In preparation for development of both key technologies and instrument concept studies to use those technologies, the Habitable Worlds Observatory Technology Maturation Project Office at the NASA Goddard Space Flight Center has compiled a series of statements of state of the art for those same key technologies. These statements are being provided to the public as exemplars and suggestions for possible future collaboration for those same instrument concept studies, but without mandate, to enable proposing teams to be able to find the technical solutions they need to field a compelling proposal. This information resides in the public domain and is presented without prejudice.

The Ultraviolet (UV) Type Ia Supernova CubeSat (UVIa) is a CubeSat/SmallSat mission concept that stands to test critical space-borne UV technology for future missions like the Habitable Worlds Observatory (HWO) while elucidating long-standing questions about the explosion mechanisms of Type Ia supernovae (SNe Ia). UVIa will observe whether any SNe Ia emit excess UV light shortly after explosion to test progenitor/explosion models and provide follow-up over many days to characterize their UV and optical flux variations over time, assembling a comprehensive multi-band UV and optical low-redshift anchor sample for upcoming high-redshift SNe Ia surveys (e.g., Euclid, Vera Rubin Observatory, Nancy Roman Space Telescope). UVIa's mission profile requires it to perform rapid and frequent visits to newly discovered SNe Ia, simultaneously observing each SNe Ia in two UV bands (FUV: 1500-1800A and NUV: 1800-2400A) and one optical band (u-band: 3000-4200A). In this study, we describe the UVIa mission concept science motivation, mission design, and key technology development.

The Ultraviolet Type Ia Supernova Mission (UVIa) is a CubeSat/SmallSat concept that stands to test critical space-borne ultraviolet (UV) technology for future missions such as the Habitable Worlds Observatory while elucidating long-standing questions about the explosion mechanisms of type Ia supernovae (SNe Ia). UVIa will observe whether any SNe Ia emit excess UV light shortly after explosion to test progenitor/explosion models and provide follow-up over many days to characterize their UV and optical flux variations over time, assembling a comprehensive multi-band UV and optical low-redshift anchor sample for upcoming high-redshift SNe Ia surveys (e.g., Euclid, Vera Rubin Observatory, and Nancy Roman Space Telescope). UVIa's mission profile requires it to perform rapid and frequent visits to newly discovered SNe Ia, simultaneously observing each SNe Ia in two UV bands [far-ultraviolet (FUV): 1500 to 1800 angstrom; near-ultraviolet (NUV): 1800 to 2400 angstrom] and one optical band (u-band: 3000 to 4200 angstrom). We describe the UVIa mission concept science motivation and basic mission design. The UVIa mission concept has been submitted to the CubeSats category of the NASA ROSES Astrophysics Research and Analysis program ($10M cost cap) and NASA Astrophysics Pioneers program ($20M cost cap).

The Nancy Grace Roman Space Telescope ("Roman") is a 2.4 m flagship astrophysics mission featuring a secondary coronagraph instrument (CGI) capable of directly imaging extrasolar planets and debris disks through starlight suppression. CGI will, for the first time, demonstrate a space-based platform for active wavefront control through adaptive optics and the use of photon-counting electron-multiplying charge coupled devices (EMCCDs). Integral to this demonstration are its two camera systems, EXCAM and LOCAM, that will enable contrast of up to 10-8 for science targets-a 100-fold improvement over current state-of-the-art technology. We detail the assembly, calibration, and integration of EXCAM and LOCAM into the CGI. The camera subassemblies are introduced with a description of their design, assembly, and functionality, followed by an explanation of the waveforms that specialize each camera. Calibration results from both the subsystem and instrument levels are presented alongside CGI performance requirements and suggestions for optimum performance across relevant operating scenarios. CGI is a critical step toward future missions targeted at direct imaging of Earth-like planets in the habitable zones of nearby stars. We conclude with recommendations for next-generation camera systems that can accommodate similar functionality to CGI while offering improved imaging performance and extended mission lifetime. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.

Here, we summarize Jet Propulsion Laboratory's optical coatings methods for silicon-based UV detectors and report on the latest developments. The topics to be covered include UV-optimized antireflection coatings, solar-blind UV bandpass filters, and patterned coatings yielding detectors with spatially varying responses spanning the UV and visible wavelength ranges. The latter innovation is achieved by combining well-established lithographic patterning techniques with optical coating techniques to produce butcher block-style AR coatings, similar to linear variable filters often used in infrared spectroscopy systems. With these patterned AR coatings, a detector's spatial response can be tailored according to the spectral dispersion of the optical system. Thus, high-throughput, wide-wavelength imaging and spectroscopy can be achieved on a single detector.

