The correlation process is carried out by a VLBI correlator at KJCC (Korea-Japan Correlation Center) of KASI, which has been developed by the Korea-Japan joint correlator development project, and named as "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 DIR-2000(VERA-2000) at the data rate of 1024 Mbps. The only data format available in the next observing season is 16 IFs x 16 MHz ("C5 mode" in The Daejeon correlator terminology). Minimum integration time (time resolution) is 1.6384 seconds at this mode, and the number of frequency channels within each IF is 8192 (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 8.
|Max. number of antennas||16|
C4(32MHz Bandwidth, 8 stream)b
C5(16MHz Bandwidth, 16 stream)
|Max. number of corr./input||120 cross + 16 auto|
|Sub-array||2 case(12+4, 8+8)|
|Max. data rate/antenna||2048 Mbps VSI-H(32 parallels, 64MHz clock)|
|Max. delay compensation||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 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://radio.kasi.re.kr/kvn/status_report_2016/correlator.html|