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Attempt to Minimize Pointing Scatter

Image name: SXT_Pointing_Scatter.png (click image to enlarge)
Image size: 12.0880 KB (640x512)
Date submitted: 19-Sep-1998

This images illustrates the Y pointing of some 90,000 SFD images.  The SXL data
base was used to gather the index records.  Yohkoh repointings are indicated by
the vertical lines.  Probably some repointings are missed.

Since 1997 a serious attempt has been made to narrow the scatter of pointings in
order to improve straylight correction.  As can be seen from this figure the
effort has been only partially successful.  Also, the desire to spread around
limb radiation damage on the CCD competes with the desire to keep all pointings
tightly clustered.

The pointing drift pattern is quite predictable and repeatable.  Thus, I suggest
that the SXT CO write down a plan for managing pointing rather than use the
seat of the pants approach followed so far.  One could even write down a
chron job to prepare Yohkoh pointing updates on a regular and planned basis.

						Loren Acton  19-Sep-98

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