PREDICTION OF THE DETECTION LIMIT IN A NEW COUNTING EXPERIMENT

Seon, Kwang-Il The Korean Astronomical Society 2008 Journal of The Korean Astronomical Society Vol.41 No.4

When a new counting experiment is proposed, it is crucial to predict whether the desired source signal will be detected, or how much observation time is required in order to detect the signal at a certain significance level. The concept of the a priori prediction of the detection limit in a newly proposed experiment should be distinguished from the a posteriori claim or decision whether a source signal was detected in an experiment already performed, and the calculation of statistical significance of a measured source signal. We formulate precise definitions of these concepts based on the statistical theory of hypothesis testing, and derive an approximate formula to estimate quickly the a priori detection limit of expected Poissonian source signals. A more accurate algorithm for calculating the detection limits in a counting experiment is also proposed. The formula and the proposed algorithm may be used for the estimation of required integration or observation time in proposals of new experiments. Applications include the calculation of integration time required for the detection of faint emission lines in a newly proposed spectroscopic observation, and the detection of faint sources in a new imaging observation. We apply the results to the calculation of observation time required to claim the detection of the surface thermal emission from neutron stars with two virtual instruments.

「造成雜物器用有功化主錄」과 불영사의 불교회화

정명희 국립중앙박물관 2014 미술자료 Vol.- No.86

Bulyeongsa Temple, which is now a branch temple of Bulguksa Temple, was once under the auspices of Woljeongsa Temple in Gangwon-do Province - before the Japanese colonial era. This paper examines the monk-painters who were active in the areas of Gyeongsangbuk-do Province and characteristics of their Buddhist paintings by studying the Buddhist projects carried out at the Bulyeongsa Temple throughout the seventeenth to the nineteenth centuries. Chapter II focuses on the details of Buddhist ritual utensils required for daily rites and for the Buddhist projects held by Bulyeongsa Temple in the seventeenth century by investigating Joseong-japmulgiyong-yugong-hwajurok (造成雜物有功化主걧 Records on the donors of miscellaneous votive objects for building Bulyeongsa Temple). This record documents the details, including the dates, of the Buddhist projects, meaning establishment of halls and pagodas, and production of Buddhist paintings, statues and other utensils. It lists the names of monks, who were responsible for collecting donations, and further contains detailed descriptions of “miscellaneous essential items”or japmulgiyong in Korean, such as offertory vessels, vessels placed on altars or tables, and ritual utensils for daily and special rites. Bulyeongsa Temple was severely damaged during the Japanese invasion of Korea in 1592, Imjin waeran. Joseong-japmulgiyong-yugong-hwajurok records the miscellaneous essential items that the temple was equipped with for restoring its function and their written order indicates their priorities. The items included Buddhist statues and paintings as well as various rituals utensils. It was possible to understand the internal and external facilities of the temple by understanding these items, which also helped comprehend the function of Buddhist paintings. Among them, what is noteworthy is the equipment that was designed for altars. In line with this, Buddhist paintings were produced, including the paintings for the middle and lower altars, and for rituals. In addition to the items for use in the permanent top and middle altars such as ceremonial robes and incense burners, there were also items for lower altars that were custombuilt. While temples were equipped with most of the “miscellaneous items”by the 1620s, some ritual robes and instruments were added at the time when Buddhist paintings were created for the occasion of erecting Yeongsanjeon Hall and Myeongbujeon Hall. The next chapter examines the paintings of the local monk-painters and their characteristics in style by studying the Buddhist paintings of the eighteenth and nineteenth centuries in Bulyeongsa Temple. There were not many monk-painters and monk-craftsmen available in Gangwon-do Province, so monk-painters from Gyeongsangbuk-do Province were more engaged in the production than those from Gangwon-do Province. This is evidenced from the records that Daeseungam Hermitage had looked for masters to build Buddhist palanquin and that the extant Nectar Ritual Painting of the 15 Buddhist paintings that were executed under the leadership of Gyerim was painted by Cheolhyeon of Oeosa Temple in Pohang, Yeonghyeon and Takjin of Tongdosa Temple. The establishment of Daeungjeon Hall in the 1730s was led by a monk-painter who was based in Donghwasa Temple on Palgongsan Mountain. The Sakyamuni Preaching Assembly for Daeungjeon Hall completed in 1735 was based on the draft of the Sakyamuni Preaching Assembly of Beophwasa Temple painted by Kwaemin(快旻). Master monk-painter Goengwon(宏遠) and other monk-painters of Palgongsan Mountain led the production of the former, which was grander in scale than the latter and had new iconographies. The Threematrix Bodhisattvas of 1739 was led by the master monk-painter Milgi of Unbusa Temple and assisted by a monk-painter of Palgongsan Mountain. Milgi(密機) is resemblant to the Palgongsan School in their drafts, which continues Euigyun’ painting style, but they are rather different in style. The Three-Matrix Bodhisattvas in Bulyeongsa Temple reflects the style of monk-painters from the regions of Gyeongsangbuk-do Province such as Cheono of Girimsa Temple in Gyeongju and Noehyeon of Bogyeongsa Temple in Pohang, and Sakyamuni Preaching Assembly shows the influence of the Palgongsan School. By the eighteenth century, the Buddhist projects were extended in scale and monk-artists from different regions often cooperated. Thus, in the letter of prayer and the inscription of paintings were written the names of the temples to which the monk-painters were registered. While the Buddhist paintings were mainly led by the monk-painters of Palgongsan Mountain in the previous era, in the nineteenth century many monk-painters participated from Sabulsan Mountain. There were also cases where monk-artists Hwasan Jaegeun(華山在根) and Seokong Cheolyu(石翁喆侑) cooperated, and they mainly practiced on Geumgangsan Mountain as wellas in the regions of Gyeongsang-do and Gyeonggi-do provinces. Through the examination of the Buddhist paintings of Bulyeonsa Temple, located on the borders between Gyeongsangbukdo and Gangwon-do provinces, it was possible to observe the expansion of monk-painters’ sphere of activity and the changes of participating groups of monk-painters.

