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At least 1,027 records · Page 57
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NASA NTRS1993

Data management in NOAA

The NOAA archives contain 150 terabytes of data in digital form, most of which are the high volume GOES satellite image data. There are 630 data bases containing 2,350 environmental variables. There are 375 million film records and 90 million paper records in addition to the digital data base. The current data accession rate is 10 percent per year and the number of users are increasing at a 10 percent annual rate. NOAA publishes 5,000 publications and distributes over one million copies to almost 41,000 paying customers. Each year, over six million records are key entered from manuscript documents and about 13,000 computer tapes and 40,000 satellite hardcopy images are entered into the archive. Early digital data were stored on punched cards and open reel computer tapes. In the late seventies, an advanced helical scan technology (AMPEX TBM) was implemented. Now, punched cards have disappeared, the TBM system was abandoned, most data stored on open reel tapes have been migrated to 3480 cartridges, many specialized data sets were distributed on CD ROM's, special archives are being copied to 12 inch optical WORM disks, 5 1/4 inch magneto-optical disks were employed for workstation applications, and 8 mm EXABYTE tapes are planned for major data collection programs. The rapid expansion of new data sets, some of which constitute large volumes of data, coupled with the need for vastly improved access mechanisms, portability, and improved longevity are factors which will influence NOAA's future systems approaches for data management.

Callicott, William M.↗
NASA NTRS1993

Computation of supersonic jet noise under imperfectly expanded conditions

The turbulent mixing noise of supersonic jet under imperfectly expanded conditions is calculated for convergent and convergent-divergent (CD) axisymmetric nozzle geometries. The noise prediction incorporates CFD solution of Navier-Stokes equations. The effect of grid resolution on shock structure computation is demonstrated. Mixing noise spectra predicted from fine and coarse grid solutions exhibit little sensitivity to the grid resolution. A proper grid resolution, however, results in a significant improvement in shock capturing capability and helps predictions agree favorably with experimental data. Good agreement between predicted noise spectra and data shows that the CFD-incorporated noise prediction scheme, which was demonstrated for shock-free conditions, works as well for shock-containing flow conditions.

Kim, Chan M.↗
NASA NTRS1993

Study of tellurium precipitates in CdTe crystals

The effect of tellurium precipitates was studied in medium resistivity (10 exp 3-10 exp 6 ohm cm) undoped and Cl-doped CdTe using differential scanning calorimetry (DSC) and mid-infrared spectroscopy and the results were correlated with near-infrared microscopy photographs. When present in a significant quantity (about 0.25 wt pct), we show that Te precipitates are detectable using DSC measurements. In the mid-infrared, the contribution of the absorption by free-carriers is negligible, and therefore, the effect of the Te precipitates in these crystals can be considered uncoupled from the effects of Cd vacancies.

Jayatirtha, H. N.↗
NASA NTRS1993

Far-infrared emission from the intracluster medium

IRAS images of 56 clusters of galaxies are examined for evidence of diffuse, extended FIR emission at 60 and 100 microns. Of these 56 clusters, five show evidence of FIR excess, but at low levels of significance. For A496 and MKW 1, this excess is attributable to the presence of a strong point source at or near the position of the central cD galaxy. In A2344, the observed 100-micron excess is the result of the presence of a foreground cirrus concentration which coincides with the cluster. Examination of the sample as a whole indicates that clusters exhibit excess FIR emission at the 2-sigma level for apertures 4 and 10 arcmin in diameter. FIR luminosities range from about 1-0 exp 9 solar luminosities for the smallest aperture to about 10 exp 14 solar luminosities for the entire cluster.

