The high-energy modular array (HEMA) is one of three instruments that compose the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) mission concept. The HEMA is a large-area, high-throughput non-imaging pointed instrument based on the large area detector (LAD) developed as part of the Large Observatory For X-ray Timing (LOFT) mission concept. It is designed for spectral timing measurements of a broad range of sources and provides a transformative increase in sensitivity to X-rays in the energy range of 2 to 30 keV compared with previous instruments, with an effective area of 3.4 m2 at 8.5 keV and an energy resolution of better than 300 at 6 keV in its nominal field of regard.
The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument designed for the eXTP (enhanced Xray Timing and Polarimetry) mission, a major project of the Chinese Academy of Sciences and China National Space Administration. The eXTP science case involves the study of matter under extreme conditions of gravity, density and magnetism. The eXTP mission is currently performing a phase B study, expected to be completed by the end of 2024. The target launch date is end-2029. Until recently, the eXTP scientific payload included four instruments (Spectroscopy Focusing Array, Polarimetry Focusing Array, Large Area Detector and Wide Field Monitor) offering unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The mission designed was however rescoped in early 2024 to meet the programmatic requirements of a final mission adoption in the context of the Chinese Academy of Sciences. Negotiations are still ongoing at agency level to assess the feasibility of a European participation to the payload implementation, by providing the LAD and WFM instruments, through a European Consortium composed of institutes from Italy, Spain, Austria, Czech Republic, Denmark, France, Germany, Netherlands, Poland, Switzerland and Turkey. At the time of writing, the LAD instrument is thus a scientific payload proposed for inclusion on eXTP. The LAD instrument for eXTP is based on the design originally proposed for the LOFT mission within the ESA-M3 context. The eXTP/LAD envisages a deployed >3 m2 effective area in the 2-30 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to 200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper we provide an overview of the LAD instrument design and the status of its maturity when approaching nearly the end of its phase B study.
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.
The Lunar Electromagnetic Monitor in X-rays (LEM-X) is a proposed observatory on the Moon surface for the detection of transients and the long-term monitoring of astrophysical sources across the whole observable sky in the 2 − 50 keV band. LEM-X is based on a compact and lightweight coded-aperture camera with a 2 sr field of view. The detector plane is composed of four individual alumina-based Detector Assemblies (DA), each one hosting a single large-area (∼ 7 × 7 cm2) linear Silicon Drift Detector (SDD), as well as 24 analog Application Specific Integrated Circuits (AFE ASICs), specifically developed for this project. High-voltage cables and a rigid-flex printed circuit board connect the DA to the back-end electronics and power supply. A breadboard featuring a 64-channel SDD and two AFE ASICs has been manufactured and is currently under test. The LEMX DA is being developed within the Earth-Moon-Mars project of the Italian National Recovery and Resilience Plan.
The Lunar Electromagnetic Monitor in X-rays (LEM-X) is a proposed lunar observatory for the study of high-energy transients. The fundamental components of the LEM-X instrument are pairs of coded aperture cameras, each sensitive in the 2−50 keV range and with a 2 sr field of view. In this paper, we present a trade-off analysis of the instrument layout, identify the optimal design, and characterize its performance in terms of sky exposure for multiple candidate landing sites. We first optimized the number and configuration of cameras and designed a concept of their support structure, to ensure complete and uniform sky coverage while minimizing complexity and volume. Then, by using NASA’s SPICE toolkit, simulations were carried out to assess the effective sky coverage of the proposed instrument configuration. We provide results for three landing site candidates on the Moon’s prime meridian, with latitudes 0°, −70° and −90°, laying the groundwork for future mission implementation studies.
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.
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.
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 Lunar Electromagnetic Monitor in X-rays (LEM-X) is an imager for X-ray Astronomy to be installed on the surface of the Moon, is funded by the Italian Ministero dell’Università e della Ricerca Scientifica and lead by the Istituto Nazionale di Astrofisica in the framework of the Italian “Piano Nazionale di Ripresa e Resilienza”. The building block of LEM-X is represented by a pair of coded aperture cameras, each one built around four large-area linear Silicon Drift Detectors and able to image the sky within a field of view of ~1 sr with a source location accuracy of ~1 arcmin, while at the same time reaching a spectral resolution better than 350 eV FWHM at 6 keV. The LEM-X instrument preliminarily envisages about seven such camera pairs, arranged on a dome-like structure on the surface of the Moon, to reach a sensitivity better than 5 mCrab in 50 ks and 1 Crab in 1 s in the 2 – 50 keV energy band. In this contribution we describe the design of LEM-X, we discuss the scientific performance and we report the status of the instrument development.
