The X-Ray Imaging and Spectroscopy Mission (XRISM) satellite was successfully launched and put into a low-Earth orbit on September 6, 2023 (UT). The Resolve instrument onboard XRISM hosts an X-ray microcalorimeter detector, which was designed to achieve a high-resolution (≤7eV FWHM at 6 keV), high-throughput, and non-dispersive spectroscopy over a wide energy range. It also excels in a low background with a requirement of <2×ばつ10−3s−1keV−1 (0.3 to 12.0 keV), which is equivalent to only one background event per spectral bin per 100-ks exposure. Event screening to discriminate X-ray events from background is a key to meeting the requirement. We present the result of the Resolve event screening using data sets recorded on the ground and in orbit based on the heritage of the preceding X-ray microcalorimeter missions, in particular, the Soft X-ray Spectrometer onboard ASTRO-H. We optimize and evaluate 19 screening items of three types based on (1) the event pulse shape, (2) relative arrival times among multiple events, and (3) good time intervals. We show that the initial screening, which is applied for science data products in the performance verification phase, reduces the background rate to 1.8×ばつ10−3s−1keV−1 meeting the requirement. We further evaluate the additional screening utilizing the correlation among some pulse shape properties of X-ray events and show that it further reduces the background rate, particularly in the <2keV band. Over 0.3 to 12 keV, the background rate becomes 1.0×ばつ10−3s−1keV−1.

X-Ray Imaging and Spectroscopy Mission (XRISM) is an astronomical satellite with the capability of high-resolution spectroscopy with the X-ray microcalorimeter, Resolve, and wide field-of-view imaging with the charge-coupled device (CCD) camera, Xtend. Xtend consists of the mirror assembly (X-ray Mirror Assembly) and detector, Soft X-ray Imager (SXI). The SXI is composed of CCDs, analog and digital electronics, and a mechanical cooler. After the successful launch on September 6, 2023 (UT) and subsequent critical operations, the mission instruments were turned on and set up. The CCDs have been kept at the designed operating temperature of −110°C after the electronics and cooling system were successfully set up. During the initial operation phase, which continued for more than a month after the critical operations, we verified the observation procedure, stability of the cooling system, all the observation options with different imaging areas and/or timing resolutions, and time-tagged and automated operations, including those for South Atlantic Anomaly passages. We optimized the operation procedure and observation parameters, including the cooler settings, imaging areas for the small window modes, and the event selection algorithm. We summarize our policy and procedure of the initial operations for the SXI. We also report on a couple of issues we faced during the initial operations and lessons learned from them.

We discuss the design and performance of the vibration isolation system (VIS) used for the Resolve microcalorimeter on the X-Ray Imaging and Spectroscopy Mission (XRISM) spacecraft. Resolve makes high spectral resolution observations of celestial X-rays. XRISM was conceived as a recovery mission following the short-lived Hitomi mission. As such, the design of Resolve is similar to that of the soft X-ray spectrometer (SXS). A VIS was initially developed for the Hitomi SXS after discovering that vibrations from the cryocooler degraded the sensor’s performance. However, the VIS for Resolve was completely redesigned to include a hold-and-release mechanism to avoid damage to the compressor during launch or ground-based sine-vibe tests. The XRISM spacecraft was successfully launched in September 2023, confirming the functionality of the VIS while in orbit.

The spectroscopic performance of an X-ray microcalorimeter is compromised at high count rates. We utilize the Resolve X-ray microcalorimeter onboard the XRISM satellite to examine the effects observed during high-count rate measurements and propose modeling approaches to mitigate them. We specifically address the following instrumental effects that impact performance: CPU limit, pile-up, and untriggered electrical cross-talk. Experimental data at high count rates were acquired during ground testing using the flight model instrument and a calibration X-ray source. In the experiment, data processing not limited by the performance of the onboard CPU was run in parallel, which cannot be done in orbit. This makes it possible to access the data degradation caused by limited CPU performance. We use these data to develop models that allow for a more accurate estimation of the aforementioned effects. To illustrate the application of these models in observation planning, we present a simulated observation of GX 13+1. Understanding and addressing these issues is crucial to enhancing the reliability and precision of X-ray spectroscopy in situations characterized by elevated count rates.

The Soft X-ray Imager (SXI) is an X-ray charge-coupled device (CCD) camera of the Xtend system onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), which was successfully launched on September 7, 2023 (JST). During ground cooling tests of the CCDs in 2020/2021, using the flight-model detector housing, electronic boards, and a mechanical cooler, we encountered an unexpected issue. Anomalous charges appeared outside the imaging area of the CCDs and intruded into the imaging area, causing pulse heights to stick to the maximum value over a wide region. Although this issue has not occurred in subsequent tests or in orbit so far, it could seriously affect the imaging and spectroscopic performance of the SXI if it were to happen in the future. Through experiments with non-flight-model detector components, we successfully reproduced the issue and identified that the anomalous charges intrude via the potential structure created by the charge injection (CI) electrode at the top of the imaging area. To prevent anomalous charge intrusion and maintain imaging and spectroscopic performance that satisfies the requirements, even if this issue occurs in orbit, we developed a new CCD driving technique. This technique is different from the normal operation in terms of potential structure and its changes during imaging and CI. We report an overview of the anomalous charge issue, the related potential structures, the development of the new CCD driving technique to prevent the issue, the imaging and spectroscopic performance of the new technique, and the results of experiments to investigate the cause of anomalous charges.

We describe the development, design, ground verification, and in-orbit verification, performance measurement, and calibration of the timing system for the X-Ray Imaging and Spectroscopy Mission (XRISM). The scientific goals of the mission require an absolute timing accuracy of 1.0 ms. All components of the timing system were designed and verified to be within the timing error budgets, which were assigned by component to meet the requirements. After the launch of XRISM, the timing capability of the ground-tuned timing system was verified using the millisecond pulsar PSR B1937+21 during the commissioning period, and the timing jitter of the bus and the ground component were found to be below 15μs compared with the NICER (Neutron star Interior Composition ExploreR) profile. During the performance verification and calibration period, simultaneous observations of the Crab pulsar by XRISM, NuSTAR (Nuclear Spectroscopic Telescope Array), and NICER were made to measure the absolute timing offset of the system, showing that the arrival time of the main pulse with XRISM was aligned with that of NICER and NuSTAR to within 200μs. In conclusion, the absolute timing accuracy of the bus and the ground component of the XRISM timing system meets the timing error budget of 500μs.