DEVELOPMENT OF WIDE-FIELD IMAGING CAMERA FOR ZODIACAL LIGHT OBSERVATION

KWON S. M.,HONG S. S.,SHIN K. J. The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.4

We have developed a wide-field imaging camera system, called WICZO, to monitor light of the night sky over extended period. Such monitoring is necessary for studying the morphology of interplanetary dust cloud and also the time and spatial variations of airglow emission. The system consists of an electric cooler a CCD camera with $60\%$ quantum efficiency at 500nm, and a fish-eye lens with $180^{\circ}$ field of view. Wide field imaging is highly desired in light of the night sky observations in general, because the zodiacal light and the airglow emission extend over the entire sky. This paper illustrates the design of WICZO, reports the result of its laboratory performance test, and presents the first night sky image, which was taken, under collaboration with Byulmaro Observatory, on top of Mt. Bongrae at Yongweol in January, 2004.

PROTO-MODEL OF AN INFRARED WIDE-FIELD OFF-AXIS TELESCOPE

Kim, Sang-Hyuk,Pak, Soo-Jong,Chang, Seung-Hyuk,Kim, Geon-Hee,Yang, Sun-Choel,Kim, Myung-Sang,Lee, Sung-Ho,Lee, Han-Shin The Korean Astronomical Society 2010 Journal of The Korean Astronomical Society Vol.43 No.5

We develop a proto-model of an off-axis reflective telescope for infrared wide-field observations based on the design of Schwarzschild-Chang type telescope. With only two mirrors, this design achieves an entrance pupil diameter of 50 mm and an effective focal length of 100 mm. We can apply this design to a mid-infrared telescope with a field of view of $8^{\circ}{\times}8^{\circ}$. In spite of the substantial advantages of off-axis telescopes in the infrared compared to refractive or on-axis reflective telescopes, it is known to be difficult to align the mirrors in off-axis systems because of their asymmetric structures. Off-axis mirrors of our telescope are manufactured at the Korea Basic Science Institute (KBSI). We analyze the fabricated mirror surfaces by fitting polynomial functions to the measured data. We accomplish alignment of this two-mirror off-axis system using a ray tracing method. A simple imaging test is performed to compare a pinhole image with a simulated prediction.

