  The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope
started nominal operations on August 13, 2008, after about 60 days of
instrument checkout and commissioning and is currently performing an all-sky
gamma-ray survey from 30 MeV to above 300 GeV with unprecedented sensitivity
and angular resolution. The LAT pre-launch response was tuned using Monte Carlo
simulations and test beam data from a campaign necessarily limited in scope.
This suggested a conservative approach in dealing with systematics that affect
the reconstruction analysis of the first months of data taking. The first major
update of the instrument performance based on flight data is now being
completed. Not only are the LAT calibrations now based on flight data, but also
the ground event reconstruction has been updated to accommodate on-orbit
calibrations, and response was carefully verified using real data from
celestial sources. In this contribution we describe the current best knowledge
of the instrument, and our plans towards releasing public response functions to
support data release in year 2.