Wise, Michael W.↗
NASA NTRS1993

BL Lacertae objects, Fanaroff-Riley type I radio sources, and cluster cooling flows

The correctness of the view that the Fanaroff-Riley type I (F-R I) radio galaxies and the BL Lac objects are intrinsically the same and that the strong emission seen in BL Lac may be the result of beaming of radiation from the galactic nucleus is examined. Expressions are derived for the surface brightness of scattered beams of polarized or unpolarized radiation, and the expected scattered light surface is calculated assuming the beams have spectra and fluxes consistent with those observed for BL Lac objects. The models are compared to recent observations of lobes of excess, polarized blue light in Cy-A, and observations of lobes of UV light in the central regions of the cD galaxies in A1795 and A2597. It was found that the models predict scattered surface brightnesses in reasonable agreement with those observed. If these lobes are indeed scattered light, this would indicate that F-R I radio galaxies do possess beams of radiation with apparent luminosities similar to BL Lac objects and that the radiation is actively beamed and not merely obscured by a torus of dust around the nucleus.

Sarazin, Craig L.↗
NASA NTRS1993

Fluidic scale model multi-plane thrust vector control test results

An experimental investigation has been conducted at the NASA Langley 16-Foot Transonic Tunnel Static Test Facility to determine the concept feasibility of using fluidics to achieve multiplane thrust vector control in a 2D convergent-divergent (2D-CD) fixed aperture nozzle. Pitch thrust vector control is achieved by injection of flow through a slot in the divergent flap into the primary nozzle flow stream. Yaw vector control results from secondary air delivered tangentially to vertical Coanda flaps. These flaps are offset laterally and aligned parallel to the primary nozzle side walls. All tests were conducted at static (no external flow) conditions. Flow visualization was conducted using a paint flow technique and Focus Schlieren. Significant levels of pitch deflection angles (19 deg) were achieved at low pressure ratios and practical levels (14 deg) resulted at typical intermediate power settings. The ability of the Coanda surface blowing concept to produce yaw deflection was limited to NPR not greater than 4.

Chiarelli, Charles↗
NASA NTRS1993

Electronic characterization of defects in narrow gap semiconductors

The study of point defects in semiconductors has a long and honorable history. In particular, the detailed understanding of shallow defects in common semiconductors traces back to the classic work of Kohn and Luttinger. However, the study of defects in narrow gap semiconductors represents a much less clear story. Here, both shallow defects (caused by long range potentials) and deep defects (from short range potentials) are far from being completely understood. In this study, all results are calculational and our focus is on the chemical trend of deep levels in narrow gap semiconductors. We study substitutional (including antisite), interstitial and ideal vacancy defects. For substitutional and interstitial impurities, the efects of relaxation are included. For materials like Hg(1-x)Cd(x)Te, we study how the deep levels vary with x, of particular interest is what substitutional and interstitial atoms yield energy levels in the gap i.e. actually produce deep ionized levels. Also, since the main technique utilized is Green's functions, we include some summary of that method.

Patterson, James D.↗
NASA NTRS1993

Progress in p(+)n InP solar cells fabricated by thermal diffusion

The performance results of our most recently thermally diffused InP solar cells using the p(+)n (Cd,S) structures are presented. We have succeeded in fabricating cells with measured AMO, 25 C V(sub oc) exceeding 880 mV (bare cells) which to the best of our knowledge is higher than previously reported V(sub oc) values for any InP homojunction solar cells. The cells were fabricated by thinning the emitter, after Au-Zn front contacting, from its initial thickness of about 4.5 microns to about 0.6 microns. After thinning, the exposed surface of the emitter was passivated by a thin (approximately 50A) P-rich oxide. Based on the measured EQY and J(sub sc)-V(sub oc) characteristics of our experimental high V(sub oc) p(+)n InP solar cells, we project that reducing the emitter thickness to 0.3 microns, using an optimized AR coating, maintaining the surface hole concentration of 3 x 10(exp 18)cm(sup -3), reducing the grid shadowing from actual 10.55 percent to 6 percent and reducing the contact resistance will increase the actual measured 12.57 percent AMO 25 C efficiency to about 20.1 percent. By using our state-of-the-art p(+)n structures which have a surface hole concentration of 4 x 10(exp 18)cm(sup -3) and slightly improving the front surface passivation, an even higher practically achievable AMO, 25 C efficiency of 21.3 percent is projected.

