Characterizing the aerosol atmosphere above the Observatorio del Roque de los Muchachos by analysing seven years of data taken with an GaAsP HPD-readout, absolutely calibrated elastic LIDAR

Abstract

We present a new elastic LIDAR concept, based on a bi-axially mounted Nd:YAG laser and a telescope with HPD readout, combined with fast FADC signal digitization and offline pulse analysis. The LIDAR return signals have been extensively quality checked and absolutely calibrated. We analyse seven years of quasi-continuous LIDAR data taken during those nights when the MAGIC telescopes were operating. Characterization of the nocturnal ground layer yields zenith and azimuth angle dependent aerosol extinction scale heights for clear nights. We derive aerosol transmission statistics for light emitted from various altitudes throughout the year and separated by seasons. We find further seasonal dependencies of cloud base and top altitudes, but none for the LIDAR ratios of clouds. Finally, the night sky background light is characterized using the LIDAR photon backgrounds.

Performance evaluation of three silicon photomultiplier detector modules within the MAGIC telescopes PMT-based camera

“…The results essentially confirmed our calculations with measured values of 4.3 times more LoNS and 1.9 times more Cherenkov photons. The ∼ 12% difference in LoNS intensity still could be considered in agreement because the LoNS not only depends on the simulated parameters but also on the rotating star field in the imaging camera plane, variable atmospheric conditions (Fruck et al, 2022) and variations in the LoNS (Roach et al, 1958;Patat, 2008).…”

Aerosol measurements at sub-percent precision using wide-field stellar photometry

“…The validity of this assumption should be tested, for every FRAM location, using other devices with the capability of 3-D aerosol reconstruction, such as steerable LIDARs. Recently, a study using the elastic LIDAR of the MAGIC experiment, located at Observatorio Roque de los Muchachos, La Palma, in the immediate vicinity of one of the currently operating FRAMs (labelled CTA-N in the following), has been published [5], indicating that the stratification hypothesis is not fulfilled. Nevertheless, some information can be extracted from FRAM data itself.…”

The influence of reduced atmospheric transmission on the CTA-North performance

“…In this study, the influence of clouds with bases at 3, 5 and 7 km a.g.l. with transmissions T = 0.75 and T = 0.50 is presented [14]. The full CTA-N configuration in this study consists of 4 Large-Sized Telescopes and 15 Medium-Sized Telescopes (figure 1).…”