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DOE OSTI2020

Quantifying Leaf Chlorophyll Concentration of Sorghum from Hyperspectral Data Using Derivative Calculus and Machine Learning

Leaf chlorophyll concentration (LCC) is an important indicator of plant health, vigor, physiological status, productivity, and nutrient deficiencies. Hyperspectral spectroscopy at leaf level has been widely used to estimate LCC accurately and non-destructively. This study utilized leaf-level hyperspectral data with derivative calculus and machine learning to estimate LCC of sorghum. We calculated fractional derivative (FD) orders starting from 0.2 to 2.0 with 0.2 order increments. Additionally, 43 common vegetation indices (VIs) were calculated from leaf spectral reflectance factor to make comparisons with reflectance-based data. Within the modeling pipeline, three feature selection methods were assessed: Pearson’s correlation coefficient (PCC), partial least squares based variable importance in the projection (VIP), and random forest-based mean decrease impurity (MDI). Finally, we used partial least squares regression (PLSR), random forest regression (RFR), support vector regression (SVR), and extreme learning regression (ELR) to estimate the LCC of sorghum. Results showed that: (1) increasing derivative order can show improved model performance until certain order for reflectance-based analysis; however, it is inconclusive to state that a particular order is optimal for estimating LCC of sorghum; (2) VI-based modeling outperformed derivative augmented reflectance factor-based modeling; (3) mean decrease impurity was found effective in selecting sensitive features from large feature space (reflectance-based analysis), whereas simple Pearson’s correlation coefficient worked better with smaller feature space (VI-based analysis); and (4) SVR outperformed all other models within reflectance-based analysis; alternatively, ELR with VIs from original reflectance yielded slightly better results compared to all other models.

47 OTHER INSTRUMENTATION↗

DOE OSTI2023

The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra

Abstract A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) of the optical spectroscopic data to quantify key survey metrics. In this paper we present results from VI of the quasar survey using deep coadded SV spectra. We show that the majority (≈70%) of the main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. A nonnegligible fraction of the quasars are misidentified by the standard spectroscopic pipeline, but we show that the majority can be recovered using post-pipeline “afterburner” quasar-identification approaches. We combine these “afterburners” with our standard pipeline to create a modified pipeline to increase the overall quasar yield. At the depth of the main DESI survey, both pipelines achieve a good-redshift purity (reliable redshifts measured within 3000 km s −1 ) of ≈99%; however, the modified pipeline recovers ≈94% of the visually inspected quasars, as compared to ≈86% from the standard pipeline. We demonstrate that both pipelines achieve a median redshift precision and accuracy of ≈100 km s −1 and ≈70 km s −1 , respectively. We constructed composite spectra to investigate why some quasars are missed by the standard pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of “Seyfert galaxies”) and/or more dust reddened than the standard-pipeline quasars. We also show example spectra to demonstrate the overall diversity of the DESI quasar sample and provide strong-lensing candidates where two targets contribute to a single spectrum.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1960

Observations of the Van Allen Radiation Regions During August and September 1959

An integrating ionization chamber and a single Geiger counter were flown on United States satellite Explorer VI in an elliptical orbit extending to 48,000 km. In addition to the Van Allen inner zone and the great outer zone, a stable and distinct intermediate zone was detected throughout August and September 1959. The outer-zone intensity showed a large decrease following the sudden commencement of a geomagnetic storm. Later in the storm the outer zone increased to much in excess of its prestorm level. During stable periods the outer zone was fairly constant and less intense than it had been observed to be with Pioneer III or Pioneer IV or the first Soviet cosmic rocket. Cosmic-ray background counting rates were reached on most passes in August and Septmeber near apogee of the satellite. The radiation ?dumped? from the outer zone during the geomagnetic storm fits very well with the intensity and latitude distribution required to account for balloon observations of auroral X rays made during the IGY period. This paper is based on preliminary analysis of Explorer VI data.

Arnoldy, R. L.↗

NASA NTRS1972

Rocket spectroscopy of zeta Orionis.