This paper discusses the further development of JPL's n-type superlattice doping (2D doping) process for sensitivity and stability enhancement of backside illuminated (BSI), p-channel CCDs and PMOS pixel CMOS imaging arrays. We discuss the results of the n-type 2D-doping of SRI's backside illuminated PMOS pixel 4k x 4k and 8k x 8k CMOS imagers. We briefly describe the backside processing parameters for the optimization of the 2D-doping process and antireflection coating design. Performance characterization, including quantum efficiency (QE), dark signal, and modulation transfer function (MTF) as a function of silicon epitaxial thickness and operating temperature will be discussed. These will be compared with the performance of devices produced using SRI's standard BSI processes.

Type Ia supernovae (SNe Ia) are a cornerstone of modern cosmology. Upcoming missions like the Nancy Grace Roman Telescope are pushing to high redshifts to measure cosmological parameters like the dark energy equation of state. Despite the impressive success of empirically standardizing their luminosities, the explosion mechanism of SNe Ia remains hotly debated; e.g., the mass of the white dwarf (WD) when it explodes and the state of the companion star (degenerate or non-degenerate) are all currently in question. Early-time UV observations are sensitive to the outermost layers of the ejecta (and least affected by the explosion itself) and show the most diversity for SNe Ia. This makes the UV bandpass an excellent probe to solve these open questions about the nature of these cosmological distance indicators. To achieve this science, we present UVIa, a CubeSat that will be reactive and have simultaneous optical, Near-UV (NUV), and Far-UV (FUV) coverage, takes advantage of state-of-the-art UV coatings, UV-enhanced silicon detectors with whitelight rejection filter, and autonomous observing scheduling, updated regularly based on newly discovered SNe Ia from modern transient surveys.

We report on the development of metal-dielectric bandpass filters that can be integrated with back-illuminated CMOS imaging sensors for operation at far ultraviolet wavelengths (FUV, 90-200 nm). These coatings utilize previous developments in atomic layer deposition (ALD) processes for transparent dielectric materials which are combined with evaporated aluminum layers in multilayer structures. Planar coatings can produce an FUV bandpass response that allows broadband silicon imaging sensors to operate with visible and solar blindness. We describe the fabrication and optical characterization of these coatings, and describe the development of delta-doped detectors integrating these coatings that are motivated by the performance requirements of the NASA astrophysics mission Ultraviolet Explorer (UVEX), currently undergoing a Phase A concept study. We also describe the extension of this concept to include graded thickness dielectric layers deposited by ALD. We show that a graded lateral thickness can be engineered in a variety of thermal ALD processes by depositing into a shallow horizontal cavity. This allows for the fabrication of detector-integrated filter coatings with a spatially-varying response that can be matched to the spectral dispersion of the planned UVEX spectrograph channel. Prototype graded coatings are demonstrated over areas up to 4 x 4 cm, and characterized for optical performance and environmental stability.

We present an overview of our work on design, development, and demonstration of simple and effective approaches to fabricating solid-state curved focal plane arrays (CFPAs) that have spawned a novel class of detector arrays. CFPAs can dramatically alter the capability and size of image systems, with an especially high impact in scientific and space applications in terms of science-instrument size, mass, simplicity, optical performance, and cost. The key to the simplicity of our approaches to curved focal plane arrays, implemented in thick, high-purity silicon or thinned membrane low-resistivity substrate detectors is that the curvature of the surface is independent of the VLSI fabrication process of imaging arrays. We present the principles of two approaches, results of fabrication of curved arrays, and results of analysis for limits of curving silicon arrays. New concepts and techniques were also developed as spin offs of this program for extreme curvature FPAs and infrared CPFAs.

Stability and photometric accuracy of silicon imaging detectors are essential for the Habitable Worlds Observatory and a range of NASA missions that will explore time domain astrophysics and astronomy over a spectral range spanning soft X-rays through the ultraviolet, visible, and near infrared. Detector stability is one of the oldest and most challenging problems in NASA missions. The challenges are particularly acute in the extreme ultraviolet range, where near-surface absorption of high-energy photons causes surfaces to degrade rapidly. In this paper, the effects of radiation-induced variability of surface charge on detector stability and photometric accuracy are analyzed in order to assess the implications for future NASA missions.

Radiation-induced damage and instabilities in back-illuminated silicon detectors have proved to be challenging in multiple NASA and commercial applications. In this paper, we develop a model of detector quantum efficiency (QE) as a function of Si-SiO2 interface and oxide trap densities to analyze the performance of silicon detectors and explore the requirements for stable, radiation-hardened surface passivation. By analyzing QE data acquired before, during, and after, exposure to damaging UV radiation, we explore the physical and chemical mechanisms underlying UV-induced surface damage, variable surface charge, QE, and stability in ion-implanted and delta-doped detectors. Delta-doped CCD and CMOS image sensors are shown to be uniquely hardened against surface damage caused by ionizing radiation, enabling the stability and photometric accuracy required by NASA for exoplanet science and time domain astronomy.