We report the results from the ground and on-orbit verifications of the X-ray Imaging and Spectroscopy Mission timing system when the satellite clock is not synchronized to the Ground Positioning System (GPS) time. In this case, the time is determined by a free-run quartz oscillator of the clock, whose frequency changes depending on its temperature. In the thermal vacuum test performed in 2022, we obtained the GPS unsynchronized mode data and the temperature-versus-clock frequency trend. Comparing the time values calculated from the data and the true GPS times when the data were obtained, we confirmed that the requirement (within a 350-μs error in the absolute time, accounting for both the spacecraft bus and ground systems) was satisfied in the temperature conditions of the thermal vacuum test. We also simulated the variation of the timing accuracy in the on-orbit temperature conditions using the Hitomi on-orbit temperature data and found that the error remained within the requirement over ∼3×ばつ105s. The on-orbit tests were conducted in 2023 September and October as part of the bus system checkout. The temperature-versus-clock frequency trend remained unchanged from that obtained in the thermal vacuum test, and the observed time drift was consistent with that expected from the trend.

The X-Ray Imaging and Spectroscopy Mission (XRISM) is the seventh Japanese X-ray observatory, with development and operation that are in collaboration with universities and research institutes in Japan, the United States, and Europe, including Japan Aerospace Exploration Agency (JAXA), National Aeronautics and Space Administration (NASA), and European Space Agency. The telemetry data downlinked from the satellite are reduced to scientific products using pre-pipeline (PPL) and pipeline software running on standard Linux virtual machines (VMs) for the JAXA and NASA sides, respectively. Observation IDs (OBSIDs) identified the observations, and we had 80 and 161 OBSIDs to be reprocessed at the end of the commissioning period and performance verification and calibration period, respectively. The combination of the containerized PPL utilizing Singularity of a container platform running on JAXA’s "TOKI-RURI" high-performance computing (HPC) system and working disk images formatted to ext3 accomplished a 33×ばつ speedup in PPL tasks over our regular VM. Herein, we briefly describe the data processing in XRISM and our porting strategies for PPL in the HPC environment.

The X-Ray Imaging and Spectroscopy Mission satellite was launched on September 6, 2023 (UT). Its Resolve instrument is a high-resolution X-ray spectrometer enabled by a microcalorimeter array thermally anchored to a 50-mK heat sink. Many sensitive, critical sub-systems comprise Resolve, including a multistage cryogenic cooling system, thin-film aperture filters, low-noise electronics, on-board signal processing, and several sources of X-rays for calibration. We summarize the initial on-orbit power-on and checkout of Resolve that commenced immediately after launch. Soon after launch, the cryocoolers were activated, and their operation was successfully established. On October 9, 2023, the first cycle of the adiabatic demagnetization refrigerator was carried out, bringing the sensors to their steady-state operational temperatures. Following this, the energy resolution at 5.9 keV was successfully measured. The energy scale of the system is highly sensitive to the thermal environment surrounding both the sensors and their analog electronics. Gain correction was performed using reference X-ray lines from onboard calibration sources. To optimize cooler frequency settings, noise spectra were collected across a range of frequencies, and the most suitable frequency pair was selected based on the in-orbit environment. During the final phase of the checkout, an attempt was made to open the gate valve, which is designed to protect the Dewar’s interior from external pressure during ground operations and launch. Unfortunately, this attempt was unsuccessful. As a result, the checkout process was temporarily paused, and a stable operational strategy was subsequently developed to enable Resolve to function effectively with the gate valve remaining closed.

The X-ray Imaging and Spectroscopy Mission observatory was launched on September 7, 2023, from the Tanegashima Space Center in Japan. Resolve, one of its two instruments, performs high-resolution spectroscopy in the soft X-ray band (0.2 to 13 keV) using a 6×ばつ6 microcalorimeter array. The array is cooled to 50 mK by a three-stage adiabatic demagnetization refrigerator (ADR), which is linked to both a liquid helium dewar (at <1.2K) and a Joule–Thomson (JT) cryocooler operating at <4.5K. Although, liquid helium is present, two of the ADR stages provide detector cooling at 50 mK and auxiliary cooling to 0.5 K to intercept some parasitic heat loads while rejecting waste heat to the helium. Once the helium is exhausted, Resolve enters a cryogen-free mode in which all three ADR stages are operated to provide detector cooling at 50 mK and to continuously cool the helium tank to 1.4 K. In this mode, waste heat is rejected by the JT cryocooler. The cryogen-free operation can be sustained as long as the JT and other cryocoolers remain fully operational. At launch, the helium tank contained ∼35.4L of liquid. Within a few days, the helium cooled below 1.15 K, with an estimated 35.0 L remaining. With an expected time average heat load of 0.68 mW, the helium lifetime was projected to exceed 4 years, but measurements of He volume on orbit suggest a significantly longer lifetime. Details of the ADR’s design and on-orbit performance in "cryogen mode" are presented.

The Resolve instrument was launched on board the XRISM observatory in early September 2023. The Resolve spectrometer is based on a high-sensitivity X-ray calorimeter detector system (DS) that has been successfully deployed in many ground and sub-orbital spectrometers. However, the Resolve instrument is the first long-term implementation in space. The instrument will provide essential diagnostics for nearly every class of X-ray emitting objects, from galactic supernova remnants to the outskirts of galaxy clusters, without degradation for spatially extended objects. The Resolve DS consists of a 36-pixel microcalorimeter array operated at a heat sink temperature of 50 mK. In pre-flight testing, the DS demonstrated a resolving power of better than 1300 at 6 keV with a simultaneous bandpass from below 0.3 keV to above 12 keV and a timing precision better than 100μs. An anti-coincidence detector placed directly behind the microcalorimeter array effectively suppresses background. The detector energy-resolution budget included terms for interference from the Resolve cooling system and the spacecraft. Additional terms for energy-scale stability, on-orbit effects, and use of mid-grade events were also included, predicting an end-of-life, on-orbit performance for high- and mid-resolution grade events that meet the requirement of 7 eV FWHM at 6 keV. Here, we discuss the actual on-orbit performance of the Resolve DS and compare this with the performance in pre-flight testing, on-orbit predictions, and the almost identical Hitomi/SXS instrument. We will also discuss the on-orbit gain stability, an assessment of on-orbit interference, and measurements of the on-orbit background.

The X-Ray Imaging and Spectroscopy Mission (XRISM) is a Japanese International X-ray observatory, launched in September 2023. The XRISM science operations team (SOT) has been responsible for organizing and preparing for in-orbit science operations since the early stage of the project and has been performing quick-look and pipeline processes for data monitoring to provide the data to users as the operations of the payload instruments began in the initial operation phase. The target observations, including transient objects, were initiated from the nominal operations phase using the short-/long-term observation plans. The SOT has also contributed to performance verification and optimization activities to provide well-calibrated data and analysis tools and established a help desk to support guest observers (GOs) analyzing the XRISM data. The publicly solicited observations for GOs started from September 2024. These daily science operations have been carried out by dedicated scientists at the Japan Aerospace Exploration Agency, with the support of the other SOT members and the mission and instrument teams. This study introduces the ground system used for the XRISM science operations and describes how in-orbit science operations have been established by the SOT from the system development phase to the cycle 1 period.

