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Welcome to Radio Astronomy Division's wiki site

This is a wiki page for sharing the information of Radio Astronomy Division in KASI. You may edit the pages after registering and logging in. All visitors can read all pages and all registered users can edit the pages. However editing some pages are allowed to some internal people.

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Sciences with KVN

The KVN was built by Korea Astronomy and Space Science Institute (KASI) for achieving the main goals

  • to study the formation and death of stars with observing water (H2O), methanol (CH3OH), and silicon monoxide (SiO) masers at high resolutions,
  • to investigate the structure and dynamics of our own Galaxy by conducting highly accurate astrometric VLBI observations toward the galactic radio sources, and
  • to study the nature of active galactic nuclei (AGN) and their population at high frequencies.

The KVN as a dedicated-VLBI network also aims to study the spectral and temporal properties of transient sources such as bursting star-forming regions, intra-day variable compact radio sources, gammaray flaring AGNs, etc by conducting systematic multi wavelength monitoring campaigns

KVN VLBI Observations

VLBI observations with KVN are remotely conducted at the KVN Array Operation Center in KASI, Daejeon. The obsevations are based on a schedule file in VEX (VLBI EXperiment) format. A VEX file contains various information relevant to individual observation such as sources, system setup, observing time, calibration mode, etc. The VEX file can be prepared either by using a VLBI scheduling software Sched or by modifying template VEX files. PIs are kindly asked to prepare and submit the VEX files to KVN AOC (kvnobs@kasi.re.kr) so that the AOC conducts the observations after double-checking the VEX files. PIs will be informed via email after the observations and correlations.

KVN Single Dish Observations

Single dish observations with KVN radio telescopes can be conducted either at individual KVN radio observatory or at the KVN Array Operation Center in KASI, Daejeon. Graphical user interface is available for the observations. Observational data are stored in CLASS (Continuum and Line Analysis Single-dish Software) format. The CLASS is one of Gildas packages developed at IRAM observatory. KVN field systems understand Python languages so that Python scripts may be used for the observations. In principle, PIs are supposed to conduct their own observations. The following observational modes are available for various purposes:

Cal and SkyDip for calibrating the data, Position Switching, Frequency Switching, Grid Mapping, Five Pointing, and Focus for spectroscopic observations, Cross Scan and OTF for continuum observations.

Continuum polarization observations and spectroscopic observations can be automatically conducted using Python scripts. Simultaneus multifrequency observations are available either at four frequency bands (22, 43, 86, 129GHz) in single polarization (LCP or RCP) or at two frequency bands in dual polarizations. Source catalogs are in a format readable by ASTRO software, one of Gildas packages.

Recent News

Commissioning of 8 Gbps recording

The 8 Gbps recording mode has been commissioned for multi-wavelength observations with a total bandwidth of 2 GHz (or with a bandwidth of 512MHz for each frequency band). The correlated flux densities of the 8 Gbps mode observations for 3C273 are higher, compared with the 1 Gbps mode observations by 
10% (K), 
12% (Q),
 9% (W),
 12% (D).

Images from the 8Gbps mode observations for 3C 273 at K-band (upper left), Q-band (upper right), W-band (lower left), and D-band (lower rifht). Peak flux density (denoted as p), rms (as r), and dynamic range (as DR) are given in the images.  Figure caption: Images of the 8Gbps mode observations for 3C 273 at K-band (upper left), Q-band (upper right), W-band (lower left), and D-band (lower rifht). Peak flux density (denoted as p), rms (as r), and dynamic range (as DR) are given in the images.

Spectra of the 8Gbps mode observations before(left) and after(right) a Bandpass calibration (BPASS) being applied. Figure caption: Spectra of the 8Gbps mode observations before(left) and after(right) a Bandpass calibration (BPASS) being applied.

Data reduction Pipeline developed

The KVN Pipeline has been developed including an application of the Frequency Phase Transfer (FPT) technique. (see Hodgson et al. 2016, JKAS, 49, 137 and also see its wiki page). We find that the pipelined data using phase transfer produces better results than a manually reduced dataset not using the phase transfer. Additionally we compared the pipeline results with a manually reduced phase-transferred dataset and found the results to be identical.

First simultaneous K/Q-band fringes obtained with VERA

First simultaneous fringes at K/Q-band between KVN and VERA were obtained, using the K/Q-band quasi-optics system installed at VERA stations.

VLBI images obtained with KVN and the Sejong 22-m radio telescope

The Sejong 22-m diameter radio telescope is located in Sejong, Korea. VLBI observations together with KVN and the Sejong 22-m radio telescope were conducted, yielding VLBI images of several bright compact extragalactic radio sources.

M87 Images from the KVN and Sejong 22-m radio telescopes at 22GHz band. (Left) The image only with KVN. (Right) The image with KVN and Sejong. Peak flux density (denoted as P), rms (as rms), and dynamic range (as DR) are given on top of the images.  Figure caption: M87 Images from the KVN and Sejong 22-m radio telescopes at 22GHz band. (Left) The image only with KVN. (Right) The image with KVN and Sejong. Peak flux density (denoted as P), rms (as rms), and dynamic range (as DR) are given on top of the images.

KVN joined the GMVA in Oct 2015

KVN has joined the GMVA in October 2015 and started to participate in the GMVA session in 2016 May.

KVN joined officially the EVN (European VLBI Network)

KVN joined the EVN as an Associate Member of EVN from 2014 January 1.

GPS receiver installed in each KVN station

One GPS receiver was installed at each KVN station. By estimating atmospheric wet delay and TEC(Total Electron Content) over all KVN stations, we expect to improve the accuracy of phase referencing and astrometric observations.

A 6.7GHz receiver installed in KVN Ulsan Radio Observatory

In 2013 August, the 6.7 GHz receiver was installed in KVN Ulsan. The KVN Ulsan was chosen for the installation based on RFI measurements. The first light was obtained soon after the installation. Single dish performance tests have been conducted. We expect to operate the KVN Ulsan at 6.7GHz in single dish and VLBI modes mainly for the observations toward 6.7GHz class II CH3OH masers.

start.txt · Last modified: 2017/09/27 10:58 (external edit)