Algorithm for Reconstructing EAS-Type Events of the TUS Orbital Detector

Abstract

On April 28, 2016, the TUS (Tracking Ultraviolet Setup), an orbital detector of extreme energy cosmic rays (EECRs) was launched into near-Earth orbit as a part of the Lomonosov satellite’s scientific equipment. The detector measures the fluorescent radiation of extensive air showers (EASes) appearing in the atmosphere after cosmic rays with energies of 100 EeV and higher penetrate into it. An algorithm is presented for reconstructing directions of the arrival of an EECR particle, based on an approximation of the track (EAS image) on the photodetector matrix in the form of a uniform rectilinear motion of a point (the image’s centroid). The technique is validated and its accuracy in the case of a Gaussian point spread function (PSF) is estimated using model examples. It can be used when reconstructing events of the TUS and similar missions in the future (e.g., K-EUSO).