The measurements of the vertical profiles of the atmospheric aerosol optical properties (i.e., the extinction and the backscatter coefficients) and water vapour mixing ratio, are based on the well-known single scattering lidar equation. The Raman scattering is an inelastic pure molecular scattering that has been successfully used in lidar remote-sensing techniques since the late 1960s. Focused...
For the pre-production phase of Cherenkov Telescope Array (CTA), the INFN Raman Lidar (IRL) has collected vertical profiles of aerosol optical properties in the UV region at Roque de los Muchachos Observatory (ORM) up to December 2022, in automatic and unattended mode.
The data analysis has been tested and improved also by comparison with the measurements of the nearly located AERONET...
The Cherenkov Telescope Array (CTA) is the next generation observatory of ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs). The observatory, currently under construction, will be composed of more than 70 telescopes at two locations: in the northern hemisphere, CTAO-N at the Observatorio del Roque de Los Muchachos (ORM, La Palma, Canary Islands, Spain), and in the southern...
The observations of a Raman Lidar at the Pierre Auger Observatory in the Argentinian Pampa are reported. The Raman Lidar is utilized for real-time atmospheric monitoring along the detection of cosmic-ray air showers. The vertical profiles of the water vapor mixing ratio, aerosol optical depth, and the aerosol backscatter are presented and discussed, for an observation time of 7 years...
As aerosols influence the optical transmission properties of the atmosphere, variations in atmospheric aerosols yield variations in the signals from extensive air-showers (EAS) measured with imaging atmospheric Cherenkov telescopes (IACTs).
With the optical transmission of the atmosphere affecting the amount of Cherenkov light reaching IACTs, wrongly accounted aerosol levels yield a...
The future Cherenkov Gamma Ray experiment CTA will reach a sensitivity and energy resolution never obtained until now by any other high energy gamma–ray experiment. Raman lidars can help reduce the systematic uncertainties of the molecular and aerosol components of the atmosphere so these performances can be reached. The motivation for Raman lidars and the design and development of the...
Recent developments for the atmospheric monitoring at the Pierre Auger Observatory will be presented. These developments include new methods for cloud identification, and a status of our suit of instruments for atmospheric monitoring and the application of these data to air shower physics.
The Imaging Atmospheric Cherenkov Telescopes observational technique employs the atmosphere as part of the detector, thus it is sensitive to all the changes taking place in it. Particularly, in the presence of clouds, the detector registers incomplete and degraded information caused by additional light absorption. Such observations are often rejected from further analysis process due to...
We present a novel method to determine the atmospheric transmission profile from the isotropic background events detected by the Imaging Atmospheric Cherenkov Telescopes. We construct a longitudinal distribution of the observed Cherenkov light by relating its emission height to a specific pixel in the camera. For this, we use a simple geometric model based on the parameters of the air shower....
The visibility of stars is often used for cloud detection using all-sky cameras, which have however only a limited reach and resolution near the horizon due to the lack of detectable stars. At the Pierre Auger Observatory, it is also used by the current generation of FRAM robotic telescopes, but – due to their limited field of view – only for a small number of selected showers. Thanks to the...
In the last ten years, the Pierre Auger Observatory has exploited a dedicated trigger and extended readout, and its very high time resolution, to record the world's largest sample of multiple ELVES. By comparing the time gaps between flashes with waveforms recorded by the antennas of the ENTLN network, we observe the correlation expected by models for what concerns double ELVES. On the...
The Airborne Lightning Observatory for FEGS and TGFs (ALOFT) campaign, conducted during the summer of 2023 on-board a NASA ER-2 research aircraft, investigated Terrestrial Gamma-ray Flashes (TGFs) and gamma-ray glows from thunderclouds over Central America, the Gulf of Mexico, and the Caribbean. Flying at an altitude of 20 km, the NASA ER-2 was equipped with an advanced scientific payload: a...
The Gamma-Flash program, funded by the Italian Space Agency (ASI) and led by the National Institute for Astrophysics (INAF), aims to study high-energy emissions related to thunderstorms, such as terrestrial gamma-ray flashes (TGFs) and gamma-ray glows. The program led to the development of two main detection systems: a ground-based system, installed at the “O. Vittori” Observatory on top of...
Over the past 15 years, the high-energy atmospheric physics group at the University of California, Santa Cruz, has developed and deployed instrumentation for the detection of TGFs on the ground and aboard aircraft. While the nature of this observing strategy is that far fewer events are observed than can be seen from spacecraft, with their very large (~600km radius) detection footprint, there...
Optical emissions linked to Terrestrial Gamma-ray Flashes (TGFs) have recently gained significance in both space-based and ground-based observations. These emissions are crucial in comprehending how TGFs are generated during thunderstorms. In this presentation, I will present the first time-resolved leader spectra of the optical component associated with downward TGFs, using a spectroscopic...
The Pierre Auger Observatory, designed to study ultra-high-energy cosmic rays, turned out to be a tremendous instrument for detecting and characterizing Terrestrial Gamma-ray Flashes (TGFs). In contrast to most TGF detections, which are almost exclusively from single locations, the vast array at the Auger Observatory yields upwards of 40 well spaced samples of the entire TGF footprint. As a...
Data from radio instruments are imperative to understanding the context of high-energy events in the atmosphere. Terrestrial gamma-ray flashes (TGFs) are extremely dynamic events that have several distinctive radio profiles in VLF including slow pulses (Pu et al. 2019) and energetic intracloud pulses (EIP; Lyu et al. 2021) in upward TGFs, both recently detected in association with downward...
The Naples observation station serves as a National Facility for the ACTRIS European network. In this frame, an innovative lidar system was recently made operational as part of the transportable atmospheric analysis equipment at the University of Naples "Federico II", located at CeSMA (Advanced Metrological and Technological Services Center).
The system is compact and transportable, using two...
The Cherenkov Telescope Array Observatory (CTAO) has set ambitious goals in terms of energy and angular resolution. Achieving these goals requires a detailed understanding of the atmosphere over the CTAO sites and the development of atmospheric calibration methods. In this contribution, we focus on the molecular atmosphere. We discuss ongoing efforts to estimate systematic uncertainties in...
Ground-based observations of Very-High-Energy (VHE) gamma rays from extreme astrophysical sources are significantly influenced by atmospheric conditions. This is due to the atmosphere being an integral part of the detector when observing with Imaging Air Cherenkov telescopes. Clouds and dust particles diminish atmospheric transmission, thereby impacting Cherenkov showers and the reconstructed...
The Observatorio del Roque de los Muchachos (ORM) will host the northern site of the Cherenkov Telescope Array Observatory, in an area about 200~m below the mountain rim, where the optical telescopes are located. The area hosts the MAGIC Telescopes, which have gathered a unique series of 20 years of weather data.
We use advanced profile likelihood methods to determine seasonal cycles, the...
