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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 199 records · Page 11
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NASA NTRS1994

Ultraviolet imaging and spectroscopy of planetary atmospheres

The main scientific results of the participation of the Institute of Astrophysics (Belgium) in the NASA's Pioneer Venus mission are reported on. The data were obtained with the Pioneer Orbiter's Ultraviolet Spectrometer (POUVS). The instrument provided a morphological study of the nitric oxide ultraviolet night glow. Information concerning the altitude of the airglow emitting layer was also collected and used to constrain models of turbulent transport on the night side of the planet. Models of the odd nitrogen thermospheric chemistry and transport were developed to analyze the observations and derive the properties of the global circulation of Venus' upper atmosphere. Images of the Jovian ultraviolet aurora were obtained. The morphology and the time variations of the HI Ly-alpha and H2 Lyman and Werner bands were acquired at different longitudes. The observed distribution was compared with the results of the spectrometric observations made with the Voyager and the International Ultraviolet Explorer missions. Images concerning the Io surface albedo and Saturn's disk and ring's reflectivity were also obtained.

Gerard, Jean-Claude↗
NASA NTRS1997

High-Resolution Studies of Extreme-Ultraviolet Emission from CO by Electron Impact

We report a high-resolution study (0.0036 nm full width at half maximum) of electron-impact-induced emission spectra of CO at 30-, 75-, and 100-eV electron-impact energies. The spectral features were acquired in optically thin conditions. At the specified resolution, attainable with our 3-m vacuum ultraviolet spectrometer, we observe rotationally resolved emission bands of CO in the extreme ultraviolet, from the vibronic states B (sup 1)sigma(sup +)(0), C (sup 1)sigma(sup+)(0), and E (sup 1)pi(0), to the ground state X (sup 1)sigma(sup +)(0). A simple model of these bands, based on the Honl-London factors and the rotational constants, is constructed and is shown to be in good agreement with the observed spectra. The predissociation yield for the E (sup 1)pi electronic state has been determined, showing that the E state has the largest predissociation cross section of CO for all singlet-state Rydberg series members. The excitation function of the [E (sup 1)pi(0) yields X (sup 1)sigma(sup +)(0)] transition, in the 0-800-eV impact energy range, is measured, permitting determination of the oscillator strength by using a modified Born approximation analytical fit.

Ciocca, Marco↗
NASA NTRS2002

Jupiter Systems Data Analysis Program Galileo Multi-Spectral Analysis of the Galilean Satellites

Progress was made on this project at the University of Colorado, particularly concerning analysis of data of the galilean moons Io and Europa. The goal of the Io portion of this study is to incorporate Near Infrared Mapping Spectrometer (NIMS) measured sulfur dioxide (SO2) frost amounts into models used with Ultraviolet spectrometer (UVS) spectra, in order to better constrain SO2 gas amounts determined by the UVS. The overall goal of this portion of the study is to better understand the thickness and distribution of Io's SO2 atmosphere. The goal of the analysis of the Europa data is to better understand the source of the UV absorption feature centered near 280 rim which has been noted in disk-integrated spectra primarily on the trailing hemisphere. The NIMS data indicate asymmetric water ice bands on Europa, particularly over the trailing hemisphere, and especially concentrated in the visibly dark regions associated with chaotic terrain and lines. The UPS data, the first-ever disk-resolved UV spectra of Europa, shown that the UV absorber is likely concentrated in regions where the NIMS data show asymmetric water ice bands. The material that produces both spectral features is likely the same, and we use data from both wavelength regions to better understand this material, and whether it is endogenically or exogenically produced. This work is still in progress at JPL.

