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Toroidal Varied-Line Space (TVLS) GratingsIt is a particular challenge to develop a stigmatic spectrograph for XUV wavelengths since the very low normal-incidence reflectance of standard materials most often requires that the design be restricted to a single optical element which must simultaneously provide both re-imaging and spectral dispersion. This problem has been solved in the past by the use of toroidal gratings with uniform line-spaced rulings (TULS). A number of solar EUV (Extreme Ultraviolet) spectrometers have been based on such designs, including SOHO/CDS, Solar-B/EIS, and the sounding rockets SERTS and EUNIS. More recently, Kita, Harada, and collaborators have developed the theory of spherical gratings with varied line-space rulings (SVLS) operated at unity magnification, which have been flown on several astronomical satellite missions. We now combine these ideas into a spectrometer concept that puts varied-line space rulings onto toroidal gratings. Such TVLS designs are found to provide excellent imaging even at very large spectrograph magnifications and beam-speeds, permitting extremely high-quality performance in remarkably compact instrument packages. Optical characteristics of two solar spectrometers based on this concept are described: SUMI, proposed as a sounding rocket experiment, and NEXUS, proposed for the Solar Dynamics Observatory mission.
Document ID
20020071039
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Thomas, Roger J.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Oegerle, William
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Astronomy
Meeting Information
Meeting: Astronomical Telescopes and Instrumentation
Location: Waikoloa, HI
Country: United States
Start Date: August 22, 2002
End Date: August 28, 2002
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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