Strong whistler mode waves observed in the vicinity of Jupiter’s moons
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Y. Y. Shprits↗
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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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Observation of mode locking and ultrashort optical pulses induced by anisotropic molecular liquids.
Mode locking and ultrashort pulses in giant pulses in giant pulse ruby laser with heated nitrobenzene or alpha-chloronaphthalene in resonator
Comly, J.↗
A bimodal search strategy for SETI
A SETI plan has been developed jointly by the NASA Ames Research Center and the Jet Propulsion Laboratory with the objective of both observing all potential sites to some limiting equivalent isotropic radiated power and surveying with greater sensitivity a set of especially promising sites. The bimodal search strategy assumes that existing radio telescopes with state-of-the-art receivers and data processing devices will have the sensitivity to explore the vicinity of nearby stars for similar transmitters and the entire galaxy for more powerful signals. The discrete source observational mode is designed to observe 773 F, G and K-type stars within 25 pc of the sun at frequencies from 1.2 to 3 GHz and spot bands between 3 and 25 GHz with sensitivities from 10 to the -25th to 10 to the -27th W/sq m. The sky survey is intended to search the entire celestial sphere between 1.2 and 10 GHz and spot bands between 10 and 25 GHz at a sensitivity limit of approximately 10 to the -23rd times the square root of the frequency. Instrumentation for the surveys includes a large multichannel spectrum analyzer. Immediate goals of the program are the investigation of the RF background at high resolution and the development of signal detection algorithms, with operation to begin in 1984.
Gulkis, S.↗
Proceedings of the 20th International Symposium on Space Flight Dynamics
Topics include: Measuring Image Navigation and Registration Performance at the 3-Sigma Level Using Platinum Quality Landmarks; Flight Dynamics Performances of the MetOp A Satellite during the First Months of Operations; Visual Navigation - SARE Mission; Determining a Method of Enabling and Disabling the Integral Torque in the SDO Science and Inertial Mode Controllers; Guaranteeing Pointing Performance of the SDO Sun-Pointing Controllers in Light of Nonlinear Effects; SDO Delta H Mode Design and Analysis; Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter; Broken-Plane Maneuver Applications for Earth to Mars Trajectories; ExoMars Mission Analysis and Design - Launch, Cruise and Arrival Analyses; Mars Reconnaissance Orbiter Aerobraking Daily Operations and Collision Avoidance; Mars Reconnaissance Orbiter Interplanetary Cruise Navigation; Motion Parameters Determination of the SC and Phobos in the Project Phobos-Grunt; GRAS NRT Precise Orbit Determination: Operational Experience; Orbit Determination of LEO Satellites for a Single Pass through a Radar: Comparison of Methods; Orbit Determination System for Low Earth Orbit Satellites; Precise Orbit Determination for ALOS; Anti-Collision Function Design and Performances of the CNES Formation Flying Experiment on the PRISMA Mission; CNES Approaching Guidance Experiment within FFIORD; Maneuver Recovery Analysis for the Magnetospheric Multiscale Mission; SIMBOL-X: A Formation Flying Mission on HEO for Exploring the Universe; Spaceborne Autonomous and Ground Based Relative Orbit Control for the TerraSAR-X/TanDEM-X Formation; First In-Orbit Experience of TerraSAR-X Flight Dynamics Operations; Automated Target Planning for FUSE Using the SOVA Algorithm; Space Technology 5 Post-Launch Ground Attitude Estimation Experience; Standardizing Navigation Data: A Status Update; and A Study into the Method of Precise Orbit Determination of a HEO Orbiter by GPS and Accelerometer.
