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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

A scanning modulation collimator observation of the high-energy X-ray source in the Crab Nebula

Two-dimensional maps of the 22-64 keV emission from the Crab Nebula with an angular resolution of 15 arcsec has been synthesized. The maps are generated by application of a maximum entropy method operating on a series of one-dimensional scans obtained with a balloon-borne modulation collimator telescope. The two-dimensional size, shape and orientation of the hard X-ray nebula relative to the pulsar have been measured for the first time. The implications of these results for models of electron transport in the Crab are discussed, and the geometry of the observed X-ray nebula is related to other features of the Crab Nebula system.

Pelling, R. M.↗
NASA NTRS1987

Performance of moire deflectometry with deferred electronic heterodyne readout

The effects of diffraction and nonlinear photographic emulsion characteristics on the performance of deferred electronic heterodyne moire deflectometry are theoretically and experimentally investigated. The intensity transmission distribution of the transparency, the moire image, the heterodyne readout, and the spatial and angular resolution are analytically discussed. The deferred electronic heterodyne technique is evaluated by measuring small fringe shifts caused by a weak phase object. It is found that this technique can be applied for accurate and sensitive readout of moire fringes of unsteady phase objects. The theoretical study shows that the accuracy and sensitivity of the system are weakly affected by diffraction and nonlinear photographic emulsion characteristics. Nonlinear recording does not affect the spatial resolution of the system.

Stricker, Josef↗
NASA NTRS1988

Compact Sun-Position Sensor

Single device finds and tracks Sun. New sensor has both wide field of view and high angular resolution when axis within few degrees of the line to the Sun.

Matsumoto, Yutaka↗
NASA NTRS1987

Low frequency VLBI in space using GAS-Can satellites: Report on the May 1987 JPL Workshop

Summarized are the results of a workshop held at JPL on May 28 and 29, 1987, to study the feasibility of using small, very inexpensive spacecraft for a low-frequency radio interferometer array. Many technical aspects of a mission to produce high angular resolution images of the entire sky at frequencies from 2 to 20 MHz were discussed. The workshop conclusion was that such a mission was scientifically valuable and technically practical. A useful array could be based on six or more satellites no larger than those launched from Get-Away-Special canisters. The cost of each satellite could be $1-2M, and the mass less than 90 kg. Many details require further study, but as this report shows, there is good reason to proceed. No fundamental problems have been discovered involving the use of untraditional, very inexpensive spacecraft for this type of mission.

Mahoney, M. J.↗
NASA NTRS1987

Detection of a very bright source close to the LMC supernova SN 1987A

High angular resolution observations of the supernova in the Large Magellanic Cloud, SN 1987A, have revealed a bright source separated from the SN by approximately 60 mas with a magnitude difference of 2.7 at 656 nm (H-alpha). Speckle imaging techniques were applied to data recorded with the CfA two-dimensional photon counting detector on the CTIO 4 m telescope on March 25 and April 2 to allow measurements in H-alpha on both nights and at 533 nm and 450 nm on the second night. The nature of this object is as yet unknown, though it is almost certainly a phenomenon related to the SN.

Nisenson, P.↗
NASA NTRS1987

Determination of the masses of elliptical galaxies and clusters of galaxies with AXAF

The procedures to be used in the determination of the mass and mass distribution of elliptical galaxies and clusters of galaxies, using spatially resolved X-ray spectra of galaxies and clusters of galaxies to be obtained by the imaging spectrometers on AXAF, are described. The procedures utilize the unique AXAF features of large band width, large field of view, high angular resolution, long exposure times, and the availability of sophisticated AXAF instrumentation. The techniques described involve the measurement of the surface brightness and temperature profiles of the hot gas trapped in the potential wells of these systems. Then, by using the equation of hydrostatic equilibrium, which relates the total mass inside a given radius to the size, absolute temperature, density gradient, and temperature profile, it will be possible to infer the mass distribution in these objects to large physical scales.

