Angular resolution, confusion, and dynamic range constraints on the design of next generation radio telescopes for centimeter wavelengths

The next generation of radio telescopes designed to work at centimeter wavelengths may have collecting areas of up to one million square meters, and in principal will be able to reach radio sources as weak as 100 nanojanskys in 12 hours or a few tens of nanojansky in a few hundred hours integration time. However, special care will be needed to achieve the high angular resolution needed to study individual sources and to reduce the effects of confusion and spurious responses below the thermal noise level. This will require array dimensions up to one thousand kilometers to achieve noise limited performance at 1.4 GHz (20 cm) and up to ten thousand kilometers at 300 MHz (1 meter). But, even then, the performance may be limited by the finite extent of the sources and the consequential blending of their images. A scenario is presented for the gradual implementation of a Square Kilometer Array with global dimensions to give submicrojansky sensitivity over a broad range of angular scales and surface brightness.