Woodard, Mark↗
Real-Time Exposure Control and Instrument Operation With the NEID Spectrograph GUI
The NEID spectrograph on the WIYN 3.5-m telescope at Kitt Peak has completed its first full year of science operations and is reliably delivering sub-m/s precision radial velocity measurements. The NEID instrument control system uses the TIMS package (Bender et al. 2016), which is a client-server software system built around the twisted python software stack. During science observations, interaction with the NEID spectrograph is handled through a pair of graphical user interfaces (GUIs), written in PyQT, which wrap the underlying instrument control software and provide straightforward and reliable access to the instrument. Here, we detail the design of these interfaces and present an overview of their use for NEID operations. Observers can use the NEID GUIs to set the exposure time, signal-to-noise ratio (SNR) threshold, and other relevant parameters for observations, configure the calibration bench and observing mode, track or edit observation metadata, and monitor the current state of the instrument. These GUIs facilitate automatic spectrograph configuration and target ingestion from the nightly observing queue, which improves operational efficiency and consistency across epochs. By interfacing with the NEID exposure meter, the GUIs also allow observers to monitor the progress of individual exposures and trigger the shutter on user-defined SNR thresholds. In addition, inset plots of the instantaneous and cumulative exposure meter counts as each observation progresses allow for rapid diagnosis of changing observing conditions as well as guiding failure and other emergent issues.
Arvind F Gupta↗
Chapter 3: Photovoltaic Module Stability and Reliability
Profits realized from investment in photovoltaic will benefit from decades of reliable operation. Service life prediction through accelerated tests is only possible if indoor tests duplicate power loss and failure modes observed in fielded systems. Therefore, detailing and quantifying power loss and failure modes is imperative. In the first section, we examine recent trends in degradation rates, the gradual power loss observed for different technologies, climates and other significant factors. In the second section, we provide a summary of the most commonly observed failure modes in fielded systems.
14 SOLAR ENERGY↗
Orbit-following simulations of fast-ion transport and losses due to the Alfvén eigenmode burst in the Large Helical Device
Orbit-following simulations of fast-ion transport and losses with time-dependent electromagnetic perturbations are performed to clarify the roles of Alfvén eigenmodes (AEs) and the low-frequency magnetohydrodynamic (MHD) mode observed in the kinetic-MHD hybrid simulation of AE bursts in the Large Helical Device. Fast-ion pressure profile flattening in the kinetic-MHD hybrid simulation can be reproduced by an orbit-following simulation with only the primary single AE of the time-dependent amplitude following the kinetic-MHD hybrid simulation result, while orbit-following simulations with constant AE amplitude of average level during AE burst cannot reproduce the fast-ion pressure profile flattening observed. The effects of other modes are negligible on the fast-ion pressure profile flattening. The fast-ion losses in kinetic-MHD hybrid simulation can be reproduced by an orbit-following simulation with time-dependent amplitude when the low-frequency MHD mode is considered in addition to multiple AEs. This indicates the synergetic effect of multiple AEs and the low-frequency MHD mode on fast-ion losses.
Seki, Ryohsuke↗
On the mean particle size and water content of polar mesospheric clouds
Results from the ultraviolet spectrometer experiment (UVS) aboard the Solar Mesospheric Explorer, which measures ultraviolet sunlight scattered from air molecules in the mesosphere, are reported and discussed. The UVS experiment, its observing modes, and details of the observing sequence are described. The data are compared with predictions of Mie scattering theory, assuming the size distribution is parameterized by a mean radius and a width parameter. The water ice content, mean particle radius, and column number are calculated as a function of cloud brightness, and in terms of the unknown width parameter. It is concluded that polar mesospheric cloud particles are quite small, having average volume-effective radii less than 70 mm, and that clouds differ in their optical properties mainly as a result of their mean particle size.
