25 November 1996 LASCO spectrometric Lyot coronagraph tunable passband filter
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Abstract
Spectrometric and spectropolarimetric aspects of the Lyot coronagraph flown aboard the ESA/NASA SOlar Heliospheric Observatory (SOHO) are presented. The coronagraph is one of the three channels comprising the LASCO coronagraph and the only channel with spectroradiometric capabilities. Among the primary science objectives assigned to the Lyot coronagraph are the determination of the mechanisms responsible for the acceleration of the solar wind and the heating of the corona. Spectrometric and spectropolarimetric coronal observations made with the Lyot coronagraph are used in support of these and other objectives. We describe the Lyot instrument design from the imaging coronal spectrometer perspective. The rationale for use of a tunable Fabry-Perot interferometer as the spectral resolving element is outlined. The relationships between spectral resolving power, interferometer diameter, telescope entrance stop diameter and coronal field of view as it applies to LASCO is reviewed. Performance requirements imposed on the interferometer by the coronal source and the science objectives are described. The optical, mechanical, electronic and semi-automated control designs as well as the interferometer modes of operation are summarized. The actual flight model Fabry-Perot interferometer performance allows the instrument to operate with high luminosity and with finesse values high enough to provide approximately optimal passband widths and reasonable tunable ranges about useful spectral features. We conclude with some early results indicative of the flight performance of the instrument.
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Dennis George Socker, Guenter E. Brueckner, Clarence M. Korendyke, D. N. Lilley, James Henry Steenson, Preston Mitchell Kohn, Gail Marie Lyons, Michael Lawrence Owens, Norman E. Moulton, Robert W. Moye, Rainer Schwenn, P. Hemmerich, "LASCO spectrometric Lyot coronagraph tunable passband filter", Proc. SPIE 2804, Missions to the Sun, (25 November 1996); doi: 10.1117/12.259711; https://doi.org/10.1117/12.259711
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