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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

UV and radiofrequency observations of Wolf-Rayet stars

Observations of W stars in the ultraviolet by OAO 2 and at 750 and 1400 MHz with the Green Bank telescopes are discussed. The emphasis is on the Green Bank observations of W stars with symmetric nebulae around them, their interpretation, and comparisons with other data. The implications regarding mass distribution, internal motion, flux density, ejected mass, velocity dispersion, and expanding envelopes are considered in detail.

Johnson, H. M.↗
NASA NTRS1971

The UV spectrum of the Crab Nebula

Observations of the Crab nebula are described, which were made under the OAO 2/NASA guest-investigator program with WEP stellar photometers. The 10 foot-diameter focal plane diaphragm was ample enough to accept the 4 ft X 6 ft image. The logarithm of the integrated relative intensity per wavelength interval, corrected for sky background, and the rms error, from 11 passbands in the range 4250 to 1380 A, are given. No correction was given for polarization of light. The data were converted to logarithm of the flux density per frequency interval and plotted on scales of log nu (Hz) and of reciprocal microns with two adjustments.

Johnson, H. M.↗
NASA NTRS1971

Uranium plasma emission coefficient in the visible and near UV.

Measurements of the specific emission coefficient in the near ultra-violet and visible region of a uranium arc plasma are reported. Spatial unfolding of the intensity profile is used to determine the emission coefficient in the spectral range of 2000 A to 6000 A. The uranium partial pressure is estimated to range between .001 and .01 atmosphere, and the corresponding temperature range is 5000 - 10,000 K.

Mack, J. M., Jr.↗
NASA NTRS1971

Integral image tube-optical systems for the far UV.

Description of proposed image tube optical systems for narrow-band direct photography and broad bandpass photography from spacecraft outside the atmosphere. For narrow-band photography an f/1.5 Schmidt camera with a photocathode located on the focal surface is recommended. The photoelectrons are accelerated and magnetically focused onto a phosphor/fiber optics surface, the curvature of which partially corrects for distortions of the electric field introduced by the curved photocathode. The second stage can be any other tube, electrostatically or magnetically focused, having a fiber optics faceplate butted to the first stage. For broad bandpass a spectrograph with an f/3 all-reflecting Schmidt image tube camera is recommended.

Chincarini, G.↗
NASA NTRS1972

Rocket observations of solar UV radiation during the eclipse of 7 March 1970.

Results of observations of the solar eclipse of Mar. 7, 1970, with photometers sensitive to narrow bands of radiation at Lyman-alpha (1216 A) and at 2600 A included in the payloads of four Nike Apache rockets flown before and during the eclipse. At the center of totality, the flux of Lyman-alpha from the solar corona is 0.15% of the flux from the unobscured sun. The flux at second contact is 0.64%; at third contact, two observations give 0.52 and 0.59%. The brightness of the chromosphere in Lyman-alpha decreases exponentially over the range from 5 to 30 arc-sec from the limb with a scale height of 3835 plus or minus 70 km. In addition to the coronal and chromospheric Lyman-alpha a diffuse source is found. This is restricted to within 20 deg of the earth's horizon and is nearly uniform in azimuth at 170 km, the flux is about 3% of that from the unobscured sun. The flux of Lyman-alpha during the eclipse is considered in relation to the observed variation in electron density. It is concluded that, in totality, the ionosphere near 80 km is not in equilibrium with the ionizing radiation and that the production rate for electrons is not negligible if the loss process is recombination; it is negligible if the loss process is attachment-like.

Smith, L. G.↗
NASA NTRS1972

Measurements of the UV and VUV transmission of optical materials during high energy electron irradiation

An experimental program was conducted in which the optical transmission of several transparent materials was measured during high energy electron irradiation. These experiments were conducted using the Dynamitron electron accelerator as a continuous source of 1.5 MeV electrons and the LINAC electron accelerator as a pulsed source of 5-7 MeV electrons. The experimental program consisted of three major portions. The first portion, the optical transmission of fused silica, BeO, MgF2, and LiF was measured at vacuum ultraviolet wavelengths in the range 1550-2000 A during ambient temperature, 1.5 MeV electron irradiation at ionizing dose rates to 0.5 Mrad/sec. In the second portion of the program, the optical transmission of fused silica and BeO was measured in the range 2000-3000 A during high dose rate, elevated temperature 1.5 MeV electron irradiation. In particular, accurate measurements of the optical transmission were made at ionizing dose rates as high as 10 Mrad/sec. In the final portion of the program, the optical transmission of fused silica and BeO was measured in the wavelength range 2000-3000 A during pulsed 5 and 7 MeV electron irradiation from the LINAC accelerator. The maximum time averaged ionizing dose rate was limited to 0.75 Mrad/sec due to accelerator limitations.

Palma, G. E.↗
NASA NTRS1973

Optical and UV astronomy, overview

The study of stars and other astronomical objects by means of radiation emitted in the range of 1,000 to 10,000 A is considered. Spectrum classification, astrophysical observations, distribution in space and physical properties of celestial objects are used to develop a view of the formation and evolution of the universe.

