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This paper presents Rocket Experiment (REX) that was part of a dual payload rocket campaign for NASA's sounding rocket Black Brant IX with water recovery technology. This mission was a suborbital sounding rocket flight that was launched and recovered on April 4, 2018 and targeted the Vela supernova remnant. The purpose of REX was to classify the Technology Readiness Level of onboard devices designed for space applications. The devices were two wide-field X-ray telescopes consisting of a combination of Lobster-Eye (LE) optics with an uncooled Timepix detector (256 x 256 px @ 55 um), and additional sensors. The first telescope uses a two-dimensional combination of LE modules with a focal length of 1 m and a Field of View (FOV) of 1.0 x 1.2 deg and operates in the energy range of 3 - 60 keV. The second telescope was a one-dimensional LE with a focal length of 250 mm and a FOV of 2.7 x 8.0 deg for the energy range 3 - 40 keV. The X-ray telescopes were supplemented by a camera in the visible spectrum with 1,280 x 1,024 px resolution, which was used to obtain images of the observed sources and to verify the resulting pointing of the rocket carrier. Other devices also include infrared array sensors and inertial measurement units tested for future small satellite missions. The data handler and communication system were built using the Robot Operating System, and both the system and the electronics were deployed and operated in flight. The hardware was successfully recovered after the launch and the data were extracted., Comment: Submitted to Acta Astronautica

Photon counting detector systems on sounding rocket payloads often require interfacing asynchronous outputs with a synchronously clocked telemetry (TM) stream. Though this can be handled with an on-board computer, there are several low cost alternatives including custom hardware, microcontrollers and field-programmable gate arrays (FPGAs). This paper outlines how a TM interface (TMIF) for detectors on a sounding rocket with asynchronous parallel digital output can be implemented using low cost FPGAs and minimal custom hardware. Low power consumption and high speed FPGAs are available as commercial off-the-shelf (COTS) products and can be used to develop the main component of the TMIF. Then, only a small amount of additional hardware is required for signal buffering and level translating. This paper also discusses how this system can be tested with a simulated TM chain in the small laboratory setting using FPGAs and COTS specialized data acquisition products., 16 pages, 11 pages (also published as a 2015 SPIE conference proceeding)

The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a funded series of sounding rocket instruments to detect diffuse soft X-ray emission from astrophysical sources. The first launch of tREXS is scheduled for Q4 2021, with a goal to observe the Cygnus Loop supernova remnant. tREXS house a four-channel grating spectrometer that uses passive, mechanical focusers, arrays of reflection gratings, and an extended focal plane based around Teledyne CIS 113 CMOS sensors. We present here an update on the instrument design, build, and calibrations in advance of the launch later this year.

Modern grating manufacturing techniques suffer from inherent issues that limit their peak efficiencies. We describe work in collaboration with the Nanofabrication Lab at Penn State University to design and characterize etched silicon gratings optimized for the extreme (EUV; 10 { 90 nm) and far ultraviolet (FUV; 90 { 180 nm) bandpasses. We develop this technology by fabricating a variety of gratings that operate over these bandpasses. We present analyses for two different grating designs in this work. The first is an FUV echelle that has similar parameters to the grating own on the CHESS sounding rocket. CHESS was an FUV spectrograph that utilized a mechanically ruled echelle grating. We compare the efficiency and in-instrument performance of the gratings, finding a ~ 50% increase in groove efficiency and an 80% decrease in inter-order scatter for the etched gratings compared to their mechanically ruled counterpart. The FUV echelle improvements can ultimately benefit the faint source sensitivity and high-resolution performance of future UV observatories, such as LUVOIR, by reducing the non-uniform inter-order backgrounds that have historically plagued echelle spectrographs. We additionally provide a description of how this lithographic process can be extended to gratings with holographic solutions by discussing our procedure for generating a map of groove traces from holographic recording parameters. This discussion is provided in the context of the creation of a grating sample that was developed in support of the ESCAPE Small Explorer Phase A study.

The Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS) has been successful in maturing technologies for carrying out multi-object spectroscopy in the far-UV, including: the successful implementation of the Next Generation of Microshutter Arrays; large-area microchannel plate detectors; and an aspheric "dual-order" holographically ruled diffraction grating with curved, variably-spaced grooves with a laminar (rectangular) profile. These optical elements were used to construct an efficient and minimalist "two-bounce" spectro-telescope in a Gregorian configuration. However, the susceptibility to Lyman alpha (Ly$\alpha$) scatter inherent to the dual order design has been found to be intractably problematic, motivating our move to an "Off-Axis" design. OAxFORTIS will mitigate its susceptibility to Ly$\alpha$ by enclosing the optical path, so the detector only receives light from the grating. The new design reduces the collecting area by a factor of 2, but the overall effective area can be regained and improved through the use of new high efficiency reflective coatings, and with the use of a blazed diffraction grating. This latter key technology has been enabled by recent advancements in creating very high efficiency blazed gratings with impressive smoothness using electron beam lithography and chemical etching to create grooves in crystalline silicon. Here we discuss the derivation for the OAxFORTIS grating solution as well as methods used to transform the FORTIS holographic grating recording parameters (following the formalism of Noda et al.1974a,b), into curved and variably-spaced rulings required to drive the electron beam lithography write-head in three dimensions. We will also discuss the process for selecting silicon wafers with the proper orientation of the crystalline planes and give an update on our fabrication preparations., Comment: 10 pages, 6 figures, to appear in Proc. of SPIE Vol. 11821, UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XXII

The Off-plane Grating Rocket Experiment is a soft X-ray grating spectrometer payload to be launched on a suborbital rocket. The spectrometer will use three technologies – monocrystalline silicon X-ray optics (NASA Goddard Space Flight Center), X-ray reflection gratings (The Pennsylvania State University), and electron-multiplying CCDs (XCAM Ltd., The Open University) – to achieve the highest performance on-sky soft X-ray spectrum to date when launched. To realize this performance, not only must each of the three individual spectrometer components perform at their required level, but these components also must be aligned to one another to the required tolerances and integrated into the payload. In this manuscript, we report on the alignment and integration plan for each component within the spectrometer.

The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of NASA funded suborbital rockets that will make large field-of-view observations of the diffuse soft X-ray emission from the Cygnus Loop and Vela supernova remnants. The tREXS focal plane camera is made up of an array of 11 Vega-CIS113 CMOS detectors, with a 12th as the zero-order detector. To optimize the performance of the camera, a test setup was developed where a single CMOS detector can be characterized to determine which settings have the highest impact on detector performance characteristics such as readout noise. This paper will discuss this test setup, the initial testing that has occurred using an engineering grade detector, and the initial results on how changing bias potentials and pixel timings impact the readout noise. Improvements that will be made to the final focal plane camera electronics based on the findings in the initial testing will also be discussed.

The Rocket for Extended-Source X-ray Spectroscopy (tREXS) is a suborbital rocket payload that is designed to obtain the most highly resolved soft X-ray emission spectrum from the Cygnus Loop to date. This research will discuss the development and implementation of a guidance system that will replace the traditional pointing mechanism for a sub-orbital payload. Normally the pointing requirement for a sub-orbital flight is achieved using a NSROC altitude control system, which uses an ST5000 star tracker co-aligned with the X-ray optic. In tREXS design there is not space to use this star tracker; therefore, a design has been made that utilizes a side looking ST5000 to acquire the target field and an aspect camera for fine pointing. The aspect camera will stream frames of the target star field, that will be processed by the guidance algorithm. The algorithm will relay where to position the payload to target the Cygnus Loop.

