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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 127 records · Page 7
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NASA NTRS1979

X-ray observations of the 5 March 1979 gamma-burst field

An extremely intense burst of hard X-rays and gamma-rays that was recorded by the nine interplanetary spacecraft of the burst sensor network and localized by time-of-flight determinations to a position coincident with the supernova remnant N49 in the Large Magellanic Cloud is analyzed. The region of the sky was observed both before and after the gamma-ray event with the soft X-ray imaging instruments aboard the Einstein Observatory. Coupled with the optical plate material, the soft X-ray data is used to place severe constraints on models for the origin of the transient phenomena.

Helfand, D. J.↗
NASA NTRS1982

Low intensity X-ray and gamma-ray spectrometer

A low intensity X-ray and gamma ray spectrometer for imaging, counting, and energy resolving of single invisible radiation particles is described. The spectrometer includes a converting device for converting single invisible radiation particles to visible light photons. Another converting device converts the visible light photons to photoelectrons. A fiber optics coupling device couples together the two converting devices. An intensifying device intensifies the photoelectrons by an average gain factor of between 10 to the 4th power and 10 to the 7th power. The tensifying device is an anti-ion feedback microchannel plate amplifier which is operated substantially below saturation. A displaying device displays the intensified photoelectrons. The displaying device 32 indicates the spatial position, number, and energy of the incoming single invisible radiation particles.

Yin, L. I.↗
NASA NTRS1983

Constraints on gamma-ray bursters from soft X-ray transients

The Columbia Astrophysics Laboratory's Einstein imaging proportional counter database has been searched for possible X-ray counterparts to gamma ray bursts. The limiting sensitivity was about 10 to the 10th erg/sq cm with a total exposure of about 3 x 10 to the 6th s divided among about 1000 1 deg x 1 deg fields. Four events with a pointlike spatial distribution were detected but their extremely soft spectra makes them unlikely candidates for gamma ray burst counterparts. The results are used to place limits on the X-ray and gamma ray luminosity ratio and log(number)N-log(flux)S relation for gamma ray bursts. The constraints placed on models for their origin are commented on.

Helfand, D. J.↗
NASA NTRS1983

NASA astrophysics - Optical systems to explore the universe

Major and minor NASA astrophysical research efforts in the near-term are outlined, together with projections of direction for future projects. The Space Telescope is being readied for a 1986 launch and will feature an f/24, 2.4 m aperture, an MgF2 mirror with better than 1/60 wavelength accuracy and will be diffraction-limited in the UV. Pointing accuracy is designed to be 0.007 arcsec for 24 hr. Optical, spectrometric, and photometric equipment will be included. Around 1990, Shuttle-based missions will include an IR telescope and a subarcsec solar surface imaging device. A free-flying X-ray observatory (AXAF) is planned and will include a sensitivity that exceeds that of the HEAO-2 spacecraft by two orders of magnitude. Instruments are under development for higher resolution UV, gamma-ray, and IR studies. In-orbit interferometry is being studied and will depend on in-orbit assembly and servicing of stable structures with segmented optics.

Pellerin, C. J., Jr.↗
NASA NTRS1985

Observations of the Crab Nebula at energies 4.10(11)

Since the development of gamma-ray astronomical telescopes, the Crab Nebula has been a prime target for observations. From 100 to 1000 MeV, the pulsar PSR0531 is the dominant source with a light-curve similar to that seen at lower energies; there is also some evidence for longterm amplitude variations but none for emission from the Nebula itself. In the very high energy gamma-ray region there have been reported detections of pulsed emission with longterm time variations from minutes to months. Recently a pulsed flux has been reported that resisted over a long time interval. The detection of a flux from the Nebula at the 3 sigma level at energies of 3x1011eV was reported; there was no evidence of periodic emissions on any time scale during the three years of observations. A new measurement of very high energy gamma rays from the Crab Nebula is reported using the imaging system on the Whipple Observatory 10m reflector.

Cawley, M. F.↗
NASA NTRS1986

Results from the solar maximum mission

The major results from SMM (Solar Max Mission) are presented as they relate to the understanding of the energy release and particle transportation processes that led to the high energy X-ray aspects of solar flares. Evidence is reviewed for a 152- to 158-day periodicity in various aspects of solar activity including the rate of occurrence of hard X-ray and gamma-ray flares. The statistical properties of over 7000 hard X-ray flares detected with the Hard X-Ray Burst Spectrometer are presented including the spectrum of peak rates and the distribution of the photo number spectrum. A flare classification scheme is used to divide flares into three different types. Type A flares have purely thermal, compact sources with very steep hard X-ray spectra. Type B flares are impulsive bursts which show double footpoints in hard X-rays, and soft-hard-soft spectral evolution. Type C flares have gradually varying hard X-ray and microwave fluxes from high altitudes and show hardening of the X-ray spectrum through the peak and on the decay. SSM data are presented for examples of Type B and Type C events. New results are presented showing coincident hard X rays, O V, and UV continuum observations in Type B events with a time resolution of 128 ms. The subsecond variations in the hard X-ray flux during 10% of the stronger events are discussed and the fastest observed variation in a time of 20 ms is presented. The properties of Type C flares are presented as determined primarily from the non-imaged hard X-ray and microwave spectral data. A model based on the association of Type C flares and coronal mass ejections is presented to explain many of the characteristics of these gradual flares.

