The pointing calibration of Imaging Atmospheric Cherenkov Telescopes (IACTs) is often a technological challenge: their cameras are not designed for imaging the stars in the Field of View (FoV) and this prevents from using the standard astrometry of the focal plane for monitoring the pointing of the instrument. A common solution is to adopt auxiliary optical devices aligned with the line-of-sight of the telescope but, in order to avoid systematic errors, a pointing strategy considering also the signal from the Cherenkov camera is desirable, especially when a dual-mirror optical configuration is adopted. In this contribution, we present a new custom astrometry technique that we developed for the Cherenkov camera of ASTRI telescopes, using the so-called Variance method: an ancillary output data-flow owning the possibility to image the stellar component of the Night Sky Background with relatively good sensitivity (limiting magnitude ∼7). Despite the large angular size of Cherenkov camera pixels (∼11 ′′) and their relatively small number (a few thousand), our automatic astrometric routine is able to identify the stars in the FoV with sub-pixel precision, giving the possibility of monitoring the pointing of the telescope in real-time, without any additional hardware. Our technique has been already tested on archive data taken with the ASTRI-Horn prototype telescope, located in Italy, and it will be implemented in the incoming ASTRI Mini-Array: a facility of 9 identical Cherenkov telescopes under construction in Tenerife (Canary Islands). In this contribution we discuss the features of this novel procedure, its potentialities, and how they will enhance the scientific accuracy of future ASTRI telescopes.
ASTRI-Horn is a small-sized Cherenkov telescope (SST) developed by the Italian National Institute of Astrophysics (INAF) for very-high energy gamma-ray astronomy. It is characterized by a dual-mirror optical system and a curved focal surface covered by SiPM sensors managed by a non-conventional fast front-end electronics. Installed in Italy at the INAF "M.C. Fracastoro" observing station (Mt. Etna, Sicily), ASTRI-Horn has been developed implementing a complete end-to-end approach that includes all aspects from the design, construction and implementation of the entire hardware and software system to the final scientific products. ASTRI-Horn is the prototype for nine SSTs that will form the ASTRI mini-array, considered by INAF as pathfinder for the Cherenkov Telescope Array (CTA). This phase will permit to exploit previous experimented technologies for the realization of the telescope structure and mirrors in a large production scale. After a short description of the major results obtained by the prototype in Serra La Nave, the proposed design of the new telescope structure and the status of the production of the optics are described. Moreover a review about the integration and alignment strategies to reach the required performance of the mini-array is reported.
ASTRI-Horn is a prototypal telescope of an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF), proposed for the Cherenkov Telescope Array (CTA) Observatory. The CTA Observatory represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very highenergy domain from a few tens of GeV up to few hundreds of TeV. It will be composed of large-, medium-, and small sized telescopes; ASTRI-Horn is an end-to-end prototype proposed for the Small Sized array.
The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon- Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system.
This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented.
The Cherenkov Telescope Array (CTA) foresees, in its southern site (Chile), the implementation of up to 70 small-sized telescopes (SSTs), which will extend the energy coverage up to hundreds of TeV. It has been proposed that one of the first set of CTA SSTs will be represented by the ASTRI mini-array, which includes (at least) nine ASTRI telescopes. The endto-end prototype of such telescopes, named the ASTRI SST-2M, is installed in Italy and it is now completing the overall commissioning and entering the science verification phase. ASTRI telescopes are characterized by an optical system based on a dual-mirror Schwarzschild-Couder design and a camera at the focal plane composed of silicon photomultiplier sensors managed by a fast read-out electronics specifically designed. Based on a custom peak-detector mode, the ASTRI camera electronics is designed to perform Cherenkov signal detection, trigger generation, digital conversion of the signals and data transmission to the camera server. In this contribution we will describe the main features of the ASTRI camera, its performance and results obtained during the commissioning phase of the ASTRI SST-2M prototype in view of the ASTRI mini-array implementation.
ASTRI SST-2M is an Imaging Atmospheric Cherenkov Telescope (IACT) developed by the Italian National Institute of Astrophysics, INAF. It is the prototype of the ASTRI telescopes proposed to be installed at the southern site of the Cherenkov Telescope Array, CTA. The optical system of the ASTRI telescopes is based on a dual mirror configuration, an innovative solution for IACTs, and the focal plane of the camera is composed of silicon photo-multipliers (SiPM), a recently developed technology for light detection, that exhibit very fast response and an excellent single photoelectron resolution. The ASTRI camera electronics is specifically designed to directly interface the SiPM sensors, detecting the fast pulses produced by the Cherenkov flashes, managing the trigger generation, the digital conversion of the signals and the transmission of the data to an external camera server connected through a LAN. In this contribution we present the general architecture of the camera electronics developed for the ASTRI SST-2M prototype, with special emphasis to some innovative solutions.
