HR: 0800h
AN: SH41B-1121    [Abstracts]
TI: Elliptical Varied Line-Space (EVLS) Gratings for Imaging EUV Spectroscopy
AU: * Thomas, R
EM: Roger.J.Thomas@nasa.gov
AF: NASA's Goddard Space Flight Center, Code 612.1, Greenbelt, MD 20771 United States
AB: Imaging spectroscopy at wavelengths below 2000 Å offers an especially powerful method for studying many extended high-temperature astronomical objects, like the Sun and its outer layers. But the technology to make such measurements is also especially challenging, because of the poor reflectance of all standard materials at these wavelengths, and because the observations must be made from above the absorbing effects of the Earth's atmosphere. To solve these problems, single-reflection stigmatic spectrographs for XUV wavelengths have been flown on several space missions based on designs with toroidal uniform line-space (TULS) or spherical varied line-space (SVLS) gratings that operate at near normal-incidence. More recently, two solar EUV/UV instruments have been selected that use toroidal varied line-space (TVLS) gratings: the SUMI and RAISE sounding rocket payloads. The next logical extension to these concepts is to consider gratings with elliptical surfaces and varied line-space (EVLS) rulings. In fact, EVLS designs are found to provide superior imaging even at very large spectrograph magnifications and beam-speeds, permitting extremely high-quality performance in remarkably compact instrument packages. Such designs may be optimized even further by using a hyperbolic surface for the feeding telescope. Optical characteristics of two EUV spectrometers based on these concepts are described: EUS and EUI, both being developed as possible instruments for ESA's Solar Orbiter mission by consortia led by RAL and by MSSL, respectively.
DE: 7594 Instruments and techniques
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005