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NASA NTRS1996

Integration of the White Sands Complex into a Wide Area Network

The NASA White Sands Complex (WSC) satellite communications facility consists of two main ground stations, an auxiliary ground station, a technical support facility, and a power plant building located on White Sands Missile Range. When constructed, terrestrial communication access to these facilities was limited to copper telephone circuits. There was no local or wide area communications network capability. This project incorporated a baseband local area network (LAN) topology at WSC and connected it to NASA's wide area network using the Program Support Communications Network-Internet (PSCN-I). A campus-style LAN is configured in conformance with the International Standards Organization (ISO) Open Systems Interconnect (ISO) model. Ethernet provides the physical and data link layers. Transmission Control Protocol and Internet Protocol (TCP/IP) are used for the network and transport layers. The session, presentation, and application layers employ commercial software packages. Copper-based Ethernet collision domains are constructed in each of the primary facilities and these are interconnected by routers over optical fiber links. The network and each of its collision domains are shown to meet IEEE technical configuration guidelines. The optical fiber links are analyzed for the optical power budget and bandwidth allocation and are found to provide sufficient margin for this application. Personal computers and work stations attached to the LAN communicate with and apply a wide variety of local and remote administrative software tools. The Internet connection provides wide area network (WAN) electronic access to other NASA centers and the world wide web (WWW). The WSC network reduces and simplifies the administrative workload while providing enhanced and advanced inter-communications capabilities among White Sands Complex departments and with other NASA centers.

Boucher, Phillip Larry↗

NASA NTRS1998

On Substrate for Atomic Chain Electronics

A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom structures. However, the two requirements conflict. For excellent electronic isolation, we may seek adatom confinement via van der Waals interaction without chemical bonding to the substrate atoms, but the confinement turns out to be very weak and hence unsatisfactory. An alternative chemical bonding scheme with excellent structural strength is examined, but even fundamental adatom chain properties such as whether chains are semiconducting or metallic are strongly influenced by the nature of the chemical bonding, and electronic isolation is not always achieved. Conditions for obtaining semiconducting chains with well-localized surface-modes, leading to good isolation, are clarified and discussed.

Yamada, Toshishige↗

NASA NTRS1994

Standing shocks in a two-fluid solar wind

We present a numerical study of the formation of standing shocks in the solar wind using a two-fluid time-dependent model in the presence of Alfven waves. Included in this model is the adiabatic cooling and thermal conduction of both electrons and protons. In this study, standing shocks develop in the flow when additional critical points form as a result of either localized momentum addition or rapid expansion of the flow tube below the existing sonic point. While the flow speed and density exhibit the same characteristics as found in earlier studies of the formation of standing shocks, the inclusion of electron and proton heat conduction produces different signatures in the electron and proton temperature profiles across the shock layer. Owing to the strong heat conduction, the electron temperature is nearly continuous across the shock, but its gradient has a negative jump across it, thus producing a net heat flux out of the shock layer. The proton temperature exhibits the same characteristics for shocks produced by momentum addition but behaves differently when the shock is formed by the rapid divergence of the flow tube. The adiabatic cooling in a rapidly diverging flow tube reduces the proton temperature so substantially that the proton heat conduction becomes negligible in the vicinity of the shock. As a result, protons experience a positive jump in temperature across the shock. While Alfven waves do not affect the formation of standing shocks, they contribute to the change of the mmomentum and energy balance across them. We also find that for this solar wind model the inclusion of thermal conduction and adiabatic cooling for the elctrons and protons increases significantly the range of parameters characterizing the formation of standing shocks over those previously found for isothermal and polytropic models.

Habbal, Shadia R.↗

NASA NTRS1976

Deuteron whistler and trans-equatorial propagation of the ion cyclotron whistler

The paper investigates two unusual types of ion cyclotron whistlers that were found in the low-latitude topside ionosphere by analyzing ISIS VLF electric-field data received at Kashima, Japan. One type is characterized by an asymptotic frequency equal to one half the local proton gyrofrequency; the asymptotic frequency of the other type corresponds to the minimum proton gyrofrequency along the geomagnetic field line passing through the satellite. The observations are compared with theoretical spectrograms of the ion cyclotron whistlers computed for appropriate model distributions of electrons and ions in the topside ionosphere. It is found that the whistlers with the asymptotic frequency of one half the local proton gyrofrequency are deuteron whistlers and that the other whistlers are due to the transequatorial propagation of proton or deuteron whistlers originating in the southern hemisphere.