The Nancy Grace Roman Space Telescope Coronagraph is a JPL-led space-based instrument that will be the most sensitive instrument ever built for direct imaging and characterization of exoplanets in the visible. The instrument contrast is expected to be better than 1e-9, which implies that it will be capable of seeing exoplanets with an apparent magnitude < 30. With such a low brightness, only a few photons per hour will be perceived by its optical detectors. Two cameras will be used on the instrument for wavefront sensing, direct imaging and spectroscopy, with frame rates ranging from 1000 fps to less than 0.01 fps. For such a broad range of operating modes and industry leading noise figure, JPL has selected the 1024x1024 CCD201- 20 EMCCD from Teledyne-e2v as the image sensor for the two coronagraph cameras and appealed to Nüvü Caméras to adapt its most recent space controller design for the mission specifics. The new version of the camera readout electronics co-developed with ABB Space System group brings important improvements over the version flown at the edge of space in CSA’s 2018 STRATOS campaign namely on reliability, functionality, thermal control, power, volume and mass whilst preserving its unique noise performance. This paper presents an overview of the project and addresses the development of the delivered flight modules.

We present Hyperion, a mission concept recently proposed to the December 2021 NASA Medium Explorer announcement of opportunity. Hyperion explores the formation and destruction of molecular clouds and planet-forming disks in nearby star-forming regions of the Milky Way. It does this using long-slit, high-resolution spectroscopy of emission from fluorescing molecular hydrogen, which is a powerful far-ultraviolet (FUV) diagnostic. Molecular hydrogen (H2) is the most abundant molecule in the universe and a key ingredient for star and planet formation, but is typically not observed directly because its symmetric atomic structure and lack of a dipole moment mean there are no spectral lines at visible wavelengths and few in the infrared. Hyperion uses molecular hydrogen's wealth of FUV emission lines to achieve three science objectives: (1) determining how star formation is related to molecular hydrogen formation and destruction at the boundaries of molecular clouds; (2) determining how quickly and by what process massive star feedback disperses molecular clouds; and (3) determining the mechanism driving the evolution of planet-forming disks around young solar-analog stars. Hyperion conducts this science using a straightforward, highly-efficient, single-channel instrument design. Hyperion's instrument consists of a 48 cm primary mirror, with an f/5 focal ratio. The spectrometer has two modes, both covering 138.5-161.5 nm bandpasses. A low resolution mode has a spectral resolution of R>10,000 with a slit length of 65 arcmin, while the high resolution mode has a spectral resolution of R>50,000 over a slit length of 5 armin. Hyperion occupies a 2 week long, high-earth, Lunar resonance TESS-like orbit, and conducts 2 weeks of planned observations per orbit, with time for downlinks and calibrations. Hyperion was reviewed as Category I, which is the highest rating possible, but was not selected.

In this paper we review the physics and performance of back-illuminated CCDs. Models of back-illuminated CCDs are used to derive requirements for stable, strong surface passivation in space-relevant environments. Models and data are used to compare state-of-the-art surface passivation methods with 2D-doped surfaces. MBE growth of 2D-doped silicon on back-illuminated CCDs and CMOS image sensors enables near 100% charge collection efficiency with exceptional stability in space and other harsh environments. Lifetime tests performed on 2D-doped CMOS image sensors using pulsed DUV lasers have demonstrated the unique stability of 2D-doped detectors against high levels of radiation-induced surface damage. The insensitivity of 2D-doped detectors to Si-SiO2 traps has facilitated the development of a variety of coatings and filters with science-enabling capabilities for NASA instruments and missions in the far and near ultraviolet spectral range. We discuss the status and goals of a strategic partnership between JPL and Teledyne e2v for the certification of 2D-doping processes, and report initial results from our collaboration.

In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.

We report on the continued development of multilayer optical coatings on back-illuminated silicon imaging sensors in order to enhance the functionality of such systems at ultraviolet wavelengths. This includes the development metal-dielectric filter structures to enable solar-blind operation, and graded thickness coatings to tune the spatial response of a detector system to the dispersion of a spectrometer. Such systems can maintain the high internal quantum efficiency afforded by the delta-doping process utilized at NASA JPL, while also providing long-wavelength rejection or a spatially optimized efficiency (or both). We present the characterization of CCD and CMOS image sensors incorporating these processes, and describe the atomic layer deposition coating processes. Such detectors are currently being developed for ground-based high energy physics applications as well as NASA orbital astrophysics instruments operating at wavelengths shorter than 200 nm.