费米伽马射线太空望远镜（英语：Fermi Gamma-ray Space Telescope，缩写为LAT）是费米伽马射线太空望远镜（英语：Fermi Gamma-ray Space Telescope，缩写为Fermi）的主要仪器，是一个成像、宽视场、高能伽马射线望远镜，覆盖能量范围从20 MeV以下到300 GeV以上。本文介绍了LAT，其飞行前的预期性能，并总结了关键的科学目标，将解决。在轨性能将在随后的一篇论文中详细介绍。LAT是一个具有精密跟踪器和热量计的对转换望远镜，每个都由16个模块的4x 4阵列，覆盖跟踪器阵列的分段反符合探测器以及可编程触发器和数据采集系统组成。每个跟踪器模块具有18个x，y跟踪平面的垂直堆叠，每个托盘包括两层（x和y）单面硅条探测器和高Z转换器材料（钨）。每个量能器模块具有96个CsI（Tl）晶体，以8层的速端配置布置，总深度为8.6辐射长度。跟踪器的纵横比（高/宽）为0.4，允许大视场（2.4 sr）。LAT获得的数据旨在：（一）允许快速通知高能伽马射线暴（GRB）和瞬变，并促进对可变源的监测，（二）产生从全天巡天获得的数千个高能源的广泛目录，（三）测量数百个源的20 MeV至50 GeV以上的光谱，（iv）将点源定位到0.3 - 2角分，（v）绘制并获得扩展源（如SNR、分子云和附近星系）的光谱，（vi）测量高达TeV能量的弥散各向同性伽马射线背景，以及（vii）探索暗物质的发现空间。
英文摘要：
(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from below 20 MeV to more than 300 GeV. This paper describes the LAT, its pre-flight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4x4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 x,y tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an 8 layer hodoscopic configuration with a total depth of 8.6 radiation lengths. The aspect ratio of the tracker (height/width) is 0.4 allowing a large field-of-view (2.4 sr). Data obtained with the LAT are intended to (i) permit rapid notification of high-energy gamma-ray bursts (GRBs) and transients and facilitate monitoring of variable sources, (ii) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (iii) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (iv) localize point sources to 0.3 - 2 arc minutes, (v) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (vi) measure the diffuse isotropic gamma-ray background up to TeV energies, and (vii) explore the discovery space for dark matter.
Ultra-long gamma-ray bursts (ULGRBs) have very atypical durations of more than 2000 seconds. Even if their origins are discussed, the SVOM mission with its soft gamma-ray telescope ECLAIRs could detect ULGRBs and increase the sample of the few which have been detected so far by the Burst Alert Telescope aboard the Neil Gehrels Swift Observatory and some other instruments. In this paper, after a short description of the SVOM mission, we present methods developed to clean detector images from non-flat background and known source contributions in the onboard imaging process. We present an estimat…
Starting from 1960s, a great number of missions and experiments have been performed for the study of the high--energy sky. This review gives a wide vision of the most important space missions and balloon experiments that have operated in the 10--600 keV band, a crucial window for the study of the most energetic and violent phenomena in the Universe. Thus it is important to take the stock of the achievements to better establish what we have still to do with future missions in order to progress in this field, to establish which are the technologies required to solve the still open issues and to …
Hard X-/soft gamma-ray astronomy is a crucial field for transient, nuclear and multimessenger astrophysics. However, the spatial localization, imaging capabilities and sensitivity of the measurements are strongly limited for the energy range > 70 keV. To overcome these limitations, we have proposed a mission concept, ASTENA, submitted to ESA for its program Voyage 2050. We will report on a pathfinder of ASTENA, that we intend to propose to ASI as an Italian mission with international participation. It will be based on one of the two instruments aboard ASTENA: a Laue lens with 20 m focal length…
Gamma-Ray Integrated Detectors (GRID) mission is a student project designed to use multiple gamma-ray detectors carried by nanosatellites (CubeSats), forming a full-time all-sky gamma-ray detection network that monitors the transient gamma-ray sky in the multi-messenger astronomy era. A compact CubeSat gamma-ray detector, including its hardware and firmware, was designed and implemented for the mission. The detector employs four Gd2Al2Ga3O12 : Ce (GAGG:Ce) scintillators coupled with four silicon photomultiplier (SiPM) arrays to achieve a high gamma-ray detection efficiency between 10 keV and 2…
Despite over 50 years of Gamma-Ray Burst (GRB) observations many open questions remain about their nature and the environments in which the emission takes place. Polarization measurements of the GRB prompt emission have long been theorized to be able to answer most of these questions. The POLAR detector was a dedicated GRB polarimeter developed by a Swiss, Chinese and Polish collaboration. The instrument was launched, together with the second Chinese Space Lab, the Tiangong-2, in September 2016 after which it took 6 months of scientific data. During this period POLAR detected 55 GRBs as well a…
The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is designed to identify and characterize gamma rays from extreme explosions and accelerators. The main science themes include: supermassive black holes and their connections to neutrinos and cosmic rays; binary neutron star mergers and the relativistic jets they produce; cosmic ray particle acceleration sources including Galactic supernovae; and continuous monitoring of other astrophysical events and sources over the full sky in this important energy range. AMEGO-X will probe the medium energy gamma-ray band using a single inst…