We present a new, inexpensive, bench-top method for measuring groove period over large areas with high mapping resolution and high measurement accuracy, dubbed the grating mapper for accurate period (GMAP). The GMAP has the ability to measure large groove period changes and non-parallel grooves, both of which cannot be measured via optical interferometry. In this paper, we detail the calibration and setup of the GMAP, and employ the instrument to measure three distinct gratings. Two of these measured gratings have customized groove patterns that prevent them from being measured via other traditional methods, such as optical interferometry. Our implementation of this tool achieves a spatial resolution of 0.1 mm$\times$0.1 mm and a period error of 1.7 nm for a 3 $\mu$m size groove period., Comment: 14 pages, 16 figures

Ultraviolet spectroscopy for astrophysics allows us to address key scientific goals ranging from exoplanets and their environments to stars of all types and ages to galaxies and their evolution. In order to achieve these goals, spectrographs must realize improvements in sensitivity and resolving power. Recent advancements in reflection gratings for X-ray astronomy have enabled concurrent increases in these performance requirements. The nanofabrication-based techniques are now being applied to UV gratings with electron beam lithography (EBL) lying at the heart of the processing steps. EBL allows for custom groove distributions on flat and curved substrates thus opening new parameter space for spectrograph optimization. Blazed profiles are also realizable using EBL itself or subsequent processing steps. We report here the early results of fabrication work and performance testing on UV gratings intended for use on a variety of platforms from upcoming suborbital rockets, to Explorer and Flagship concept missions.

The Off-plane Grating Rocket Experiment (OGRE) is a soft x-ray grating spectrometer to be flown on a suborbital rocket. The payload is designed to obtain the highest-resolution soft x-ray spectrum of Capella to date with a resolution goal of R ( λ / Δλ ) > 2000 at select wavelengths in its 10 to 55 Å bandpass of interest. The optical design of the spectrometer realizes a theoretical maximum resolution of R ≈ 5000, but this performance does not consider the finite performance of the individual spectrometer components, misalignments between components, and in-flight pointing errors. These errors all degrade the performance of the spectrometer from its theoretical maximum. A comprehensive line-spread function (LSF) error budget has been constructed for the OGRE spectrometer to identify contributions to the LSF, to determine how each of these affects the LSF, and to inform performance requirements and alignment tolerances for the spectrometer. In this document, the comprehensive LSF error budget for the OGRE spectrometer is presented, the resulting errors are validated via raytrace simulations, the implications of these results are discussed, and future work is identified.

The Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission is an astrophysics Small Explorer employing ultraviolet spectroscopy (EUV: 80 – 825 A and FUV: 1280 – 1650 A) 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 soft X-ray grating spectrometer on board the Off-plane Grating Rocket Experiment (OGRE) hopes to achieve the highest resolution soft X-ray spectrum of an astrophysical object when it is launched via suborbital rocket. Paramount to the success of the spectrometer are the performance of the [Formula: see text] reflection gratings populating its reflection grating assembly. To test current grating fabrication capabilities, a grating prototype for the payload was fabricated via electron-beam lithography at The Pennsylvania State University’s Materials Research Institute and was subsequently tested for performance at Max Planck Institute for Extraterrestrial Physics’ PANTER X-ray Test Facility. Bayesian modeling of the resulting data via Markov chain Monte Carlo (MCMC) sampling indicated that the grating achieved the OGRE single-grating resolution requirement of [Formula: see text] at the 94% confidence level. The resulting [Formula: see text] posterior probability distribution suggests that this confidence level is likely a conservative estimate though, since only a finite [Formula: see text] parameter space was sampled and the model could not constrain the upper bound of [Formula: see text] to less than infinity. Raytrace simulations of the tested system found that the observed data can be reproduced with a grating performing at [Formula: see text]. It is therefore postulated that the behavior of the obtained [Formula: see text] posterior probability distribution can be explained by a finite measurement limit of the system and not a finite limit on [Formula: see text]. Implications of these results and improvements to the test setup are discussed.

