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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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NASA NTRS2002

Satellite Spots Turbulence Producing Mountain Waves in the Stratosphere

When masses of air flow over massive mountains, invisible waves often roil high into the stratosphere, affecting weather and mixing the chemicals that contribute to ozone depletion. The waves also create turbulence that can be a danger to high-altitude research missions by NASA's lightweight ER-2 aircraft, as well as shuttle flights upon reentry. In Friday's issue of the journal Science, researchers report for the first time a technique that allows them to see temperature signatures from these invisible mountain waves. The method, involving high-resolution, satellite-based measurement of adjacent pockets of the atmosphere, is expected to aid in spotting turbulence and, one day, improve weather forecasts.

Britt, Robert Roy↗
NASA NTRS2002

The Social Life of a Data Base

This paper presents the complex social life of a large data base. The topics include: 1) Social Construction of Mechanisms of Memory; 2) Data Bases: The Invisible Memory Mechanism; 3) The Human in the Machine; 4) Data of the Study: A Large-Scale Problem Reporting Data Base; 5) The PRACA Study; 6) Description of PRACA; 7) PRACA and Paper; 8) Multiple Uses of PRACA; 9) The Work of PRACA; 10) Multiple Forms of Invisibility; 11) Such Systems are Everywhere; and 12) Two Morals to the Story. This paper is in viewgraph form.

Linde, Charlotte↗
NASA NTRS2003

An Obstacle Alerting System for Agricultural Application

Wire strikes are a significant cause of helicopter accidents. The aircraft most at risk are aerial applicators. The present study examines the effectiveness of a wire alert delivered by way of the lightbar, a GPS-based guidance system for aerial application. The alert lead-time needed to avoid an invisible wire is compared with that to avoid a visible wire. A flight simulator was configured to simulate an agricultural application helicopter. Two pilots flew simulated spray runs in fields with visible wires, invisible wires, and no wires. The wire alert was effective in reducing wire strikes. A lead-time of 3.5 sec was required for the alert to be effective. The lead- time required was the same whether the pilot could see the wire or not.

DeMaio, Joe↗
NASA NTRS2002

An Obstacle Alerting System for Agricultural Application

Wire strikes are a significant cause of helicopter accidents. The aircraft most at risk are aerial applicators. The present study examines the effectiveness of a wire alert delivered by way of the lightbar, a GPS-based guidance system for aerial application. The alert lead-time needed to avoid an invisible wire is compared with that to avoid a visible wire. A flight simulator was configured to simulate an agricultural application helicopter. Two pilots flew simulated spray runs in fields with visible wires, invisible wires, and no wires. The wire alert was effective in reducing wire strikes. A lead-time of 3.5 sec was required for the alert to be effective. The lead-time required was the same whether the pilot could see the wire or not.

DeMaio, Joe↗
NASA NTRS2000

Motion coherence affects human perception and pursuit similarly

Pursuit and perception both require accurate information about the motion of objects. Recovering the motion of objects by integrating the motion of their components is a difficult visual task. Successful integration produces coherent global object motion, while a failure to integrate leaves the incoherent local motions of the components unlinked. We compared the ability of perception and pursuit to perform motion integration by measuring direction judgments and the concomitant eye-movement responses to line-figure parallelograms moving behind stationary rectangular apertures. The apertures were constructed such that only the line segments corresponding to the parallelogram's sides were visible; thus, recovering global motion required the integration of the local segment motion. We investigated several potential motion-integration rules by using stimuli with different object, vector-average, and line-segment terminator-motion directions. We used an oculometric decision rule to directly compare direction discrimination for pursuit and perception. For visible apertures, the percept was a coherent object, and both the pursuit and perceptual performance were close to the object-motion prediction. For invisible apertures, the percept was incoherently moving segments, and both the pursuit and perceptual performance were close to the terminator-motion prediction. Furthermore, both psychometric and oculometric direction thresholds were much higher for invisible apertures than for visible apertures. We constructed a model in which both perception and pursuit are driven by a shared motion-processing stage, with perception having an additional input from an independent static-processing stage. Model simulations were consistent with our perceptual and oculomotor data. Based on these results, we propose the use of pursuit as an objective and continuous measure of perceptual coherence. Our results support the view that pursuit and perception share a common motion-integration stage, perhaps within areas MT or MST.