DEVELOPMENT OF 2.8-GHZ SOLAR FLUX RECEIVERS

윤영주,박용선,김창희,이방원,김정훈,유세호,이철환,한진욱,김영윤 한국천문학회 2014 Journal of The Korean Astronomical Society Vol.47 No.6

We report the development of solar flux receivers operating at 2.8 GHz to monitor solar radio activity. Radio waves from the sun are amplified, filtered, and then transmitted to a power meter sensor without frequency down-conversion. To measure solar flux, a calibration scheme is designed with a noise source, an ambient load, and a hot load at 100$\;^{\circ}$C. The receiver is attached to a 1.8 m parabolic antenna in Icheon, owned by National Radio Research Agency, and observation is being conducted during day time on a daily basis. We compare the solar fluxes measured for last seven months with solar fluxes obtained by DRAO in Penticton, Canada, and by the Hiraiso solar observatory in Japan, and finally establish equations to convert observed flux to the so-called Penticton flux with an accuracy better than 3.2 sfu.

DEVELOPMENT OF WIDE-FIELD IMAGING CAMERA FOR ZODIACAL LIGHT OBSERVATION

권석민,홍승수,신기진 한국천문학회 2004 Journal of The Korean Astronomical Society Vol.37 No.5

We have developed a wide-eld imaging camera system, called WICZO, to monitor light of the nightsky over extended period. Such monitoring is necessary for studying the morphology of interplanetarydust cloud and also the time and spatial variations of airglow emission. The system consists of anelectric cooler, a CCD camera with 60% quantum eciency at 500nm, and a sh-eye lens with 180eld of view. Wide eld imaging is highly desired in light of the night sky observations in general,because the zodiacal light and the airglow emission extend over the entire sky. This paper illustratesthe design of WICZO, reports the result of its laboratory performance test, and presents the rst nightsky image, which was taken, under collaboration with Byulmaro Observatory, on top of Mt. Bongraeat Yongweol in January, 2004.

AN EVALUATION OF THE SOLAR RADIO BURST LOCATOR (SRBL) AT OVRO

HwangBo, J.E.,Bong, Su-Chan,Cho, K.S.,Moon Y.J.,Lee, D.Y.,Park, Y.D.,Gary Dale E.,Dougherty Brian L. The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.4

The Solar Radio Burst Locator (SRBL) is a spectrometer that can observe solar microwave bursts over a wide band (0.1-18 GHz) as well as detect the burst locations without interferometry or mechanical scanning. Its prototype has been operated at Owens Valley Radio Observatory (OVRO) since 1998. In this study, we have evaluated the capability of the SRBL system in flux and radio burst location measurements. For this, we consider 130 microwave bursts from 2000 to 2002. The SRBL radio fluxes of 53 events were compared with the fluxes from USAF/RSTN and the burst locations of 25 events were compared with the optical flare locations. From this study, we found: (1) there is a relatively good correlation (r = 0.9) between SRBL flux and RSTN flux; (2) the mean location error is about 8.4 arcmin and the location error (4.7 arcmin) of single source events is much smaller than that (14.9 arcmin) of multiple source events; (3) the minimum location error usually occurred just after the starting time of burst, mostly within 10 seconds; (4) there is a possible anti-correlation (r = -0.4) between the pointing error of SRBL antenna and the location error. The anti-correlation becomes more evident (r=-0.9) for 6 strong single source events associated with X-class flares. Our results show that the flux measurement of SRBL is consistent with that of RSTN, and the mean location error of SRBL is estimated to be about 5 arcmin for single source events.

