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 similar to 103 nm. 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.
In carbon nanotube thin film transistors (CNT-TFTs), the performance is significantly influenced by the fluctuation in the diameter of the CNTs in channel. In this work, first-principles calculations were employed to explore the fluctuations in the valence band maximum and conduction band minimum of CNTs with diameters ranging from 0.78 to 2.07 nm. Band alignment analysis reveals maximum offsets reach 0.54 eV for the valence band and 0.48 eV for the conduction band, with larger CNTs (diameters over 1.8 nm) exhibiting energy band fluctuations of less than 0.06 eV. Further analysis shows that the fluctuation in Schottky barrier height (SBH) is smaller between CNTs and Pd compared to CNTs and Ti. Atomistic simulations of Pd-CNT-Pd devices at -2 V demonstrate that the variation in on-state current between 1.49 and 2.04 nm CNTs is six times smaller than that between 1.02 and 1.49 nm CNTs. This indicates that inter-nanotube fluctuations in larger-diameter CNTs have a smaller impact on device current compared to fluctuations in smaller-diameter CNTs. These findings suggest that larger-diameter CNTs (greater than 1.8 nm) enhance the uniformity of electrical properties, presenting a promising approach to improving the reliability of CNT-based thin-film devices.
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.
Distributed Acoustic Sensing (DAS) is a rapidly developing technology that has already been successfully applied to solve various problems in geology, geophysics, and geoecology. Its advantages include unprecedentedly high spatial resolution, covering areas of up to a hundred kilometers or more; high sensitivity; and a broad frequency range. High-quality ice cover monitoring requires a dense network of seismic sensors. DAS can serve as an excellent complement to observation networks based on traditional seismic instruments. An expensive interrogator remains in a safe location (e.g., onshore), while the optical fiber can be considered expendable. In this article, we discuss the current state of the problem, describe our experiment conducted in February 2024 on the ice of the Klyazma reservoir, and share some conclusions and recommendations.
Aspera is the UV small-satellite mission to detect and map the warm-hot phase gas in nearby galaxy halo. Aspera was chosen as one of NASA's Astrophysics Pioneers missions in 2021 and employs a FUV long-slit spectrograph payload, optimized for low-surface brightness O VI emission line detection at 103-104 nm. The mission incorporates state-of-the-art UV technologies such as high-efficiency micro-channel plates and enhanced LiF coating to achieve a high level of diffuse-source sensitivity of the payload, down to 5.0E-19 erg/s/cm^2/arcsec^2. The combination of the high sensitivity and a 1-degree by 30-arcsecond long-slit field of view enables efficient 2D mapping of diffuse halo gas through step and stare concept observation. Aspera is presently in the critical design phase, with an expected launch date in mid-2025. This work provides a current overview of the Aspera payload design.
