "linear astigmatism-free" confocal system. The telescope comprises two pieces of aluminum-alloy freeform mirrors that are fabricated with diamond turning machine (DTM) process. We designed optomechanical structures where optical components in the telescope system can be adjustable on a linear stage. Optomechanical deformation caused by the weight of system itself and its temperature variation is analyzed by the finite element analysis (FEA). The results show that the deformation is estimated in the tolerance range. For the optic-axis alignment of telescope system, three-point alignment (TPA) method is chosen. The TPA method uses three parallel lasers and a plane mirror. Point source images were taken from collimated light and field observation. The performance of optical system was tested by point spread function and aberration measurement of the point sources.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.55.4-56
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• 2018

Linear Astigmatism Free - Three Mirror System (LAF-TMS) is the linear astigmatism free off-axis wide field telescope with D = 150 mm, F/3.3, and $FOV=5.51^{\circ}{\times}4.13^{\circ}$. We report the design and analysis results of its mirrors and optomechanical structures. Tolerance allowance has been analyzed to the minimum mechanical tolerance of ${\pm}0.05mm$ that is reasonable tolerance for fabrication and optical alignment. The aluminum mirrors are designed with mounting flexure features for the strain-free mounting. From Finite Element Analysis (FEA) results of mounting torque and self-weight, we expect 33 - 80 nm RMS mirror surface deformations. Shims and the L-bracket are mounted between mirrors and the mirror mount for optical alignment. The mirror mount is designed with four light-weighted mechanical parts. It can stably and accurately fix mirrors, and it also suppresses some of stray light.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.39.4-40
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• 2017

According to the Korean government's Long-term Space Development Plan 2040, "Creative space science research" is included in a statement to investigate the origin and evolution of the universe by conducting a series of Korean space telescope missions: launch of space telescopes on a small satellite and an international collaboration explorer by 2020, a mid-size domestic space telescope by 2030, and a large size Korea leading international space telescope by 2040. We studied the feasibility of the future Korean Space Telescope (KST) for a mid-size domestic satellite platform. In order to pursue the uniqueness of the science program, we consider a wide range of observing wavelength (0.2um ~ 2.0um) with a spectral resolution of R~6 in the NUV and optical bands, and R~30 for NIR, utilizing an off-axis TMS(Three Mirror System) optics with a wide field of view ($2{\times}4$ degrees) which is optimized for ultra-low surface brightness sources. The main science goals of the mission include investigations of the galaxy formation, cosmic web, and the cosmic background radiation in the NUV-NIR regions. In this paper, we present the science cases and several technical challenges to be resolved along with the future milestones for the success of the KST mission.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.85.1-85.1
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• 2013

GMT(Giant Magellan Telescope)는 25.4m의 주경과 3.2m의 부경으로 이루어진 거대망원경이다. 3.2m의 부경은 빠른 tip-tilt로 망원경을 제어하는 Fast Steering Mirror(FSM)와 적응광학계로 이루어진 Adaptive Secondary Mirror (ASM)로 구분된다. 한국천문연구원은 국내외 협력기관들과 함께 부경 FSM의 시험모델개발을 수행하고 있다. 부경은 1.06m의 반사경 일곱 개로 이루어져 있는데, 한 개의 광축 반사경 주위로 여섯개의 비축 반사경이 둘러싸여서 하나의 3.2m 반사경과 같은 기능을 하고 있다. 비축 비구면 반사경에 대한 시험모델의 반사면을 가공한 결과 표면가공 정밀도가 11.7nm rms의 정밀도를 갖는 반사경을 가공하였다(target : <20nm rms). 또한 test-bed를 제작하여 tip-tilt 정밀도를 제어한 결과 성능요구 조건 값인 0.03arcsec 제어에 성공하였고, 더 나아가 0.01arcsec의 tip-tilt 제어도 가능한 것으로 판단된다.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.43.3-44
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• 2017

We report the operational highlights of KMTNet in the point of observing rate, image pre-processing and data reduction, observing run for each science program, and scientific publications performed in 2016. Major system upgrade has been conducted in the CCD camera and the wide field telescope optics: the post amp and readout electronics of the 18k Mosaic CCD camera at Siding Spring Observatory site has been fine tuned and the protected silver coat of the primary mirror has been replaced with the bare aluminium coat due to the degradation of reflectivity of the primary mirror surface. A plan of KMTNet observation system improvement for 2017 will be introduced in this talk.