This PDF file contains the front matter associated with SPIE Proceedings Volume 11118, including the title page, copyright information, table of contents, and author and conference committee lists.

A germanium charge-coupled device (CCD) offers the advantages of a silicon CCD for X-ray detection – excellent uniformity, low read noise, high energy resolution, and noiseless on-chip charge summation – while covering an even broader spectral range. Notably, a germanium CCD offers the potential for broadband X-ray sensitivity with similar or even superior energy resolution than silicon, albeit requiring lower operating temperatures (≤ 150K) to achieve sufficiently low dark noise due to the lower band gap of this material. The recent demonstration of high-quality gate dielectrics on germanium with low surface-state density and low gate leakage is foundational for realization of high-quality imaging devices on this material. Building on this advancement, MIT Lincoln Laboratory has been developing germanium CCDs for several years, with design, fabrication, and characterization of kpixel-class front-illuminated devices discussed recently. In this article, we describe plans to scale these small arrays to megapixel-class imaging devices with performance suitable for scientific applications. Specifically, we discuss our efforts to increase charge-transfer efficiency, reduce dark current, improve fabrication yield, and fabricate backside-illuminated devices with excellent sensitivity.

We discuss the joint development by Penn State University (PSU) and Teledyne Imaging Systems (TIS) of hybrid CMOS detectors for X-ray astronomy, and specifically the development over the past 10 years of a new event-driven X-ray detector for future astronomy missions. This novel X-ray detector is designed to perform onchip event recognition and to read out only pixels containing X-ray events. With the exception of analog power supply voltages, the detector is digital in/digital out, reducing off-chip electronics to a minimum. It operates at frame rates of over 1000 frames per second, providing excellent performance for bright X-ray sources and/or high-throughput optics. The pixel size is 40 × 40 microns, and we are fabricating devices with 550 × 550 pixels.

Understanding the effects of high energy proton radiation is essential in planning for the next generation of X-ray space telescopes. We report on the results of an experiment in which an X-ray hybrid CMOS detector was incrementally irradiated with 8 MeV protons up to a total absorbed dose of approximately 3 krad(Si) (4.5 x 109 protons/cm2). The effect of the damage caused by the high energy protons is then analyzed in the context of several detector characteristics, including read noise, dark current, and energy resolution.

The High Resolution Energetic X-ray Imager (HREXI) is a coded-aperture imaging telescope that utilizes tiled CdZnTe (CZT) detectors to image cosmic x-ray sources and transients in the 3-200 keV energy band. A closely tiled array of 256 pixellated CZT detectors form the 1024 cm^2 detector plane of a proposed (Grindlay et al. 2019) SmallSat mission. This close tiling of the crystal units is achieved by Through-Silicon-Via (TSV) enabled readout ASICs that shrink the readout electronics footprint of the wire-bonded ASICs previously developed and incorporated on the Nuclear Spectroscopic Telescope Array (NuSTAR) mission. To close-tile large numbers of detectors, an efficient die-level ASIC screening method is required for the TSV-ASICs. The ASIC Test Stand (ATS) was developed (Violette et al. 2018, SPIE Proceedings) in order to enable rapid testing of die-level TSV-ASICs by precision alignment of a fixed array of spring-loaded pogo-pin probes to connect to the ASIC's 87 pads with a 225 micron pitch. Here we report ATS design improvements and results from testing ASIC energy resolution and stability using the commandable test pulser internal to the ASIC. Multiple ATS systems will enable rapid testing and selection of ASICs for large area detector arrays as needed for the HREXI SmallSat Prototype (HSP).

The Smithsonian Astrophysical Observatory (SAO) in collaboration with SRI/Sarnoff has been developing monolithic CMOS imaging detectors that are intended for use as X-ray imaging spectrometers for over a decade. The ultimate goal of this joint effort is to produce X-ray Active Pixel Sensor (APS) detectors that are Fano-limited over the entire 0.1-10keV band while incorporating the benefits of CMOS technology. These benefits include: low power consumption, radiation “hardness”, high levels of integration, and very high read rates. A large format Fano-limited CMOS imager would be ideal for large “facility class” missions such as Lynx. Similarly, since CMOS devices are simple to operate (e.g require little to no cooling), they would also be ideal for smaller, resource limited, X-ray applications such as “SmallSat” missions. SmallSats represent more immediate opportunites to both demonstrate nascent technologies while carrying out meaningful but typically narrowly defined science missions. SAO and SRI have produced 1k by 1k format back-thinned, CMOS devices with 16μm pitch, 6 Transistor Pinned Photo Diode (6TPPD) pixels with ~135μV/electron sensitivity. The device known as the Big Minimal III (BMIII) is optimzed for X-ray photon counting applications. The high sensitivity pixel ensures that even low energy (100eV) x-rays produce a macroscopic voltage at the pixel. The detectors incorporate a versatile, parallel and therefore very fast signal chain. These BMIII detectors are fabricated on 10μm epitaxial silicon so the thickness to pixel pitch ratio is small; this increases the number of single pixel X-ray events.

Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a solar physics mission concept that was selected as a candidate for JAXA competitive M-class missions in July 2018. The onboard science instrument, EUVST, is an EUV spectrometer with slit-jaw imaging system that will simultaneously observe the solar atmosphere from the photosphere/chromosphere up to the corona with seamless temperature coverage, high spatial resolution, and high throughput for the first time. The mission is designed to provide a conclusive answer to the most fundamental questions in solar physics: how fundamental processes lead to the formation of the solar atmosphere and the solar wind, and how the solar atmosphere becomes unstable, releasing the energy that drives solar flares and eruptions. The entire instrument structure and the primary mirror assembly with scanning and tip-tilt fine pointing capability for the EUVST are being developed in Japan, with spectrograph and slit-jaw imaging hardware and science contributions from US and European countries. The mission will be launched and installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in 2025. ISAS/JAXA coordinates the conceptual study activities during the current mission definition phase in collaboration with NAOJ and other universities. The team is currently working towards the JAXA final down-selection expected at the end of 2019, with strong support from US and European colleagues. The paper provides an overall description of the mission concept, key technologies, and the latest status.

The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) flux from the host star. The EUV flux likely controls the demographics of the short-period planet population as well the ability for rocky planets to maintain habitable environments long enough for the emergence of life. We present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, an astrophysics Small Explorer proposed to NASA. ESCAPE employs extreme- and far-ultraviolet spectroscopy (70 - 1800 Α) to characterize the highenergy radiation environment in the habitable zones (HZs) around nearby stars. ESCAPE provides the first comprehensive study of the stellar EUV environments that control atmospheric mass-loss and determine the habitability of rocky exoplanets. The ESCAPE instrument comprises an EUV grazing incidence telescope feeding four diffraction gratings and a photon-counting detector. The telescope is 50 cm diameter with four nested parabolic primary mirrors and four nested elliptical secondary mirrors, fabricated and aligned by NASA Marshall Space Flight Center and the Smithsonian Astrophysical Observatory. The off-plane grating assemblies are fabricated at Pennsylvania State University and the ESCAPE detector system is a micro-channel plate (MCP; 125mm x 40mm active area) sensor developed by the University of California, Berkeley. ESCAPE employs the versatile and high-heritage Ball Aerospace BCP-100 spacecraft.

We are reporting on the development of the next generation 2D programmable field masks for the UV/visible multi-object spectroscopy. The devices have their legacy in the JWST microshutter NIRSpec magnetically actuated MEMS microshutters. A new fabrication process has been developed to actuate microshutter arrays electrostatically thus eliminating the need for the macroscopic mechanisms and improving the reliability and robustness of the device. The microshutters, made with silicon nitride membranes with a pixel size of 100 x 200 μm^2, rotate on torsion bars. The microshutters are actuated, latched, and addressed electrostatically by applying voltages on the electrodes the front and back sides of the microshutters. We have successfully fabricated and demonstrated actuation and addressing of these devices. Microshuter arrays are programmable field selector masks for optical spectrocopy based on MEMS technology. The original device was developed as part of the NIRSpec (Near Infrared Spectrometer) instrument for JWST (Jame Webb Space Telescope. The devices were designed for: random access addressing of the individual pixels in large format (365x721 elements), high contrast optical blocking > 1e4 operate in UV and visible, long life time for the operation of 20,000 cycles or more.

The Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX Polarimeter) is a sounding rocket instrument that can make the first measurement of the linear X-ray polarization of an extragalactic source in the 0.2-0.5 keV band as low as 10%. We employ multilayer-coated mirrors as Bragg reflectors at the Brewster angle. By matching the dispersion of a dispersive spectrometer using critical angle transmission gratings to three laterally graded multilayer mirrors (LGMLs), we achieve polarization modulation factors over 90%. We will describe new prototyping work as well as extensions of the design for an orbital version. This work was supported in part by NASA grants NNX15AL14G and NNX17AE11G to develop the design for a soft X-ray polarimeter.

The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of suborbital rocket payloads being developed at The Pennsylvania State University. The tREXS science instrument is a soft X-ray grating spectrometer that will provide a large field-of-view and unmatched spectral resolving power for extended sources. Each instrument channel consists of a passive, mechanical focusing optic and an array of reflection gratings. The focal plane consists of an array of CIS113 CMOS sensors. tREXS I is currently in the design phase and is being developed for a launch in 2021 to observe diffuse soft X-ray emission from the Cygnus Loop supernova remnant. An analysis of instrument optics, gratings, and focal plane camera is discussed.

The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of sub-orbital rocket payloads that will aim to make large field-of-view spectroscopic observations of diffuse soft X-ray astrophysical objects. The tREXS payloads will passively focus X-rays onto a co-aligned array of reflection gratings, dispersing the incident X-rays onto a focal plane camera. The large focal plane requires the detector to cover a large area (100s of mm), have good quantum efficiency across the soft X-ray energy range (300 eV to 1000 eV), and survive the high-stress environment of a sub-orbital rocket launch. This paper will look at the options that were considered for this focal plane detector including Micro-Channel Plates, Charge-Coupled Devices, and CMOS detectors; including the use of commercially available camera solutions from companies such as Andor. The final choice for the focal plane camera will then be discussed in detail including the ultimate decisions behind the choice, system level integration into the payload design, and the requirements on the readout electronics, telemetry interface, and power.

