The IFAE/UAB and LUPM Raman LIDARs for the CTA observatory

The Cherenkov Telescope Array (CTA) is the next generation of Imaging Atmospheric Cherenkov Telescopes. It will reach a sensitivity and an energy resolution with no precedent in very high energy gamma-ray astronomy. In order to achieve this goal, the systematic uncertainties derived from the atmospheric conditions shall be reduced to a minimum. Different instruments may help to understand and account for the precise state of the atmosphere at a given time. The Barcelona IFAE/UAB (acronyms for Institut de Física d'Altes Energies and Universitat Autònoma de Barcelona, respectively) and the Montpellier LUPM (Laboratoire Univers et Particules de Montpellier) groups are building Raman LIDARs, devices which can reduce the systematic uncertainties in the reconstruction of the gamma-ray energies from 20% down to better than 5%. The Raman LIDARs will have each 1.8 m mirror and use a coaxial two-color beam from a Nd-YAG laser. A light guide collects the light at the focal plane and transports it to the readout system. We have developed a monochromatic optical detector with the purpose of testing the readout chain of both LIDARs. This device is composed of a system of filters and a photomultiplier, and will be used to study an individual elastic channel. After characterizing the system, we will build a multiwavelength optical detector to collect also the sparse Raman signal and will optimize it to reduce every possible loss of signal. We report on the current status of the LIDAR development and the latest results on the different characterization tests.