Feedback from massive stars through their host galaxies is a crucial driver of galaxy evolution, energizing and enriching the interstellar medium (ISM) and circumgalactic medium (CGM). Massive stars also emit ionizing radiation, a fraction of which escapes into the intergalactic medium. The Supernova Remnants and Proxies for Reionization Testbed Experiment (SPRITE) is a 12U CubeSat that will observe these processes in the far-ultraviolet in local galaxies through two independent but related science surveys. SPRITE is the first independent far-UV orbital spectroscopic mission in over 20 years, and the first orbital instrument capable of sub-arcminute imaging spectroscopy in the Lyman ultraviolet (91 < λ < 120 nm). We present the results of ground testing of the SPRITE flight instrument and characterize its projected on-orbit performance. We also demonstrate the capabilities of SPRITE’s unique technological developments, including advanced UV optical coatings and a low-background microchannel plate detector, providing flight heritage for Habitable Worlds Observatory (HWO) and other future missions.
SPRITE (Supernova Remnants and Proxies for Reionization Testbed Experiment) is a 12U CubeSat mission funded by NASA and led by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder. The payload will house the first sub-arcminute resolution Far-Ultraviolet (FUV) long-slit spectrograph with access to the Lyman UV (912 − 1216 Å), enabled by new enhanced lithium fluoride coatings and an ultra-low-noise photon-counting microchannel plate (MCP) detector. The scientific mission has two main components: constraining the escape fraction of ionizing Lyman-Continuum (LyC) radiation from low-redshift galaxies (0.14 ≤ z ≤ 0.4) and measuring feedback from nearby star forming regions and supernova remnants. Enabling the scientific mission are two distinct observing modes. For the faintest sources, we will operate the MCP detector in photon-counting mode. For brighter sources, we will operate the MCP in an accumulation / integration mode. For extended sources we will collate multiple pointings of the long slit, stepping across the field of view in a ‘push broom’ mapping to create 3D spectroscopic cubes. SPRITE will also take weekly calibration data to characterize the degradation of the coatings and detector. We present these observing modes along with the data acquisition and processing pipeline required to enable scientific analysis on the ground.
Aspera is a NASA-funded UV SmallSat mission designed to detect and map warm-hot phase halo gas around nearby galaxies. The Aspera payload is designed to detect faint diffuse O VI emission at around 103.2 nm, satisfying the sensitivity requirement of 5×10−19 erg/s/cm2/arcsec2 over 179 hours of exposure. In this manuscript, we describe the overall payload design of Aspera. The payload comprises two identical co-aligned UV long-slit spectrograph optical channels sharing a common UV-sensitive microchannel plate detector. The design delivers spectral resolution R ∼ 2,000 over the wavelength range of 101 to 106 nm. The field of view of each channel is 1 degree by 30 arcsec, with an effective area of 1.1 cm2. The mission is now entering the payload integration and testing phase, with the projected launch-ready date set for late 2025 or early 2026. The mission will be launched into low-Earth orbit via rideshare.
The Integral Field Ultraviolet Spectroscopic Experiment sounding rocket is the first far ultraviolet integral field spectrometer. It features an f /16, 0.49 m Cassegrain telescope and a 26-element image slicer feeding 26 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 29th, 2023, and demonstrated spectral multiplexing, successfully detecting ionized gas emission in the XA region of the Cygnus loop. The second launch of INFUSE is projected for spring 2025 to observe the star-forming galaxy NGC 2366 alongside companion NGC 2363. Housed within NGC 2366 is the Mrk 71 region, a prototype for studying highly ionized starburst regions, making NGC 2366 a local analog to Green Pea type galaxies. Several enhancements are planned for INFUSE before this second science flight, including adding an improved baffle to reduce contamination by second order light, improving grating alignment to reduce overlap between different spectrograms, and iriditing several surfaces to reduce scattered geocoronal Ly-α. An additional grating coated with xenon diflouride-enhanced lithium fluoride will also be added to flight qualify a new coating that may support ultraviolet capability on the Habitable Worlds Observatory. The second flight will also feature a ride along mission, the Spectroscopic Ultraviolet Multi-Object Observatory. We report on the results from the first launch as well as outline progress towards preparation for the second flight.
