Fringe Visibility Estimators for the Palomar Testbed Interferometer

Visibility estimators and their performance are presented for use with the Palomar Testbed Interferometer (PTI). One operational mode of PTI is single-baseline visibility measurement using pathlength modulation with synchronous readout by a NICMOS-3 infrared array. Visibility is estimated from the fringe quadratures, either incoherently, or using source phase referencing to provide a longer coherent integration time. The visibility estimators differ those used with photon-counting detectors in order to account for biases attributable to detector offsets and read noise. The performance of these estimators is affected not only by photon noise, but also by the detector read noise and errors in estimating the bias corrections, which affect the incoherent and coherent estimators differently. Corrections for visibility loss in the coherent estimators using the measured tracking jitter are also presented.