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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Relative effectiveness of several simulated jet engine noise spectral treatments in reducing annoyance in a TV-viewing situation

An experiment was conducted in order to determine the relative effectiveness of several hypothetical jet engine noise treatments and to test hypothesis that speech interference, at least in part, mediates annoyance in a TV-viewing situation. Twenty-four subjects watched television in a simulated living room. Recorded jet flyover noises were presented in such a way as to create the illusion that aircraft were actually flying overhead. There were 27 stimuli (nine spectra at three overall levels) presented at an average rate of approximately one flight every 2 minutes. Subjects judged the annoyance value of individual stimuli using either a category rating method or magnitude estimation method in each of two 1-hour sessions. The spectral treatments most effective in reducing annoyance were at 1.6 Khz and 800 Hz, in that order. The degree of annoyance reduction resulting from all treatments was affected by the overall sound level of the stimuli, with the greatest reduction at the intermediate overall sound level, about 88 to 89 db(A), peak value. The results are interpreted as supporting the hypothesis that speech interference, at least in part, mediates annoyance with aircraft noise in a TV-viewing situation.

Gunn, W. J.↗
NASA NTRS1976

Earth Viewing Applications Laboratory (EVAL). Dedicated payload, standard test rack payload, sensor modifications

The preliminary analysis of strawman earth-viewing shuttle sortie payloads begun with the partial spacelab payload was analyzed. The payloads analyzed represent the two extremes of shuttle sortie application payloads: a full shuttle sortie payload dedicated to earth-viewing applications, and a small structure payload which can fly on a space available basis with another primary shuttle payload such as a free flying satellite. The intent of the dedicated mission analysis was to configure an ambitious, but feasible, payload; which, while rich in scientific return, would also stress the system and reveal any deficiences or problem areas in mission planning, support equipment, and operations. Conversely, the intent of the small structure payload was to demonstrate the ease with which a small, simple, flexible payload can be accommodated on shuttle flights.

Source record↗
NASA NTRS1978

Numerical procedure to determine geometric view factors for surfaces occluded by cylinders

A numerical procedure was developed to determine geometric view factors between connected infinite strips occluded by any number of infinite circular cylinders. The procedure requires a two-dimensional cross-sectional model of the configuration of interest. The two-dimensional model consists of a convex polygon enclosing any number of circles. Each side of the polygon represents one strip, and each circle represents a circular cylinder. A description and listing of a computer program based on this procedure are included in this report. The program calculates geometric view factors between individual strips and between individual strips and the collection of occluding cylinders.

Sawyer, P. L.↗
NASA NTRS1978

Extending the field of view of KD/asterisk/P electrooptic modulators

The use of KD(asterisk)P as a polarization rotator has been limited to small field of view instruments. To investigate this limitation, the index ellipsoid is used to describe the optical properties of KD(asterisk)P and to calculate the retardance and fast axis as a function of the angle of incidence and voltage. Computed converging light patterns are then compared with observed intensity patterns formed by KD(asterisk)P. Finally, computed intensity patterns are used to demonstrate how the field of view of KD(asterisk)P can be increased when properly aligned with a positive uniaxial crystal.

West, E. A.↗
NASA NTRS1980

The effect of viewing time, time to encounter, and practice on perception of aircraft separation on a cockpit display of traffic information

The concept of a cockpit display of traffic information (CDTI) includes the integration of air traffic, navigation, and other pertinent information in a single electronic display in the cockpit. Two studies were conducted to develop a clear and concise display format for use in later full-mission simulator evaluations of the CDTI concept. Subjects were required to monitor a CDTI for specified periods of time and to make perceptual judgments concerning the future position of a single intruder aircraft in relationship to their own aircraft. Experimental variables included: type of predictor information displayed on the two aircraft symbols; time to encounter point; length of time subjects viewed the display; amount of practice; and type of encounter (straight or turning). Results show that length of viewing time had little or no effect on performance; time to encounter influenced performance with the straight predictor but did not with the curved predictor; and that learning occurred under all conditions.

Oconnor, S.↗
NASA NTRS1980

System for forming a quadrified image comprising angularly related fields of view of a three dimensional object

A system for generating, within a single frame of photographic film, a quadrified image including images of angularly (including orthogonally) related fields of view of a near field three dimensional object is described. It is characterized by three subsystems each of which includes a plurality of reflective surfaces for imaging a different field of view of the object at a different quadrant of the quadrified image. All of the subsystems have identical path lengths to the object photographed.