The Water Recovery X-ray Rocket (WRXR) mission was a sounding rocket flight that targeted the northern part of the Vela supernova remnant with a camera designed to image the diffracted X-rays using a grating spectrometer optimized for OVII, OVIII, and CVI emissions. The readout camera for WRXR utilized a silicon hybrid CMOS detector (HCD) with an active area of 36.9  36.9 mm. A modified H2RG X-ray HCD, with 1024  1024 active silicon pixels bonded to the H2RG read-out integrated circuit, was selected for this mission based on its characteristics, technology maturation, and ease of implementation into the existing payload. This required a new camera package for the HCD to be designed, built, calibrated, and operated. This detector and camera system were successfully operated in-flight and its characteristics were demonstrated using the on-board calibration X-ray source. In this paper, a detailed description of this process, from design concept to flight performance, will be given. A full integrated instrument calibration will also be discussed, as well as the temperature dependency measurements of gain variation, read noise, and energy resolution for the HCD.

The first detected exoplanets found were "hot Jupiters"; these are large Jupiter-like planets in close orbits with their host star. The stars in these so-called "hot Jupiter systems" can have significant X-ray emission and the X-ray flux likely changes the evolution of the overall star-planetary system in at least two ways: (1) the intense high energy flux alters the structure of the upper atmosphere of the planet - in some cases leading to significant mass loss; (2) the angular momentum and magnetic field of the planet induces even more activity on the star, enhancing its X-rays, which are then subsequently absorbed by the planet. If the alignment of the systems is appropriate, the planet will transit the host star. The resulting drop in flux from the star allows us to measure the distribution of the low-density planetary atmosphere. We describe a science mission concept for a SmallSat Exosphere Explorer of hot Jupiters (SEEJ; pronounced "siege"). SEEJ will monitor the X-ray emission of nearby X-ray bright stars with transiting hot Jupiters in order to measure the lowest density portion of exoplanet atmospheres and the coronae of the exoplanet hosts. SEEJ will use revolutionary Miniature X-ray Optics (MiXO) and CMOS X-ray detectors to obtain sufficient collecting area and high sensitivity in a low mass, small volume and low-cost package. SEEJ will observe scores of transits occurring on select systems to make detailed measurements of the transit depth and shape which can be compared to out-of-transit behavior of the target system. The depth and duration of the flux change will allow us to characterize the exospheres of multiple hot Jupiters in a single year. In addition, the long baselines (covering multiple stellar rotation periods) from the transit data will allow us to characterize the temperature, flux and flare rates of the exoplanet hosts at an unprecedented level. This, in turn, will provide valuable constraints for models of atmospheric loss. In this contribution we outline the science of SEEJ and focus on the enabling technologies Miniature X-ray Optics and CMOS X-ray detectors.

The Wide Field Imager (WFI), one of two complementary instruments on board ESA's next large X-ray mission Athena, combines state-of-the-art resolution spectroscopy with a large field of view and high count rate capability. Centerpiece of the WFI instrument are four DEPFET (Depleted p-channel field effect transistor) sensors with a size of 512_512 pixels each and one fast detector with a size of 64_64 pixels. They are planned to be operated in drain current readout mode, which enables fast readout rates but is sensitive to inhomogeneities of the drain currents. These inhomogeneities arise from the sheer size of the DEPFET sensor matrix and are originated in the spatial distribution of wafer properties and process parameters. We characterized the drain current distribution of a prototype device (64_64 pixels) utilizing the same layout and technology as specified for the pre-flight production of Athena's WFI DEPFET detectors. In order to better understand the origin of the current spread we measured I-V characteristics of all pixels and extracted threshold voltages and transconductance values of the detector in operational conditions. This is enabled by features of the VERITAS read-out ASIC.

The High Definition X-ray Imager (HDXI) is one of three planned instruments for the next generation Lynx mission concept and would provide fine spatial resolution X-ray imaging and moderate spectral resolution over a wide field-of-view. The instrument is baselined to rapidly read out large silicon focal plane arrays consisting of small pixels. We present the most recent results from small-pixel X-ray hybrid CMOS detectors that are designed to meet these needs. These devices implement crosstalk-eliminating capacitive transimpedance amplifiers as well the ability to perform in-pixel correlated double sampling, and have achieved noise and spectral resolution approaching the notional requirements of Lynx-HDXI. Read noise as low as 5.4 e- (RMS) has been measured, along with energy resolution (FWHM) as good as 158 eV at 5.9 keV, 78 eV at 0.52 keV, and 71 eV at 0.28 keV.

The SIRI line of instruments is designed to space-qualify new space-based, gamma-ray detector technology for Department of Defense (DoD) and astrophysics applications. SIRI-2’s primary objective is to demonstrate the performance of europium-doped strontium iodide (SrI₂:Eu) gamma-ray detection technology with sufficient active area for DoD operational needs. Secondary scientific objectives include understanding the internal background of SrI₂:Eu in the space radiation environment, and studying transient phenomena, such as solar flares. The primary detector array of the SIRI instrument consists of seven hexagonal europium-doped strontium iodide (SrI₂:Eu) scintillation detectors 3.81 cm by 3.81 cm, with a combined active area of 66 cm². SIRI-2’s primary detectors have an energy resolution of ~4% at 662 keV. SIRI-2 is expected to operate in the high gamma-ray background of a geosynchronous orbit and the instrument includes a number of features to both passively and actively suppress the unique background of the outer Van Allen belts. Construction and environmental testing of the SIRI-2 instrument has been completed, and it is currently awaiting integration onto the spacecraft bus. The expected launch date is Aug 2020 onboard the Space Test Program’s STPSat-6.

