Wide-field UV imaging: Current capabilities and performance requirements for future missions

I give a brief history of UV space telescopes, paying particularly attention to imaging facilities that operate at UV wavelengths. I examine a number of science drivers for space imaging at UV and blue-optical wavelengths (≲0.5μm) for the coming decade, and discuss some possible synergies with future optical-IR imaging facilities, such as LSST and Euclid. While the present “Golden Age” of UV astronomy may be drawing to a close, an important new imaging facility - the Ultraviolet Imaging Telescope (UVIT) onboard Astrosat - should begin operations in 2014. This instrument will provide astronomers with a wide-field (Ω∼0.2 deg2) UV imaging capability at an angular resolution (FWHM ∼1.5″-1.8″) that approaches those of ground-based optical telescopes. I also describe a proposed wide-field UV/blue-optical imaging telescope (CASTOR) that would provide HST-quality images over a ∼0.7 deg2 field in three broad filters covering the range 150-550 nm.