Korean VLBI Network (KVN)

Recent News

KVN joined scientific observations of East Asia VLBI Network (2017 June)

Scientific operation of the EAVN (East Asia VLBI Network) has started in 2017. After the commissioning in 2016, the EAVN conducted a series of 17 scientific observatinos at 22/43GHz of M87 and SgrA* between 2017 March and May, some of which were in synchronized with EHT-ALMA 230 GHz VLBI campaign. KVN joined these EAVN observations together with Sejong (Korea), VERA (Japan), Tianma and Urumqi (China), and other EVAN telescopes.

Commissioning of 130 GHz VLBI polarization observation (2017 March)

A KVN KSP (PAGaN) team, led by Prof. Trippe, S. (Seoul National University), has successfully obtained high resolution linear polarization images of AGNs using KVN at 130 GHz by correcting for the instrumental polarization effect from KVN polarization observations. The instrumental leakage term (D-term) is measured to be about 10% at 130 GHz.

Multi frequency polarization images of CTA 102
Linear polarization images of CTA 102 obtained with KVN in 22.682, 43.332, 86.632, and 129.334 GHz bands, respectively from the left. Contour map shows the distribution of total intensity and colored map indicates the linear polarization distribution with red vector for polarization direction.

Commissioning of 8 Gbps recording (2017 January)

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).

8 Gbps recording image
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.

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

Data reduction Pipeline developed (2016 August)

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.

VLBI images obtained with KVN and the Sejong 22-m radio telescope (2016 June)

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.

(Left) The image only with KVN. (Right) The image with KVN and Sejong
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 (2015 October)

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

First simultaneous K/Q-band fringes obtained with VERA (2014 September)

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.

KVN joined officially the EVN (European VLBI Network) (2014 January)

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

A 6.7GHz receiver installed in KVN Ulsan Radio Observatory (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.

GPS receiver installed in each KVN station (2012 December)

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.

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Korean VLBI Network (KVN)