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AFTA Coronagraph Working Group Recommendation to Astrophysics Division
No abstract available
HabEx Telescope WFE Stability Specification Derived from Coronagraph Starlight Leakage
No abstract available
Extreme wave front sensing accuracy for the Eclipse Coronagraphic Space Telescope
Through both simulation and hardware experiments, we examine and establish the key data requirements, such as the defocus levels and imagin signal-to noise level, that are necessary to obtain the desired wave front sensing accuracy and bandwidth.
Exploratory Analytic Cases and Coronagraph Exploratory Cases
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UCSC CAL2 Phase 1 Deliverables: Designing Software and Coronagraph Hardware for the CAL2.0 Upgrade [Slides]
Abstract not provided.
A Simplified Theory of External Occulters for Solar Coronagraphs
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The Coronal Mass Ejection Visibility Function of Modern Coronagraphs
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Support-studies for the coronagraph contamination experiment, 1 September 1968 - 31 August 1969
Calculation of Mie scattering functions
Coronagraph observations of the coronal condensation of 4 February 1962
Coronal condensation spectra during 4 February 1962 total eclipse, determining abundances, ionization equilibria, electron densities, etc, from Fe and Ca XV lines analysis
Supporting studies for the coronagraph contamination experiment
Calculations of Mie scattering functions involved individual as well as mixed scattering of particles. In particular, computations were completed for a 15A particle and for particles subjected to incident light of ultraviolet wavelengths. Calculations of contaminant atmospheres for Gemini, Apollo, and Skylab considered leakage rates for the respective vehicles and the mass column density of the atmospheres surrounding them. Atmospheres for these vehicles have been computed for a uniform particle size distribution, and for a particle size distribution in which size varied.
Coronagraphic observations of an enhanced coronal region. I - Fe XIII and Ni XV emission line data.
Observation of nine coronal emission lines representing five stages of Fe ionization and one stage of Ni in an enhanced coronal region. The data from these observations are presented along with a density model of the enhanced region obtained from the Fe XIII and Ni XV emission line ratios as a function of position angle. The electron densities obtained from Fe XIII lines range from 10 to the 8th to 10 to the 9th per cu cm, and are slightly lower for Ni XV line data. Estimates of the variation of temperature over the enhanced region are inferred from the observed line intensities.
Coronagraphic observations of an enhanced coronal region. II - Temperature and density structure through the enhanced region.
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Use of the moon to distinguish the F from the K corona using a rocket coronagraph during an eclipse
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Radiance calibration of the High Altitude Observatory white-light coronagraph on Skylab
The processing of over 35,000 photographs of the solar corona obtained by the white-light coronograph on Skylab is described. Calibration of the vast amount of data was complicated by temporal effects of radiation fog and latent image loss. These effects were compensated by imaging a calibration step wedge on each data frame. Absolute calibration of the wedge was accomplished through comparison with a set of previously calibrated glass opal filters. Analysis employed average characteristic curves derived from measurements of step wedges from many frames within a given camera half-load. The net absolute accuracy of a given radiance measurement is estimated to be 20%.
The 1980 rocket coronagraph measurements of the solar wind acceleration region
Spectroscopic measurements of temperatures, densities and flow velocities in the solar wind acceleration region provide critical empirical constraints on solar stellar wind theory. Preliminary results of an analysis of H I Lyman-alpha and white light measurements made on 16 February 1980 in a polar coronal region are reported. The hydrogen kinetic temperatures in the observed region were found to be nearly constant with T sub HI approximately equals 10 degrees K at heliocentric distances between 1.5 and 4 solar radii. The outflow velocities were found to be subsonic indicating that the critical point in the observed region was located at r approximately greater than 4 solar radii.
Coronagraphic observations of two new sungrazing comets
The discovery has recently been reported of a comet (Howard-Koomen-Michels: 1979 XI) that apparently collided with the sun on 30 August 1979. A report is presented of observations of two additional sungrazers that encountered the sun on 27 January 1981 and 20 July 1981, respectively. Like comet 1979 XI, these two new comets seem to have been members of the Kreutz group of sungrazers, and like 1979 XI the new comets did not reappear after their encounters with the sun. The discovery of three previously unreported comets during the initial 2.3 yr of satellite coronal observations suggests that sungrazers are much more common than one might suppose from the list of only nine known sungrazers observed during the years 1668-1970.
White Light Coronagraph (WLC) and Ultra-Violet Coronal Spectrometer (UVCS)
The WLC and UVS together reveal the corona and the roots of the solar wind from 1.5 to 6 solar radii from sun center. The WLC measures the plasma density and spatial structure of the corona and coronal mass ejections at a plasma density and spatial structure of the corona and coronal mass ejections at a resolution of about 20 arcsec. The UVCS in combination with the WLC measures the temperature and radial outflow speed of the coronal plasma. These instruments will detect mass ejections from active regions and high speed solar wind streams from coronal holes a few days before the source regions rotate onto the face of the Sun, thus giving a week or more of advanced warning for disturbed geomagnetic conditions at Earth.