  Atmospheric spectroscopy of extrasolar planets is an intricate business.
Atmospheric signatures typically require a photometric precision of $1 \times
10^{-4}$ in flux over several hours. Such precision demands high instrument
stability as well as an understanding of stellar variability and an optimal
data reduction and removal of systematic noise. In the context of the EChO
mission concept, we here discuss the data reduction and analysis pipeline
developed for the EChO end-to-end simulator EChOSim. We present and discuss the
step by step procedures required in order to obtain the final exoplanetary
spectrum from the EChOSim`raw data' using a simulated observation of the
secondary eclipse of the hot-Neptune 55 Cnc e.
