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

21.5. A WORKED EXAMPLE 277
Therefore, to perform the SLICE processing we now have to first set the reduction parameters
structure with:
CIA> red param = set red param(tdt=tdt,flat smooth window=6,nplanes=30,$
CIA> flat thresh=10)
Two things are worth mentioning here. First it is mandatory that the result of the set red param
function go into the variable red param as this is how SLICE will access the parameters. If
you use another name, the SLICE structure will not be updated correctly. Second, you can see
that the name flat-field method appears nowhere on the command lines. This is because the
method is entirely determined by the set of parameters used. Thus make sure you have read the
manual and understand the signification of the parameters before you start any processing.
Now that the parameters are set, you need to specify the action to perform, for flat-fielding,
this is called make map so, in a similar fashion, you will update the action structure:
CIA> act = set act(/make map)
Here again, it is absolutely mandatory to store the result of the set act go into the variable
called act.
So far, we have only updated the structures that describe the actions to perform, to actually
start the processing, type:
CIA> slice pipe
At the end of this processing, the resulting map can be found in the field map and is displayed
by SLICE’s visualizing tool. If you wish to recover the flat-cube used in the flat fielding, start
the slice pipeline with:
CIA> slice pipe,flat out=flat out
21.4.2 Error computations
Even though this is an important aspect of the data reduction, up to April 2000, SLICE in
its default setup did not compute the error map associated to the sky map. This operation is
performed at the make map stage. You can easily check what is your setting by doing:
CIA> help,error map
If the result is UNDEFINED then you need to read the following lines, otherwise the error map
is computed by default at the flat-field correction stage.
If the error map is not computed by default, simply add the keyword /error map to the call
to set red param and proceed as before. The error map should now be available in the variable
error map 2 . Therefore, the example above becomes:
CIA> red param = set red param(tdt=tdt,flat smooth window=6,nplanes=30,$
CIA> flat thresh=10,/error map)
CIA> act = set act(/make map)
CIA> slice pipe
21.5 A worked example
This section is intended to lead you through a classical use of SLICE on a raster observation.
We once again recommend that you read M. A. Miville-Deschênes’ paper before using SLICE.
2 Remember to add the keyword at all your flat-fielding calls, otherwise set red param will reset it at 0.