This PDF file contains the front matter associated with SPIE Proceedings Volume 11444 including the Title Page, Copyright information, and Table of Contents.

SmallSats extend the frontiers of astrophysics, and present an opportunity with which to develop the next generation of scientists and engineers. Achieving high-impact research with SmallSats is increasingly feasible due to advances in technologies such as precision pointing, compact sensitive detectors and the miniaturization of propulsion systems. Science cases for SmallSat observatories (including CubeSats) being developed now include the discovery and characterization of exoplanets, stars, black holes and radio transients. SmallSats also represent a fantastic “on-ramp” to bring more people into mission development by providing opportunities for students and new PIs to get hands-on, end-to-end leadership, research and engineering experience. This combination of people development with new technology provides diverse opportunities to advance astrophysics knowledge.

We describe the radiometric performance and ground calibration results of the JUpiter ICy moons Explorer Ultraviolet Spectrograph (JUICE-UVS) instrument. JUICE-UVS is a modest power (8 W) ultraviolet spectrograph that is the fifth in a series of Alice/UVS instruments built by Southwest Research Institute. JUICE-UVS covers a 50-204 nm bandpass with 0.4 nm spectral resolution over a 7.5° field of view with better than 0.3° spatial resolution. JUICE-UVS also features three different observing modes to allow higher-than-nominal spatial resolution observing as well as solar occultations in the Jupiter system. JUICE-UVS meets all performance requirements with margin, and is the first planetary UV spectrograph to feature a microchannel plate detector with an atomic layer deposition (ALD) coating to minimize in-flight gain loss due to accumulated fluence. JUICE-UVS also features both a time-tagged pixel list observing mode and a programmable histogram mode to maximize observational flexibility and data management. During the main JUICE mission, JUICE-UVS will explore the atmospheres and surfaces of the Galilean satellites, examine the dynamics of Jupiter’s upper atmosphere from pole to equator, and investigate the Jupiter-Io connection through observations of the Io torus.

The Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission is an astrophysics Small Explorer employing ultraviolet spectroscopy (EUV: 80 – 825 Å and FUV: 1280 – 1650 Å) to explore the high-energy radiation environment in the habitable zones around nearby stars. ESCAPE provides the first comprehensive study of the stellar EUV and coronal mass ejection environments which directly impact the habitability of rocky exoplanets. In a 21 month science mission, ESCAPE will provide the essential stellar characterization to identify exoplanetary systems most conducive to habitability and provide a roadmap for future life-finder missions. ESCAPE accomplishes this goal with roughly two-order-of-magnitude gains in EUV efficiency over previous missions. ESCAPE employs a grazing incidence telescope that feeds an EUV and FUV spectrograph, building on experience with ultraviolet and X-ray instrumentation, grazing incidence optical systems, and photon-counting ultraviolet detectors. The instrument builds on design and hardware heritage from numerous NASA UV astrophysics, heliophysics, and planetary science missions. The ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace BCP-Smallspacecraft. Data archives are housed at the Mikulski Archive for Space Telescopes (MAST).

The Colorado Ultraviolet Transit Experiment (CUTE) is a 6U CubeSat designed to explore the upper atmospheres of short-period exoplanets via near-ultraviolet (2500 – 3300 Å) transmission spectroscopy, with an anticipated launch date of September 2021. The 4U science instrument comprises a Cassegrain telescope with a 20 × 8 cm primary mirror, a spectrograph, and a thermal-electrically cooled CCD detector. The spacecraft structure and a 1.5U XB1 avionics module are provided by Blue Canyon Technologies. CUTE’s novel and compact instrument design presents unique challenges to conducting component-level testing, alignment, instrument and spacecraft integration, calibration, and end-to-end performance testing. We provide a description of several custom test setups and procedures designed to characterize the spectrograph performance and its expected science return. We also outline the remainder of our integration and testing plan.

The CAFE (Census of warm-hot intergalactic medium, Accretion, and Feedback Explorer) and LyRIC (Lyman UV Radiation from Interstellar medium and Circum-galactic medium) have been proposed to the space agencies in China respectively. CAFE was first proposed as a joint scientific CAS-ESA small space mission in 2015. LyRIC was proposed as the independent external payload operating on the Chinese Space Station (CSS) in 2019. Both missions are dedicated to mapping the Lyman UV emissions ( ionized oxygen (O_VI) resonance lines at 103.2 and 103.8 nm, and Lyman series) for the diffuse sources either in our Galaxy or the circum-galactic mediums of the nearby galaxies. We present the primary science objectives, mission concepts, the enabling technologies, as well as the current status.

We report on the status of CETUS, an all-UV, Probe-class mission concept to be evaluated by the Astro2020 Steering Panel. This report expands and updates the scientific uses of CETUS and CETUS technology as described earlier by Kendrick et al. (2019). The major updates derive form technological advances that promise to make CETUS a scientifically more powerful and long-lived space observatory than originally proposed. A long, useful lifetime will be needed to fulfill the future needs of the astronomical and planetary-science community.

The INtegral Field Ultraviolet Spectroscopic Experiment (INFUSE) is a sounding rocket under sounding rocket under development by the Colorado Ultraviolet Spectroscopy Program (CUSP) at the University of Colorado. INFUSE will be the first far-ultraviolet (1000 - 2000 Å) integral field spectrograph in space and will have ˚ access to a portion of the Lyman ultraviolet (912 Å– 1216Å). This instrument leverages the development of ˚ enhanced lithium fluoride (eLiF) mirror coatings, which are roughly 30% more reflective than the conventional LiF+Al coatings used on previous missions. The integral field spectrograph is enabled by an 26-element image slicer precision machined by Canon Inc., with each element acting as a reflective long-slit. Each channel is re-focused and dispersed by one of 26 identical holographic gratings onto the same 94 x 94 mm XS MCP. This will be the largest cross-strip (XS) borosilicate microchannel plate detector yet deployed in space. INFUSE will spectroscopically image the XA region of the Cygnus Loop at the interface between the supernova and the ambient ISM. The first flight of INFUSE is projected for early 2023.

The Star-Planet Activity Research CubeSat (SPARCS) is a 6U CubeSat under construction that is devoted to the photometric monitoring of M stars in the far-UV (FUV) and near-UV (NUV), to measure the time-dependent spectral slope, intensity and evolution of low-mass star high-energy radiation. We report on the progress made in the assembly, integration and test of the instrument payload at Arizona State University using a custom TVAC chamber and optical stimulus that provides calibration light sources and the custom contamination control environment that the FUV demands. The payload consists of a custom 90mm clear aperture telescope developed by Hexagon/Sigma Space, combined with a dichroic plate to separate the FUV and NUV beams developed by Teledyne Acton and Materion, married with twin focal plane array cameras separately optimized for their bandpasses as developed by JPL.

The Star-Planet Activity Research CubeSat (SPARCS) will be a 6U CubeSat whose mission will be to observe M stars in two ultraviolet (UV) bands—SPARCS far UV (S-FUV: 153-171 nm) and SPARCS near UV (S-NUV: 260-300 nm). SPARCS would be the first mission to provide time-dependent spectral slope, intensity and evolution of M dwarf stellar radiation; measurements that are critical to deciphering observations of planetary atmosphere from missions such as JWST. The baseline UV camera for SPARCS (SPARCam) includes the electronics boards and two UV detectors, one optimized for each of the SPARCS bands. The camera’s low-noise electronics are based on JPL’s compact, modular design and provide dynamic observation capabilities. For its detectors, SPARCam uses 2D-doped (i.e. delta-doped) CCDs for both channels. Here we present SPARCam development and characterization results prior to payload integration. Copyright 2019. All rights reserved.

SUAVE (Solar Ultraviolet Advanced Variability Experiment) is a far UV imaging solar telescope (Lyman Alpha, 121.6 nm, Herzberg continuum, 200-242 nm, etc.) of novel design (off-axis telescope with "mushroom type" SiC mirrors) for ultimate thermal stability and long lasting performances over years instead of, often, a few weeks or months in this wavelength range. SUAVE has no entrance window for long and uncompromising observations in the UV (no coatings of mirrors, flux limited to less than 2 solar constants on filters to avoid their degradation), associated with an ultimate thermal control (no central obscuration resulting in limited thermal gradients and easier heat evacuation, focus control, stabilization). Design and anticipated performances will be detailed as well as results of representative thermal/optical tests performed on the SiC primary mirror and support regulated plate (SiC also). SUAVE is the main instrument of the Solar/Climate SoSWEET-SOUP constellation mission.

All reflective spatial heterodyne spectrometers (SHS) are a compact self-scanning Fourier transform spectrometer (FTS) device capable of providing line-resolved measurements of wide-field emissions at far greater sensitivity than existing echelle- based instruments at large telescopes. Their use of reflective optical components further enables their use in UV, particularly at wavelengths below 160 nm where options for transmitting elements are few or non-existent. We have been developing advanced prototype SHS instruments that are optimized to provide single-line and broadband performance in the UV. These prototypes do not require large telescopes to achieve sensitivity and are sufficiently compact that can be incorporated in the SmallSat and robotic probes. In this presentation I will describe the basic functionality of the SHS, our previous development, and the progress toward flight-ready instruments that can be incorporated into future mission concepts. All reflective spatial heterodyne spectrometers (SHS) are a compact self-scanning Fourier transform spectrometer (FTS) device capable of providing line-resolved measurements of wide-field emissions at far greater sensitivity than existing echelle- based instruments at large telescopes. Their use of reflective optical components further enables their use in UV, particularly at wavelengths below 160 nm where options for transmitting elements are few or non-existent. We have been developing advanced prototype SHS instruments that are optimized to provide single-line and broadband performance in the UV. These prototypes do not require large telescopes to achieve sensitivity and are sufficiently compact that can be incorporated in the SmallSat and robotic probes. In this presentation I will describe the basic functionality of the SHS, our previous development, and the progress toward flight-ready instruments that can be incorporated into future mission concepts.

The Institute for Astronomy and Astrophysics in Tübingen (IAAT) has a long-term experience in developing and building space-qualified imaging and photon counting microchannel-plate (MCP) detectors, which are sensitive in the ultraviolet wavelength range. Our goal is to achieve high quantum efficiency and spatial resolution, while maintaining solar blindness and low-noise characteristics. Our flexible detector design is currently tailored to the specific needs of three missions: For the ESBO DS (European Stratospheric Balloon Observatory – Design Study) we provide a sealed detector to the STUDIO instrument (Stratospheric Ultraviolet Demonstrator of an Imaging Observatory), a 50 cm telescope with a UV imager for operation at an altitude of 37-41 km. In collaboration with the Indian Institute of Astrophysics we plan a space mission with a CubeSat-sized farultraviolet spectroscopic imaging instrument, featuring an open version of our detector. A Chinese mission, led by the Purple Mountain Observatory, comprises a multi-channel imager using open and sealed detector versions. Our MCP detector has a cesium activated p-doped gallium-nitride photocathode. Other photocathode materials like cesium-telluride or potassium-bromide could be used as an alternative. For the sealed version, the photocathode is operated in semi-transparent mode on a MgF₂ window with a cut-off wavelength of about 118 nm. For missions requiring sensitivity below this cut-off, we are planning an open version. We employ a coplanar cross-strip anode and advanced low-power readout electronics with a 128-channel charge-amplifier chip. This publication focuses on the progress concerning the main development challenges: the optimization of the photocathode parameters and the sophisticated detector electronics.

Many Earth-sized planets have been discovered and some of them are potentially in the habitable zone. In addition, several Earth-sized planets have been detected around low temperature stars near our solar system. However, it is difficult to characterize them as Earth-like or Venus-like, even though they are relatively very close to our solar system. We performed a conceptual design of an Ultraviolet Spectrograph for Exoplanet (UVSPEX) for World Space Observatory Ultraviolet (WSO-UV), which is 1.7-m UV space telescope being prepared by Russia. The spectral range is to exceed wavelengths from 115 nm to 135 nm to detect at least H Lyman alpha 121.6nm to O I 130 nm. The throughput is >4%. UVSPEX is planned to be a part of a Field Camera Unit (FCU). This additional instrument would enable us to observe ~20 Earth-like exoplanets and detect an oxygen exosphere if some of them have an Earth-like atmosphere.

Solar-C (EUVST) is the next Japanese solar physics mission to be developed with significant contributions from US and European countries. The mission carries an EUV imaging spectrometer with slit-jaw imaging system called EUVST (EUV High-Throughput Spectroscopic Telescope) as the mission payload, to take a fundamental step towards answering how the plasma universe is created and evolves and how the Sun influences the Earth and other planets in our solar system. In April 2020, ISAS (Institute of Space and Astronautical Science) of JAXA (Japan Aerospace Exploration Agency) has made the final down-selection for this mission as the 4th in the series of competitively chosen M-class mission to be launched with an Epsilon launch vehicle in mid 2020s. NASA (National Aeronautics and Space Administration) has selected this mission concept for Phase A concept study in September 2019 and is in the process leading to final selection. For European countries, the team has (or is in the process of confirming) confirmed endorsement for hardware contributions to the EUVST from the national agencies. A recent update to the mission instrumentation is to add a UV spectral irradiance monitor capability for EUVST calibration and scientific purpose. This presentation provides the latest status of the mission with an overall description of the mission concept emphasizing on key roles of the mission in heliophysics research from mid 2020s.

We present ongoing efforts on the development of precision Wolter mirrors for the Soft X-ray Imaging Spectrometer (SXIS) aboard PhoENiX mission proposed to JAXA for studying mechanism(s) of particle acceleration and its relationship with magnetic reconnection in solar flares. The Wolter mirrors for PhoENiX/SXIS are made by direct polishing of glass-ceramic substrates. So far, we succeeded in fabricating a small size of high precision Wolter surfaces (e.g., PSF core size of ~0.2 arcsec HPD at 8 keV) as well as good indication of extending the mirror area along the cylindrical direction. Recent status of the mirror development will be reported.