Watanabe, S.↗

NASA NTRS1979

Magnetospheric multiharmonic instabilities

The paper discusses linear convective growth rates of instabilities of electrostatic multiple electron cyclotron harmonic waves in a plasma consisting of a hot electron component with a loss-cone type of free energy source and a cold electron component of presumably ionospheric origin. When the ratio of cold to hot electron temperature is small, the cold upper hybrid frequency controls the harmonic bands that can be nonconvectively stable. When this ratio increases above a few times 0.01, nonconvective instability disappears simultaneously for each harmonic band, when the density ratio is less than unity. A consistent interpretation of the spatial localization and harmonic frequency bandwidths of the observed waves can be made assuming linear convective saturation, provided that the cold electrons have temperatures considerably in excess of those in the ionosphere.

Ashour-Abdalla, M.↗

NASA NTRS1973

The dayside midlatitude plasma trough

The electrostatic probe experiment aboard the ISIS-1 satellite detects a quasi-stable dayside plasma trough in the protonosphere with a characteristic time of at least 2 weeks. This behavior contrasts with measurements at 1000 km from Explorer-22, which indicate a trough of a characteristic time less than a satellite orbit period. Associated with the protonospheric trough is an electron temperature maximum approximately 6000 K that is sharp at midnight and broad at noon. In spring and summer, a second noontime temperature maximum often appears poleward of 70 invariant latitude, accompanied by an enhancement in the ionization. The ISIS-1 data indicates that local processes such as dayside F-region photoionization and ionization by energetic cusp particles produce enhancements in plasma density and electron temperature. These enhancements modify the plasmaspheric boundary to varying degrees along a magnetic field tube, thus leading to a plasmas pheric boundary with distinctive features at various positions along a field tube.

Miller, N. J.↗

NASA NTRS1994

DE 1 and Viking observations associated with electron conical distributions

Data from the electron detectors on board the Swedish Viking satellite launched during a period of low solar activity and from the Dynamic Explorer (DE) 1 satellite launched during active solar coditions have been examined for the occurrence and location of electron conical distributions and several conclusions can be drawn. First, we note that most of the best examples of electron conics observed by the V-3 experiment onboard Viking occurred in the afternoon sector in the range of magneitc local time 14 hours less than Magnetic Local Time (MLT) less than 18 hours, at midaltitudes in the range 10,000 km less than h less than 13,500 km, with few occurring in the nightside auroral region, a region poorly sampled at altitudes greater than 5000 km. For the Viking data there is an association of electron conics with upper hybrid waves. DE 1 observations made by the high-altitude plasma instrument (HAPI) indicate that electron conics were observed in the midmorning sector and the late evening sector, and as has been reported earlier, the correlation with upper hybird waves was good. The HAPI did not sample the afternoon sector. The electon conics observed on both satellites occurred in the presence of at least a modest (several kilovolts) potential difference beneath the satellite with a maximum energy that was usually, but not always, equal to or greater than the maximum energy of the electron conics. Two independent sets of observations by DE 1 suggest two distinct production mechanisms for electron conics. Examiniation of DE 1 electric field measurements from the plasma wave instrument during the observation of electron conics show simultaneous parallel oscillations in the frequency range of 0.2 Hz less than f less than 0.5 Hz during one and perhaps two of four events examined, and upper hybrid waves were observed on all four events. In addition, recent observations of '90-deg' electron conics associated with auroral kilometric radiation source regions suggest a perpendicular heating mechanism produced by wave-particle interaction. Such distributions may be observed as electron conics at higher altitudes. These results suggest more than one possible source mechanism may be responsible for electron conics.

Menietti, J. D.↗

NASA NTRS1976

Magnetospheric chorus - Occurrence patterns and normalized frequency

Over 400 hours of continuous broadband data obtained by the OGO 3 satellite are analyzed to provide a statistically accurate description of band-limited (magnetospheric) chorus. Certain aspects of the chorus frequency distribution are interpreted in terms of a gyroresonant electron feedback model of generation. An example of high chorus activity during an outbound pass through the noon magnetosphere is examined in detail, the spectral complexity of some chorus is illustrated, and the diurnal variation of chorus occurrence is investigated. The frequency and bandwidth distributions of chorus are analyzed. The results indicate that chorus occurrence depends strongly on local time and dipole latitude, the general region of maximum chorus occurrence approximates the previously reported zone of 'hard' electron precipitation, and the normalized chorus frequency is strongly dependent on dipole latitude. It is shown how a change in the curvature of the whistler-mode refractive-index surface affects focusing of radiation along magnetic field lines and how interference can occur between modes with slightly different ray velocities. It is concluded that most magnetospheric chorus consists of rising emissions which are probably generated by gyroresonant electrons slightly off the equator.