Gamma-ray astronomy is a branch whose potential has not yet been fully exploited. The observations of elemental and isotopic abundances in supernova (SN) explosions are key probes not only of the stellar structure and evolution but also for understanding the physics that makes Type-Ia SNe as standard candles for the study of the Universe expansion properties. In spite of its crucial role, nuclear astrophysics remains a poorly explored field mainly for the typical emission lines intensity which are vanishing small and requires very high sensitivities of the telescopes. Furthermore, in spite tha…
We propose a fleet of nanosatellites to perform an all-sky monitoring and timing based localisation of gamma-ray transients. The fleet of at least nine 3U cubesats shall be equipped with large and thin CsI(Tl) scintillator based soft gamma-ray detectors read out by multi-pixel photon counters. For bright short gamma-ray bursts (GRBs), by cross-correlating their light curves, the fleet shall be able to determine the time difference of the arriving GRB signal between the satellites and thus determine the source position with an accuracy of $\sim10^\prime$. This requirement demands precise time s…
GRBAlpha is a 1U CubeSat mission with an expected launch date in the first half of 2021. It carries a 75 x 75 x 5 mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel photon counter (MPPC) setup, to detect gamma-ray bursts (GRBs). The GRB detector is an in-orbit demonstration for the detector system on the Cubesats Applied for MEasuring and LOcalising Transients (CAMELOT) mission. While GRBAlpha provides 1/8th of the expected effective area of CAMELOT, the comparison of the observed light curves with other existing GRB monitoring satellites will allow us to validate the core idea of…
Design of a mission to measure the shape and substructure of the 511 keV gamma-ray line from the center of the Milky Way
Washington University in St. Louis（华盛顿大学）；University of Colorado, Boulder（科罗拉多大学博尔德分校）；National Institute of Standards and Technology（美国国家标准与技术研究院）；University of New Hampshire（新罕布什尔大学）
Long Gamma Ray Bursts (LGRBs) can be used to address key questions on the formation of the modern universe including: How does the star formation rate evolve at high redshift? When and how did the intergalactic medium become re-ionized? What processes governed its early chemical enrichment? A LGRB signals when a massive star collapses to form a black hole and in doing so provides an independent tracer of the star formation rate. The LGRB afterglow is a bright back-light to view the host galaxy and intergalactic medium in absorption. The Gamow Explorer will be optimized to search for high redsh…
Aimed at progress in mega-electron volt (MeV) gamma-ray astronomy, which has not yet been well-explored, Compton telescope missions with a variety of detector concepts have been proposed so far. One of the key techniques for these future missions is an event reconstruction algorithm that is able to determine the scattering orders of multiple Compton scattering events and to identify events in which gamma rays escape from the detectors before they deposit all of their energies. We revisit previous event reconstruction methods and propose a modified algorithm based on a probabilistic method. Fir…
The e-ASTROGAM is a gamma-ray space mission to be proposed as the M5 Medium-size mission of the European Space Agency. It is dedicated to the observation of the Universe with unprecedented sensitivity in the energy range 0.2 - 100 MeV, extending up to GeV energies, together with a groundbreaking polarization capability. It is designed to substantially improve the COMPTEL and Fermi sensitivities in the MeV-GeV energy range and to open new windows of opportunity for astrophysical and fundamental physics space research. e-ASTROGAM will operate as an open astronomical observatory, with a core scie…
After the development of a BoGEMMS (Bologna Geant4 Multi-Mission Simulator) template for the back- ground study of X-ray telescopes, a new extension is built for the simulation of a Gamma-ray space mission (e.g. AGILE, Fermi), conceived to work as a common, multi-purpose framework for the present and future electron tracking gamma-ray space telescopes. The Gamma-ray extension involves the Geant4 mass model, the physics list and, more important, the production and treatment of the simulation output. From the user point of view, the simulation set-up follows a tree structure, with the main level…
In gamma-ray astronomy, a variety of data formats and proprietary software have been traditionally used, often developed for one specific mission or experiment. Especially for ground-based imaging atmospheric Cherenkov telescopes (IACTs), data and software are mostly private to the collaborations operating the telescopes. However, there is a general movement in science towards the use of open data and software. In addition, the next-generation IACT instrument, the Cherenkov Telescope Array (CTA), will be operated as an open observatory. We have created a Github organisation at https://github.c…
