Laboratory measurements and modelling of the 'Pi of the Sky' detector response for more effective detection of GRB optical counterparts

摘要

The ultimate goal of the "Pi of the Sky" apparatus is observation of optical flashes of astronomical origin and other light sources variable on short timescales, down to tens of seconds. We search mainly for optical emissions of Gamma Ray Bursts, but also variable stars, novae, blazars, etc. This task requires a precise photometry - accurate measurement of the source's brightness (and it's variability). "Pi of the Sky" single cameras' field of view is about 20 deg X 20 deg. This causes a significant deformation of a point spread function (PSF), reducing quality of brightness and position measurement with standard photometric and astrometric algorithms. Improvement requires a careful study and modelling of the PSF. A dedicated laboratory setup has been created for obtaining isolated, high quality profiles, which in turn were used as the input for mathematical model. Results of it's application to brightness and position measurements as well as search for precursor of the naked-eye burst GRB080319B are shown in this paper.