... if attsource =`odf' and timesource =`eventlist'), a file (usually expected to be the output file of atthkgen ) which contains in the primary HDU keywords as follows: . if odfattsource =`ahf': . ... if attsource =`atthk'), a file (usually expected to be the output file of atthkgen ) which contains in the primary HDU keywords as described in the previous item, plus an extension ATTHK , which contains the following columns: . ... if atthkattsource =`ahf') AHFRA , AHFDEC and AHFPA . ...