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Recent Progress of Daejeon Correlator Se-Jin Oh Duk-Gyoo Roh , Jae- Hwam Yeom , ChungSik Oh, Jinseung Jung, Dong- Kyu Jung, Youngjoo Yun , A. Miyazaki, T. Oyama , N. Kawaguchi, H. Kobayashi, K. Shibata, and staff of Correlator team of KASI/NAOJ.

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Recent Progress of DaejeonCorrelatorSe-Jin OhDuk-GyooRoh, Jae-HwamYeom, ChungSik Oh, Jinseung Jung, Dong-Kyu Jung, YoungjooYun, A. Miyazaki, T. Oyama, N. Kawaguchi, H. Kobayashi, K. Shibata, and staff of Correlator team of KASI/NAOJ

2nd IVTW, ICC Jeju, Korea. 10-12, Oct. 2013

  • Background
  • System Introduction
    • Playback System
    • RVDB System
    • VLBI Correlation Subsystem
    • Correlated VLBI Data Buffer(CVDB)
    • Post Processing SW
  • Recent Status
  • KJCC Operation
  • Experimental Result
  • Future Work
target array eavn
Target Array : EAVN
  • For KVN, KVN+VERA/JVN, and EAVN.
  • And also for Chinese Space-VLBI


in the Space

korea japan joint vlbi correlator kjjvc development project backgrounds
Korea-Japan Joint VLBI Correlator(KJJVC) Development ProjectBackgrounds
  • To establish the bigger, more powerful correlator and get the best performance in East Asian VLBI Network, we concluded that KASI & NAOJ join together to develop new Correlator.
  • MOU between KASI & NAOJ (2005. 7. 7.)  Development of Korea-Japan Joint VLBI Correlator, Common facility of correlation & data center
  • Joint Development Project was initiated respectively.Japan : 5 years from April 2005Korea : 5 years from Jan. 2006

Specification (1) of KJJVC

KASI + NAOJ  2006~2010

kjjvc framework


















Optical Fiber

Correlator Control & Operation S/W

KJJVC Framework
  • Yellow : NAOJ, Green : KASI
playback systems
Playback Systems
  • Mark5B playback  VSI compatible : KVN
  • DIR2000 is in use extensively at VERA.
    • VERA 2000, which is modified by NAOJ according to DIR1000, used for Playing back DIR2000 tape media for VERA.
  • OCTADISK : modified using RVDB with 4Gbps recorder/playback developed by NAOJ.
  • Optical Fiber : Capable of dealing with the full data rate of 8 Gbps.




raw vlbi data buffer rvdb
Raw VLBI Data Buffer (RVDB)

(N. Kawaguchi / NAOJ)

  • Purpose :
    • Adjust data format as like # of bits per sample, and so on
    • Easily synchronize the data while playback (heterogeneous recorder models)
    • Maintain the buffering between recorder speed(1 Gbps) and correlation speed(8 Gbps)
raw vlbi data buffer rvdb basic configuration

VSI Optical


Raw VLBI Data Buffer (RVDB)basic configuration

Control PC


Input Ports

4 C-ports


2Gbps, nominal

10GbE Switch



4 D-ports


1Gbps, nominal





vlbi correlation subsystem vcs 2007 8 2009 7
VLBI Correlation Subsystem (VCS)(2007.8-2009.7)

Antenna Unit

Corr & Acu.Unit

Antenna Unit

  • 16 Stations, 8Gbps /station
  • Serialized data sub-streams in time domain, and Parallel processing in frequency channels after FFT.
  • Full polarization correlation is supported (up to 8 stations)
  • Two sub-array modes are prepared (12+4 and 8+8).
  • Max. data output rate is 1.4GB/sec @ 25.6ms integration
cvdb correlated vlbi data buffer
CVDB(Correlated VLBI Data Buffer)
  • Max. data rate : 1.4GB/sec @25.6ms integ.(~10% at average operation)
  • need to implement massive storage to save the

correlation results with four 10GbE of VCS

  • CVDB (specification)
    • Architecture
      • Infiniband
    • Max. Capacity
      • 1~3 PB for 1 year (EAVN, Space VLBI)
      • 500 TB at initial phase (KVN, KJJVN)

~119 TB

post processing sw configuration
Post-Processing SW configuration
  • Developing with Japanese colleagues, NAOJ(CODA) and Kagoshima Univ.(GFS)
  • CODA file system (CCcoda ver2.1), FITSgen
    • to reduce the developing efforts & cost, and to have compatibility with MTK FX
recent status hardware rvdb
Recent Status : Hardware(RVDB)
  • By NAOJ
    • In RVDB system, 3 OCTADDB system changed to OCTADISK so as to support VERA(JVN) wideband observation, these are now testing in Mitaka.
    • After completion of test, these will be delivered to KJCC until end of October this year.
    • 2set OCTADISK2 systems were already ordered to manufacturer for supporting VERA wideband data with high speed(over 8 Gbps) recording

 Please refer to Kono-san’s presentation in detail on Saturday

recent status hardware vcs
Recent Status: Hardware(VCS)
  • New firmware was installed
    • DC-like component deletion @ band start
    • Phase concentration deletion @ band start
    • FFT operation : 16bit20bit

Experiments of scaling factor/requantization for FFT were performed, so new reasonable factors were determined.

Correlation is currently conducted using modified firmware as indicated above.

recent status software
Recent Status: Software
  • CODAgen/FITSgen
    • By Kan-yasan’s great effort of Leonid/NAOJ, creating time for CODA F/S was reduced within 3~4 hours for 8hours observation with 16MHz-16stream.
    • Also creating time for FITS was reduced within 1 hour for 8 hours observation with 16MHz-16stream.

 Creating time depends on the observational(correlation) mode.

new building
New Building

KASI Headquarter @Daejeon

East Asia VLBI Research Center


daejeon correlator

2012.07~ current

kjcc operation structure
KJCC - Operation Structure
  • KASI operates KJCC with supporting operational budget and know-how of NAOJ.



  • Oper. Support Group
  • KVN
  • VERA / JVN
  • EAVN
  • MitakaCorrelator

Korea-Japan Correlation Center

Project manager 1 , 1

Operation manager 1 , 1

System Engineer 3 , 3

Operator 2 , 6

Data quality analyzer 2 , 4



experimental results
Experimental Results
  • To adjust the scaling factor, requantization bit position and verify the performance of DaejeonCorrelator
  • Observation Code : r11027b
  • Array : KVN+VERA combined 7stations
  • Observation frequency : 22 GHz
  • Observation time : 9.2hours
  • Correlation mode : C5(16MHz BW, 16stream)
  • Integration time : 1.6384sec


By S.S. Lee et al

correlation backlog status
Correlation(backlog) Status

From 2013,


is normally operating

for C5 mode(16MHz


future plan supporting for other mode wideband etc
Future plansupporting for other mode(wideband etc)
  • EAVN evaluation observation
    • 24th Sept. 2013
    • KVN, VERA, CVN(Shanghai, Kunming, Urumuqi), JVN ~ 13 stations had been joined
    • These observed data will be correlated by Daejeoncorrelator
  • Until the end of 2013
    • C2 (128MHz BW, 2streams)
    • C1 (256MHz BW, 1stream)
    • W1 (512MHz BW)
    • Polarization correlation
      • Test correlation will be also performed soon or within this year.
change tape to disc @ kjcc vera planned
Change Tape to Disc @ KJCC/VERA(Planned)




80 min.


6 Hours or longer

In VERA, parallel operation of tape and disk are now going on.