Dennis, B. R.↗
NASA NTRS1986

Development of the instruments for the Gamma Ray Observatory

The Gamma Ray Observatory (GRO) is to be launched in 1988 by the STS. The GRO will feature four very large instruments: the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), the Energetic Gamma Ray Experiment Telescope (EGRET) and the Burst and Transient Source Experiment (BATSE). The instruments weigh from 900-1200 kg each, and required the development of specialized lifting and dolly devices to permit their assembly, manipulation and testing. The GRO is intended a{s a tool for studying discrete celestial objects such as black holes, neutron stars and other gamma-ray emitting objects, scanning for nucleosynthesis processes, mapping the Galaxy and other, high energy galaxies in terms of gamma rays, searching for cosmological effects and observing gamma ray bursts. The instruments will be sensitive from the upper end mof X-rya wavelengths to the highest energies possible. Details of the hardware and performance specifications of each of the instruments are discussed.

Madden, J. J.↗
NASA NTRS1986

Impulsive phase transport

The transport of nonthermal electrons is explored. The thick-target electron beam model, in which electrons are presumed to be accelerated in the corona and typically thermalized primarily in the chromosphere and photosphere, is supported by observations throughout the electromagnetic spectrum. At the highest energies, the anisotropy of gamma-ray emission above 10 MeV clearly indicates that these photons are emitted by anisotropically-directed particles. The timing of this high-energy gamma-radiation with respect to lower-energy hard X-radiation implies that the energetic particles have short life-times. For collisional energy loss, this means that they are stopped in the chromosphere or below. Stereoscopic (two-spacecraft) observations at hard X-ray energies (up to 350 keV) imply that these lower-energy (but certainly nonthermal) electrons are also stopped deep in the chromosphere. Hard X-ray images show that, in spatially resolved flares whose radiation consists of impulsive bursts, the impulsive phase starts with X-radiation that comes mostly from the foot-points of coronal loops whose coronal component is outlined by microwaves.

Canfield, Richard C.↗
NASA NTRS1986

A Fourier transform telescope for sub-arcsecond imaging of X-rays and gamma rays

This paper describes a Fourier transform telescope designed to image solar flare X-rays and gamma rays at energies up to 1 MeV with arcsec resolution. The imaging technique makes use of a bigrid collimator divided into a number of smaller areas called subcollimators. The grids in each subcollimator consist of a set of linear apertures so configured that each subcollimator provides a measurement of a single Fourier component of the angular distribution of the source. The imaging concept is therefore a mathematical analog to aperture synthesis in radio astronomy. For X-ray and gamma-ray astronomy, this approach has significant advantages in terms of relaxed requirements for astronomy, this approach has significant advantages in terms of relaxed requirements for position sensitivity in the detector and for control of grid alignment in the large scale telescope structure. The concept of the Fourier transform telescope will be illustrated with numerical parameters of a version now under study for the Pinhole/Occulter Facility.

Crannell, C. J.↗
NASA NTRS1986

Search for optical flashes from gamma-ray bursters

Preliminary results of an investigation of the Ondrejov and Sonneberg plate collections for possible optical counterparts to gamma ray bursters (GRBs) are presented. The study proceeds in three directions: as time-correlated searches for GRBs with known positions, as time-correlated searches for GRBs without known positions, and as archival searches. The position of the Perseus flasher was also investigated using 1000 hours of monitoring. No evidence for true optical images associated with GRBs was found. Statistical conclusions are drawn and discussed.

Hudec, R.↗
NASA NTRS1988

Imaging Of Directional-Solidification Interfaces

X-ray and gamma-ray technique developed at NASA Langley Research Center enables melt/solid interface to be observed visually during crystal growth by directional solidification in Bridgman furnace. Technique used to observe movement and shape of interface in germanium and in lead tin telluride. Valuable tool in efforts to grow seeded semiconductor materials in Bridgman furnaces.

Fripp, Archibald L., Jr.↗
NASA NTRS1989

The solar gamma ray and neutron capabilities of COMPTEL on the Gamma Ray Observatory

The imaging Compton telescope COMPTEL on the Gamma Ray Observatory (GRO) has unusual spectroscopic capabilities for measuring solar gamma-ray and neutron emission. The launch of the GRO is scheduled for June 1990 near the peak of the sunspot cycle. With a 30 to 40 percent probability for the Sun being in the COMPTEL field-of-view during the sunlit part of an orbit, a large number of flares will be observed above the 800 keV gamma-ray threshold of the telescope. The telescope energy range extends to 30 MeV with high time resolution burst spectra available from 0.1 to 10 MeV. Strong Compton tail suppression of instrumental gamma-ray interactions will facilitate improved spectral analysis of solar flare emissions. In addition, the high signal to noise ratio for neutron detection and measurement will provide new neutron spectroscopic capabilities. Specifically, a flare similar to that of 3 June 1982 will provide spectroscopic data on greater than 1500 individual neutrons, enough to construct an unambiguous spectrum in the energy range of 20 to 200 MeV. Details of the instrument and its response to solar gamma-rays and neutrons will be presented.

