Sunelevation: the higher the sun in the sky, the higher the UV radiation level.
太阳高度：太阳在空中越高，紫外线辐射水平就越高。
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At any point, if the sunelevation or sun azimuth errors or the momentum vector error exceeds tolerances, the ACS will return to an appropriate mode in order to correct the problem.
The red stripe is caused by a the interplay of light and cloud in the Canadian Rockies. The light-reflecting nature of the clouds coupled with low sunelevation resulted in this startling effect.