Update on The Ultra-Fast Flash Observatory (UFFO) Pathfinder.

The Ultra-Fast Flash Observatory (UFFO) uses an X/gamma and an optical/UV instrument to observe gamma-ray bursts (GRB) starting milliseconds after burst trigger and location. The X/gamma instrument, a standard coded-mask camera, locates the GRB and triggers the system. The optical/UV instrument, the Slewing Mirror Telescope (SMT), is planned to use an array of micro-electromechanical (MEMS) mirrors, with negligible moments of inertia, to steer its beam rapidly and accurately. The UFFO Pathfinder is scheduled to be launched into orbit by 2012 January. In this presentation, we give the current design of the pathfinder, with a 191 square centimeter LSO+MAPMT X/gamma detector and a 10 cm aperture SMT. We estimate that we will observe ∼44 GRB per year, and detect ∼10 GRB with both instruments. The UFFO will provide the most rapid optical/UV observations of GRB available thus far, and yield a sizable sample of observations of the rise-phase of GRB light curves for the first time. [ABSTRACT FROM AUTHOR]