Analysis of a spectrum of zeta Ori extending from 922 to 1453 A with approximately 0.8 A resolution recorded at rocket altitudes. All lines used in existing models of stellar atmospheres appear in the recorded spectrum with the exception of those masked by telluric N2 or strong P Cygni-type profiles and by an O V line at 1371.29 A. Fifteen multiplets of subordinate lines have been reliably identified, indicating an approximate range of excitation from 0 to 50 eV. Transitions in C III (1176 A), N III (991 A), N V (1239, 1243 A), O VI (1032, 1038 A), Si IV (1394, 1403 A), S IV (1063, 1074 A), and S VI (933, 944 A) have been observed as P Cygni-type profiles presumably arising in a circumstellar envelope. The degree of ionization, transitions present, and mean radial velocities are all consistent with viewing the envelope as a hot (about 100,000 K), rarefied plasma in which collisional ionization is important. Interstellar lines in C I (1277, 1280 A), C II (1036, 1334 A), N I (1134-1135 A), N I (1200-1201 A), N II (1084-1086 A), O I (1302, 1305 A), Si II (1190, 1193 A), Si II (1260 A), and Si II (1304 A) have been definitely identified. Other transitions in Ar II, S I, C I, and Fe II are tentatively identified. The equivalent width of the L alpha line is found to be 10.4 plus or minus 1.6 A, corresponding to a columnar density of 2.0 plus or minus 0.7 x 10 to the 20th per cu cm.

Smith, A. M.↗

NASA NTRS1974

A tracking polarimeter for measuring solar and ionospheric Faraday rotation of signals from deep space probes

A tracking polarimeter implemented on the 64-m NASA/JPL paraboloid antenna at Goldstone, Calif., is described. Its performance is analyzed and compared with measurements. The system was developed to measure Faraday rotation in the solar corona of the telemetry carrier from the Pioneer VI spacecraft as it was occulted by the sun. It also measures rotation in the earth's ionosphere and is an accurate method of determining spacecraft orientation. The new feature of this system is its use of a pair of quarter-wave plates to allow the synthesis of a rotating feed system, while requiring the rotation of only a single section of waveguide. Since the polarization sensing is done at RF and the receiver operates essentially as a null detector, the system's accuracy is superior to other polarization tracking schemes. In addition, the antenna size and maser preamplifier provide unsurpassed sensitivity. The associated instrumentation used in the Pioneer VI experiment is also described.

Ohlson, J. E.↗

NASA NTRS1975

G2.4 + 1.4, a supernova remnant or ring nebula around a peculiar star

G2.4 + 1.4 is a probable nonthermal radio source and an optical nebula which appears to be a supernova remnant (SNR). It also contains an O VI sequence star of great excitation. We present new radiofrequency-continuum and (nil) H 92 alpha observations, optical spectroscopy, and Fabry-Perot scanner observations of the nebula. The object distance (possibly 5 kpc), origin of gas kinematics (possibly SNR expansion), and mode of excitation of the gas (possibly photoexcitation and/or shock wave) remain uncertain. We discuss the possible roles of the O VI star as 'runaway' in an SNR, as a source of photoexcitation, and as an ejector of a 'counterfeit' SNR.

Johnson, H. M.↗

NASA NTRS1975

Experimental investigation of supersonic flow past double-wedge configurations

Viscous-inviscid interactions characteristic of those which occur when the fuselage-generated shock wave interacts with the wing-generated shock wave of a shuttle orbiter were studied experimentally. Surface-pressure measurements and schlieren photographs were obtained to define the flowfield generated when a Mach 4.97 stream encounters a double-wedge configuration. The deflection angles for the two wedge surfaces were such that the shock interaction pattern was either a Type-V pattern or a Type-VI pattern, as defined by Edney. The correlation between the present data and the theoretical solution for the Type-VI solution is satisfactory. The correlation between the measured Type-V shock-interaction pattern and the theoretical solution is satisfactory up to the interaction region. Downstream of the interaction the Type-V data depend primarily on the shape of the leading-edge shock wave.

Bertin, J. J.↗

NASA NTRS1976

An experimental investigation of supersonic flow past a wedge-cylinder configuration

An experimental investigation of supersonic flow past double-wedge configurations was conducted. Over the range of geometries tested, it was found that, while theoretical solutions both for a Type V pattern and for a Type VI pattern could be generated for a particular flow condition (as defined by the geometry and the free-stream conditions), the weaker, Type VI pattern was observed experimentally. More rigorous flow-field solutions were developed for the flow along the wing leading-edge. Solutions were developed for the three-dimensional flow in the plane of symmetry of a swept cylinder (which represented the wing leading-edge) which was mounted on a wedge (which generated the "bow" shock wave). A numerical code was developed using integral techniques to calculate the flow in the shock layer upstream of the interaction region (i.e., near the wing root). Heat transfer rates were calculated for various free stream conditions. The present investigation was undertaken to examine the effects of crossflow on the resultant flow-field and to verify the flow model used in theoretical calculations.

