ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

286 CHAPTER 21. USING SLICE WITHIN CIA
Figure 21.5: The long-term transient corrections derived by SLICE. The continuous curves
are the exact corrections and the dashed ones the fitted corrections, assuming the long-term
transient effect is a combination of two exponentials. On the left, the LW3 case, and on the
right, the LW2 case. Some oscillation appear on the LW2 exact curve, but these are not obviously
related to the raster scan period.
sky with another method. Therefore, we apply here two make map actions, the first one with
the Perturbed Single Flat-Field method, using the parameter values in Table 21.3 and the
second with the DivSky method, using the parameter values listed in Table 21.4. The results
after the long-term transient correction and the new flat-field are displayed in Figure 21.6. A
comparison with Fig. 21.1 shows the improvement in the image quality. Further improvement
can be achieved by looking at deviant pixels, glitch impacts and so on. This is explained in the
next section.
21.6 Bad pixels, ghosts and sources
Even though we have removed much of the problems that affect the data, some may still remain.
For instance, ghosts following observations of bright sources are not corrected by either the ltt
or make map action. Pixels that have been hit by strong glitches may still show up in the map
as holes or fake sources. This section thus describes the tool that SLICE offers to correct these
artifact. For those that may already be familiar with SLICE the current version (April 2000)
has introduced a dramatic change by merging the ghost, bad pixels and source actions into
one, the bad pixels action.
A note of warning though: if your observation contains bright small-scale structure, it may
be affected by the bad pixels action. It is important that you compare in detail the result of
the action to the previous state of the map (in map before) to make sure you understand what
has been done.
An important point to mention before we begin: the action described here affect neither the
data cube (variable c) nor the cube of raster pointings contained in raster. It will create new
versions of the sky map (in map), the error map (error map) and the redundancy map (redun).
Also note that, as for the make map action, you have the possibility to work on the full cube, or
simply on the cube of raster pointings (here I recommend working on the full cube, by placing
the /docube keyword on the call to slice pipe).