Hendrix, Amanda↗
NASA NTRS1993

Solar maximum mission/ultraviolet spectrometer and polarimeter studies

This final report for NASA Contract No. NAS8-35921 describes various studies performed for the Ultraviolet Spectrometer and Polarimeter (UVSP) experiment, one of several instruments on the Solar Maximum Mission (SMM) satellite which was launched on 14 February 1980. The UVSP consisted primarily of a Gregorian telescope and an Ebert-Fastie spectrometer with a polarimeter that could be inserted into the light path. The spacecraft and most of the instruments, including the UVSP, operated successfully until 23 November 1980, when part of the SMM attitude control system (fine pointing control) failed. The UVSP was then unable to observe the Sun until 18 April 1984, when the SMM was visited by the space shuttle and the attitude control module was replaced by astronauts. The SMM mission ended when the spacecraft reentered the atmosphere of the Earth and was thereby destroyed on 2 December 1989. The topics covered in this report include the following: (1) ultraviolet stellar polarimetry (probably the first such attempted measurement); no polarization as detected and the upper limits, based on the sensitivity as determined by the observed count rate, are rather high; (2) an investigation into the possible position of the UVSP wavelength drive after it became stuck on 26 April 1985; (3) fast timing tests for sit-and-state observations involving one or two detectors; (4) development of computer subroutines to allow the calculation of the component of the SMM spacecraft orbital velocity along the line of sight to the Sun at any desired time during the 1984/1985 period when the UVSP wavelength drive was operating properly; (5) listing of published research papers; (6) description of the UVSP catalog of observations; and (7) description of UVSP calibration report and data users guide.

Henze, William, Jr.↗
NASA NTRS1986

Stellar observations with the Voyager EUV objective grating spectrograph

During the periods of interplanetary cruise the Voyager ultraviolet spectrometers are used to provide unique and otherwise unobtainable observations in the extreme ultraviolet (EUV, 500 to 1200) and the far ultraviolet (FUV, 912 to 1220 A). These observations include the spectra of hot stellar sources as well as emission from the interplanetary medium. Recent results of note include: (1)Extensive spectrophotometric coverage of a superoutburst of the dwarf nova VW Hydri, which showed a clear 1/2 day delay in the outburst at 1000 A relative to that observed in the optical and a curious dip in the FUV light curve near maximum light. The Voyager observations were part of a comprehensive and highly successful campaign involving EXOSAT, IUE and ground based observations of this dwarf nova; (2)A comprehensive study of Be star spectra and variability. These results show the critical importance of FUV observations in the study of the effects of stellar rotation in hot stars; (3)The detection of a strong O VI absorption feature in the spectrum of the PG 1159-like object H1504+65. This detection along with the optical identification of weak O IV lines was a key to the interpretation of this object; which is of extremely high (>150,000K) temperature and appears to be a unique example of a stellar atmosphere devoid of H and He; (4)An analysis of an extremely long duration spectrum of the EUV and FUV sky background, which establishes important new upper limits on both continuum and line emission. This result also provide the first detection of interplanetary Lyman gamma.

Holberg, J. B.↗
NASA NTRS1988

The precipitation of energetic heavy ions into the upper atmosphere of Jupiter

Evidence for auroral particle precipitation at Jupiter was provided by the ultraviolet spectrometers on board the Voyager 1 and 2 spacecraft and by the International Ultraviolet Explorer. Magnetospheric measurements made by instruments on board the Voyager spacecraft indicate that energetic sulfur and oxygen ions are precipitating into the upper atmosphere of Jupiter. A theoretical model describing the interaction of precipitating oxygen with the Jovian atmosphere was constructed. The auroral energy is deposited in the atmosphere by means of ionization, excitation, and dissociation and heating of the atmospheric gas. Energetic ion precipitation and electron precipitation are shown to have similar effects on the atmosphere and ionosphere of Jupiter.

Horanyi, M.↗
NASA NTRS1996

Analysis of IUE Observations of Supernovae

This program supported the analysis of IUE observations of supernovae. One aspect was a Target-of-Opportunity program to observe bright supernovae which was applied to SN 1993J in M81, and another was continuing analysis of the IUE data from SN 1987A. Because of its quick response time, the IUE satellite has continued to provide useful data on the ultraviolet spectra of supernovae. Even after the launch of the Hubble Space Telescope, which has much more powerful ultraviolet spectrometers, the IUE has enabled us to obtain early and frequent measurements of ultraviolet radiation: this information has been folded in with our HST data to create unique observations of supernova which can be interpreted to give powerful constraints on the physical properties of the exploding stars. Our chief result in the present grant period was the completion of a detailed reanalysis of the data on the circumstellar shell of SN 1987A. The presence of narrow high-temperature mission lines from nitrogen-rich gas close to SN 1987A has been the principal observational constraint on the evolution of the supernova's progenitor. Our new analysis shows that the onset of these lines, their rise to maximum, and their subsequent fading can be understood in the context of a model for the photoionization of circumstellar matter.