The SPRITE (The Supernova remnants, Proxies for Re-Ionization Testbed Experiment) 12U CubeSat mission, funded by NASA and led by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder, will house the first Far-UV (100-175 nm) long-slit spectrograph with access to the Lyman UV (λ ⪅ 115 nm) and sub-arcminute imaging resolution. SPRITE will map the high energy emission from diffuse gas allowing for the study of star formation feedback in a critical, but rarely studied, Far-UV regime on both stellar and galactic scales. This novel capability is enabled by new UV technologies incorporated into SPRITE’s design. These technologies include more robust, high broadband reflectivity mirror coatings and an ultra-low background photon counting microchannel plate detector. The SPRITE science mission includes weekly calibration observations to characterize the performance of these key UV technologies over time, increasing their technology readiness level (TRL) to 7+ and providing flight heritage essential for future UV flagship space missions such as the Habitable Worlds Observatory (HWO). Currently, SPRITE is in the beginning stages of integration and testing of its flight assembly with a planned delivery date of fall of 2024. This proceeding will overview the current mission status, the schedule for testing and integration prior to launch, and the planned mission operations for SPRITE.
The Europa Clipper Ultraviolet Spectrograph (Europa-UVS) is the sixth in the line of Alice/UVS spectrographs from Southwest Research Institute (SwRI). The heart of the instrument is a far-UV sensitive microchannel plate detector system. This detector consists of a z-stack of three borosilicate glass microchannel plates, with resistive and secondary emissive layers deposited via an atomic-layer deposition (ALD) process. The resulting detector has orders of magnitude longer lifetime given comparable fluences than previously flown MCP detectors, as well as reduced sensitivity to gamma-ray induced background noise. This detector is also the first instance of a curved borosilicate glass microchannel plate z-stack undergoing thermal vacuum testing in a flight-like environment, raising the TRL of the system to 6. The flight model detector was bench tested at Sensor Sciences and delivered to the Europa-UVS project in July 2020. Further bench tests were undertaken at SwRI after delivery, followed by thermal vacuum testing in December 2020. The results of these tests are presented herein.
We present the performance of a 200mm × 200mm microchannel plate detector during two suborbital flights in 2017 and 2018. The detector utilized ALD boro-silicate plates and a cross delay line readout. Background counts inflight were between 1.43 count/cm2/s. The quantum efficiency after two years and two flights was consistent with preflight measurements.
The JUICE (JUpiter ICy moons Explorer) Ultraviolet Spectrograph (JUICE-UVS) is the fifth in the line of Alice/UVS spectrographs from Southwest Research Institute (SwRI). The heart of the instrument is a far-UV sensitive microchannel plate detector system. This detector includes an atomic-layer deposition (ALD) coating on the bottom plate to minimize gain sag, resulting in a detector with orders of magnitude longer lifetime given comparable fluences than previously flown MCP detectors. This detector is also the first instance of a curved microchannel plate z-stack receiving an ALD coating to minimize gain sag. The detector electronics have also been improved over previous generations to preserve pulse height integrity at the high (i.e. 100 kHz) count rates expected during operation in the Jupiter system. The flight model detector was bench tested at Sensor Sciences and delivered to the JUICE-UVS project in August 2018. Further bench tests were undertaken at SwRI after delivery, followed by thermal vacuum testing in October 2018. The results of these tests are presented herein.
The Johns Hopkins University sounding rocket group has completed the assembly and calibration of the Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS); a sounding rocket borne multi-object spectro-telescope designed to provide spectral coverage of up to 43 separate targets in the 900 - 1800 Angstrom bandpass over a 30′ x 30′ field-of-view. FORTIS is capable of selecting the far-UV brightest regions of the target area by utilizing an autonomous targeting system. Medium resolution (R ~ 400) spectra are recorded in redundant dual-order spectroscopic channels with ~40 cm2 of effective area at 1216 Å. The maiden launch of FORTIS occurred on May 10, 2013 out of the White Sands Missile Range, targeting the extended spiral galaxy M61 and nearby companion NGC 4301. We report on the final flight calibrations of the instrument, as well as the flight results.
