converting IMAGE_TIME UTC to UT1 Options

[ncc1701d]

When images are taken the PDS header for a .IMG image file alway gives the "IMAGE_TIME" date in UTC time
like
2006-05-18T01:30:33.015Z which is zulu UTC

If i wanted to to get the matching UT1 that NASA might use for that particular "IMAGE_TIME" I would need to know how they handle leap seconds.

From my reading here
http://tf.nist.gov/pubs/bulletin/leapsecond.htm

It looks like there are two resolutions

It says
"The resolution of the DUT1 correction is 0.1 s, and represents an average value for an extended range of dates.
Therefore, it will not agree exactly with the weekly UT1-UTC(NIST) values shown in the earlier table, which have 1 ms resolution and are updated weekly"


So my question would be . What would NASA use to get the UT1 for that "IMAGE_TIME" if it was making a simulator or something? the 0.1 resolution or the weekly 1 ms resolution?
I might guess the higher resolution but maybe thats over kill or to inconvenient or may doesnt matter which resolution.