Long-baseline Michelson interferometry with large ground-based telescopes operating at optical wavelengths. II. Interferometry at infrared wavelengths.

The theoretical bases, techniques, and instrumentation applied in long baseline interferometry of astrophysical objects at IR wavelengths are surveyed. Light detection is carried out with single photoelectric sensors functioning in the 1-30 microns window or with one- or two-dimensional CCD device grids which measure the incoming flux. Numerical expressions have been devised to account for single-photon, background and detector intrinsic noise sources and standard noise values have been calculated for each. The SNR and phase stability of sensed image fringes determine if the photoelectric analysis will proceed by synchronous detection or quadratic detection, respectively. The interference will be analyzed either in the image or in terms of the registration on the pupil plane of the detector. Techniques for estimating the image spectral density and limiting magnitudes are reviewed. Applications of long-baseline systems to studying asteroids, comets, star formation, and galactic nuclei are discussed, noting the large advantages available in visible wavelength studies if the instrumentation was space-based.