We have fabricated a blazed x-ray reflection grating with a period of 160 nm using thermally activated selective topography equilibration (TASTE) and electron-beam (ebeam) physical vapor evaporation. TASTE makes use of grayscale ebeam lithography to create three-dimensional (3-D) structures in resist, which can then be thermally reflown into a desired profile. A blazed grating profile can be fabricated by selectively reflowing a periodic staircase structure into a wedge. This was done for the first time at a grating period of 160 nm, 2.5 times smaller than previous x-ray gratings fabricated using TASTE. The grating was patterned over a 10 mm by 60 mm area in a 147-nm-thick layer of poly(methyl methacrylate) resist and coated with 5 nm of chromium and 15 nm of gold using ebeam evaporation. The diffraction efficiency of the grating was measured using beamline 6.3.2 at Lawrence Berkeley National Laboratory’s Advanced Light Source. The results show a total absolute diffraction efficiency ≳40 % at lower energies, with maximum single-order diffraction efficiency ranging from 20% to 40%. The total diffraction efficiency was ≳30 % across the measured bandpass of 180 to 1300 eV.

Gratings enable dispersive spectroscopy from the X-ray to the optical, and feature prominently in proposed flagships and SmallSats alike. The exacting performance requirements of these future missions necessitate assessing whether the present state-of-the-art in grating manufacture will limit spectrometer performance. In this work, we manufacture a 1.5 mm thick, 1000 nm period at grating using electron-beam lithography (EBL), a promising lithographic technique for patterning gratings for future astronomical observatories. We assess the limiting spectral resolution of this grating by interferometrically measuring the diffracted wavefronts produced in +/-1st order. Our measurements show this grating has a performance of at least R ~ 14,600, and that our assessment is bounded by the error of our interferometric measurement. The impact of EBL stitching error on grating performance is quantifed, and a path to measuring the period error of customized, curved gratings is presented.

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 cm^2. 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.

Future astronomical X-ray spectrometer missions call for high spectral resolution in conjunction with high throughput. To achieve both of these requirements simultaneously, many grating elements must be aligned such that their diffraction arcs overlap at the focal plane. Methods for the alignment of reflection gratings operated in the extreme off-plane mount are being developed at The Pennsylvania State University in support of the Off-plane Grating Rocket Experiment. We report on the alignment methodology and performance tests of an aligned reflection grating module.

We have fabricated a blazed X-ray reflection grating with a period of 160 nm using thermally activated selective topography equilibration (TASTE). The grating was tested for diffraction efficiency using the soft X-ray reflectometer at Lawrence Berkeley National Laboratory's Advanced Light Source. Preliminary results show total absolute diffraction efficiency ≥ 40% at lower energies, with maximum single order diffraction efficiency ranging from 20-40%. Total diffraction efficiency was ≥ 30% across the entire measured band pass of 180 eV to 1300 eV.

The Off-plane Grating Rocket Experiment (OGRE) is a soft X-ray spectroscopy suborbital rocket payload designed to obtain the highest-resolution soft X-ray spectrum of Capella to date. With a spectral resolution goal of R(λ/uλ) < 2000 at select wavelengths in its 10-55 A bandpass of interest, the payload will be able to study the line-dominated spectrum of Capella in unprecedented detail. To achieve this performance goal, the payload will employ three key technologies: mono-crystalline silicon X-ray mirrors developed at NASA Goddard Space Flight Center, reflection gratings manufactured at The Pennsylvania State University, and electron-multiplying CCDs developed by The Open University and XCAM Ltd. In this document, an updated optical design that can achieve the performance goal of the OGRE spectrometer and a new grating alignment concept to realize this optical design are described.

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.

High-resolution, high-throughput soft X-ray spectroscopy using reflection gratings has the potential to unlock answers to many of the questions about the high-energy Universe. To enable missions to use this technology in the future, the ability to precisely align reflection gratings needs to be demonstrated. The Water Recovery X-ray Rocket (WRXR), a soft X-ray spectrometer that successfully launched in April 2018 from the Kwajalein Atoll, required co-aligned X-ray reflection gratings. WRXR was designed to produce a moderate-resolution spectrum of the Vela supernova remnant over a large field-of-view. The grating module was manufactured, integrated onto the rocket payload, passed environmental testing and was successfully launched and recovered. This paper describes the grating and mirror alignment methodologies for WRXR, and their inherent systematic uncertainties. Improvements to the alignment method that are required to meet the tighter alignment tolerances of future X-ray spectrometers are also discussed.