The Wide Field Imager (WFI) instrument for ESA’s next large X-ray mission Athena is designed for imaging and spectroscopy over a large field of view, and high count rate observations up to and beyond 1 Crab source intensity. The other focal plane instrument, the cryogenic X-IFU camera, is designed for high-spectral resolution imaging. Both cameras share alternately a mirror system based on silicon pore optics with a focal length of 12 m and unprecedented large effective area of about 1.4 m² at 1keV. The WFI instrument employs DEPFET active pixel sensors, which are fully depleted, back-illuminated silicon devices of 450 μm thickness. The detectors provide high quantum efficiency and state-of-the art energy resolution in the 0.2 keV to 15 keV energy range with extremely fast readout speeds compared to previous generations of Si detectors for X-ray astronomy. The focal plane comprises a Large Detector Array (LDA) and a Fast Detector (FD). The LDA comprises about 1 million pixels and a time resolution in full frame mode of 5 ms. The FD optimized for bright point source observations permits a time resolution of even 80 μs with about 4000 pixels. Both detectors have a pixel size of 130 μm × 130 μm, providing oversampling of the PSF by a factor >2. The instrument development is in phase B of the project after a successful Preliminary Requirements Review and endorsement of the both instrument consortia by ESA. Critical technology developments for the WFI focal plane camera are currently investigated and finally experimentally verified with breadboard models: the detector function and performance, the real-time capability of onboard event pre-processing and the integrity of the large-area and ultra-thin optical blocking filter after environmental tests. Flight-size sensors have been produced and a flight-like detector assembly has been developed. First test results of a flight-size detector are expected in near future. Based on the thermal design and model for the camera head (CH), thermal interface requirements have been estimated.

The X-ray Integral Field Unit (X-IFU) will be the cryogenic X-ray spectro-imager of the ESA Athena space observatory. It will implement a matrix of 3168 superconducting Transition Edge Sensors at 90 mK to provide a very high spectral resolution of 2.5 eV up to the energy of 7 keV, across a 5’ large field of view. The X-IFU successfully passed its Preliminary Requirements Review in mid-2019. After providing an overview of the driving science cases, the key requirements, I will present a status on the instrument development.

This paper describes the fabrication- and integration process of the X ray Integral Field Unit Focal Plane Assembly (X-IFU FPA) Development Model (DM) as part of the ongoing FPA development program for the Athena X-ray observatory. The build of this FPA-DM is a first demonstration for the X-IFU focal plane, which contains all these elements while the design is aimed for space application rather than for laboratory environment. In this paper we present the FPA-DM integration process including relevant tests on sub-system level. In addition the latest status of the warm- and cryogenic FPA-DM test program is presented. This test program, which is planned to start in 2020, includes thermal-, mechanical- and functional and performance tests. A comparison between the available test results and the thermal- and mechanical- models is made.

CNES (French Space Agency) is in charge of the development of the X-IFU instrument for Athena. The main sensor array detection chain sub-system of the X-IFU instrument is one of the major sub-subsystem of the instrument, as the main contributor to the performance. This sub-system involves major partners of the X-IFU instrument, e.g GFSC, SRON, VTT, APC, and IRAP. The purpose of this paper is to present the baseline of the definition of the X-IFU detection chain in the frame at end of phase A/beginning of phase B. The readout is based on Time Domain Multiplexing (TDM). There are strong design issues which couple the different sub-components of the detection chain (the main sensor array, the cold electronics stages, and the warm electronics). The detection chain environment (thermal, mechanical and EMI/EMC environment) also requires a transverse analysis. This paper focuses on those aspects while providing design description of the sub-components of the detection chain.

We are developing Frequency Domain Multiplexing (FDM) read-out of Transition-Edge Sensors (TESs) for the X-ray Integral Field Unit (X-IFU) on board of the future European X-Ray observatory Athena. The X-IFU Focal-Plane Assembly consists of a $sim$ 3000-pixel array, read out by SQUID-based FDM. The multiplexing readout scheme is a critical technology for the X-IFU instrument because of the cooling and electronic power limits for the satellite. In this contribution, we report on the development of FDM readout technology and on the performance of TESs array under an AC bias at MHz frequencies.

We intoduce our novel method of super high resolution astronomical X-ray imaging, Multi Image X-ray Interferometer Method, Modules, Missions (MIXIM). In series of experiments on the ground we not only verified the concept of MIXIM but also realized 2D imaging with angular resolution better than 0. ′′1. Employment of small pixel size CMOS sensor was the key to this achievement. Scalability is also an important feature of MIXIM., and various mission format is available. We show some examples from a very small satellite for sub arcsecond resolution to a formation flight with a millions km separation to gain µas resolution. MIXIM is different from X-ray mirrors in various points, for example, it does not have a collecting power. Considering the limitations and advantages of MIXIM, we should choose bright apparently point-like sources as targets. Nearby AGNs are primary ones, and the MIXIM scope just corresponds to spatial scales which have not yet resolved in X-rays.

We have proposed a new style X-ray interferometer, Multi-Image X-ray Interferometer Module (MIXIM), to achieve high angular resolution. MIXIM is comprised of a grating and an X-ray detector, and its angular resolution is in inverse proportion to the distance between two components. Although we have already detected a 1D interference fringe which corresponds an angular resolution of about 1” in our past experiment, its amplitude is not so high partly because of the lack of the spatial resolution of the X-ray detector. Then we newly adopt a CMOS detector which has both high spatial resolution (< 2.5 μm) and high spectroscopic capability (FWHM∼ 170 eV @5.9 keV) and evaluate the performance of MIXIM at BL20B2 in SPring-8, the synchrotron radiation facility in Japan. 1D interference fringes in this experiment have much higher amplitudes than those in the past experiment, which demonstrates the improvement of the performance due to the new CMOS detector. We also introduce a 2D grating for the first time, and try to obtain the 2D profile of the X-ray beam of which the size is 0.28” (H) and 0.06” (V). Extending the distance between two components to 866.5 cm, 2D imaging by MIXIM succeeds in capturing the horizontally elongated beam structure. The angular resolution at this configuration is calculated to be 0.076”, which is the highest ever achieved for astronomical X-ray imagers.

We have proposed the development of X-ray interferometry as part of ESA’s Voyage 2050 programme, to reveal the universe at high energies with ultra-high spatial resolution. With only a 1 m baseline, which could be accommodated on a single spacecraft, X-ray interferometry can reach 100 μas resolution at 10 Å (1.24 keV) and exceed that of the Event Horizon Telescope at 2Å (6.2 keV). A multi-spacecraft ‘constellation’ interferometer would resolve well below 1 μas. Here we focus on the single-spacecraft interferometer design and discuss the process of fringe detection and image reconstruction from multiple baselines, showing simulated images of test cases from our Voyage 2050 White Paper. We also discuss the challenges and feasibility of reaching the technical requirements needed for a single-spacecraft interferometer. Most key requirements are already feasible or within easy reach. Besides a ground-based testbed, covered elsewhere in these proceedings, the most important areas for development include large format, small-pixel X-ray detectors and pointing which is stable or can be reconstructed to tens of µas precision.

We present a novel nested-shell Wolter x-ray telescope design that can achieve diffraction-limited performance over the entire telescope aperture. The new design features a compact single-spacecraft mirror assembly, similar in form to that proposed for Lynx, and a separate detector spacecraft. A wide range of design parameter space was considered. We present a specific example which features 10 micro-arcsec resolution, a wide band (0.1-10 keV) with > 2 m2 effective area out to 10 keV, a large flat field (>1010 pixels), achieving diffraction-limited performance (Strehl ratio > 0.8). We will also briefly discuss a potential science case for this telescope.

For many years, Wolter mirrors have been used as imaging elements in X-ray telescopes. The shape error of Wolter mirrors fabricated by replicating the shape of a mandrel originates from the replication error in electroforming. We have been developing an X-ray focusing mirror for synchrotron radiation X-rays, as well as a high-precision electroforming process. In this paper, we report on the application of the advanced electroforming process to the fabrication of Wolter mirrors for the FOXSI Sun observation project. We also discuss the figuring accuracy of the mandrel.

High-resolution (R = λ/Δλ >2000) x-ray absorption and emission line spectroscopy in the soft x-ray band is a crucial diagnostic for the exploration of the properties of ubiquitous warm and hot plasmas and their dynamics in the cosmic web, galaxy clusters, galaxy halos, intragalactic space, and star atmospheres. Soft x-ray grating spectroscopy with R > 10,000 has been demonstrated with critical-angle transmission (CAT) gratings. CAT gratings combine the relaxed alignment and temperature tolerances and low mass of transmission gratings with high diffraction efficiency blazed in high orders. They are an enabling technology for the proposed Arcus grating explorer and were selected for the Lynx design reference mission grating spectrometer instrument. Both Arcus and Lynx require the manufacture of hundreds to perhaps ≈ 2000 large-area CAT gratings. We are developing new patterning and fabrication process sequences that are conducive to large-format volume processing on stateof-the-art 200 mm wafer tools. Recent x-ray tests on 200 nm-period gratings patterned using e-beam-written masks and 4x projection lithography in conjunction with silicon pore focusing optics demonstrated R ≈ 104 at 1.49 keV. Extending the grating depth from 4 μm to 6 μm is predicted to lead to significant improvements in diffraction efficiency and is part of our current efforts using a combination of deep reactive-ion etching and wet etching in KOH solution. We describe our recent progress in grating fabrication and report our latest diffraction efficiency and modeling results.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a Chinese – French satellite mission due to be launched in the summer of 2022. It is composed of four instruments: ECLAIRs, for detecting X-ray and gamma-ray transients (4-250 keV); GRM, a gamma-ray spectrometer (15 keV-5 MeV); VT, a visible telescope and the Microchannel X-ray Telescope (MXT). The MXT’s main goal is to precisely localize, and spectrally characterize X-ray afterglows of Gamma-Ray Bursts. The MXT is a narrow-field-optimised lobster eye X-ray focusing telescope comprising an array of 25 square Micro Pore Optics (MPOs), with a detectorlimited field of view of ∼1 square degree, working in the energy band 0.2-10 keV. The SVOM qualification model (QM) MXT optic (MOP) was designed and built at the University of Leicester, and is the first complete, lobster eye optic to be X-ray tested. We present results from the PANTER facility (MPE), where a full calibration of the QM MOP was carried out. The response of the optic was studied at seven energies from C-K to Cu-K, and the effective area at multiple off-axis angles at each energy was measured. The focal length of the MOP was confirmed and the PSF was studied on and off-axis. In addition, we present details of the modelling and analysis, which was used to calculate the results from the test campaign. The effective area and PSF are in good agreement with the modelling, indicating that the optic is performing as expected.

eROSITA aboard the Spectrum-Roentgen-Gamma satellite, successfully launched in July 2019, is the first X-ray astronomical telescope operational at the Sun-Earth Lagrange point L2. A prime scientific goal of eROSITA is the detection of 100000 clusters of galaxies, which at the fainter luminosity end appears as weak and slightly extended objects. For a reliable detection and characterization of the sources also a detailed knowledge of the instrumental background is required. In the light of the upcoming ESA Athena mission and other future X-ray missions, eROSITA can play a role as pathfinder in terms of space environment and non-X-ray background at L2.. Initial results related to the eROSITA in-flight background have been obtained during Commissioning and subsequent Calibration and Performance Verification phases. The eROSITA background is composed of various components, such as from the electronics, from particle induced radiation inside the camera, external particles registered (and rejected) onboard, stray-light from celestial sources, and general X-ray background. By means of dedicated variations of the set-up (e.g., filter wheel, on-board processing) and viewing direction we started to disentangle the components and origins. Particle background variations appear to be low, which may be expected due to the low solar activity at the moment. The general background level appears to exceed pre-launch expectation. This is currently under investigation.

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.

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.

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.

All-sky surveys are crucial to discover transient objects. In reality, however, it is impossible to achieve high sensitivity, high cadence, wide sky coverage, and broad wavelength range at the same time. This is where observations with small telescopes can come in significant, as small telescopes often can make high cadence monitoring and flexible operations, playing a complementary role to large observatories. We plan to launch a new 6U-size CubeSat X-ray observatory, NinjaSat, in 2022 to conduct a flexible X-ray observation program. The satellite is equipped with two identical non-imaging Gas Multiplier Counters (GMCs) sensitive to X-rays in the 2–50 keV band with a total effective area of 36 cm² at 6 keV. Coupled with X-ray collimators of a 2.1° field-of-view, NinjaSat is suitable for flexible multi-wavelength coordinated observations of bright (⪆10 mCrab) X-ray sources with particular emphasis on their time variability. An example of our targets is one of the brightest celestial X-ray objects, Scorpius X-1, which hosts a fast-spinning neutron star and is a candidate source for coherent gravitational waves. The quasi-periodic oscillation (QPO) of neutron-star systems is considered to carry important information on the neutron star’s rotational frequency, which is useful for sensitive gravitational-wave searches. Scorpius X-1, being one of the brightest, provides the best opportunity to study the QPO. Combining with coordinated simultaneous monitoring observations with recently-developed fast optical photometry, the mechanism of the mass accretion of the disk can also be studied. We plan to use NinjaSat also for space science education, particularly X-ray astronomy, for students and the general public.

BurstCube aims to expand sky coverage in order to detect, localize, and rapidly disseminate information about gamma-ray bursts (GRBs). BurstCube is a ’6U’ CubeSat with an instrument comprised of 4 Cesium Iodide (CsI) scintillators coupled to arrays of Silicon photo-multipliers (SiPMs) and will be sensitive to gamma-rays between 50 keV and 1 MeV. BurstCube will assist current observatories, such as Swift and Fermi, in the detection of GRBs as well as provide astronomical context to gravitational wave (GW) events detected by LIGO, Virgo, and KAGRA. BurstCube is currently in its development phase with a launch readiness date in early 2022.