Accurate and precise correction of the gain drift is the key to achieve the required energy resolution of the Resolve microcalorimeter spectrometer on the X-ray Imaging and Spectroscopy Mission (XRISM). Therefore, Resolve is equipped with highly configurable X-ray sources called the modulated X-ray source (MXS). The pulsed nature allows us to separate calibration and astrophysical X-rays by time interval selections. However, undesirable characteristics of the MXS, such as the afterglow X-rays, restrict the allowed configuration range. Moreover, the nonlinear and discontinuous behaviors of the calibration line count rate make the determination of the optimal setting highly complex. The MXS count rate model has been established using measurements in the spacecraft thermal vacuum test with the flight detector and MXS. A trade-off study using the model enables us to choose a few settings for the continuous use of the MXS optimized for different ranges of target gain tracking intervals. An alternative approach, where the MXS is used only intermittently, has also been developed and implemented. This new mode enables us to reconstruct the drift without having most of the undesirable effects in science data. This also forms the basis of the gain tracking under the current Resolve configuration with the closed gate valve.

Resolve is a high-resolution X-ray spectrometer onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), launched on September 6 (UT), 2023. The Resolve has performed better than its required spectral resolution (7 eV at full width at half maximum at 6 keV), both on the ground and in orbit, and has been confirmed to have comparable performance to the soft X-ray spectrometer onboard the ASTRO-H (Hitomi) satellite. The focal plane is composed of an array of microcalorimeter detectors operated at 50 mK to achieve the required energy resolution, and the cooling system is designed to satisfy the lifetime requirement of over 3 years. The focal plane and cooling system are contained in a vacuum-insulated dewar. The cooling system is equipped with a two-stage adiabatic demagnetization refrigerator (ADR) that uses superfluid liquid helium (LHe) as its heat sink. The system includes a third ADR stage that can be used to provide the heat sink when the helium is exhausted. A Joule–Thomson cooler and several two-stage Stirling coolers are used to reduce the heat load on the LHe. During pre-launch operations, we carried out a superfluid LHe top-off operation. The resultant amount of LHe onboard Resolve was over 35 L before launch, which is sufficient to meet the lifetime requirement. During post-launch operation, the LHe vent valve was opened 5 min after launch during rocket acceleration, and the cryocoolers were turned on after several orbits, as planned, which established stable cooling within the dewar. Pre- and post-launch operations for the Resolve instrument were planned around multiple constraints from launch vehicle operations; all were successfully completed, and the launch requirements were fully met.

The Resolve soft X-ray spectrometer is a high spectral resolution microcalorimeter spectrometer for the X-ray Imaging and Spectroscopy Mission. In the beam of Resolve, there is a filter wheel containing X-ray filters. In the beam, there is also an active calibration source, the modulated X-ray source (MXS), which can provide pulsed X-rays to facilitate gain calibration. The filter wheel consists of six filter positions. Two open positions, one Fe55 source to aid in spectrometer characterization during the commissioning phase, and three transmission filters: a neutral density filter, an optical blocking filter, and a beryllium filter. The X-ray intensity, pulse period, and pulse separation of an MXS are highly configurable. Furthermore, the switch-on time is synchronized with the spacecraft’s internal clock to give accurate start and end times of the pulses. One of the issues raised during ground testing was the susceptibility of an MXS at high voltage to ambient light. Although measures were taken to mitigate the light leak, the efficacy of those measures must be verified in orbit. Along with an overview of issues raised during ground testing, we will discuss the calibration source and the filter performance in-flight and compare with the transmission curves present in the Resolve calibration database.

The Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM) consists of an array of 6×ばつ6 silicon-thermistor microcalorimeters cooled down to 50 mK and a high-throughput X-ray mirror assembly (XMA) with a focal length of 5.6 m. XRISM is a recovery mission of ASTRO-H/Hitomi, and the Resolve instrument is a rebuild of the ASTRO-H Soft X-ray spectrometer (SXS) and the Soft X-ray Telescope (SXT) that achieved energy resolution of ∼5eV FWHM on orbit, with several important changes based on lessons learned from ASTRO-H. The flight models of the Dewar and the electronics boxes were fabricated, and the instrument test and calibration were conducted in 2021. By tuning the cryocooler frequencies, energy resolution better than 4.9 eV FWHM at 6 keV was demonstrated for all 36 pixels and high-resolution grade events, as well as energy-scale accuracy better than 2 eV up to 30 keV. The immunity of the detectors to microvibration, electrical conduction, and radiation was evaluated. The instrument was delivered to the spacecraft system in April 2022. The XMA was tested and calibrated separately. Its angular resolution is 1.27′, and the effective area of the mirror itself is 570cm2 at 1 keV and 424cm2 at 6 keV. We report the design and the major changes from the ASTRO-H SXS, the integration, and the results of the instrument test.

The Resolve X-ray imaging spectrometer onboard the X-ray Imaging and Spectroscopy Mission consists of a 36 pixel array of high-resolution X-ray calorimeters each with ∼5eV full-width-at-half-maximum (FWHM) spectral resolution in the 0.3 to 12 keV band. The response to monochromatic X-rays (line spread function, LSF) is composed of a narrow Gaussian core and weak extended components caused by energy loss during thermalization. We report on the characterization of the Gaussian core LSF in an extensive ground calibration campaign. We also discuss the characterization of on-orbit resolution, which shows slightly higher FWHM than that obtained on the ground.

CASTOR is a proposed wide-field (30′×ばつ30′=0.25deg2), high-resolution (FWHM∼0.15′′), 1-m-diameter space telescope that is under development by the Canadian Space Agency and the National Research Council of Canada. Optimized for UV/blue-optical wavelengths, the telescope uses dichroics to enable imaging in three channels (and up to five bands) that cover the 0.15 to 0.55μm spectral region, simultaneously. CASTOR will also feature low- and low-medium-resolution spectroscopic capabilities through the use of a deployable grism for low-resolution (R≲420) slit-less spectroscopy in its UV and u channels, and low-medium-resolution R∼1400 multi-object spectroscopy in a parallel field using a digital micro-mirror device. High-speed, precision photometry will be possible using dedicated CMOS detectors in each of its three channels. We present an overview of the mission, including the optical design, instruments and detectors, payload layout, satellite bus, orbit, and ground segment. We describe the mission’s scientific capabilities and expected place within the astronomical landscape in the 2030s. The 5-year lifetime is baselined on a combination of legacy surveys, guest observer programs, and target-of-opportunity science. We summarize scientific plans for the mission in each of eight fields: cosmology, time domain and multi-messenger science, active galactic nuclei, galaxies, near-field cosmology, stellar astrophysics, exoplanets, and solar system studies. We conclude by describing ongoing development efforts, highlighting areas of particular relevance for NASA’s Habitable Worlds Observatory.