The Off-plane Grating Rocket Experiment (OGRE) is a sounding rocket payload designed to obtain a high-resolution soft X-ray spectrum of Capella. OGRE’s optical system uses new technologies including state-of-the-art X-ray optics, custom arrays of reflection gratings, and an array of EM-CCDs. Many of these technologies will be tested for the first time in flight with OGRE. To achieve the high performance that these new technologies are capable of, the payload components must be properly aligned to meet high tolerances. This paper will outline OGRE’s opto-mechanical design for achieving alignment within these tolerances. Specifically, the design of the X-ray grating arrays will be discussed.

Historically, ultraviolet (UV) gratings used in astronomical spectrographs have been made using two different techniques. Mechanically-ruled gratings have been produced for more than a hundred years. A diamond tool is used to create parallel grooves onto a fine metallic coating layer that has been previously deposited on a polished substrate. The edge-on profile of these grooves is a sawtooth tilted at a specific angle called the "blaze" angle. The blaze angle is the deciding factor that will allow for maximum efficiency at a specific wavelength called the "blaze" wavelength. Holographic gratings are produced using interference lithography. A layer of photoresist deposited on a substrate is exposed to fringes usually formed by exposure to two coherent laser beams. After development, the resulting pattern is sinusoidal by nature. Blazing one side of the sinusoidal profile of holographic gratings is possible through ion etching, but is only commonly used for a limited subset of grating parameters. Both types of gratings have different advantages: - Ruled gratings have a sharp, blazed profile that ensures good efficiency. However, they suffer from groove spacing inconsistencies that lead to stray light and ghosting. - Holographic gratings do not suffer from groove spacing errors which minimizes stray light. However, their sinusoidal profile (if not ion etched) leads to efficiency losses. At Penn State University, we are studying new processes that allow to fabricate blazed, high efficiency and high spectral resolution UV gratings for astronomical purposes. These processes are derived from the ones we used in creating X-ray gratings and consist of: 1) writing an electron-beam pattern consisting of parallel grooves on a layer of positive resist that has been deposited on a Si substrate. 2) dry etching this profile into a hard mask made of silicon nitride. 3) wet etching with KOH that will create the sawtooth profile at a specific blaze angle thanks to the properties of the different crystallographic planes of silicon. Gratings fabricated using these techniques show an excellent behavior all around, combining the best qualities from both ruled and holographic gratings. Indeed, they display a sharp sawtooth profile, they do not suffer from periodicity errors, and grating facets show low roughness. Recent testing done at UC Boulder shows efficiencies that are close to the maximum, theoretical limit. Combined with the possibility to create custom blaze angles through the use of custom cut Si wafers, this opens the way to new applications in the field of astronomical UV spectroscopy.

Astronomical X-ray diffraction gratings are a key technology under development for current and future NASA missions. X-ray reflection gratings, developed at Penn State University, have recently demonstrated both leading diffraction efficiency and high spectral resolving power. However, recent results are the result of different fabrication techniques and a single technique has not yet been developed to yield a grating that satisfies both the diffraction efficiency and resolving power required by future missions. Here we seek to leverage exiting electron-beam lithographic techniques to produce a grating with groove groove pattern capable of high resolving power. We then introduce new ion-milling techniques to create custom groove profiles capable of high diffraction efficiency. The goal is to produce a radial groove pattern with precisely blazed facets that are customizable based on ion mill input parameters. The process should be insensitive to groove density (ranging from ~150 nm to 400+ nm), facet size, and desired facet angle. Initial efforts in this study have concentrated on constraining various parameters in ion milling to fully characterize the effect of each parameter on the grating groove profile. We present here initial results and discuss experimental verification and future work.