Ryan, James M.↗
NASA NTRS1990

Calibration and performance of the UCR double Compton gamma ray telescope

Results of the field calibration and performance of the UCR double Compton gamma-ray telescope are presented. The telescope is a balloon-borne instrument with an upper array of 16 plastic scintillator bars and a lower one of 16 NaI(Tl) bars. The telescope is sensitive to celestial gamma rays from 1 to 30 MeV. The data were collected on February 14, 1988 prior to launch in Alice Springs, Australia to observe SN 1987A. Radioactive sources were used to calibrate the energy deposits in the scintillators. Each bar was analyzed laterally using pulse height or timing to obtain the positions of the gamma ray interactions. Double scatter events from an Na-24 source simulating a celestial source were studied to obtain the general performance of the telescope and to develop imaging techniques, later used with the flight data. An angular resolution of 11 deg FWHM and energy resolutions of 13 and 10 percent FWHM at 1.37 and 2.75 MeV, respectively, were found. The efficiency of the telescope is 0.0035 at 1.37 MeV and zenith angle 31 deg.

Ait-Ouamer, Farid↗
NASA NTRS1991

The gamma-ray observatory

An overview is given of the Gamma Ray Observatory (GRO) mission. Detection of gamma rays and gamma ray sources, operations using the Space Shuttle, and instruments aboard the GRO, including the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET) are among the topics surveyed.

Source record↗
NASA NTRS1991

The Solar-A mission - An overview

An overview of the Solar-A spacecraft, launched in August 1991, is presented. This mission is dedicated primarily to the study of solar flares, especially of high-energy phenomena observed in the X- and gamma-ray ranges. With a coordinated set of instruments, including hard X-ray and soft X-ray imaging telescopes as well as spectrometers with advanced capabilities, it is expected to reveal many new aspects of flares and help better understand their physics, supporting international collaboration with ground-based observatories as well as theoretical investigations. The scientific instruments of Solar-A, especially the soft X-ray telescope, require sophisticated control of flight operations to exploit their capabilities with the constraints of the telemetry data rate and the capacity of the data recorder; this is achieved by the 'data processor' unit. Objectives include flare-related phenomena, dynamical phenomena not necessarily related to flares, and global coronal structure.

Ogawara, Y.↗
NASA NTRS1990

EXOSS - A hard X-ray and soft gamma-ray astronomy mission

The Energetic X-ray Observatory on Space Station (EXOSS) is a mission concept for high-sensitivity coded-aperture sky surveys and studies of the spectral and temporal behavior of astrophysical sources from approximately 3 keV to 1 MeV. The scientific motivation for the mission and the instrument requirements, including the need for high angular resolution to resolve and identify numerous detectable sources, are summarized. Two baseline telescopes are described: one employing a 1.4-sq-m array of Xe gas imaging proportional counters to cover the 3 to 100 keV range with 1 arcmin resolution; the second using a 2.8-sq-m array of NaI/CsI imaging phoswich detectors to span the 20 keV to MeV range with 12 arcmin resolution.

Cook, W. R.↗
NASA NTRS1990

Development of a scintillating optical fiber ionization calorimeter

A design study of a scintillation fiber (SF) calorimeter for a cosmic ray observation is made. An evaluation of various fibers and design configuration was made. The proposed design has a dimension of 1 m (W) x 1 m (L) x 16 cm (H) contains 1000 fibers at each of 40 x- or 40 y-layers interleaved with 1mm thick leadplates. Two or four CCD Particle Track Imaging Systems are connected to a bundle of SF edges at x- and y-ends. The overall weight of a calorimeter is 1,200 kg including read-out systems and supporting boards. The designed calorimeter can measure cosmic ray nuclei and gamma-rays with position, angles and energy information suitable for detailed spectrum analysis. The system is particularly beneficial at very high energies where the flux is extremely low and it requires a very long exposure over many years in space. Emulsion chambers have an advantage for cosmic ray measurements if the exposure is limited to several months in space. In fact, the most important energy region for the current cosmic ray studies is at around 1,000 TeV where a drastic change of elemental composition is indicated by various indirect observations. A detector whose size is in the order of 1 m(sup 2) requires several years of exposure in space accumulate sufficient statistics near 1,000 TeV. Emulsions will be strongly contaminated by background radiation for such a long duration flight, while SF calorimeter is totally immune from this concern. This is particularly important for long-duration experiments. The SF calorimeter also allows time-tagging of individual events, extending the experimental capability in various ways.

Takahashi, Y.↗