NASA’s Habitable Worlds Observatory (HWO) concept and the 2020 Decadal Survey’s recommendation to develop a large space telescope to "detect and characterize Earth-like extrasolar planets" require new starlight suppression technologies to probe a variety of biomarkers across multiple wavelengths. Broadband absorption due to ozone dominates Earth’s spectrum in the mid-ultraviolet (200 to 300 nm) and can be detected with low spectral resolution. Despite the high value of direct ultraviolet (UV) exoplanet observations, high-contrast coronagraph demonstrations have yet to be performed in the UV. Typical coronagraph leakage sources such as wavefront error, surface scatter, polarization aberrations, and coronagraph mask quality all become more significant in the UV and threaten the viability of HWO to produce meaningful science in this regime. As a first step toward a demonstration of UV coronagraphy in a laboratory environment, we develop an end-to-end model to produce performance predictions and a contrast budget for a vacuum testbed operating at wavelengths from 200 to 400 nm. At 300 nm, our model predicts testbed performance of ∼3×ばつ10−9 contrast in a narrow 2% bandwidth and ⪅10−8 in a 5% bandwidth, dominated primarily by the chromatic residuals from surface errors on optics that are not conjugate to the pupil.

We present the design, development, and end-to-end testing of a unique setup for characterizing the noise performance of silicon-based, photon-counting detectors, using delta-doped detectors developed at Jet Propulsion Lab’s Microdevices Laboratory in collaboration with Teledyne-e2v. Combined with atomic layer deposition coatings, delta-doped detectors have been demonstrated to achieve high quantum efficiency (QE) in the ultraviolet, enabling several UV missions (e.g., FIREBall-2, UVEX, SPARCS, and SHIELDS) and proposals (e.g., Hyperion, UVscope, Eos, and others). Understanding the noise performance of these detectors and developing strategies and designs to minimize that noise is important for future applications such as the Habitable Worlds Observatory (HWO). For instance, delta-doped electron multiplying charge-coupled devices have been identified as a target technology for HWO. This test setup is designed to investigate the impact of the ambient thermal environment, where these detectors are operated, on their noise performance, specifically focusing on the dark current plateau observed below 163 K. This plateau limits the signal-to-noise ratio that can be achieved in the photon-counting mode and has broader implications for the noise performance of silicon-based detectors. The test bench incorporates a delta-doped Teledyne-e2v CCD201-20 readout with a Nüvü CCCP v3 controller at 1 MHz and features a dual cooling system: a cryocooler for the detector and a liquid nitrogen–cooled thermal shroud to simulate a temperature-controlled ambient environment. We describe the design of the test setup, including independent thermal control for the detector and shroud, as well as the validation, optimization, and characterization process for the testbed. The testbed allows for further characterization of the noise performance of the detector, optimization of readout sequences, and operations for low clock-induced charge. First measurements of dark rate were taken across a range of detector temperatures (183 K to 143 K), shroud temperatures (298 K to 180 K), with substrate voltage set to 0 V. We find that the measured dark rate is notably lower with the shroud is cooled to 230 K in comparison with similar measurements with a shroud at 298 K. The reduction in dark rate is potentially due to a decrease in optical/NIR photons emitted from the shroud.

The next generation of exoplanet direct imaging missions will focus on detecting and characterizing Earth-like planets across the ultraviolet (UV), optical, and near-infrared (NIR) spectrum. Starshades operating in the UV offer high throughput, high contrast, and broad spectral bandwidth, making them a valuable complement to coronagraphs as a characterization instrument. We introduce high-fidelity simulations of UV starshade observations of an Earth-twin orbiting a Sun-like star at 10 parsecs. The simulations incorporate conservative estimates of starshade-specific systematics such as petal shape and position errors, solar and surface glint, micrometeoroid holes, formation flying errors, and contaminated edges, alongside local zodiacal dust and resonant exozodiacal debris disks. To estimate the planetary signal from the simulated observation, we implement a post-processing pipeline consisting of imperfect starshade calibration, parametric exozodi estimation, and a matched filter. Finally, we present a sensitivity analysis of a starshade’s ability to recover high signal-to-noise measurements of an Earth-like planet as a function of system inclination, planet phase angle, and exozodiacal dust density. This approach is applied to a 35-m UV starshade optimized for the future Habitable Worlds Observatory (HWO). The results for the HWO starshade indicate that it is possible to achieve an SNR≥10 in under 3 days of observation across a wide range of cases. For inclinations ≤30deg, an SNR≥10 is possible for systems with up to 50 times the Solar System’s dust density or 50 zodis. This performance extends to 20 zodis for 60-deg inclined system, even at unfavorable crescent planet phases. Evaluating the impact of residual noise on the extracted spectra with resolution R=10 at 250 nm reveals that it is possible to obtain measurements of the 0.25μm ozone feature with between 1% and 5% error for inclinations ≤60deg and ≤20 zodis.

A future ultraviolet (UV) large strategic mission will require a capable and qualified far-UV detector. Microchannel plate (MCP) detectors provide unique capabilities for space-based astrophysics and have extensive flight heritage. MCPs can be obtained in large geometric form factors (up to 20×ばつ20cm2). They have operational characteristics that include: a broad input energy bandwidth, further tailorable by photocathode selection, large global and local photon-counting dynamic range capabilities, an intrinsically low dark count rate, and support high spatial and temporal resolution. The initialization of an MCP event is purely photoemissive and is agnostic to readout architecture, so the backend event handling is adaptable. This flexibility allows the technology to support a diverse set of mission requirements. Implementations can vary widely from supporting low-power, long-lifetime, planetary missions to large area, high spatial resolution, low background Earth-orbiting sensors, as well as low-cost access capabilities—rugged rocket flights and CubeSats. The backend sensing element of the imaging device is typically achieved by one of several means: cross delay line (XDL) anodes, image intensifiers (phosphor screens), cross strip (XS) anodes, or a pixelated charge sensing complementary metal-oxide-semiconductor (CMOS) approach. MCP detector technology has improved over the years when compared with a previous UV flagship mission [e.g., Hubble Space Telescope – Cosmic Origins Spectrograph (HST-COS)]. Improvements in MCP background, lifetime, and gain stability have been enabled by atomic layer deposited (ALD) resistive and secondary emissive layers. XS and pixelated backend readout approaches allow for lower gain operation which further improves the detector’s local and global rate capability as well as detector lifetime. In addition, these backend approaches require less power to operate while also allowing for higher dynamic event capture and improved spatial and temporal resolving power. These sensor properties are achieved without cooling, or out-of-band filtering, and constitute a high signal-to-noise (S/N) photon-counting and imaging detector capability well suited for prospective National Aeronautics and Space Administration missions.

