It's a planned roll maneuver of the spacecraft itself. They do this once in a while for maintenance purposes (I don't know the specific reason).
I found this press release about a roll maneuver on October 26 that also mentions another roll maneuver for Nov. 7 (the date of the OP's images):
SOHO will perform a special 360-degree science roll maneuver on 26-Oct-09 between 13:50 and 23:50 UT. The roll comprises 10 segments (10
degrees, 8 x 45 degrees, -10 degrees), after which SOHO will be back in its nominal roll attitude. During the manuever, images and movies will also
appear rotated. The next quarterly 180-degree roll maneuver is scheduled for 7-Nov-09.
Source (scroll down to bottom of page)
It seems from the information above that they do a planned quarterly (4 times per year) 180 degree roll of the spacecraft, but the October 360 degree
roll event was special.
I couldn't find specific information on the 180 degree rolls -- hopefully someone on ATS knows why this roll is required.
I realize the orientation on the "after roll" image is the same as the "before roll" image (i.e., it's not upside-down), but perhaps the
SOHO people rotate the images themselves to a common orientation (with the top being Solar North) before releasing them to the public.
[edit on 11/9/2009 by Soylent Green Is People]
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