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At least 1,513 records · Page 84

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NASA NTRS1980

The reduction, verification and interpretation of Magsat magnetic data over Canada

The primary concern of this investigation is to detect and study variations in the magnetic field originating in the solid Earth, as measured by Magsat. Most of this field originates in the core, but an important part of the field is of lithospheric origin. Magnetic anomalies of lithospheric origin are weak at Magsat altitudes (20 to 30 nT at most), and they can easily be masked by much larger effects caused by field aligned and other currents at high latitudes. Most of Canada lies under the influence of ionospheric currents in the auroral zone and polar cap. Therefore, before Magsat data had become available, but after the October 30, 1979 launch, criteria were developed for selecting times when subsets of potentially usable Magsat data could be expected. Subsequently, as Magsat data became available, these critieria were applied.

Coles, R. L.↗

NASA NTRS1980

Short-circuit current improvement in thin cells with a gridded back contact

The use of gridded back contact on thin silicon solar cells 50 micrometers was investigated. An unexpected increase in short circuit current of almost 10 percent was experienced for 2 cm x 2 cm cells. Control cells with the standard continuous contact metallization were fabricated at the same time as the gridded back cells with all processes identical up to the formation of the back contact. The gridded back contact pattern was delineated by evaporation of Ti-Pd over a photo-resist mask applied to the back of the wafer; the Ti-Pd film on the controls was applied in the standard fashion in a continuous layer over the back of the cell. The Ti-Pd contacts were similarly applied to the front of the wafer, and the grid pattern on both sides of the cell was electroplated with 8-10 micrometers of silver.

Giuliano, M.↗

NASA NTRS1981

Ion beam sputter etching of orthopedic implanted alloy MP35N and resulting effects on fatigue

The effects of two types of argon ion sputter etched surface structures on the tensile stress fatigue properties of orthopedic implant alloy MP35N were investigated. One surface structure was a natural texture resulting from direct bombardment by 1 keV argon ions. The other structure was a pattern of square holes milled into the surface by a 1 keV argon ion beam through a Ni screen mask. The etched surfaces were subjected to tensile stress only in fatigue tests designed to simulate the cyclic load conditions experienced by the stems of artificial hip joint implants. Both types of sputter etched surface structures were found to reduce the fatigue strength below that of smooth surface MP35N.

Wintucky, E. G.↗

NASA NTRS1981

Analysis of data from Viking RPA's

Measurements of the martian ionosphere performed by Viking Retarding Potential Analyzer (RPA) are reported. Viking RPA measurements of low energy electron fluxes out to 16,000 km above the Mars surface are discussed including both energy spectra and periods of continuous monitoring of the total flux above 15 ev. The mean electron current at energies greater than ev increases montonically by nearly two orders of magnitude from about 9000 km down to 700 km, but no clear signature of the bow shock is seen. The total wave power in the 2 sec measurement intervals for this current does, however, show a broad peak near 1700 km altitude. These variations in the low energy electron fluxes are related to whistler mode oscillations in the solar wind plasma. It is concluded that there may be a highly turbulent shock structure that masks a clear signature of the bow shock in the time averaged data.

Hanson, W. B.↗

NASA NTRS1981

Pinhole-coronograph tracking control

The pinhole occulter system, a space shuttle based experiment for the production of hard X-ray images taken primarily from the Sun is described. The system is a pinhole camera utilizing a deployable 50 m flexible boom for separating the pinhole from the recording devices located in the shuttle. The system is subjected to the disturbances of the shuttle. The worst of these are thruster firing for orbit correction, man motion, motion induced by other systems, and gravity gradient torques. The control system of the pointing mount senses both position and velocity of the mask tip and uses these to estimate accurately the flexible modes of the system.

Greene, M.↗

NASA NTRS1979

The MSFC complementary metal oxide semiconductor (including multilevel interconnect metallization) process handbook

The fabrication techniques for creation of complementary metal oxide semiconductor integrated circuits at George C. Marshall Space Flight Center are described. Examples of C-MOS integrated circuits manufactured at MSFC are presented with functional descriptions of each. Typical electrical characteristics of both p-channel metal oxide semiconductor and n-channel metal oxide semiconductor discrete devices under given conditions are provided. Procedures design, mask making, packaging, and testing are included.

Bouldin, D. L.↗

NASA NTRS1981

X-ray photoemission studies of superficially oxidized cesium antimonide photoemitters

Superficially oxidized cesium antimonide photoemitting surfaces prepared in ultrahigh vacuum were studied by X-ray photoelectron spectroscopy. Oxidation of Cs3Sb to produce a surface with enhanced photosensitivity converts part of the antimony to elemental antimony and part of the cesium to cesium suboxide. The latter is identified on the basis of an O1 s peak at 531.3 eV, characteristic of Cs11O3. The production of Cs2O is not ruled out in this process since its signature at 527.5 eV is masked by an antimony shake-up peak at 527 eV.

Bates, C. W., Jr.↗

NASA NTRS1980

An all-plated, low cost contact system for silicon solar cells

The plating sequences Pd-Cr-Cu and Pd-Ni-Cu are demonstrated. The surface was sensitized with a 50 A-thick Pd layer obtained from an immersion bath. After 15 min heating at 400 C in N2, a thin barrier layer of either Cr or Ni was deposited from electroless baths operated at temperatures around 90 C. The sintering process was repeated, and a thin copper layer of 500 A was deposited by electroless means. An electrolytic copper bath was used to build the copper layer to 3-4 micron thicknesses. Cells with good I-V curves were obtained, and the all-plated contacts had good adhesion. Preliminary cost estimates show that the process costs approximately 12 cents per watt excluding the cost of the masking procedure.

