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.
The Enhanced X-ray Timing and Polarimetry (eXTP) mission is a flagship astronomy mission led by the Chinese Academy of Sciences (CAS) and scheduled for launch in 2029. The Large Area Detector (LAD) is one of the instruments on board eXTP and is dedicated to studying the timing of X-ray sources with unprecedented sensitivity. The development of the eXTP LAD involves a significant mass production of elements to be deployed in a significant number of countries (Italy, Austria, Germany, Poland, China, Czech Republic, France). This feature makes the Manufacturing, Assembly, Integration and Test (MAIT), Verification and Calibration the most challenging and critical tasks of the project. An optimized Flight Model (FM) implementation plan has been drawn up, aiming at a production rate of 2 Modules per week. This plan is based on the interleaving of a series of parallel elementary activities in order to make the most efficient use of time and resources and to ensure that the schedule is met.
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.
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.
The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow the study of the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. It is approved for a Phase B study. In this work, we report on the characterization of the Avalanche Photodiodes (APDs) that will be used as readout sensors of the absorption stage of the Compton polarimeter. We assessed the APDs gain and energy resolution as a function of temperature by irradiating the sensor with a 55Fe radioactive source. Moreover, the APDs were also characterized as being coupled to a GAGG scintillator.
The CUbesat Solar Polarimeter (CUSP) project aims to develop a constellation of two CubeSats orbiting the Earth to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter on board of each satellite. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures. CUSP is a project approved for a Phase B study by the Italian Space Agency in the framework of the Alcor program aimed to develop CubeSat technologies and missions. In this paper we describe the a method for a multi-physical simulation analysis while analyzing some possible design optimization of the payload design solutions adopted. In particular, we report the mechanical design for each structural component, the results of static and dynamic finite element analysis, the preliminary thermo-mechanical analysis for two specific thermal cases (hot and cold orbit) and a topological optimization of the interface between the platform and the payload.
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 CUbesat Solar Polarimeter (CUSP) project is a future CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band, by means of a Compton scattering polarimeter. CUSP will allow us to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. The project is in the framework of the Italian Space Agency Alcor Program, which aims to develop new CubeSat missions. CUSP is approved for a Phase B study that will last for 12 months, starting in mid-2024. We report on the current status of the CUSP mission project as the outcome of the Phase A.
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.
KEYWORDS: Monte Carlo methods, Polarimetry, Photons, X-rays, Solar radiation models, Solid modeling, Solar processes, Hard x-rays, Equipment, Compton scattering
The CUbesat Solar Polarimeter (CUSP) project is a CubeSat mission orbiting the Earth aimed to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures of our star. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed to develop new CubeSat missions. It is approved for a Phase B study. In this work, we report on the accurate simulation of the detector’s response to evaluate the scientific performance. A GEANT4 Monte Carlo simulation is used to assess the physical interactions of the source photons with the detector and the passive materials. Using this approach, we implemented a detailed CUSP Mass Model. In this work, we report on the evaluation of the detector’s effective area as a function of the beam energy.
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.
The eXTP (enhanced x-ray timing and polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS) and China National Space Administration (CNSA) currently performing a phase B study and proposed for a launch in 2027/2028.
The eXTP scientific payload envisages a suite of instruments offering unprecedented simultaneous wide-band x-ray timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study and it is expected to provide key hardware elements, including the large area detector (LAD) composed by 40 modules for a total effective area of 3.0 m2 at 6.0 keV.
In this paper we describe the design solutions adopted for the most important thermo-mechanical design drivers of the LAD module, which have been elaborated and used for the demonstration of compliance to the system requirements at spacecraft level. We report in particular the mechanical design for the module and its components, the results of static and dynamic finite element analysis of a simplified model and the preliminary thermal analysis for both a single detailed model and for a reduced model for all the 40 modules of the large area detector. We note that, in parallel to this activity, the LAD module design is being revised and optimized by the LAD consortium. Such design optimization is still ongoing and it is not reported in this paper.
The CubeSat solar polarimeter (CUSP) project aims to develop a constellation of two CubeSats orbiting the Earth to measure the linear polarisation of solar flares in the hard x-ray band by means of a Compton scattering polarimeter on board of each satellite. CUSP will allow to study the magnetic reconnection and particle acceleration in the flaring magnetic structures. CUSP is a project approved for a Phase A study by the Italian Space Agency in the framework of the Alcor program aimed to develop CubeSat technologies and missions.
The Pixelated silicon Drift Detector (PixDD) is a two-dimensional multi-pixel X-ray sensor based on the technology of Silicon Drift Detectors, designed to solve the dead time and pile-up issues of photon-integrating imaging detectors. Read out by a two-dimensional self-triggering Application-Specific Integrated Circuit named RIGEL, to which the sensor is bump-bonded, it operates in the 0:5 — 15 keV energy range and is designed to achieve single-photon sensitivity and good spectroscopic capabilities even at room temperature or with mild cooling (< 150 eV resolution at 6 keV at 0 °C). The paper reports on the design and performance tests of the 128-pixel prototype of the fully integrated system.
This paper assesses the response to radiation effects of the RIGEL, the Application Specific Integrated Circuit developed within the framework of the PixDD project, to be coupled with a multi-pixel sensor based on Silicon Drift Detectors for operation at the focal plane of X-ray optics on board space-borne astronomy missions. The campaign was conducted at the heavy ion beam line of the Radiation Effects Facility of the University of Jyvӓskylӓ (Finland): both the response to Single Event Effects (latch-ups and bit flips) and to Total Ionising Dose was evaluated. Experimental data were combined with simulations of the in-orbit environment for two scenarios: an equatorial and a Sun-synchronous orbit. The study demonstrated that the device can be safely operated on an equatorial orbit without any dedicated circuitry to mitigate Single Event Effects, although this precaution is instead advisable in the case of a Sun-synchronous orbit. Spectroscopic degradation resulting from Total Ionising Dose stays below 10% up to 34 krad, a manageable value for both orbital configurations.
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