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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Interpreting vegetation reflectance measurements as a function of solar zenith angle

Spectral hemispherical-conical reflectances of a nadir looking sensor were taken throughout the day for a lodgepole pine and two grass canopies. Mathematical simulations of both spectral hemispherical-conical and bi-hemispherical reflectances were performed for two theoretical canopies of contrasting geometric structure. These results and comparisons with literature studies showed a great amount of variability of vegetation canopy reflectances as a function of solar zenith angle. Explanations for this variability are discussed and recommendations for further measurements are proposed.

Kimes, D. S.↗
NASA NTRS1978

Lines in the 2736-3303 A spectrum of Arcturus

Results are reported for a study of the near-UV spectrum of Arcturus as recorded with a balloon-borne echelle spectrograph-vidicon detector system in the spectral region from 2700 to 3300 A at 0.1-A resolution. A condensed version of the Arcturus spectrum is provided along with profile descriptions and identifications for 383 absorption features detected in the near-UV. Elements definitely present include Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, and La. Elements with spectral features indicating possible presence include Be, O, S, K, Ga, Ge, Nb, Sn, Gd, and Bi. Line blocking is shown to be extensive in the spectral region studied, and eight possible continuum 'windows' are found in the near-UV. Emission lines of chromospheric origin due to Mg II, Fe I, Fe II, and possibly Cr II are also identified in the region from 2736 to 3303 A. It is noted that the Fe I emission lines at 2823 and 2844 A are optically pumped.

Stencel, R. E.↗
NASA NTRS1978

Growth parameters for aligned microstructures in directionally solidified aluminum-bismuth monotectic

Microstructures are shown for directionally solidified Al-3.4 wt pct Bi alloys with 0.2 wt pct Fe and 0.6 wt pct Fe additions. The third element causes the LI/SI + LII growth interface to become cellular. The bismuth forms at the cell nodes, appearing either as uniformly spaced arrays of spheres in the case of 0.2 wt pct Fe, or as an irregular network in the case of 0.6 wt pct Fe. Changes in the growth conditions which are known to control cellular structure are seen to have a similar effect on the bismuth spacing, with the cross sectional spacing varying as the inverse of G (Temperature gradient) x R(Growth rate).

Parr, R. A.↗
NASA NTRS1979

Thermodynamics of selected trace elements in the Jovian atmosphere

The thermochemistry of several hundred compounds of twelve selected trace elements (Ge, Se, Ga, As, Te, Pb, Sn, Cd, Sb, Tl, In, and Bi) has been investigated for solar composition material along a Jupiter adiabat. The results indicate that AsF3, InBr, TlI, and SbS, in addition to CO, PH3, GeH4, AsH3, H2Se, HCl, HF, and H3BO3 proposed by Barshay and Lewis (1978), may be potential chemical tracers of atmospheric dynamics. The reported observation of GeH4 is interpreted on the basis of new calculations as implying rapid vertical transport from levels where the temperature is greater than or equal to 800 K. Upper limits are also set on the abundances of many gaseous compounds of the elements investigated.

Fegley, B., Jr.↗
NASA NTRS1979

On mobile element transport in heated Abee

Abee chondrite samples were heated at 700 C for one week at 0.00001 to 0.001 atm Ne or at 0.00001 atm H2. Samples heated in Ne showed greater loss of Bi and Se and greater retention of Zn than those heated in H2. An inverse relationship between Zn retention and ambient Ne pressure was found. Seven trace elements (Ag, Co, Cs, Ga, In, Te, and Tl) were retained or lost to the same extent regardless of the heating conditions. Variations in the apparent activation energy for C above and below 700 C suggest that diffusive loss from different hosts and/or different mobile transport processes over the temperature range may have been in effect.

Ikramuddin, M.↗
NASA NTRS1978

The NASA Standard Telemetry and Command Components /STACC/

The Standard Telemetry and Command Components (STACC) were conceived by NASA for use on the Multimission Modular Spacecraft. The components have wider application, however, and already are being considered for many other spacecraft. A programmable Central Unit controls Remote Interface Units via a full duplex data bus, providing data acquisition and command distribution capability throughout the spacecraft. The Central Unit can meet any uplink, time code, and format requirements without hardware changes. Each remote unit can acquire any type of data (serial digital, bi-level, analog, or passive analog) on any channel. A third type of unit is an optional interface providing I/O capability to an on-board computer. The protocols used on the 1Mbps data bus are compatible with MSFC's 'Standard Interfaces for Digital Data, Multiplex Serial Data Acquisition and Distribution Systems (SIDD/MSDADS Standard)'. The bus design saves significant harness weight and simplifies the single point ground and isolation approaches.

