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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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A low-power microscope or telescope provides a simple means of autocollimation. This is done by fitting the instrument with a light source to permit alignment from a reflecting surface normal to the optic axis of the instrument.
Circuit incorporating a bisynchronous demodulator for an electro-optical star-tracking sensor provides a signal proportional to star intensity without interference from background light in the field of view. The system works best on a sharply focused star image and requires a 50 percent duty cycle.
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A 0.5 x 0.5-m digitized spark-chamber gamma-ray telescope was flown on three balloon flights to look at the galactic center region, Virgo, and the Crab Nebula. An excess flux above atmospheric background of over 4 standard deviations was found for gamma-rays exceeding 100 MeV coming from the galactic center region, but there was no statistically significant excess in the 50-100 MeV interval. As a result, there is only a 6% chance that Compton or synchrotron radiation from electrons with a power-law spectrum having an exponent of 2.6 could make as much as a 50% contribution to the gamma-radiation in this energy range.
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New photometric observations of the BN infrared source in the Orion Nebula eliminate the possibility that it is simply a highly reddened star, and undermine the conclusion that there are 80 mag of visual extinction to the source. We suggest that there is a generic relationship between it and the infrared source IRS 5 in the H II region W3.
The Earth Resources Technology Satellite (ERTS-1) launched by NASA in July 1972 has been providing thousands of high resolution multispectral images of interest to geographers, cartographers, hydrologists, and agroculturists. It has been found possible to detect the long-range (over 50 km) transport of suspected particulate plumes from the Chicago-Gary steel mill complex over Lake Michigan. The observed plumes are readily related to known steel mills, a cement plant, refineries, and fossil-fuel power plants. This has important ramifications when discussing the interregional transport of atmospheric pollutants. Analysis reveals that the Multispectral Scanner Band 5 (0.6 to 0.7 micrometer) provides the best overall contrast between the smoke and the underlying water surface.
The Cygnus Loop was observed with a one-dimensional X-ray telescope. Data from two orthogonal scans showed no evidence for a pointlike remnant of the supernova at the center of the Loop. We set an upper limit to the presence of such a source of 2.9% (at 99.9% confidence) of the total emission in the bandwidth from 400 eV to 850 eV. The pulsed component at 62.31 msec suggested by Rappaport et al. (1973) was not observed.
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The results of the Apollo-Soyuz extreme ultraviolet (EUV)/soft X-ray diffuse background survey are analyzed to assess the contribution of discrete-sources with blackbody or coronal plasma spectra. Blackbody emitters in the EUV must be less luminous and more numerous than hot white dwarfs in order to produce the bulk of the diffuse flux. Significant contributions to the EUV background appear likely only if sufficient numbers of white dwarfs possess low temperature coronae similar to the one suggested for Sirius B.
The machine-readable version of the Astronomical Netherlands Satellite ultraviolet photometry catalog is described in detail, with a byte-by-byte format description and characteristics of the data file given. The catalog is a compilation of ultraviolet photometry in five bands, within the wavelength range 155 nm to 330 nm, for 3573 mostly stellar objects. Additional cross reference data (object identification, UBV photometry and MK spectral types) are included in the catalog.
The optical characteristics of a paraboloidal solar concentrator are analyzed using the intercept factor curve (a format for image data) to describe the results of a mathematical model and to represent reduced data from experimental testing. This procedure makes it possible not only to test an assembled concentrator, but also to evaluate single optical panels or to conduct non-solar tests of an assembled concentrator. The use of three-dimensional ray tracing computer programs to calculate the mathematical model is described. These ray tracing programs can include any type of optical configuration from simple paraboloids to array of spherical facets and can be adapted to microcomputers or larger computers, which can graphically display real-time comparison of calculated and measured data.
To optimize the procedure for evaporating a metal film onto a sphere, calculations of the film thickness distribution for various motions of the sphere have been carried out. These calculations, including shadowing effects of sphere support rods, are presented in this paper. Also, an apparatus and procedure for the evaporative coating of a sphere are described. A comparison of measured thickness with the calculated values is made for one example of sphere motion. The implications of the calculated results for coating techniques are discussed.
