... HST . WF/PC-1 Data Handbook . ... Data . ... Journal Clubs and Research Groups . ... If strfits was used to convert the HST Archive's FITS files (as described in Chapter 3), the image data will be in GEIS format. ... GEIS files use group format to keep all of the data from a given HST exposure together in a single image file. ... The header file for an image contains the information that applies to the observation as a whole (i.e., to all the groups in the image), viewable by paging the header. ...