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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

An extreme ultraviolet telescope with no soft X-ray response

While EUV grazing incidence telescopes of conventional design exhibit a substantial X-ray response as well as an extreme UV response, and existing bandpass filters for the transmission of radiation longward of 400 A also transmit soft X-rays, the grazing incidence telescope presented suppresses this soft X-ray throughput through the incorporation of a Wolter Schwarzschild Type II mirror with large graze angles. The desirable features of an EUV photometric survey telescope are retained. An instrument of this design will be flown on the EUE mission, in order to make a survey of the sky at wavelengths longer than 400 A.

Finley, David S.↗
NASA NTRS1978

Extreme ultraviolet observations of coronal holes. II - Association of holes with solar magnetic fields and a model for their formation during the solar cycle

Skylab and ground-based observations in the extreme UV range of the spectrum are used to analyze characteristics of coronal holes, and to correlate their development with variations in the solar cycle. The mergence of bipolar magnetic regions (BMR) during the declining phase of the cycle is held reponsible for the formation of large equatorial holes (M-regions, which cause recurring geomagnetic storms). The BMR mergence model can also be applied to polar cap holes.

Bohlin, J. D.↗
NASA NTRS1974

Extreme ultraviolet spectrometer for space research

A normal incidence spectrometer for use in the wavelength region from 200 to 1270 A has been developed. The design and calibration of the instrument are described in detail. The spectrometer can be employed to detect extreme UV radiation at a minimum flux level of 1 rayleigh with a spectral resolution of 40 A and a spatial resolution of 6 deg. Data on the extreme UV night sky spectrum between 780 and 1270 A obtained with this instrument on a recent rocket flight are presented.

Kumar, S.↗
NASA NTRS1996

Optical Identification of Quasar 0917+7122 in the Direction of an Extreme-Ultraviolet Source

We report the optical identification of an R = 18.3 mag, z = 2.432 quasar at the position of a 6 cm radio source and a faint ROSAT PSPC X-ray source. The quasar lies within the error circles of unidentified extreme-UV (EUV) detections by the EUVE and ROSAT WFC all-sky surveys at approximately 400 A and approximately 150 A, respectively. A 21 cm H I emission measurement in the direction of the quasar with a 21'-diameter beam yields a total H I column density of N(sub H) = 3.3 x 10(exp 20) /sq cm, two orders of magnitude higher than the maximum allowed for transparency through the Galaxy in the EUV The source of the EUV flux is therefore probably nearby (approximately < 100 pc), and unrelated to the quasar.

Maoz, D.↗
NASA NTRS1988

A self-consistent interpretation of the solar flare extreme-ultraviolet to hard X-ray ratio in large events

This paper shows quantitatively that when a limiting X-ray yield is considered, a universal area of 10 to the 17th sq cm used in the thick-target electron bombardment model of McClymont and Canfield (1986) cannot explain the observed hard X-ray flux in large solar flare events without recourse to extreme values of the physical parameters of the flaring corona. The return current ohmic heating produced by a beam of flux 10 to the 13th ergs/sq cm/s results in a coronal temperature in excess of 100 million K. In this case, the thermal hard X-ray emission dominates the nonthermal emission and the EUV-to-hard X-ray ratio would not decrease with increasing hard X-ray flux, as observed. Hence, any model that requires a beam flux of 10 to the 13th ergs/sq cm/s is untenable. It is proposed that these apparently contradictory results can be reconciled if the X-ray emitting area is substantially larger than the area of the chromospheric precipitation site.

Larosa, T. N.↗
NASA NTRS1977

Extreme ultraviolet spectroheliograph ATM experiment S082A

The XUV spectroheliograph, Apollo Telescope Mount experiment S082A, is described. The instrument was a slitless Wadsworth grating spectrograph that employed photographic recording. The grating was of 4-m radius, ruled with 3600 grooves/mm. By rotating the grating to positions where the normal was at 255 A or 400 A, the spectral ranges 175-335 A and 320-480 A, respectively, were covered with 2-sec of arc spatial resolution. Close to the normal the resolution reached 2 sec of arc, but at the extreme limit, 630 A, it was 10 sec of arc or worse. The aberrations of the instrument are discussed in detail as are the provisions necessary to maintain optimum imagery and reliability in a space environment. During the mission about 1020 exposures were made covering 171-335 A or 320-630 A.

Tousey, R.↗
NASA NTRS1994

An Optics Free Spectrometer for the Extreme Ultraviolet

The optics-free spectrometer is a photon spectrometer. It provides the photon spectrum of a broadband source by converting photons of energy E into electrons of energy E', according to the Einstein relation, E' = E - Ei. E, is the ionization threshold of the gas target of interest (any of the rare gases are suitable) and E is the incoming photon energy. As is evident from the above equation, only a single order spectrum is produced throughout the energy range between the first and second ionization potentials of the rare gas used. Photons with energy above the second ionization potential produce two groups of electrons, but they are readily distinguished from each other. This feature makes this device extremely useful for determining the true spectrum of a continuum source or a many line source. The principle of operation and the laboratory results obtained with a representative configuration of the optics-free spectrometer are presented.

Judge, D. L.↗
NASA NTRS1978

Extreme-ultraviolet observations of dwarf novae from Apollo-Soyuz

The paper reports on EUV observations of four dwarf novae (SS Cyg, Z Cha, VW Hyi, and AE Aqr) in July 1975 during the Apollo-Soyuz Test Project, which were performed by using pointed grazing-incidence optics and a channel-electron multiplier as a photon detector. An EUV flux in the range from 55 to 150 A was detected from SS Cyg during an optical outburst at an intensity level considerably below that of Rappaport et al. (1974). Upper limits are placed on the EUV fluxes from Z Cha, VW Hyi, and AE Aqr. Multicolor optical photometry of SS Cyg and AE Aqr is also examined which was obtained simultaneously with the EUV observations. It is concluded that intrinsic EUV flux variability is probably a characteristic of SS Cyg and that the same system exhibits an extremely large range of soft X-ray luminosities while remaining at about the same visible light level. Several models for the SS Cyg system are compared with the EUV data.

Margon, B.↗