The origin of the cosmic diffuse gamma-ray (CDG) background in the 0.3 – 30 MeV energy range is a mystery that has persisted for over 40 years. The Mini Astrophysical MeV Background Observatory (MAMBO) is a CubeSat mission concept motivated by the fact that, since the MeV CDG is relatively bright, only a small detector is required to make highquality measurements of it. Indeed, the sensitivity of space-based gamma-ray instruments to the CDG is limited not by size, but by the locally generated instrumental background produced by interactions of energetic particles in spacecraft materials. Comparatively tiny CubeSat platforms provide a uniquely quiet environment relative to previous gamma-ray science missions. The MAMBO mission will provide the best measurements ever made of the MeV CDG spectrum and angular distribution, utilizing two key innovations: 1) low instrumental background on a 12U CubeSat platform; and 2) an innovative shielded spectrometer design that simultaneously measures signal and background. We describe the MAMBO instrument and mission concept in detail, including simulations and laboratory measurements demonstrating the key measurement concept.

The X-Ray Imaging and Spectroscopy Mission (XRISM) is the successor to the 2016 Hitomi mission that ended prematurely. Like Hitomi, the primary science goals are to examine astrophysical problems with precise highresolution X-ray spectroscopy. XRISM promises to discover new horizons in X-ray astronomy. XRISM carries a 6 x 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly and a co-aligned X-ray CCD camera that covers the same energy band over a large field of view. XRISM utilizes Hitomi heritage, but all designs were reviewed. The attitude and orbit control system were improved in hardware and software. The number of star sensors were increased from two to three to improve coverage and robustness in onboard attitude determination and to obtain a wider field of view sun sensor. The fault detection, isolation, and reconfiguration (FDIR) system was carefully examined and reconfigured. Together with a planned increase of ground support stations, the survivability of the spacecraft is significantly improved.

We report current status of developing Soft X-ray Imager (SXI), the X-ray CCD camera onboard X-Ray Imaging and Spectroscopy Mission (XRISM). Four flight model (FM) CCDs have been selected considering several items including energy resolution at 5.9keV, CTI, dark current, etc. We have also completed calibration campaign for all the FM CCDs. Initial analyses show that the response function for monochromatic X-rays is basically the same as that of Hitomi CCDs. The focal plane including the single-stage Stirling cooler has been assembled. Production of key parts in SXI sensor body such as contamination blocking filter and onboard calibration source has been finished and they are waiting for assemble. The digitized signals of the CCD are corrected step by step before conversion to X-ray energy. We are preparing calibration database for the correction such as CTI, gain, and line redistribution function.

The Resolve detector system is calibrated on the ground in three stages: at the focal plane assembly, at the calorimeter spectrometer insert, and at the full instrument level. We have just completed the first two stages and have measured the detailed core line shape and spectral redistribution functions, by pixel, and as a function of energy. In addition, we have measured the energy scale function that translates instrument units into spectral units, by pixel, and as a function of detector heat sink temperature. We discuss the results of the Resolve calibration program to date as well as implications for the calibration of future high resolution x-ray spectrometers.

X-Ray Imaging and Spectroscopy Mission (XRISM) is the seventh Japanese X-ray astronomical satellite scheduled to be launched in the Japanese fiscal year 2022. XRISM has two mission instruments, “Resolve”, a soft X-ray spectrometer, and “Xtend”, a soft X-ray imager. The Former is an X-ray micro-calorimeter that has ∼ 5 eV of energy resolution with 3′ × 3 ′ of field of view. The Latter is an X-ray CCD camera with 38′ × 38′ of field of view. Both instruments are placed on the focal plane of X-ray telescopes, X-ray Mirror Assembly (XMA). Xtend CCDs are designed almost the same as those of Hitomi (ASTRO-H), whereas some improvements have been applied. In 2019, flight-model (FM) candidates of Xtend CCDs were fabricated by Hamamatsu Photonics K.K. We performed screening experiments to examine whether they met requirements or not, and then selected the best four chips as the FM. We then performed on-ground calibration on August 2019 and September 2019 for the FM chips to determine the gain correction parameters and to construct the detector response with several energies of monochromatic X-ray. In this paper, we report screening, selection, and on-ground calibration processes, especially focusing on the response verification.

The XRISM X-ray observatory will fly two advanced instruments, the Resolve high-resolution spectrometer and the Xtend wide-field imager. These instruments, particularly Resolve, pose calibration challenges due to the unprecedented combination of spectral resolution, spectral coverage, and effective area, combined with a need to characterize the imaging fidelity of the full instrument system to realize the mission’s ambitious science goals. We present the status of the XRISM in-flight calibration plan, building on lessons from Hitomi and other X-ray missions. We present a discussion of targets and observing strategies to address the needed calibration measurements, with a focus on developing methodologies to plan a thorough and flexible calibration campaign and provide insight on calibration systematic error. We also discuss observations that exploit Resolve’s spectral

GEO-X (GEOspace X-ray imager) is a 50 kg-class small satellite to image the global Earth’s magnetosphere in X-rays via solar wind charge exchange emission. A 12U CubeSat will be injected into an elliptical orbit with an apogee distance of ∼40 Earth radii. In order to observe the diffuse soft X-ray emission in 0.3-2 keV and to verify X-ray imaging of the dayside structures of the magnetosphere such as cusps, magnetosheaths and magnetopauses which are identified statistically by in-situ satellite observations, an original light-weight X-ray imaging spectrometer (∼10 kg, ∼10 W, ∼10×10×30 cm) will be carried. The payload is composed of a ultra light-weight MEMS Wolter type-I telescope (∼4×4 deg² FOV, <10 arcmin resolution) and a high speed CMOS sensor with a thin optical blocking filter (∼2×2 cm² , frame rate ∼20 ms, energy resolution <80 eV FWHM at 0.6 keV). An aimed launch year is 2023-25 corresponding to the 25th solar maximum.

We are planning a new solar satellite mission, "PhoENiX", for understanding of particle acceleration during magnetic reconnection. The main observation targets of this mission are solar flares. The scientific objectives of this mission are (1) to identify particle acceleration sites, (2) to investigate temporal evolution of particle acceleration, and (3) to characterize properties of accelerated particles, during solar flares. In order to achieve these science objectives, the PhoENiX satellite is planned to be equipped with three instruments of (1) Photon-counting type focusing-imaging spectrometer in soft X-rays (up to ~10 keV), (2) Photoncounting type focusing-imaging spectrometer in hard X-rays (up to ~30 keV), and (3) Spectropolarimeter in soft gamma-rays (spectroscopy is available in the energy range of from > 20 keV to < 600 keV; spectropolarimetry is available from >60 keV to < 600 keV). We plan to realize PhoENiX satellite mission around next solar maximum (around 2025).

We propose a high-time-resolution, high-spectral-resolution X-ray telescope that uses transition-edge sensors (TES) as detectors and collector optics to direct the X-rays onto the focal plane, providing a large effective area in a small satellite. The key science driver of the instrument is to study neutron stars and accreting black holes. The proposed instrument is built upon two technologies that are already at high TRL: TES X-ray detectors and collector optics.

We present the concept of a future Japan-lead X-ray mission, FORCE (Focusing On Relativistic universe and Cosmic Evolution). FORCE is characterized by broadband (1-80 keV) X-ray imaging spectroscopy with high angular resolution (<15"). The sensitivity above 10 keV will be 10 times higher than that of any previous hard X-ray missions. FORCE will trace the cosmic evolution by searching for ``missing black holes'' in the entire range of their mass spectrum and investigate the nature of relativistic particles at various astrophysical shocks by observing their non-thermal X-ray emission.

Arcus will provide high-resolution soft X-ray spectroscopy in the 12-50Å bandpass with sensitivity orders of magnitude higher than any previous astronomical observatory. The three top science goals for Arcus are to (1) measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, groups, and clusters, (2) trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback and (3) explore how stars form and evolve. Arcus uses the same 12m focal length grazing-incidence silicon pore X-ray optics (SPO) developed for the Athena mission. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics.

The enhanced X-ray Timing and Polarimetry Observatory (eXTP) is a flagship international collaboration mission led by Chinese Academy of Sciences, with a large contribution from more than 20 European institutes. eXTP mission is designed to study the equation of state of ultra-dense matter under extreme conditions of strong density, gravity and magnetic field. The satellite carries four main instruments, including the Spectroscopy Focusing Array (SFA), the Large Area Detector (LAD), the Polarimetry Focusing array (PFA) and the Wide Field Monitor (WFM), enabling simultaneous spectral-timing-polarimetry studies of celestial sources in the energy range from 0.5-30 keV. The satellite will fly at a near-zero-inclination Low Earth Orbit, and is featured with long-time steady high-precision coaxial pointing, near realtime burst alert distribution, and follow-up maneuver capabilities. This paper describes the primary mission requirements and constraints, and presents an overall mission analysis including orbit analysis, pointing strategy, and board-ground communications, etc. The preliminary design of eXTP satellite is also introduced, including satellite overall configuration, observation modes, avionics architecture and development plan.

The Spectroscopy Focusing Array (SFA) onboard the enhanced X-ray Timing and Polarimetry (eXTP) observatory consists of 9 modules, each comprising a Wolter type I telescope with a field of view (FOV) around 16 arcminutes and a focal plane silicon drift detector (SDD) with 19 hexagonal pixels. Due to the large size of each individual SDD pixel (each pixel corresponds to an area of ∼ 3.6 arcminutes in diameter) and the limited pixel number, SFA can not obtain a real image of the observed region like many other X-ray imaging telescopes. Thus, contamination from nearby bright sources needs to be considered when we study the properties of the target source. We simulate such contaminations using the SIXTE simulator. In this paper we present the results by taking observations of the millisecond pulsar PSR J0437–4715 as an example, and discuss the cases for contamination on background or target source respectively.

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 the full exploitaiton of 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 '30s by next generation facilities like aLIGO/aVirgo, LISA, KAGRA, and Einstein Telescope (ET), as well as of most classes of transient sources, thus providing an ideal sinergy with the large e.m. facilities of the near future like LSST, ELT, TMT, SKA, CTA, ATHENA. We present an overview of the mission science case, concept design (instruments and spacecraft) and expected performances.

THESEUS (Transient High Energy Sky and Early Universe Surveyor) is one of the three missions selected by ESA as fifth medium class mission (M5) candidates in its Cosmic Vision science program, currently under assessment in a phase A study with a planned launch date in 2032. THESEUS is designed to carry on-board two wide and deep sky monitoring instruments for X/gamma-ray transients detection: a wide-field soft X-ray monitor with imaging capability (Soft X-ray Imager, SXI, 0.3 – 5 keV), a hard X-ray, partially-imaging spectroscopic instrument (X and Gamma Imaging Spectrometer, XGIS, 2 keV – 10 MeV), and an optical/near-IR telescope with both imaging and spectroscopic capability (InfraRed Telescope, IRT, 0.7 – 1.8 μm). The spacecraft will be capable of performing fast repointing of the IRT to the error region provided by the monitors, thus allowing it to detect and localize the transient sources down to a few arcsec accuracy, for immediate identification and redshift determination. The prime goal of the XGIS will be to detect transient sources, with monitoring timescales down to milliseconds, both independently of, or following up, SXI detections, and identify the sources performing localisation at <15 arcmin and characterize them over a broad energy band, thus providing also unique clues to their emission physics. The XGIS system consists of two independent but identical coded mask cameras, arranged to cover 2 steradians. The XGIS will exploit an innovative technology coupling Silicon Drift Detectors (SDD) with crystal scintillator bars and a very low-noise distributed front-end electronics (ORION ASICs), which will produce a position sensitive detection plane, with a large effective area over a huge energy band (from soft X-rays to soft gamma-rays) with timing resolution down to a few µs. Here is presented an overview of the XGIS instrument design, its configuration, and capabilities.

We are entering a new era for high energy astrophysics with the use of new technology to increase our ability to both survey and monitor the sky. The Soft X-ray Imager (SXI) instrument on the THESEUS mission will revolutionize transient astronomy by using wide-field focusing optics to increase the sensitivity to fast transients by several orders of magnitude. The THESEUS mission is under Phase A study by ESA for its M5 opportunity. THESEUS will carry two large area monitors utilizing Lobster-eye (the SXI instrument) and coded-mask (the XGIS instrument) technologies, and an opticalIR telescope to provide source redshifts using multi-band imaging and spectroscopy. The SXI will operate in the soft (0.3- 5 keV) X-ray band, and consists of two identical modules, each comprising 64 Micro Pore Optics and 8 large-format CMOS detectors. It will image a total field of view of 0.5 steradian instantaneously while providing arcminute localization accuracy. During the mission, the SXI will find many hundreds of transients per year, facilitating an exploration of the earliest phase of star formation and comes at a time when multi-messenger astronomy has begun to provide a new window on the universe. THESEUS will also provide key targets for other observing facilities, such as Athena and 30m class ground-based telescopes.

The Infra-Red Telescope (IRT) is part of the payload of the THESEUS mission, which is one of the two ESA M5 candidates within the Cosmic Vision program, planned for launch in 2032. The THESEUS payload, composed by two high energy wide field monitors (SXI and XGIS) and a near infra-red telescope (IRT), is optimized to detect, localize and characterize Gamma-Ray Bursts and other high-energy transients. The main goal of the IRT is to identify and precisely localize the NIR counterparts of the high-energy sources and to measure their distance. Here we present the design of the IRT and its expected performance.

Space-based X-ray detectors are subject to significant fluxes of charged particles in orbit, notably energetic cosmic ray protons, contributing a significant background. We develop novel machine learning algorithms to detect charged particle events in next-generation X-ray CCDs and DEPFET detectors, with initial studies focusing on the Athena Wide Field Imager (WFI) DEPFET detector. We train and test a prototype convolutional neural network algorithm and find that charged particle and X-ray events are identified with a high degree of accuracy, exploiting correlations between pixels to improve performance over existing event detection algorithms. 99 per cent of frames containing a cosmic ray are identified and the neural network is able to correctly identify up to 40 per cent of the cosmic rays that are missed by current event classification criteria, showing potential to significantly reduce the instrumental background, and unlock the full scientific potential of future X-ray missions such as Athena, Lynx and AXIS.