Underhill, A. B.↗
NASA NTRS1972

Special report - UV: Eye on the moon.

The Lunar Surface Ultraviolet Spectrographic Camera, the primary objective of which was to determine the location and extent of gaseous material (principally hydrogen) in preselected regions of the celestial sphere is described. Camera capability included acquisition of direct imagery and spectroscopy of the same target. The optical section made use of a Schmidt reflector component. The procedure for making photographic records is outlined.

Lankes, L. R.↗
NASA NTRS1973

An extreme UV photometer for solar observations from Atmosphere Explorer.

A broadband photometer experiment is being prepared for the Atmosphere Explorer-C, -D, and -E missions to record the solar irradiance in seven wavelength bands in the range from 40 to 1250 A. The experiment contains four spiral electron multipliers located behind a moving eight-position filter wheel. Six of the eight sections of this wheel contain metallic filters used to spectrally isolate the solar irradiance. In addition, three Al2O3 diodes, two with filters, are being used to record the solar irradiance over the full range of orbital altitudes including those at which operation of multipliers with high voltages on open structures would be unsafe. A principal goal of the experiment will be to measure time dependence of the solar irradiance.

Heath, D. F.↗
NASA NTRS1973

Uranium plasma radiates in the UV spectrum

Description of an experiment designed to produce and spectroscopically analyze a simulated gas core reactor plasma in the spectral range from 300 to 1300 A. The plasma was produced by focusing the radiation of a Q-spoiled ruby laser onto the flat surface of a pure U-238 specimen.

Williams, M. D.↗
NASA NTRS1975

The investigation of O and N2 densities from the OSO-7 extreme UV data

The results of solar radiation observations in the extreme ultra-violet spectrum from 200 A to 600 A made by the OSO-7 Satellite were studied. The results of the influence of attenuation by the atmosphere in the 250 to 500 km altitude range are presented. Using published molecular absorption cross-sections at 304 A and 256 A, the Jaccia atmospheric model is validated, and shows that a mean exospheric of 1050 K is appropriate for the sunset data.

Source record↗
NASA NTRS1975

A thermal vacuum-UV solar simulator test system for assessing microbiological viability

Microorganisms were exposed to a simulated space environment in order to assess the photobiological effect of broad spectrum, nonionizing solar electromagnetic radiation in terms of viability. A thermal vacuum chamber capable of maintaining a vacuum of 0.000133n/sq m and an ultraviolet rich solar simulator were the main ingredients of the test system. Results to date indicate the system to be capable of providing reliable microbiological data.

Ross, D. S.↗
NASA NTRS1976

On the cometary hydrogen coma and far UV emission

Cometary hydrogen observations are reviewed with emphasis on observations of comet Bennett. The results are theoretically interpreted and a brief summary of ultraviolet observations other than Lyman alpha is given.

Keller, H. U.↗
NASA NTRS1976

Intensity and pressure dependence of resonance fluorescence of OH induced by a tunable UV laser

The intensity and pressure dependence of the fluorescence spectrum of OH in the presence of N2 and H2O molecules was studied. Saturation of the absorption transition was observed at low pressures, and the corresponding fluorescence signal was found to vary as the square root of the exciting intensity. This observed dependence agreed with the predicted dependence which took into account the presence of laser modes in the spectrum of the exciting radiation. With full laser power incident, a saturation parameter as high as 3 x 10 to the 5th was observed. The fluorescence spectrum was found to peak at 3145 and at 3090 A, with the relative peak intensities dependent upon gas pressures and upon the particular rotational electronic transition used for excitation. It is concluded that vibrational relaxation of the electronically excited OH due to water vapor in the system plays a dominant role in determining the observed fluorescence spectrum.

Killinger, D. K.↗
NASA NTRS1976

A search for slowly varying radio continuum emission from UV Ceti stars

The paper presents results of a search conducted at the Arecibo Observatory for variable 430-MHz emission from the active flare stars EQ Peg, YZ CMi, and AD Leo. No statistically significant evidence for slowly varying emission is found to a level of 0.05 Jy for AD Leo, 0.018-0.021 Jy for YZ CMi, and 0.009-0.018 Jy for EQ Peg. Upper limits of about 10 trillion K are determined for the brightness temperature of active radio regions on these stars at the time of the observations.

Spangler, S. R.↗
NASA NTRS1977

Speculations on the consequences to biology of space shuttle-associated increases in global UV-B radiation

Various aspects of the impact of ozone depletion on the biosphere are assessed and discussed. Speculations on the factors which determine the extent and nature of biological damage due to an increased flux of ultra violet light are presented. It is concluded that a complete assessment must consider both direct effects (organisms) as well as indirect effects (ecosystems). The role of computer simulation of ecosystem models as a predictive tool is examined.

Averner, M. M.↗