Grating stray-light analysis and control in the UVCS/SOHO

被引：23

作者：

Fineschi, S ^{[1
]}

Gardner, LD ^{[1
]}

Kohl, JL ^{[1
]}

Romoli, M ^{[1
]}

Noci, G ^{[1
]}

机构：

[1] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

来源：

X-RAY AND ULTRAVIOLET SPECTROSCOPY AND POLARIMETRY II | 1998年 / 3443卷

关键词：

UV space optics; UV spectroscopy; stray-light;

D O I：

10.1117/12.333614

中图分类号：

O43 [光学];

学科分类号：

070207 ; 0803 ;

摘要：

The Ultraviolet Coronagraph Spectrometer (UVCS) of the Solar and Heliospheric (SOHO) mission has been developed for spectroscopic and polarimetric determinations of temperatures, densities and flow velocities in the extended solar corona. The instrument consists of a visible light (VL) polarimeter, and two ultraviolet (UV) spectrometers, optimized for the H I Lyman alpha (Ly-alpha) line (lambda 1216 Angstrom) and for the O VI doublet (lambda 1032/1037 Angstrom). The stray-light profile of the Ly-alpha holographic grating has been measured, in a laboratory set-up, in both the spatial and spectral directions. The observed profile has been found Go be a combination of two components: the scattering from the grating surface, and the Fraunhofer diffraction due to the vignetting of the grating. An analytical expression for the scattering component of the grating point spread function (PSF) has been derived from a simple model of the grating surface roughness. The stray-light profile generated by the analytical expression of the grating PSF gives a good fit of stray-light profile measured in the laboratory This instrument function has been be used in the analysis of in-flight UVCS observations of the profile of electron scattered Ly-alpha from the solar corona. These observations have resulted, for the first time, in the most direct measurement of the coronal electron temperature.

引用

页码：67 / 74

页数：8

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