Korean VLBI Network (KVN)

Daejeon Correlator

1. General Information

The correlation process is carried out by the Daejeon correlator located at KASI Daejoen headquarter. The maximum number of antenna stations that can be correlated at the same time is 16 for the Mark5B and VERA2000(DIR-2000) system. Thus, the correlator can process at once the data recorded by Mark5B with the three KVN stations and DIR-2000 with four VERA stations. In the correlator output, the maximum number of spectral point per antenna is 8192 points across all channels for Mark5B and DIR-2000. The time resolution of the correlator output is usually set to be 1.6384 second, but the high time resolution (down to 409.6 milliseconds for C5 mode(16 MHz bandwidth, 16stream)) is also available upon requests (though the total amount of output data becomes larger). Detail information about correlation mode, Integration time, and Channel integration are listed in below. Table 1 shows the detail specification of Deajeon Correlator.

Table 1. Specification of Daejeon Correlator.
# of antennas 16
# of inputs/antenna 4 bands(4Fx1P, 2Fx2P, 1Fx2P+2Fx1P)
Max. # of corr./input 120 cross + 16 auto
Sub-array 2 case(12+4, 8+8)
Bandwidth 512 MHz
Sampling, Digitization 1 Gsps by 2bit/sample
Maximum data rate/antenna 2 Gbps VSI-H(32parallels, 64 MHz clock
Maximum delay compensation +-36,000km
Maximum fringe tracking 1.075 kHz
Design architecture FX-type with FPGA
FFT word length 16+16 bits fixed point for real, imaginary
Integration time 25.6 msec~10.24 sec
Data output channels 8192 channels
Data output rate Maximum 1.4GB/sec at 25.6msec integration time

2. Correlation Processing

2.1 Correlation mode and Integration time

KJCC can currently support the following correlation mode.
-C5 (16 MHz BW, 16stream), Integration time : 1.6384sec @ correlation
Min. Integ. time : 409.6msec @ correlation
KJCC plans to support the following correlation mode until 2013.
-C2 (128 MHz BW, 2stream), Integration time : 1.6384sec @ correlation
-C1 (256 MHz BW, 1stream)
-W1 (512 MHz BW, 1port)

2.2 CODA/FITS

KJCC will basically support the following number of frequency channels in the prepared FITS file.
-Basic output channel of correlator : 8192 frequency channel
-Continuum : 128 frequency channel(64 channels integrated in post-correlation)
-Spectral line : 512 frequency channel(16 channels integrated in post-correlation)

2.3 FITS delivery

KJCC will deliver the FITS file to the PI via FTP server or USB memory or mobile disk.

2.4 Archiving policy

KJCC will organize the archiving policy for observation data, CODA and FITS file as below.
-Observation data : basically 2 months, and then it will be released.
-CODA : if correlated data will be used for astrometry or geodesy, it will be permanently stored at CODA server. Otherwise, the correlated raw data and CODA file system will be deleted after receiving the response from PI.
-FITS : it will be permanently archived at Archiving server.

2.5 Correlation expected time

Correlation processing will be about 1 week for preparing 1st version of FITS. However, KJCC will do their best to make correlation as fast as possible to deliver FITS file to PI.

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Korean VLBI Network (KVN)