VLT Interferometer: II. Factors affecting on-axis operation

Abstract

The factors contributing to fringe contrast decrease for telescopes working near their diffraction limits are summarized. These factors include variations with time, such as atmospheric variations, vibrations, pathlength drift, and fringe tracking noise; and variations accross the pupil; variation with wavelength and factors relating to polarization effects; unequal beam intensities; detector resolution; and pupil transfer geometry. The effects on multispeckle images are also considered. The resulting error budget for the Very Large Telescope Interferometer (VLTI) is derived. It is concluded that the total random error in the fringe contrast is 4.2. The total calibratable systematic error amounts to 34 percent (27 percent due to the instrument, 9 percent due to the atmosphere).© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.