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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 415 records · Page 23
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NASA NTRS1975

Absolute calibration of a hydrogen discharge lamp in the vacuum ultraviolet

A low-pressure hydrogen discharge lamp was calibrated for radiant intensity in the vacuum ultraviolet spectral region on an absolute basis and was employed as a laboratory standard source in spectrograph calibrations. This calibration was accomplished through the use of a standard photodiode detector obtained from the National Bureau of Standards together with onsite measurements of spectral properties of optical components used. The stability of the light source for use in the calibration of vacuum ultraviolet spectrographs and optical systems was investigated and found to be amenable to laboratory applications. The lamp was studied for a range of operating parameters; the results indicate that with appropriate peripheral instrumentation, the light source can be used as a secondary laboratory standard source when operated under preset controlled conditions. Absolute intensity measurements were recorded for the wavelengths 127.7, 158.0, 177.5, and 195.0 nm for a time period of over 1 month, and the measurements were found to be repeatable to within 11 percent.

Nealy, J. E.↗
NASA NTRS1975

The LST scientific instruments

Seven scientific instruments are presently being studied for use with the Large Space Telescope (LST). These instruments are the F/24 Field Camera, the F/48-F/96 Planetary Camera, the High Resolution Spectrograph, the Faint Object Spectrograph, the Infrared Photometer, and the Astrometer. These instruments are being designed as facility instruments to be replaceable during the life of the Observatory.

Levin, G. M.↗
NASA NTRS1977

Slow scan SEC vidicon system

A slow scan SEC vidicon system is described here. This system is coupled to the 152.4-cm (60-in) McMath telescope at Kitt Peak National Observatory. An anamorphic lens system is used to couple optically the vertical spectrograph to the vidicon system. The resolutin of the over-all system is 55 mA, while the resolution of the spectrograph alone is 50 mA. Actual observational results are used to evaluate the system performance.

Chiu, H.-Y.↗
NASA NTRS1976

White light and radio studies of the coronal transient of 14-15 September 1973. I - Material motions and magnetic field

Observations of a coronal transient event were obtained in white light by the Skylab coronagraph and at metric wavelengths by the radioheliograph and spectrograph at Culgoora, Australia, and the spectrograph-interferometer at Boulder, Colo. The continuum radio burst was found to originate above the outward-moving white-light loop, a region of compressed material headed by a bow wave. The computed density in the region of radio emission, based on either gyrosynchrotron or harmonic plasma radiation mechanisms, was approximately 10 times the ambient coronal density; this is compatible with the density deduced from the white-light observations. The magnetic-energy density derived from the radio observations was greater than 10 times the thermal energy density, marginally larger than the kinetic energy density in the fastest-moving portion of the transient, and considerably larger in most other regions. The ambient medium, the white-light front, the compression region, the loop, and the slower massive flow of material behind are each examined. It is found that the plasma was magnetically controlled throughout and that magnetic forces provided the principal mechanism for acceleration of the transient material from the sun.

Dulk, G. A.↗
NASA NTRS1977

Spectrophotometry of the transient X-ray source A0620-00

Optical observations of the transient X-ray source A0620-00 over the wavelength range from about 3200 to 6600 A are analyzed which were made with the 5-m Hale telescope using a multichannel spectrometer, a digital spectrograph with a cooled integrating SIT vidicon, and an image photon-counting system attached to the camera of the coude spectrograph. Infrared observations at 1.65, 2.2, and 3.5 microns are also examined. Individual spectral lines of special interest are discussed, the E(B-V) color excess is estimated to be about 0.40, and a distance of 1200 pc is adopted. Analysis of the continuous spectrum yields several simple binary models. A specific model is proposed in which one of the continuum sources is an optically thick object characterized by a model atmosphere at a temperature of 25,000 to 30,000 K and the second source is either a cool black body at 4000 K or a partially optically thick source of bound-free plus free-free radiation from a hydrogen gas with an electron temperature of at least 100,000 K. Some possible parameters of these sources and of the accretion disk are considered.

Oke, J. B.↗
NASA NTRS1977

Measurements of H-beta, He D3, and Ca/+/ 8542-A line emission in quiescent prominences

Measurements of H-beta, He D3, and Ca(+) 8542-A line emission in 18 quiescent prominences are presented which were performed with a 25-cm coronagraph/coude spectrograph system and an optical multichannel analyzer utilizing a Si-vidicon detector assembly mounted at the single-pass spectrograph port. The data obtained show that the line profiles deviate in the wings from those calculated on the basis of an isothermal atmosphere and a Gaussian absorption coefficient. Both a non-Gaussian microturbulence component and a temperature gradient from prominence-core to coronal values can successfully account for this phenomenon. The line widths from a given line of sight of prominence material are reduced on the basis of a common core emitting region with a temperature of 7500 to 11,600 K and a microturbulent velocity of 4.5 to 7.1 km/s for the isothermal model (these values are 5% to 10% less for the two-temperature model). It is noted that long-period low-amplitude oscillations in the D3 line width and intensity were observed when a specific line of sight in a quiescent prominence was followed. These oscillations are found to remain coherent for as many as 3 or 4 cycles and to be associated with prominence structural activation.

