Stellar Interferometry from the Ground and Space

Stellar Interferometry began more than 80 years ago with the pioneering measurement of the diameter of Betelqueuse by Michelson and Pease using a 20 foot beam mounted at the top of the 10011 Hooker telescope at Mt. Wilson. Essentially no other work was done in this field until the 1960's when Hanbury-Brown and his colleagues developed and used the Intensity Interferometer at Narrabri, Australia to measure the diameters of a number of important hot stars. The modern period of Stellar Interferometry really began in the 1970's with the successes of 3 or 4 small research groups in the US and Europe, and scientific and technical progress in the field has been outstanding, particularly in the last decade. This has lead to the development of two major ground based facilities: NASA's own Keck Interferometer and ESO's Very Large Telescope Interferometer, and a number of space interferometers such as the Space Interferometer Mission (SIM), and the Terrestrial Planet Finder (TPF), among others. I will review the principles, history, and scientific progress in the field both on the ground and in space, and I will discuss a mission concept under development here at NASA Goddard, the Fourier-Kelvin Stellar Interferometer, a near-term mid-infrared imaging interferometer, which can serve as a scientific and technical pre-cursor for some of the more ambitious concepts being discussed within the Astronomical and NASA communities.