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.
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 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 an instrument concept for the eXTP and STROBE-X space missions (although for the latter with a different name, HEMA). Based on linear Silicon Drift Detectors (SDD), it performs spectraltiming studies in the 2–30 keV energy range. Due to the harsh particle environment of low Earth orbit, it will be subject to radiation damage in the form of both displacement damage and Total Ionizing Dose (TID). To evaluate the response of the LAD sensor technology to TID, we exposed a prototype of a LAD detector to a 60Co source for a total of 85 kRad. This allowed us to evaluate the contribution of TID to the end-of-life performance of the instrument.
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.
Despite being a one-dimensional device by design, large-area linear Silicon Drift Detectors may exploit the diffusion of the charge cloud produced by an interacting photon to determine its two-dimensional impact position as well as its energy. Therefore, they can operate as spectral-imaging devices, which are particularly suitable for space-based X-ray coded-mask instruments, for which the trade-off between large collecting area, number of readout channels and spatial resolution is a challenge. We describe the experimental characterization of the photon reconstruction capabilities of a 169 μm anode-pitch large-area linear Silicon Drift Detector, whose technology is the foundation of the Wide Field Monitor camera of the eXTP, STROBE-X and LEM-X space missions.
The Large Area Detector is built around an array of linear Silicon Drift Detectors read out by dedicated CMOS Application-Specific Integrated Circuits. Strict constraints on power consumption and energy resolution (200 eV FWHM at 6 keV for single-channel events, ≤ 240 eV FWHM overall), impose a tough trade-off. We developed a new sensor architecture to improve the performance following two strategies: firstly by confining the signal charge diffusion during drift to a single channel, and secondly by focusing this charge to a smaller anode reducing the preamplifier’s noise contribution. Preliminary results show single-anode events increasing from 40% to > 94% for a best energy resolution of 219 eV FWHM at5.9 keV at 0 °C.
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.
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