The Johns Hopkins University sounding rocket group is entering the final fabrication phase of the Far-ultraviolet Off
Rowland-circle Telescope for Imaging and Spectroscopy (FORTIS); a sounding rocket borne multi-object spectro-telescope
designed to provide spectral coverage of 43 separate targets in the 900 - 1800 Angstrom bandpass over a 30' x 30' field-of-
view. Using "on-the-fly" target acquisition and spectral multiplexing enabled by a GSFC microshutter array, FORTIS
will be capable of observing the brightest regions in the far-UV of nearby low redshift (z ~ 0.002 - 0.02) star forming
galaxies to search for Lyman alpha escape, and to measure the local gas-to-dust ratio. A large area (~ 45 mm x 170 mm)
microchannel plate detector built by Sensor Sciences provides an imaging channel for targeting flanked by two redundant
spectral outrigger channels. The grating is ruled directly onto the secondary mirror to increase efficiency. In this paper, we
discuss the recent progress made in the development and fabrication of FORTIS, as well as the results of early calibration
and characterization of our hardware, including mirror/grating measurements, detector performance, and early operational
tests of the microshutter arrays.
The nitride-III semiconductors, in particular GaN (band gap energy 3.5 eV), AlN (band gap 6.2 eV) and their alloys AlxGa1-xN are attractive as UV photo-convertors with applications as photocathodes for position sensitive detector systems. These can “fill the gap” in the 150-400nm wavelength regime between alkali halide photocathodes (<2000Å), and the various optical photocathodes (>4000Å, mutlialkali & GaAs). Currently CsTe photocathodes have fairly low efficiency (Fig. 1) in the 100nm to 300nm regime are sensitive to contamination and have no tolerance to gas exposure. We have prepared and measured a number of GaN photocathodes in opaque and semitransparent modes, achieving >50% quantum efficiency in opaque mode and ~35% in semitransparent mode (Fig. 2). The GaN photocathodes are stable over periods of >1 year and are robust enough to be re-activated many times. The cutoff wavelength is sharp, with a rapid decline in quantum efficiency at ~380-400nm. Application of GaN photocathodes in imaging devices should be feasible in the near future. Further performance improvements are also expected as GaN fabrication and processing techniques are refined.
We present the preliminary calibration results for the Cosmic Origins Spectrograph, a fourth generation replacement instrument for the Hubble Space Telescope due to be installed in mid-2005. The Cosmic Origins Spectrograph consists of two spectroscopic channels: a far ultraviolet channel that observes wavelengths between 1150 and 2000 Åand a near ultraviolet channel that observes between 1700 and 3200 Å. Each channel supports moderate (R≈20,000) and low (R≈2000) spectral resolution. We discuss the calibration methodology, test configurations, and preliminary end-to-end calibration results. This includes spectral resolution, system efficiency, flat fields, and wavelength scales for each channel. We also present the measured transmission of the Bright Object Aperture (BOA) and the measured spatial resolution.
The flight microchannel plate detectors to be used in the Cosmic Origins Spectrograph, a fourth generation instrument for the Hubble Space Telescope, have been calibrated in the laboratory before being integrated into the spectrograph. This paper presents additional findings following a second scrub that became necessary when a fault was found with the quantum efficiency enhancement grid.
The flight microchannel plate detectors to be used in the Cosmic Origins Spectrograph, a fourth generation instrument for the Hubble Space Telescope, have been calibrated in the laboratory before being integrated into the spectrograph. This paper presents the results of these calibrations that include measurements of the detector quantum efficiency, spatial resolution, spatial linearity, flat field, electronic livetime and the local count rate limit.
We report on the performance of 6 micrometer pore diameter Microchannel Plates (MCPs) fabricated in 50 X 50 mm2 format, from both standard and radio-isotope free low noise glass, by Photonis SAS for a European Space Agency Technology Research Program. We compare them to MCPs manufactured by Photonis (the former Philips Photonics) for the High Resolution Camera (HRC) on NASA's Chandra X-ray observatory. The new MCPs represent a significant advance in MCP technology, having a much larger area than previously reported 6 micrometer plates, and demonstrating low noise 6 micrometer technology for the first time. The 6 micrometer plates are shown to be, mechanically, exceptionally well made with a defect density reduced by a factor of 2 - 5 compared to samples from the HRC flight blocks. They exhibit excellent gain and the expected 0.28 keV (Carbon K) X-ray quantum efficiency. The low noise plates have a very uniform response to X-rays but the standard glass MCPs do show inhomogeneity on both the global and multifiber scales.
Lobster-eye optics have been proposed as an exciting development in the field of x-ray all-sky monitors. However, to date their potential has mainly been analyzed in the context of an all-sky monitor for a small satellite mission. We examine the wide range of parameters available for lobster-eye optics with different configurations. The sensitivity of the various schemes is calculated. We have also examined the current state of the art in actual lobster-eye optics. We present our experimental results and discuss realistic targets for manufacture. The impact of these targets on the calculated sensitivities is also described.
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