• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.2
• /
• pp.56.3-56.3
• /
• 2015

한국우주전파관측망은 22GHz, 43GHz, 86GHz, 129GHz의 4주파수 동시관측 시스템을 운용하고 있다. 이 시스템으로부터 수신된 전파신호를 실시간으로 디지털 신호로 바꾸어 주는 장치인 샘플러의 국산화를 위하여, 우리는 3년간의 연구개발로 1GHz 샘플링을 할 수 있는 샘플링 장치를 설계/제작하였다. 그리고, 이를 연구 관측에 실제 적용할 수 있음을 보여 주었다. 본 연구에서는 한 단계 더 나아가 광대역 관측과 e-VLBI 구현을 위하여 전파관측 자료를 직접 첨단 연구망으로 보낼 수 있는 4GHz 샘플러를 개발 중에 있다. 이번 발표에서는 4GHz 샘플러에 대한 개발 현황 및 향후 계획을 소개한다.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.79.2-79.2
• /
• 2014

Galactic radio pulsar population is diverse. So far about 2300 radio pulsars are known in the Milky Way, in addition to Large and Small Magellanic Clouds. Radio pulsar observations at a few hundreds MHz up to ~10 GHz have been active and they are proved to be fruitful. Low frequencies are preferred mainly because of the steep ratio spectrum of pulsars. However, developments in pulsar backends (e.g. a wide-band spectrometer) and improved system sensitivities make it possible to observe pulsars at higher frequencies using large, single-dish telescopes up to ~18 GHz. Going forward, mm-wavelength observations is expected to open a new window in pulsar astronomy. In particular, frequencies well above ~15 GHz are pre-requisite to detect pulsars in the Galactic Center where radio pulsed signals are severely scattered by interactions with the interstellar medium. Recent discoveries strongly imply that there are subsets of pulsars with an apparently flat spectrum, such as magnetars. In April 2014, the first pulsar (magnetar) was discovered only 3 arcmin from Sgr A*, PSR J1745-2900. We will present a brief overview on pulsar populations focusing on those observable at high frequencies. We will also discuss prospects of pulsar observations in mm-wavelengths and how we can utilize the Korean VLBI network.

• Journal of Astronomy and Space Sciences
• /
• v.30 no.4
• /
• pp.345-353
• /
• 2013

A W-band Orthomode Transducer (OMT) has been developed for Korean VLBI Network (KVN) polarization observation. The OMT design was based on E-plane split-block technique using septum structure. 3-dimensional electromagnetic simulation was fully employed to optimize the performance of the OMT. Measurements of the fabricated OMT show that the return losses for the vertically and horizontally polarized modes are better than -20 dB across 80 ~ 108 GHz and the insertion losses for the both modes are less than 0.47 dB. The cross-polarization level of the OMT is less than -30 dB. The bandwidth of the developed OMT is estimated as around 30%.

• Publications of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.75-89
• /
• 2023

Technosignature, previously known as SETI(search for extraterrestrial intelligence), is the scientific evidence of past or present extraterrestrial civilizations. Since NRAO's Project Ozma was performed in 1960, most of the noticeable technosignature searches have been done by radio telescopes, hoping to find strong and narrow bandwidth signals that cannot be explained by known natural processes. Recently, the Breakthrough Listen project has opened a new opportunity for technosignature by utilizing both optical telescopes, radio telescopes, and next-generation radio telescope arrays. In this review, mainly based on NASA Technosignatures Workshop (2018), we review the current trends of technosignature surveys, as well as other possible methods for detecting technosignature. Also, we suggest what the Korean community could contribute the technosignature research, including the new SETI project with Korea VLBI Network (KVN).

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.1
• /
• pp.35.3-35.3
• /
• 2019

Blazars are a subclass of active galactic nuclei (AGNs) with relativistic jets aligned with our line of sight. The jet physics is yet to be understood, but can be studied with blazar variability (e.g., flares). The highly variable blazar 3C 279 has shown a general decline of its radio flux density since 2013, but the flux density has been increasing since 2017. To better understand physical properties of 3C 279 related with the flux variations, we analyze multi-frequency new radio data obtained with Korean VLBI Network (KVN), as well as archival data from Owens Valley Radio Observatory (OVRO) and Submillimeter Array (SMA). We measure the radio spectral variability and infer the relativistic jet properties of 3C 279. The high-cadence OVRO and SMA observations are used to construct detailed light curves of the source, and KVN data supplement the spectral coverage and allow us to locate the spectral break frequencies precisely. In this talk, we present our analysis results and interpret them using a blazar jet model.