How gas gets into, through, and out of galaxies is critical to understanding galactic ecosystems. The disk-circumgalactic medium (CGM) interface region is uniquely suited for studying processes that drive gas flows. Matter and energy that enter and leave a galaxy pass through this region; however, the precise pathways are yet to be explored. We discuss future observations that will facilitate the discovery of the gas flow pathways in galaxies and the telescope parameters necessary for making those observations. We advocate for high spectral resolution ultraviolet spectroscopic capabilities on the Habitable Worlds Observatory (HWO) that will enable observations at a wavelength range of 940 to 3500 Å (minimum range 970 to 3000 Å) and at a resolution of 100,000 (minimum of 50,000). We advocate for a multi-object spectrograph with thousands of sub-arcsec slitlets and a field of view 6′×ばつ6′. We also recommend that the spectrograph be sensitive enough to achieve a signal-to-noise ratio of 10 or higher within a few hours for a continuum source of 21 AB magnitude and estimate an optimal aperture size of 8 m. These capabilities would enable the characterization of gas in the disk-halo interface, leading to breakthroughs in our understanding of the gas flows and galactic ecosystems.

We present a new program aimed at developing a new generation of micromirror devices specifically tailored for astronomical applications, multislit spectroscopy in particular. We first overview the general characteristics of multi-object spectrographs based on the current digital micromirror devices (DMDs), with a particular focus on the newly deployed SAMOS instrument at the 4.1-m SOAR telescope on Cerro Pachon. We illustrate the operational advantages of DMD-based instruments and the technical limitations of the currently available devices, the DMDs produced by Texas Instruments (TI). We then introduce the baseline and target parameters of the new micromirror devices (MMDs) that we plan to develop with the goal of reaching technology readiness level 5 by mid-2029 as required by the Habitable Worlds Observatory (HWO) timeline. We conclude with a brief illustration of the exciting potential of MMD-based spectrographs for an 8-m class space telescope such as HWO.

We describe efforts to develop broadband mirror coatings with high performance that will extend from the far-ultraviolet (FUV) to infrared wavelengths. Our team at the Goddard Space Flight Center has developed a reactive physical vapor deposition (rPVD) process that combines a fluorination with a XeF2 gas (which grants a thin AlF3 layer) in between the Al and the metal-fluoride protection layer (either LiF or MgF2) that are done with the conventional PVD process. This recently developed rPVD process produces protected Al mirrors coatings with an improved average FUV reflectance between 10% and 15% higher (when compared with conventionally prepared samples). We have termed these coatings as XeLiF when the dielectric overcoat is LiF or XeMgF2 when the dielectric overcoat is MgF2. The XeLiF-coated Al mirrors meet current goals for advanced broadband mirrors in the FUV (R>70% at 103 nm and R>80 above 110 nm), whereas the XeMgF2 provides R>80% above 115 nm. The IR/Vis/UV reflectance for either XeLiF or XeMgF2 mirrors is similar to the theoretical reflectance of bare aluminum at wavelengths >200nm. In addition, long-term lifetime testings of XeLiF mirrors indicate the rPVD process produces more environmentally stable coatings, where a XeLiF sample showed a degradation in the average FUV reflectance of around 1% to 2% when stored in a relative humidity of 40% over a period of 3.5 years. These results are a remarkable improvement when compared with conventionally prepared Al+LiF samples that would degrade their FUV reflectance in a matter of weeks or months when exposed to those kinds of relative humidity levels. Surface topographies on several XeLiF samples with varying Al and LiF thicknesses have been measured with an atomic force microscope (AFM). The root mean square (RMS) roughness (σ) values derived from these AFM results have ranged between 0.6 and 0.9 nm. For comparison, samples without the Xe process start off by having an RMS roughness that is 30% larger than samples treated with the XeF2 gas. We have also determined that these roughness values are showing a slight increase, ranging between 0.9 and 1.0 nm, when samples are exposed to room temperature and relative humidity as high as 50% over one week. Both of these key performance parameters (environmental stability in reflectance and smoothness of ≤1nm) are key considerations for using the XeLiF coating in the primary and secondary mirrors of the Habitable Worlds Observatory (HWO). We also show evidence that the rPVD coating process is compatible with deposition on Si-based gratings. It is known that XeF2 vapor is a strong Si etchant, thus the demonstration that the native SiO2 layer on Si test samples is sufficient to protect the groove profile of E-beam-ruled Si gratings from degradation is an important and significant finding.

Liquid crystal materials for making vector vortex waveplates for ultraviolet wavelengths have been investigated, and both an appropriate alignment material and a polymerizable liquid crystal monomer that is stable in thin layers have been identified. These materials were used to manufacture both uniform half-wave plates and vector vortex waveplates for ultraviolet wavelengths. A laser line focus was used to optically record the vortex waveplates on a rotating substrate. We describe two fabricated monochromatic vector vortex waveplates with measured half-wave wavelengths of 353 and 325 nm. These waveplates show good geometric vortex patterns all the way down to central defect regions as small as 3μm. Although these initial masks were designed for single-wavelength operation to first investigate materials and establish fabrication feasibility, it should next be possible to make broadband ultraviolet vortex masks using established multilayer techniques. Such broadband ultraviolet vortex masks could be of interest for coronagraphic exoplanet observations at ultraviolet wavelengths.

Our understanding of cosmology is shaped by type Ia supernovae (SNe Ia), the runaway thermonuclear detonations of white dwarfs via accretion from a companion star. The nature of this companion star is highly debated, with disparate models explaining the currently available SNe Ia data. Critical ultraviolet (UV) signatures of SNe Ia progenitors are only observable within the first few days post-detonation. We present the instrument design of the Ultraviolet Type Ia (UVIa) Supernova Mission, a proposed SmallSat to make early UV observations of SNe Ia. UVIa conducts simultaneous observations in three photometric channels: far-UV (1500 to 1800 Å), near-UV (1800 to 2400 Å), and Sloan u-band (3000 to 4200 Å). UVIa employs two 80-mm double-offset Cassegrain UV telescopes and a similar 50-mm u-band telescope, imaging onto three Teledyne e2v CIS120-10-LN complementary metal-oxide semiconductor (CMOS) detectors. The UV detectors are delta-doped for enhanced sensitivity, with custom metal-dielectric filters providing further in-band efficiency and red light rejection. The UV optics utilize multi-layer coatings, defining the UV bandpasses and providing additional red light rejection. The instrument design achieves high UV sensitivity (21.5 mag AB) and superior red light rejection (<10−5 throughput), allowing UVIa to make early observations of SNe Ia while serving as a pathfinder for future UV transient telescopes.

