Status report of the UFFO-pathfinder

Gamma-Ray Bursts (GRBs) are the most energetic explosions in the universe, their optical photonflux rise very quickly, typically within one minute, then fall off gradually. Hundreds of GRBs optical light curveshave been measured since the first discovery of GRB in 1967. However, only a handful of measurements havebeen made within a minute after the gamma ray signal.

Because of this drawback, the short-hard type GRBs andrapid-rising GRBs, which may account for 30% of all GRBs, remain practically unexplored. To reach sub-minutetimescales, the Ultra-Fast Flash Observatory (UFFO) uses a rapidly moving mirror to redirect the optical beaminstead of slewing the entire spacecraft.

The first realization of this concept is UFFO-pathfinder, which is equippedwith fast-response Slewing Mirror Telescope (SMT) and a UFFO Burst Alert and Trigger Telescope (UBAT).SMT has a slewing mirror to redirect optical photons into a telescope and then record them by an intensified CCD.UBAT uses coded mask to provide X-ray trigger from a GRB and provides the GRB location for SMT.

UFFOssub-minute measurements of the optical emission of dozens of GRBs each year will result in a more rigorous testof current internal shock models, probe the extremes of bulk Lorentz factors, provide the first early and detailedmeasurements of fast-rise GRB optical light curves, and help verify the prospect of GRB as a new standard candle.The UFFO-pathfinder is fully integrated with the Lomonosov satellite and is scheduled to be launched in late 2013or early 2014.

We will present the latest progress in this conference