The ultra-violet/optical telescope of the Swift MIDEX mission

The Swift MIDEX mission is the first-of-its-kind observatory for multi-wavelength transient astronomy. The goal of the mission is to ascertain the origin of gamma-ray bursts and to utilize these bursts to probe the early universe. The Ultra-Violet/Optical Telescope (UVOT) is one of three telescopes flying aboard Swift. The UVOT is a working `copy' of the Optical Monitor on the X-ray Multi-mirror Mission (XMM-Newton). It is a Ritchey-Chretien telescope with microchannel plate intensified charged-coupled devices (MICs) that provide sub-arcsecond imaging. These MICs are photon-counting devices, capable of detecting very low signal levels. When flown above the atmosphere, the UVOT will have the equivalent sensitivity of a 4 m telescope on the ground, reaching a limiting magnitude of 24 for a 1000 second observation in the white light filter. A rotating filter wheel contains sensitive photometric broadband UV and visual filters for determining photometric redshifts. The filter wheel also contains UV and visual grisms for performing low-resolution spectroscopy.