arXiv subjects

P. Bruno

Publications and source records attributed to P. Bruno.

At least 19 recordsLinked to original sources

arXiv2026

Cassiopee: Defining the next-generation deformable mirror and high-speed SWIR camera for adaptive optics applications

Future adaptive optics (AO) systems for astronomy, optical communications, space situational awareness, and laser-based defense require a new generation of components operating at unprecedented speed, sensitivity, and precision. We present a systematic approach to defining the specifications of two key technologies: a large-format, high-cadence SWIR camera and a high-order deformable mirror (DM). Starting from four representative use-cases, high-contrast exoplanet imaging, free-space optical communications, satellite observation, and laser focusing, we derive detailed AO error budgets to identify the dominant performance drivers. This analysis defines quantitative requirements for the DM (actuator count, stroke, bandwidth, electronics) and the camera (read noise, quantum efficiency, frame rate, latency, and dark current), developed in close collaboration with industrial partners. We then describe an integrated experimental testbed designed to validate both components in a closed AO loop under atmospheric and system-level disturbances representative of astronomical and telecom applications. Finally, we outline the roadmap toward on-sky validation with EKARUS, the new AO facility at Asiago Observatory, bridging the gap between component qualification and deployment in future extremely large telescopes and ground-to-space optical links.

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arXiv2026

The Array Control and Data Acquisition software of the Cherenkov Telescope Array Observatory

The Cherenkov Telescope Array Observatory (CTAO) aims to advance knowledge of the gamma-ray sky as the largest gamma-ray observatory ever built. The CTAO will be deployed at two sites, one in the Northern Hemisphere and the other in the Southern Hemisphere, containing telescopes of three sizes to cover different energy domains. Commissioning of the prototype CTAO Large-Sized Telescope (LST-1) is being finalized at the northern site, while three additional LSTs are under construction. Additional calibration and environmental monitoring instruments, such as laser imaging detection and ranging (LIDAR) systems and weather stations, will support telescope operations. The Array Control and Data Acquisition (ACADA) system serves as the central element for on-site CTAO operations. ACADA controls, supervises, and handles the data generated by the telescopes and the auxiliary instruments. It drives the efficient planning and execution of observations while managing the multi-gigabit-per-second data streams produced by each CTAO telescope. The ACADA system contains the CTAO Science Alert Generation Pipeline - a real-time data processing and analysis pipeline, dedicated to automatically generating science alert candidates as data are acquired. These science alerts, along with external alerts received from other scientific instruments, are managed by the Transients Handler (TH) component. The TH informs ACADA's Short-Term Scheduler (STS) about relevant science alerts, enabling modification of ongoing observations on sub-minute timescales. This capability for rapid response, combined with the fast slewing of CTAO telescopes, makes the Observatory an excellent instrument for studying high-impact astronomical transients.

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arXiv2023

The CCD Controller and Detector

All the scientific instruments of the Italian National Telescope "Galileo" (TNG). as well as the tracking systems and the Shack-Hartmann wavefront systems use CCDs as detectors. The CCD procurement is crucial to optimize the instruments performance, and, of course, equal importance assumes the design and realization of controllers able to drive various kinds of CCDs with a very low readout noise. Detectors characterization is of fundamental importance when they have to be used in scientific instrumentation. Various CCDs have been assembled in cryostats and tested at our laboratory in order to select the suitable detector for the optical instruments of the TNG. The relevant phases of the group activity are here described, as well as the commissioning at the telescope and the work that is in progress.

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arXiv2023

OIG and Sarg CCD's characterization

CCDs characterization is the preliminary step to perform before the CCD can be properly used at the telescope. Most of the scientific instrumentation at the Italian National Telescope Galileo use CCDs as detectors. In particular the optical imager (OIG) and the high resolution spectrograph (SARG) use a mosaic of two 2k X 4k CCD manufactured by EEV (EEV 4280). The technical characteristics of the EEV4280 can be found in Cosentino et al (these proceedings).