Flood, D. J.↗
NASA NTRS1993

Crystal growth of ZnSe and related ternary compound semiconductors by physical vapor transport

The materials to be investigated are ZnSe and related ternary semiconducting alloys (e.g., ZnS(x)Se(1-x), ZnTe(x)Se(1-x), and Zn(1-x)Cd(x)Se). These materials are useful for opto-electronic applications such as high efficient light emitting diodes and low power threshold and high temperature lasers in the blue-green region of the visible spectrum. The recent demonstration of its optical bistable properties also makes ZnSe a possible candidate material for digital optical computers. The investigation consists of an extensive ground-based study followed by flight experimentation, and involves both experimental and theoretical work. The objectives of the ground-based work are to establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low gravity environment and to obtain the experimental data and perform the analyses required to define the optimum parameters for the flight experiments. During the six months of the Preliminary Definition Phase, the research efforts were concentrated on the binary compound ZnSe - the purification of starting materials of Se by zone refining, the synthesis of ZnSe starting materials, the heat treatments of the starting materials, the vapor transport rate measurements, the vapor partial pressure measurements of ZnSe, the crystal growth of ZnSe by physical vapor transport, and various characterization on the grown ZnSe crystals.

Su, Ching-Hua↗
NASA NTRS1993

Determining the locations of the various CIRC recording format information blocks (user data blocks, C2 and C1 words and EFM frames) on a recorded compact disc

Just prior to its being EFM modulated (i.e., converted to eight-to-fourteen channel data by the EFM encoder) and written to a Compact Disc (CD), information that passes through the CIRC Block Encoder is grouped into 33-byte blocks referred to as EFM frames. Twenty four of the bytes that make up a given EFM frame are user data that was input into the CIRC encoder at various (different) times, 4 of the bytes of this same EFM frame were created by the C2 ECC encoder (each at a different time), and another 4 were created by the C1 ECC encoder (again, each at a different time). The one remaining byte of the given EFM frame, which is known as the EFM frame C&D (for Control & Display) byte, carries information that identifies which portion of the current disc program track the given EFM frame belongs to and also specifies the location of the given EFM frame on the disc (in terms of a time stamp that has a resolution of l/75th second, or 98 EFM frames). (Note: since the program track and time information is stored as a 98-byte word, a logical group consisting of 98 consecutive EFM frames must be read, and their respective C&D bytes must be catenated and decoded, before the program track identification and time position information that pertains to the entire block of 98 EFM frames can be obtained.) The C&D byte is put at the start (0th byte) of an EFM frame in real time; its placement completes the construction of the EFM frame - it is assigned just before the EFM frame enters the EFM encoder. Four distinct blocks of data are referred to: 24-byte User Input Data Blocks; 28-byte C2 words; 32-byte C1 words; and 33-byte EFM frames.