This paper details preliminary photon measurements with the monolithic silicon detector ATLASPix, a pixel detector built and optimized for the CERN experiment ATLAS. The goal of this paper is to determine the promise of pixelated silicon in future space-based gamma-ray experiments. With this goal in mind, radioactive photon sources were used to determine the energy resolution and detector response of ATLASPix; these are novel measurements for ATLASPix, a detector built for a ground-based particle accelerator. As part of this project a new iteration of monolithic Si pixels, named AstroPix, have been created based on ATLASPix, and the eventual goal is to further optimize AstroPix for gamma-ray detection by constructing a prototype Compton telescope. The energy resolution of both the digital and analog output of ATLASPix is the focus of this paper, as it is a critical metric for Compton telescopes. It was found that with the analog output of the detector, the energy resolution of a single pixel was 7.69 ± 0.13% at 5.89 keV and 7.27 ± 1.18% at 30.1 keV, which exceeds the conservative baseline requirements of 10% resolution at 60 keV and is an encouraging start to an optimistic goal of <2% resolution at 60 keV. The digital output of the entire detector consistently yielded energy resolutions that exceeded 100% for different sources. The analog output of the monolithic silicon pixels indicates that this is a promising technology for future gamma-ray missions, while the analysis of the digital output points to the need for a redesign of future photon-sensitive monolithic silicon pixel detectors.

Detectors with high energy and position resolution over a wide energy range are required for space telescopes in high energy astrophysics missions. By combining a low noise fully depleted pnCCD detector with a columnar CsI(Tl) scintillator, an energy dispersive spatially resolving detector can be realized with high quantum efficiency in the range from below 0.5 keV to above 150 keV. The detector is exposed to the photon source such that the X-rays first traverse the 450 μm sensitive pnCCD. If they are stopped through the photoelectric effect in the silicon detector, Fano-noiselimited energy resolution is achieved. This is true for X-rays from a few hundred eV up to approximately 15 keV. Above this energy the probability that the photon penetrates the pnCCD and converts in the CsI(Tl) scintillator is becoming higher. Due to the high atomic number of Cs (Z=55) and I (Z=53) hard X-rays are stopped efficiently in a 0.7 mm thick CsI(Tl) scintillator for photon energies up to 150 keV. The light from the scintillator is recorded with the same backilluminated pnCCD. For X-rays from a ⁵⁷Co source with an energy of 122 keV and 136 keV we achieve an energy resolution of 0.7% (FWHM=850 eV) for the direct conversion in the silicon while the energy resolution for the conversion in the CsI(Tl) is 10% (12 keV). We have performed a knife-edge experiment at 122 keV and achieved a position precision of 27 μm at that energy. Monte Carlo simulations were showing similar, fully compatible results. In case the X-rays are converted directly in the silicon the position precision is better than 10 μm. This is close to the theoretical limit of the spatial resolution in such a system, which is given by the length of the tracks of the secondary electrons in the ionizing process in silicon and CsI. Spectra, images and the results of the GEANT4 simulations will be shown.

The Hot Universe Baryon Surveyor (HUBS) mission is proposed to study “missing” baryons in the universe. Unlike dark matter, baryonic matter is made of elements in the periodic table, and can be directly observed through the electromagnetic signals that it produces. Stars contain only a tiny fraction of the baryonic matter known to be present in the universe. Additional baryons are found to be in diffuse (gaseous) form, in or between galaxies, but a significant fraction has not yet been seen. The latter (“missing” baryons) are thought to be hiding in low-density warm-hot ionized medium (WHIM), based on results from theoretical studies and recent observations, and be distributed in the vicinity of galaxies (i.e., circumgalactic medium) and between galaxies (i.e., intergalactic medium). Such gas would radiate mainly in the soft X-ray band and the emission would be very weak, due to its very low density. HUBS is optimized to detect the X-ray emission from the hot baryons in the circumgalactic medium, and thus fill a void in observational astronomy. The goal is not only to detect the “missing” baryons, but to characterize their physical and chemical properties, as well as to measure their spatial distribution. The results would establish the boundary conditions for understanding galaxy evolution. Though highly challenging, detecting “missing” baryons in the intergalactic medium could be attempted, perhaps in the outskirts of galaxy clusters, and could shed significant light on the large-scale structures of the universe. The current design of HUBS will be presented, along with the status of technology development.

The Hot Universe Baryon Surveyor (HUBS) mission will carry an imaging X-ray telescope (IXT) for covering an energy range from 0.5 keV to 10 keV to study the hot baryon evolution. In this paper, we report the optical design for HUBS mission and the latest developments at IPOE, Tongji Univeristy. For HUBS mission, we had designed a three-stage conic-approximation type to simplify the manufacturing process. The basic process of imaging X-ray telescopes based on thermal glass slumping has been introduced. Nearly ten prototypes have been fabricated for the process optimization over the years. In August 2018, an IXT prototype with 21 layers was measured at the PANTER X-ray test facility, indicating an HPD of 111″ and an effective area of 39 cm² at 1.49 keV. In September 2019, the latest prototype with 3 layers reached to an HPD of 58″ at 1.49 keV.

The high-resolution X-ray imaging spectrometer of the Hot Universe Baryon Surveyor (HUBS) mission is based on the superconducting transition edge sensor (TES) technology. A TES serves as a thermometer for sensing the temperature change of a microcalorimeter to measure the energy of incident X-rays. In order to achieve high sensitivity, TES needs to operate at temperatures below 100 mK. A combination of a 4 K pre-cooling system and a sub-K cooling system is required to achieve such a low temperature. In this paper, it is proposed to directly obtain the 4 K temperature by a high frequency pulse tube cryocooler (HPTC) for HUBS. The advantages of this technology is compact structure and high reliability, compared with other technologies (for instance, multi-stage Stirling cryocoolers + Joule-Thompson cooler). We have constructed a multi-stage HPTC. The test cooling performance, as well as the design of the cryocooler, existing challenges and proposed solutions will be presented.

The prompt emission of GRBs has been investigated for more than 50 years but remains poorly understood. Commonly, spectral and temporal profiles of γ-ray emission are analysed. However, they are insufficient for a complete picture on GRB-related physics. The addition of polarization measurements provides invaluable information towards the understanding of these astrophysical sources. In recent years, dedicated polarimeters, such as POLAR and GAP, were built. The former of which observed low levels of polarization as well as a temporal evolution of the polarization angle. It was understood that a larger sample of GRB polarization measurements and time resolved studies are necessary to constrain theoretical models. The POLAR-2 mission aims to address this by increasing the effective area by an order of magnitude compared to POLAR. POLAR-2 is manifested for launch on board the China Space Station in 2024 and will operate for at least 2 years. Insight from POLAR will aid in the improvement of the overall POLAR-2 design. Major improvements (compared to POLAR) will include the replacement of multi-anode PMTs (MAPMTs) with SiPMs, increase in sensitive volume and further technological upgrades. POLAR-2 is projected to measure about 50 GRBs per year with equal or better quality compared to the best seen by POLAR. The instrument design, preliminary results and anticipated scientific potential of this mission will be discussed.

This paper introduces a second-generation balloon-borne hard X-ray polarimetry mission, XL-Calibur. X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as pulsars and binary black hole systems. The XL-Calibur contains a grazing incidence X-ray telescope with a focal plane detector unit that is sensitive to linear polarization. The telescope is very similar in design to the ASTRO-H HXT telescopes that has the world’s largest effective area above ~10 keV. The detector unit combines a low atomic number Compton scatterer with a CdZnTe detector assembly to measure the polarization making use of the fact that polarized photons Compton scatter preferentially perpendicular to the electric field orientation. It also contains a CdZnTe imager at the bottom. The detector assembly is surrounded by the improved anti-coincidence shielding, giving a better sensitivity. The pointing system with arcsecond accuracy will be achieved.

We describe a new implementation of a broad-band soft X-ray polarimeter, substantially based on a previous design. This implementation, the Pioneer Soft X-ray Polarimeter (PiSoX) is a SmallSat, designed for NASA’s call for Astrophysics Pioneers, small missions that could be CubeSats, balloon experiments, or SmallSats. As in REDSoX, the grating arrangement is designed optimally for the purpose of polarimetry with broad-band focussing optics by matching the dispersion of the spectrometer channels to laterally graded multilayers (LGMLs). The system can achieve polarization modulation factors over 90%. For PiSoX, the optics are lightweight Si mirrors in a one-bounce parabolic configuration. High efficiency, blazed gratings from opposite sectors are oriented to disperse to a LGML forming a channel covering the wavelength range from 35 Å to 75 Å (165 - 350 eV). Upon satellite rotation, the intensities of the dispersed spectra, after reflection and polarizing by the LGMLs, give the three Stokes parameters needed to determine a source’s linear polarization fraction and orientation. The design can be extended to higher energies as LGMLs are developed further. We describe examples of the potential scientific return from instruments based on this design.

HiZ-GUNDAM is a future satellite mission which will lead the time-domain astronomy and the multi-messenger astronomy through observations of high-energy transient phenomena. A mission concept of HiZ-GUNDAM was approved by ISAS/JAXA, and it is one of the future satellite candidates of JAXA’s medium-class mission. We are in pre-phase A (before pre-project) and elaborating the mission concept, mission/system requirements for the launch in the late 2020s. The main themes of HiZ-GUNDAM mission are (1) exploration of the early universe with high-redshift gamma-ray bursts, and (2) contribution to the multi-messenger astronomy. HiZ-GUNDAM has two kinds of mission payload. The wide field X-ray monitors consist of Lobster Eye optics array and focal imaging sensor, and monitor ~1 steradian field of view in 0.5 – 4 keV energy range. The near infrared telescope has an aperture size 30 cm in diameter, and simultaneously observes four wavelength bands between 0.5 – 2.5 μm. In this paper, we introduce the mission overview of HiZ-GUNDAM.

Laue lenses has been proposed for gamma-ray astronomy since long. But Laue lenses are seriously constrained by Braggs law. Consequently, it has proven difficult to devise convincing designs of Laue lenses covering an energy range of more than a few hundred keV. We are developing a miniature pedestal allowing to adjust the Bragg angle of individual crystals in a large Laue lens. We also develop an optical system to monitor the adjustment. These developments would eliminate two major technical obstacles for Laue lens construction: one: the precision mounting of the crystals to the support panel, and two: ensuring the necessary rigidity and stability of the gamma-ray transparent support panel. But even more importantly, these developments would open the way for retuning the Laue lens for different energy bands. We shall show, how a lens designed for the 300 to 800 keV band can be used effectively between 150 keV and 2.4 MeV.

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a Probe-class mission concept that will provide essential contributions to multimessenger astrophysics in the next decade. AMEGO operates both as a Compton and pair telescope to achieve unprecedented sensitivity between 200 keV and >5 GeV. The instrument consists of four subsystems. A double-sided strip silicon Tracker gives a precise measure of the first Compton scatter interaction and tracks of pair-conversion products. A novel CdZnTe Low Energy Calorimeter with excellent position and energy resolution surrounds the bottom and sides of the Tracker to detect the Compton-scattered photons which enhances the polarization and narrow-line sensitivity. A thick CsI High Energy Calorimeter contains the high-energy Compton and pair events. The instrument is surrounded by a plastic anti-coincidence detector to veto the cosmic-ray background. We have performed detailed simulations to predict the telescope performance and are currently building a prototype instrument. The AMEGO prototype, known as ComPair, will be tested at the High Intensity Gamma-Ray Source in 2021, followed by a balloon flight in Fall of 2022. In this presentation we will give an overview of the science motivation, a description of the observatory, and an update of the prototype instrument development.

AMEGO is a combined Compton and pair-production telescope designed to survey the sky from ∼ 200 keV to > 10 GeV. The prototype, known as ComPair, will undergo beam tests in 2021 and a short-duration balloon flight the following year. The ComPair tracker is based on ten layers of 10 cm × 10 cm double-sided silicon detectors read out with a custom front-end based on the IDEAS VATA460 ASIC and a Zynq SoC ARM+FPGA running petalinux. In this contribution, we will discuss detector and ASIC characterization, calibration systems, and the overall design of the ComPair silicon tracker.

The Advanced Scintillator Compton Telescope (ASCOT) is a medium-energy gamma-ray Compton telescope flown on NASA’s high-altitude scientific balloon from Palestine, TX on 5th July 2018. It uses commercially available highperformance scintillators like Cerium Bromide (CeBr₃) and p-terphenyl along with compact readout devices - silicon photomultipliers (SiPMs) - for an improved instrument response. ASCOT was built to address the existing need for observations in the gamma-ray energy range of 0.4 - 20 MeV. Operating stably throughout the mission, it reached an altitude of 120,000 ft and observed the Crab Nebula at MeV energies for ~5 hours. Built on the legacy of COMPTEL (onboard CGRO), along with the hardware advancement ASCOT also makes use of the Time-of-Flight (ToF) background rejection technique for effective imaging. Presented here is the Energy and ToF calibrated flight data with optimal data cuts (Earth Horizon Cut, Pulse Shape Discrimination Cut). The growth curves generated using this data from 5 to 100 g/cm² of residual atmosphere in conjunction with the Monte Carlo simulations of the instrument response have been used to obtain the Cosmic Diffuse Gamma-ray (CDG) flux value of (1.28±0.37)×10^-5 photons/cm² /s/sr/keV for 0.4 – 0.7 MeV energy range. The 3σ upper limit for CDG flux is 1.8×10^-5 photons/cm² /s/sr/keV for 0.7-1.5 MeV and 2×10^-6 photons/cm² /s/sr/keV for 1.5-2.5 MeV. The analysis of the Crab Nebula from flight observation is underway.