Mushotzky, Richard F.↗
NASA NTRS1988

H2 and H I emission line imaging of the ring nebula (NGC 6720)

Infrared emission-line images of the v = 1-0 S(1) transition of molecular hydrogen and Br-gamma recombination line of atomic hydrogen which cover the entire extent of NGC 6720, the Ring nebula. The maps presented here are the highest angular resolution images of these transitions yet produced for this object and have very low relative positional uncertainty. As a result, the spatial stratification of the ionized and shocked molecular zones within the nebula is clearly resolved. These data, and data from the Infrared Astronomical Satellite, are used to determine the H2, H I, and dust mass within the nebula. Energy sources for the dust heating, formation and destruction of the H2, and overall evolution of the nebula are also discussed.

Greenhouse, Matthew A.↗
NASA NTRS1988

High throughput X-ray optics - An overview

Techniques for the production of high-throughput modular arrays of telescopes with net collecting areas exceeding 10 to the 5th sq cm and 20-arsec angular resolution are discussed. Techniques considered include the automated figuring of flats as parabolic reflectors, the replication of cylindrical shells, the alignment of thin lacquer-coated conical foils, electroforming, and the use of large diamond turning machines. High-throughput programs are described, and it is noted that future missions will emphasize high resolution spectroscopy.

Gorenstein, Paul↗
NASA NTRS1988

X-ray performance of the LAMAR protoflight mirror

A grazing incidence X-ray mirror in the Kirkpatrick-Baez geometry was constructed and tested. Its geometric aperture measures 20 by 30 cm and its length is 100 cm. The focal length is 3.4 m measured from the front to the focal plane. It is the first of eight mirrors to be built for the LAMAR experiment of the Shuttle High Energy Astrophysics Laboratory. Its angular resolution was measured at 1.5 and 6.4 keV in a quasi-parallel X-ray beam at the Marshall Space Flight Center. The half-power width (HPW) of the resolution function projectd along a horizontal axis is 31-sec of arc at both energies and in visible light. With the addition of small isolation pads the mirror is able to withstand the vibration and acceleration levels of a Space Shuttle launch. The resolution remains under 35-sec of arc HPW for changes in temperature of 9.5 C and when a modest temperature gradient is imposed on the mirror.

Fabricant, Daniel G.↗
NASA NTRS1988

An electroformed mirror array for high energy X-ray astronomy

A design for a mirror array telescope for high energies with almost 1000 sq cm effective area at 7 keV is described. Briefly, it consists of 36 modules. Each module contains Wolter I mirrors nested 6 deep. The system is small enough to be flown on an Aries rocket. With the current mirrors, the angular resolution at high contrast is 20 arcsec and the half power diameter for images is 1.5 arcmin at 1.5 keV and 3.5 arcmin - 4 arcmin at 7 keV. Plans to improve upon this performance are discussed.

Ulmer, Melville P.↗
NASA NTRS1989

Very-Long-Baseline Interferometry Using Cheap Satellites

Celestial radiation below 25 MHz, heretofore inaccessible, yields new insights. Report discusses feasibility of array of small satellites deployed in high orbit around Earth to monitor celestial radio sources at frequencies less than 25 MHz. Objective to make high-angular-resolution map of such sources over entire sky by use of very-long-baseline interferometry (VLBI).

Mahoney, M. J.↗
NASA NTRS1988

Scientific tradeoffs in pinhole/occulter facility accommodation

The Pinhole/Occulter Facility (P/OF) consists of state-of-the-art instruments for the study of particle acceleration in the solar corona, and uses a large structure to obtain very high angular resolution. P/OF has been studied in the past as an attached payload for the Space Shuttle, and has been the subject of study by a NASA Science Working Group (P/OFSWG). Appendix A lists various technical studies and reports carried out under the auspices of P/OFSWG and the Program Development Office of NASA Marshall Space Flight Center. Under the rationalization of NASA flight opportunities following the Challenger disaster, and the beginning of the Space Station Freedom program, the sortie-mode deployment of P/OF seemed less efficient and desirable. Thus, NASA decided to reconsider P/OF for deployment on the Space Station Freedom. The technical studies for this deployment continue at the present and will evolve as our knowledge of Space Station architecture and capabilities increase. MSFC contracted with Teledyne Brown Engineering for these technical studies.