Lynx is a powerful, next-generation X-ray observatory that will provide orders of magnitude increases in capability relative to previous and other planned X-ray missions. Its unprecedented views of the X-ray universe will provide essential insights into the fundamental role played by high-energy processes in virtually every aspect of astrophysics, insights available from none of the other highly ambitious space- and ground-based observatories planned for the 2030s and beyond. Lynx is a flagship mission operating as a general observatory with almost all science observations carried out via a competed and peer-reviewed General Observer (GO) program. The Lynx architecture has been designed to enable highly challenging observations in each of three broad science pillars: detecting and understanding the seeds of the first supermassive black holes, characterizing physics of the energetic processes that drive galaxy formation and evolution, and probing the broad range of high-energy processes that shape stellar birth and death, internal stellar structure, star-planet interactions, and the origin of elements.

We have been studying Lynx, an X-ray Observatory with factors of 10 to 1000 greater imaging and spectroscopic capabilities than any other existing or planned facility. We present a Design Reference Mission (DRM) driven by the need to solve fundamental problems in three broad areas of astrophysics. The Lynx Observatory will provide discovery space for all of astrophysics, and also address questions which will only be revealed as our knowledge increases. Studies supported by the Advanced Concepts Office at MSFC for the observatory design and operations take advantage of the highly successful architecture of the Chandra Observatory. A light-weight mirror with 30 times the Chandra effective area, and modern microcalorimeter and CMOS based X-ray imagers will exploit the 0.5 arcsec imaging capability. Operating at Sun/Earth L2, we expect 85% to 90% of the time to be spent acquiring data from celestial targets. Designed for a five year baseline mission, there are no expected impediments to achieving a 20 year goal. This paper presents technical details of the Observatory and highlights of the mission operations.

Incom, Inc. is now producing commercially available Large Area Picosecond Photo-Detectors (LAPPD™) usable in applications by early adopters. The first generation LAPPD™ is an all-glass 230 x 220 x 22 mm³ flat panel photodetector with a chevron stack of glass capillary array microchannel plates functionalized by atomic layer deposition, a semitransparent bi-alkali photocathode, and a strip-line anode. The photodetector is being optimized for applications requiring picosecond timing and millimeter spatial resolution and has achieved single photoelectron (PE) timing resolutions of α≤52 ps. Typical performance metrics include electron gains of 10⁷ at 1 kV per MCP, low dark noise rates (15-30 Hz/cm² at moderate gains), single PE spatial response along and across strips of 1.8 mm and 0.76 mm respectively and quantum efficiencies that are typically ≥20% at 365 nm. Changes to the “baseline” LAPPD™ are under development to optimize the photodetector for applications requiring very high spatial resolutions.

Incom Inc. is developing and commercializing a novel type of microchannel plate (MCP) electron multipliers. These new devices are called “ALD-GCA-MCPs” and are made from glass capillary arrays (GCA), glass plates with a regular array of hollow glass capillaries that are functionalized using atomic layer deposition (ALD) thin film coating technology. ALD-GCA-MCPs are a technology advancement that affords MCPs with significantly improved performance, as compared to conventional MCPs. Notable benefits over conventional lead-oxide based MCPs are larger size, high and stable gain, low dark counts and gamma-ray sensitivity, improved mechanical stability, and the unique ability to tune the MCP resistance and electron amplification characteristics over a much wider range and independent from the glass substrate. Incom now routinely produces ALD-GCA-MCPs with 10 and 20 μm pore size at MCP dimensions up to 20 cm x 20 cm. The MCPs show a number of favorable characteristics, such as 3x lower gamma-ray sensitivity compared to conventional MPCs, low background (< 0.05 cts/s/cm²), and stable, high gains (<1×10⁴ for single MCP and <1×10⁷ for a chevron pair configuration, at 1000V/MCP). ALD-GCA-MCPs find use in a variety of photon counting applications and are particularly suited for charged particle detection that requires high timing and spatial resolution, such as Ion time-of-flight (TOF), electron spectroscopies, analytical and space instruments, and MCP-based photomultipliers such as the Large-Area Picosecond Photodetector (LAPPD^TM), which is also being developed by Incom Inc. In this paper, we provide a brief technology overview highlighting the current state of the art of Incom’s ALD-GCA-MCP technology, as well as current and future development efforts that address the GCA glass substrate as well as the resistive and electron emissive ALD coatings.

We present recent progress in the development of novel microchannel plates (MCPs) manufactured using standard lead glass and with borosilicate glass microcapillary arrays functionalized using Atomic Layer Deposition (ALD) technology. Standard glass MCPs have achieved high quantum efficiency (~60% @115 nm & 65 nm) using opaque alkali halide photocathodes. Enhanced performance standard glass MCPs have also been demonstrated with no fixed pattern noise due to construction defects. Novel borosilicate glass atomic layer deposited MCPs up to 20 cm format show good overall response uniformity, tight pulse height distributions and very low background levels (0.05 events cm^-2). Spatial resolutions of the order of 20 μm are demonstrated with 10 μm pore atomic layer deposited MCPs, and their fixed pattern noise has been significantly reduced. Bialkali cathodes in sealed tubes show high (<30%) efficiency at ~200 nm and long wavelength cutoffs at ~360 nm have been engineered.