The Star-Planet Activity Research CubeSat (SPARCS) is a NASA-funded 6U-CubeSat mission designed to monitor ultraviolet (UV) radiation from low-mass stars. These stars’ relatively high-frequency and high-energy UV flares significantly affect the atmospheres of orbiting exoplanets, driving atmospheric loss and altering the conditions for habitability. SPARCS aims to capture time-resolved photometric data in the far-UV and near-UV simultaneously to better characterize the flares and detect the strongest and rarest among them. In addition, SPARCS is testing innovative technology, such as delta-doped detectors with near 100% internal quantum efficiency and detector-integrated metal-dielectric UV bandpass filters. This mission will increase the technology readiness level of these critical components, positioning them for inclusion in future flagship missions such as the Habitable Worlds Observatory. We outline SPARCS’ mission goals and provide an update as the spacecraft is completed and awaits its planned late-2025 launch to a sun-synchronous low-Earth orbit. We also highlight the critical role of small missions in providing training and leadership development opportunities for students and researchers, advancing technology for larger observatories, and share lessons learned from collaborations among academic, government, and industry partners.

We present a science case for the Habitable Worlds Observatory (HWO) to map the circumgalactic medium (CGM) in emission by targeting ultraviolet emission lines, which trace the 104 to 106K gas engaged in the feedback and accretion mechanisms driving galaxy evolution. Although the CGM–galaxy connection is clearly evident through absorption line experiments and limited work has been done in optical and radio emission from the ground, the nature of this connection is poorly understood with regard to how these cosmic ecosystems exchange matter and energy. We outline a two-pronged experiment with HWO utilizing both multi-object spectroscopy to map kpc-scale CGM structures such as galactic superwinds and integral field spectroscopy to unveil the sub-kpc-scale processes such as thermal instabilities, which are theorized to govern the cool gas reservoirs long detected in pencil-beam absorption surveys.

The oxygenation of Earth’s atmosphere 2.3 billion years ago, which on exoplanets is expected to be most detectable via the UV ozone feature at ∼0.5 microns, is often regarded as a sign of the emergence of photosynthetic life. On exoplanets, we may similarly expect life to oxygenate the atmosphere, but with a characteristic distribution of emergence times. In this paper, we test our ability to recover various "true" emergence time distributions as a function of (1) stellar age uncertainty and (2) number of Earth analogs in the sample. The absolute uncertainties that we recover, for diverse underlying distributions, are mostly independent of the true underlying distribution parameters and are more dependent on sample size than stellar age uncertainty although both influence the recoveries. For a sample size of 30 Earth analogs and a Habitable Worlds Observatory architecture sensitive to ozone at 1% of the current atmospheric level on Earth, we find that no ozone detections across the entire sample would place a 10σ limit on the mean time of ozone emergence, regardless of stellar age uncertainty.

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.

Aspera is a far ultraviolet (FUV) SmallSat mission in the NASA Astrophysics Pioneers Program with the science objectives surrounding detection and mapping of the warm-hot circumgalactic medium in emission for the first time in nearby galaxies. Aspera comprises a pair of identical long-slit FUV spectrographs optimized to detect faint extended source emission at ∼103nm. The operations phase of the mission will include a commissioning phase, a primary science phase, and a closeout phase. Placed in a Sun-synchronous 500 to 600 km orbit, Aspera will operate in detection, mapping, and calibration modes during the primary science phase to achieve the mission’s science objectives. We note that minor damage outside of the clear aperture of the off-axis parabola mirrors was discovered during the application of high reflectance FUV coatings. It was determined that this damage was likely due to a cold welding effect when the Al optic holder came in contact with the contact point regions of the optic during the enhanced lithium fluoride coating process. These features do not affect the performance of the optic, nor do they pose any structural risk, and they can be avoided for future projects through material selection. The payload critical design is complete, and assembly of the payload began as of summer 2024.

Integral field spectroscopy allows for spectral mapping of extended sources in a time-efficient manner. An integral field unit (IFU) in the ultraviolet on Habitable Worlds Observatory (HWO) could be used to quickly map extended objects such as supernova remnants or galaxies and their surroundings, but there are technical challenges to an ultraviolet IFU. The Integral Field Ultraviolet Spectroscopic Experiment (INFUSE), a sounding rocket project, is the first static configuration far ultraviolet integral field spectrograph. INFUSE features an f/16, 0.49 m Cassegrain telescope and a 26-element image slicer feeding 26 replica holographic gratings, with spectra imaged by the largest cross-strip microchannel plate detector flown in space. The first launch of INFUSE occurred from White Sands Missile Range on October 29, 2023, and demonstrated spectral multiplexing, successfully detecting ionizing gas emission in the XA region of the Cygnus Loop. INFUSE will launch again in fall 2025 to observe NGC 2366, a local analog for green pea–type galaxies, with several enhancements, including a xenon-enhanced lithium fluoride + aluminum-coated grating, testing the leading flight coating for HWO for the first time. The INFUSE IFU is designed as a pathfinder for a potential IFU mode on HWO, enabling rapid 3D spectroscopy of extended sources.

The bright glow of geocoronal Lyman-alpha has long stymied astronomical observations within the Lyman ultraviolet (912 to 1215.67 Å). We explore the utility of a hydrogen absorption cell as a means of filtering out this geocoronal light, thus enabling Lyman ultraviolet observations in low Earth orbit. The hydrogen absorption cell is a chamber outfitted with LiF windows and filled with molecular hydrogen that is thermally dissociated into its neutral atomic form by a hot tungsten filament. We outline methodology and requirements for a wide-field high galactic latitude sounding rocket mission, using H-cell technology to directly detect the cosmic Lyman ultraviolet background underneath a Milky Way foreground of dust scattered starlight, molecular hydrogen emissions, and resolved stars. Such an instrument would be a pathfinder to a preparatory survey science mission for the Habitable Worlds Observatory to identify the most interesting Lyman ultraviolet objects for spectroscopic followup and deeply explore the Lyman ultraviolet background. The results herein have demonstrated close to 100% absorption of Lyα by an absorption cell attached to the entrance aperture of a low-resolution spectrograph (R≈103).

Recent studies have focused on the low-z Lyman alpha (Lyα) forest as a potential constraint on galactic feedback, as different active galactic nuclei (AGN) and stellar feedback models in hydrodynamic simulations produce varying intergalactic medium (IGM) statistics. However, existing low-z Lyα forest data provide insufficient observational constraints for simulations due to their low precision and the lack of observations from z∼0.4 to 1.8. The Habitable Worlds Observatory, equipped with an ultraviolet (FUV/NUV) spectrograph, could provide transformative data for this science by increasing both absorbers in the redshift range where current data are lacking and increasing the precision of the Lyα forest observational data at z≤0.4. This spectrograph should cover the wavelengths 1215 to 3402 Å and have a spectral resolution of R=40,000. Distinguishing between certain active-galactic nuclei feedback models requires high precision (∼5% to 10%) measurements of the Lyα forest 1D transmitted flux power spectrum for z≤1.8. This requires ∼830 QSO spectra with S/N≥5 to 25 depending on redshift. This data would also enable a comprehensive study on the thermal state of the IGM across time and address the tension between the observed and simulated Lyα forest b value distribution.