SVOM is a space mission in cooperation between China and France. SVOM stands for “Space multi-band astronomical Variable Objects Monitor”. SVOM mission aims at detecting GRB (Gamma Ray Burst) through a collection of instruments in various gamma and X energy bands as well as in visible wave lengths through a narrow field of view telescope. Satellite management unit is an important onboard device of SVOM satellite and it’s responsible for implementation of the sophisticated onboard observation management which handles general program, GRB and targetof-opportunity observation. Because GRB would be automatically generated on-board, a sound mechanism to decide to accept or reject is necessary. Then, some work of predictions about satellite capacity is needed. These requirements place high demands on autonomy of onboard satellite management. Besides, other pre-planned observations and target-ofopportunity observations uploaded by ground station need to be processed simultaneously with a complicated logic. When an observation is finished, the previously interrupted observation may be recovered at specific time. Further, unpredictable satellite attitude increase difficulty in ground planning such as X-band visibility. This results in X-band visibility algorithm to be implemented by satellite management unit. Face these complex requirements, a reasonable interface design is important to reduce coupling. The interface is clear and the design is easy to maintain and flexible to possible new requirements. Through several operational tests which include typical scenario, the design is verified to meet the requirements of onboard observation management.

The EUV high-throughput spectroscopic telescope (EUVST) onboard the Solar-C mission has the high spatial (0.4′′) resolution over a wide wavelength range in the vacuum ultraviolet. To achieve high spatial resolution under a design constraint given by the JAXA Epsilon launch vehicle, we further update the optical design to secure margins needed to realize 0.4′′ spatial resolution over a field of view of 100′′×100′′. To estimate the error budgets of spatial and spectral resolutions due to installation and fabrication errors, we perform a sensitivity analysis for the position and orientation of each optical element and for the grating parameters by ray tracing with the Zemax software. We obtain point spread functions (PSF) for rays from 9 fields and at 9 wavelengths on each detector by changing each parameter slightly. A full width at half maximum (FWHM) of the PSF is derived at each field and wavelength position as a function of the perturbation of each optical parameter. Assuming a mount system of each optical element and an error of each optical parameter, we estimate spatial and spectral resolutions by taking installation and fabrication errors into account. The results of the sensitivity analysis suggest that budgets of the total of optical design and the assembly errors account for 15% and 5.8% of our budgets of the spatial resolution in the long wavelength and short wavelength bands, respectively. On the other hand, the grating fabrication errors give a large degradation of spatial and spectral resolutions, and investigations of compensators are needed to relax the fabrication tolerance of the grating surface parameters.

The EUV High-Throughput Spectroscopic Telescope (EUVST) of Solar-C mission consists of only two imaging optical components; a 28-cm clear aperture off-axis parabolic primary mirror and a two-split ellipsoidal grating without a blocking filter for visible light before the primary mirror to achieve unprecedented high spatial and temporal resolution in EUV-UV imaging spectroscopic observations. For this reason, about 60 W of sunlight is absorbed by the multilayer coating on the mirror. We report a thermal design of telescope in which the temperature of the primary mirror bonding part and underlying tip-tilt and slit-scanning mechanisms is well lower than a glass transition temperature of adhesive (about 60°C) and thermal deformation of the primary mirror is small, although it is non-negligibly small.

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.

We present a number of example studies of telescope optics using the latest version of the AstroX add on toolbox for McXtrace. Among which are first, a benchmark study of effective area and vignetting for the Chandra X-ray Observatory which we find to match well with literature. Second, a convenient way of building a telescope model (in this case NuSTAR) with many similar optical elements scripted using python module. This lends itself well to be included in online notebooks and/or for teaching. Third, we show a new AstroX module for lobster eye optics, and fourth, a study of the proposed solar axion telescope BabyIAXO.

The remaining relative uncertainties on the calibration of the XMM-Newton telescope effective areas can still yield differences of the order of ten percent for the astrophysical parameters derived from the EPIC pn and MOS data. The aim of the CORRAREA project is to provide an empirical correction function determined by cross-calibration of the EPIC effective areas. The correction will be integrated as a default multiplicative energy-dependent correction factor to the ARFs in the SAS software package. It is determined by cross-calibrating the on-axis effective areas using a sample of more than 250 bright but non-piled-up observations of point-like sources. A fit-and-stack approach is used for cross-calibration with physically motivated models defined separately for each observation in the sample. Data-to-model ratios are calculated for each of the three detectors by dividing the detector data with the pn model convoluted with the detector response. A fit to the ratio of the MOS and pn data-to-model ratios then yields the correction function. The EPIC pn camera was chosen as the reference instrument as most of its calibration parameters have remained stable over the lifetime of the XMM-Newton mission. A highly automated pipeline was developed to allow for easy recalculation of the correction function to account for any future changes introduced in the XMM-Newton calibration files or SAS. The automated pipeline also allows to easily add future observations to the sample with only two manual tasks per observation: selection of a model and visual screening including the selection of source and background regions.

The X-ray Integral Field Unit (X-IFU) of the ATHENA space observatory is based on a 3 kilo-pixels array of superconducting micro-calorimeters, that is read out with the Warm Front-End Electronics (WFEE) and then followed by the Digital Readout Electronics (DRE) outside the cryostat. We have developed low-noise/lowdrift amplifiers for this readout as well as performed simulations and measured the noise, bandwidth, linearity, harmonic distortion and thermal drift. Here we are presenting a realistic model of these parameters. These characterizations and models of the WFEE are necessary in order to get a full ATHENA X-IFU readout chain simulator. Impact of the WFEE low-frequency noise and its limited bandwidth on the entire X-IFU detection chain in Time Domain Multiplexing will be introduced.

The WFI instrument is designed for high-resolution X-ray imaging and spectroscopy with a large field of view. A movable mirror focuses the X-rays onto the focal plane detectors of the WFI. For design development of the instrument, structural analysis is performed from early project phases. The WFI project has entered phase B and the preliminary design is evolving towards a more detailed design including interface definitions. The focal plane of WFI consists of two detectors: Large Detector Array (LDA) and Fast Detector (FD). The LDA assembly is used for main observation modes, whereas FD is for very bright point sources. The complexity of the LDA design is due to the fact that it has to be compliant to contradictory requirements. Its sensors have to be thermally decoupled from the structure, but with a high stiffness to avoid relative displacement and deformation of sensitive components, e.g. bond wires. The LDA has an active area that is as large as ≈14x14 cm² but the thermal gradient across it shall be below 2.5-3K. The LDA is optimized with respect to mechanical requirements for launch loads and operational conditions in space. In order to minimize mass while withstanding thermo-mechanical, static and dynamic loads, various design studies have been carried out. With the aim to develop a design, which meets all structural and functional requirements, various structural analyses are performed. In this paper, the structural design studies and the preliminary analysis results of the WFI Large Detector Array are presented.

The Wide Field Imager (WFI) is one of two focal plane instruments of the Advanced Telescope for High-Energy Astrophysics (Athena), ESA’s next large X-ray observatory, planned for launch in the early 2030’s. The current baseline halo orbit is around L2, the first Lagrangian point of the Sun-Earth system, L1 is under consideration. For both potential halo orbits the radiation environment, solar and cosmic protons, electrons and He-ions will affect the performance of the instruments. A further critical contribution to the instrument background arises from the unfocused cosmic hard X-ray background. It is important to understand and estimate the expected instrumental background and to investigate measures, like design modifications or analysis methods, which could improve the expected background level in order to achieve the challenging scientific requirement (< 5 × 10⁻³ cts/cm²/keV/s at 2 - 7 keV). Previous WFI background simulations1 done in Geant4 have been improved by taking into account new information about the proton flux at L2. In addition, the simulation model of the WFI instrument and its surroundings employed in GEANT4 simulations has been refined to follow the technological development of the WFI camera.

The X-IFU instrument is one of the payloads of the ESA ATHENA observatory, offering an unprecedented high spectral resolution of X-ray. In the readout chain of the X-IFU instrument, the first warm stage is the WFEE subsystem. It comprises low-noise amplifiers, current sources, a serial bus and housekeeping elements. Until now, three ASICs dedicated to this subsystem have been developed and fully characterised. They all use a 350 nm SiGe BiCMOS technology. The first version was to verify the feasibility of basic topologies and radiation robustness of the technology, that has already been reported in previous papers. Based on the results of the first version, the second version was for testing the low-noise amplifier, the serial bus and the thermometer and the third ASIC is a complete version integrating all the components of one WFEE FDM channel. This paper presents these two ASICs and their representative experimental results as an update on the WFEE microelectronics. Moreover, following the shift of the readout multiplexing scheme from FDM to TDM, a new version adapting to technical changes has also been developed and current manufacturing. It is discussed at the end of the paper.

One of the science goals of the Wide Field Imager (WFI) on ESA’s Athena X-ray observatory is to map hot gas structures in the universe, such as clusters and groups of galaxies and the intergalactic medium. These deep observations of faint diffuse sources require low background and the best possible knowledge of that background. The WFI Background Working Group is approaching this problem from a variety of directions. Here we present analysis of Geant4 simulations of cosmic ray particles interacting with the structures aboard Athena, producing signal in the WFI. We search for phenomenological correlations between these particle tracks and detected events that would otherwise be categorized as X-rays, and explore ways to exploit these correlations to flag or reject such events in ground processing. In addition to reducing the Athena WFI instrumental background, these results are applicable to understanding the particle component in any silicon-based X-ray detector in space.

We present a test platform for the Athena X-IFU detection chain, shared between IRAP and CNES. This test bench, housed in a commercial two-stage ADR cryostat provided by Entropy GmbH, will serve as the first demonstration of the representative end-to-end readout chain for the X-IFU, using prototypes of the future flight electronics and currently available subsystems. The focal plane array (FPA), placed at the 50 mK cold stage of the ADR, includes a 1024-pixel array of transition-edge sensor (TES) microcalorimeter spectrometers provided by NASA/GSFC, superconducting amplifiers (SQUIDs) from VTT, as well as superconducting readout electronics for frequency domain multiplexing (FDM), provided by SRON. The detection chain then continues with the prototype room temperature electronics for the X-IFU: the Warm Front-End Electronics (WFEE, provided by APC) and the Digital Readout Electronics (DRE, provided by IRAP). The test bench yields critical feedback on current subsystem designs and electronic interfaces, and in the future will also be used for refining the X-IFU calibration plan as well as laboratory astrophysics experiments relevant to future X-IFU science. In this presentation, we describe the characterization of the cryostat, various design trades for the FPA and readout chain, and recent results from our current setup.

The core element of the Athena Wide-Field-Imager (WFI) is its detector assembly. The scientific raw data rate, depending on the observation mode, reaches values up to 3.65 Gbit/s. We demonstrate the error-free real-time processing capability using an input data stream that simulates scientific observations, e.g. a crab-like point source with 78,000 up to 195,000 photons per second.

The Athena observatory is the second large class ESA mission to be launched on early 2030’s. One of the two on board instruments is the X-IFU, which is a TES based kilo-pixels array able to perform simultaneous high grade energy spectroscopy (2.5eV@7keV) and imaging over the 5' FoV. The X-IFU sensitivity is degraded by primary particles background (bkg) of both solar and Galactic Cosmic Rays origin, and secondary electrons produced by primaries interacting with the materials surrounding the detector. The TES-array main sensor therefore needs a Cryogenic AntiCoincidence detector (CryoAC) to veto as much as possible such particles. The required residual bkg is 0.005 cts/cm² /s/keV in 2-10 keV energy bandwidth. The CryoAC is at present baselined as 4 pixels detector made of Silicon suspended absorbers sensed by a network of IrAu TESes, and placed at a distance < 1 mm below the TES-array. On November 2019, Athena has successfully passed the Mission Formulation Review (MFR), thus entering in Phase B. Next close goal is the MAR (Mission Adoption Review) planned in second half of 2022 where all the critical technologies must demonstrate a Technology Readiness Level (TRL) equal to 5. Here we will provide an overview of the CryoAC program advancement involving: 1) the present particle background assessment; 2) the assembly design concept and the related trade-off studies between the present baseline (4 pixels) against a monolithic solution (1 pixel); 2) the technology status (i.e., some results from the integrated chipset test; warm electronics). We will conclude with programmatic aspects.

Athena is an ESA-led space telescope to be launched in the early 2030s. The X-ray Integral Field Unit (X-IFU) on board of the Athena mission is an X-ray imaging spectrometer, sensitive to 0.2-12 keV X-rays. The main sensor of the X-IFU is an array of ~3200 closely-packed superconducting transition-edge sensor (TES) microcalorimeters with X-ray absorbers. The X-IFU provides a breakthrough spectral resolution of 2.5 eV (full width at half maximum; FWHM) at 6 keV, which enables us to access unrevealed properties of the hot gases that are formed at every level of the hierarchical structure of the universe. At SRON, we are developing Frequency Division Multiplexing (FDM) readout with SQUID amplifiers as a baseline technology for the X-IFU. In the FDM system, the microcalorimeter pixels are AC-biased at different frequencies from 1 to 5 MHz. Therefore, it is crucial to minimize frequency-dependent phenomena because it causes non-linearity effects in the detector response and degrades the spectral resolution. Theoretical analyses have shown that this non-linearity is caused by weak-link behavior, induced by superconducting leads and can be mitigated by increasing the normal resistance of the TES. We are also developing TES arrays based on a superconducting Ti/Au bi-layer with an Au absorber as a sensor backup technology for the X-IFU. We have recently fabricated TES calorimeters with large variation of normal resistance from 25 to 150 mΩ by changing the width and aspect ratio of the bi-layer. The TESes with 117 and 150 mΩ have shown a promising spectral performance of below 2 eV (FWHM) at 6 keV. However, we still see that the detector response is affected by the weak-link behavior, especially at high frequency regime. In this paper, we briefly summarize our results with a focus on the spectral performance and the detector responsivity for each TES design. We also present our recent works on fabrication related to a superconducting wiring process, which would be useful for further reduction of the weak-link effects.