Burtis, W. J.↗

NASA NTRS1986

Process Produces Low-Secondary-Electron-Emission Surfaces

Textured carbon layer applied to copper by sputtering. Carbon surface characterized by dense, random array of needle-like spires or peaks that extend perpendicularly from local copper surface. Spires approximately 7 micrometers in height and spaced approximately 3 micrometers apart, on average. Copper substrate essentially completely covered by carbon layer, is tenacious and not damaged by vibration loadings representative of multistage depressed collector (MDC) applications. Process developed primarily to provide extremely low-secondary-electron-emission surface for copper for use as highefficiency electrodes in MDC's for microwave amplifier traveling-wave tubes (TWT's). Tubes widely used in space communications, aircraft, and terrestrial applications.

Curren, A. N.↗

NASA NTRS1991

Empirical models of the latitudinal variations of Te and Ne in the ionosphere at solar maximum

A global spectral model of electron temperature and density is developed in which only the latitudinal variations observed in narrow altitude and local time bands are used. The measurements for this purpose are obtained during intervals that are short as compared to a season. By suppressing all variables except latitude the model can use 17th-order polynomials and generates a latitudinal structure that is similar to that described by the observational data. The treatment is designed to correct for the eccentricity and slow evolution of the data-collection satellite orbit so that small-scale features can be resolved. By comparing the results of a global model and the present latitudinal model to observational measurements of electron temperature and density it is shown that auroral-zone and midlatitude trough structures are not resolved in latitudinal models. The observational data can be used to study the response of electron density and temperature to solar EUV flux variations and geomagnetic activity.

Brace, L. H.↗

NASA NTRS2004

Sensor for Monitoring Nanodevice-Fabrication Plasmas

The term plasma process diagnostics (PPD) refers to a spectroscopic technique and sensing hardware that have been proposed for monitoring plasma processes used to fabricate electronic devices that feature sizes as small as several nanometers. Nanometer dimensions are characteristic of the quantum level of miniaturization, where single impurity atoms or molecules can drastically change the local properties of the nanostructures. Such changes may be purposely used in nanoscale design but may also be extremely damaging or cause improper operation of the fabricated devices. Determination of temperature and densities of reactants near the developing features is important, since the structural synthesis is affected by characteristics of the local microenvironment. Consequently, sensors capable of nonintrusive monitoring with high sensitivity and high resolution are essential for real-time atomistic control of reaction kinetics and minimizing trace contamination in plasma processes used to fabricate electronic nanodevices. Such process-monitoring sensors are required to be compact, multiparametric, and immune to the harsh environments of processing plasmas. PPD is intended to satisfy these requirements. The specific technique used to implement plasma diagnostics with a PPD sensor would be an advanced version of continuous-wave cavity-ringdown spectroscopy (CW-CRDS) capable of profiling spectral line broadenings in order to derive both Doppler and Stark components. CRDS is based on measurements of the rate of absorption of laser light in an optical resonator. The ultimate sensitivity results from a very long absorption path length within the cavity and immunity to variations in incident laser intensity. The proposed version of this technique would involve the use of multiplexing tunable laser diodes and an actively modulated high-reflectivity optical resonator, thus offering a synergistic combination of simplicity, compactness, high sensitivity, and high resolution. The multiplexing capabilities of diode lasers could be utilized to make the PPD sensor a single, simple, compact, and inexpensive tool for the acquisition of multiparametric data. A PPD sensor would be capable of continuous measurement of such physical parameters as gas temperature, gas velocity, electron number density, and absolute densities of reacting chemical species. A laser beam can be easily adjusted to analyze the immediate vicinity of the growing nanostructures (or features etched down) in real time. The absorption enhancement in an optical cavity would afford the sensitivity needed for measurement of the temperature and densities of species at concentrations significantly lower than measurable by other nonintrusive techniques. It is anticipated that fully developed PPD sensors would enable simultaneous measurement of local temperature and determination of plasma species responsible for the synthesis and functionalization of nanodevices. These sensors would also enable tracking the pathways and origins of damaging contaminants, thereby providing feedback for adjustment of processes to optimize them and reduce contamination. The PPD sensors should also be useful for optimization of conventional microelectronics manufacturing plasma processes. Going beyond plasma processes for fabrication of electronic devices, PPD sensors could be used for monitoring of atoms, molecules, ions, radicals, clusters, and particles in a variety of other settings, including outer space. Because of their high sensitivity, such sensors could also prove useful for detecting traces of illegal drugs and explosives.

Bolshakov, Alexander↗

NASA NTRS2016

Electrical, Electronic, and Electromechanical (EEE) Parts Management and Control Requirements for Space Flight Hardware and Critical Ground Support Equipment...aka... The NASA EEE Parts Standard, NASA-STD 8739.10

Describes development and content of a new NASA Standard for Electrical Electronic and Electromechanical (EEE) parts. This Standard reflects current practices, instead of changing them. Most NASA Centers utilize local documents, but there is minimal consistency across the Agency. A gap analysis clearly shows the differences that exist among the different centers and with respect to the NASA Parts Policy. Once approved, the new standard can be referenced in contracts and agreements with organizations outside of NASA.

