Stephane Rivoire | Searcharxiv

arXiv2026

Development of a Raman Lidar for the Southern Site of the Cherenkov Telescope Array Observatory

The future CTAO will reach a sensitivity and energy resolution never obtained until now by any other high-energy gamma-ray experiment. Studying the atmospheric conditions during the CTAO observations, namely the extinction and backscatter coefficients, permits a very precise evaluation of the atmospheric UV absorption, a parameter that directly affects the energy and flux spectra of the CTAO-studied sources. This paper describes the motivation for the LUPM Raman Lidar system, a Lidar specifically designed to fulfill the CTAO requirements for the south site in Chile. Preliminary results obtained during a two-year campaign at the OHP Observatory are presented. Our results include estimations of the extinction, back-scatter, and Lidar ratio at both 355 and 532 nm and confirm the conformity of our prototype to the CTAO requirements

astro-ph.IM↗

arXiv2019

Raman LIDARs for the atmospheric calibration along the line-of-sight of CTA

The Cherenkov Telescope Array (CTA) is the next generation ground based observatory for gamma ray astronomy at very high energies. Employing more than 100 Imaging Atmospheric Cherenkov Telescopes in the northern and southern hemispheres, it was designed to reach unprecedented sensitivity and energy resolution. Understanding and correcting for systematic biases on the absolute energy scale and instrument response functions will be a crucial issue for the performance of CTA. The LUPM group and the Spanish/Italian/Slovenian collaboration are currently building two Raman LIDAR prototypes for the online atmospheric calibration along the line of sight of the CTA. Requirements for such a solution include the ability to characterize aerosol extinction at two wavelengths to distances of 30 km with an accuracy better than 5%, within time scales of about a minute, steering capabilities and close interaction with the CTA array control and data acquisition system as well as other auxiliary instruments. Our Raman LIDARs have design features that make them different from those used in atmospheric science and are characterized by large collecting mirrors (2.5 m2), liquid light guides that collect the light at the focal plane and transport it to the readout system, reduced acquisition time and highly precise Raman spectrometers. The Raman LIDARs will participate in a cross calibration and characterization campaign of the atmosphere at the CTA North site at La Palma, together with other site characterization instruments. After a one year test period there, an in depth evaluation of the solutions adopted by the two projects will lead to a final Raman LIDAR design proposal for both CTA sites.

astro-ph.IM↗