We present the performance of a 200mm × 200mm microchannel plate detector during two suborbital flights in 2017 and 2018. The detector utilized ALD boro-silicate plates and a cross delay line readout. Background counts inflight were between 1.43 count/cm²/s. The quantum efficiency after two years and two flights was consistent with preflight measurements.

We report on life testing of conventional microchannel plates (MCPs) and atomic layer deposition (ALD) MCPs. For the Global-scale Observations of the Limb and Disk (GOLD) mission, long-duration, deep charge extraction testing was performed on a Z-stack triplet of 12 μm pore conventional MCPs with a CsI photocathode on the top surface. A relatively low gain (≈1000e-), modest charge extraction (0.07 C/cm²) full-field conditioning burn-in was performed followed by a very deep narrow line burn-in to emulate a GOLD spectral line. The gain local to the line burn-in decreased by ≈20% over ≈1 C/cm² of extracted charge, and then remained stable (to 95 C/cm²). We also present the performance of several sets of 20 μm pore ALD MCPs with MgO secondary electron emission layers through full-field conditioning burn-ins at both full gain and low gain.

The JUICE (JUpiter ICy moons Explorer) Ultraviolet Spectrograph (JUICE-UVS) is the fifth in the line of Alice/UVS spectrographs from Southwest Research Institute (SwRI). The heart of the instrument is a far-UV sensitive microchannel plate detector system. This detector includes an atomic-layer deposition (ALD) coating on the bottom plate to minimize gain sag, resulting in a detector with orders of magnitude longer lifetime given comparable fluences than previously flown MCP detectors. This detector is also the first instance of a curved microchannel plate z-stack receiving an ALD coating to minimize gain sag. The detector electronics have also been improved over previous generations to preserve pulse height integrity at the high (i.e. 100 kHz) count rates expected during operation in the Jupiter system. The flight model detector was bench tested at Sensor Sciences and delivered to the JUICE-UVS project in August 2018. Further bench tests were undertaken at SwRI after delivery, followed by thermal vacuum testing in October 2018. The results of these tests are presented herein.

In this paper we describe the design, science objectives, and preliminary results of the Dual-channel Extreme Ultraviolet Continuum Experiment (DEUCE). DEUCE is a dual-channel, sounding-rocket borne spectrograph consisting of a Wolter-II telescope and the largest MCP detector ever own in space. The DEUCE science objective is to obtain the first 700-1150 A spectra of highly ionizing hot stars in order to calibrate stellar models and better understand the role of such stars in ionization upkeep. DEUCE launched in December 2018 and obtained a quality spectrum of B star Epsilon Canis Majoris, which is preliminarily presented and discussed.

The SPRITE cubesat is a recently selected NASA astrophysics mission designed to measure ionizing radiation escape from star-forming galaxies, and to map far-ultraviolet (1000 - 1750 Å) emission from shocked regions in supernova remnants. The instrument leverages a number of new technologies identified for future large mission concepts, including the LUVOIR surveyor, to achieve the required performance. These include high broadband reflectivity mirror coatings and an ultra-low background photon counting microchannel plate detector with an anti-coincidence particle rejection system. SPRITE will serve as a flight testbed for these technologies, employing a robust calibration program as part of the principal science mission to advance the technology readiness level (TRL) to 7+ and provide heritage for future Explorer-class and larger missions. SPRITE is a 6U class cubesat funded through NASA ROSES with an anticipated launch date in 2022. The science data products will be archived on the Mikulski Archive for Space Telescopes (MAST). This proceedings describes the instrument science program, optical design, preliminary performance projections, and project timeline.

The Imaging X-ray Polarimetry Explorer (IXPE) will add polarization to the properties (time, energy, and position) observed in x-ray astronomy. A NASA Astrophysics Small Explorer (SMEX) in partnership with the Italian Space Agency (ASI), IXPE will measure the 2–8-keV polarization of a few dozen sources during the first 2 years following its 2021 launch. The IXPE Observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazingincidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU), separated by a deployable optical bench. The Observatory’s Spacecraft provides typical subsystems (mechanical, structural, thermal, power, electrical, telecommunications, etc.), an attitude determination and control subsystem for 3-axis stabilized pointing, and a command and data handling subsystem communicating with the science instrument and the Spacecraft subsystems.

Arcus provides high-resolution soft X-ray spectroscopy in the 12-50 Å bandpass with unprecedented sensitivity, including spectral resolution < 2500 and effective area < 250 cm². The three top science goals for Arcus are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, (2) to 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) to explore how stars form and evolve. Arcus uses the same 12 m focal length grazing-incidence Silicon Pore X-ray Optics (SPOs) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. 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. Combined with the high-heritage NGIS LEOStar-2 spacecraft and launched into 4:1 lunar resonant orbit, Arcus provides high sensitivity and high efficiency observing of a wide range of astrophysical sources.

