FAST mode data is not binned by the DPU. The drifts from the ODF OM
Tracking History Auxiliary File need to be corrected for BPE only.
All events are assumed to occur in the centre of their pixel. The
output integer pixel coordinate value is the integer truncation of the real
coordinate value.
For FAST mode, in addition to a tracking frame time, a FAST mode time
slice (FMTS) is defined with duration SAMPTIME*10ms, where
SAMPTIME is integer (i.e. integer multiples of a CCD frame)
Each event is tagged with a time stamp (FTCOARSE+FTFINE) corresponding
to the specific FMTS integration within each tracking frame
integration, in which each event occurred. This allows the possibility
to apply a `fine shift' to each event corresponding to the spacecraft
drift, after each FMTS integration.
omfastshift produces by default a corrected event list in
which all events within a FMTS are shifted back to the reference frame
using drifts calculated from a linear interpolation of the tracking
frame drifts in the OM Tracking History auxiliary data file.
A corrected event list in which all events within a tracking frame are
shifted back to the reference frame using the tracking frame drifts
can be called for by the setting flag interp_flag = F on the command
line
It is worth noting that there exists cases in which a FMTS crosses a
tracking frame boundary. Although events may belong to two tracking
frames, all events within the FMTS are given the same event timestamp
and are treated equivalently.
The drift-corrected OM FAST mode event list contains 4 additional
columns: the corrected X and Y pixel coordinates and OBT time for each event
and a flag denoting whether the shift-corrected event falls within the
defined science window. This flag is necessary since the s/c drift causes
the science window to sample a region of the sky larger than the science
window. When these events are drift-corrected they may fall outside
the GO defined science window area. A value of WIN_FLAG=0 is given for all
events outside the science window, and WIN_FLAG=1 for all events in
the science window.