Tanner, D. P.↗

NASA NTRS1981

A new CT collimator for producing two simultaneous overlapping slices from one scan

A new CT collimator is developed which is capable of producing two simultaneous successive overlapping images from a single scan. The collimator represents a modification of the standard EMI 5005 collimator achieved by alternately masking one end or portions of both ends of the X-ray detectors at a 13-mm beamwidth so that a set of 540 filtered projections is obtained for each scan which can be separated into two sets of interleaved projections corresponding to views 3 mm apart. Tests have demonstrated that the quality of the images produced from these two projections almost equals the quality of those produced by the standard collimator from two separate scans. The new collimator may thus be used to achieve a speed improvement in the generation of overlapping sections as well as a reduction in X-ray dosage.

Kwoh, Y. S.↗

NASA NTRS1982

Plating To Reinforce Welded Joints

Electrodeposition used to strengthen welded joints gouged, nicked, or suffered other mechanical damage. Plating cell, typically of acrylic plastic such as poly (Methylmetacrylate), is assembled around part to be plated. Areas not to be plated are masked with plater's tape. Weld area is plated in standard nickel-plating process.

Otousa, J. E.↗

NASA NTRS1981

Dynamic Moire Methods for Detection of Loosened Space Shuttle Tiles

Moire fringe methods for detecting loose space shuttle tiles were investigated with a test panel consisting of a loose tile surrounded by four securely bonded tiles. The test panel was excited from 20 to 150 Hz with in-plane sinusoidal acceleration of 2 g (peak). If the shuttle orbiter can be subjected to periodic excitation of 1 to 2 g (peak) and rigid-body periodic displacements do not mask the change in the Moire pattern due to tile looseness, then the use of projected Moire fringes to detect out-of-plane rockin appears to be the most viable indicator of tile looseness since no modifications to the tiles are required.

Snow, W. L.↗

NASA NTRS1982

High temperature LSI

Integrated injection logic (1,2) technology for reliable operation under a -55 C to +300 C, temperature range is discussed. Experimental measurements indicate that an 80 mv signal swing is available at 300 C with 100 micro A injection current per gate. In addition, modeling results predict how large gate fan-ins can decrease the maximum thermal operational limits. These operational limits and the longterm reliability factors associated with device metallization are evaluated via specialized test mask.

Dening, D. C.↗

NASA NTRS1981

The reduction, verification and interpretation of Magsat magnetic data over Canada

Magnetic anomalies of lithospheric origin are weak at Magsat altitudes (20 to 30 nT at most), and are easily masked by much larger effects caused by field-aligned and other currents at high latitudes. Most of Canada lies under the influence of ionospheric currents in the auroral zone and polar cap. A more refined selection of quiet Magsat data allowed a revised scalar magnetic anomaly map of the whole region north of about 40 deg N latitude. Very preliminary vector anomaly maps and absolute vector component maps were derived. The scalar magnitudes show great promise for mapping the total force and anomaly fields. The Z vector data also appear to be good. The horizontal X and Y vector data are seriously contaminated with external fields and maybe other effects.

Coles, R. L.↗

NASA NTRS1981

Optical implementation of systolic array processing

Algorithms for matrix vector multiplication are implemented using acousto-optic cells for multiplication and input data transfer and using charge coupled devices detector arrays for accumulation and output of the results. No two dimensional matrix mask is required; matrix changes are implemented electronically. A system for multiplying a 50 component nonnegative real vector by a 50 by 50 nonnegative real matrix is described. Modifications for bipolar real and complex valued processing are possible, as are extensions to matrix-matrix multiplication and multiplication of a vector by multiple matrices.

Caulfield, H. J.↗

NASA NTRS1980

Spatial thermal radiometry contribution to the Massif Armoricain and the Massif Central France litho-structural study

Thermal zones delimited on HCMM images, by visual interpretation only, were correlated with geological units and carbonated rocks, granitic, and volcanic rocks were individualized rock signature is evolutive parameter and some distinctions were made by addition of day, night and seasonal thermal image interpretation. This analysis also demonstrated that forest cover does not mask the underlying rocks thermal signature. Thermal linears are associated with known tectonics but the observed thermal variations from day to night and from one to another represent a promising concept to be studied in function of neotectonics and hydrogeology. The thermal anomalies discovered represent a potential interest which is to be evaluated. Significant results were obtained in the Mont Dore area and additional geological targets were defined in the Paris Basin and the Montmarault granite.

Scanvic, J. Y.↗

NASA NTRS1981

Anthropometric data error detecting and correction with a computer

Data obtained with automated anthropometric data aquisition equipment was examined for short term errors. The least squares curve fitting technique was used to ascertain which data values were erroneous and to replace them, if possible, with corrected values. Errors were due to random reflections of light, masking of the light rays, and other types of optical and electrical interference. It was found that the signals were impossible to eliminate from the initial data produced by the television cameras, and that this was primarily a software problem requiring a digital computer to refine the data off line. The specific data of interest was related to the arm reach envelope of a human being.

Chesak, D. D.↗

NASA NTRS1982

Elastic suspension of a wind tunnel test section

Experimental verification of the theory describing arbitrary motions of an airfoil is reported. The experimental apparatus is described. A mechanism was designed to provide two separate degrees of freedom without friction or backlash to mask the small but important aerodynamic effects of interest.

Hacker, R.↗

NASA NTRS1980

Spatial thermal radiometry contribution to the Massif Armoricain and the Massif Central (France) litho-structural study

Scanvic, J. Y.↗