Compton polarimeters are typically designed to be sensitive only to the azimuthal angle of the scattered photon, ignoring the scattering angle. Such a 2-dimensional reconstruction of the event is pursued for both simplicity and because the polarization of the incident photon influences only the azimuthal response of the instrument. While this is true for on-axis sources, when the source starts to be off-axis of several degrees the azimuthal response of the instrument is effectively a convolution of the azimuthal and polar scattering angles: measuring the latter would provide a better sensitivity and smaller systematic effects. In this contribution, we will present a design which allows to estimate the scattering angle in a Compton polarimeter through the read-out of the light signal at the two ends of scintillator bars. Such a design is being tested with a representative set-up and first results on the performance are presented.
The Technological and Scientific Pathfinders of the High Energy Rapid Modular Ensemble of Satellites (HERMES) are a constellation of low Earth orbit (LEO) novel CubeSats devoted to the monitoring of high energy sky. These 3U nanosatellites are equipped with miniaturized detectors specifically crafted for detecting bright high-energy transients, such as Gamma-Ray Bursts (GRBs). Their primary objective is to advance Gamma Ray Burst (GRB) science and improve the identification of Gravitational Wave (GW) electromagnetic counterparts. The overall localization performance of the constellation is directly related to the number of components and inversely proportional to the average baseline between them, therefore it is expected to improve with each new unit starting operation. This paper presents the design of the onboard scientific software that runs on the Payload Data Handling Unit (PDHU) on-board the HERMES missions. Besides serving as the main interface between the payload and the satellite bus, the PDHU manages the on-board control, monitoring and data acquisition of the HERMES detectors. This monitoring will emit a “trigger” alert when a transient is present in the data. In this work, we discuss the on-board data processing, particularly the trigger-performance. We showcase some results using flight hardware and software, albeit in a laboratory environment, and compare these results with simulated data.
The HERMES Technologic and Scientific Pathfinder will include a siswich detector, which is capable of performing spectroscopy in the range from 2 keV to 2 MeV as a single monolithic detector. To do this, the siswich combines a solid-state Silicon Drift Detector and a scintillator crystal. However, a spectroscopic calibration pipeline has not been standardized yet for these instruments. In this work, we present the newly developed HERMES calibration pipeline, mescal, which is intended for laboratory on-ground raw HERMES data energy calibration and formatting. This software is designed to minimize user interaction, thus including an automatic calibration line identification, and an automatic linear, independent calibration for each pixel in both operating modes. The mescal pipeline can set the basis for similar applications in future siswich telescopes.
The Space Industry Responsive Intelligent Thermal (SpIRIT) 6U CubeSat nano-satellite is an Australian mission with Italian partecipation for high-energy astrophysics. The 6U CubeSat carries an actively cooled detector system payload in a Sun-synchronous orbit. This payload unit is identical to the six that will fly onboard the High Energy Rapid Modular Ensemble of Satellites (HERMES) Technologic and Scientific Pathfinder ASI mission, hosting compact and innovative X-ray and gamma-ray detector for high energy transients localization (e.g., GRBs). SpIRIT was successfully launched on December 1, 2023 with a SpaceX Falcon 9, and the payload commissioning is in progress and about to be completed. This paper will provide an overview of the SpIRIT scientific payload early orbital operations, with the commissioning and in-flight calibrations of the instrument.
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.
KEYWORDS: Calibration, Space operations, Satellites, Data processing, Data archive systems, Open source software, Data centers, Data analysis, Astronomy, Gamma ray astronomy
HERMES Pathfinder is a constellation of six 3U nano-satellites mainly funded by the Italian Space Agency (ASI) and also by the European Union’s Horizon 2020 Research and Innovation Program. The nano-satellites host simple but innovative x-ray detectors to monitor cosmic high energy transients such as Gamma Ray Bursts (GRB). A seventh HERMES detector is aboard the Australian mission SpIRIT (Space Industry Responsive Intelligent Thermal), launched in December 2023. HERMES Science Operation Center (SOC) is hosted by the ASI Space Science Data Center (SSDC), which is a multi-mission science operation, data processing and data archiving center. The SOC is responsible for archiving, generating, validating, and distributing scientific and ancillary data, for quick-look analysis, mission planning, GRB trigger alerts, calibration data and data-analysis software. SSDC has developed specific pipelines to automatically perform each of the tasks under the responsibility of the SOC and the HERMESDAS (HERMES Data Analysis Software) software package to generate calibrated and cleaned scientific data from raw telemetry data. HERMESDAS is designed as a collection of software modules each dedicated to a single function. HERMEDAS makes use of open-source software, is designed for portability on most UNIX platforms, and adheres to NASA OGIP standards. HERMES science data archive will be accessible at www.asi.ssdc.it.
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 (high energy rapid modular ensemble of satellites) is a space-borne mission based on a constellation of six 3U CubeSats flying in a low-Earth orbit, hosting new miniaturized instruments based on a hybrid silicon drift detector/GAGG:Ce scintillator photodetector system sensitive to x-rays and γ-rays. Moreover, the HERMES constellation will operate in conjunction with the Australian-Italian space industry responsive intelligent thermal (SpIRIT) 6U CubeSat, that will carry in a sun-synchronous orbit (SSO) an actively cooled HERMES detector system payload. In this paper we provide an overview of the ground calibrations of the first HERMES and SpIRIT flight detectors, outlining the calibration plan, detector performance and characterization.
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