Kirshner, Robert P.↗
NASA NTRS1997

A new look at the quiet sun network in the upper atmosphere during a minimum of activity cycle

The preliminary results obtained with the solar extreme ultraviolet spectrometer, onboard the Solar and Heliospheric Observatory (SOHO), are reported on. The solar ultraviolet measurement of emitted radiation (SUMER) instrument established a long time series of the network evolution in following the solar rotation. The maps of the network evolution were obtained in lines spanning from 10(sup 4) K to 6 x 10(sup 6) K. Line profiles were also recorded with a sampling of 1 x 0.76 sq arcsec over the entire field. The progress analysis of this set of data is underlined and the velocity distribution in the cell network is considered.

Lemaire, P.↗
NASA NTRS1984

Voyager EUV and FUV Observations

The Voyager 1 and 2 ultraviolet spectrometers are sensitive over the wavelength range 500 to 1700 A. In the extreme ultraviolet (EUV), at wavelengths shortward of the Lyman limit (912 A), Voyager observations detected emission from three out of a sample of 11 nearly hot DA white dwarfs. These observations imply very low HI column densities in the directions of the three stars detected. In the far ultraviolet (FUV), at wavelengths between 912 and 1200 A, Voyager observations of O and B stars can be used to study interstellar reddening at the shortest wavelengths and to provide useful estimates of interstellar H2 column densities.

Holberg, J. B.↗
NASA NTRS1985

Prospects for determining the cosmological helium-3 to helium-4 ratio via absorption-line studies of the local interstellar medium

The prospects for determining the interstellar (He-3)/(He-4) ratio via absorption-line studies in the extreme ultraviolet are considered. A high-resolution extreme-ultraviolet spectrometer fed by a 1-meter-class telescope similar to that discussed in the Far Ultraviolet Spectroscopic Explorer Report (1983) is assumed, and it is found that detection of He-3 may be possible with less than three days of observing time. To measure the (He-3)/(He-4) ratio with sufficient precision to determine the number of light neutrino species will require over 50 days of integration time for each object studied.

Hurwitz, M.↗
NASA NTRS1979

Jovian upper atmospheric temperature measurement by the Voyager 1 UV spectrometer

A measurement of the neutral temperature in the exosphere of Jupiter is reported. The observations were carried out by the Voyager 1 Ultraviolet Spectrometer during the solar occultation phase beginning 4.5 hours after the Jupiter encounter. The range of the exospheric temperature is found to be 1450 (+300, -250) K. The uncertainty in the determination of the temperature appears to be largely a consequence of the lack of knowledge of the brightness distribution on the solar disk at the time of the observations. The high exospheric temperature appears to result from a combination of upward-propagating inertia gravity waves, magnetospheric soft electrons, and auroral electrons, including those from the Io-plasma torus.

Atreya, S. K.↗
NASA NTRS1990

Far and extreme ultraviolet astronomy with ORFEUS

ORFEUS (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer) is a 1 m normal incidence telescope for spectroscopic investigations of cosmic sources in the far and extreme ultraviolet spectral range. The instrument will be integrated into the freeflyer platform ASTRO-SPAS. ORFEUS-SPAS is scheduled with STS ENDEAVOUR in September 1992. We describe the telescope with its two spectrometer and their capabilities i.e., spectral range, resolution and overall sensitivity. The main classes of objects to be observed with the instrument are discussed and two examples of simulated spectra for the white dwarf HZ43 and an O9-star in LMC are shown.

Kraemer, G.↗
NASA NTRS1986

A comparison of photospheric electric current and ultraviolet and X-ray emission in a solar active region

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft X-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is found between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region.