Howe, Dennis G.↗
NASA NTRS1993

Global and regional/seasonal color mosaics of Mars

Four regional mosaics of Mars acquired during different seasons, along with their composite as a single global mosaic, have been completed in two colors (red and violet) at scales of 1/16 and 1/64 degrees/pixel. These mosaics were put together from a set of 51 separate mosaics, each acquired from a single Viking orbiter spacecraft orbital revolution. Special techniques were developed and applied to suppress large variations between mosaics introcued by highly variable, optically thin, condensate hazes. The techniques utilize a combination of the spatial characteristics of the hazes (generally broad, low-frequency) along with their modulation of the reginal color ratios (strongly enhancing the violet/red ratios). Photometric-function normalization was applied following the haze removal. Most of the single-orbit mosaics consist of red and violet or red, green, and violet filters, but a few mosaics with only red-filter data were included to fill gaps in global coverage at high northern latitudes. Global coverage is approximately 99 percent complete in red-filter mosaics and approximately 95 percent and approximately 60 percent complete in corresponding violet- and green-filter mosaics, respectively. All of the mosaics are geometrically tied to the 1/256 deg per pixel Mars Digital Image Map (MDIM), which is available on Compact Disk (CD), and which will be used as the base map for Mars Observer data sets. Early in 1993, the single-orbit color mosaics will be distributed to the science community in a six-volume set of CDs. Perhaps the most scientifically interesting parts of this dataset are the overlap regions, which show significant temporal variations in surface and atmospheric features. Surface changes can be categorized as (1) changes that probably occurred during the great dust storms of 1977; (2) changes that occurred soon after 1977 storms due to removal of redistribution of recently deposited dust; (3) changes in the northern lowlands that probably occurred during the dusty southern summer of 1979 (when no great dust storm occurred); and (4) changes associated with strong slope winds in the Tharsis and Elysium regions.

Mcewen, Alfred S.↗
NASA NTRS1993

Initial development of a high-pressure crystal growth facility: Center director's discretionary fund

A low-cost, flexible, high-pressure (600 psi) system for crystal growth and related thermophysical properties measurements was designed, assembled, and tested. The furnace system includes a magnetically coupled translation mechanism that eliminates the need for a high-pressure mechanical feedthru. The system is currently being used for continuing crystal growth experiments and thermophysical properties measurements on several material systems including Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se.

Szofran, F. R.↗
NASA NTRS1992

Guide star catalogue data retrieval software 2

The Guide Star Catalog (GSC), being the largest astronomical catalog to date, is widely used by the astronomical community for all sorts of applications, such as statistical studies of certain sky regions, searches for counterparts to observational phenomena, and generation of finder charts. It's format (2 CD-ROM's) requires minimum hardware and is ideally suited for all sorts of conditions, especially observations. Unfortunately, the actual GSC data is not easily accessible. It takes the form of FITS tables, and the coordinates of the objects are given in one coordinate system (equinox 2000). The included reading software is rudimentary at best. Thus, even generation of a simple finder chart is not a trivial undertaking. To solve this problem, at least for PC users, GUIDARES was created. GUIDARES is a user-friendly program that lets you look directly at the data in the GSC, either as a graphical sky map or as a text table. GUIDARES can read a sampling of GSC data from a given sky region, store this sampling in a text file, and display a graphical map of the sampled region in projected celestial coordinates (perfect for finder charts). GUIDARES supports rectangular and circular regions defined by coordinates in the equatorial, ecliptic (any equinox) or galactic systems.

Smirnov, O. M.↗
NASA NTRS1992

UIT support observations archive

We are in the process of archiving the approximately 1.2Tbytes of imaging data acquired in support of UIT observations. The UIT is one of three telescopes comprising the ASTRO spacecraft and is a 38-cm f/9 Ritchey-Chretien telescope with wavelength coverage 1200 A to 3000 A and a 40 arcminute diameter field-of-view at 4 min FWHM resolution. During the ASTRO shuttle mission, there were 65 different pointings (some with multiple targets) of the UIT and hence 65 fields. Our support data of these fields were obtained with the KPNO and CTIO 0.9m telescopes and several of the 2048x2048 CCD's. Our images are typically about 20 acrminutes on a side and contain the entire UV target except for nearby galaxies, for which mosaiced images were created. All good quality images in the broadband and narrow band filters for every target are being archived. Though all of the UIT targets were well studied astronomical objects, these frames are many of the first large field format images of them and, when combined with the soon to be released UV frames, provide a unique dataset. These data were already used to address a wide variety of astronomical questions. Vacuum ultraviolet (VUV) observations were used to study star formation in a sample of nearby galaxies, since integrated VUV - optical colors provide the most sensitive available measure of the formation rate of massive stars. The blue stages later in stellar evolution are also being studied. These data allow more accurate determination of the helium and metallicities of hothorzontal branch stars. These data are being prepared to release to the public in CD-ROM format through the National Space Science Data Center.

