Study of the LAT PSF of the Gamma Ray Large Area Telescope

Abstract

GLAST is the next generation telescope for the study of the Gamma Ray Universe.The GLAST mission is composed of two instruments: the LAT (Large Area Telescope) exploring the energy range between 20 MeV and 300 GeV and the GBM (Gamma ray Burst Monitor) studying the region from 10 KeV up to 30 MeV.GLAST represents an important step beyond EGRET providing a large improvement in instrument performance: large Field of View (FOV), large energy range extending to unexplored region of energies larger than 10 GeV, large effective area, a factor of 30 improvement in sensitivity, a much smaller dead time and a very good Point Spread Function (PSF).Since GLAST will operate in a continuous scanning mode, for most of the time during the mission, photons from a source will be detected at different angles in the LAT field of view requiring a good PSF in order to disentangle between sources.We will present results on PSF studies performed with various sets of data. The selection criteria and algorithm have been initially developed on DC1 and DC2 data (simulation of one and 55 days respectively of data collected by the LAT), applied to the data collected with the 16 LAT towers during the I&T integration phase with cosmic ray muons and finally applied to the testbeam data collected in August 2006 at the CERN beam line.