PERFORMANCE OF THE TRAO 13.7-M TELESCOPE WITH NEW SYSTEMS

정일교,강현우,정재훈,이창훈,변도영,제도흥,강성주,이영웅,이창원 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.6

We report the performance of the 13.7-meter Taeduk Radio Astronomy Observatory (TRAO) radio telescope. The telescope has been equipped with a new receiver, SEQUOIA-TRAO, a new backend system, FFT2G, and a new VxWorks operating system. The receiver system features a 16-pixel focal plane array using high-performance MMIC preamplifiers; it shows very low system noise levels, with system noise temperatures from 150 K to 450 K at frequencies from 86 to 115 GHz. With the new backend system, we can simultaneously obtain 32 spectra, each with a velocity coverage of 163 kms¯1 and a resolution of 0.04 kms¯1 at 115 GHz. The new operating system, VxWorks, has successfully handled the LMTMC-TRAO observing software. The main observing method is the on-the-fly (OTF) mapping mode; a position-switching mode is available for small-area observations. Remote observing is provided. The antenna surface has been newly adjusted using digital photogrammetry, achieving a rms surface accuracy better than 130 μm. The pointing uncertainty is found to be less than 500 over the entire sky. We tested the new receiver system with multi-frequency observations in OTF mode. The aperture efficiencies are 43±1%, 42±1%, 37±1%, and 33±1%, the beam efficiencies are 45±2%, 48±2%, 46±2%, and 41±2% at 86, 98, 110, and 115 GHz, respectively.

Development of Light weighted Optical Telescope Kit using Aluminum Profile and Isogrid Structure

박우진,이선우,한지민,안호재,지태근,김창곤,김도훈,이수민,김영재,김건희,김정현,김일훈,박수종 한국천문학회 2022 Journal of The Korean Astronomical Society Vol.55 No.1

We introduce the Transformable Reflective Telescope (TRT) kit that applies an aluminum profile as a base plate for precise, stable, and lightweight optical system. It has been utilized for optical surface measurements, developing alignment and baffle systems, observing celestial objects, and various educational purposes through Research \& Education projects. We upgraded the TRT kit using the aluminum profile and truss and isogrid structures for a high-end optical test device that can be used for prototyping of precision telescopes or satellite optical systems. Thanks to the substantial aluminum profile and lightweight design, mechanical deformation by self-weight is reduced to maximum 67.5~$\mu$m, which is an acceptable misalignment error compared to its tolerance limits. From the analysis results of non-linear vibration simulations, we have verified that the kit survives in harsh vibration environments. The primary mirror and secondary mirror modules are precisely aligned within 50~$\mu$m positioning error using the high accuracy surface finished aluminum profile and optomechanical parts. The cross laser module helps to align the secondary mirror to fine-tune the optical system. The TRT kit with the precision aluminum mirror guarantees high quality optical performance of 5.53~$\mu$m Full Width at Half Maximum (FWHM) at the field center.

TILT CORRECTION FOR A WIDE-FIELD ON-AXIS TELESCOPE USING THE SYMMETRICITY OF OPTICAL ABERRATIONS

Lee, Chung-Uk,Kim, Yunjong,Kim, Seung-Lee,Lee, Dong-Joo,Cha, Sang-Mok,Lee, Yongseok,Kim, Dong-Jin The Korean Astronomical Society 2021 Journal of The Korean Astronomical Society Vol.54 No.4

It is difficult for observers to conduct an optical alignment at an observatory without the assistance of an optical engineer if optomechanical parts are to be replaced at night. We present a practical tilt correction method to obtain the optimal optical alignment condition using the symmetricity of optical aberrations of a wide-field on-axis telescope at night. We conducted coarse tilt correction by visually examining the symmetry of two representative star shapes obtained at two guide chips facing each other, such as east-west or north-south pairs. After coarse correction, we observed four sets of small stamp images using four guide cameras located at each cardinal position by changing the focus positions in 10-㎛ increments and passing through the optimum focus position in the range of ±200 ㎛. The standard deviation of each image, as a function of the focus position, was fitted with a second-order polynomial function to derive the optimal focus position at each cardinal edge. We derived the tilt angles from the slopes converted by the distance and the focus position difference between two paired guide chip combinations such as east-west and north-south. We used this method to collimate the on-axis wide-field telescope KMTNet in Chile after replacing two old focus actuators. The total optical alignment time was less than 30 min. Our method is practical and straightforward for maintaining the optical performance of wide-field telescopes such as KMTNet.