Elliott, N. P.↗
NASA NTRS1978

Meteoritic material in lunar highland samples from the Apollo 11 and 12 sites

Radiochemical neutron activation analyses for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Te, Tl, U and Zn were carried out on 11 samples from the Apollo 11 and 12 sites (two samples of rock 12013, one granitic and one KREEPy; 4 KREEP fragments from 2-4 mm soil 12033,2; 4 anorthositic fragments from 1-3 mm soil 10085,104; 1 sample of 'Luny' rock-felsite-KREEP breccia 12013 10085,31 LR-1). Most Apollo 12 samples were found to have an Imbrium meteoritic component; others, typified by the Luny breccia, apparently contain a new meteoritic component of low Re content. Components of higher Ir/Au ratio (3L, 5L and 7) were found in Apollo 11 anorthositic samples; the fact that their enrichment in meteoritic siderophiles parallels that of Fe, Mg, REE and other KREEP elements is consistent with progressive contamination of an anorthositic crust. The Luny rock was tentatively classified Group 2, supporting the assignment of this group to Serenitatis.

Janssens, M.-J.↗
NASA NTRS1979

Isotopic anomalies of noble gases in meteorites and their origins. IV - C3 /Ornans/ carbonaceous chondrites

The C3O chondrites Kainsaz, Lance, and Ornans were studied by an acid dissolution technique to characterize the noble gas components in 3 mineral fractions: HF, HCl-solubles, chromite and carbon, and 'phase Q', a trace mineral containing Ar, Kr, Xe. For all fractions, gas contents decline in the order Kainsaz, Lance, Ornans; this trend parallels volatile contents but not heterogeneity of olivine composition or degree of metamorphism, and reflects progressively higher condensation temperature from the solar nebula. The Ar/Xe ratios and compositions of the three mineral fractions are discussed, and it is concluded that in all primitive chondrites the amount and the chemical separability of CCFXe parallel the abundance of primordial noble gases and other volatiles, such as C, N, Tl, Bi, and In. The close correlation of CCFXe with properties of local origin, such as volatile content and petrologic type, is more consistent with a local than with an extrasolar origin of the component.

Alaerts, L.↗
NASA NTRS1979

On volatile element trends in gas-rich meteorites

Study of 10 volatile elements (and non-volatile Co) in co-existing light and dark portions of 6 gas-rich chondrites indicates patterns of distinct but non-uniform enrichment of volatile elements. Only Cs is enriched in all samples; Bi and Tl enrichments covary. The observed enrichments are inconsistent with prior suggestions of admixture of C1 or C2 chondritic matter, whether pristine or partly devolatilized, but suggest that both light and dark portions of each chondrite represents a compositionally more extended sampling of parental nebular material than hitherto known.

Bart, G.↗
NASA NTRS1980

Ultramicrowave communications system, phase 2

Communications system design was completed and reviewed. Minor changes were made in order to make it more cost effective and to increase design flexibility. System design activities identified the techniques and procedures to generate and monitor high data rate test signals. Differential bi-phase demodulation is the proposed method for this system. The mockup and packaging designs were performed, and component layout and interconnection constraints were determined, as well as design drawings for dummy parts of the system. The possibility of adding a low cost option to the transceiver system was studied. The communications program has the advantage that new technology signal processing devices can be readily interfaced with the existing radio frequency subsystem to produce a short range radar.

Source record↗
NASA NTRS1980

Preliminary design data package, appendices C1 and C2

The HYBRID2 program which computes the fuel and energy consumption of a hybrid vehicle with a bi-modal control strategy over specified component driving cycles is described. Fuel and energy consumption are computed separately for the two modes of operation. The program also computes yearly average fuel and energy consumption using a composite driving cycle which varies as a function of daily travel. The modelling techniques are described, and subroutines and their functions are given. The composition of modern automobiles is discussed along with the energy required to manufacture an American automobile. The energy required to scrap and recycle automobiles is also discussed.

Source record↗
NASA NTRS1980

On the chemical composition of L-chondrites

Radiochemical neutron activation analysis of Ag, As, Au, Bi, Co, Cs, Ga, In, Rb, Sb, Te, Tl, and Zn and major element data in 14 L4-6 and 3 LL5 chondrites indicates that the L group is unusually variable and may represent at least 2 subgroups differing in formation history. Chemical trends in the S/Fe rich subgroup support textural evidence indicating late loss of a shock formed Fe-Ni-S melt; the S/Fe poor subgroup seemingly reflects nebular fractionation only. Highly mobile In and Zn apparently reflect shock induced loss from L chondrites. However, contrasting chemical trends in several L chondrite sample sets indicate that these meteorites constitute a more irregular sampling of, or more heterogeneous parent material than do carbonaceous or enstatite chondrites. Data for 15 chondrites suggest higher formation temperatures and/or degrees of shock than for LL5 chondrites.

Neal, C. W.↗
NASA NTRS1980

Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413K

The pressure dependence of absolute rate constants for the reaction of OH + C2H2 yields products has been examined at five temperatures ranging from 228 to 413 K. The experimental techniques which was used is flash photolysis-resonance fluoresence. OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is 4 x 10 the the minus 13th power cu cm molecule (-1) s(-1) over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (k sub bi) sub infinity = (6.83 + or - 1.19) x 10 to the minus 12th power exp(-646 + or - 47/T)cu cm molecule (-1) s(-1). The results are compared to previous investigated and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.