Thomas, G. E.↗
Experiments on excitation of Alfvén eigenmodes by alpha-particles with bump-on-tail distribution in JET DTE2 plasmas
Dedicated experiments were performed in JET DTE2 plasmas for obtaining an α-particle bump-on-tail (BOT) distribution aiming at exciting Alfvén eigenmodes (AEs). Neutral beam injection-only heating with modulated power was used so that fusion-born α-particles were the only ions present in the MeV energy range in these DT plasmas. The beam power modulation on a time scale shorter than the α-particle slowing down time was chosen for modulating the α-particle source and thus sustaining a BOT in the α-particle distribution. High-frequency modes in the toroidicity-induced Alfven eigenmode (TAE) frequency range and multiple short-lived modes in a wider frequency range have been detected in these DT discharges with interferometry, soft x-ray cameras, and reflectometry. The modes observed were localised close to the magnetic axis and were not seen in the Mirnov coils. Analysis with the TRANSP and Fokker-Planck FIDIT codes confirms that α-particle distributions with BOT in energy were achieved during some time intervals in these discharges though no clear correlation was found between the times of the high-frequency mode excitation and the BOT time intervals. The combined magneto-hydrodynamic (MHD) and kinetic modelling studies show that the high-frequency mode in the TAE frequency range is best fitted with a TAE of toroidal mode number n= 9. This mode is driven mostly by the on-axis beam ions while the smaller drive due to the pressure gradient of α-particles allows overcoming the marginal stability and exciting the mode. The observed multiple short-lived modes in a wider frequency range are identified as the on-axis kinetic AEs predicted in Rosenbluth and Rutherford.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization
The phononic band diagram of a periodic square structure fabricated by femtosecond laser pulse-induced two photon polymerization is recorded by Brillouin light scattering (BLS) at hypersonic (GHz) frequencies and computed by finite element method. The theoretical calculations along the two main symmetry directions quantitatively capture the band diagrams of the air- and liquid-filled structure and moreover represent the BLS intensities. The theory helps identify the observed modes, reveals the origin of the observed bandgaps at the Brillouin zone boundaries, and unravels direction dependent effective medium behavior.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Experimental investigation of the crashworthiness of scaled composite sailplane fuselages
The crash dynamics and energy absorption of composite sailplane fuselage segments undergoing nose-down impact were investigated. More than 10 quarter-scale structurally similar test articles, typical of high-performance sailplane designs, were tested. Fuselages segments were fabricated of combinations of fiberglass, graphite, Kevlar, and Spectra fabric materials. Quasistatic and dynamic tests were conducted. The quasistatic tests were found to replicate the strain history and failure modes observed in the dynamic tests. Failure modes of the quarter-scale model were qualitatively compared with full-scale crash evidence and quantitatively compared with current design criteria. By combining material and structural improvements, substantial increases in crashworthiness were demonstrated.
Kampf, Karl-Peter↗
Progress in understanding the enhanced pedestal H-mode in NSTX
The paper describes the enhanced pedestal (EP) H-mode observed in the National Spherical Torus Experiment (NSTX). The defining characteristics of EP H-mode are given, namely i)transition after the L- to H-mode transition, ii) region of very steep ion temperature gradient, and iii) associated region of strong rotational shear. A newly observed long-pulse EP H-mode example shows quiescent behavior for as long as the heating and current drive sources are maintained. Cases are shown where the region of steep ion temperature gradient is located at the very edge, and cases where it is shifted up to 10 cm inward from the plasma edge; these cases are united by a common dependence of the ion temperature gradient on the toroidal rotation frequency shear. EP H-mode examples have been observed across a wide range of q95 and pedestal collisionality. No strong changes in the fluctuation amplitudes have been observed following the eP H-mode transition, and transport analysis indicates that the ion t hermal transport is comparable to or less than anticipated from a simple neoclassical transport model. Cases are shown where EP H-modes were reliably generated, through these low-q95 examples were difficult to sustain. A case where an externally triggered ELM precipitates the transition to EP H-mode is also shown, though an initial experiment designed to trigger EP-H-modes in this fashion was successful.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Progress In Understanding The Enhanced Petestal H-mode In NSTX
This paper describes the enhanced pedestal (EP) H-mode observed in the National Spherical Torus Experiment (NSTX). The defining characteristics of EP H-mode are given, namely i) transition after the L- to H-mode transition, ii) region of very steep ion temperature gradient, and iii) associated region of strong rotational shear. A newly observed long-pulse EP H-mode example shows quiescent behavior for as long as the heating and current drive sources are maintained. Cases are shown where the region of steep ion temperature gradient is located at the very edge, and cases where it is shifted up to 10 cm inward from the plasma edge; these cases are united by a common dependence of the ion temperature gradient on the toroidal rotation frequency shear. EP H-mode examples have been observed across a wide range of q 95 and pedestal collisionality. No strong changes in the fluctuation amplitudes have been observed following the eP H-mode transition, and transport analysis indicates that the ion thermal transport is comparable to or less than anticipated from a simple neoclassical transport model. Cases are shown where EP H-modes were reliably generated, through these low-q 95 examples were difficult to sustain. A case where an externally triggered ELM precipitates the transition to EP H-mode is also shown, though an initial experiment designed to trigger EP-H-modes in this fashion was successful.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Propulsion Requirements and Options for the New Millennium Interferometer (DS-3) Mission
The New Millennium Interferometer (DS-3) Mission is described along with a new candidate observation plan which takes advantage of an observation mode in which data is collected as the spacecraft are in relative motion.
