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Image name: APR_99_Filter_Failure.png (click image to enlarge)
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Date submitted: 12-Sep-2001
APRIL 1999 ENTRANCE FILTER FAILURE EVENT L. Acton, 12-Sep-2001 To the accuracy of the data it appears that the April 1999 entrance filter failure happened at sunrise, as has been the case for several other filure events. This would suggest that thermal stress plays a role in the failures. The top panel displays the total signal in narrow-band straylight monitor images with the 2-level intensity bifurcation normalized out. In the middle panel is the intensity in an exposure and resolution normalized strip across the bottom of AlMg images. The crosses are all exposures of DPE=19 and longer. The diamonds include DPE=11 exposures and are plotted with expanded time scale in the bottom panel. Yohkoh night is also displayed in the bottom panel Until further notice we will assume a failure time of 20-APR-99 19:02:00 and a failure fraction of 1/12 or 0.0833 for this failure event.