New XRT/WFC mixed attitudes with WFC errors
============================================
Starting with SASS7_7 there are several ROSAT days on which the XRT attitude
solution has been replaced by a mixed WFC/XRT attitude solution that also
displays the WFC errors. Replacement by WFC values has been done for such times
only where the XRT solution definitively is bad or is missing. 

The WFC errors show a relatively broad distribution reaching from about 3'' to
45''. From the XRT attitude solution we know that the scale of the (XRT) error
has nearly no meaning. This is the reason why SASS in this case adopted 1
arcsec as a quality selection criterion since two stars in the star tracker
camera brought the attitude error below 1 arcsec and less than 2 stars resulted
in errors above 1 arcsec. For the WFC attitude as well no well established
interpretation of the error value does exist. Thus it seemed to be appropriate
to adopt the same criterion as for the XRT data. Hence only such WFC attitude
data points have been accepted for replacement where at least two stars are
found in the star camera (except for a few singular seconds which are estimated
to be unimportant). SASS will not make any further screening on the WFC data. It
is left to the user to make a further screening if he/she will find it
appropriate. 

On the following 33 ROSAT days a mixed WFC/XRT attitude solution will be used
beginning with release SASS7_7: 

		0021
		0024
		0046
		0047
		0059
		0276
		0280
		0291
		0292
		0298
		0300
		0301
		0321
		0340
		0343
		0345
		0362
		0363
		0365
		0369
		0370
		0373
		0382
		0383
		0392
		0404
		0411
		0412
		0414
		0418
		0426
		0428
		0432

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