In this situation, the telescope is controlled in roll by gyros, which may allow a slow drift around the axis defined by the direction toward the single guide star. As a member of the ST ScI's OPUS team, I examined the data and provided the following assessment.
Preliminary analysis indicates that the guide star was binary.
As a result there may be some motion around a point centered on the dominant guide star position. These observations were implemented as observation set 26 in Science Mission Specification 972097C2. The exposure logsheet lines that defined them are listed in the following table. The intention of this report is to notify you about shortcomings with the execution of your observations. It is ST ScI policy not to repeat parallel observations.