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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 217 records · Page 12

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NASA NTRS1974

LST and supporting technology

In order to realize the LST objectives of high angular resolution, extended wavelength coverage and faint object detection, the performance of the instruments must be matched to that of the telescope. To insure that adequate technology is available by 1976, an intensive SR & T program has been initiated which builds on previous work and is coordinated with work in other agencies. The primary areas of concern are detectors, on-board computers, and ultraviolet optical components. In the last area grating work is being emphasized. The on-board computer will be necessary to allow pre-processing of raw data and enable detector operation in a pulse counting mode. For detectors, the SEC Vidicon development will be continued but the use of solid-state arrays in the electron bombarded mode and channel plate detectors are being seriously considered. One challenging problem is to provide 2 K cooling to permit ultra-sensitive IR observations to be made.

Sobieski, S.↗

NASA NTRS1976

A far-infrared map of the Ophiuchus dark cloud region

An extensive area of the Ophiuchus dark cloud has been mapped at far-infrared (40-50 microns) wavelengths with high angular resolution (1 arcmin) using a 102-cm balloon-borne telescope. Three sources were detected and resolved. Two of the sources were identified with strong 2-micron sources that were also associated with radio continuum emission. The far-infrared flux is consistent with radiation from dust heated by an early B star. Previous 2-micron observations have indicated the presence of a large number of early B stars embedded in the dark cloud; the far-infrared observations indicate, however, that although some early B stars are in the dark cloud, most of the 2-micron sources are either behind the cloud or are stars not on the main sequence.

Fazio, G. G.↗

NASA NTRS1976

Microwave holographic imaging of aircraft with spaceborne illuminating source

The conceptual development of a method for the high angular resolution and accurate angular position estimates for the surveillance and traffic control of aircraft is considered. A target volume several hundred kilometers in diameter is illuminated by a CW microwave source located on a satellite in geosynchronous orbit. Signals are received by a large array of random, conformally located receiving elements. Each element receives the direct signal from the satellite plus signals reflected from aircraft in the illuminated volume. Coherent combination of the signals received from the individual elements permits the equivalent of holographic imaging or multiple beam formation from which the useful target data can be obtained.

Berkowitz, R. S.↗

NASA NTRS1977

Radiative transfer in dust and the spectral flux distribution of NGC 1068

The continuum spectral flux distribution of the Seyfert galaxy NGC 1068 is analyzed by detailed models of radiative transfer in an optically thick cloud of dust grains. For wavelengths short of 30 microns, models invoking a spherical dust cloud with visual optical depth near 10 in the nucleus of the galaxy can reproduce the observed spectrum in a way consistent with information derived from spectral lines. The far-infrared emission cannot be explained easily by dust in the nucleus, but it is hypothesized that this radiation is emitted by dust associated with the observed molecular clouds, and that these clouds lie outside the nucleus. This far-infrared emission, therefore, should be extended to the same degree as the molecular-cloud distribution. High angular resolution mapping will be necessary to confirm this hypothesis.

Jones, T. W.↗

NASA NTRS1977

Structure of the X-ray source in the Virgo cluster of galaxies

High-angular-resolution observations in the 0.15-1.5-keV band with an imaging X-ray telescope shows the extended X-ray source in the Virgo cluster of galaxies to be a diffuse halo of about 15 arcmin core radius surrounding M87. The angular structure of the surface brightness is marginally consistent with either of two simple models: (1) an isothermal (or adiabatic or hydrostatic) sphere plus a point source at M87 accounting for 12% of the total 0.5-1.5-keV intensity or (2) a power-law function without a discrete point source. No evidence for a point source is seen in the 0.15-0.28-keV band, which is consistent with self-absorption by about 10 to the 21st power per sq cm of matter having a cosmic abundance. The power-law models are motivated by the idea that radiation losses regulate the accretion of matter onto M87 and can account for the observed difference in the size of the X-ray source as seen in the present measurements and at higher energies.

Gorenstein, P.↗

NASA NTRS1979

Wide field/planetary camera optics study

Design feasibility of the baseline optical design concept was established for the wide field/planetary camera (WF/PC) and will be used with the space telescope (ST) to obtain high angular resolution astronomical information over a wide field. The design concept employs internal optics to relay the ST image to a CCD detector system. Optical design performance predictions, sensitivity and tolerance analyses, manufacturability of the optical components, and acceptance testing of the two mirror Cassegrain relays are discussed.