Electronic↗

NASA NTRSDate not supplied

Microbes Share Rides Too: Updating Encapsulated Bioburden Estimate Values in Electronic Parts Common to Class D Missions

As NASA develops more planetary protection missions that are Category III and in the Class D/rideshare mission platform, there is an increasing reliance on estimation of prelaunch bioburden to understand needs for burn up and breakup analyses or other methods to meet pre-launch bioburden levels. Current levels estimated for the encapsulated bioburden of semiconductor parts cited by NASA have been based on estimates of semiconductor manufacturing approaches from the 1970s that do not incorporate the evolving cleanliness of semiconductor manufacturing since that time. This investigation will focus on direct sampling of semiconductor parts for encapsulated bioburden values, drawing upon Goddard’s strength in EEE parts, supply chain management, destructive parts analysis and existing local planetary protection lab facilities to prepare and measure encapsulated bioburden at a statistically significant level for standard electronics parts common to known Class D/rideshare platforms.

planetary protection↗

NASA NTRSDate not supplied

Microbes Share Rides Too: Updating Encapsulated Bioburden Estimate Values in Electronic Parts Common to Class D Mission Platforms.

As NASA develops more planetary protection missions that are Category III and in the Class D/rideshare mission platform, there is an increasing reliance on estimation of prelaunch bioburden to understand needs for burn up and breakup analyses or other methods to meet pre-launch bioburden levels. Current levels estimated for the encapsulated bioburden of semiconductor parts cited by NASA have been based on estimates of semiconductor manufacturing approaches from the 1970s that do not incorporate over fifty years of evolving cleanliness of semiconductor manufacturing processes and facilities. This investigation will focus on direct sampling of semiconductor parts for encapsulated bioburden values, drawing upon Goddard’s strength in EEE parts, supply chain management, destructive parts analysis and existing local planetary protection lab facilities to prepare and measure encapsulated bioburden at a statistically significant level for standard electronics parts common to known Class D/rideshare platforms.

planetary protection↗

NASA NTRS1968

Silicon surface barrier detectors used for liquid hydrogen density measurement

Multichannel system employing a radioisotope radiation source, strontium-90, radiation detector, and a silicon surface barrier detector, measures the local density of liquid hydrogen at various levels in a storage tank. The instrument contains electronic equipment for collecting the density information, and a data handling system for processing this information.

James, D. T.↗

NASA NTRS1976

The lower ionosphere of Titan

Ionization of the atmosphere of Titan by galactic cosmic rays is a very significant process throughout the altitude range from 100 to 400 km. An approximate form of the Boltzmann equation for cosmic-ray transport has been used to obtain local ionization rates. Models of both ion and neutral chemistry have been employed to compute electron and ion density profiles for three different values of the H2/CH4 abundance ratio. The peak electron density is of the order of 1000 per cu cm. The most abundant positive ions are C2/H9(+) and C3H9(+), while the predicted densities of the negative ions H(-) and CH3(-) are very small (less than one ten-thousandth that of the positive ions). It is suggested that inclusion of the ion chemistry is important in the computation of the H and CH3 density profiles in the lower ionosphere.

Capone, L. A.↗

NASA NTRS1982

Plasma behavior during energetic electron streaming events further evidence for substorm-associated magnetic reconnection

A recent study showed that streaming energetic (more than 200 keV) electrons in earth's magnetotail are statistically associated with southward magnetic fields and with enhancements of the AE index. It is shown here that the streaming electrons characteristically are preceded by an approximately 15-minute period of tailward plasma flow and followed by a dropout of the plasma sheet, thus demonstrating a clear statistical association between substorms and the classical signatures of magnetic reconnection and plasmoid formation. Additionally, a brief upward surge of mean electron energy preceded plasma dropout in several of the events studied, providing direct evidence of localized, reconnection-associated heating processes.

Bieber, J. W.↗

NASA NTRS1983

An analytic solution for the response of the neutral atmosphere to the high-latitude convection pattern

The analytic solutions to a two-dimensional, shallow-water model of the high-latitude thermosphere are developed. The equations are a linearized representation of the response of the neutral atmosphere to the momentum source due to the plasma convection pattern. The obtained results show how the neutral winds depend on the Pedersen and Hall ion drag coefficients and the horizontal wave number. The response depends on the dimensionless scale as it appears in the product of the Rossby radius of deformation and the wave number. The flow pattern is shifted in local time from the plasma flow pattern by an amount that depends on the average electron density. At the largest scales there is a 180 deg phase shift between the rotational flow components in the E and F regions. The model applies to quiet magnetic conditions and below 200 km of altitude.

Mikkelsen, I. S.↗