Development and performance of the real-time VLBI correlator (RVC)

The Real-time VLBI Correlator (RVC) is a new type processor for the Very-Lo ng-Baseline Interferometry (VLBI). This correlator was primarily designed f or supporting the VLBI Space Observatory Programme (VSOP). Two particular t echniques, the fringe rotator after correlation and the lag-time extension technique, are newly developed for the RVC. The correlation circuit size of VLBI correlator is reduced to half by introducing the new fringe rotator, and it makes possible to realize a large delay window being essential in fi nding a cross correlation in real-time. The delay window can be changed fle xibly with the lag-time extension technique, and its technique is useful to detect the fringe peak in a VSOP observation. The new correlator was insta lled at the Usuda Deep Space Center in Japan, and is used in VSOP and other domestic VLBI observations. In this paper, the key features of the Real-ti me VLBI Correlator (RVC) focusing on these advanced techniques are presente d, and the results of its performance test are shown.