Future global astrometry missions have targeted the determination of p
ositions, parallaxes, and annual proper motions to the 10 mu as level.
This can be achieved through the use of fringe imaging interferometer
s, possibly featuring wide fields of view (e.g,, Fizeau configurations
). The basic location information is to be extracted from the fringe p
attern by proper implementation of the detection system and proper exp
loitation of the focal plane data. The sampling resolution requirement
s are a key trade-off issue between science and engineering: therefore
, fringe acquisition by means of realistic detectors and the resulting
accuracy in photocenter location is discussed herein, The location pe
rformance is described as a chi(2) minimization problem; the resulting
expressions are then evaluated in analytical form and by means of a M
onte Carlo simulation, which provide good agreement. In order to achie
ve the limiting Interferometer accuracy, 8-10 pixels per fringe period
are required, whereas a sampling resolution of 4-5 pixels per period
provides a 30% degradation. We evaluate the location accuracy degradat
ion induced by progressively reduced fringe visibility and increasing
noise level. The former provides a smooth performance reduction, accep
table to a wide extent, read-out noise is critical because the fringe
pattern signal is recorded over many pixels, each providing a comparab
le contribution to the overall noise.