The National Aeronautics and Space Administration (NASA) Great Observatories Maturation Program is a development plan to efficiently and effectively develop large, strategic astrophysics missions. Suborbital rocket and balloon programs have long been a key development tool for enabling large missions in NASA astrophysics. We review the significance of these suborbital missions in the preceding decades to demonstrate their contributions to the Great Observatories Maturation Program for the Habitable Worlds Observatory and beyond. We show that suborbital instruments have obtained science observations of astrophysical sources across the electromagnetic spectrum, matured high-priority component technologies, and served as a training ground for principal investigators of explorer-class astrophysics satellites. A brief discussion of emerging CubeSat and SmallSat missions and their place in the NASA astrophysics portfolio is also provided.

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 Å; near-ultraviolet (NUV): 1800 to 2400 Å] and one optical band (u-band: 3000 to 4200 Å). 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 (10ドルM cost cap) and NASA Astrophysics Pioneers program (20ドルM cost cap).

The Quick Ultra-VIolet Kilonova surveyor (QUVIK), a two-band ultraviolet (UV) space telescope approved for funding as a Czech national science and technology mission, will focus on detecting early UV light of kilonovae (KNe) (Werner et al., 2024). In addition, it will study the UV emission of stars and systems (Krtička et al., 2024) as well as the intense and variable emission of active galactic nuclei (AGN) or galactic nuclei activated by tidal disruption events (TDEs) (Zajaček et al., 2024). In this contribution, we describe the role of this small (∼30-cm diameter) UV telescope for studying bright, nearby AGN. With its NUV and FUV bands, the telescope will perform high-cadence (∼0.1 to 1 day) two-band photometric monitoring of nearby AGN (z<1), which will allow us to probe accretion disk sizes/temperature profiles via photometric reverberation mapping. Thanks to its versatility, QUVIK will be able to perform a moderately fast repointing (<20min) to target candidates for TDEs. Early detection of the UV emission following a TDE optical flare, in combination with the subsequent two-band UV monitoring performed simultaneously with other observatories, will enable us to infer the time delay (or its lack of) between the optical, UV, and X-ray emission. In combination with theoretical models, it will be possible to shed more light on the origin of the UV/optical emission of TDEs. Furthermore, the two-band monitoring of nuclear transients will be beneficial in distinguishing between TDEs (nearly constant blue color) and supernovae (progressive reddening) in the era of intensive wide-field surveys.

Requirements for the direct detection of ionizing radiation escaping from galaxies by the Habitable Worlds Observatory are reviewed along with an outline of the sampling statistics required to create Lyman continuum (LyC) luminosity functions over the redshift interval from 0.2<z<1.2. The goal is to determine how the shape of the escaping LyC evolves with redshift and assess its impact on creating and sustaining the metagalactic ionizing background (MIB). A robust program that can deliver samples ∼500 objects per Δz=0.2 redshift interval and detect LyC escape fractions f900e<1% for sub-L900(1+z)* galaxies requires a spectral multiplexing capability with sensitivity to ≳30 abmag. A short wavelength cutoff of ∼1000Å will allow the first measurements of the LyC spectral energy distribution down to a rest frame cutoff from 830≲λcutoffLyC≲450Å over the proposed redshift interval, allowing for a more complete assessment of the ionizing radiation escaping into the MIB.

In the context of the development of several space mission projects for ultraviolet (UV) spectropolarimetry at high resolution and over a wide UV wavelength range, such as Arago, Polstar, and Pollux onboard the Habitable Worlds Observatory, we are studying and developing the UV nanosatellite CubesAt Spectropolarimeter Scientific and Technological demonstratOR (CASSTOR) to obtain the very first UV spectropolarimetric observations of hot stars and test several new technologies, in particular a UV polarimeter and a fine guiding system. In this paper, we present the work and outcome of the phase 0 study of CASSTOR.

We detail recent and current work that is being carried out to fabricate and advance novel SiC UV instrumentation that is aimed at enabling more sensitive measurements across numerous disciplines, with a short discussion of the promise such detectors may hold for the Habitable Worlds Observatory. We discuss SiC instrument development progress that is being carried out under multiple NASA grants, including several PICASSO and SBIR grants, as well as an ECI grant. Testing of pixel design, properties, and layout as well as maturation of the integration scheme developed through these efforts provides key technology and engineering advancement for potential HWO detectors. Achieving desired noise characteristics, responsivity, and validating the operation of SiC detectors using standard readout techniques offers a compelling platform for the operation of denser and higher dimensionality SiC photodiode arrays of interest for use in potential HWO coronagraph, spectrograph, and high-resolution imaging instruments. We incorporate these SiC detector properties into a simulation of potential NUV exoplanet observations by HWO and also discuss potential applications to HWO.

The energy generated by the accretion disks (ADs) around supermassive black holes (SMBHs) at the centers of galaxies plays a critical role in the evolution of their host galaxy. Recent studies have shown that theoretical models for AD sizes do not match indirect observations of disks. Unfortunately, direct observation of AD around SMBHs is not possible, but we can exchange time resolution for spatial resolution to study the radius-to-temperature relation for these disks and derive their true sizes. Reverberation mapping (RM) provides the best close-in probe of the structure of the SMBH environment. RM measures the time delay among fluctuations in the short wavelength continuum arising from close to the SMBH (likely from its corona) and the subsequent longer wavelength response of the AD continuum and gas in the broad line region (BLR). However, RM is a telescope-intensive process requiring regular observations over a long period, but due to the scarcity of observing time on ultraviolet (UV)-capable facilities, very few active galactic nuclei (AGNs) have had this type of intensive multiwavelength monitoring. To solve this problem, we have proposed a space mission dedicated to AGN RM: the Black Hole Accretion and Growth Experiment with Reverberation Analysis, which is equipped with a 20-cm telescope coupled to a far UV/optical (1400 to 6000 Å) low-resolution spectrograph. By monitoring changes from the far UV to the optical, we trace the changes from close to the SMBH all the way out to the optical emitting region, and we can distinguish between continuum emission from the disk and continuum emission from elsewhere (e.g., potentially from the BLR). By observing 10 nearby AGNs, we can sample the diversity of AGN AD properties over a range of SMBH masses and accretion rates to gain insight into the fundamental physics of accretion disks and how they ultimately connect to their host galaxies.