ASTRI is the end-to-end prototype for the CTA small-size class of telescopes in a dual-mirror configuration (SST-2M) proposed by the Italian National Institute of Astrophysics (INAF) in the framework of the Cherenkov Telescope Array. ASTRI SST-2M has been installed at the Serra La Nave Astrophysical Observatory on Mount Etna (Sicily) and its Performance Verification Phase will start in autumn 2016. For the relative pixel calibration and gain monitoring, the ASTRI SST-2M camera is equipped with an internal illumination device, while an external, portable, illumination system, placed at a few km distance from the telescope, will be used for the absolute end-to-end calibration of the telescope spectral response. Moreover analysis of signals induced in the camera pixels by the night sky background (diffuse emission and reference stars) will be used to monitor the long term evolution of the telescope calibration. We present an overview of the ASTRI SST-2M absolute calibration strategy and the external illuminating device that will be used for its spectral calibration
The purpose of this contribution is to present the current status of the software architecture of the ASTRI SST-2M Cherenkov Camera. The ASTRI SST-2M telescope is an end-to-end prototype for the Small Size Telescope of the Cherenkov Telescope Array. The ASTRI camera is an innovative instrument based on SiPM detectors and has several internal hardware components. In this contribution we will give a brief description of the hardware components of the camera of the ASTRI SST-2M prototype and of their interconnections. Then we will present the outcome of the software architectural design process that we carried out in order to identify the main structural components of the camera software system and the relationships among them. We will analyze the architectural model that describes how the camera software is organized as a set of communicating blocks. Finally, we will show where these blocks are deployed in the hardware components and how they interact. We will describe in some detail, the physical communication ports and external ancillary devices management, the high precision time-tag management, the fast data collection and the fast data exchange between different camera subsystems, and the interfacing with the external systems.
ASTRI SST-2M is the end-to-end prototype telescope under development by the Italian National Institute of Astrophysics, INAF, proposed for the investigation of the highest-energy gamma-ray band in the framework of the Cherenkov Telescope Array, CTA. The ASTRI SST-2M prototype will be installed in Italy at the INAF station located at Serra La Nave on Mount Etna during Fall 2014. The calibration and scientific validation phase will start soon after. The calibration of a Cherenkov telescope includes several items and tools. The ASTRI SST- 2M camera is equipped with an internal fiber illumination system that allows to perform the relative calibration through monitoring of gain and efficiency variations of each pixel. The absolute calibration of the overall system, including optics, will take advantage from auxiliary instrumentation, namely UVscope and UVSiPM, two small-aperture multi-pixels photon detectors NIST calibrated in lab. During commissioning phase, to measure the main features of ASTRI SST-2M, as its overall spectral response, the main telescope and the auxiliary UVscope-UVSiPM will be illuminated simultaneously by a spatially uniform flux generated by a ground-based light source, named Illuminator, placed at a distance of few hundreds meters. Periodically, during clear nights, the flux profiles of a reference star tracked simultaneously by ASTRI SST-2M and UVscope-UVSiPM will allow to evaluate the total atmospheric attenuation and the absolute calibration constant of the ASTRI SST-2M prototype. In this contribution we describe the auxiliary UVscope-UVSiPM and Illuminator sub-system together with an overview of the end-to-end calibration procedure foreseen for the ASTRI SST-2M telescope prototype.
In the context of the Cherenkov Telescope Array observatory project, the ASTRI SST-2M end-to-end prototype
telescope, entirely supported by the Italian National Institute of Astrophysics, is designed to detect cosmic primary
gamma ray energies from few TeV up to hundreds of TeV. The ASTRI SST-2M prototype camera is part of the
challenging synergy of novel optical design, camera sensors, front-end electronics and telescope structure design. The
camera is devoted to imaging and recording the Cherenkov images of air showers induced by primary particles into the
Earth’s atmosphere. In order to match the energy range mentioned above, the camera must be able to trigger events
within a few tens of nanoseconds with high detection efficiency. This is obtained by combining silicon photo-multiplier
sensors and suitable front-end electronics. Due to the characteristic imprint of the Cherenkov image that is a function of
the shower core distance, the signal dynamic range of the pixels and consequently of the front-end electronics must span
three orders of magnitude (1:1000 photo-electrons). These and many other features of the ASTRI SST-2M prototype
camera will be reported in this contribution together with a complete overview of the mechanical and thermodynamic
camera system.
The PICsIT (PIxelated CsI Telescope) instrument is the high energy plane of the IBIS imager onboard the INTEGRAL satellite. PICsIT consists of a 64x64 detector array, each composed of a CsI(Tl) scintillating crystal with p-i-n photodiode readout.
