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EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: THE QCAL-1 43 GHz CALIBRATOR SURVEY
Petrov, Leonid,Lee, Sang-Sung,Kim, Jongsoo,Jung, Taehyun,Oh, Junghwan,Sohn, Bong Won,Byun, Do-Young,Chung, Moon-Hee,Je, Do-Heung,Wi, Seog-Oh,Song, Min-Gyu,Kang, Jiman,Han, Seog-Tae,Lee, Jung-Won,Kim, American Institute of Physics 2012 The Astronomical journal Vol.144 No.5
<P>This paper presents the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q band) survey observed with the Korean VLBI Network. Of them, 14 objects used as calibrators were previously observed, but 623 sources have not been observed before in the Q band with very long baseline interferometry (VLBI). The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22-129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to –40°. Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in the range of 115-180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with a median formal uncertainty of 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies of 22 GHz and higher at 3/4 of the celestial sphere.</P>
Australia and the DPRK: The Sixty Years of Relationship
Leonid A. Petrov 인하대학교 국제관계연구소 2008 Pacific Focus Vol.23 No.3
The record of relations between Australia and the Democratic People’s Republic of Korea (DPRK) is one of the oddest and most chequered in diplomatic history. A short period of recognition and cultural cooperation was followed by the resurgent nuclear crisis and the drug-smuggling ship incident, which proved to be hard tests for this shaky relationship. The closure of the DPRK embassy to Australia in January 2008 once again left the public confused and the pundits guessing about the true reasons behind this quiet démarche. This paper examines the major ups and downs in the history of Australia-DPRK bilateral relations and offers some clues as to what might have been wrong in Australian policy and attitudes toward the isolated communist nation. Australian involvement in the US-led Proliferation Security Initiative and the ban on the supply of “luxury goods” to North Korea will be discussed. Interviews with serving and veteran diplomats, declassified DFAT archival material and international media reports provided the basis for this research.
EARLY SCIENCE WITH THE KOREAN VLBI NETWORK: EVALUATION OF SYSTEM PERFORMANCE
Lee, Sang-Sung,Petrov, Leonid,Byun, Do-Young,Kim, Jongsoo,Jung, Taehyun,Song, Min-Gyu,Oh, Chung Sik,Roh, Duk-Gyoo,Je, Do-Heung,Wi, Seog-Oh,Sohn, Bong Won,Oh, Se-Jin,Kim, Kee-Tae,Yeom, Jae-Hwan,Chung, American Institute of Physics 2014 The Astronomical journal Vol.147 No.4
<P>We report the very long baseline interferometry (VLBI) observing performance of the Korean VLBI Network (KVN). The KVN is the first millimeter-dedicated VLBI network in East Asia. The KVN consists of three 21 m radio telescopes with baseline lengths in a range of 305-476 km. The quasi-optical system equipped on the antennas allows simultaneous observations at 22, 43, 86, and 129 GHz. The first fringes of the KVN were obtained at 22 GHz on 2010 June 8. Test observations at 22 and 43 GHz on 2010 September 30 and 2011 April 4 confirmed that the full cycle of VLBI observations works according to specification: scheduling, antenna control system, data recording, correlation, post-correlation data processing, astrometry, geodesy, and imaging analysis. We found that decorrelation due to instability in the hardware at times up to 600 s is negligible. The atmosphere fluctuations at KVN baseline are partly coherent, which allows us to extend integration time under good winter weather conditions up to 600 s without significant loss of coherence. The post-fit residuals at KVN baselines do not exhibit systematic patterns, and the weighted rms of the residuals is 14.8 ps. The KVN is ready to image compact radio sources both in snapshot and full-track modes with residual noise in calibrated phases of less than 2 deg at 22 and 43 GHz and with dynamic ranges of ~300 for snapshot mode and ~1000 for full-track mode. With simultaneous multi-frequency observations, the KVN can be used to make parsec-scale spectral index maps of compact radio sources.</P>
Early Science of KVN: 43GHz fringe survey
이상성,김종수,정태현,손봉원,변도영,Lee, Sang-Sung,Petrov, Leonid,Kim, Jongsoo,Jung, Taehyun,Sohn, Bong Won,Byun, Do-Young 한국천문학회 2012 天文學會報 Vol.37 No.2
This paper presents the results of one of early sciences with Korean VLBI Network (KVN): a large fringe survey of compact radio sources at 43GHz. We established the catalog of correlated flux densities in three ranges of baseline projection lengths of 637 sources from a 43 GHz (Q-band) survey observed with the Korean VLBI Network. Of them, 623 sources have not been observed before at Q-band with VLBI. The goal of this work in the early science phase of the new VLBI array is twofold: to evaluate the performance of the new instrument that operates in a frequency range of 22--129 GHz and to build a list of objects that can be used as targets and as calibrators. We have observed the list of 799 target sources with declinations down to $-40{\circ}$. Among them, 724 were observed before with VLBI at 22 GHz and had correlated flux densities greater than 200 mJy. The overall detection rate is 78%. The detection limit, defined as the minimum flux density for a source to be detected with 90% probability in a single observation, was in a range of 115--180 mJy depending on declination. However, some sources as weak as 70 mJy have been detected. Of 623 detected sources, 33 objects are detected for the first time in VLBI mode. We determined their coordinates with the median formal uncertainty 20 mas. The results of this work set the basis for future efforts to build the complete flux-limited sample of extragalactic sources at frequencies 22 GHz and higher at 3/4 of the celestial sphere.