Smith, Eric P.↗
NASA NTRS1992

Hardware design of a spherical mini-rover

In this hardware project the students designed the prototype of a novel mini-rover for the exploration of a planetary surface. In an actual application, a large number of such miniature roving devices would be released from a landing craft. Each rover would be equipped with a Cd 109 radio-isotope source (a gamma ray emitter) irradiating the planetary surface below the rover, and an x-ray fluorescence detector for a quantitative assay of high atomic weight elements in the planet's surface. (Similar, miniaturized, hand-held devices have recently been developed for use in gold mines). The device developed by the students was limited to demonstrating the mechanical and electrical drive. The geometric external shape is a sphere; hence there is no danger of the rover being turned on its back and stopped. Propulsion is by means of an interior mass, eccentric to the sphere and driven by an electric motor. In an inter-disciplinary effort in mechanical and electrical engineering, the students designed the mechanical parts, built the transistorized circuit board, and tested the device.

Tarlton, John↗
NASA NTRS1994

Determination of thermal properties of commercial Ni-MH cells

The test objectives were to evaluate the electrical and thermal performance of commercial Ni-MH cells, evaluate the effectiveness of commercial charge control circuits, assess the abuse tolerance of these cells, and correlate performance and abuse tolerances to cell design via disassembly. Design objectives were to determine which cell designs are most suitable for scale-up and to guide the design of future shuttle and space station based battery chargers. Results, displayed in viewgraph format, include: reflex charging with ICS circuit resulted in premature charge termination; Ni-MH cells appear very tolerant to overcharge at low rates; Enstore's charger is more electrically and thermally efficient at high rates; and Ni-MH cycles much more efficiently than Ni-Cd with the delta-V/delta-t termination.

Darcy, Eric C.↗
NASA NTRS1993

Cellular polarity and interactions in plant graviperception

Presented are results of studies on the mechanisms of gravitropic sensing in higher and lower plants. Gravitropic roots of the aquatic angiosperm, Limnobium, were found to have sedimented amyloplasts in their elongation zone but not in their rootcap; nuclei were found to sediment in the elongation zone as well. Another study attempted to understand how plastid sedimentation occurs in vertical Ceratodon cells and how this sedimentation is regulated. To determine whether the cytoskeleton restricts plastid sedimentation, the effects of amiprophos-methyl (APM) and cytochalasin (CD) on plastid position were qualified. Results suggest that microtubules restrict the sedimentation of plastids along the length of the cell and that microtubules are load-bearing for all the plastids in the apical cell, demonstrating the importance of the cytoskeleton in maintaining organelle position and cell organization against the force of gravity. Physcomitrella and Funaria were also studied. Results suggest that gravitropism may be relatively common in moss protonemata and reinforce the idea that amyloplast mass functions in gravitropic sensing.

Sack, Fred D.↗
NASA NTRS1992

High speed jet noise research at NASA Lewis

The source noise portion of the High Speed Research Program at NASA LeRC is focused on jet noise reduction. A number of jet noise reduction concepts are being investigated. These include two concepts, the Pratt & Whitney ejector suppressor nozzle and the General Electric (GE) 2D-CD mixer ejector nozzle, that rely on ejectors to entrain significant amounts of ambient air to mix with the engine exhaust to reduce the final exhaust velocity. Another concept, the GE 'Flade Nozzle' uses fan bypass air at takeoff to reduce the mixed exhaust velocity and to create a fluid shield around a mixer suppressor. Additional concepts are being investigated at Georgia Tech Research Institute and at NASA LeRC. These will be discussed in more detail in later figures. Analytical methods for jet noise prediction are also being developed. Efforts in this area include upgrades to the GE MGB jet mixing noise prediction procedure, evaluation of shock noise prediction procedures, and efforts to predict jet noise directly from the unsteady Navier-Stokes equation.

Krejsa, Eugene A.↗