Source record↗

NASA NTRS1979

A far-infrared photometer for the Kuiper Airborne Observatory

A high-angular-resolution multiaperture far-IR photometric instrument for multicolor observations of a variety of objects at effective wavelengths of 40 to 160 microns is described which is ideal for use on NASA's Kuiper Airborne Observatory. The operational principles of the instrument are discussed, along with the far-IR radiometer and the offset guiding module. System performance is evaluated on the basis of the noise-equivalent flux of the radiometer, guiding accuracy capability, the suitability to the scientific objectives of the filter bandpasses and focal-plane aperture sizes, the ease of operation, and operating efficiency. Some examples of recent observations with this instrument are provided.

Harvey, P. M.↗

NASA NTRS1979

Physical characteristics of ionized gaseous nebulae

The high angular resolution and the capability of the space telescope to observe ultraviolet radiation are discussed in relation to investigating planetary nebulae. The physical characteristics of planetary nebulae particulary the abundances of the common light elements, the H2 regions, the angular size, and the surface brightness are reviewed. Differences between supernova remants and planetary nebulae and H2 regions are discussed.

Osterbrock, D. E.↗

NASA NTRS1980

Soft X-ray sources in the bar of the Large Magellanic Cloud

X-ray observations of the Large Magellanic Cloud were made with two collimated proportional counters having high angular resolution, a wide spectral dynamic range and a large aperture. Counting rates in the two detectors during the entire rocket flight are presented, and a number of soft X-ray (0.5-2 keV) sources were found in the bar of the LMC, having luminosities between 10 to the 37th and 10 to the 38th ergs/s. Emission in the 0.15-0.28 keV band from LMC X-3 was also detected.

Mckee, J. D.↗

NASA NTRS1981

Development of a CCD array as an imaging detector for advanced X-ray astrophysics facilities

The development of a charge coupled device (CCD) X-ray imager for a large aperture, high angular resolution X-ray telescope is discussed. Existing CCDs were surveyed and three candidate concepts were identified. An electronic camera control and computer interface, including software to drive a Fairchild 211 CCD, is described. In addition a vacuum mounting and cooling system is discussed. Performance data for the various components are given.

Schwartz, D. A.↗

NASA NTRS1982

Concepts for large interferometers in space

Very high angular resolution can be achieved in optical and radio astronomy through interferometers in space. Evolutionary approaches and required technological advances are presented. In the optical region a phase-coherent array, (COSMIC) starting as a four-element linear array is discussed. Combining several modules results in greatly improved resolution with a goal of combining images to obtain a single field of view with 0.004 arcsecond resolution. The angular resolution, detail and temporal coverage of radio maps obtained by ground-based Very Long Interferometry (VLBI) can be greatly improved by placing one of the stations in earth orbit. An evolutionary program leading to a large aperture VLBI observatory in space is discussed.

Morgan, S. H.↗

NASA NTRS1983

Feasibility study of an optically coherent telescope array in space

Numerical methods of image construction which can be used to produce very high angular resolution images at optical wavelengths of astronomical objects from an orbiting array of telescopes are discussed and a concept is presented for a phase-coherent optical telescope array which may be deployed by space shuttle in the 1990's. The system would start as a four-element linear array with a 12 m baseline. The initial module is a minimum redundant array with a photon-counting collecting area three times larger than space telescope and a one dimensional resolution of better than 0.01 arc seconds in the visible range. Later additions to the array would build up facility capability. The advantages of a VLBI observatory in space are considered as well as apertures for the telescopes.

Traub, W. A.↗

NASA NTRS1982

Speckle spectroscopy; an application for the multi-anode microchannel array detector system

Plans to combine the High Angular Resolution Imager/Spectrometer on the 4-meter Mayall telescope at the Kitt Peak National Observatory and the (256 x 1024)-pixel Multi-Anode Microchannel Array detector system to produce a unique instrument for speckle spectroscopy are described. The pulse-counting detector system will provide distortion-free imaging and will time tag each spatially-resolved photon event with an accuracy of 100 ns. The Imager/Spectrometer will provide a spatial resolution of 0.07 arcsec orthogonal to the plane of dispersion and 0.18 arcsec in the plane of dispersion.