Barnette, D. W.↗

NASA NTRS1975

An upper limit on interstellar C IV in the spectrum of gamma-2 Velorum

An upper limit on the column density of C IV along the line of sight to gamma-2 Vel is derived from upper limits placed on the equivalent widths of the interstellar C IV doublet with rest wavelengths at 1548.20 A and 1550.77 A. A lower limit of 250,000 K is calculated for the electron temperature of O VI emitting regions by combining the C IV results with a measurement of the column density of interstellar O VI for the same star and using calculations for the relative ionization of some abundant elements as a function of electron temperature in a low-density plasma. Since gamma-2 Vel is in the central part of the Gum Nebula, the high temperature suggested by these results is shown to support the idea that a high-temperature phase of the interstellar medium, possibly maintained by supernova explosions, may exist.-

Lengyel-Frey, D.↗

NASA NTRS1976

P Cygni profiles in zeta Ophiuchi and zeta Puppis

Detailed P Cygni profiles are plotted using data from selected regions of the far-UV spectra of zeta OPh and zeta Pup obtained by the Copernicus satellite. Equivalent widths and velocity shifts of both emission and absorption features are also presented. For zeta Oph, it is found that only the C IV and N V resonance lines exhibit the P Cygni phenomenon; for zeta Pup, the resonance lines of C III, N III, Si IV, C IV, P V, S VI, N V, and O VI all show strong P Cygni lines, although the emission component seems to be absent in N III. For both stars, it is shown that parts of most absorption profiles exceed the escape velocity, indicating mass ejection. The short-wavelength edges of the resonance lines are found to average about -1590 km/s in zeta Oph and about -2660 km/s in zeta Pup, with no significant dependence on ionization potential. It is noted that the equivalent width of the emission component is always considerably less than that of the absorption component, suggesting that absorption occurs close to the stellar surface.

Morton, D. C.↗

NASA NTRS1977

Relative motions of fragments of the split comets. I - A new approach

A hypothesis is proposed which interprets the relative motion of two fragments of a split comet in terms of a slight difference between their effective solar attraction rather than in terms of the impulse imparted to them at separation. A quantitative version of this hypothesis is formulated by assuming that the difference in effective solar attraction varies with heliocentric distance in direct proportion to the actual solar attraction so that the ratio of the two forces is constant and equal to a measure of the relative effect between the two fragments under consideration. Results obtained using this formulation are compared with observational evidence on the split comets P/Biela, Liais 1860 I, 1882 II, P/Brooks 2 1889 V, Swift 1899 I, Kopff 1905 IV, Mellish 1915 II, Taylor 1916 I, 1947 XII, Wirtanen 1957 VI, Ikeya-Seki 1965 VIII, Kohoutek 1970 III, and West 1975n. The hypothesis is found to fail only in the case of comet Wirtanen 1957 VI. Some unusual phenomena associated with split comets are examined.

Sekanina, Z.↗

NASA NTRS1978

Nebular observations and stellar coronae

Copernicus UV observations of O VI in early-type stars are used to infer the existence of coronae or hot stellar winds. Attention is given to the optical doublet of O VI at wavelengths 3811 and 3834, which is seen in the spectra of some central stars in planetary nebulae, and taken to be evidence of a coronal wind. It is noted (from observations of NGC 6751) that hot gas in the coronal model produces radiation at energies above 54 eV, which can affect He II Zanstra temperatures. He(+) ionizing radiation in population I early-type stars is also taken as an indication of hot winds.

Hartmann, L.↗

NASA NTRS1978

Growth of single crystals by vapor transport

The primary objectives of the program were to establish basic vapor transport and crystal growth properties and to determine thermodynamic, kinetic and structural parameters relevant to chemical vapor transport systems for different classes of materials. An important aspect of these studies was the observation of the effects of gravity-caused convection on the mass transport rate and crystal morphology. These objectives were accomplished through extensive vapor transport, thermochemical and structural studies on selected Mn-chalcogenides, II-VI and IV-VI compounds.

