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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.

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At least 1,477 records · Page 82
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NASA NTRS1981

Measured branching ratios for O II2D and 2P transitions in the wavelength range 530 to 800 A

Branching ratios for four sets of extreme ultraviolet transitions terminating on the 2D0 and 2P0 metastable levels of ionized oxygen have been measured. The emissions were excited in both an open window hollow cathode and a capillary discharge lamp, and the branching ratios were derived from the observed intensity ratios of the multiplet pairs. The results are in good agreement with theoretical values and compare favorably, within experimental uncertainties, with line ratios obtained by EUV spectroscopy of the airglow.

Morrison, D.↗
NASA NTRS1981

Observations of rich clusters of galaxies at metre wavelengths

Observations have been made at 10 frequencies between 50 and 120 MHz of 17 rich, X-ray emitting clusters of galaxies with the 78 x 156 m dipole array al Llanherne. The observed flux densities were compared to the flux densities expected on the basis of the known discrete sources in the fields. In no case was a significant flux excess found that might have indicated the presence of a diffuse halo component of radio emission in the cluster. For those clusters in which spectral indices could be determined, the spectra all tend to be much steeper than is normal for extragalactic radio sources, although a strict correlation between the X-ray luminosity and the low-frequency radio luminosity or spectral index is not found. The occurrence of large halo sources such as that which is present in the Coma cluster seems to be quite unusual.

Cane, H. V.↗
NASA NTRS1982

Earth-based remote sensing of planetary surfaces and atmospheres at radio wavelengths

Two reasons for remote sensing from the Earth are given: (1) space exploration, particularly below the surfaces or underneath cloud layers, is limited to only a very few planets; and (2) a program of regular monitoring, currently impractical with a limited number of space probes, is required. Reflected solar and nonthermal radiation are discussed. Relativistic electrons, trapped in large magnetospheres on Saturn and Jupiter, are discussed. These electrons produce synchrotron radiation and also interact with the ionosphere to produce bursts of low frequency emission. Because most objects are black-bodies, continuum radiometry is emphasized. Spectroscopic techniques and the measurement of nonthermal emission are also discussed.

Dickel, J. R.↗
NASA NTRS1981

Investigations of medium wavelength magnetic anomalies in the Eastern Pacific using Magsat data

Processing continued on the data set covering the first three months of the mission. Orbits were selected over a specified range of longitude and latitude and those orbits falling within the geographical boundaries were stored on a disk and a listing made. To verify the quality of the data, plots were made showing altitude vs latitude, anomalous field vs latitude, and corrected anomalous field vs latitude. Results of the plotting showed that: (1) data from the first day of the mission are not usable because they are too noisy; (2) some orbits contain spikes, no doubt a processing error on the tape; (3) some orbits contain a 20 deg region in latitude, offset roughly 30 nT from the rest of the anomalous field profiles; and (4) the correlation between the adjacent orbits is poor. Even the new ring current coefficients provided with a later, corrected set of data tapes did not not yield the desired correlations.

Harrison, C. G. A.↗
NASA NTRS1982

Coordinated observations of Markarian 180 at ultraviolet, X-ray, optical and radio wavelengths

The results of multifrequency observations of MrK 180 = 1133+704, a BL Lac object embedded in a giant elliptical galaxy are presented. The importance of MrK 180 derives mostly from its association of a quasar-like object with a galaxy whose absorption line redshift (z = 0.046) unambiguously determines its distance. This implies that physical conditions within this local quasar can be discussed without the confusion introduced by distance uncertainties.

Mufson, S. L.↗
NASA NTRS1982

A wavelength scannable XeCl oscillator-ring amplifier laser system

A holographic grating at grazing angle of incidence was used to achieve tunable, narrow bandwidth (0.005 nm) operation of a XeCl oscillator for injection locking of a ring amplifier. The amplifier's narrow bandwidth output energy was constant and equal to the untuned, broadband output (approximately 15 mJ) in regions where injection locking was achieved. Scanning was provided by use of a stepping motor-driven differential micrometer on the tuning mirror. This system was used to produce a laser excitation spectrum of hydroxyl radicals (OH) in a flame.

Pacala, T. J.↗
NASA NTRS1981

The submillimeter wavelength spectrum of methanol

Observations and assignments of some of the absorption lines in methanol from 200 to 850 GHz are reported. A simple phenomenological model is described which allows interpretation of spectra and prediction of new lines with little computational effort.

Pickett, H. M.↗
NASA NTRS1982

Observations of ring structure in a sunspot associated source at 6 centimeter wavelength

The detection of a new kind of sunspot-associated source in which the emission comes predominantly from a ring structure with size between that of the umbra and the penumbra is reported. The absence of emission from the center of the spot is interpreted in terms of the orientation of the magnetic field and the presence of low temperature material above the umbra.

