  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.
