Pick of The Week
 
 

What's Going On? (September 17, 2003)


Hi-res TIF image (4.3M)

Our SOHO team has received a number of questions about this image taken by the LASCO C3 coronagraph on 12 September 2003. What are all those swirling lines? Since the launch of SOHO in December, 1995, we've seen something similar about a dozen times. The images taken 24 minutes before and 30 minutes after this image show nothing unusual. As in each previous case, it appears that some of SOHO's multi-layer thermal insulation (MLI), which has become brittle after almost eight years' exposure to solar radiation, has flaked off and is passing in front of the wide-angle view of the coronagraph. The streaking in this 19-second-long exposure is similar to what you would capture if you were to hold a camera lens open for several seconds and take a picture of snow falling. Just as the snowflakes that passed closest to the lens would appear as fat, out of focus streaks, some of the MLI flakes also appear as thick, bright streaks.

Why did the MLI flake off? Most likely, a micrometeorite struck the insulation, not an uncommon event for spacecraft. This type of image has usually been observed when a cover of one of the instrument covers has closed with some force and knocked off some of the spacecraft's insulation, but no covers were closing on this occasion.

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Previous Picks of the Week

SOHO began its Weekly Pick some time after sending a weekly image or video clip to the American Museum of Natural History (Rose Center) in New York City. There, the SOHO Weekly Pick is displayed with some annotations on a large plasma display.

If your institution would also like to receive the same Weekly Pick from us for display (usually in Photoshop or QuickTime format), please send your inquiry to steele.hill@gsfc.nasa.gov.

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