The Large Area Detector (LAD) is a narrow field-of-view instrument concept proposed for the eXTP X-ray space astronomy mission. With a substantial active area exceeding 3m2 at 8 keV, the LAD cannot rely on traditional grazing-incidence focusing X-ray optics. Instead, it uses an array of lightweight collimator plates matched to the sensors, employing lead-glass Micro-Pore Optics (MPO) technology to limit the field of view. To support the development of the LAD instrument, a dedicated X-ray facility was designed and constructed at the INAF-IAPS laboratories in Rome for the study and characterization of collimators. This facility is capable of measuring the collimator plates’ point-by-point angular response about different axes at several energies with an accuracy of 1′. Additionally, the facility includes a software pipeline that manages the measurements without constant user supervision, enabling thorough testing of large batches of collimator samples.
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.
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.
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.
The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument onboard the eXTP mission, a flagship mission of the Chinese Academy of Sciences and the China National Space Administration, with a large European participation coordinated by Italy and Spain. The eXTP mission is currently performing its phase B study, with a target launch at the end-2027. The eXTP scientific payload includes four instruments (SFA, PFA, LAD and WFM) offering unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The LAD instrument is based on the design originally proposed for the LOFT mission. It envisages a deployed 3.2 m2 effective area in the 2-30 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to 200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper we will provide an overview of the LAD instrument design, its current status of development and anticipated performance.
Within Quantum Gravity theories, different models for space-time quantisation predict an energy dependent speed for photons. Although the predicted discrepancies are minuscule, GRB, occurring at cosmological distances, could be used to detect this signature of space-time granularity with a new concept of modular observatory of huge overall collecting area consisting in a fleet of small satellites in low orbits, with sub-microsecond time resolution and wide energy band (keV-MeV). The enormous number of collected photons will allow to effectively search these energy dependent delays. Moreover, GrailQuest will allow to perform temporal triangulation of high signal-to-noise impulsive events with arc-second positional accuracies: an extraordinary sensitive X-ray/Gamma all-sky monitor crucial for hunting the elusive electromagnetic counterparts of GW. A pathfinder of GrailQuest is already under development through the HERMES project: a fleet of six 3U cube-sats to be launched by 2021/22.
The association of GW170817 with GRB170817A proved that electromagnetic counterparts of gravitational wave events are the key to deeply understand the physics of NS-NS merges. Upgrades of the existing GW antennas and the construction of new ones will allow to increase sensitivity down to several hundred Mpc vastly increasing the number of possible electromagnetic counterparts. Monitoring of the hard X-ray/soft gamma-ray sky with good localisation capabilities will help to effectively tackle this problem allowing to fully exploit multi-messenger astronomy. However, building a high energy all-sky monitor with large collective area might be particularly challenging due to the need to place the detectors onboard satellites of limited size. Distributed astronomy is a simple and cheap solution to overcome this difficulty. Here we discuss in detail dedicated timing techniques that allow to precisely locate an astronomical event in the sky taking advantage of the spatial distribution of a swarm of detectors orbiting Earth.
HERMES (High Energy Rapid Modular Ensemble of Satellites) Technological and Scientific pathfinder is a space borne mission based on a LEO constellation of nano-satellites. The 3U CubeSat buses host new miniaturized detectors to probe the temporal emission of bright high-energy transients such as Gamma-Ray Bursts (GRBs). Fast transient localization, in a field of view of several steradians and with arcmin-level accuracy, is gained by comparing time delays among the same event detection epochs occurred on at least 3 nano-satellites. With a launch date in 2022, HERMES transient monitoring represents a keystone capability to complement the next generation of gravitational wave experiments. In this paper we will illustrate the HERMES payload design, highlighting the technical solutions adopted to allow a wide-energy-band and sensitive X-ray and gamma-ray detector to be accommodated in a Cubesat 1U volume together with its complete control electronics and data handling system.
