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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The Free-Flying Magnetometer (FFM) is an autonomous spin-stabilized sensorcraft developed at the Jet Propulsion Laboratory (JPL) for the Enstrophy sounding rocket mission.
The first Danish satellite, إrsted, will be launched in August of 1997. The scientific objective of إrsted is to perform a precision mapping of the Earth's magnetic field. Attitude data for the payload and the satellite are provided by the Advanced Stellar Compass (ASC) star tracker. The ASC consists of a CCD star camera and a capable microprocessor which operates by comparing the star image frames taken by the camera to its internal star catalogs.
The paper summarizes efforts at JPL to develop an intelligent autonomous tracking and pointing system for space applications. A powerful 3D graphic software testbed has also been developed to simulate a likely scenario of autonomous tracking and pointing operations during a planetary flyby.
A quasi-inertial reference frame is defined based on the radio positions of 212 extragalactic sources distributed over the entire sky.
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In this paper, we identify the broad range of challenges associated with creating an augmented reality for future spaceflight missions. The challenges were framed within a sociotechnical framework to explore how an imagined augmented reality system might one day help crew cope with future exploration mission demands. Key challenges include an augmented reality system cannot simply be designed to help a single suited astronaut and must enable the broader mission team. There exists a host of optical, compute, and control technical challenges that must be simultaneously addressed while the work domain itself is in development. There exist limited methods to help cope with the envisioned world problem; however, we emphasize a few strategies to articulate work design assumptions and host this detail in a transparent fashion. Finally, we note the broader organizational constraints that shape the creation of such novel technology for spaceflight. By addressing these broad range of challenges directly, early in the design and development process, key trade-offs can be considered and fundamental concerns within the community can be addressed to yield desired mission outcomes.
The task of quantifying spatial and temporal variations in terrestrial water, energy, and vegetation conditions is challenging due to the significant complexity and heterogeneity of these conditions, all of which are impacted by climate change and anthropogenic activities. To address this challenge, Earth Observations (EOs) of the land and their utilization within data assimilation (DA) systems are vital. Satellite EOs are particularly relevant, as they offer quasi-global coverage, are non-intrusive, and provide uniformity, rapid measurements, and continuity. The past three decades have seen unprecedented growth in the number and variety of land remote sensing technologies launched by space agencies and commercial companies around the world. There have also been significant developments in land modeling and DA systems to provide tools that can exploit these measurements. Despite these advances, several important gaps remain in current land DA research and applications. This paper discusses these gaps, particularly in the context of using DA to improve model states for short-term numerical weather and sub-seasonal to seasonal predictions. We outline an agenda for land DA priorities so that the next generation of land DA systems will be better poised to take advantage of the significant current and anticipated shifts and advancements in remote sensing, modeling, computational technologies, and hardware resources.
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Pure Aluminum (Al) exhibits intrinsic high reflectance over the proposed Large UV/Optical/IR (LUVOIR) Surveyor observatory target spectral range (90-2500 nm). However, Al coatings have to be protected from oxygen exposure in order to prevent the formation of the naturally occurring Al2O3 oxide layer, which limit performance for use only above 160 nm. Aluminum protected with fluorides such as LiF or MgF2 have been the most commonly used solutions. But below 102 nm and down to 90 nm, no transparent material is available to protect Al and coating mirror reflectance stays below 40%. But even above 102 nm, the reflectance of protected Al is limited by the residual absorption of the fluoride overcoats. Hence, this paper will report on recent advances in producing enhanced Al-based mirror coatings with the highest possible far-ultraviolet (FUV) reflectance, while exhibiting a more stable LiF protection layer. The process starts with a bare optically smooth glass substrate that is coated with Al in an ultra-high vacuum chamber by using the physical vapor deposition (PVD) process, which has been shown to provide the best aluminum thin-films when compared to other approaches. The next step is done by in-situ exposure of the freshly made Al film to a reactive XeF2 gas that will grant a thin AlF3 overcoat (2-3 nm) to the Al film that prevents further oxidation. This fluorinated Al film is then coated with a final layer of a LiF metal-fluoride overcoat. The coating process is finalized with a second exposure to the XeF2 precursor gas. The preparation of these mirror coatings will be studied and analyzed as a function of the XeF2 exposure time and deposition rate of the LiF layer during the PVD process. This paper will present and discuss characterization of a number of Al+XeLiF witness coupons produced with this reactive PVD (rPVD) process. These studies include characterization of specular reflectance in the 90-2500 nm spectral range, micro-roughness, long-term stability, as well as polarization characteristics in the visible and near-infrared spectral regions. These studies have been performed in order to demonstrate the improved reflectance performance, longer durability, and less hygroscopic nature of protected Al mirrors produced with the rPVD process (through exposure to XeF2) and in comparison with the standard PVD process.
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This paper presents results from metal contact processing experiments towards the implementationof durable 500 deg.C high-frequency 4H-SiC bipolar junction transistors (BJTs). Specifically, p-type ohmic contacts have been demonstrated on a 0.25 μm-thick p-type homoepitaxial layer of doping 8 x 1018± 4 x 1018cm-3. Finally, preliminary current-voltage characteristics of fabricated BJTs are presented.