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arXiv2023

The commissioning phase

In May 1997 a consistent part of the services and structures committed to the industry had already been released to the commissioning group. The telescope itself was, with the exception of the Nasmyth derotators, motors and all the optics groups, basically ready in its mechanical parts to accept the integration of all services and control equipment. Also the verification of the cabling (interlocks, data-nets, power and controls) already mounted was started in the same period. Starting from June 1998 (telescope first-light date) the telescope went gradually in use, several nights per week, in order to test and tune the tracking and pointing system, the optics and the first derotator system (Nasmyth A station). At the end of the commissioning period and with the first scientific instruments mounted (April 1999) also the first routinely observations started. In this moment the telescope is doing astronomy 80% of time and the complete first-light instrumentation is mounted.

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arXiv2023

SARG control system

The control system and the entire architecture of the High Resolution Spectrograph (SARG) for the Italian National Telescope "Galileo" (TNG) are here described. The concept of SARG instrument controls is similar to that of the other TNG instruments, in particular the CCD detector driving and the image acquisition use the same TNG standard boards and the same selected bus: the VME. The link between the SARG VME and the other telescope components is based on the same GATE software that guarantees the compatibility with the entire distributed TNG software. The control of the moving parts as well as the other parts of instrument that is the lamp controller and the temperature sensors, is based on a commercial controller connected to the system through a serial link. Furthermore a specialized software running on a PC has been realized to test the rotating tables independently of the VME system. Test of accuracy and repeatability of the positioning were done and some results are presented.

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arXiv2023

CCDs for the instrumentation of the Telescopio Nazionale Galileo

Most of the scientific instrumentation as well as the tracking systems and the Shack- Hartmann wavefront analysers at the Italian National Telescope Galileo use CCDs as detectors. The characterization of detectors is of fundamental importance for their correct utilization in scientific instrumentation. We report on the measurement of the electro-optical characteristics of CCDs that will be used in the scientific instrumentation at the Italian National Telescope. In particular we will show and compare the quantum e{\AE}ciency, the charge transfer e{\AE}ciency, the dark current, the read out noise the uniformity and the linearity of two sets of CCDs manufactured by EEV and LORAL. Finally, we will show the preliminary tests done at the telescope with the optical imager that has a mosaic of two EEV chips.

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arXiv2022

ASTRI Mini-Array Core Science at the Observatorio del Teide

The ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Project led by the Italian National Institute for Astrophysics (INAF) is developing and will deploy at the Observatorio del Teide a mini-array (ASTRI Mini-Array) composed of nine telescopes similar to the small-size dual-mirror Schwarzschild-Couder telescope (ASTRI-Horn) currently operating on the slopes of Mt. Etna in Sicily. The ASTRI Mini-Array will surpass the current Cherenkov telescope array differential sensitivity above a few tera-electronvolt (TeV), extending the energy band well above hundreds of TeV. This will allow us to explore a new window of the electromagnetic spectrum, by convolving the sensitivity performance with excellent angular and energy resolution figures. In this paper we describe the Core Science that we will address during the first four years of operation, providing examples of the breakthrough results that we will obtain when dealing with current open questions, such as the acceleration of cosmic rays, cosmology and fundamental physics and the new window, for the TeV energy band, of the time-domain astrophysics.

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arXiv2022

Extragalactic Observatory Science with the ASTRI Mini-Array at the Observatorio del Teide

The ASTRI Mini-Array is a next-generation system of nine imaging atmospheric Cherenkov telescopes that is going to be built at the Observatorio del Teide site. After a first phase, in which the instrument will be operated as an experiment prioritizing a schedule of primary science cases, an observatory phase is foreseen in which other significant targets will be pointed. We focus on the observational feasibility of extragalactic sources and on astrophysical processes that best complement and expand the ASTRI Mini-Array core science, presenting the most relevant examples that are at reach of detection over long-term time scales and whose observation can provide breakthrough achievements in the very-high energy extragalactic science. Such examples cover a wide range of $\gamma$-ray emitters, including the study of AGN low states in the multi-TeV energy range, the possible detection of Seyfert galaxies with long exposures and the searches of dark matter lines above 10 TeV. Simulations of the presented objects show that the instrument performance will be competitive at multi-TeV energies with respect to current arrays of Cherenkov telescopes.