HERMES-TP/SP is a constellation of six 3U nano-satellites hosting simple but innovative X-ray detectors for the monitoring of Cosmic High Energy transients such as Gamma Ray Bursts and the electromagnetic counterparts of Gravitational Wave Events, and for the determination of their position. The projects are funded by the Italian Space Agency and by the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 821896. HERMES-TP/SP is an in orbit demonstration, that should be tested in orbit by the beginning of 2022. It is intrinsically a modular experiment that can be naturally expanded to provide a global, sensitive all sky monitor for high energy transients. On behalf of the HERMES-TP and HERMES-SP collaborations I will present the main scientific goals of HERMES-TP/SP, as well as a progress report on the payload, service module and ground segment developments.
HERMES (High Energy Rapid Modular Ensemble of Satellites) is an innovative mission aiming to observe transient high-energy events such as gamma-ray bursts (GRBs) through a constellation of CubeSats hosting a broadband X and gamma-ray detector. The detector is based on a solid-state Silicon Drift Detector (SDD) coupled to a scintillator crystal, and is sensitive in the 2 keV to 2 MeV band. An accurate evaluation of the foreseen in-orbit instrumental background is essential to assess the scientific performance of the experiment. An outline of the Monte Carlo simulations of the HERMES payload will be provided, describing the various contributions on the total background and the optimization strategies followed in the instrument design. Moreover, the simulations were used in order to derive the effective area and response matrices of the instrument, also as a function of the source location with respect to the detector frame of reference.
GAGG:Ce (Cerium-doped Gadolinium Aluminium Gallium Garnet) is a promising new scintillator crystal. A wide array of interesting features, such as high light output, fast decay times, almost non-existent intrinsic background and robustness, make GAGG:Ce an interesting candidate as a component of new space-based gamma-ray detectors. As a consequence of its novelty, literature on GAGG:Ce is still lacking on points crucial to its applicability in space missions. In particular, GAGG:Ce is characterized by unusually high and long-lasting delayed luminescence. This afterglow emission can be stimulated by the interactions between the scintillator and the particles of the near-Earth radiation environment. By contributing to the noise, it will impact the detector performance to some degree. In this manuscript we summarize the results of an irradiation campaign of GAGG:Ce crystals with protons, conducted in the framework of the HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites - Technological and Scientific Pathfinder) mission. A GAGG:Ce sample was irradiated with 70 MeV protons, at doses equivalent to those expected in equatorial and sun-synchronous LowEarth orbits over orbital periods spanning 6 months to 10 years, time lapses representative of satellite lifetimes. We introduce a new model of GAGG:Ce afterglow emission able to fully capture our observations. Results are applied to the HERMES-TP/SP scenario, aiming at an upper-bound estimate of the detector performance degradation due to the afterglow emission expected from the interaction between the scintillator and the nearEarth radiation environment.
Space radiation is well-known to pose serious issues to solid-state high-energy sensors. Therefore, radiation models play a key role in the preventive assessment of the radiation damage, duty cycles, performance and lifetimes of detectors. In the context of HERMES-SP mission we present our investigation of AE8/AP8 and AE9/AP9 specifications of near-Earth trapped radiation environment. We consider different circular Low-Earth orbits. Trapped particles fluxes are obtained, from which maps of the radiation regions are computed, estimating duty cycles at different flux thresholds. Outcomes are also compared with published results on in-situ measurements. This study is done on behalf of the HERMES-SP collaboration.
A software toolkit for the simulation of activation background for high energy detectors onboard satellites is presented on behalf of the HERMES-SP1 collaboration. The framework employs direct Monte Carlo and analytical calculations allowing computations two orders of magnitude faster and more precise than a direct Monte Carlo simulation. The framework was developed in a way that the model of the satellite can be replaced easily. Therefore the framework can be used for different satellite missions. As an example, the proton induced activation background of the HERMES CubeSat is quantified.
The HERMES-TP/SP mission, based on a nanosatellite constellation, has very stringent constraints of sensitivity and compactness, and requires an innovative wide energy range instrument. The instrument technology is based on the “siswich” concept, in which custom-designed, low-noise Silicon Drift Detectors are used to simultaneously detect soft X-rays and to readout the optical light produced by the interaction of higher energy photons in GAGG:Ce scintillators. To preserve the inherent excellent spectroscopic performances of SDDs, advanced readout electronics is necessary. In this paper, the HERMES detector architecture concept will be described in detail, as well as the specifically developed front-end ASICs (LYRA-FE and LYRA-BE) and integration solutions. The experimental performance of the integrated system composed by scintillator+SDD+LYRA ASIC will be discussed, demonstrating that the requirements of a wide energy range sensitivity, from 2 keV up to 2 MeV, are met in a compact instrument.
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