Butcher, H. R.↗

NASA NTRS1982

Infrared observations of low-mass star formation in Orion - HH objects

The results of a preliminary analysis of IR data on Herbig-Haro objects in the Orion nebula are reported. The observations were made with the high angular resolution IR photometry equipment on the NASA Kuiper Airborne Observatory and the NASA facility on Mauna Kea, HI. Data were taken in the 1-200 microns region with 40, 6, and 8 arcsec resolution. Attention was focused on NGC 1999 (HH1-3) and M78 (HH24-25) and the determination of absolute luminosities of the exciting stars. Measurements were also made of the IR energy distribution in the thermally emitting dust clouds and the point sources. Herbig-Haro objects featured compact and far IR sizes and large visual extinction, in addition to a steeply rising energy distribution up to 50-100 microns, where the luminosity emitted was concentrated.

Harvey, P. M.↗

NASA NTRS1984

IRAS images of the galactic center

Some preliminary IRAS results in the form of images at 12, 25, 60, and 100 microns of an 8 deg x 15 deg area around the galactic center are presented. These absolute intensity maps have unprecedented sensitivity combined with high angular resolution, wide field coverage, and large wavelength range. They give a broad view of the central galaxy revealing previously unseen details, especially in regions far from the central few arcmin. Well-defined infrared features in the nucleus correspond to the nuclear radio sources Sgr A, B2, C, and D. Extremely faint structures are detected, such as the cold molecular cloud associated with Sgr B2 which has never before been detected at wavelenths shorter than 40 microns.

Gautier, T. N.↗

NASA NTRS1984

NGC 6334-V - An infrared bipolar nebula

High angular resolution infrared mapping of the enigmatic far-infrared source NGC 6334-V shows it to have a bipolar structure at 1-4 microns. This structure together with the near-infrared colors and previous observations of H2 emission suggests a model for the source (IRS 4) in which a single luminous star is embedded in a dust cloud with a disklike geometry. Photometry of near-infrared sources within 0.5 pc of IRS 4 is also presented. These data suggest that there are at least four lower luminosity members of a young, dense cluster associated with the dominant source.

Harvey, P. M.↗

NASA NTRS1984

Far Infrared Continuum Emission from the Galactic Center

High angular resolution observations of the Galactic center from the Kuiper Airborne Observatory are discussed. The results of multi-wavelength mapping reveal that the 30 micron distribution shows a single peak which lies between two emission lobes seen at the longer wavelengths. The 30 micron emission is known from ground-based measurements to peak at the galactic center. The far-infrared color temperature and luminosity also peak at the position of the galactic center, and the observations show a strong temperature gradient away from the galactic center in all directions. Consideration of these data leads to the conclusion that the dust density decreases inward over the central 3 pc of the Galaxy, and that the central parsec of the Galaxy is remarkably devoid of dust, so that optical and ultraviolet photons may traverse it freely. The inferred total luminosity of the sources that heat the dust radiating the far-infrared emission from the central few pc of the Galaxy is 1 to 3 x to the 7th power L(Sun). It is probable that these same sources are responsible for ionizing the plasma at the galactic center.

Werner, M. W.↗

NASA NTRS1985

Trends in measurement of solar vector magnetic fields using the Zeeman effect

Trends in spectropolarimetry as applied to the problem of Zeeman effect measurement are discussed. The use of detector arrays to improve observing efficiency is obtained. Which required new polarization modulation schemes that match the time required to read detector arrays. Another significant trend is narrowband filters, to improve angular and temporal coverage, and to Fourier transform spectrometers, to improve spectral coverage and precision. Low-polarization designs and improved methods for compensating instrumental polarization were developed. A requirement for high angular resolution suggests using adaptive optical devices to subdue the effects of bad seeing. The ultimate strategy to beat the seeing is to loft the telescope above the atmosphere such as is planned with a 30-cm telescope in 1985 and a 1250-cm telescope in 1990.

Harvey, J. W.↗