Longitudinal Shower Profile Reconstruction from Fluorescence and Cherenkov Light

Traditionally, longitudinal shower profiles are reconstructed in fluorescence light experiments by treating the Cherenkov light contribution as background. Here we will argue that, due to universality of the energy spectra of electrons and positrons, both fluorescence and Cherenkov light can be used simultaneously as signal to infer the longitudinal shower development. We present a new profile reconstruction method that is based on the analytic least-square solution for the estimation of the shower profile from the observed light signal and discuss the extrapolation of the profile with a Gaisser-Hillas function.