The X-ray parallel beam facility XPBF 2.0 in the laboratory of the Physikalisch-Technische Bundesanstalt at the synchrotron radiation facility BESSY II provides a parallel beam of very low divergence, and adjustable beam sizes between about 100 μm and at least 5 mm. Further, XPBF 2.0 is equipped with a vacuum chamber with a hexapod system for accurate positioning of all silicon pore optic (SPO) sizes to be investigated, and a vertically movable CCD-based camera system to register the direct and the reflected beam at a sample to CCD distance of 12 m corresponding to the envisaged focal length of ATHENA (Advanced Telescope for High ENergy Astrophysics). Since its installation in 2016, the beamline has been constantly upgraded to improve performance and implementing the changing requirements. To accurately and constantly measure the 12 m distance, between the center of the sample (i.e. mirror module) and the CCD detector, a laser-tracker has been installed. Additionally, the cleanroom, housing the vacuum chamber, was upgraded with a cooling unit keeping the temperature at 20°C. The original phosphor screen in front of the CCD has been replaced with a new phosphor screen with different grain size and material. The next upgrade of the XPBF 2.0 is the installation of a new monochromator mirror to operate the beamline at 1.0 keV instead of 1.6 keV. This paper will present the upgrades of the X-ray parallel beam facility XPBF 2.0 and discuss next steps for characterizing SPOs with synchrotron radiation.

A state-of-the-art Low-Energy X-ray Reflectometer (LEXR) is in operation at DTU Space with the main purpose of characterizing coatings for the Advanced Telescope for High-ENergy Astrophysics (ATHENA), a selected Lclass ESA mission. In particular, soft materials are difficult to characterize at higher energies so the 1.487 keV beamline compliments our existing 8.048 keV reflectometer, allowing for a more complete understanding of thinfilm X-ray characteristics. Documenting and qualifying the as-deposited coatings for X-ray telescope optics is of crucial importance, both to ensure that the effective area requirements are met, but also to quantify any temporal evolution in coating characteristics as well as the impact of manufacturing process parameters on mirror performance. It is notably relevant in the case of ATHENA, as there is a desire to enhance the low-energy performance by using a low-Z material overcoating on top of the Ir coating. We report on the commissioning and qualify the performance of the as-built 1.487 keV reflectometer as well as discuss measurement repeatability and system limitations.

The mirror coatings for the Athena X-ray telescope assumes Ir/SiC bilayer thin films as a baseline design. Adding the soft overcoat to the Ir X-ray mirror coatings for the Athena optics is used to improve the low energy performance necessary to achieve the telescope effective area requirements. The Athena mirror is based on silicon pore optics technology, for which the manufacturing process involves a sequence of wet chemical and thermal post-coating treatments of the mirror plates. Establishing compatibility of the thin film material candidates following exposure to these processes is critical for the Athena mission since the specific coating quality will influence the performance of the X-ray telescope. We present an investigation of Ir and Ir/SiC thin films exposed to post-coating treatments based on coatings produced at DTU Space. The current status of the chemical procedures is presented with representative coatings from the Athena-dedicated coating facility.

The European Space Agency (ESA) mission ATHENA is a next generation large X-ray observatory which is slated to be launched in the early 2030s. It will have mirror assembly with 2.6-m diameter and a 12-m focal length that is made up of ~600 Silicon Pore Optic (SPO) mirror modules integrated into mirror assembly support structure. Existing facilities cannot calibrate the such a large mirror assembly in full illumination. To avoid having to make compromises during calibration of the mirror assembly a new long beam X-ray test facility would be required. A study for ESA on a such a new long beam X-ray test facility and the necessary GSE has been performed by a team from MPEs PANTER X-ray test facility. Here we present the current status of the design of a 800-m long and 2.8-m diameter beam line X-ray test facility in Garching, Germany.

As part of the thin film development for the Athena X-ray telescope and X-ray optics in general, we investigated the residual stress in iridium and chromium thin films deposited using direct current magnetron sputtering. Residual stresses in thin films can affect the performance and adhesion properties of the fabricated thin film coated X-ray optics. We characterized the thin films using X-ray reflectometry to determine the thin film thicknesses and stylus profilometry to determine the residual film stresses. To counterbalance the compressive stress identified in the iridium thin films, we introduced a chromium thin film layer for which the residual stress is tensile beneath the iridium film. However, chromium thin films are known to exhibit a grainy growth resulting in a high surface roughness which was also observed in this work. In this paper, we evaluated the effect on the iridium surface roughness when introducing a chromium underlayer and discussed the effect on the X-ray optics performance.

The SRG satellite with the eROSITA X-ray telescope as scientific payload was successfully launched on July 13, 2019 and deployed in a 6-month halo orbit around the second Lagrange point of the Sun Earth system. The telescope comprises an array of seven mirror systems with seven focal plane cameras. The spectroscopic CCD cameras are a further development of the very successful EPIC PN camera on the XMM-Newton satellite, which is after 20 years in space still successfully operating. Key component of the camera is the detector, which matches the large field of view of 1° to permit an all-sky survey in the energy range from 0.2 keV to 8 keV with state-of-the-art energy resolution. The image area of the PNCCD comprises 384 x 384 pixels. Their size of 75 x 75 μm² each, matches the angular resolution of the mirror system. Readout of the full frame is achieved in 9.18 ms but for thermal and onboard event pre-processing reasons, the time resolution is slowed down to 50 ms. The photon entrance window of five of the seven CCDs is equipped with an optical blocking filter, which turned out to be advantageous. The improved concept and design of the eROSITA cameras will be explained as well as their operation and performance in space.

The power of eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the core instrument on the Russian–German Spectrum–Roentgen–Gamma (SRG) mission, is high sensitivity at high spectral, spatial, and temporal resolution over a large field of view. This is achieved by combining 7 coaligned X–ray telescope modules, each composed of 54 paraboloid / hyperboloid mirror shells in a Wolter–I geometry, to focus the X–rays through optical blocking filters onto PNCCDs with a total of 1 million pixels, providing a spectral resolution of 60 – 160 eV FWHM over an energy range 0.2 – 8 keV and a 1 degree field of view at a time resolution of 50 ms. In order to make full scientific use of the unique capabilities of eROSITA, all the individual components have to be calibrated. The initial ground calibration was done at the PANTER and PUMA facilities of MPE as well as at BESSY, and was supplemented by an in–orbit calibration. We report on the extensive and often challenging calibration activities performed on ground and in space.

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary scientific payload on board the SRG (Spektrum Röntgen Gamma) mission, successfully launched from Baikonur in July 2019. Following a 101 days cruise phase, SRG reached its final orbit around the Lagrangian point L2, where it will carry out its mission of making a full survey of the X-ray sky. eROSITA is a complex instrument composed of seven identical co-aligned X-ray telescopes with a focal length of 1600mm and an aperture of 350mm. Each telescope is equipped with an independent CCD camera. The cold redundant ITC (Interface and Thermal Controller) manages all seven cameras as well as the thermal control of the telescope and the interface to the spacecraft. The cruise phase of SRG was used to verify that all systems had survived launch and no degradation in the functionality was present. In addition, the critical one-time operations of opening the telescope cover and cooling the CCD detectors to -90°C were carried out during this phase. The extreme reliance on the instrument controller (ITC) for the survival of the telescope, in addition to the thermal control an data handling systems that are under control of the ITC, make it pertinent to report on how these systems behaved in the initial phases of the mission. This paper presents an overview of the telescope operations during the early phase and commissioning that verified functionality of thermal and electrical systems and commissioned the cameras before the important Calibration and Pointed Verification phase started. In addition, it reports on the challenges encountered and summarizes the results from this phase of eROSITA operations.

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.

GRBAlpha is a 1U CubeSat mission with an expected launch date in the first half of 2021. It carries a 75 × 75 × 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 CAMELOT, i.e. the feasibility of timing-based localization

Despite the great success achieved by X-ray and gamma-ray observatories in the last two decades, the energy range between few hundreds keV and few MeVs remains poorly explored. COMPTEL, on board CGRO (1991- 2000), was the last telescope to explore the MeV domain, with a modest sensitivity. Many missions, like AMEGO, HERMES and ETCC have been proposed, in order to fill this gap in observations. However, the time-scale for development and launch of such big missions is around 10 years. Looking at this scenario, a nano-satellite Compton telescope, with small cost and relatively short development time, may be profitable for the immediate future. MeVCube is a 6 U CubeSat concept currently under investigation at DESY. The scientific payload is based on two layers of pixelated Cadmium-Zinc-Telluride (CdZnTe) detectors, coupled with low-power read-out electronics (ASIC, VATA450.3). We demonstrate through simulations that even such a small telescope could cover the energy range between hundreds keV up to few MeVs with a sensitivity comparable to that of missions like COMPTEL and INTEGRAL. Preliminary experimental studies of CdZnTe detectors with a custom pixelated anode design and read-out electronics are presented as well.

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.

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 High Energy Rapid Modular Ensemble of Satellites (HERMES) Technological and Scientific pathfinder is a space borne mission based on a constellation of LEO nanosatellites. The payloads of these CubeSats consist of miniaturized detectors designed for bright high-energy transients such as Gamma-Ray Bursts (GRBs). This platform aims to impact Gamma Ray Burst (GRB) science and enhance the detection of Gravitational Wave (GW) electromagnetic counterparts. This goal will be achieved with a field of view of several steradians, arcmin precision and state of the art timing accuracy. The localization performance for the whole constellation is proportional to the number of components and inversely proportional to the average baseline between them, and therefore is expected to increase as more. In this paper we describe the Payload Data Handling Unit (PDHU) for the HERMES-TP and HERMES SP mission. The PDHU is the main interface between the payload and the satellite bus. The PDHU is also in charge of the on-board control and monitoring of the scintillating crystal detectors. We will explain the TM/TC design and the distinct modes of operation. We also discuss the on-board data processing carried out by the PDHU and its impact on the output data of the detector.

Planned to launch in 2022, SPRITE is the first NASA-funded 12U cubesat for astrophysics science. SPRITE is equipped with unique hardware for a cubesat that enables it to simultaneously perform underexplored astrophysical observations and serve as a testbed to evaluate the in-space performance of experimental technologies that are candidates for implementation on future large missions. SPRITE will observe ultraviolet light from low-redshift galaxies and other targets of interest to provide data on emissions from these targets in a bandpass that has not been investigated exhaustively to date. An ultraviolet light photon-counting borosilicate glass microchannel plate detector is one of the experimental components that is unique to SPRITE among cubesats, and it motivates the uncommon requirement for a high voltage power supply on the particularly volume-limited spacecraft platform. This proceedings describes SPRITE’s electrical subsystems with a focus on the payload electronics that directly enable its science objectives with particular attention given to the design and planned laboratory experimental validation of the high voltage power supply needed to drive the detector. The planned Time-Tag and Accumulate data acquisition modes and the data products of these routines are also discussed.

MeV astronomy provides unique and direct diagnostics of cosmic explosions and chemical evolution. Gammaray lines provide detailed information on nuclear physics processes throughout the universe. New instruments sensitive to MeV gamma-ray lines are needed. A new instrument concept with high energy and angular resolution is proposed to study nuclear astrophysics in the medium gamma-ray energy range. The system consists of a 12U CubeSat carrying onboard CdZnTe detectors that will be placed in orbit around the moon. The Lunar Occultation Technique will be used to analyze the changes in counting rate during occultations of the moon to pinpoint the location of gamma-ray line flux at precise locations in the sky. The lack of lunar atmosphere, stable background, and low-mass spacecraft provides the perfect environment for high sensitivity gamma-ray spectroscopy and good angular resolution. Simulation studies using MCNP6 were used to determine the expected instrument eciency and lunar gamma-ray background environment. An initial simulation study indicates that the proposed instrument can achieve sensitivity to gamma-ray lines comparable to much larger proposed Compton Telescopes.

The Einstein Probe mission, due to launch in late 2022, will study time-domain astrophysics and monitor variable objects. It aims to observe x-ray counterparts of gravitational wave sources and high-redshift gamma ray bursts. Developed and built by the Chinese Academy of Sciences, Einstein Probe will use two types of telescope: the WideField X-ray Telescope (WXT) and the Follow-Up X-ray Telescope (FXT). The FXT will perform follow-up observations of sources discovered by the WXT, and will observe in the energy range of 0.5 to 8 keV. The performance aim of the FXT – the point spread function half-energy width (PSF HEW) – is <20 arcseconds (on-axis at 1.49 keV). The Max-Planck Institute for Extraterrestrial Physics (MPE) is producing and integrating the x-ray straylight baffle for the FXT, as well as testing and calibrating the different models of the FXT x-ray optic. Production of the structural-thermal model (STM) for Einstein Probe FXT began in 2019. The STM mirror module, produced by Media Lario, has been tested at MPE’s PANTER x-ray test facility. Following this acceptance test, further x-ray tests have been performed at PANTER after each of the subsequent stages: the mounting of the x-ray baffle, the shock and vibration test, and the thermal cycling test. The x-ray performance of the FXT STM is documented at each stage and the results of each test are presented in this paper.

The Einstein Probe (EP) is an X-ray astronomical mission mainly devoting to time-domain astronomy. There are two main scientific payloads onboard EP, the Wide Field X-ray Telescope (WXT) based on the lobster eye optics and the Follow-up X-ray Telescope (FXT). FXT contains two Wolter-1 mirrors with a pnCCD detector on each focus. The total effective area is about 600 cm2 and the energy range is 0.3-10 keV. The pnCCD detector cooled by a pulse tube cooler enables high-resolution spectroscopy and imaging combined with excellent time resolution. It will also have several working modes with time resolution ranging from tens of microseconds to 50 milliseconds. Currently, the FXT is in its qualification model phase. The mirror assemblies (STM and TCM) as well as the pnCCD EM module have been manufactured and tested.

