In situ measurement of chromatic dispersion in an optical hypertelescope: a laboratory demonstration

Optical interferometry is a technique capable of achieving better spatial resolution than the world's largest monolithic telescopes at a fraction of the cost. Most interferometer architectures split the imaging bandwidth into a number of channels in order to prevent image degradation due to a large spectral bandwidth. An optical hypertelescope permits a much broader spectral bandwidth on a single channel than a conventional interferometer. However, a broader spectral bandwidth becomes more sensitive to differential chromatic dispersion, and this dispersion must be measured and corrected in order to maintain a high signal-to-noise ratio. A prototype dispersion measurement system is presented that is capable of measuring chromatic dispersion in an eight aperture hypertelescope. The optical design, calibration, data acquisition, and dispersion measurement process are described in detail. This system is capable of measuring differential dispersion to better than λ/100R M S and is scalable to a system with an order of magnitude more apertures.