Michael, J. V.↗
NASA NTRS1979

Breccias 73215 and 73255 - Siderophile and volatile trace elements

Fifteen siderophile and volatile trace elements (Os, Re, Ir, Pd, Ni, Au, Sb, Ge, Se, Ag, In, Zn, Cd, Bi, Tl) and U were determined by radiochemical neutron activation analysis in a spheroidal aphanitic clast and a clast of coarse-grained anorthositic gabbro from breccia 73215 and in three types of aphanite and two clasts of fine-grained anorthositic gabbro from breccia 73255. In common with most Apollo 17 fragment-laden melt rocks, the aphanites from 73215 and 73255 predominantly contain a Group 2 meteoritic component, which is apparently derived from the Serenitatis impact. All aphanitic lithologies contain the same meteoritic component, and are probably cogenetic. The clasts of fine-grained anorthositic gabbro contain substantial amounts (2% to 6% Cl equivalent based on Au) of a pre-Serenitatis Group 3 component. The clast of coarse-grained anorthositic gabbro is low in siderophile elements (0.4% Cl equivalent), and the meteoritic component (Group 5) is not well-defined. A strong correlation exists between Ir and Au in both the aphanites and the anorthositic gabbro clasts, which argues against the breccias 73215 and 73255 being open systems for Au

Morgan, J. W.↗
NASA NTRS1980

Densities and mass motions in transition-zone plasmas in solar flares observed from Skylab

The electron densities and bulk motions in the transition-zone plasma of a solar flare are investigated by an analysis of EUV emission line spectra taken on Skylab. Spectra of three flares were obtained with the NRL normal incidence grating slit spectrograph in the ranges 1100-1940 and 1940-3940 A. The line ratios of transition-zone Si III lines and the intensity of the forbidden O IV 1401-A lines during flare maximum indicate electron densities on the order of 10 to the 12th/cu cm, decreasing by a factor of 2 to 3 in the flare decay phase. Line broadening of the transition-zone ions such as Si III, O IV, C IV and N V is noted, and the observed asymmetrical N V line profiles are approximated by a bi-Gaussian model of a stationary and a moving plasma component with a bulk velocity of 12 to 70 km/sec. Turbulent velocities of from 45 to 85 km/sec and from 20 to 40 km/sec are also indicated for the moving and stationary components of the transition-zone plasma, respectively.

Cheng, C.-C.↗
NASA NTRS1980

Trace element contents of selected Antarctic meteorites. I - Weathering effects and ALH A77005, A77257, A77278 and A 77299

Data is examined for volatile/mobile Ag, As, Au, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Sb, Se, Te, Tl and Zn in exterior and/or interior samples of four Antarctic meteorites from the Allan Hills (ALH): A77005 (unique achondrite); A77257 (ureilite); A77278 (L3); A77299 (H3). Exterior samples reflect contamination and/or leaching by weathering but trace element (ppm-ppt) contents in interior samples seem reasonable for representatives of these rare meteoritic types. The A77005 achondrite is shown to be related to shergottites; other samples extend compositional ranges previously known for their groups or types. With suitable precautions, Antarctic meteorite finds yield trace element data as reliable as those obtained from previously known falls.

Biswas, S.↗
NASA NTRS1980

SO2 frost - UV-visible reflectivity and Io surface coverage

The reflectance spectrum in the range 0.24-0.85 microns of SO2 frost is measured in light of the discovery of SO2 gas in the atmosphere of Io and the possible discovery of the frost on its surface. Frost deposits up to 1.5 mm thick were grown in vacuum at 130 K and bi-directional reflectance spectra were obtained. Typical SO2 frost is found to exhibit very low reflectivity (2-5%) at 0.30 microns, rising steeply at 0.32 microns to attain a maximum reflectivity (75-80%) at 4.0 microns and uniformly high reflectivity throughout the visible and near infrared. Comparison with the full disk spectrum of Io reveals that no more than 20% of the surface can be covered with optically thick SO2 frost. Combinations of surface materials including SO2 frost which can produce the observed spectrum are indicated.

Nash, D. B.↗
NASA NTRS1979

Multispectral Resource Sampler (MRS): Proof of concept study on atmospheric corrections. Determinations of atmospheric optical parameters using the multispectral resource sampler atmospheric optical

An investigation was performed to determine which mathematical algorithms should be used in the calculation of atmospheric optical parameters using the Multispectral Resource Sampler (MRS) sensor. A simulation of the MRS sensor was performed using a radiative-transfer model. The simulation provides the spectral radiance at the satellite sensor in terms of various atmospheric parameters, such as optical thickness, solar zenith angle, nadir view angle, relative azimuth angle, bi-directional reflectance of the target, background albedo, and wavelength. Atmospheric correction algorithms were also developed for the determination of the total spectral optical thickness of the atmosphere for: (1) homogeneous (horizontal) hazy atmospheres with diffuse targets; (2) inhomogeneous (horizontal) hazy atmospheres with diffuse targets; and (3) homogeneous (horizontal) hazy atmospheres with non-diffuse targets.

Turner, R. E.↗