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  • 1
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    A new convergent point and distance modulus for the Hyades from radial velocities (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The dynamics of the Hyades open star cluster is investigated analytically on the basis of the photoelectric radial velocities reported by Griffin et al. (1988). The methods used to determine the radial-velocity gradient, convergent point, and distance modulus are described, and the results are presented in tables and graphs and characterized in detail. Findings reported include convergent-point alpha = 98.2 + or - 1.1 deg and delta = 6.1 + or - 1.0 deg, space motion 48.0 + or - 0.27 km/s, distance to cluster center 45.4 + or - 2.1 pc, distance modulus 3.28 + or - 0.10, and cluster velocity dispersion 230 m/s.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 96; 198-210
    Format: text
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  • 2
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    On the detectability of infrared echo arcs around supernova 1987A (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The ring-like interstellar visual echoes of radii 33 and 54 arcsec detected around SN 1987A should coincide with infrared echoes (thermal reradiation) from dust at T approximately equal to 15 to 30 K. Whether these infrared echoes are detectable at present is considered. They will be brightest at approximately 100 microns, the range of the Texas infrared photometer. Detectability depends on the ratio zeta congruent to tan(sub a)/tan(sub s)P(theta), where tan(sub a) and tan(sub s) are the visual absorption and scattering optical thicknesses of the echo layer, and P is the phase function function for small-angle scattering (theta approximately equal to 2 to 4 degrees). Zeta approximately greater than 1 is needed for a detectable signal (approximately 0.3 Jy), but zeta cannot be much less than 1; otherwise the visual echoes could not be as bright as they are. Typical dust mixtures of Mathis-Rumpl-Nordsieck type have zeta much less than 1. Zeta remains small even if a population of very small grains with power-law index as steep as approximately 5.5 is added. A population with even more small grains and/or fewer large grains could have a zeta similar to 1 and be detectable at present, but this seems unlikely. The echoes will move, but should remain accessible for many years and should be detected eventually.
    Keywords: ASTRONOMY
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 549-552
    Format: application/pdf
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  • 3
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    NASA Marshall Space Flight Center Solar Observatory report, October - December 1990 (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is provided, and a summary of its observations and data reduction during Oct. - Dec. 1990 is presented. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
    Keywords: ASTRONOMY
    Type: NASA-TM-103532 , NAS 1.15:103532
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  • 4
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    NASA Marshall Space Flight Center Solar Observatory report, July - September 1990 (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A description of the NASA Marshall Space Flight C nter's Solar Vector Magnetograph Facility is provided and gives a summary of its observations and data reduction during Jul. - Sep. 1990. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
    Keywords: ASTRONOMY
    Type: NASA-TM-103531 , NAS 1.15:103531
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  • 5
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    NASA Marshall Space Flight Center Solar Observatory report, July - December 1991 (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A summary is given of the solar vector magnetic field, H-alpha, and white light observations made at the NASA/Marshall Space Flight Center (MSFC) Solar Observatory during its daily periods of observation. The MSFC Solar Observatory facilities consist of the Solar Magnetograph, an f-13, 30 cm Cassegrain system with a 3.5 cm image of the Sun housed on top of a 12.8 meter tower, a 12.5 cm Razdow H-alpha telescope housed at the base of the tower, an 18 cm Questar telescope with a full aperture white-light filter mounted at the base of the tower, a 30 cm Cassegrain telescope located in a second metal dome, and a 16.5 cm H-alpha telescope mounted on the side of the Solar Vector Magnetograph. A concrete block building provides office space, a darkroom for developing film and performing optical testing, a workshop, video displays, and a computer facility for data reduction.
    Keywords: ASTRONOMY
    Type: NASA-TM-103577 , NAS 1.15:103577
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  • 6
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    NASA Marshall Space Flight Center Solar Observatory report, January - June 1992 (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during Jan. to Jun. 1992. The systems that make up the facility are a magnetograph telescope, and H-alpha telescope, a Questar telescope, and a computer code.
    Keywords: ASTRONOMY
    Type: NASA-TM-103597 , NAS 1.15:103597
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  • 7
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    Doppler imaging of AR Lacertae at three epochs (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations from IUE were used to study the structure of the lower chromosphere of AR Lacertae in the light of Mg II k. Sequences of LWR/P-HI images distributed around the binary period at three epochs were obtained. Discrete plage-like regions of enhanced Mg II surface flux in this system are identified. There are temporal variations in the Mg II flux on timescales of hours as well as substantial changes in chromospheric morphology on timescales of years. Even with the limited S/N attainable with the IUE, one can map the gross structures of active stellar atmospheres. With such information, one can begin to study the true 3-D structure of the atmospheres of late-type stars.
    Keywords: ASTRONOMY
    Type: ESA, A Decade of UV Astronomy with the IUE Satellite, Volume 1; p 295-297
    Format: application/pdf
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  • 8
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    Imaging phased telescope array study (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The problems encountered in obtaining a wide field-of-view with large, space-based direct imaging phased telescope arrays were considered. After defining some of the critical systems issues, previous relevant work in the literature was reviewed and summarized. An extensive list was made of potential error sources and the error sources were categorized in the form of an error budget tree including optical design errors, optical fabrication errors, assembly and alignment errors, and environmental errors. After choosing a top level image quality requirment as a goal, a preliminary tops-down error budget allocation was performed; then, based upon engineering experience, detailed analysis, or data from the literature, a bottoms-up error budget reallocation was performed in an attempt to achieve an equitable distribution of difficulty in satisfying the various allocations. This exercise provided a realistic allocation for residual off-axis optical design errors in the presence of state-of-the-art optical fabrication and alignment errors. Three different computational techniques were developed for computing the image degradation of phased telescope arrays due to aberrations of the individual telescopes. Parametric studies and sensitivity analyses were then performed for a variety of subaperture configurations and telescope design parameters in an attempt to determine how the off-axis performance of a phased telescope array varies as the telescopes are scaled up in size. The Air Force Weapons Laboratory (AFWL) multipurpose telescope testbed (MMTT) configuration was analyzed in detail with regard to image degradation due to field curvature and distortion of the individual telescopes as they are scaled up in size.
    Keywords: ASTRONOMY
    Type: NASA-CR-183661 , NAS 1.26:183661 , PR-B11-0064
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  • 9
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    NASA Marshall Space Flight Center Solar Observatory report, January - June 1990 (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility is presented and a summary of its observations and data reduction is given. The systems that make up the facility are a magnetograph telescope, an H alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
    Keywords: ASTRONOMY
    Type: NASA-TM-103512 , NAS 1.15:103512
    Format: application/pdf
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  • 10
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    NASA Marshall Space Flight Center solar observatory report, January - December 1987 (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report provides a description of the NASA Marshall Space Flight Center's Solar Vector Magnetograph Facility and gives a summary of its observations and data reduction during January to December 1987. The systems that make up the facility are a magnetograph telescope, an H-alpha telescope, a Questar telescope, and a computer code. The data are represented by longitudinal contours with azimuth plots.
    Keywords: ASTRONOMY
    Type: NASA-TM-100360 , NAS 1.15:100360
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