Haisch, B. M.↗
NASA NTRS1990

Study of planetary atmospheres by absorptive occultations

The absorption spectrum of the upper atmosphere can be observed as a function of height as a spacecraft observes the setting or rising of the sun or a star behind the limb of a planet. Data reduction methodology for absorptive occultations are described. Emphasis is placed on occultations by atmospheres other than the earth's in which the observed effects are dominated by absorption. Observations of the other planets by ultraviolet spectrometers able to look at the sun as well as stars are presented. Most of the instruments utilized the extreme ultraviolet wavelength region between 500 and 1600 A, which includes strong absorptions by nearly all gases and is consequently very useful for an initial exploration of a little known atmosphere. A closely related development is the utilization of stellar occultations seen from the earth's surface or airborne platforms, to obtain geometrical information on planets, rings, and asteroids, including density profiles of atmospheres. Voyager instruments defined the upper atmospheres of all four Jovian planets and the satellites Titan and Triton. Tight upper limits on the atmosphere of Mercury were established by Mariner 10.

Smith, Gerald R.↗
NASA NTRS1999

High-Resolution Spectroscopy of Auroras on Jupiter and Saturn/Earth Dayglow

The purpose of the grant was to allow the researcher to: (1) reduce and analyze Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometers (ORFEUS) II observations of Jupiter (200s) and Saturn (1200s); (2) Reduce and analyze selected ORFEUS-II Earth Far Ultraviolet (FUV) airglow data; (3) Modify existing scripts for simulating Earth FUV airglow emissions to model a subset of the ORFEUS data.

Gladstone, G. Randall↗
NASA NTRS1991

Calibration of passive remote observing optical and microwave instrumentation; Proceedings of the Meeting, Orlando, FL, Apr. 3-5, 1991

Various papers on the calibration of passive remote observing optical and microwave instrumentation are presented. Individual topics addressed include: on-board calibration device for a wide field-of-view instrument, calibration for the medium-resolution imaging spectrometer, cryogenic radiometers and intensity-stabilized lasers for EOS radiometric calibrations, radiometric stability of the Shuttle-borne solar backscatter ultraviolet spectrometer, ratioing radiometer for use with a solar diffuser, requirements of a solar diffuser and measurements of some candidate materials, reflectance stability analysis of Spectralon diffuse calibration panels, stray light effects on calibrations using a solar diffuser, radiometric calibration of SPOT 23 HRVs, surface and aerosol models for use in radiative transfer codes. Also addressed are: calibrated intercepts for solar radiometers used in remote sensor calibration, radiometric calibration of an airborne multispectral scanner, in-flight calibration of a helicopter-mounted Daedalus multispectral scanner, technique for improving the calibration of large-area sphere sources, remote colorimetry and its applications, spatial sampling errors for a satellite-borne scanning radiometer, calibration of EOS multispectral imaging sensors and solar irradiance variability.

Guenther, Bruce W.↗
NASA NTRS1975

Mariner 9 observations of beta Cephei stars

Ultraviolet spectra of three beta Cep variables and a nonvariable star of similar spectral type were observed by the ultraviolet spectrometer on Mariner 9. A significant light variation at 1400 A may have been detected for beta Cep. The variable stars have mean ultraviolet spectra similar to that of the nonvariable star and do not show any significant short-period spectral variations.

Lesh, J. R.↗
NASA NTRS1991

Design of spherical varied line-space gratings for a high-resolution EUV spectrometer

A highly efficient EUV spectrograph is designed for high-resolution spectroscopic observation. The spectrograph is designed for point source astronomy in a 40-120 nm bandpass and is to be ORFEUS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer), scheduled for launch as the first payload of a German space platform Astro-SPAS (Astronomy Shuttle Pallet Satellite). The design uses spherical varied line-space (SVLS) grating to minimize astigmatism, coma, and spherical aberration. The effectiveness and practical feasibility of the design is proved by an SVLS grating for visible use. The image focusing properties of the SVLS grating for ORFEUS are compared to those with toroidal uniform line-space (TULS) design. The SVLS design is superior to the TULS, theoretically in resolution and image concentration, but also practically with not only fabrication ease. Four SVLS gratings with nominal groove densities of 6000, 4550, 3450, and 2616 gr./mm, and a 200 mm x 200 mm ruled area have been ruled using a numerically controlled ruling engine for use in ORFEUS.

Harada, Tatsuo↗