Future observatories utilizing reflection grating spectrometers for extreme ultraviolet (EUV) and soft X-ray (SXR) spectroscopy require high-fidelity gratings with both blazed groove facets and custom groove layouts that are often fanned or feature a slight curvature. While fabrication procedures centering on wet anisotropic etching in monocrystalline silicon produce highly efficient blazed gratings, the precision of a nonparallel groove layout is limited by the cubic structure of the silicon crystal. This motivates the pursuit of alternative techniques to grating manufacture, namely thermally activated selective topography equilibration (TASTE), which uses gray-scale electron-beam lithography to pattern multilevel structures in resist followed by an optimized polymer thermal reflow to smooth the 3D patterns into continuous surface relief profiles. Using TASTE, a mold for a reflection grating with a periodicity of 400 nm and grooves resembling an asymmetric sawtooth was patterned in 130 nm thick poly(methyl methacrylate) resist on a silicon substrate over a 50 mm by 7.5 mm area. This structure was coated with 15 nm of gold by electron-beam physical vapor deposition using titanium as an adhesion layer and then tested for EUV and SXR diffraction efficiency at beamline 6.3.2 of the Advanced Light Source synchrotron facility. Results demonstrate a quasi-blaze response characteristic of a 27 degree blaze angle with groove facets smooth to 1.5 nm rms. Absolute peak-order efficiency ranges from 75% to 25%, while total relative efficiency measures gap90% across the measured bandpass of 15.5 nm > lambda > 1.55 nm., 19 pages, 16 figures

Many of the key science goals in X-ray astronomy require spectroscopy in the soft energy band, 0.2 - 2.0 keV. The performance requirements placed on spectrometers typically have spectral resolving powers in the thousands with effective areas in the hundreds of square centimeters. Obtaining both of these requirements in a single instrument is a challenge for a variety of reasons. Here, we discuss the development tasks specific to off-plane reflection gratings. We detail the requirements that drive our technical challenges such as fabrication, alignment, and integration. Finally, we summarize recent results of X-ray performance testing demonstrating very high diffraction efficiency and resolving power.

Arcus, a Medium Explorer (MIDEX) mission, was selected by NASA for a Phase A study in August 2017. The observatory provides high-resolution soft X-ray spectroscopy in the 12-50 A bandpass with unprecedented sensitivity: effective areas of >350 cm^2 and spectral resolution >2500 at the energies of O VII and O VIII for z=0-0.3. The Arcus key science goals are (1) to 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) 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, circumstellar disks and exoplanet atmospheres form and evolve. Arcus relies upon the same 12m focal length grazing-incidence silicon pore X-ray optics (SPO) 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. The power and telemetry requirements on the spacecraft are modest. Arcus will be launched into an ~ 7 day 4:1 lunar resonance orbit, resulting in high observing efficiency, low particle background and a favorable thermal environment. Mission operations are straightforward, as most observations will be long (~100 ksec), uninterrupted, and pre-planned. The baseline science mission will be completed in

The Off-plane Grating Rocket Experiment (OGRE) is a soft X-ray spectroscopy suborbital rocket payload scheduled for launch in Q3 2020 from Wallops Flight Facility. The payload will serve as a testbed for several key technologies which can help achieve the desired performance increases for the next generation of X-ray spectrographs and other space-based missions: monocrystalline silicon X-ray mirrors developed at NASA Goddard Space Flight Center, reflection gratings manufactured at The Pennsylvania State University, and electron-multiplying CCDs developed by the Open University and XCAM Ltd. With these three technologies, OGRE hopes to obtain the highest-resolution on-sky soft X-ray spectrum to date. We discuss the optical design of the OGRE payload.

Off-plane x-ray reflection gratings are theoretically capable of achieving high resolution and high diffraction efficiencies over the soft x-ray bandpass, making them an ideal technology to implement on upcoming x-ray spectroscopy missions. To achieve high effective area, these gratings must be aligned into grating modules. X-ray testing was performed on an aligned grating module to assess the current optical alignment methods. Results indicate that the grating module achieved the desired alignment for an upcoming x-ray spectroscopy suborbital rocket payload with modest effective area and resolving power. These tests have also outlined a pathway towards achieving the stricter alignment tolerances of future x-ray spectrometer payloads, which require improvements in alignment metrology, grating fabrication, and testing techniques.