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The 2CG catalog of gamma ray sources was compiled before detailed knowledge was available on the fine-scale structure of the diffuse Galactic gamma-ray emission. Two independent analyses to discriminate sources which are either compact objects of due to very local and strong enhancements in the Galactic cosmic-ray distribution from those which are artifacts due to the clumpy gas distribution are about to be completed: a maximum likelihood analysis and a cross correlation analysis. Arguments are given why differences, and therefore confusion, and in resulting source lists can be expected. Detailed analysis of all COS-B gamma-ray data on Geminga (2CG195+04), reveals the existence of a drastic spectral break below 200 MeV. A power-law spectrum with index -1.88 fits the data above about 100 MeV to 3.2 GeV, however, there are also indications for a spectral break above these energies. For energies above about 100 MeV no evidence for a long-term time variability was found. The error region of Geminga was searched for a radio counterpart at wavelengths of 90, 49, 21, 6, and 2 cm using the Westerbork Synthesis Radio Telescope and the Very Large Array. So far, 16 sources were detected in this error region. In the direction of 1E0630+178, the Einstein x ray source proposed to be a Vela-like pulsar and the counterpart of Geminga, no radio source was found at 21, 49, and 90 cm with 3 sigma upper limits on the flux densities ranging from 0.5 mJy at 21 cm to 4.5 mJy at 90 cm. Detailed structures in local molecular cloud complexes are so far only resolved in gamma rays for the closet and most massive complexes, namely those in the Orion-Monoceros and the Ophiuchus regions. For both region, there is circumstantial evidence for gamma ray emission from molecular gas that was photodissociated after the passage of a SN shell.
Sources discovered by the Infrared Astronomical Satellite with spectra that rise steeply from 60 to 100 microns are a mixed sample of external galaxies, condensations in the interstellar medium, and potentially unknown astronomical objects. Sources in regions of low total H I column density (as determined with the all-sky 21-cm line surveys), and with no nearby cataloged external galaxy, were observed for presence of 20-cm continuum emission (with the NRAO VLA), enhanced 21-cm H I line emission (with the NAIC Arecibo 305 m), and molecular line emission (with the NRAO 12 m, HCRO 6 m, and FCRAO 14 m). Based on the CO detection rate, 70 percent of our sample are small interstellar molecular clouds. The remainder are mostly faint external galaxies. The dust column densities of the interstellar condensations were determined from the IR flux, using a spherical-cloud model for the radiative transfer of the interstellar radiation field (ISRF). The CO column densities were determined using the large-velocity-gradient model for the excitation and radiative transfer of the rotational transitions. About half of the interstellar sources have normal dust-to-gas ratios and ISRF heating. Sources with excess infrared emission, compared to the molecular column density, are protostellar candidates.
One of the primary goals of the Extreme Ultraviolet Explorer (EUVE) all-sky survey is the detection and identification of new sources of extreme ultraviolet radiation. Here, the challenges involved in producing a catalog containing as many statistically significant detections as possible, with a small expected number of spurious detections, are reviewed. The discussion covers simulation and testing, early survey results, advanced detection techniques, and diffuse feature detection.
It is the purpose of this paper to provide, in relatively brief form, a summary of a boundary integral approach that has been developed for calculating the sound field radiated from short ducts in uniform axial motion. The method was devised primarily to study sound generated by rotating sources in the duct, as is of current practical interest in connection with ducted-fan aircraft engines. Detailed background on the fan source application of the technique can be found. The author has not previously discussed the simpler monopole source case of interest in these proceedings. However, readers desiring a more detailed treatment than will be included here should have little difficulty in extracting it from those references after making the relatively minor modifications necessary to adapt the analyses to the monopole case. It should be noted that other authors have also considered radiation from short ducts. In particular, readers may find the finite-element approach of Eversman of interest as well as the alternate boundary integral method treatments of Martinez and of Dunn, Tweed, and Farassat.