HSP was selected for the NASA Astrophysics Science SmallSat Study (AS3) program as a SmallSat mission concept that will be proposed for a 1 – 2 year science mission to demonstrate performance and cost goals to enable a future Explorer-class SmallSat Constellation mission for the first simultaneous full-sky imager with 2X finer resolution. HSP is a 36 x 36deg (FWHM) coded aperture telescope with 16 x 16 CdZnTe detectors, each 20 x 20 x 3mm with 32 x 32 0.6mm pixels and ~1.5keV energy resolution. The 1024 cm^2 HSP imaging detector array views the sky through the Tungsten coded aperture mask (0.7 mm pixels) at 68cm, providing 4’ imaging and <30” source positions over the 3 – 200 keV band. This is mounted on a Blue Canyon Technologies (BCT) SmallSat (S5) bus, with ~10arcsec pointing and star camera aspect, extends the capabilities of Swift/BAT and INTEGRAL/IBIS. HSP will promptly localize long and short GRBs and outbursts of X-ray transients: from nearby M dwarf flares, to BH-LMXB outbursts, Blazar flares and Jetted TDEs.  HSP will daily-monitor the Galactic Bulge and adjacent Galactic plane and > 2 nearby OB association regions for 1 yr, providing high cadence light curves of black hole X-ray binaries (with low and high mass companions) in the Galaxy.  HSP matches the on-axis sensitivity of Swift/BAT in the 15 – 200 keV band with 5X finer spatial resolution, and the simultaneous 3 – 15 keV imaging and spectra surpass MAXI with 15X finer spatial resolution, all within an ESPA class mission in LEO at ~500-600 km and <~30 deg inclination.

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 1 keV. The WFI instrument employs DEPFET active pixel sensors, which are fully depleted, back-illuminated silicon devices of 450 μm thickness. These provide high quantum efficiency over the 0.2 keV to 15 keV range with state-of-the art spectral resolution and extremely fast readout speeds compared to previous generations of Si detectors for X-ray astronomy. The sensors are controlled and read out by customized ASICs developed for this project. The focal plane comprises a Large Detector Array (LDA) with over 1 million pixels of 130 μm × 130 μm size, providing oversampling of the PSF by a factor <2 over the large (40’ × 40’) field of view, complemented by a smaller Fast Detector (FD) optimized for high count rate applications. The WFI development has entered phase B of the project at the end of 2018 after a successful Preliminary Requirements Review of the instrument conducted jointly by ESA and DLR. A further important milestone was the endorsement of the both instrument consortia by ESA, also end of 2018. The results of breadboard model development and testing will be presented as well as the preliminary design of WFI and an outlook to the next steps of the development.

The world's premier X-ray astronomical observatories, Chandra and XMM-Newton, have been operating for about 20 years. The next flagship X-ray observatory launched will be ESA's Athena mission. We discuss planned US contributions to the Athena Wide Field Imager instrument, which encompass transient source detection, background characterization and reduction, and detector electronics design and testing, in addition to scientific contributions.

Axion is a promising dark matter candidate as well as a solution to the strong charge-parity (CP) problem in quantum chromodynamics (QCD). We describe a new concept for SmallSat Solar Axion and Activity X-ray Telescope (SSAXI) to search for solar axions or axion-like particles (ALPs) and to monitor solar activity over a wide dynamic range. SSAXI aims to unambiguously identify X-rays converted from axions in the solar magnetic field along the line of sight to the solar core, effectively imaging the solar core. SSAXI employs Miniature lightweight Wolter-I focusing X-ray optics (MiXO) and monolithic CMOS X-ray sensors in a compact package. The wide energy range (0.5 - 5 keV) of SSAXI can easily distinguish spectra of axion-converted X-rays from solar X-ray spectra, while encompassing the prime energy band (3 - 4.5 keV) of axion-converted X-rays. The high angular resolution (30 arcsec) and large field of view (40 arcmin) in SSAXI will easily resolve the enhanced X-ray flux over the 3 arcmin wide solar core while fully covering the X-ray activity over the entire solar disc. The fast readout in the inherently radiation tolerant CMOS X-ray sensors enables high resolution spectroscopy over a wide dynamic range with a broad range of operational temperatures. We present multiple mission implementation options for SSAXI under ESPA class. SSAXI will operate in a Sun-synchronous orbit for 1 yr preferably near a solar minimum to accumulate sufficient X-ray photon statistics.

We present the performance and recent results of the MIT polarimetry beamline. Originally designed for testing Chandra HETG gratings, the beamline has been adapted to test components for soft x-ray polarimetry applications. Since then, its monochromator capabilities have also been used to test gratings. We present results on the measured absolute efficiencies of the Arcus Phase A gratings using the B-K, O-K, and C-K emission lines. The beamline has also been used to develop tools and techniques to measure the linear polarization of soft X-rays (0.2-0.8 keV), which form the basis for a sounding rocket mission REDSoX (Rocket Experiment Demonstration of a Soft X-ray Polarimeter) and a possible orbital mission. We present our tests to align the REDSoX gratings, as well as our idea to use thin twisted crystals as a possible alternative to laterally-graded multilayer mirrors. Support for this work was provided in part by the NASA grant NNX15AL14G and a grant from the MIT Kavli Institute.

The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket experiment demonstrates the technique of focusing hard X-ray (HXR) optics for the study of fundamental questions about the high-energy Sun. Solar HXRs provide one of the most direct diagnostics of accelerated electrons and the impulsive heating of the solar corona. Previous solar missions have been limited in sensitivity and dynamic range by the use of indirect imaging, but technological advances now make direct focusing accessible in the HXR regime, and the FOXSI rocket experiment optimizes HXR focusing telescopes for the unique scientific requirements of the Sun. FOXSI has completed three successful flights between 2012 and 2018. This paper gives a brief overview of the experiment, focusing on the third flight of the instrument on 2018 Sept. 7. We present the telescope upgrades highlighting our work to understand and reduce the effects of singly reflected X-rays and show early science results obtained during FOXSI's third flight.

