• 천문학회보
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• 제46권2호
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• pp.61.4-61.4
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• 2021

Searching for technosignatures is the fundamental tool for finding the evidence of the extraterrestrial life in the Universe along with searching for biosignatures. We summarize the current status of the radio SETI(Search for Extraterrestrial Intelligence) such as the Breakthrough Listen project and suggest a concept of the VLBI SETI with KVN(Korean VLBI Network). In addition, we introduce conceptual studies of the SETI on the surface of Moon's farside and in lunar orbit.

• 천문학회지
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• 제56권1호
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• pp.91-96
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• 2023

In this paper, we describe the first multi-frequency synthesis observations of blazar 0059+581 made with the Radioastron space-ground interferometer in conjunction with the Korean VLBI Network (KVN), Medicina and Torun ground telescopes. We conducted these observations to assess the spaceground interferometer multi-frequency mode capability for the first time.

• 천문학논총
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• 제20권1호
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• pp.125-134
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• 2005

In this paper, we propose a small-scale Gigabit VLBI observing system for the Korean VLBI Network (KVN) under construction. The system consists of high-speed sampler, IP-VLBI board, PC-VSI board, and software correlator. Radio signal received by receiver is sampled by high-speed sample. at 1 Gsps (Gigabit sample per second) rate with 2 bits quantization. The digitized signal is recorded in PC and the software correlator does the cross correlation. IP-VLBI board will be used for the geodesy VLBI observation, while PC-VSI board is for the astronomical VLBI observation. The PC-VSI board adopts the VSI-H (VLBI Standard Interface Hardware). The proposed system is based on commercial PCs and therefore can be built inexpensively.

• 천문학논총
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• 제19권1호
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• pp.101-107
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• 2004

This paper describes the digital back-end system for getting the data to analyze the user observation mode by digitalize the analog data after receiving the space radio using the radio telescope, The received analog data will be digitalized by high-speed sampler with 1 Gsps for 4 channel frequency band of millimeter wave, and the digital data will be transported through the fiber-optic digital transmission system and WDM(wavelength division multiplex) to observation building, The wideband digital FIR(Finite Impulse Response) filters analyze the data for user observation mode to record the data in high-speed recorder with 1 Gbps. In this paper, we introduce the overall system configuration and features combined by various information and communication technology in radio astronomy briefly, which will be adopted by KVN(Korean VLBI Network).

• Journal of Astronomy and Space Sciences
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• 제26권4호
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• pp.567-588
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• 2009

한일공동VLBI상관기(Korea-Japan Joint VLBI Correlator, KJJVC)는 2010년 정상가동을 목표로 한국과 일본 간 공동으로 개발이 진행되고 있다. 이 연구에서는 KJJVC의 핵심이 되는 VLBI 상관 서브시스템(VLBI Correlation Subsystem, VCS)과 동일한 규격을 갖는 소프트웨어 상관기를 개발하였다. 소프트웨어 상관기는 VCS와 같은 8Gbps급, 8192출력채널, 262,144점 FFT(Fast Fourier Transform)의 규격을 갖고 있으며, VCS의 하드웨어 규격과 동일한 함수 알고리즘과 연산 레지스터를 적용하고 있다. 개발한 소프트웨어 상관기의 성능을 확인하기 위해 일본국립천문대의 VERA(VLBI Exploration of Radio Astrometry) 관측망으로 관측한 스펙트럼선과 연속파 천체를 대상으로 상관처리 실험을 수행하고, 그 결과는 미타카 FX 상관기의 스펙트럼 모양, 위상변화, 프린지 검출 등을 비교하였다. 실험을 통하여, VERA 관측데이터를 이용한 소프트웨어 상관기의 결과는 미타카 FX 상관기의 상관결과와 일치하는 것을 확인하여 그 유효성을 입증하였다. 향후 개발한 소프트웨어 상관기는 GUI와 같은 사용자 인터페이스와 상관 후 처리 부분을 개선하면 KJJVC와 함께 한국우주전파관측망(Korean VLBI Network, KVN)의 소프트웨어 상관기로 활용할 수 있을 것으로 기대된다.

• 천문학논총
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• 제21권2호
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• pp.95-100
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• 2006

In this paper, we describe the radio astronomical data processing system implementation using Mark5B and its development. KASI(Korea Astronomy and Space Science Institute) is constructing the KVN (Korean VLBI Network) until the end of 2007, which is the first VLBI(Very Long Baseline Interferometery) facility in Korea and dedicated for the mm-wave VLBI observation. KVN will adopt the DAS (Data Acquisition System) consisting of digital filter with various function and 1Gsps high-speed sampler to digitize the radio astronomical data for analyzing on the digital filter system. And the analyzed data will be recorded to recorder up to 1Gbps data rates. To test this, we have implemented the system which is able to process 1Gbps data rates and carried out the data recording experiment.

