HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder mission aims to observe and localize Gamma Ray Bursts (GRBs) and other transients using a constellation of nanosatellites in low-Earth orbit (LEO). Scheduled for launch in early 2025, the 3U CubeSats will host miniaturized instruments featuring a hybrid Silicon Drift Detector (SDD) and GAGG:Ce scintillator photodetector system, sensitive to X-rays and gamma-rays across a wide energy range. Each HERMES payload contains 120 SDD cells, each with a sensitive area of 45 mm2, organized into 12 matrices, reading out 60 12.1×6.94×15.0 mm3 GAGG:Ce scintillators. Photons interacting with an SDD are identified as X-ray events (2–60 keV), while photons in the 20–2000 keV range absorbed by the crystals produce scintillation light, which is read by two SDDs, allowing event discrimination. The detector system, including front-end and back-end electronics, a power supply unit, a chip-scale atomic clock, and a payload data handling unit, fits within a 10×10×10 cm3 volume, weighs 1.5 kg, and has a maximum power consumption of ∼2 W. This paper outlines the development of the HERMES constellation, the design and selection of the payload detectors, and laboratory testing, presenting the results of detector calibrations and environmental tests to provide a comprehensive status update of the mission.
HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder is a space-borne mission based on a constellation of six nano-satellites flying in a low-Earth orbit (LEO). The 3U CubeSats, to be launched in early 2025, host miniaturized instruments with a hybrid Silicon Drift Detector/GAGG:Ce scintillator photodetector system, sensitive to X-rays and gamma-rays in a large energy band. HERMES will operate in conjunction with Australian Space Industry Responsive Intelligent Thermal (SpIRIT) 6U CubeSat, launched in December 2023. HERMES will probe the temporal emission of bright high-energy transients such as Gamma-Ray Bursts (GRBs), ensuring a fast transient localization in a field of view of several steradians exploiting the triangulation technique. HERMES intrinsically modular transient monitoring experiment represents a keystone capability to complement the next generation of gravitational wave experiments. In this paper we outline the scientific case, development and programmatic status of the mission.
We describe the science case, design and expected performances of the X/Gamma-ray Imaging Spectrometer (XGIS), a GRB and transients monitor developed and studied for the THESEUS mission project, capable of covering an exceptionally wide energy band (2 keV – 10 MeV), with imaging capabilities and location accuracy <15 arcmin up to 150 keV over a Field of View of 2sr, a few hundreds eV energy resolution in the X-ray band (<30 keV) and few micro seconds time resolution over the whole energy band. Thanks to a design based on a modular approach, the XGIS can be easily re-scaled and adapted for fitting the available resources and specific scientific objectives of future high-energy astrophysics missions, and especially those aimed at fully exploiting GRBs and high-energy transients for multi-messenger astrophysics and fundamental physics.
HERMES (high energy rapid modular ensemble of satellites) is a space-borne mission based on a constellation of nano-satellites flying in a low-Earth orbit (LEO). The six 3U CubeSat buses host new miniaturized instruments hosting a hybrid silicon drift detector/GAGG:Ce scintillator photodetector system sensitive to x-rays and gamma-rays. HERMES will probe the temporal emission of bright high-energy transients such as gamma-ray bursts (GRBs), ensuring a fast transient localization (with arcmin-level accuracy) in a field of view of several steradians exploiting the triangulation technique. With a foreseen launch date in late 2023, HERMES transient monitoring represents a keystone capability to complement the next generation of gravitational wave experiments. Moreover, the HERMES constellation will operate in conjunction with the space industry responsive intelligent thermal (SpIRIT) 6U CubeSat, to be launched in early 2023. SpIRIT is an Australian-Italian mission for high-energy astrophysics that will carry in a sun-synchronous orbit (SSO) an actively cooled HERMES detector system payload. On behalf of the HERMES collaboration, in this paper we will illustrate the HERMES and SpIRIT payload design, integration and tests, highlighting the technical solutions adopted to allow a wide-energy-band and sensitive x-ray and gamma-ray detector to be accommodated in a 1U CubeSat volume.