Resolve onboard the X-ray satellite XRISM is a cryogenic instrument with an X-ray microcalorimeter in a Dewar. A lid partially transparent to X-rays is installed at the top of the Dewar along the optical axis, which is called the gate valve (GV). Because observations will be made through the GV for the first few months, the X-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission using the X-ray beamline at ISAS for the first time. For the Be window, we used synchrotron facilities to measure the transmission and modeled the data with (i) photoelectric absorption and incoherent scattering of Be, (ii) photoelectric absorption of contaminants, and (iii) coherent scattering of Be. We discuss the physical interpretation of the transmission discontinuity caused by the Bragg diffraction in poly-crystal Be, which we incorporated into our phenomenological model. The measurements and the constructed model meet the calibration requirements of the GV. We also performed a spectral fitting of the Crab nebula data observed with Hitomi SXS and confirmed improvements of the model.

The X-Ray Imaging and Spectroscopy Mission, XRISM, is scheduled to launch in 2022, with the goal of building on the brief successes of the ASTRO-H (Hitomi) mission, and recovering the prime science objective to solve outstanding astrophysical questions using high resolution X-ray spectroscopy. The XRISM Science Operations Team (SOT), consists of the JAXA-led Science Operations Center (SOC) and NASA-led Science Data Center (SDC) that work together to optimize the scientific output from the Resolve high-resolution spectrometer and the Xtend wide-field imager through planning and scheduling observations, processing and distribution of data, development and distribution of software tools and the calibration database (CaldB), user support, and support of ground and in-flight calibration. Here, we summarize the roles and responsibilities of the SDC, and the current status and future plans, covering scheduling software, software and CalDB production and release, data transmission and processing pipeline, and simulation and other post-pipeline analysis tools. Resolve poses particular challenges due to its unprecedented combination of high spectral resolution and throughput, broad spectral coverage, and relatively small field-of-view and large pixel-size; and, we highlight those challenges.

The XRISM is the astronomical mission to perform the high-resolution X-ray spectroscopy of astrophysical objects using the micro-calorimeter array. In order to enhance the scientific outputs of the mission, the science operations team (SOT) is structured with responsibilities of the spacecraft planning, data processing and distributions, development and maintenance of analyses software and calibration database, and users’ supports. The operation concepts are established based on lessons learned from past X-ray missions. The SOT consists of the Science Operations Center at JAXA and the Science Data Center at NASA. Details of science operations plan and preparation status on SOC are summarized.

FORCE (Focusing On Relativistic universe and Cosmic Evolution) is a future Japan-lead X-ray mission in study to achieve wide-band (1-80 keV) coverage with good (15’’ half-power-diameter, HPD) angular resolution, to uncover high energy phenomena currently difficult to access because of strong absorption and/or overlaid thermal emission. The science instrument onboard FORCE is a pair of high-resolution super-mirrors, and wide-band imaging spectrometers, placed with a focal length distance of 12 m. WHXI is designed to achieve high sensitivity, and therefore low background level of 1-3 x 10-3 counts s^-1 cm^-2. Low and stable background is important especially for diffuse source analysis, and it also contributes to achieve good sensitivity against dim point sources. With this aim, the basic concept of FORCE/WHXI is based on Hitomi/HXI heritage, which has achieved the lowest ever background in 5 to ~30 keV band in orbit. The imager is made of a hybrid X-ray imager and active shield surrounding it. The former consists of a newly developed Si imager (XRPIX) to cover 1-25 keV, and a CdTe imager (CdTe-DSD, a heritage of Hitomi/HXI), to cover 20-80 keV, stacked in tandem. The active shield is made of 3-4 cm thick BGO scintillator crystal covering almost 4-pi radian around the imagers. Lessons learned from both NuSTAR FPMA and Hitomi/HXI will be incorporated in WHXI.

We propose an optimized source detection algorithm with an X-ray wide-field imaging detector based on lobstereye (LE) optics to realize better sensitivity. In our method, we take two parts of region of interest (ROI) in which we test the number of X-ray events exceed a certain threshold level. Since we compose the condition that the excesses of the photons are required for the both parts of the ROI, we can lower the detection threshold level with a less false alert rate. We take two comparative methods in which the ROI consists of one part, and compared the performance of them. We formulated an appropriate threshold level and sensitivity for two comparable detection methods as well as our proposed method. We found that the detection sensitivity of our method is improved by a factor of about 30% at most than that of the comparable methods in the nominal case of the proposed HiZ-GUNDAM mission. We also found that which detection method has better sensitivity depends on the background event rate. We checked that the formulation works well by comparing to a Monte Carlo simulation in the case of the HiZ-GUNDAM condition. The formula can be applied to any future missions with LE optics to design which detection algorithm is suitable for optimizing sensitivity.

In this paper we report on development of an FPGA-based fast readout system of a CMOS image sensor for the future satellite mission HiZ-GUNDAM observing gamma-ray bursts (GRBs) in the 0.4–4 keV band. Since the typical durations of GRBs are about 0.1–100 s, an X-ray photon-counting capability with a time resolution of < 0.1 s is required. The FPGA-based signal processing system has the following functions: (1) take images with a few million pixels at a frame rate of >10 frames per second, (2) extract X-ray events by image subtraction, (3) compile position and energy information of the obtained X-ray events, and (4) transfer the information to an external CPU. A more detailed system configuration is reported.

We are studying an improved DIOS (Diffuse Intergalactic Oxygen Surveyor) program, Super DIOS, which is accepted for establishing the Research Group in ISAS/JAXA, for a launch year after 2030. The aim of Super DIOS is an X-ray quantitative exploration of ”dark baryon” over several scales from circumgalactic medium, cluster outskirt to warm-hot intergalactic medium along the Cosmic web with mapping redshifted emission lines from mainly oxygen and other ions. These observations play key roles for investigating the physical condition, such as the energy flow and metal circulation, of most baryons in the Universe. This mission will perform wide field X-ray spectroscopy with a field of view of about 0.5–1 degree and energy resolution of a few eV with TES microcalorimeter, but with much improved angular resolution of about 10–15 arcseconds. We will also consider including a small gamma-ray burst monitor and a fast repointing system. We will have an international collaboration with US and Europe for all the onboard instruments.

We propose a novel concept of a ultracompact hard X-ray imaging polarimeter system that utilizes the combination of a fine-pixel CMOS imaging sensor and a narrow field-of-view coded aperture mask with multiple different random patterns. An instrument using this concept can be installed in the cost-effective 6U CubeSat mission cipher, providing us a quick opportunity to demonstrate potentials of the semiconductor photoabsorption-type polarimeter by realizing imaging polarimetry of the brightest objects in an energy band of 10–30 keV. Polarization of this energy band, which is the lower part of hard X-rays, has been unexplored in spite of its great scientific importance. The science targets of cipher include particle acceleration at relativistic shocks in the Crab Nebula, the accretion flow geometry in Cygnus X-1, and the anisotropy of electrons accelerated by bright solar flares. We show by proof-of-concept experiments in SPring-8 that a CMOS sensor with a pixel size of 2.5 µm has polarization sensitivity at energies of 10, 16, and 24 keV with modulation factors of 4.24% ±0.03%, 11.82%±0.06%, and 15.15%±0.25%, respectively. We also demonstrate that the coded aperture imaging with the different random patterns achieves artifact-reduced image decoding with an angular resolution of 30 arcseconds. The combination of these methods can be naturally extended to imaging polarimetry with high energy and angular resolutions.

XL-Calibur is a balloon-borne hard X-ray polarimetry mission, the first flight of which is currently foreseen for 2021. XL-Calibur carries an X-ray telescope consists of consists of 213 Wolter I grazing-incidence mirrors which are nested in a coaxial and cofocal configuration. The optics design is nearly identical to the Hard X-ray Telescope (HXT) on board the ASTRO-H satellite. The telescope was originally fabricated for the Formation Flying Astronomical Survey Telescope (FFAST) project. However, the telescope can be used for XL-Calibur, since the FFAST project was terminated before completion. The mirror surfaces are coated with Pt/C depth-graded multilayers to reflect hard X-rays above 10 keV by Bragg reflection. The effective area of the telescope is larger than 300 cm^2 at 30 keV. The mirrors are supported by alignment bars in the housing, and each of the bars has a series of 213 grooves to hold the mirrors. To obtain the best focus of the optics, the positions of the mirrors have to be adjusted by tuning the positions of the alignment bars. The tuning of the mirror positions is conducted using the X-ray beam at the synchrotron facility SPring-8 BL20B2, and this process is called optical tuning. First the positions of the second reflectors are tuned, and then those of the first reflectors are tuned. We did the first optical tuning in Jan 2020. The second tuning will be planned between April to July, 2020. This paper reports the current status of the hard X-ray telescope for XL-Calibur.

The Imaging X-Ray Polarimetry Explorer (IXPE) is the next NASA small explorer mission, due to be launched on May 2021. It will perform polarization measures of soft X-ray photons (∼ 2 − 8keV), together with imaging, spectroscopy, and timing. The core of the detector units is the Gas Pixel Detector (GPD) with dedicated back-end electronics (BEE). We designed the latter with a radiation-tolerant FPGA for data acquisition and processing, event sequencing, and on-line data compression. Two custom digital serial interfaces implement the communication of the units with a central on-board computer: Command and Control Interface and Science Data Interface. This BEE exploits the auto-trigger capability of the GPD and can process its output of 300 photons per second with 30% of system dead time. We designed comprehensive test-equipment to emulate the on-board computer. It is based on a commercial FPGA on a VME-board together with dedicated software for control and data collection

We present the first application of a time projection chamber polarimeter to measure high energy X-ray polarization above 10 keV. The polarimeter is designed based on the PRAXyS soft X-ray polarimeter. The sealed gas is changed to a gas mixture of 60% argon and 40% dimethyl ether at 1 atm to be sensitive to high energy X-rays. The polarimeter performance is verified with linearly polarized, monochromatic X-rays at a synchrotron radiation facility, KEK Photon Factory BL-14A. The measured modulation factors are 42.4 ± 0.6%, 50.4 ± 0.6%, and 55.0 ± 0.6% at 12, 14, and 16 keV, respectively, and the measured polarization angles are consistent with the expected values at all energies.

We present an update on our work measuring the performance and alignment of the critical-angle transmission (CAT) gratings for the proposed sounding Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX) mission, as well as a possible orbital version. We built and verified a grating alignment system that could be used for REDSoX Polarimeter fabrication. The performances of the gratings were measured using the MIT polarimetry beamline. The beamline is a monochromator and has been used to measure the absolute efficiencies of not only the REDSoX prototype gratings but also the Arcus Phase A gratings. It is also capable of producing and measuring polarized soft X-rays to aid in the development and testing of future missions. Lastly, we present an update on our effort applying twisted crystals to X-ray polarimetry. Support for this work was provided in part by the NASA grant NNX15AL14G and a grant from the MIT Kavli Institute Research Investment Fund.

X-ray polarimetry is still largely uncharted territory. With the upcoming launch of IXPE, we will learn a lot more about X-ray polarization at energies above 2 keV, but so far no current or accepted mission provides observational capabilities below 2 keV. We present ray-tracing results for a small orbital mission that could be launched within NASA’s Pioneer or SmallSat cost-cap to provide X-ray polarimetry below 2 keV. The design is based on the use of laterally-graded multi-layer (ML) mirrors, a concept that we have developed theoretically for the REDSoX Polarimeter,¹ for which most components have been verified in the laboratory. In this contribution, we describe a single channel orbital mission based on the same idea, but modified to the unique cost and space requirements. All results scale up easily to two or more polarimetry channels. Scaling up would simply increase the effective area and reduce the need to rotate the instrument to measure the different polarization directions. In particular, we use the ray-traces to define the maximum size of the dispersion gratings and to determine an alignment budget.

The Imaging X-ray Polarimetry Explorer (IXPE) is a scientific observatory with the purpose of expand observation space adding polarization property to the X-ray sourceƒ_Ts currently measured characteristics. The mission, selected in the context of NASA Small Explorer (SMEX) is a collaboration between NASA and ASI that will provide to observatory the instrumentation of focal plane. IXPE instrument is composed by three photoelectric polarimeter based on the Gap Pixel Detector (GPD) design, integrated by INFN inside detector unit (DU) that comprises all the electrical interfaces required to control and communicate with GPD. The three DUs are interfaced with spacecraft through a de-tector service unit (DSU) that collect scientific and ancillary data and provides a basically data handling and interfaces to manage the three DUs. AIV has been planned to combine calibration of DUs and Instrument integration and veri-fication activities. Due the tight schedule and the scientific and functional requirements to be verified, in IAPS/INAF have been assembled two equipments that work in parallel. The flight model of each DU after the environmental tests campaign was calibrated on-ground using Instrument Calibration Equipment (ICE) and subsequently integrated in the instrument in the AIV-T process on a AIV and Calibration Equipment (ACE), both the facilities managed by Electrical Ground Support Equipment (EGSE) that emulate the spacecraft interfaces of power supply, functional and thermal control and scientific data collection. AIV activities test functionalities and nominal/off-nominal orbits activities of IXPE instrument each time a calibrated DU is connected to DSU flight model completing step by step the full instrument. Here we describe the details of instrumentation and procedures adopted to make possible the full integration and test activities compatibly with calibration of IXPE Instrument.

IXPE, the Imaging X-ray Polarimetry Explorer, is a NASA SMEX mission with an important contribution of ASI that will be launched with a Falcon 9 in 2021 and will reopen the window of X-ray polarimetry after more than 40 years. The payload features three identical telescopes each one hosting one light-weight X-ray mirror fabricated by MSFC and one detector unit with its in-orbit calibration system and the Gas Pixel Detector sensitive to imaging X-ray polarization fabricated by INAF/IAPS, INFN and OHB Italy. The focal length after boom deployment from ATK-Orbital is 4 m, while the spacecraft is being fabricated by Ball Aerospace. The sensitivity will be better than 5.5% in 300 ks for a 1E-11 erg/s/cm² (half mCrab) in the energy band of 2-8 keV allowing for sensitive polarimetry of extended and point-like X-ray sources. The focal plane instrument is completed, calibrated and it is going to be delivered at MSFC. We will present the status of the mission at about one year from the launch.