• 천문학회보
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• 제41권1호
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• pp.43.2-43.2
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• 2016

We present results of a calibrator search near twenty evolved stars using the Korean VLBI Network (KVN). Our evolved star targets include candidate sources for a Key Science Project (KSP) of the KVN. The KSP plans to investigate the spatial structure and dynamical effects between SiO and H2O maser regions including mass-loss process and development of asymmetry in circumstellar envelopes of evolved stars. For these purposes, we need compact and strong extragalactic sources close to the evolved stars. We carried out 5 observations in order to detect radio continuum sources that can be used for source frequency phase-referencing (SFPR) -based analysis. We observed 153 sources, out of which we detected 29 at 22 GHz and 20 at 43 GHz at signal-to-noise ratios higher than 50 at all baselines. Therefore, we successfully found target and calibrator pairs for the KVN KSP.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.30-30
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• 2003

GPS와 VLBI와 같은 우주측지 기술을 이용한 정밀 측위는 수 mn 정밀도의 관측소 좌표결정과 1 mm/year 정도의 고정밀 속도결정에 이용된다. 이를 위해서는 여러 가지 오차 요인들과 다양한 물리적 현상에 대한 모델링이 이루어져야 한다. 그 중의 하나가 해수 하중(ocean loading)에 의한 수직방향의 지각변위이다. 특히 한반도의 서해안은 복잡한 리아스식 해안으로 이루어져 있고, 조수간만의 차이가 크기 때문에 현존하는 모델의 정확도가 떨어진다. KVN(Korean VLBI Network)사업에서 추진하는 3기의 VLBI 중 2기가 서울과 제주도에 설치될 계획이므로, 해수하중에 의한 지각변위에 관한 연구가 선행되어야 한다. 또한 국내 GPS상시관측소의 많은 수가 서해안 지역에 설치되어 있다. 본 연구에서는 서해안 지역의 해수하중에 의한 수직방향의 지각변위를 GPS로 관측하고 이를 서해안 해수조류 모델의 정밀도를 향상시키는데 필요한 기초연구를 수행하였다. 서해안의 4개 GPS 관측소 위치에서의 해수하중에 의한 지각변위를 계산해본 결과 인천 지역에는 3 cm에 육박하는 지각변위가 수직으로 발생함을 알 수 있었다. 같은 크기와 위상의 지각변위 진폭을 GPS로 검출하기 위한 여러 가지 오차 보정과 GIPSY를 이용한 고정밀 키네마틱 GPS 자료처리에 대하여 상세히 소개한다.

• 천문학논총
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• 제19권1호
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• pp.93-99
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• 2004

In this paper, we describe a principle of the atomic frequency standard and clock system in VLBI(Very Long Baseline Interferometry). The hydrogen maser is a usual VLBI standard. During VLBI observations, signals emitted by distant sources of radio frequency energy(quasars) are received and recorded at several antennas. At each antenna(VLBI station), a very stable frequency standard(hydrogen maser) provides a reference signal which enables time-tagging to the quasar signals as they are being recorded on magnetic tapes or hard-disk modules. For each VLBl experiment, correlation of the time-tagged recorded information between the participating antennas is used to yield the arrival time differences of any specific quasar radio wave between the antennas. These time differences are used to calculate the relative antennas to each other. In this paper, we also introduce the KVN(Korean VLBI Network) atomic frequency standard and clock system.

• 천문학논총
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• 제19권1호
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• pp.83-92
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• 2004

In this paper, we introduce the development of the large storage system in order to record the observed space radio signal in the Korean VLBI Network(KVN) with high-speed. The KVN is the Very Long Baseline Interferometery(VLBI) to observe the birth of star, the structure of space by constructing radio telescope with diameter 21m at the Seoul, Ulsan, Jeju from 2001 to 2007 years. To do this, Korea Astronomy Observatory joined the international consortium for developing the high-speed large storage system(Mark 5), which is developed by MIT Haystack observatory. The Mark 5 system based on hard disk has to record up to 1 Gbps the observed space radio signal. The main features of Mark 5 system are as follows; First it is able to directly record the input data to the hard disk without PC1(Peripheral Component Interconnect) internal bus, and the second, it has two hard disk banks, which are able to hot-swap ATA/IDE type very cheap up to 1 Gbps recording and playback. The third is that it follows the international VLBI standard interface hardware(VSI-H). Therefore it can be connect directly the VSI-H type system at the input/output. Finally it also supports e- VLBI(Electronic-VLBI) through the standard Gigabits Ethernet connection.