COAST in the near infrared: solutions for infrared interferometry

There are difficult problems involved in building a near-infrared interferometer which uses more than two elements simultaneously. These problems have been overcome at the Cambridge Optical Aperture Synthesis Telescope(COAST). This has allowed us to make the first closure phase measurements on an astronomical source in the infrared. We describe a scheme for fast, low noise readout of an infrared focal-plane array detector, capable of adequately sampling pupil plane fringes on three simultaneous baselines, as well as a procedure for aligning a many-component beam-combiner in the infrared. Finally, the performance of the working COAST infrared system is discussed.