The Off-plane Grating Rocket Experiment (OGRE) is a sub-orbital rocket payload that will make the highest spectral resolution astronomical observation of the soft X-ray Universe to date. Capella, OGRE’s science target, has a well-defined line emission spectrum and is frequently used as a calibration source for X-ray observatories such as Chandra. This makes Capella an excellent target to test the technologies on OGRE, many of which have not previously flown. Through the use of state-of-the-art X-ray optics, co-aligned arrays of off-plane reflection gratings, and an X-ray camera based around four Electron Multiplying CCDs, OGRE will act as a proving ground for next generation X-ray spectrometers.

Future soft X-ray spectroscopy missions have science requirements that demand higher instrument throughput and higher resolution than currently available technology. A key element in such spectrometers are dispersive elements such as diffraction gratings. Our group at Penn State University develops and fabricates off-plane reflection gratings in an effort to achieve the level of performance required by future missions. We present here efficiency measurements made in the 0.2 – 1.3 keV energy band at the Advanced Light Source (ALS) at Lawrence Berkley National Laboratory for one such grating, which was fabricated to achieve the high-throughput required for future observatories. This grating was replicated from a grating master using UV-nanoimprint techniques which are suitable for mass-production and is coated in a layer of gold. Total absolute diffraction efficiency was measured to be ~55-65% across the energy range, with relative diffraction efficiency approaching 90%. These results represent the first successful demonstration of off-plane grating replicas produced via these fabrication techniques and exceed the grating efficiency requirements for future X-ray missions.

The Water Recovery X-ray Rocket (WRXR) is a sounding rocket payload that will launch from the Kwajalein Atoll in April 2018 and seeks to be the first astrophysics sounding rocket payload to be water recovered by NASA. WRXR's primary instrument is a grating spectrometer that consists of a mechanical collimator, X-ray reflection gratings, grazing-incidence mirrors, and a hybrid CMOS detector. The instrument will obtain a spectrum of the diffuse soft X-ray emission from the northern part of the Vela supernova remnant and is optimized for 3rd and 4th order OVII emission. Utilizing a field of view of 3.25° × 3.25° and resolving power of λ/δλ ≈40-50 in the lines of interest, the WRXR spectrometer aims to achieve the most highly-resolved spectrum of Vela's diffuse soft X-ray emission. This paper presents introductions to the payload and the science target.

This paper presents a Lobster Eye (LE) X-ray telescope developed for the Water Recovery X-ray Rocket (WRX-R) experiment. The primary payload of the rocket experiment is a soft X-ray spectroscope developed by the Pennsylvania State University (PSU), USA. The Czech team participates by hard LE X-ray telescope as a secondary payload. The astrophysical objective of the rocket experiment is the Vela Supernova of size about 8deg x 8deg. In the center of the nebula is a neutron star with a strong magnetic field, roughly the mass of the Sun and a diameter of about 20 kilometers forming the Vela pulsar. The primary objective of WRX-R is the spectral measurement of the outer part of the nebula in soft X-ray and FOV of 3.25deg x 3.25deg. The secondary objective (hard LE X-ray telescope) is the Vela neutron star observation. The hard LE telescope consists of two X-ray telescopes with the Timepix detector. First telescope uses 2D LE Schmidt optics (2DLE- REX) with focal length over 1m and 4 Timepix detectors (2x2 matrix). The telescope FOV is 1.5deg x 1.5deg with spectral range from 3keV to 60keV. The second telescope uses 1D LE Schmidt optics (1D-LE-REX) with focal length of 25 cm and one Timepix detector. The telescope is made as a wide field with FOV 4.5deg x 3.5deg and spectral range from 3keV to 40keV. The rocket experiment serves as a technology demonstration mission for the payloads. The LE X-ray telescopes can be in the future used as all‐sky monitor/surveyor. The astrophysical observation can cover the hard X-ray observation of astrophysical sources in time-domain, the GRBs surveying or the exploration of the gravitational wave sources.

