  EChO is a three-modules (VNIR, SWIR, MWIR), highly integrated spectrometer,
covering the wavelength range from 0.55 $\mu$m, to 11.0 $\mu$m. The baseline
design includes the goal wavelength extension to 0.4 $\mu$m while an optional
LWIR module extends the range to the goal wavelength of 16.0 $\mu$m.
  An Instrument Control Unit (ICU) is foreseen as the main electronic subsystem
interfacing the spacecraft and collecting data from all the payload
spectrometers modules. ICU is in charge of two main tasks: the overall payload
control (Instrument Control Function) and the housekeepings and scientific data
digital processing (Data Processing Function), including the lossless
compression prior to store the science data to the Solid State Mass Memory of
the Spacecraft. These two main tasks are accomplished thanks to the Payload On
Board Software (P-OBSW) running on the ICU CPUs.
