The Signal-to-noise Ratio in Long-baseline Stellar Interferometry

Abstract

The signal-to-noise ratio for long-baseline stellar interferometers is evaluated. Results are derived for interferometers using collector areas large compared to the correlation length of atmospherically distorted wavefronts. Analysis is given for interferometers which interfere images of the object or images of the collector pupils and for situations where the result is taken point by point or spatially averaged with signal dependent or signal independent weighting functions. Using a complex gaussian model to represent the statistics of atmospherically distorted wavefronts, limiting magnitudes up to ∼ +17 are predicted for an interferometer using two collectors each of 1 m ² area. A restricted form of log-normal model is used to estimate the effects of scintillation on the pupil space interferometer.