The X-ray astronomical telescopes in use today, such as Chandra and XMM-Newton, use X-ray grating spectrometers to probe the high energy physics of the Universe. These instruments typically use reflective optics for focussing onto gratings that disperse incident X-rays across a detector, often a Charge-Coupled Device (CCD). The X-ray energy is determined from the position that it was detected on the CCD. Improved technology for the next generation of X-ray grating spectrometers has been developed and will be tested on a sounding rocket experiment known as the Off-plane Grating Rocket Experiment (OGRE). OGRE aims to capture the highest resolution soft X-ray spectrum of Capella, a well-known astronomical X-ray source, during an observation period lasting between 3 and 6 minutes whilst proving the performance and suitability of three key components. These three components consist of a telescope made from silicon mirrors, gold coated silicon X-ray diffraction gratings and a camera that comprises of four Electron-Multiplying (EM)-CCDs that will be arranged to observe the soft X-rays dispersed by the gratings. EM-CCDs have an architecture similar to standard CCDs, with the addition of an EM gain register where the electron signal is amplified so that the effective signal-to-noise ratio of the imager is improved. The devices also have incredibly favourable Quantum Efficiency values for detecting soft X-ray photons. On OGRE, this improved detector performance allows for easier identification of low energy X-rays and fast readouts due to the amplified signal charge making readout noise almost negligible. A simulation that applies the OGRE instrument performance to the Capella soft X-ray spectrum has been developed that allows the distribution of X-rays onto the EM-CCDs to be predicted. A proposed optical model is also discussed which would enable the missions minimum success criteria's photon count requirement to have a high chance of being met with the shortest possible observation time. These results are compared to a Chandra observation to show the overall effectiveness of the new technologies. The current optical module is shown to narrowly meet the minimum success conditions whilst the proposed model comfortably demonstrates the effectiveness of the technologies if a larger effective area is provided.

Arcus, a Medium Explorer (MIDEX) mission, was selected by NASA for a Phase A study in August 2017. The observatory provides high-resolution soft X-ray spectroscopy in the 12-50Å bandpass with unprecedented sensitivity: effective areas of >450 cm^2 and spectral resolution >2500. The Arcus key science goals are (1) to 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) 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, circumstellar disks and exoplanet atmospheres form and evolve. Arcus relies upon the same 12m focal length grazing-incidence silicon pore X-ray optics (SPO) 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. The power and telemetry requirements on the spacecraft are modest. Mission operations are straightforward, as most observations will be long (~100 ksec), uninterrupted, and pre-planned, although there will be capabilities to observe sources such as tidal disruption events or supernovae with a ~3 day turnaround. Following the 2nd year of operation, Arcus will transition to a proposal-driven guest observatory facility.

The Water Recovery X-Ray Rocket (WRXR) was a suborbital rocket payload that was launched and recovered in April 2018. The WRXR flew two technologies being developed for future large x-ray missions: x-ray reflection gratings and a hybrid CMOS detector (HCD). The large-format replicated gratings on the WRXR were measured in ground calibrations to have absolute single-order diffraction efficiency of ∼60 % , ∼50 % , and ∼35 % at CVI, OVII, and OVIII emission energies, respectively. The HCD was operated with ∼6 e − read noise and ∼88 eV energy resolution at 0.5 keV. The WRXR was also part of a two-payload campaign that successfully demonstrated NASA sounding rocket water recovery technology for science payloads. The primary instrument, a soft x-ray grating spectrometer, targeted diffuse emission from the Vela supernova remnant over a field-of-view >10 deg2. The flight data show that the detector was operational during flight and detected x-ray events from an on-board calibration source, but there was no definitive detection of x-ray events from Vela. Flight results are presented along with a discussion of factors that could have contributed to the null detection.