Global fringe search techniques for VLBI

Abstract

The usual fringe search technique for VLBI is correlator-based. Here we describe a more sensitive, global approach to fringe search (so named, because it yields a simultaneous solution for all of the delay and fringe rate parameters). By means of this approach, the number of parameters required for delay and rate compensation for an n element array is reduced from «2 — « to 3« — 3. The two methods described here—one based on the Fourier transform, the other, on a least-squares algorithm—may be viewed as variants of the self-calibration/hybrid mapping techniques which already are in widespread use