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arXiv2022

Galactic Observatory Science with the ASTRI Mini-Array at the Observatorio del Teide

The ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Mini-Array will be composed of nine imaging atmospheric Cherenkov telescopes at the Observatorio del Teide site. The array will be best suited for astrophysical observations in the 0.3-200 TeV range with an angular resolution of few arc-minutes and an energy resolution of 10-15\%. A core-science programme in the first four years will be devoted to a limited number of key targets, addressing the most important open scientific questions in the very-high energy domain. At the same time, thanks to a wide field of view of about 10 degrees, ASTRI Mini-Array will observe many additional field sources, which will constitute the basis for the long-term observatory programme that will eventually cover all the accessible sky. In this paper, we review different astrophysical Galactic environments, e.g. pulsar wind nebulae, supernova remnants, and gamma-ray binaries, and show the results from a set of ASTRI Mini-Array simulations of some of these field sources made to highlight the expected performance of the array (even at large offset angles) and the important additional observatory science that will complement the core-science program.

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arXiv2022

Constraints on the structure and seasonal variations of Triton's atmosphere from the 5 October 2017 stellar occultation and previous observations

A stellar occultation by Neptune's main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. We aimed at constraining Triton's atmospheric structure and the seasonal variations of its atmospheric pressure since the Voyager 2 epoch (1989). We also derived the shape of the lower atmosphere from central flash analysis. We used Abel inversions and direct ray-tracing code to provide the density, pressure, and temperature profiles in the altitude range $\sim$8 km to $\sim$190 km, corresponding to pressure levels from 9 {\mu}bar down to a few nanobars. Results. (i) A pressure of 1.18$\pm$0.03 {\mu}bar is found at a reference radius of 1400 km (47 km altitude). (ii) A new analysis of the Voyager 2 radio science occultation shows that this is consistent with an extrapolation of pressure down to the surface pressure obtained in 1989. (iii) A survey of occultations obtained between 1989 and 2017 suggests that an enhancement in surface pressure as reported during the 1990s might be real, but debatable, due to very few high S/N light curves and data accessible for reanalysis. The volatile transport model analysed supports a moderate increase in surface pressure, with a maximum value around 2005-2015 no higher than 23 {\mu}bar. The pressures observed in 1995-1997 and 2017 appear mutually inconsistent with the volatile transport model presented here. (iv) The central flash structure does not show evidence of an atmospheric distortion. We find an upper limit of 0.0011 for the apparent oblateness of the atmosphere near the 8 km altitude.

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arXiv2021

UVscope and its application aboard the ASTRI-Horn telescope

UVscope is an instrument, based on a multi-pixel photon detector, developed to support experimental activities for high-energy astrophysics and cosmic ray research. The instrument, working in single photon counting mode, is designed to directly measure light flux in the wavelengths range 300-650~nm. The instrument can be used in a wide field of applications where the knowledge of the nocturnal environmental luminosity is required. Currently, one UVscope instrument is allocated onto the external structure of the ASTRI-Horn Cherenkov telescope devoted to the gamma-ray astronomy at very high energies. Being co-aligned with the ASTRI-Horn camera axis, UVscope can measure the diffuse emission of the night sky background simultaneously with the ASTRI-Horn camera, without any interference with the main telescope data taking procedures. UVscope is properly calibrated and it is used as an independent reference instrument for test and diagnostic of the novel ASTRI-Horn telescope.

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arXiv2020

Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $\gamma$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $\gamma$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of $\gamma$-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift $z=2$ and to constrain or detect $\gamma$-ray halos up to intergalactic-magnetic-field strengths of at least 0.3pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from $\gamma$-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of $\gamma$-ray cosmology.

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arXiv2020

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies. "Full likelihood tables complementing our analysis are provided here [ https://doi.org/10.5281/zenodo.4057987 ]"

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arXiv2019

First detection of the Crab Nebula at TeV energies with a Cherenkov telescope in a dual-mirror Schwarzschild-Couder configuration: the ASTRI-Horn telescope

