Far-ultraviolet and visible light scatter measurements for CVD SiC mirrors for SOHO
Far-ultraviolet and visible light scatter measurements for CVD SiC mirrors for SOHO
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SOHO CVD SiC 反射镜的远紫外和可见光散射测量
DOI：
10.1117/12.333616
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
L. Gardner
中科院分区：
文献类型：
--
作者：
D. Leviton;T. Saha;L. Gardner
化学气相沉积(CVD)碳化硅(SIC)由于具有良好的宽带反射率和良好的热、光性能，已成为真空紫外光波段的星载太阳仪器的常用反射镜材料。在这个波长范围内工作的反射镜表面的散射会破坏原本良好的图像对比度，特别是对太阳这样的扩展目标。虽然有效的远紫外线(FUV)散射测量完全不容易进行，因此很少进行，但可见光散射测量相对容易。不幸的是，基于CVD碳化硅制成的反射镜的可见光散射测量来预测FUV散射性能并不简单。希望通过对同一个CVD碳化硅反射镜在两个波长范围内进行散射测量，可以增强做出这种预测的能力。在戈达德空间飞行中心(GSFC)，为太阳和日球层天文台(SOHO)上的两台仪器--紫外线日冕光谱仪(UVCS)和太阳辐射紫外线测量仪器(SUMER)--使用两种不同的方法进行了可见光(633 Nm)散射测量。此外，还对Sumer望远镜反射镜进行了广泛的FUV散射测量。在本文中，我们关联了这种重要材料的FUV和可见光散射测量的结果。
Chemically-vapor-deposited (CVD) silicon carbide (SiC) has become a popular mirror material for spaceborne solar instrumentation for the vacuum ultraviolet wavelength range due to its appreciable broadband reflectance and favorable thermal and opto-mechanical properties. Scatter from surfaces of mirrors operating in this wavelength range can destroy otherwise good image contrast especially for extended targets such as the sun. While valid far ultraviolet (FUV) scatter measurements are entirely non-trivial to conduct and so are rarely performed, visible light scatter measurements are comparatively easy. Unfortunately, it is not straightforward to predict FUV scatter performance based on visible light scatter measurements for mirrors made of CVD SiC. It is hoped that by carrying out scatter measurements in both wavelength regimes for the same CVD SiC mirror, that the ability to make such predictions may be enhanced. Visible light (633 nm) scatter measurements were performed at Goddard Space Flight Center (GSFC) by two different means on CVD SiC telescope mirrors (from the same process and same vendor) for two instruments on the Solar and Heliospheric Observatory (SOHO) - - the Ultraviolet Coronagraph Spectrometer (UVCS) and Solar Ultraviolet Measurement of Emitted Radiation (SUMER). Additionally, extensive FUV scatter measurements were made for SUMER telescope mirrors. In this paper, we correlate the results for those FUV and visible light scatter measurements for this important material.