Landman, D. A.↗
NASA NTRS1977

The spectrum and position of solar noise storms at decameter wavelengths

Decametric storm radiation during the period July-August 1970 has been observed simultaneously with a high sensitivity spectrograph at Arecibo Observatory and with the log-periodic, swept-frequency array of the Clark Lake Radio Observatory. The observations complement each other; different types of fine structure emissions can be easily identified on the spectrograph records and their position can be determined from the swept-frequency recordings. The relative positions of the different emissions which have been observed during the storms are studied. Four distinct sources appear to be present. The continuum emission, the type I bursts and the flare-related type III's are all emitted at different locations. The storm type III bursts, type IIIb's and drift pairs overlap in position, but appear at different locations than the previously mentioned sources.

De La Noe, J.↗
NASA NTRS1978

EUV spectra from Skylab /1175-1940 A/ - Mass motions in the transition zone in regions of solar activity

The profiles of spectral lines in the 1100-2000-A range emitted by transition-zone ions in regions of solar activity are discussed. The data were recorded by the NRL spectrograph on Skylab. At the spatial resolution of the Skylab spectrograph (2 x 60 arcsec), it is shown that the line profiles result from the superposed emission of a number of physically distinct regions at different electron densities and with different mass motions. Although high densities are found for some surgelike phenomena at transition-zone temperatures, the densities can also be comparable to normal active-region densities. Line profiles, as well as spectral line intensities, must be considered if meaningful theoretical models of dynamic activity in the transition zone are to be constructed.

Doschek, G. A.↗
NASA NTRS1979

Ultraviolet astronomy instrumentation for sounding rocket and Shuttle/Spacelab missions

The paper deals with an electrographic Schmidt camera for wide-field imaging and objective-spectrographic sky surveys, and with a nebula spectrograph designed to obtain slit spectra of nebulae and other diffuse sources. Each of these ultraviolet astronomy instruments has been successfully used in sounding rocket flights. It is seen that, with some minor modifications, both instruments should be readily adaptable to Spacelab missions.

Carruthers, G. R.↗
NASA NTRS1979

H2 emission in the solar atmosphere

New identifications of emission lines of molecular hydrogen in the EUV spectrum of sunspots are reported. The spectra were obtained during the first and second flights of the Naval Research Laboratory's High Resolution Telescope and Spectrograph (HRTS). While most of the lines originate in the Lyman bands, fluorescence from the Werner bands has been found for the first time in the solar atmosphere. H2 fluorescent emission has also been identified in the spectra of a solar flare observed with NRL's normal incidence spectrograph on Skylab. Column densities for H2 are derived from intensities of lines in the sunspot spectra.

Bartoe, J.-D. F.↗
NASA NTRS1979

CO emission lines in the solar atmosphere

New identifications of CO emission lines in the EUV spectrum of a sunspot are reported. The spectra were obtained with the Naval Research Laboratory's High Resolution Telescope and Spectrograph. The emission is from the CO fourth positive system and is excited by the strong lines of C IV, Si IV and O IV. Transitions in the 0-3 band which lie above 1700 A and other lines at shorter wavelengths have been identified from the spectrum of the June 15, 1973 flare, obtained with the Naval Research Laboratory's normal incidence spectrograph on Skylab. The observed intensities in the sunspot are used to derive the CO column density.

Jordan, C.↗
NASA NTRS1980

An interactive modular design for computerized photometry in spectrochemical analysis

A general functional description of totally automatic photometry of emission spectra is not available for an operating environment in which the sample compositions and analysis procedures are low-volume and non-routine. The advantages of using an interactive approach to computer control in such an operating environment are demonstrated. This approach includes modular subroutines selected at multiple-option, menu-style decision points. This style of programming is used to trace elemental determinations, including the automated reading of spectrographic plates produced by a 3.4 m Ebert mount spectrograph using a dc-arc in an argon atmosphere. The simplified control logic and modular subroutine approach facilitates innovative research and program development, yet is easily adapted to routine tasks. Operator confidence and control are increased by the built-in options including degree of automation, amount of intermediate data printed out, amount of user prompting, and multidirectional decision points.