We present on the detector characterization activities and flight results for fine-pitch (60um) cadmium telluride (CdTe) strip detectors designed for the Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket experiment. FOXSI, optimized for observations in the range 4-20 keV, is the first solar-dedicated instrument to utilize the technology of focusing optics for observing the Sun in hard X-rays. Each of the seven FOXSI optics modules is paired with a semiconductor strip detector from which the energy and position of each incoming photon can be derived. While the first FOXSI experiment (FOXSI-1) flew only silicon (Si) detectors, both of the next two FOXSI sounding rocket experiments (FOXSI-2 and FOXSI-3) upgraded some of the detectors to CdTe (60um pitch) for enhanced efficiency at energies >10 keV. Here we present the measurements and analysis performed to characterize components of the CdTe detector response for FOXSI-2 and FOXSI-3, including the gain, energy resolution, and efficiency. Additionally, we explore the effects of charge sharing for these fine-pitch detectors and describe how these effects are accounted for in our calibration and data analysis. Results from spectral analysis of a solar microflare using CdTe data from the FOXSI-2 flight will be shown.

In this talk, I will describe briefly the telescope, instrument, and flight of the Faint Intergalactic medium Redshifted Emission Balloon (FIREBall-2). FIREBall-2 is a UV multi-object spectrograph fed by a 1 meter parabola mirror. The instrument was designed to observe 4 pre-selected fields and uses a UV optimized delta-doped EMCCD. The telescope flew on September 22, 2018 from Fort Sumner, NM, as part of the fall CSBF balloon campaign. The telescope collected data for several night hours before being cut down. I will describe the testing, flight, and hardware performance with an emphasis on the in flight performance of the instrument, including resolution, throughput, and the overall operation of the UV optimized EMCCD. Additional talks will be presented on other aspects of the flight and data.

The Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall-2, FB-2) is designed to discover and map faint UV emission from the circumgalactic medium around low redshift galaxies (z ~ 0.3 (C IV); z ~ 0.7 (Lyα); z ~ 1.0 (O VI)). FIREBall-2's first launch, on September 22nd 2018 out of Ft. Sumner, NM, was abruptly cut short due to a hole that developed in the balloon. FIREBall-2 was unable to observe above its minimum require altitude (25 km; nominal: 32 km) for its shortest required time (2 hours; nominal: 8+ hours). The shape of the deflated balloon, as well as a concurrent full moon close to our observed target field, revealed a severe, off-axis scattered light path directly to the UV science detector. Additional damage to FB-2 added complications to the ongoing effort to prepare FB-2 for a quick re-flight. Upon landing, several mirrors in the optical chain, including the two large telescope mirrors, were damaged, resulting in chunks of material broken off the sides and reflecting surfaces. The magnifying optical element, called the focal corrector, was discovered to be misaligned beyond tolerance after the 2018 flight, with one of its two mirrors damaged from the landing impact. We describe the steps taken thus far to mitigate the damage to the optics, as well as procedures and results from the ongoing efforts to re-align the focal corrector and spectrograph optics. We report the throughput of the spectrograph before and after the 2018 flight and plans for improving it. Finally, we describe several methods by which we address the scattered light issues seen from FIREBall-2's 2018 campaign and present the current status of FB-2 to fly during the summer campaign in Palestine, TX in 2020.

We have developed the capability to optimize a diffraction grating with arbitrary groove density and direction as a function of location. The added degrees of freedom allow additional correction of optical aberrations beyond what is available to holographic recordings. Since the groove direction and density can be independent but continuous for all points on the grating, we are not constrained by the limitations of ensuring that the grooves follow a single parametrized function. By fabricating a grating with an e-beam in silicon, we are able to produce a coherent, continuous grating across a silicon substrate. Silicon substrates have a number of advantages for optical designers, with ready availability. Additional advances in fabrication are providing improved grating efficiency. The key advance we report here is the adaptation of existing semiconductor fabrication technology to create a grating with grooves that are functionally independent across the entire grating. By ensuring that the grooves are continuous and coherent, we are able to fabricate a grating with unprecedented optical performance at low cost. Work to date includes fabricated test pieces, testing of the pieces, and refinement of the modeling of the optical performance.

The JUICE (Jupiter ICy moons Explorer) and Europa Ultraviolet Spectrographs (JUICE-UVS and Europa-UVS, respectively) are nearly identical modest-powered (~9W) instruments scheduled to explore the Jovian satellites aboard ESA’s JUICE and NASA’s Europa Clipper missions, respectively. These spectrographs each feature a dedicated door containing a high-resolution aperture stop that reduces the focal ratio of the telescope from f/3 to f/12. The baseline design for this aperture was a 1-cm diameter circle. We compared the optical properties of the baseline 1-cm diameter aperture with a 1-cm by 1-cm square aperture in an effort to increase throughput by 27% while maintaining the native spatial resolution of the spectrograph. The effects of both apertures were analyzed with no appreciable difference in the resulting spatial or spectral resolution. Therefore, the 1-cm by 1-cm square aperture has been implemented in both JUICE- and Europa-UVS.