Since its first in-orbit activation, several extended tracks have been detected in its images, indicating the presence of frequent electromagnetic and hadronic showers initiated by primary cosmic rays.
In this paper we present the peculiar way the showers can form images in the PICsIT detector plane. We show also as the rejection of tracks events can be accomplished thanks to their peculiar geometrical and timing characteristics.
The IBIS instrument launched on board the ESA INTEGRAL observatory on October 2002 is a coded mask telescope composed by two position sensitive detection planes, one with 16384 Cadmium Telluride pixels (ISGRI) and the other with 4096 Caesium Iodide pixels (PICsIT).
Events detected in coincidence in the two detector layers are flagged as generated by Compton scattered photons and can be then processed and filtered using the Compton kinematic equations. The analysis of these data is, however, quite complex, mainly due to the presence of a great number of fake events generated by random coincidences between uncorrelated ISGRI and PICsIT events; if this component is not subtracted with great accuracy, false source detections can be produced.
In this work, we present the performance (spectral and imaging) obtainable from the IBIS Compton data, by analyzing ground calibration acquisitions. We also analyze the IBIS Compton flight data relative to the Crab observation, to determine its scientific capabilities.
The IBIS telescope is the high angular resolution Gamma-Ray imager on-board the ESA satellite INTEGRAL. The scientific goal of IBIS is to address, complemented by the high resolution spectrometer (SPI), astrophysical processes from celestial sources and diffuse regions in the X and Gamma-Ray domain. IBIS, with its Cadmium Telluride detector of 16.384 pixels and Caesium Iodide detector of 4.096 pixels, is an instrument with an high degree of complexity, whose status is continuously monitored by thousands of parameters (count rates, temperatures, voltages, instruments status, etc.), transmitted to ground by the periodic and non-periodic satellite telemetry housekeeping packets. In this paper we present the 'Ibis Parameters MONitor' (IPAMON), the real-time quick look software, part of the IBIS Experiment Check Out Equipment (ECOE), used during the on-ground functional and calibration campaign of the IBIS flight model carried out in LABEN (Milano) and ESTEC (ESA, Noordwijk). Due the high number of parameters, the software was designed to be flexible. In fact using the instrument data base as input for the internal structure configuration, the software is then insensitive to modifications that can occurs in the contents of the packet telemetry.
This capability allows IPAMON to be easily used for any other mission involving ESA packet structured telemetry.
The gamma-ray telescope IBIS, on Board the INTEGRAL satellite, is
expected to satisfy the mission's imaging objectives, by using two
position sensitive detection planes, one with 16384 Cadmium
Telluride pixels (ISGRI) at lower energies and the other with 4096
Caesium Iodide pixels (PICsIT) for higher energy detection. Given to the high complexity of the system, a dedicated Experiment Check Out Equipment (ECOE), was developed, capable not only to acquire, archive and monitor, the instrument data, but also to perform a fast data analysis, in order to deeply understand the instrument behavior in real-time. The system was used to support the IBIS Test and Calibration campaign campaigns, from the Engineering to the Flight model, and it will be used again during the Commissioning Phase, after
launch. We describe here, the architecture of the ECOE system and the
quick-look analysis tools that, with an user friendly graphical
interface, allows the user to analyze, in an easy way, both the
IBIS housekeeping and scientific data.
Reduction, subtraction and modeling of the in-flight background has been one of the main goal of the BeppoSAX high pressure gas scintillation proportional counter commissioning and science verification phase. In this paper we report studies of the observed in-orbit background.
The high pressure gas scintillation proportional counter, HPGSPC, was launched on April 30, 1996, as part of the narrow field instruments package of the satellite for x-ray astronomy BeppoSAX. Sensitive in the 4 - 100 keV band it fills the gap between the LECS, MECS and PDS instruments, making BeppoSAX a real wide band satellite. In the following paper we present performance and calibration results on in-flight energy response, spectral and timing capabilities, in-orbit background.
The high pressure gas scintillation proportional counter (HPGSPC) is one of the narrow field instruments onboard the Italian Dutch mission for x-ray astronomy SAX. Sensitive in the 4 - 120 keV band the HPGSPC will investigate all categories of astrophysical sources emitting in the not yet well studied hard x-ray domain with a special emphasis on the cyclotron line features that are present in the hard x-ray spectrum of many celestial sources. The on-ground calibration of the flight model of the HPGSPC was carried out at Laben, Italy during October/November 1994. In this paper after describing the flight model of the HPGSPC instrument, we report preliminary results on its spectral capabilities and background rejection efficiency.
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