Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “wide-angle”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

An efficient multiplexing approach for adaptive aircraft communications via a relay satellite.

Description of a coherent wide-angle multiplexing approach which is 4 to 8 dB more efficient in the utilization of satellite power as compared to a multicarrier transmission accessing a single TWT amplifier transponder. The wide-angle multiplexing approach achieves this performance by efficiently trading the modulation power improvement against backoff at the satellite earth terminal phase modulator. A simple addition of an amplitude clipper at the modulator input is critical to the proper operation of the system.

Devieux, C.↗
NASA NTRS1977

Optimum coherent imaging of a limited field of view in the presence of angular and aperture noise

The question of image distribution reconstruction for coherent illumination of an object located in the aperture far zone is considered from first principles without postulating any particular optical spread function. The object function is mathematically modeled as a complex random function of angular coordinates, and it is assumed that the object distribution of interest is angularly limited to a certain a priori assigned field of view (FOV). A linear reconstruction procedure that is uniformly optimal in the FOV is established by using the methods of statistical estimation. Two special cases are examined: imaging a limited sector of a wide-angle random scene and objects in the FOV immersed in a wide-angle background of angular noise. It is noted that the domain of application of the reconstruction method is restricted to microwave frequencies.

Borgiotti, G. V.↗
NASA NTRS1970

Drag Characteristics of Several Towed Decelerator Models at Mach 3

An investigation has been made to determine the possibility of using toroid-membrane and wide-angle conical shapes as towed decelerators. Parameter variations were investigated which might render toroid-membrane models and wide-angle- cone models stable without loss of the high drag coefficients obtainable with sting-mounted models. The parameters varied included location of center of gravity, location of the pivot between the towline and the model, and configuration modifications of the aft end as the addition of a corner radius and the addition of a skirt. The toroid membrane can be made into a stable towed decelerator with a suitable configuration modification of the aft end.

EXPERIMENTS↗
NASA NTRS1971

Morphology of poly-p-xylylene crystallized during polymerization.

The morphology of as-polymerized poly-p-xylylene grown between -17 and 30 C is found to consist of lame llar alpha crystals oriented with the (010) plane parallel to the support surface. The crystallinity decreases with decreasing polymerization temperature. Spherulitic and nonspherulitic portions of the polymer film consist of folded chain lamellas with the chain axis parallel to the support surface. The results were obtained by small- and wide-angle X-ray measurements, electron and optical microscopy, and differential thermal analysis.

Kubo, S.↗
NASA NTRS1972

Size frequency distribution of Martian craters and relative age of light and dark terrains.

Light and dark terrains in and around Meridiani Sinus, mapped on the imagery from Mariner 6 and Mariner 7, were found to have significantly different cumulative size frequency distributions of craters. The light terrain on a mosaic of frames 6N11, 6N13, and 6N19 has a greater proportion of large craters and a lesser proportion of smaller craters than the dark terrain on the same frames. The light terrain is interpreted to be generally older than the dark terrain. The filling or partial filling of the smaller craters on the light terrain by surface detritus is suggested. Several wide-angle frames have remarkably similar cumulative crater size frequency distributions that may be representative of a large portion of the Martian surface.

Woronow, A.↗
NASA NTRS1972

Observability of high altitude atmospheric scattering layers

The observability of high altitude aerosol and atmospheric scattering layers by a satellite-mounted optical detector was considered. In particular the detectability of a 50 km layer with a wide-angle receiver was investigated. It was found that a layer possessing an optical depth greater than approximately 0.0002 at 3000 A (i.e. strong enough to affect BUV measurements of ozone) should be detectable with such an instrument provided that the system can be constructed so as to be sensitive to a signal of only 0.0001 of the sunlight directly incident on the instrument. However it was concluded that a narrow field-of-view satellite-mounted telescope used to scan the earth's horizon has a more general applicability for the detection of high altitude aerosol layers.

Cunnold, D. M.↗
NASA NTRS1972

Moving visual scenes influence the apparent direction of gravity.

It is shown that an observer viewing a wide-angled display rotating about its line of sight develops a feeling that his body is tilted and has the illusion that a vertical straight edge is tilted in a direction opposite to that of rotation. Experiments on subjects who monocularly viewed rotating disks with various settings within restricted fields of view are described to substantiate these findings. Displacement of the perceived vertical increased to a maximum of average 15 deg when the stimulus speed increased to 30 deg per sec.

Dichgans, J.↗
NASA NTRS1972

Mariner Mars 1971 photogrammetric calibrations.

One of the major objectives of the Mariner Mars 1971 mission was the systematic mapping of Mars. This required a complex and thorough photogrammetric calibration of both the wide-angle and narrow-angle cameras mounted on the spacecraft scan platform. Because of the peculiarities of the TV imaging techniques (transmission quality, low resolution, electronic distortion, etc.), combined with the extremely small vidicon format, many unique difficulties were encountered and many unprecedented problems had to be solved. Their successful solution, based on experience gained during the Surveyor and Mariner Mars 1969 projects, is discussed, and the calibration procedure for the parameters of interior orientation, as well as for opto-mechanical orthogonality, is described in detail.

Benesh, M.↗
NASA NTRS1973

Millisecond time scale atmospheric light pulses associated with solar and magnetospheric activity.