X-Ray telescopes with optics and detectors at opposite ends of semi-rigid, extendable booms can improve their imaging performance if the flexing of the boom is measured and removed in image reconstruction. This has been accomplished on previous missions with analog position detectors and highly stable laser pointing indicators. This report shows that a flight-proven digital imaging system observing LED sources, can achieve as high or higher precision measurements without extensive calibration at modest cost.

Lynx is one of the Surveyor-class mission concept studies for the 2020 Astrophysics Decadal Survey. One of the nominal science instruments for Lynx is a soft X-ray grating spectrometer and our design using critical-angle transmission (CAT) gratings can achieve the required resolving power R < 5000 and effective area < 4000 cm². We presented an initial optical design in Günther and Heilmann 2019 (JATIS 5, 02), and identified several points where additional ray-trace work can improve our design of the instrument. We add additional non-ideal effects to our ray-traces, namely diffraction and shadowing by the support structures of the gratings membranes and a finite energy resolution of the detector. Taken together, resolving power and effective area do not change much compared to our initial work, but this higher level of detail in the simulations shows that the design is workable in the presence of non-ideal effects.

The thermal dependence of the semiconductor detector is one of the critical properties. This manuscript describes changes in the threshold scans, equalization and its verification for the particle counting pixel detector Timepix. The Timepix detector family has great potential for use not only in space, i.e. for small satellite (CubeSat) missions, but also in many other areas like medicine, material testing or particle colliders (i.e. Large Hadron Collider). In this case, several experiments were performed with the Timepix detector under the vacuum conditions as well as ambient conditions with the thermal stabilization at several temperatures in a range from -15^oC to +80^oC. This paper describes the early experimental results of the chip temperature dependence. The detector equalization and validity of the original equalization dependently on different temperatures is examined. The changes in the detector could cause the errors and shifts of the detection limit for low-energies.

With the observation of the gravitational wave event of August 17th 2017 and then with those of the extragalactic neutrino of September 22nd, the multi messenger astronomy era has definitely begun. With the opening of this new panorama, it is necessary to have a perfect coordination of the several observatories. Crystal Eye is an experiment aimed at the exploration of the electromagnetic counterpart of the gravitational wave events, that represent the missing observational link between short Υ-ray bursts and gravitational waves from neutron star mergers. The experiment we propose is a wide field of view observatory. The Crystal Eye objectives will be: to alert the community about events containing soft X-ray and low energy Υ-ray, to monitor long-term variabilities of X-ray sources, to stimulate multi-wavelength observations of variable objects, and to observe diffuse cosmic soft X-ray emissions.

This paper analyzes a recently published model for Lynx Mirror Assembly production duration, to understand the sensitivity of duration to various factors. The factors considered are finite process yield, knowledge of the individual process times and finite server reliability. In all of these cases, closed form estimates are given along with numerical examples. This initial analysis indicates that accurate and precise knowledge of the process times is fundamental to making an accurate prediction of schedule duration. Analysis of the failure of any given server is also explained and can be used as the basis of a rational sparing policy.

The main characteristics of Solar-C_EUVST are the high temporal and high spatial resolutions over a wide temperature coverage. In order to realize the instrument for meeting these scientific requirements under size constraints given by the JAXA Epsilon vehicle, we examined four-dimensional optical parameter space of possible solutions of geometrical optical parameters such as mirror diameter, focal length, grating magnification, and so on. As a result, we have identified the solution space that meets the EUVST science objectives and rocket envelope requirements. A single solution was selected and used to define the initial optical parameters for the concept study of the baseline architecture for defining the mission concept. For this solution, we optimized the grating and geometrical parameters by ray tracing of the Zemax software. Consequently, we found an optics system that fulfills the requirement for a 0.4” angular resolution over a field of view of 100" (including margins) covering spectral ranges of 170-215, 463-542, 557-637, 690-850, 925-1085, and 1115-1275 A. This design achieves an effective area 10 times larger than the Extreme-ultraviolet Imaging Spectrometer onboard the Hinode satellite, and will provide seamless observations of 4.2-7.2 log(K) plasmas for the first time. Tolerance analyses were performed based on the optical design, and the moving range and step resolution of focus mechanisms were identified. In the presentation, we describe the derivation of the solution space, optimization of the optical parameters, and show the results of ray tracing and tolerance analyses.

The Solar-C_EUVST is a mission designed to provide high-quality solar spectroscopic data covering a wide temperature range of the chromosphere to flaring corona. To fulfill a high throughput requirement, the instrument consists of only two optical components; a 28-cm primary mirror and a segmented toroidal grating which have high reflective coatings in EUV-UV range. We present a mission payload structural design which accommodates long focal length optical components and a launcher condition/launch environment (JAXA Epsilon). We also present a mechanical design of primary mirror assembly which enables slit-scan observations, an image stabilizing tip-tilt control, and a focus adjustment on orbit, together with an optomechanical design of the primary mirror and its supporting system which gives optically tolerant wavefront error against a large temperature increase due to an absorption of visible and IR lights.

The Lynx x-ray mission will push thin film filters to larger apertures and thinner profiles than those of any preceding mission. We present a study of the uniformity of deposition with existing technology and the consequences of oxidation on 10-15 nm thick Al films on LUXFilm® polyimide. From visible and infrared transmission measurements of thin aluminum filters and the results of a photon-driven oxidation study at the Beamline 1 of the Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology, we conclude that, from a deposition and oxidation standpoint, Al optical blocking layers at this thickness are viable.