Chamberlain, F. R.↗
NASA NTRS1981

Safety shield for vacuum/pressure chamber viewing port

Observers are protected from flying debris resulting from a failure of a vacuum or pressure chamber viewing port following an implosion or explosion by an optically clear shatter resistant safety shield which spaced apart from the viewing port on the outer surface of the chamber.

Shimansky, R. A.↗
NASA NTRS1978

Preliminary study of head-up assessment techniques. 1: Viewing duration of instrument panel and HUD symbology using a recall methodology

Eight commercial pilots were shown 50 colored, high fidelity slides of a standard instrument panel (IP) with the needle positions of each instrument varying from slide to slide and then 50 slides of a head-up display (HUD) symbology format which contained an equivalent amount of flight-related information as the instrument panel slides. All stimuli were presented under controlled, static viewing conditions that allowed the measurement of the speed and accuracy with which one randomly selected flight parameter on each slide could be read. The subject did not know which parameter would be requested and, therefore, had to remember the total set of information in order to answer the question correctly. The results showed that from 6.6 - 8.7 sec total viewing time was required to correctly extract altitude, airspeed, heading, VSI, or ADI from the IP slides and from 6.1 to 7.4 sec for the HUD slides.

Haines, R. F.↗
NASA NTRS1981

Space Telescope orbital viewing constraints

Astronomical observations with the Space Telescope will be constrained by spacecraft operational requirements and capabilities, orbital viewing conditions, and the space environment. While ultraviolet or bright visual-range observations may be performed for 53 to 94.6 minutes per orbit (from a 500 kilometer altitude), certain stray light sensitive experiments may be limited to 0-48 minutes of viewing per orbit. Careful operations planning may make possible observations of 'secondary' targets while a primary target is occulted, of objects as close as 18 deg to the sun, or of objects visible when the spacecraft is in a high radiation environment.

Sherrill, T. J.↗
NASA NTRS1982

An ultraviolet view of Be stars

Several types of ultraviolet observations of Be stars are briefly summarized, with a view towards identifying the characteristics, if any, that distinguish Be stars from other early type objects. The present weight of the evidence is that, from the point of view of ultraviolet data, Be stars are nearly indistinguishable from normal B stars. Both groups have similar characteristics, with differences only in degree. Further comparative studies of Be and nonBe stars have the potential to reveal the causes of the Be phenomenon, and possibly also the origins of winds in early type stars. Several areas for future ultraviolet research are suggested.

Snow, T. P.↗
NASA NTRS1982

Cloud cover from high-resolution scanner data - Detecting and allowing for partially filled fields of view

A new technique is presented for obtaining cloud cover and determining clear sky radiances using high-resolution IR scanner data. The technique, which can be automated, employs the spatial structure of the IR radiance field to identify radiances associated with fields of view that are either free of clouds or completely covered by clouds drawn from one or more distinct layers. The approach is particularly well-suited for determining clear sky radiances over oceans from which sea surface temperatures may be derived. In addition, for single-layered systems, the cloud cover fraction for a given region may be obtained from the clear sky radiance, the completely cloud-covered radiance, and the mean radiance for the region. For such systems the separation of completely covered from partially covered fields of view makes it possible to estimate the errors associated with commonly used threshold techniques for determining cloud cover.

Coakley, J. A., Jr.↗
NASA NTRS1981

Remote sensing research in geographic education: An alternative view

It is noted that within many geography departments remote sensing is viewed as a mere technique a student should learn in order to carry out true geographic research. This view inhibits both students and faculty from investigation of remotely sensed data as a new source of geographic knowledge that may alter our understanding of the Earth. The tendency is for geographers to accept these new data and analysis techniques from engineers and mathematicians without questioning the accompanying premises. This black-box approach hinders geographic applications of the new remotely sensed data and limits the geographer's contribution to further development of remote sensing observation systems. It is suggested that geographers contribute to the development of remote sensing through pursuit of basic research. This research can be encouraged, particularly among students, by demonstrating the links between geographic theory and remotely sensed observations, encouraging a healthy skepticism concerning the current understanding of these data.