Hudson, Hugh S.↗
NASA NTRS1988

Imaging solar flares in hard X-rays and gamma raysfrom balloon-borne platforms

Hard X-rays and gamma rays carry the most direct evidence available for the roles of accelerated particles in solar flares. An approach that employs a spatial Fourier-transform technique for imaging the sources of these emissions is described and plans for developing a balloon-borne gamma ray imaging device (GRID) based on this instrumental approach is presented. This instrument, GRID on a balloon, would enable observations with a 1.6 arcsecond angular resolution, 10 millisecond time resolution, and whole-Sun field of view on long-duration balloon flights during MAX 1991.

Crannell, Carol JO↗
NASA NTRS1988

SIRTF and star formation

Four problems in the field of star formation that can be attacked to advantage with SIRTF are discussed: (1) the patterns of star formation in spiral galaxies, (2) the physical mechanism for bimodal star formation, (3) the nature of bipolar outflows from young stellar objects, and (4) the birth of brown dwarfs. In each case, SIRTF can provide the crucial combination of high angular resolution with great sensitivity over a broad range of wavelengths that is needed to address the relevant issues.

Shu, Frank H.↗
NASA NTRS1988

Low frequency VLBI

There are many important astrophysical questions which could be answered with observations at frequencies of a few MHz and angular resolution of an arcmin or better. For example, strong interstellar and interplanetary scattering of EM radiation could be studied along many lines of sight, and the sizes and shapes of scattering disks could be directly measured as a function of time and frequency. Such data can be obtained with an interferometer array composed of several small satellites in earth orbit. The individual satellites for an LF array could be very small and inexpensive.

Jones, Dayton L.↗
NASA NTRS1988

The All Sky Monitor for the X-ray Timing Explorer

The All Sky Monitor (ASM) for the X-ray Timing Explorer (XTE), whose purpose is to record a photometric history of known objects and to detect and locate transient objects, is discussed. This instrument uses the multiple pinhole approach to avoid photon starvation for good photometric capability together with good angular resolution and an excellent capability for locating transients. While the XTE ASM does not have the ideal imaging qualities of the uniformly redundant array-based designs, it is simpler to build and requires a modest telemetry bandwidth; since the ASM is intended for detection, location, and photometry of discrete point sources, imaging is of secondary importance.

Doty, John P.↗
NASA NTRS1989

Deferred electronic heterodyne moire deflectometry: A method for transient density fields measurement

Effects of spherical aberrations of the mirror used in the moire system on the angular resolution of the system are investigated. It is shown that the spherical aberrations may reduce significantly the performance of the conventional moire deflectometer. However, due to the heterodyne procedure, this is not the case with the heterodyne moire system. A moire system with a constant speed moving grating is demonstrated. It is shown that the system readout is linear and the system does not need calibration. In addition, the repeatability of the measurements is improved in this system as compared to the sinusoidally moving grating setup. The problem of the photographic plates alignment is solved by using a mechanical system in which the plate is held firmly throughout the experiment and accurately replaced after removing for photographic processing. The effect of a circular detector's aperture size on readout was tested. It is shown that the spatial phase variations, observed when scanning along a straight moire fringe, may considerably be reduced. At present we may say that both the on-line and the deferred heterodyne moire techniques may reliably be used. The errors of phase readings are 1 deg and 5 deg for the on-line and deferred methods. The total error due to subtraction of two readings at each position is, therefore, 1.4 deg and 7 deg, respectively. Further research for improving the deferred system is suggested.

Stricker, Josef↗
NASA NTRS1989

Stratospheric Observatory for Infrared Astronomy (SOFIA) system concept

The system concept for the Stratospheric Observatory for Infrared Astronomy (SOFIA), as developed by NASA Ames Research Center is described. The SOFIA facility is a 3-meter class optical/infrared/submillimeter telescope mounted in an open cavity in the forebody of a Boeing 747 aircraft, to be operational in 1992. It represents the next generation of Ames' existing airborne IR facilities, and is about ten times more sensitive than the Kuiper Airborne Observatory (KAO) with 3 times better angular resolution, and able to detect all the far-infrared point sources discovered by IRAS (Infrared Astronomical Satellite) survey in 1983. Major requirements and design attributes of the SOFIA telescope are presented, along with a brief description of the Ground Support/Operations System.

Wiltsee, Christopher B.↗