By using a wide-angle photomultiplier system a class of millisecond time scale diffuse atmospheric light emission of terrestrial origin has been discovered. These fast atmospheric pulsation events also show damped oscillations around 10-kHz frequency, which distinguishes them from ordinary lightning-type events. Evidence is presented for the enhancement in the rate of these events induced by solar flare activity.

Ogelman, H.↗
NASA NTRS1974

Holographic optical elements: Fabrication and testing

The basic properties and use of holographic optical elements were investigated to design and construct wide-angle, Fourier-transform holographic optical systems for use in a Bragg-effect optical memory. The performance characteristics are described along with the construction of the holographic system.

Zech, R. G.↗
NASA NTRS1977

Visual projection reticle

Small lightweight device visually superimposes visual-sensitivity and response contours on displays and instrument panels. Optical system provides 45 deg arc/diameter field of view; however, special wide-angle optics can be substituted without significant size or weight penalty.

Haines, R. F.↗
NASA NTRS1976

Distribution of small channels on the Martian surface

The distribution of small channels on Mars has been mapped from Mariner 9 images at the 1:5,000,000 scale. The small channels referred to here are small valleys ranging in width from the resolution limit of the Mariner 9 wide-angle images (about 1 km) to about 10 km. The greatest density of small channels occurs in dark cratered terrain. This dark zone forms a broad subequatorial band around the planet. The observed distribution may be the result of decreased small-channel visibility in bright areas due to obscuration by a high albedo dust or sediment mantle. Crater densities within two small-channel segments show crater size-frequency distributions consistent with those of the oldest of the heavily cratered plains units. Such crater densities coupled with the almost exclusive occurrence of small channels in old cratered terrain and the generally degraded appearance of small channels in the high-resolution images (about 100 m) imply a major episode of small-channel formation early in Martian geologic history.

Pieri, D.↗
NASA NTRS1976

Design of a Mars entry 'aeroshell'

The external shell of the Project Viking capsule, which will provide atmospheric deceleration for the 1976 landing of an unmanned spacecraft on the surface of Mars, is a wide-angle, stiffened cone subject to buckling under entry aerodynamic pressure. Complex, highly optimized structural prototype and flight designs were evolved through the application of relatively advanced buckling analysis methodology. Both designs were evaluated through tests and analysis with improved shell-of-revolution computer programs. Deviations between the analyses and experiments were resolved only by modeling the thin-walled rings as shell branches. The results illustrate the great complexity of shell behavior and the designer's need for reliable analysis tools capable of representing detailed structural behavior with greater accuracy than is current practice.

Leonard, R. W.↗
NASA NTRS1976

Direct photography of the Gum Nebula

The paper discusses a series of wide-angle photographs taken of the Gum Nebula in the traditional region including H-alpha with the aid of a 40-cm and an 80-cm lens in both the red and the green. The photographs support the large dimensions (75 deg in galactic longitude by 40 deg in galactic latitude) of the Gum Nebula suggested earlier, and the appearance is consistent with an origin due to photons from a supernova outburst. The relatively high-density gas has cooled and is visible on the red plates. The low-density gas has remained at a high temperature and may be visible as diffuse emission on the green plates.

Brandt, J. C.↗
NASA NTRS1977

Combined position and diameter measures for lunar craters

The note addresses the problem of simultaneously measuring positions and diameters of circular impact craters on wide-angle photographs of approximately spherical planets, such as the moon and Mercury. The method allows for situations in which the camera is not aligned on the planet's center.

Arthur, D. W. G.↗
NASA NTRS1977

Radio and optical observations in the fields of five unidentified X-ray sources at high latitudes

Radio observations at 610 MHz and optical plates were obtained for five fields centered on the unidentified X-ray sources 3U0042 + 32, 3U0917 + 63, 3U1443 + 43, 3U1555 + 27, and 3U1809 + 50. For the first three fields, several radio sources are found which are associated with stellar objects within or near the X-ray error boxes. A 'tailed' radio galaxy has been found in Abell 2142, and this cluster is suggested as the identification for 3U1555 + 27. Although there are no radio sources greater than 0.1 flux unit within the X-ray error boxes associated with 3U1809 + 50, a Zwicky cluster surrounding the 3U position contains two radio galaxies: one with an inverted spectrum and another with a wide-angle tail. A table of positions, intensities, and suggested optical identifications is given for the 249 radio sources detected in the five fields.

Harris, D. E.↗
NASA NTRS1977

Voyager imaging experiment

The Voyager imaging experiment, which involves two independently operated television systems (a narrow- and a wide-angle camera), is designed to conduct investigations of the atmospheres and surface properties of Jupiter, Saturn, their satellites and Saturn's rings. Objects of the investigations include the horizontal and vertical structure of visible clouds, the vertical structure of high, optically thin scattering layers on Jupiter and Saturn, the Great Red Spot, the South Equatorial Belt, chromophores on Io and Titan, the geology of several satellites, the masses, spin axes and periods of rotation of several satellites, the radial distribution of material in Saturn's rings, and the optical scattering properties of the primaries, rings, and satellites at a variety of wavelengths and phase angles.

Smith, B. A.↗