IXPE (Imaging X-ray Polarimetry Explorer) is a NASA SMEX in a partnership with ASI. The focal plane Detector Units (DUs) and the Detector Service Unit (DSU) were developed by the Italian research Institutes INAF-IAPS and INFN and were manufactured by OHB-I. IXPE will investigate X-ray polarimetry in the 2-8 keV energy band. The payload comprises three identical telescopes, each composed of a mirror and a detector unit with an X-ray polarimeter based on the Gas Pixel Detector (GPD). A stray-light collimator (SLC) is mounted on the top of the DU to shield the GPD from background X-rays not coming from the optics. At the bottom of the SLC, an ions-UV filter is mounted to reduce the thermal load and to prevent ions and UV from entering the DU. The ions-UV filters consist mainly of 1 um LUXFilm (based on polyimide). During on-ground calibration activities of the IXPE DUs, X-ray transparency of DU-FM ions-UV filters was measured with monochromatic X-ray at 2.7 keV and 6.4 keV at INAF-IAPS.

IXPE (Imaging X-ray Polarimetry Explorer) is the next Nasa Small Explorer mission foreseen for the lunch in 2021. It is a partnership with the Italian Space Agency (ASI). IXPE is devoted to X-ray polarimetry in the 2-8 keV energy band. The IXPE telescope comprises three grazing incidence mirror modules coupled to three detector units hosting each one a Gas Pixel Detector (GPD) polarimeter. The GPD exploits the photoelectric effect to measure the linear polarization of the X-ray emission from astrophysical sources. A wide and accurate on ground calibration was carried out on the IXPE detector units at INAF-IAPS in Italy. A dedicated facility was set-up to calibrate the detector units with polarized and unpolarised X-rays at different energies before Instrument integration.

MeV gamma-ray astronomy in an energy range of hundreds of keV to tens of MeV is a unique window for observing nucleosynthesis, however this field has not opened up until recently because of imaging difficulties. Thus, we are developing an electron-tracking Compton camera (ETCC), which consists of a gaseous electron tracker and pixel scintillator arrays, as a next generation MeV gamma-ray telescope. Because the ETCC detects all parameters after Compton scattering, we can determine the momentum of incident gamma-rays with powerful background rejection. This ETCC has confirmed low-noise and high-sensitivity observations at high altitude through Sub-MeV gamma-ray Imaging Loaded-on-balloon Experiment I (SMILE-I) in 2006 and SMILE-2+ in 2018. Therefore, we are planning scientific observations using an ETCC with an effective area of ∼10 cm² for 0.3 MeV, a spatial resolution of ≤10 degrees for 0.5 MeV, and a field of view of 3 sr as the next step (SMILE-3). In this paper, we present the design of the SMILE-3 ETCC and its expected observations.

This paper describes a trigger system for the ComPair instrument. For an incident event, each detector subsystem initiates data digitization process with its internal hit signal and sends the hit signal to the trigger module. The trigger module generates a trigger acknowledge signal from combinations of subsystem hit information to select gamma-ray events and unbiased sampled events. The trigger module also generates an event identification number for each acknowledged event and sends to each subsystem to reconstruct the event afterward. We employed an FPGA development board (ZC706, Xilinx) as a main body of the trigger module and developed an FPGA Mezzanine Card to interface with each subsystem. The peta-linux runs on the FPGA controls the trigger module. Two TCP servers on the linux handles commanding and data transfer from/to a DAQ machine. We confirmed that the trigger module could accept event rates up to 12 kHz with Lenovo ThinkPad T340S. The communication test with the other subsystems are ongoing for the upcoming beam test and a balloon flight.

Observing cosmic sources in the medium-energy gamma-ray regime (∼0.4 - 10 MeV) will require a highly efficient instrument with good angular resolution and background rejection. Artificial single-crystal diamond detectors (SCDDs) have comparable energy ranges, energy resolution, and threshold levels as traditional silicon solidstate detectors (SSDs), but with faster rise times, improved radiation hardness, and insensitivity to light and temperature. CeBr₃ scintillator is a high density, high Z material with fast rise times and good energy resolution make it a promising gamma-ray calorimeter. This work outlines ongoing work at Southwest Research Institute (SwRI) to develop readout and data acquisition electronics to characterize SCDDs. Additionally, work is ongoing at Los Alamos National Laboratory to characterize CeBr₃ scintillator detectors that are read out with silicon photomultipliers (SiPMs) and recorded via an off the shelf ASIC system (TOFPET ASIC), developed for timeof-flight (ToF) positron emission tomography. The ultimate goal of the project is to individually characterize SCDDs and CeBr₃ and bring them together to form a prototype Compton telescope, which will benchmark simulations of a functional diamond Compton telescope and predict the sensitivity of an optimized instrument for a satellite platform.

The detection of astrophysical Gamma-Ray Bursts (GRBs) has always been intertwined with the challenge of identifying the direction of the source. Accurate angular localization of better than a degree has been achieved to date only with heavy instruments on large satellites, and a limited field of view. The recent discovery of the association of GRBs with neutron star mergers gives new motivation for observing the entire γ-ray sky at once with high sensitivity and accurate directional capability. We present a novel γ-ray detector concept, which utilizes the mutual occultation between many small scintillators to reconstruct the GRB direction. We built an instrument with 90 (9 mm)3 CsI(Tl) scintillator cubes attached to silicon photomultipliers. Our laboratory prototype tested with a 60 keV source demonstrates an angular accuracy of a few degrees for ∼25 ph cm⁻² bursts. Simulations of realistic GRBs and background show that the achievable angular localization accuracy with a similar instrument occupying 1l volume is < 2° . The proposed concept can be easily scaled to fit into small satellites, as well as large missions.

POLLUX is a project of high-resolution UV spectropolarimeter for the prospective LUVOIR space observatory. It will work in the range of 90-400 nm with R ≥ 120000. The baseline design consists of 3 channels representing echelle spectrographs with dedicated polarimeters, customized echelles and freeform-based concave holographic gratings. We study the requirements for manufacturing and assembly precision. We consider three performance criteria related to the spectral resolving power, calibration stability, and the gratings diffraction efficiency. We perform the tolerance analysis in corresponding modes using raytracing and numerical methods of diffraction modelling in a Monte-Carlo loop. We emphasize the most influential design parameters, which may require high precision of manufacturing and alignment and should be the subjects of further studies. We also briefly discuss possible compensators for maintenance of the imaging performance.

Spectr-UV/WSO-UV is the third and last of the Spektr missions (Spektr-Radio, Spektr-RG, Spektr-UF), space-based observatories, of the Russian Scientific Space Program. Spektr-UF/WSO-UV is a 2-m class ultraviolet (UV) observatory to be set in geosynchronous orbit in 2025 from the Vostochny launching pad. The observatory is equipped with instrumentation for UV spectroscopy and imaging. The Universidad Complutense de Madrid together with Institute of Astronomy of the Russian Academy of Sciences are developing jointly the imaging instrument for the mission. The instrument has a UV-optical channel designed for wide field imaging from 174 to 600 nm and a far UV (FUV) channel for high resolution imaging in the 115-175 nm range. Also, some low dispersion spectroscopic capabilities are available in the FUV channel. In this contribution, the characteristics and architecture of the MCP detector being developed by Spain for the FUV channel are described.

Within the Space Situational Awareness Programme (SSA), ESA has initiated the assessment of two missions currently considered for implementation to enable enhanced space weather monitoring capabilities of ESA. These missions will position satellites at the Lagrangian points L1 and L5. Phases A and B1 with a focus on the L5 mission are now completed and the Bridging Phase studies are now initiated. The Lagrange mission to L5 considers four remote sensing optical instruments and several in-situ instruments to analyze the Sun, the energetic particle streams, the magnetic field and solar wind conditions, in order to provide early warnings of increased solar activity. Within this frame, an Extreme UltraViolet Imager (EUVI) instrument is under study to image the full solar corona. The overall Remote Sensing Instruments study will be led by RAL (GB). In particular, the EUVI study is carried out by three institutes - CSL (BE), ROB (BE) and PMOD/WRC (CH) - and is built upon the heritage of previous projects such as PROBA2/SWAP, ESIO and SolO/EUI to which CSL contributed. The work is shared between CSL, ROB and PMOD with the following responsibilities: - CSL: overall management, system study, optical engineering, thermal engineering, - PMOD: electrical engineering, mechanisms and mechanical engineering - ROB: instrument requirements, instrument operation, ground segments Several EUV imaging telescopes have been developed for scientific solar spacecraft, e.g. SOHO/EIT, TRACE, Proba-2/SWAP, STEREO/SECCHI-EUVI, SOLAR ORBITER/EUI. Another study called ESIO, based on an ESA General Support Technology Programme activity (GSTP), was also performed until 2015 jointly by the Centre Spatial de Liège (CSL) and the Royal Observatory of Belgium (ROB). The name of the instrument designed in that frame was the EUV Solar Imager for Operations (ESIO). The ESIO instrument was intended to provide solar EUV images for operational use as part of the ESA SSA (Space Situational Awareness) programme. The ESIO design is a low resolution, low data rate, compact solar EUV imager associated to a flux monitor for operation use in space weather monitoring and forecasting. The EUVI instrument intends to image the full solar disc, in a single spectral line as the requirement and multiple lines as a goal. The idea for this instrument is to combine heritages from SWAP, ESIO and SolO/EUI to benefit from the experience CSL gained during those projects. The optical design of its telescope originates from PROBA-2/SWAP: it consists of a two-mirror telescope imaging the Sun to a focal plane assembly. The actual structural solution also benefits from the SWAP heritage: a simple optical bench onto which the optical elements will be attached. Within Lagrange, the global philosophy is indeed to re-use as much as possible heritage from previous missions and limit the amount of new development. The previous accommodation of SWAP has however been updated to fit with the new optical design characteristics and benefits from some updates coming from SolO/EUI. The spectral selection is achieved with a set of aluminum foil filters, together with EUV reflective multilayer coatings deposited on the mirrors. The overall stack is specifically designed to provide reflectivity in the extreme ultraviolet range, and to achieve the spectral selection in the selected narrow band pass (1.5 nm at full width half maximum). The accuracy on central wavelength adjustment is within +/- 0.2 nm. The focal plane assembly comprises an EUV CMOS detector coming from the spare list of SolO/EUI. A decontamination heater located on the sensor will be used periodically to outgas the condensed layer that builds up on the cold sensor. Cleanliness of such EUV instrument is indeed critical as molecular deposits can absorb EUV radiation and dramatically decrease photon throughput. The focal plane assembly also includes the proximity electronics (FEE) required to readout the sensor and a thermal link to the cold space for the detector cooling down. An overview on the technical development and decisions taken will be presented during the presentation to highlight the tight relation between the design selection, user requirements, interfaces and cost/schedules aspects.

Remote sensing of Earth at ultraviolet wavelengths offers the capability to retrieve key environmental parameters that provide remarkable insight into space weather conditions. The miniaturized UV imager (MUVI) instrument is a currently funded NASA technology development effort that expands on capability developed from recent flight experience to build and qualify a small, relatively simple UV imager that can be tuned for a range of purposes. The goal is to revisit earlier designs of suppressive imagers, obviating the need for gratings, slits, and long optical paths, redeveloping a direct imaging capability in a CubeSat type form-factor. Combining high heritage components with improved imaging technologies, MUVI provides science performance comparable to high-performance imagers developed and flown for prior research missions at much lower mass and cost points. A compelling scientific design for future missions will be to make space-based observations from multiple vantage points from one or more orbit planes. Multiple-observatory mission designs, including those implemented using the CubeSat form-factor, are more accessible now due to a great deal of research and commercial work toward miniaturization of spacecraft subsystems. It is likely that small scientific payloads will greatly benefit upcoming Heliophysics missions if appropriate technologies are developed. An overview of the MUVI instrument is described here, along with development status after year 1 of funding.

The ozone layer has a complex spectral absorption profile at NUV wavelengths. It is dependent on seasonal effects due to solar intensity, as well as atmospheric circulation of the ozone layer. Getting above this then becomes imperative for getting a usable SNR for scientific observations. GLUV is an affordable, long duration, high altitude balloon experiment which will fly a network of NUV telescopes at altitudes of 20-30 km. GLUV Pathfinder is a spectrometer based system to identify the sky background in the NUV, measuring this as a function of altitude, latitude, and seasonal phase in the regimes that the final GLUV project will experience. The development of dedicated NUV instrumentation is highly important for supernovae astronomy, as these higher energy wavelengths reveal their initial detonation conditions. GLUV is expected to capture the initial shocks of these events at a rate of 10+ per year of operation, well in excess of the few instances that have been seen to date

Chromospheric LAyer Spectro-Polarimeter (CLASP2) was a sounding rocket experiment, which is a follow-up mission to the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP1) in 2015. To measure the magnetic fields in the upper solar atmosphere in a highly quantitative manner, CLASP2 changes the target wavelengths from the hydrogen Ly-α line (121.567 nm) to Mg II lines near 280 nm. We reused the main structure and most of the optical components in the CLASP1 instrument, which reduced the turnaround time and cost. We added a magnifying optical system to maintain the wavelength resolution, even at the longer wavelength of CLASP2. Here, we describe the optical design and performance of the CLASP2 instrument.

Digital micromirror devices (DMDs) can be used as versatile, rapidly reconfigurable object selectors in spacebased multi-object spectrographs (MOS). DMDs are inexpensive, compact, reliable, high-throughput devices, that enable extremely flexible and efficient multi-object spectrographs; several DMD-based MOSs are currently being built for 4 m class ground-based telescopes. Previously, we have shown that DMDs are suitable for deployment and operation in space, in the near-UV and optical regimes (200 - 1000 nm). Using aluminum coatings protected with LiF and LiF/AlF3 films, we aim to extend the operational range of DMDs into the 100 - 200 nm FUV regime. Our initial coating runs produced DMDs with reflectivity > 40% in the range of 110 - 180 nm. Critically, the DMDs remain operational after the coating process. We will discuss potential for further improvement and introduce several mission concepts based on a FUV/NUV DMD MOS, that can be deployed on CubeSat and ESPA-class missions.