Development of the Far‐Infrared Interferometric Telescope Experiment

We have developed the Far‐Infrared Interferometric Telescope Experiment (FITE). It will be the first astronomical infrared interferometer working in space. FITE is a balloon‐borne telescope, and will operate in the stratosphere (at an altitude of 35 kilometers). FITE is a Michelson‐type stellar interferometer, and has a long baseline of 20 meters (at maximum). The purpose of the FITE project is to achieve a high spatial resolution of 1 arcsecond at a wavelength of 100 micrometers.For its first flight, FITE has an 8‐meter baseline, and the aim is to measure the interference fringes with a spatial resolution of 2.5 arcseconds. In order to achieve this aim, the two beams must be focused within 2.5 arcseconds accuracy in the imaging quality, within 10 arcseconds of accuracy in the beam alignment, and within 30 micrometers accuracy in the optical path length between the two beams. Also, the orientation of the telescope must be controlled within 2.5 arcseconds accuracy. To achieve such accuracy, the structural ...