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We present here the current state of a collection of promising ultraviolet technologies in preparation for the Habitable Worlds Observatory. Working with experts representing a significant number of groups working in the ultraviolet, we summarize some of the leading science drivers, present an argument for a 100 nm blue wavelength cutoff, and gather current state of the art of UV technologies. We present the state of the art of contamination control, a crucial piece of the UV instrument plan. We explore next steps with individual technologies, as well as present paths forward with systems level testing and development.

FIREBall-2 is a stratospheric balloon-borne 1-m telescope coupled to a UV multi-object slit spectrograph designed to map the faint UV emission surrounding z~0.7 galaxies and quasars through their Lyman-alpha line emission. This spectro-imager had its first launch on September 22nd 2018 out of Ft. Sumner, NM, USA. Because the balloon was punctured, the flight was abruptly interrupted. Instead of the nominal 8 hours above 32 km altitude, the instrument could only perform science acquisition for 45 minutes at this altitude. In addition, the shape of the deflated balloon, combined with a full Moon, revealed a severe off-axis scattered light path, directly into the UV science detector and about 100 times larger than expected. In preparation for the next flight, and in addition to describing FIREBall-2's upgrade, this paper discusses the exposure time calculator (ETC) that has been designed to analyze the instrument's optimal performance (explore the instrument's limitations and subtle trade-offs).

Modern grating manufacturing techniques suffer from inherent issues that limit their peak efficiencies. The anisotropic etching of silicon facilitates the creation of custom gratings that have sharp and atomically smooth facets, directly addressing these issues. We describe work to fabricate and characterize etched silicon echelles optimized for the far ultraviolet (FUV; 90 - 180 nm) bandpass. We fabricate two echelles that have similar parameters to the mechanically ruled grating flown on the CHESS sounding rocket. We demonstrate a 42% increase in peak order efficiency and an 83% decrease in interorder scatter using these gratings. We also present analysis on where the remaining efficiency resides. These demonstrated FUV echelle improvements benefit the faint source sensitivity and high-resolution performance of future UV observatories., Comment: 21 pages, 13 figures, Accepted into Applied Optics

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., Comment: 16 pages, 11 pages (also published as a 2015 SPIE conference proceeding)

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

Surface-relief gratings fabricated through nanoimprint lithography (NIL) are prone to topographic distortion induced by resist shrinkage. Characterizing the impact of this effect on blazed diffraction efficiency is particularly important for applications in astrophysical spectroscopy at soft x-ray wavelengths ($\lambda \approx 0.5 - 5$~nm) that call for the mass-production of large-area grating replicas with sub-micron, sawtooth surface-relief profiles. A variant of NIL that lends itself well for this task is substrate-conformal imprint lithography (SCIL), which uses a flexible, composite stamp formed from a rigid master template to imprint nanoscale features in an inorganic resist that cures thermodynamically through a silica sol-gel process. While SCIL enables the production of several hundred imprints before stamp degradation and avoids many of the detriments associated with large-area imprinting in NIL, the sol-gel resist suffers shrinkage dependent on the post-imprint cure temperature. Through atomic force microscopy and diffraction-efficiency testing at beamline 6.3.2 of the Advanced Light Source, the impact of this effect on blaze response is constrained for a $\sim$160-nm-period grating replica cured at 90$^{\circ}$C. Results demonstrate a $\sim$2$^{\circ}$ reduction in blaze angle relative to the master grating, which was fabricated by anisotropic wet etching in $\langle 311 \rangle$-oriented silicon to yield a facet angle close to 30$^{\circ}$., Comment: 17 pages, 11 figures

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., Comment: 19 pages, 16 figures

Future soft X-ray (10 - 50 Angstrom) spectroscopy missions require higher effective areas and resolutions to perform critical science that cannot be done by instruments on current missions. An X-ray grating spectrometer employing off-plane reflection gratings would be capable of meeting these performance criteria. Off-plane gratings with blazed groove facets operated in the Littrow mounting can be used to achieve excellent throughput into orders achieving high resolutions. We have fabricated two off-plane gratings with blazed groove profiles via a technique which uses commonly available microfabrication processes, is easily scaled for mass production, and yields gratings customized for a given mission architecture. Both fabricated gratings were tested in the Littrow mounting at the Max-Planck-Institute for extraterrestrial Physics PANTER X-ray test facility to assess their performance. The line spread functions of diffracted orders were measured, and a maximum resolution of 800 $\pm$ 20 is reported. In addition, we also observe evidence of a `blaze' effect from measurements of relative efficiencies of the diffracted orders., Comment: 25 pages including references

An X-ray spectrograph consisting of radially ruled off-plane reflection gratings and silicon pore optics was tested at the Max Planck Institute for extraterrestrial Physics PANTER X-ray test facility. The silicon pore optic (SPO) stack used is a test module for the Arcus small explorer mission, which will also feature aligned off-plane reflection gratings. This test is the first time two off-plane gratings were actively aligned to each other and with a SPO to produce an overlapped spectrum. The gratings were aligned using an active alignment module which allows for the independent manipulation of subsequent gratings to a reference grating in three degrees of freedom using picomotor actuators which are controllable external to the test chamber. We report the line spread functions of the spectrograph and the actively aligned gratings, and plans for future development., Comment: Draft Version March 19, 2015