KVN and VERA Array

Correlators

The correlation process is carried out by a VLBI correlator located at KJCC (Korea-Japan Correlation Center) at Daejeon, which has been developed as the KJJVC (Korea-Japan Joint VLBI Correlator) located at KJCC (Korea-Japan Correlation Center) project. Hereafter it is tentatively called "Daejeon correlator". The Daejeon correlator can process the data stream of up to 8192 Mbps from maximum 16 antenna stations at once. Currently the raw observed data of KVN stations are recorded and playbacked with Mark5B, and those of VERA stations are recorded and playbacked with OCTADISK at the data rate of 1024 Mbps. Data formats available in the next observing season are 16 IFs$\times$16 MHz ("C5 mode" in The Daejeon correlator terminology), 8 IFs$\times$32 MHz ("C4 mode''), and 2 IFs$\times$128 MHz ("C2 mode''). The C4 and C2 modes are newly available from the 2016A and 2018A seasons, respectively. Minimum integration times (time resolution) are 0.2048, 0.8192, and 1.6384 seconds for C2, C4, and C5 modes, respectively, and the number of frequency channels within each IF is 8192 for both modes (i.e. maximum frequency resolution is about 1.95 kHz). By default, the number of frequency channels is reduced to 128 (for continuum) or 512 (for line) via channel integration after correlation. One may put a special request of number of frequency channels to take better frequency resolution. The number of frequency channels can be selected among 512, 1024, 2048, 4096 or 8192. Final correlated data is served as FITS-IDI file.

Specification of The Daejeon correlator is summarized in Table [*].


Table: Specification of The Daejeon correlator$^{a}$.
Max. number of antennas 16
correlation mode C2(128 MHz Bandwidth, 2 stream)
C4(32 MHz Bandwidth, 8 stream)
C5(16 MHz Bandwidth, 16 stream)
Max. number of corr./input 120 cross + 16 auto
Sub-array 2 case(12+4, 8+8)
Bandwidth 512 MHz
Max. data rate/antenna 2048 Mbps VSI-H(32 parallels, 64MHz clock)
Max. delay compensation $\pm$ 36,000 km
Max. fringe tracking 1.075 kHz
FFT work length 16+16 bits fixed point for real, imaginary
Integration time 25.6 msec $\sim$ 10.24 sec
Data output channels 8192 channels
Data output rate Max. 1.4GB/sec at 25.6msec integration time
$^{a}$For more details, see
http://kvn.kasi.re.kr/status_report/correlator_status.html.



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KaVA ( KVN and VERA Array )