Wilson, H.↗
NASA NTRS1983

Sensitivity of ozone retrievals in limb-viewing experiments to errors in line-width parameters

The variance of atmospheric ozone concentration profiles retrieved in i.r. limb-viewing experiments is examined over the range of published ozone halfwidth values. Simulated retrievals are performed for a typical satellite-based high-resolution absorption experiment and a broad-band emission experiment. The results indicate that, for limb-viewing experiments, inaccurate collision-broadened linewidth values can lead to significant errors in retrieved profiles for broad-band radiometric data or for isolated strong lines in high-resolution spectra.

Smith, M. A. H.↗
NASA NTRS1984

Red and near-infrared sensor response to off-nadir viewing

It has first been intended to employ the Advanced Very High Resolution Radiometer (AVHRR) as a meteorological instrument to aid in detecting clouds and atmospheric temperature stratifications over large areas. However, more recently the satellite data have been used for monitoring large areas of vegetation with emphasis on the visible (VIS) and near-infrared (NIR) bands. The present investigation is concerned with the objective to model ranges in AVHRR VIS and NIR radiances and normalized differences expected under typical AVHRR viewing and illumination conditions. Atmospheric data sets reported by Dave (1978) and Dave and Braslau (1975) were used. It is shown that sensor response to atmospheric path length can be substantial for the AVHRR VIS and NIR channels and normalized difference (ND) values. However, errors can be minimized by high sun and clear atmosphere viewing.

Holben, B.↗
NASA NTRS1984

Variation in spectral response of soybeans with respect to illumination, view, and canopy geometry

Comparisons of the spectral response for incomplete (well-defined row structure) and complete (overlapping row structure) canopies of soybeans indicated a greater dependence on Sun and view geometry for the incomplete canopies. Red and near-IR reflectance for the incomplete canopy decreased as solar zenith angle increased for a nadir view angle until the soil between the plant rows was completely shaded. Thereafter for increasing solar zenith angle, the red reflectance leveled off and the near-IR reflectance increased. A 'hot spot' effect was evident for the red and near-IR reflectance factors. The 'hot spot' effect was more pronounced for the red band based on relative reflectance value changes. The ratios of off-nadir to nadir acquired data reveal that off-nadir red band reflectance factors more closely approximated straightdown measurements for time periods away from solar noon. Normalized difference generally approximated straightdown measurements during the middle portion of the day.

Ranson, K. J.↗
NASA NTRS1985

On stereo viewing of SAR images

Stereo viewing is indispensable for the measurement of homologue points in two overlapping images and the subsequent reconstruction of the three-dimensional topographic relief. Aspects of stereo viewing geometry are discussed along with problems of radar stereoscopy, taking into account stereo evaluation with an exaggeration factor, the viewability of real images, and radar stereoscopic computations. Attention is given to the definition of radar stereoscopic exaggeration, questions of image simulation, and the accuracy obtained with parallax measurements in radar images. An evaluation with a large set of about 40 radar stereo models demonstrates that same-side arrangements provide good stereo viewability. This result was confirmed for aircraft radar with look angles off-nadir of 60-80 deg and intersection angles between 0.2 deg and 23 deg, and for satellite radar (Seasat) with look angles of 20 deg and interaction angles of 1.2 deg - 4.8 deg.

Leberl, F. W.↗
NASA NTRS1983

Hot section viewing system

The objective of the hot section viewing program is to develop a prototype optical system for viewing the interior of a gas turbine combustor during high temperature, high pressure operation in order to produce a visual record of some causes of premature hot section failures. The program began by identifying and analyzing system designs that would provide clearest images while being able to survive the hostile environment inside the combustion chamber. Different illumination methods and computer techniques for image enhancement and analysis were examined during a preliminary test phase. In the final phase of the program the prototype system was designed and fabricated and is currently being tested on a high pressure combustor rig.

Morey, W. W.↗
NASA NTRS1986

Orthographic terrain views using data derived from digital elevation models

A fast algorithm for producing three-dimensional orthographic terrain views uses digital elevation data and co-registered imagery. These views are created using projective geometry and are designed for display on high-resolution raster graphics devices. The algorithm's effectiveness is achieved by (1) the implementation of two efficient gray-level interpolation routines that offer the user a choice between speed and smoothness, and (2) a unique visible surface determination procedure based on horizon angles derived from the elevation data set.

Dubayah, R. O.↗