Wiedemeier, H.↗

NASA NTRS1979

Interstellar absorption lines in the spectrum of Gamma Velorum

Copernicus scans of selected interstellar absorption lines in the UV spectrum of Gamma Vel are analyzed, together with ground-based data, to obtain column densities for various ion states of C, N, O, Na, Mg, Al, Si, P, S, Cl, Ar, Ca, Mn, Fe, and CO. N I and O I are fitted to a single empirical curve of growth with a velocity parameter (b) of 8 km/s; Mg II, Si II, P II, S II, Mn II, and Fe II are fitted to another curve with b between 3 and 9 km/s. Abundance determinations relative to H I show that: (1) C, N, P, S, and Ar are probably close to their solar values; (2) O may be depleted by about a factor of 2; (3) Mg, Al, Si, Cl, Mn, and Fe are depleted by a factor of 4 or more: (4) Al is depleted by at least a factor of 10 in the H II region; and (5) both N V and O VI are present, but not C IV. The N V/O VI ratio implies that the electron temperature in the H II region is about 275,000 K.

Morton, D. C.↗

NASA NTRS1982

Optical and infrared observations of bright comets in the range 0.5 micrometers to 20 micrometers

The paper reviews IR observations of comets Ikeya-Seki 1965 VIII, Bennett 1970 II, Kohoutek 1973 XII, Bradfield 1974 III, Kobayashi-Berger-Milon 1975 IX, West 1976 VI, Bradfield 1980t, and P/Encke. It is shown that four of the five dusty comets observed (1970 II, 1974 III, 1976 VI, and 1980t) exhibited a silicate signature at 10 and 18 microns, indicating the presence of small refractory grains less than 5 microns in radius, and that the antitail of the fifth (1973 XII) did not have the silicate feature, suggesting the presence of large particles more than 30 microns in radius. A detailed study of Comet 1975 IX is discussed which indicates thermal emission from large grains. The dependence of comet brightness on diaphragm diameter is found to suggest a dust model in which the number of grains satisfies the continuity equation.

Ney, E. P.↗

NASA NTRS1983

Description of the containerless melting of glass in low gravity

A brief description is given of a single-axis, acoustic levitator/furnace apparatus used to position, heat, melt, and quench multicomponent oxide, glass-forming compositions in low gravity. This apparatus is capable of processing eight approximately spherical samples (about 6 mm diameter) at temperatures up to 1550 C in a dry air atmosphere. Results are also presented for a containerless melting experiment conducted on SPAR VI where a ternary CaO-Ga2O3-SiO2 composition was levitated and quenched to a glass. Selected properties of the glass prepared on SPAR VI are compared with the properties of glass samples of identical composition prepared on earth.

Ray, C. S.↗

NASA NTRS1984

A model for the estimation of the surface fluxes of momentum, heat and moisture of the cloud topped marine atmospheric boundary layer from satellite measurable parameters

A model is developed for the estimation of the surface fluxes of momentum, heat, and moisture of the cloud topped marine atmospheric boundary layer by use of satellite remotely sensed parameters. The parameters chosen for the problem are the integrated liquid water content, q sub li, the integrated water vapor content, q sub vi, the cloud top temperature, and either a measure of the 10 meter neutral wind speed or the friction velocity at the surface. Under the assumption of a horizontally homogeneous, well-mixed boundary layer, the model calculates the equivalent potential temperature and total water profiles of the boundary layer along with the boundary layer height from inputs of q sub li, q sub vi, and cloud top temperature. These values, along with the 10m neutral wind speed or friction velocity and the sea surface temperature are then used to estimate the surface fluxes. The development of a scheme to parameterize the integrated water vapor outside of the boundary layer for the cases of cold air outbreak and California coastal stratus is presented.

Allison, D. E.↗

NASA NTRS1985

The block program approach to photovoltaic module development

A series of photovoltaic module development activities, designated Blocks I through V, used increasingly refined requirements together with extensive testing and failure analysis to assist industry in developing the most advanced modules possible. The block program approach is described and the design details are given for all modules developed, highlighting the blockwise improvements. The success of this approach is demonstrated by the fact that most design details of the Block V modules have been adopted internationally. Instrumental to this success have been the steady improvements in design and test specifications that have guided module development. The experience gained since development of the Block-V specification is being incorporated into a Block VI Design and Test Specification, which includes upgraded and revised application-specific requirements. Highlights of this Block VI specification are also described.

Smokler, M. I.↗