• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.233-244
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• 2012

The Korea Astronomy and Space Science Institute and the Department of Astronomy at the University of Texas at Austin are developing a near infrared wide-band high resolution spectrograph, immersion grating infrared spectrometer (IGRINS). The compact white-pupil design of the instrument optics uses seven cryogenic mirrors, including three aspherical off-axis collimators and four flat fold mirrors. In this study, we introduce the optomechanical mount designs of three off-axis collimating mirrors and one flat slit-viewer fold mirror. Two of the off-axis collimators are serving as H and K-band pupil transfer mirrors, and are designed as system alignment compensators in combination with the H2RG focal plane array detectors in each channel. For this reason, the mount designs include tip-tilt and parallel translation adjustment mechanisms to properly perform the precision alignment function. This means that the off-axis mirrors' optomechanical mount designs are among the most sensitive tasks in all IGRINS system hardware. The other flat fold mirror is designed within its very limitedly allowed work space. This slit-viewer fold mirror is mounted with its own version of the six-point kinematic optics mount. The design work consists of a computer-aided 3D modeling and finite element analysis (FEA) technique to optimize the structural stability and the thermal behavior of the mount models. From the structural and thermal FEA studies, we conclude that the four IGRINS mirror mounts are well designed to meet all optical stability tolerances and system thermal requirements.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.37.2-37.2
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• 2011

Our previous study on tiny pores (R < 2") observed by HINODE/Solar Optical Telescope (SOT) revealed that the plasma in the pores at the photosphere is always moving down and the pores are surrounded by the strong downward motions (highly red-shifted) of neighboring granulations. From this study, we speculated that the flow motions above the pore should be related with the motions at the photosphere, since the pore is strong magnetic field region. Meanwhile, SNU and KASI installed Fast Imaging Solar Spectrograph (FISS) in the Cude room of the 1.6 m New Solar Telescope (NST) at Big Bear Solar Observatory. FISS is a unique system that can do imaging of H-alpha and Ca II 8542 band simultaneously, which is quite suitable for studying of dynamics of chromosphere. To get some clue on the relationship between the photospheric and low-chromospheric motions at the pore region, we took a coordinate observation with NST/FISS and Hinode/SOT for new emerging active region (AR11117) on October 26, 2010. In the observed region, we could find two tiny pores and two small magnetic islands (SMIs), which have similar magnetic flux with the pores but does not look dark. Magnetic flux density and Doppler velocities at the photosphere are estimated by applying the center-of-gravity (COG) method to the HINODE/spectropolarimeter (SP) data. The line-of-sight motions above the photosphere are determined by adopting the bisector method to the wing spectra of Ha and CaII 8542 lines. As results, we found the followings. (1) There are upflow motion on the pores and downflow motion on the SMIs. (2) Towards the CaII 8542 line center, upflow motion decrease and turn to downward motion in pores, while the speed of down flow motion increases in the SMIs. (3) There is oscillating motion above pores and the SMIs, and this motion keep its pattern along the height. (4) As height increase, there is a general tendency of the speed shift to downward on pores and the SMIs. This is more clearly seen on the other regions of stronger magnetic field. In this talk, we will present preliminary understanding of the coupling of pore dynamics between the photosphere and the low-chromosphere.