  The characterization of the optical properties of the atmosphere in the near
UV, in particular the tropospheric aerosol stratification, clouds optical depth
and spatial distribution are common in the field of atmospheric physics, due to
aerosol effect on climate, and also in cosmic rays physics, for a correct
reconstruction of energy and longitudinal development of showers. The goal of
the ARCADE project is the comparison of the aerosol attenuation measurements
obtained with the typical techniques used in cosmic ray experiments
(side-scattering measurement, elastic LIDAR and Raman LIDAR) in order to assess
the systematic errors affecting each method providing simultaneous observations
of the same air mass with different techniques. For this purpose we projected a
LIDAR that is now under construction: it will use a 355 nm Nd:YAG laser and
will collect the elastic and the N2 Raman back-scattered light. For the
side-scattering measurement we will use the Atmospheric Monitoring Telescope, a
facility owned by the Colorado School of Mines and placed in Lamar (Colorado),
the site where our experiment will take place.

Instrumentation and Methods for Astrophysics