High-resolution, ultraviolet imaging is often unavailable across the sky, even in heavily studied fields such as the Chandra Deep Field - South. The Habitable Worlds Observatory is one of two upcoming missions with the possibility of significant ultraviolet (UV) capabilities and the only one early enough in development to consider suggestions to its design. We conduct an initial study of how current common UV filter sets affect the results of spectral energy distribution fitting for the estimation of galaxy parameters. This initial look is intended to motivate the need for future, more robust spectral energy distribution fitting of mock galaxies. We compare the broad near UV and far UV filters used by the GALEX mission to the three narrower Swift Ultraviolet Optical Telescope (UVOT) filters. We find that the GALEX filters result in larger errors when calculating the UV β parameter compared with UVOT and provide little constraint on the star formation age of a galaxy. We further note the ability of the UVOT filters to investigate the 2175-Å attenuation bump; GALEX has a reduced capacity to trace this same feature. Ultimately, we recommend that to optimize the effectiveness of Habitable Worlds Observatory’s ultraviolet capacity for transformative astrophysics, a minimum of a Far-UV (FUV) filter with three medium band Near-UV (NUV) filters should be adopted. This will combine the power of GALEX’s wavelength range with the finer sampling of UVOT around an important dust feature.

The Roman Space Telescope Wide Field Instrument (WFI) will enable revolutionary advancements in astronomical survey science. Instrument sensitivity spans the 0.5 to 2.3μm spectral range with a significant increase in field of view, detector sensitivity, and angular resolution compared with existing observatories. The science of the observatory drove tight stability requirements and necessitated an array of different optical elements within WFI to switch between imaging at different wavelengths, using two slitless spectroscopic elements. The science also drove the need for an uncommonly high level of detector calibration, requiring an on-board calibration system supported by unique optics, as well as precise stray light mitigation. WFI has recently completed its year-long integration and test campaign as a full instrument, including multiple environmental tests, enabling its performance to be studied in operational temperature conditions. This publication summarizes several key optical performance aspects of the instrument, including bandpass filter wavefront error, stray light control, and optomechanical alignment. The results demonstrate that the WFI is ready to help transform astrophysics as part of the next NASA flagship observatory.

HiZ-GUNDAM is a candidate for JAXA’s competitive medium-class mission program, with its concept approved by ISAS/JAXA in 2018. This proposed satellite aims to play a leading role in time-domain astronomy in the 2030s by pursuing two primary scientific goals: (1) probing the early universe through the detection of high-redshift gamma-ray bursts (GRBs) and (2) enabling the rapid identification of X-ray and optical-near-infrared counterparts of multimessenger sources. To achieve these objectives, HiZ-GUNDAM is equipped with two key instruments. A wide-field X-ray monitor, EAGLE, utilizes a micropore optics array and a focal plane imaging sensor to observe transients across ∼0.5sr in the 0.4 to 4 keV energy range. To follow up on this observation, an optical–near-infrared telescope, MONSTER, features a 30 cm aperture and conducts simultaneous five-band photometry over the 0.5 to 2.5μm wavelength range. It employs a Kösters-type prism for multi-band photometry to follow up on transients detected by the EAGLE. A sun-synchronous dawn–dusk orbit has been selected to ensure thermal stability for the MONSTER. We present a comprehensive overview of the HiZ-GUNDAM mission concept. The mission is expected to make a significant contribution to our understanding of cosmic evolution through observations of high-redshift GRBs, as well as to the identification of the multiwavelength properties of multimessenger sources by enhancing the observational capabilities for transient searches. The specifications and concepts discussed herein are subject to refinement as the mission progresses.

Supernovae (SNe) enrich and energize the surrounding interstellar medium (ISM) and are a key mechanism in the galaxy feedback cycle. The heating of the ISM by supernova shocks and its subsequent cooling is of critical importance to future star formation. The cooling of the diffuse shock-heated ISM is dominated by ultraviolet (UV) emission lines. These cooling regions and interfaces have complex spatial structure on sub-parsec scales. Mapping this cooling process is an essential part of understanding the feedback cycle of galaxies, a major goal of the 2020 Astrophysics Decadal Survey. The Supernova remnants and Proxies for ReIonization Testbed Experiment (SPRITE) 12U CubeSat Mission will house the first long-slit orbital spectrograph with sub-arcminute angular resolution covering far ultraviolet wavelengths (FUV; 1000 to 1750 Å) and access to the Lyman UV (λ<1216Å). SPRITE is designed to provide new insights into the stellar feedback that drives galaxy evolution by mapping key FUV emission lines at the interaction lines between supernova remnants (SNRs) and the ambient ISM. SPRITE will also measure the ionizing escape from ∼50 low-redshift (0.16<z<0.4) star-forming galaxies. Current models predict SPRITE capable of detecting strong O VI, O IV], and C IV emission lines with angular resolution from 10 to 20 arcseconds. The SPRITE SNR survey will use push-broom mapping of its long-slit on extended sources to produce the first large sample of sub-arcminute 3D data cubes of extended sources in the FUV. We present simulated SPRITE observations of Large Magellanic Cloud (LMC) SNRs to demonstrate the efficacy of the SPRITE instrument ahead of launch and instrument commissioning. These models serve as critical planning tools and incorporate the final pre-flight predicted performance of the instrument and the early extended source data reduction pipeline.

Far ultraviolet (FUV)and Lyman ultraviolet (LUV) imaging is necessary to address a wide breadth of high-profile science topics that range from characterizing the rest frame Lyman continuum of low-redshift galaxies, to mapping the circumgalactic medium, and expanding our understanding of how stellar feedback shapes the chemical and kinematic morphology of galaxies. We present laboratory reflectivity results of two recently developed reflectance filters designed for LUV (950 to 1150 Å) and FUV (1300 to 1900 Å) bandpasses, respectively. These filters will be implemented on a sounding rocket instrument, the Far- and Lyman-ultraviolet imaging demonstrator (FLUID). We also present the results of work to address environmental stability challenges of the FLUID optical coatings as some prescriptions can be sensitive to relative humidity (RH) during pre-deployment installation. Finally, we present spectroscopic and imaging simulations of one of the proposed FLUID targets, NGC 4449. These simulations use theoretical filter performance and laboratory reflectivity results to predict the observed in-flight data from FLUID.

We present here the design and development of the Cassegrain Module for the PARAS-2 spectrograph (CAMPAS). PARAS-2 is a high-resolution fiber-fed echelle spectrograph developed for the PRL 2.5 m telescope. The CAMPAS acts as a coupler between two optical systems, the PRL 2.5 m telescope and the PARAS-2 spectrograph. It has primarily been developed for the precise injection of the light beam into the optical fibers of the PARAS-2 spectrograph. The CAMPAS consists of a focal reducer, beam-guiding optics, an atmospheric dispersion corrector, optical fiber mounts, a calibration unit incorporating calibration lamps and beam-guiding optics, and other auxiliary subsystems. It was developed in-house at PRL, Ahmedabad, between the years 2020 and 2022 and was installed at one of the two side ports of the PRL 2.5 m telescope in March 2022. It is one of the first light instruments for the PRL 2.5 m telescope. The CAMPAS serves critical purposes of precise fiber feed, point spread function estimation, and atmospheric dispersion correction.