sentences:  This group used the principle of a sea-cliff interferometer in which the antenna (formerly a World War II radar) observed the sun at sunrise with interference arising from the direct radiation from the sun and the reflected radiation from the sea.With this baseline of almost 200 meters, the authors determined that the solar radiation during the burst phase was much smaller than the solar disk and arose from a region associated with a large sunspot group.The Australia group laid out the principles of aperture synthesis in a ground-breaking paper published in 1947.