Long-duration gamma-ray burst (GRB) afterglow observations offer cutting-edge opportunities to characterise the star formation history of the Universe back to the epoch of reionisation, and to measure the chemical composition of interstellar and intergalactic gas through absorption spectroscopy. The main barrier to progress is the low efficiency in rapidly and confidently identifying which bursts are high redshift ($z > 5$) candidates before they fade, as this requires low-latency follow-up observations at near-infrared wavelengths (or longer) to determine a reliable photometric redshift estim…
A Multi-Mission Detection Framework for High-Energy Transients: Application to a 13-year Fermi/GBM and Swift/BAT Sample
Weizmann Institute of Science（魏茨曼科学研究所）；University of California at Santa Barbara（加州大学圣塔芭芭拉分校）；International Centre for Theoretical Sciences, Tata Institute of Fundamental Research（塔塔基础研究院国际理论科学中心）
PolPy: A universal tool for X-ray/gamma-ray polarimetry using common data format standards
Raman Research Institute（拉曼研究所）；NASA Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；University of Geneva（日内瓦大学）；Indian Institute of Technology Bombay（孟买印度理工学院）；INAF Istituto di Astrofisica e Planetologia Spaziali（意大利国家天体物理研究所空间与行星物理学所）；University of New Hampshire（新罕布什尔大学）
This paper explores the potential of AstroPix, a project to develop Complementary Metal Oxide Semiconductor (CMOS) pixels for the next generation of space-based high-energy astrophysics experiments. Multimessenger astrophysics is a rapidly developing field whose upcoming missions need support from new detector technology such as AstroPix. ATLASPix, a monolithic silicon detector optimized for the ATLAS particle detector at CERN, is the beginning of the larger AstroPix project. Energy resolution is a driving parameter in the reconstruction of gamma-ray events, and therefore the characterization …
CEA Paris-Saclay, Institut de Recherche sur les lois Fondamentales de l’Univers（法国原子能和替代能源委员会巴黎萨克雷中心基础定律研究所）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理重点实验室）；Aix Marseille Université, CNRS, CNES, LAM（艾克斯-马赛大学）；IRAP, Université de Toulouse, CNRS, CNES（图卢兹大学）；Université Paris Cité, CNRS, CEA, Astroparticule et Cosmologie（巴黎西岱大学）；Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris（索邦大学）
The Sino-French space mission SVOM is mainly designed to detect, localize and follow-up Gamma-Ray Bursts and other high-energy transients. The satellite, to be launched mid 2023, embarks two wide-field gamma-ray instruments and two narrow-field telescopes operating at X-ray and optical wavelengths. It is complemented by a dedicated ground segment encompassing a set of wide-field optical cameras and two 1-meter class follow-up telescopes. In this contribution, we describe the main characteristics of the mission and discuss its scientific rationale and some original GRB studies that it will enab…
THESEUS is a space mission concept, currently under Phase A study by ESA as candidate M5 mission, aiming at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. In addition to fully exploiting high-redshift GRBs for cosmology (pop-III stars, cosmic re-ionization, SFR and metallicity evolution up to the "cosmic dawn"), THESEUS will allow the identification and study of the electromagnetic counterparts to sources of gravitational waves which will be routinely detected in the late '20s / early …
e-ASTROGAM (`enhanced ASTROGAM') is a breakthrough Observatory mission dedicated to the study of the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. In the largely unexplored MeV-GeV domain, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their…
The Sino-French space mission SVOM (Space-based multi-band astronomical Variable Objects Monitor) is mainly designed to detect and localize Gamma-Ray Burst events (GRBs). The satellite, to be launched late 2021, embarks a set of gamma-ray, X-ray and optical imagers. Thanks to its pointing strategy, quick slew capability and fast data connection to earth, ground based observations with large telescopes will allow us to measure redshifts for an unprecedented sample of GRBs. We discuss here the overall science goals of the SVOM mission in the framework of the multi-wavelength and multi-messenger …
The Advanced Energetic Pair Telescope gamma-ray polarimeter uses a time projection chamber for measuring pair production events and is expected to generate a raw instrument data rate four orders of magnitude greater than is transmittable with typical satellite data communications. GammaNet, a convolutional neural network, proposes to solve this problem by performing event classification on-board for pair production and background events, reducing the data rate to a level that can be accommodated by typical satellite communication systems. In order to train GammaNet, a set of 1.1x10^6 pair prod…
SPHiNX is a proposed satellite-borne gamma-ray burst polarimeter operating in the energy range 50-500 keV. The mission aims to probe the fundamental mechanism responsible for gamma-ray burst prompt emission through polarisation measurements. Optimising the signal-to-background ratio for SPHiNX is an important task during the design phase. The Geant4 Monte Carlo toolkit is used in this work. From the simulation, the total background outside the South Atlantic Anomaly (SAA) is about 323 counts/s, which is dominated by the cosmic X-ray background and albedo gamma rays, which contribute ~60% and ~…