Bair, V. L.↗
NASA NTRS1980

Spectrophotometric observations of P/Schwassmann-Wachmann 1 during outburst

Spectra of Comet Schwassmann-Wachmann 1 were obtained on November 26-27, 1978 and February 15, 1979 using the Cassegrain Digicon spectrograph, and on February 21-23, 1979 using the IDS spectrograph of McDonald Observatory. All spectra were obtained while the comet was in an extended series of outburst (12th-13th mag). The spectra were predominantly reflected solar light, indicating the outburst was very rich in dust. Weak emission between 4000 and 4050 A, and between 4240 and 4290 A was detected in November 1978 and is probably due to CO(+). These outbursts, and the detection of CO(+), indicate that comets are not inactive at distances as great as 6 AU.

Cochran, A. L.↗
NASA NTRS1980

An interactive modular design for computerized photometry in spectrochemical analysis

An interactive, top-down structured program design is described which produces a general flexible description of totally automatic photometry of emission spectra in an operating environment in which sample compositions and analysis procedures are low-volume and nonroutine. The use of this type of programming is illustrated by a project to computerize trace elemental determinations including the automated reading of spectrographic plates produced by a 3.4-m Ebert mount spectrograph using a dc-arc in an argon atmosphere.

Bair, V. L.↗
NASA NTRS1979

Space Telescope Digicon

The Digicon, chosen by NASA as the detector for the High Resolution Spectrograph (HRS) and the Faint Object Spectrograph (FOS) is a 512 parallel output channel vacuum photodetector. There are two HRS Digicons with spectral sensitivity ranges from 1050 A to 1800 A and 1150 A to 3000 A respectively, and two FOS Digicons, which have spectral ranges extending to 7000 A. The significant requirements for these devices are 0.01 counts per second background count rate per diode, state-of-the-art Digicon pulse height resolution (typical 15%) and a high degree of imaging precision and stability. The results of a manufacturing and test program to develop the Digicons coupled with extensive prior work has shown that these requirements can be met. The Digicon because of its inherent ruggedness is particularly well suited to space applications.

Alting-Mees, H. R.↗
NASA NTRS1980

Space Telescope - A versatile new instrument

The design, in-orbit operation and projected performance of the Space Telescope are discussed. The telescope will be in a moderately low earth orbit and communicate with the earth through the Tracking and Data Relay Satellite and directly for a few minutes each orbit. The optical system contains a 2.4-m mirror in a standard Cassegrain configuration, with four axial instrument positions and one radial and a fine guidance sensor which will allow the maintenance of telescope pointing during an observation to seven thousandths of an arcsec. The satellite will be launched by the Space Shuttle, and is capable of being serviced in space or recaptured and brought back to earth for more extensive modifications. The telescope employs a fairly standard Ritchey-Chretian optical design with a primary field of view of 18 arcmin and good mirror reflection of wavelengths from 1100 A to 1 mm. Image quality will be very insensitive to wavelength, with image size on the order of 0.04 arcsec. Instruments to be carried on the first launch include a guidance system for astrometry, a wide-field and planetary camera, a faint object camera, a high resolution spectrograph, a faint object spectrograph and a high-speed photometer.

Roman, N.↗
NASA NTRS1980

The Space Telescope Observatory

The Space Telescope is an international astronomical observatory which will be placed into a low earth orbit in December 1983. The observatory will provide astronomers the opportunity to use five different instruments (wide field/planetary camera, faint object camera, high-resolution spectrograph, faint-object spectrograph, and high speed photometer), and to do astrometry with the use of the fine guidance sensors used primarily for pointing control. These instruments, the spectral range available above the earth's atmosphere, and the spatial resolution available from the combination of a near-diffraction limited 94-in. primary mirror and the stability provided by the Pointing Control System provide a tremendous potential to the astronomical community.

Bahcall, J. N.↗
NASA NTRS1980

Ultraviolet /UV/ emission line mapping of selected regions in the Orion Nebula

Digital processing of data from the International Ultraviolet Explorer (IUE) satellite are used to obtain monochromatic mosaic images of the most prominent UV spectra lines at 35 locations in the central region of the Orion Nebula. The image processing techniques include calculations of the spectrograph orientation and the thermal effects, normalization for exposure time, background subtraction, correction for sensitivity variation within the IUE spectrograph aperture, correction to an absolute flux scale, sample interpolation, and display on graphic devices. The resulting UV emission line intensity maps may be used in conjunction with observations of other wavelength regions to determine the spatial distribution of ionization and abundance levels of carbon and oxygen in Orion.

Turnrose, B. E.↗