HERMES Pathfinder (High Energy Rapid Modular Ensemble of Satellites Pathfinder) is a space mission based on a constellation of nano-satellites in a low Earth Orbit, hosting new miniaturized detectors to probe the X-ray temporal emission of bright high-energy transients such as Gamma-Ray Bursts and the electromagnetic counterparts of Gravitational Waves. This ambitious goal will be achieved exploiting at most Commercial offthe-shelf components. For HERMES-SP, a custom Power Supply Unit board has been designed to supply the needed voltages to the payload and, at the same time, protecting it from Latch-Up events.
The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) aiming at building and operating an array of nine Imaging Atmospheric Cherenkov Telescopes (IACTs) at the Observatorio del Teide in Tenerife (Canary Islands, Spain). UVSiPM, a calibrated small photon counter working in the 280-900 nm wavelength range, is one of the auxiliary instruments of the ASTRI Mini-Array.
UVSiPM is mainly devoted to measure the level of night sky background during the ASTRI Mini-Array observations in the same energy range of the ASTRI cameras. It is composed of one single multi-pixel SiPM sensor (the same model adopted in the ASTRI Mini-Array Cherenkov cameras) coupled to an electronic chain working in single photon counting mode. The design of the optical system foresees a pin-hole mask equipped with a collimator to regulate the UVSiPM field of view. UVSiPM will be mounted on the external structure of one of the ASTRI Mini-Array telescopes and co-aligned with its camera. In addition, it will be used as a support instrument for the absolute end-to-end calibration of the ASTRI Mini-Array telescopes performed with the illuminator, a further auxiliary device devoted to perform the optical throughput calibration of each telescope of the array. Last but not least, UVSiPM can be used as diagnostic tool for the camera functionalities. In this contribution we present the overall design of the UVSiPM instrument and some preliminary results of its performance based on simulations.
ASTRI-Horn is an imaging atmospheric Cherenkov telescope developed by the Italian National Institute for Astrophysics (INAF), installed at the Serra La Nave Astronomical Station on Mount Etna (Italy). ASTRI-Horn detected the Crab proving the validity of its innovative camera and of the dual mirror configuration. Henceforth the telescope will play another important role. It will be the test bench for the upcoming cameras to be adopted for the ASTRI Mini-Array, a project led by INAF to build and operate an array of nine Cherenkov telescopes at the Observatorio del Teide (Tenerife, Spain). Moreover, the ASTRI-Horn camera will be used to test new technological solutions and explore innovative Cherenkov observation techniques. The Cherenkov camera uses Silicon-Photo Multiplier (SiPM) detectors. The fast front-end electronics implemented in the CITIROC ASIC is based on a custom peak-detector mode, which measures the electric pulses generated by the Cherenkov light flashes. The compact camera embeds all the components of a reliable thermal cooling system. This contribution gives a description of the upgrades of the ASTRI-Horn camera, which are the results of the lesson learnt during these years of sky observations. The improvements aim at correcting the drawbacks detected so far and at increasing the overall performance of the camera. The main ones are the increment of the power supplied to the photodetectors, the redesign of the Lids kinematic chain, a more efficient embedded calibration system, new control software routines and GUI.
The ASTRI Mini-Array is a project led by INAF to construct nine Imaging Atmospheric Cherenkov Telescopes in order to study gamma-ray sources emitting up to the multi-TeV energy band. These telescopes, which will be deployed at the Observatorio del Teide (Tenerife, Spain), will be based on the prototype ASTRI-Horn telescope, successfully tested since 2014 at the Serra La Nave Astronomical Station of the INAF Observatory of Catania. Each telescope will be equipped with the new version of the ASTRI Silicon Photo-Multiplier (SiPM) Cherenkov Camera. In order to monitor and control the different subsystems, a Supervisory Control And Data Acquisition (SCADA) system will be developed to manage a set of software components. Among them, the Cherenkov Camera Supervisor (CCS), a software subsystem of the Telescope Control System (TCS), is the software component to control each Cherenkov Camera. It realizes the interface between each Camera and the central SCADA software through the Alma Common Software (ACS). Furthermore, the CCS is based on the Open Platform Communications - Unified Architecture (OPC-UA) standard, in order to realize a client/server system. The server side is implemented in the software subsystem deployed on board the Camera, while the CCS contains the client side which uses the server services. This work presents the design and the technologies used to implement the CCS. It describes architecture and functionalities starting from the definition of the use cases and the system requirements. Moreover, the work reports the various phases of the CCS development.
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.
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