Alissandrakis, C. E.↗
NASA NTRS1982

Doppler wavelength shifts of ultraviolet spectral lines in solar active regions

Doppler shifts are measured for solar UV emission lines formed in the lower transition region of active regions. Doppler shifts in different regions at the same solar location, variations of Doppler shift with position of an active region on the disk, and variations of Doppler shift with time at the same solar location in the same active region were studied. Observations were made with the NRL slit spectrograph on Skylab. Excluding flare and flare-related phenomena, only redshifts are found whose magnitudes correspond to downflow velocities between about 4 and 17 km/s. Shifts are largest for lines formed between about 50,000 and 100,000 K, and are distinctly less for lines formed above 100,000 K. The shifts persist out to the limb, but not above it. There is no obvious change in redshift for lines measured at the same solar location over time intervals of about 20 minutes.

Feldman, U.↗
NASA NTRS1982

Orbiting lidar simulations. I - Aerosol and cloud measurements by an independent-wavelength technique

Aerosol and cloud measurements have been simulated for a Space Shuttle lidar. Expected errors - in signal, transmission, density, and calibration - are calculated algebraically and checked by simulating measurements and retrievals using random-number generators. By day, vertical structure is retrieved for tenuous clouds, Saharan aerosols, and boundary layer aerosols (at 0.53 and 1.06 micron) as well as strong volcanic stratospheric aerosols (at 0.53 micron). By night, all these constituents are retrieved plus upper tropospheric and stratospheric aerosols (at 1.06 micron), mesospheric aerosols (at 0.53 micron), and noctilucent clouds (at 1.06 and 0.53 micron). The vertical resolution was 0.1-0.5 km in the troposphere, 0.5-2.0 km above, except 0.25-1.0 km in the mesospheric cloud and aerosol layers; horizontal resolution was 100-2000 km.

Russell, P. B.↗
NASA NTRS1982

VLA observations of the evolution of a solar burst source structure at 6 centimeter wavelength

Evolutionary changes in the total intensity and polarization structure of a 6 cm radio burst source have been observed with the VLA, over time scales ranging from 10 s to several minutes. This burst was associated with a 2B/M1 flare observed on 1980 May 14. The 6 cm burst consisted of a gradual phase of 30 minutes duration and a strong impulsive phase of duration less than two minutes. Synthesized maps of total intensity and polarization were obtained with spatial resolution of 2 x 3 arcsec and with temporal resolutions of five minutes during the gradual phase and 10 s during the impulsive phase. The sequence of polarization maps suggests a complex magnetic field structure undergoing rapid changes. Most importantly, they show the development of two bipolar regions or quadrupole structure just prior to the impulsive energy release.

Velusamy, T.↗
NASA NTRS1982

Positional characteristics of meter-decameter wavelength bursts associated with hard X-ray bursts

Isolated and grouped type III bursts have been observed in temporal association with impulsive hard X-ray bursts in the 26-154 keV range, down to frequencies as low as 30 MHz and out to a distance of 3.1 solar radii from the disk center. The bursts occurred in regions whose electron density may have been as much as 20 times higher than that of the Newkirk-Saito model. The present observations indicate that electron acceleration/injection occurs over a region covering a wide range of magnetic field lines. It is noted that, of the two gradual hard X-ray bursts observed in association with type IV bursts, one was accompanied by a type II event, while the other was not, although both exhibited the same characteristics. It is suggested that the gradual burst associated with a type IV only involved electrons which are trapped in the plasmoid which produces the meter-decameter emission, while another fraction of the population is trapped in the low-lying loops which produce the hard X-ray and centimeter radiation.

Kundu, M. R.↗
NASA NTRS1982

Characterization of tropospheric desert aerosols at solar wavelengths by multispectral radiometry from Landsat

Characteristics of tropospheric desert aerosols are derived by comparing nadir spectral reflectivities computed from the radiative transfer models with reflectivities measured from Landsat. Over the ocean, reflectivities are compared, but over land the comparison is carried out by determining the ratios of the nadir reflectivity of the surface-atmosphere system over heavy aerosol concentration to the reflectivity of the underlying surface. This remote sensing technique is found to be a sensitive approach for measuring n sub 2, the imaginary part of the refractive index. The desert aerosols under study, in the Iran and Pakistan area, are essentially pure scatterers, inasmuch as an n sub 2 value of 0.001 + or - 0.001 was determined for each of the four Landsat spectral bands, that is, for a spectral interval from 0.5 to 1.1 microns.

Otterman, J.↗
NASA NTRS1984

Multiple-Wavelength Metal/Halide Laser

Single device produces multiple lasing lines. Laser capable of producing many lasing lines has several reservoirs of halide lasant mixed with chlorides of copper, manganese and iron. Convection-control technique possible to rapidly change from one metal halide to another at maximum energy.

Nerheim, N. M.↗