On 7 Sept 2004, a bug was found and fixed that affected imaging in those
cases when the aspect roll solution was extrapolated backwards in time.
This is quite a rare occurrence, only one such case having positively
been identified, but nevertheless it can occur in circumstances when
there are gaps in the roll data or in the roll aspect database.  In some
but not all cases a message would appear in the IDL log window.
The easiest way to tell if this happened would be if the location of the
image peak appeared to depend on xyoffset (which it should not).
The effect of the bug was to displace the image for the all or part of
the requested time range by an offset of ( 2 * xyoffset ).  If the
extrapolation covered all of the time interval the image would be
displaced without affecting its morphology.  Otherwise the quality of
the image would be seriously degraded.