Interferometer↗
Low-frequency fluctuations in the magnetosheath near the magnetopause
There are four low-frequency modes which may propagate in a high-beta nearly bi-Maxwellian plasma. These are the magnetosonic, Alfven, ion acoustic, and mirror modes. This manuscript defines a procedure based on linear Vlasov theory for the unique identification of these modes by use of transport ratios, dimensionless ratios of the fluctuating field and plasma quantities. A single parameter, the mode deviation is calculated using the plasma and magnetic field data gathered by the Active Magnetospheric Particle Tracer Explorers/Ion Release Module (AMPTE/IRM) spacecraft to identify the modes observed in the terrestial magnetosheath near the magnetopause. As well as determining the mode which best describes the observed fluctuations, it gives us a measure of whether or not the resulting identification is unique. Using 17 time periods temporally close to a magnetopause crossing, and confining our study to the frequency range from 0.01 to 0.04 Hz, we find that the only clearly identified mode in this frequency range is the mirror mode. Most commonly, the quasi-perpendicular mirror mode (with wave vector k roughly perpendicular to the background magnetic field B(sub zero) is observed. In two events the quasi-parallel mirror mode k parallel B(sub zero) was identified.
Denton, Richard E.↗
Emergent actin flows explain distinct modes of gliding motility
During host infection, Toxoplasma gondii and related unicellular parasites move using gliding, which differs fundamentally from other known mechanisms of eukaryotic cell motility. Gliding is thought to be powered by a thin layer of flowing filamentous (F)-actin sandwiched between the plasma membrane and a myosin-covered inner membrane complex. How this surface actin layer drives the various gliding modes observed in experiments—helical, circular, twirling and patch, pendulum or rolling—is unclear. Here we suggest that F-actin flows arise through self-organization and develop a continuum model of emergent F-actin flow within the confines provided by Toxoplasma geometry. In the presence of F-actin turnover, our model predicts the emergence of a steady-state mode in which actin transport is largely directed rearward. Removing F-actin turnover leads to actin patches that recirculate up and down the cell, which we observe experimentally for drug-stabilized actin bundles in live Toxoplasma gondii parasites. These distinct self-organized actin states can account for observed gliding modes, illustrating how different forms of gliding motility can emerge as an intrinsic consequence of the self-organizing properties of F-actin flow in a confined geometry.
59 BASIC BIOLOGICAL SCIENCES↗
Structures of glasses created by multiple kinetic arrests
X-ray scattering has been used to characterize glassy itraconazole (ITZ) prepared by cooling at different rates. Faster cooling produces ITZ glasses with lower (or zero) smectic order with more sinusoidal density modulation, larger molecular spacing, and shorter lateral correlation between the rod-like molecules. We find that each glass is characterized by not one, but two fictive temperatures T f (the temperature at which a chosen order parameter is frozen in the equilibrium liquid). The higher T f is associated with the regularity of smectic layers and lateral packing, while the lower T f with the molecular spacings between and within smectic layers. This indicates that different structural features are frozen on different timescales. The two timescales for ITZ correspond to its two relaxation modes observed by dielectric spectroscopy: the slower δ mode (end-over-end rotation) is associated with the freezing of the regularity of molecular packing and the faster α mode (rotation about the long axis) with the freezing of the spacing between molecules. Finally, our finding suggests a way to selectively control the structural features of glasses.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