We report on the first detection of very high-energy (VHE) gamma-ray emission from the Crab Nebula by a Cherenkov telescope in dual-mirror Schwarzschild-Couder (SC) configuration. The result has been achieved by means of the 4 m size ASTRI-Horn telescope, operated on Mt. Etna (Italy) and developed in the context of the Cherenkov Telescope Array Observatory preparatory phase. The dual-mirror SC design is aplanatic and characterized by a small plate scale, allowing us to implement large field of view cameras with small-size pixel sensors and a high compactness. The curved focal plane of the ASTRI camera is covered by silicon photo-multipliers (SiPMs), managed by an unconventional front-end electronics based on a customized peak-sensing detector mode. The system includes internal and external calibration systems, hardware and software for control and acquisition, and the complete data archiving and processing chain. The observations of the Crab Nebula were carried out in December 2018, during the telescope verification phase, for a total observation time (after data selection) of 24.4 h, equally divided into on- and off-axis source exposure. The camera system was still under commissioning and its functionality was not yet completely exploited. Furthermore, due to recent eruptions of the Etna Volcano, the mirror reflection efficiency was reduced. Nevertheless, the observations led to the detection of the source with a statistical significance of 5.4 sigma above an energy threshold of ~3 TeV. This result provides an important step towards the use of dual-mirror systems in Cherenkov gamma-ray astronomy. A pathfinder mini-array based on nine large field-of-view ASTRI-like telescopes is under implementation.

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arXiv2019

Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layout

The Cherenkov Telescope Array (CTA) is the major next-generation observatory for ground-based very-high-energy gamma-ray astronomy. It will improve the sensitivity of current ground-based instruments by a factor of five to twenty, depending on the energy, greatly improving both their angular and energy resolutions over four decades in energy (from 20 GeV to 300 TeV). This achievement will be possible by using tens of imaging Cherenkov telescopes of three successive sizes. They will be arranged into two arrays, one per hemisphere, located on the La Palma island (Spain) and in Paranal (Chile). We present here the optimised and final telescope arrays for both CTA sites, as well as their foreseen performance, resulting from the analysis of three different large-scale Monte Carlo productions.

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arXiv2019

SPHERE: the exoplanet imager for the Very Large Telescope

Observations of circumstellar environments to look for the direct signal of exoplanets and the scattered light from disks has significant instrumental implications. In the past 15 years, major developments in adaptive optics, coronagraphy, optical manufacturing, wavefront sensing and data processing, together with a consistent global system analysis have enabled a new generation of high-contrast imagers and spectrographs on large ground-based telescopes with much better performance. One of the most productive is the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE) designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE includes an extreme adaptive optics system, a highly stable common path interface, several types of coronagraphs and three science instruments. Two of them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared (NIR) range in a single observation for efficient young planet search. The third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to look for the reflected light of exoplanets and the light scattered by debris disks. This suite of three science instruments enables to study circumstellar environments at unprecedented angular resolution both in the visible and the near-infrared. In this work, we present the complete instrument and its on-sky performance after 4 years of operations at the VLT.

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arXiv2018

High-Contrast study of the candidate planets and protoplanetary disk around HD~100546

The nearby Herbig Be star HD100546 is known to be a laboratory for the study of protoplanets and their relation with the circumstellar disk that is carved by at least 2 gaps. We observed the HD100546 environment with high contrast imaging exploiting several different observing modes of SPHERE, including datasets with/without coronagraphs, dual band imaging, integral field spectroscopy and polarimetry. The picture emerging from these different data sets is complex. Flux-conservative algorithms images clearly show the disk up to 200au. More aggressive algorithms reveal several rings and warped arms overlapping the main disk. The bright parts of this ring lie at considerable height over the disk mid-plane at about 30au. Our images demonstrate that the brightest wings close to the star in the near side of the disk are a unique structure, corresponding to the outer edge of the intermediate disk at ~40au. Modeling of the scattered light from the disk with a geometrical algorithm reveals that a moderately thin structure can well reproduce the light distribution in the flux-conservative images. We suggest that the gap between 44 and 113 au span between the 1:2 and 3:2 resonance orbits of a massive body located at ~70au that might coincide with the candidate planet HD100546b detected with previous thermal IR observations. In this picture, the two wings can be the near side of a ring formed by disk material brought out of the disk at the 1:2 resonance with the same massive object. While we find no clear evidence confirming detection of the planet candidate HD100546c in our data, we find a diffuse emission close to the expected position of HD100546b. This source can be described as an extremely reddened substellar object surrounded by a dust cloud or its circumplanetary disk. Its astrometry is broadly consistent with a circular orbital motion on the disk plane.

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