The FUSE Archival Data Handbook - MAST - STScI

4.2.1.4 Preview Files (*rat.gif, *ext.gif)
Two types of exposure-level diagnostic preview files are available, and both serve as useful tools
to verify the integrity of spectra derived from the exposure.
*rat.gif: These files display the count rate throughout the exposure (see Fig. 4.3). For TTAG
data, this is the actual count rate for events occurring within the region of the detector corresponding
to the target aperture (excluding airglow features) evaluated every second. For
HIST data, these are the dead time corrected counter data from the time engineering files
(housekeeping file, see Section 5.2), which are sampled once every 16 seconds (see Table 4.9).
For non-variable objects, these are useful diagnostics, since they enable the user to determine
whether the target remained within the aperture throughout the exposure.
Figure 4.3: Example of a count rate plot (*rat.gif) for detector segment 1A of exposure 001
for the TTAG observation C1600101. These plots show the count rates within the science
apertures. The various reasons for flagging bad data are shown below the figure. The dashed
curve is the count rate from the sections of the detector used for burst detection. In this case,
the plot shows that the observation was obtained during the day, and that several bursts were
detected and eliminated from the final spectrum. It also shows that the SiC1A count rate varied
significantly during the observation. Because the same plot for LiF1A is stable, we conclude
that the target was wandering in and out of the SiC1 aperture (see Chapter 7). As a result, the
flux level of the SiC1A spectrum will be less than other channels covering similar wavelengths
(see Fig. 4.7). CalFUSE cannot check for this effect since different segments are processed
independently and cannot be compared. However, users can use the FUSE tools to exclude these
regions (see Chapters 3 and 8).
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