NASA Center ARC↗
NASA NTRS2004

Co-axial Joint Technology Applied to Antenna Backup Structures

The increasing demand to improve focusing accuracy and to accommodate higher frequencies in space communications and radio astronomy has created significant challenges for improving the capability of the constituent systems in radio antennas and telescopes. One important system is the radio antenna/telescope backup structure connections. The backup structure is a key element in providing a stable, precise and rigid support for the reflective surface. The ideal connection for these types of structures is rigid and concentric resulting in minimal deformation with stress/strain curves that are linear, repeatable and exhibiting no hysteresis over the entire service load range. Conceivably such a connection could be designed so that the stress/strain curve mimics the stress/strain characteristics of the connecting member in both tension and compression. When this is achieved then such joints can be said to be 'invisible' in the global behavior of the backup structure. At that point, overall reflector deflection becomes more linear and highly predictable. In conjunction with this advantage, optimized backup structure geometries, adaptive reflectors and compensating algorithms can best be applied in producing an instrument of unparalleled performance. This paper introduces Co-Axial Joint (CAJ) technology as the practical and economical means to produce an invisible connection.

trusses↗
NASA NTRS2003

Real-Time, High-Frequency QRS Electrocardiograph

An electronic system that performs real-time analysis of the low-amplitude, high-frequency, ordinarily invisible components of the QRS portion of an electrocardiographic signal in real time has been developed. Whereas the signals readily visible on a conventional electrocardiogram (ECG) have amplitudes of the order of a millivolt and are characterized by frequencies <100 Hz, the ordinarily invisible components have amplitudes in the microvolt range and are characterized by frequencies from about 150 to about 250 Hz. Deviations of these high-frequency components from a normal pattern can be indicative of myocardial ischemia or myocardial infarction

Schlegel, Todd T.↗
NASA NTRS1965

The aurora.

Visible and invisible aurora discussing morphology, occurrence, magnetic activity, absorption, geophysical and energy particle

AURORAL IONIZATION↗
NASA NTRS1972

Far UV camera/spectrograph

In March 1610, Galileo Galilei reported the first use of a telescope to view mountains and maria on the Moon. On April 21, 1972, the Apollo 16 commander pointed a somewhat more complex optical instrument at the Earth from the Moon and obtained several remarkable photographs showing atmospheric rather than surface features. The optical part of the far UV camera (aperture, 7.5 cm) was not much larger than Galileo's telescope. Like his, this instrument was also pointed at other celestial objects that Galileo viewed, including the Milky Way and Jupiter, and the Large Magellanic Cloud (LMC), which is not visible from Italy. More important, the far UV camera/spectrograph recorded light in the invisible band of wavelengths between 50 and 160 nm, approximately one-third the wavelength that can penetrate the atmosphere of the Earth to ground-based telescopes. As described in more detail in this section, these UV observations from the Moon allow study of the entire atmosphere of the Earth and the geocorona. The photographs show hydrogen and other gases in the solar wind and interplanetary media, and they provide new data on stars, nebulae, and galaxies much farther away. When used as a spectrograph, the instrument distributes the light it receives according to wavelength, and the resulting spectrum shows bright lines or gaps known to be characteristic of various gases, such as hydrogen (H), helium (He), oxygen (O), nitrogen (N), and neon (Ne). If a gas cloud is hot, the atoms are excited and the spectrum shows bright emission lines; if it is cool, the atoms absorb light, leaving gaps or absorption lines. The far UV camera is blind to ordinary visible light; for that reason, the photographs show very few of the stars mapped by ground-based telescopes. Only the very-high-temperature (blue) stars of spectral classes O, B, and possibly A (temperatures from 50000 ° down to 10000°K) are expected to be recorded. Image blackness or density on the negatives also depends on the brightness of the star, which astronomers measure in an inverted logarithmic scale of magnitudes. A star of 6 magnitudes (mag.) can barely be seen with the unaided eye. An 11-mag. star is 100 times fainter, and a 12-mag. star is 2.5 times fainter yet. The faintest star recorded by the far UV camera is at least 11 mag., which is called the limiting magnitude.

George R. Carruthers↗
NASA NTRS1973

California coast nearshore processes study

The author has identified the following significant results. Remote sensor aircraft flights took place simultaneously with ERTS-1 overpasses at the San Francisco, Monterey Bay, and Santa Barbara test cells. The cameras and scanners used were configured for detecting suspended sediment and for maximum water penetration. The Ektachrome/Wratten 12 photographs which were intentionally overexposed 1-1/2 stops were found to show the most extensive sediment transport detail. Minus blue/K 2 photographs illustrate nearshore underwater bottom detail including the head of the Mugu submarine canyon. The EMSIDE 9 channel scanner was employed to classify and differentiate suspended sediment, oil, kelp, and other materials found in the nearshore area. Processing of bulk ERTS-1 computer compatible tapes was utilized to enhance and analyze nearshore sediments. This technique was most successful in enhancing subtle nearshore features found to be faint or invisible on prints made from the supplied negatives. In addition to this continuing computer process, an effort was initiated to interface density values from the bulk tapes into contouring and mapping software.

