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  • SOLAR PHYSICS  (15)
  • SPACECRAFT INSTRUMENTATION  (11)
  • 1
    Publication Date: 2011-08-24
    Description: A discussion is presented of the scientific objectives that can be pursued by simultaneous coronal/chromospheric observation with the Multi-Spectral Solar Telescope Array (MSSTA), and a new balloon-borne observatory called the Ultra-High Resolution Vacuum Ultraviolet Spectroheliograph (UHRVS). Attention is given to the proposed UHRVS observatory, which will incorporate two instruments, a 65-cm aperture telescope with narrowband filters for high resolution photographic and photoelectric spectroheliograms, and a very high resolution spectrograph which uses a 40-cm aperture telescope. The capabilities of the MSSTA, and the joint UHRVS/MSSTA observing program that is envisioned are reviewed.
    Keywords: SOLAR PHYSICS
    Type: In: Multilayer and grazing incidence X-ray(EUV optics for astronomy and projection lithography; Proceedings of the Meeting, San Diego, CA, July 19-22, 1992 (A93-39601 15-74); p. 630-645.
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  • 2
    Publication Date: 2006-01-16
    Description: Available data on the solar spectral irradiances at wavelengths below 3100 A are extremely limited and there are major uncertainties in many of the measurements. In particular, there is major disagreement on the magnitude of the variability of the spectral irradiances over the solar cycle. The effects of different solar features on the ultraviolet spectral irradiances over both the 28 day solar rotation period and over the solar cycle are discussed. It is proposed that any attempt to predict the magnitudes of the ultraviolet spectral irradiances must take into account a long term variability of emission from quiet regions of the solar disk over the solar cycle. The need for direct long term monitoring of the ultraviolet spectral irradiances is emphasized.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 280-321
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  • 3
    Publication Date: 2006-01-16
    Description: The need for long term solar activity predictions is addressed. The spatial organization of solar activity is described including applications for predictions, and ancient evidence for solar variability. Methods of predicting sunspot numbers are discussed. The inherent accuracy of the methods varies considerably, but a typical error bar 20%. The accuracy of sunspot cycle predictions is considered along with long term predictions of great solar events.
    Keywords: SOLAR PHYSICS
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 246-257
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  • 4
    Publication Date: 2019-06-28
    Description: The multi-anode microchannel arrays (MAMAs) are state-of-the-art, pulse-counting, photoelectric array detectors designed specifically for use in space astrophysics instruments. The present paper provides a description of recent progress related to the development of ultraviolet and visible-light versions of the MAMA detectors, taking into account a comparison of the operating characteristics of these devices with those of photoconductive array detectors, such as the CCDs. Attention is given to MAMA detector system design parameters, the operating characteristics of MAMAs and CCDs, MAMA performance characteristics, and future developments.
    Keywords: SPACECRAFT INSTRUMENTATION
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  • 5
    Publication Date: 2019-06-28
    Description: Multi-Anode Microchannel Array (MAMA) detector systems are being fabricated and tested for use in the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) and the Ultraviolet Coronagraph Spectrometer (UVCS) instruments on the ESA/NASA Solar and Heliospheric Observatory (SOHO) mission. The SOHO MAMA detector systems have formats of 360 x 1024 pixels and pixel dimensions of 25 x 25 sq microns and are optimized for operation at Extreme Ultraviolet (EUV) wavelengths between 40 and 160 nm. In this paper we report on the initial results of measurements of the performance characteristics of the first flight-configuration detector system employing the new custom Application Specific Integrated Circuits (ASICs) which are designed to improve both the dynamic range and the uniformity of response. The performance characteristics of this detector system are compared with those of earlier breadboard systems employing discrete-component electronics circuits.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: In: Ultraviolet technology IV; Proceedings of the Meeting, San Diego, CA, July 20, 21, 1992 (A93-34426 13-35); p. 83-93.
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  • 6
    Publication Date: 2019-06-27
    Description: Full-disk solar spectral irradiances at solar maximum were obtained in the spectral range 1200-2550 A at a spectral resolution of approximately 1 A from rocket observations above White Sands, New Mexico, on June 5, 1979. Comparison with measurements made near solar minimum indicates approximately a factor of 2.5 increase in the irradiance at 1200 A, a 20% increase near 1800 A, and no increase within our measurement errors (+ or - 15%) above 2100 A. Irradiances in the range 1800-2100 A are in excellent agreement with previous measurements, but those in the 2100- to 2550-A range are significantly lower. The intensities of strong emission lines at wavelengths below 1850 A are also reported.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research; 85; Aug. 1
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  • 7
    Publication Date: 2019-06-27
    Description: Construction and mode of operation are described for a sounding rocket spectroheliometer used to establish the sensitivity of the EUV spectroheliometer on the Skylab Apollo Telescope Mount (ATM). The sounding rocket instrument was calibrated immediately before and after two flights and the calibration was transferred when the rocket and ATM instruments simultaneously measured the average intensity emitted by a quiet area of the solar disk. Descriptions are presented for the payload assembly and flight sequence, the optical system (telescope, spectrometer, and pointing reference camera), the vacuum pumping system, and the instrument electronics. Results obtained from the two flights in August and December 1973 are discussed, which included unambiguous determinations of the absolute intensity emitted by a region of the quiet solar disk over the wavelength range from 1350 to 300 A on two separate occasions and the establishment of photometric accuracy to that of laboratory calibration procedures.
    Keywords: SOLAR PHYSICS
    Type: Space Science Instrumentation; 1; Feb. 197
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  • 8
    Publication Date: 2019-07-27
    Description: The Harvard College Observatory photoelectric spectroheliometer on the Apollo Telescope Mount operated correctly in orbit from May 29, 1973 to Feb. 7, 1974. During this period many thousands of spatial and spectral scans at extreme ultraviolet wavelengths were recorded during observations of a variety of solar features. The construction and modes of operation of the instrument are outlined and the principal scientific results from a preliminary analysis of the data are described.
    Keywords: SOLAR PHYSICS
    Type: AIAA PAPER 74-1258
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  • 9
    Publication Date: 2019-06-27
    Description: We have analyzed the time structure of the intensity of solar chromospheric and coronal extreme-ultraviolet lines, obtained by the Harvard College Observatory spectrometer aboard Skylab. We find changes in the intensity of up to 50 percent in times as short as 1 minute, but not periodic oscillations. Some evidence is found for the presence of shock waves in the chromosphere and the transition region. It is suggested that the solar chromosphere and corona are heated by nonperiodic waves.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; 199; July 15
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  • 10
    Publication Date: 2019-06-27
    Description: Observations of quiescent solar prominences with the Harvard College Observatory spectrometer aboard Skylab show that prominence material is optically thick in the Lyman alpha line and the Lyman continuum. The color temperature of the Lyman continuum has a mean of 6600 K and an upward gradient toward the top of the prominence. The departure coefficient of the ground state of hydrogen is found to be of the order of unity, as expected from theory. The optical depth of the C III sheath region is determined directly from the observation of the limb through the prominence and is used to infer the mean electron density and the temperature gradient of the sheath. The result implies that the sheath density is about 0.4, and the temperature gradient about 1.4 times the respective value in the C III transition zone of the quiet sun. The C III triplet-singlet ratio for the prominence is found to give a density compatible, within the uncertainty of the atomic parameters, with the density obtained from the optical depth.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 39; Dec. 197
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