Pirie, D. M.↗
NASA NTRS1973

Star formation and evolution in spiral galaxies.

Evolutionary models for regions of M31 and M33 and the solar neighborhood are based on a stellar birthrate suggested by the dynamics of spiral structure: we assume that stars are formed very efficiently until the gas content reaches equilibrium at its present value, which takes about 1 b.y.; thereafter, the birthrate just equals the rate at which gas enters the system from stellar mass-loss or infall of intergalactic matter. Each model represents an average around a cylindrical-shell-shaped region, which is homogeneous and closed except for possible infall. The disk and spiral-arm populations only are considered. Each star is followed in the H-R diagram from the main sequence to death as an invisible remnant. Integrated magnitudes, colors, mass-to-light ratio (M/L), gas content, helium and metal abundance (Z), are computed in steps of 1 b.y.

Quirk, W. J.↗
NASA NTRS1973

California coast nearshore processes study

The author has identified the following significant results. Large scale sediment plumes from intermittent streams and rivers form detectable seasonal patterns on ERTS-1 imagery. The ocean current systems, as plotted from three California coast ERTS mosaics, were identified. Offshore patterns of sediment in areas such as the Santa Barbara Channel are traceable. These patterns extend offshore to heretofore unanticipated ranges as shown on the ERTS-1 imagery. Flying spot scanner enhancements of NASA tapes resulted in details of subtle and often invisible (to the eye) nearshore features. The suspended sediments off San Francisco and in Monterey Bay are emphasized in detail. These are areas of extremely changeable offshore sediment transport patterns. Computer generated contouring of radiance levels resulted in maps that can be used in determining surface and nearsurface suspended sediment distribution. Tentative calibrations of ERTS-1 spectral brightness against sediment load have been made using shipboard measurements. Information from the combined enhancement and interpretation techniques is applicable to operational coastal engineering programs.

Pirie, D. M.↗
NASA NTRS1974

Determination of selenographic coordinates of lunar surface points from single pictures obtained from Zond 6

Pictures of the lunar surface with an image of practically the entire lunar limb were obtained from the Zond 6 spacecraft. During the time of exposure, the entire lunar surface covered by these photographs was illuminated by the sun. Such single pictures were used to find the external orientation elements and selenographic coordinates of the photographed lunar surface points. The selenographic coordinate system was specified by the Goloseyev catalog and was realized by points of this catalog identified on the pictures and termed reference points. Craters located on the invisible side of the moon and also other points of the Goloseyev catalog, which could be used as control points, were taken as the points being determined. The technique used to compute the selenographic coordinates of the points is outlined.

Ziman, Y. L.↗
NASA NTRS1975

Relationships between motion on isentropic surfaces from 3-H rawinsonde data and radar echoes

Vertical motion in insentropic surfaces obtained at 3-h intervals conducted on 11 and 12 May, 1974 is related to convection indicated by radar echoes. Temporal and spatial changes in vertical motion are shown and demonstrated to be associated with areas of convection. Large vertical motion was calculated, and it is shown that vertical motion changes as much as 20 cm s (-1) in a horizontal distance of 300 km. The rate of change of vertical motion is demonstrated to be as large a 8 cm s (-1)h(-1) from data taken at 3-h intervals, while data taken at 12-h intervals the same day displayed a maximum rate of change of 2 cm s(-1)n(-1). Radar observations confirmed that the intensity of convection varies as a result of the atmospheric variability as detected by 3-h data but is invisible in data taken at 12-h intervals.

Overall, J. W.↗
NASA NTRS1975

Application of LANDSAT to the Surveillance and Control of Eutrophication in Saginaw Bay

The author has identified the following significant results. LANDSAT digital data and ground truth measurements for Saginaw Bay (Lake Huron), Michigan, for 3 June 1974 can be correlated by stepwise linear regression technique and the resulting equations used to estimate invisible water quality parameters in nonsampled areas. Correlation of these parameters with each other indicates that the transport of Saginaw River water can now be traced by a number of water quality features, one or more of which are directly detected by LANDSAT. Five of the 12 water quality parameters are best correlated with LANDSAT band 6 measurements alone. One parameter (temperature) relates to band 5 alone and the remaining six may be predicted with varying degrees of accuracy from a combination of two bands (first band 6 and generally band 4 second).

Rogers, R. H.↗