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

252 CHAPTER 20. ADVANCED DATA CALIBRATION
Figure 20.4: flat builder’s main window.
20.10 Making custom FLATs with flat builder
flat builder allows you to build a FLAT from EXPOSUREs in a raster observation. EXPO-
SURES can be interactively selected and a FLAT created from a median or mean. The FLAT
can be tested and tailored to produce optimum results. An additional feature is that regions of
a selected EXPOSURE can be excluded from the FLAT computation, so the danger of including
source signal in the FLAT can be avoided.
20.10.1 Building a simple flat
Suppose we have a raster PDS. flat builder accepts the cube of EXPOSUREs in the PDS field
.IMAGE as an argument. Optionally the CAL-G FLAT (already in .CALG.FLAT) can also be
supplied. This will allow you to compare your custom FLAT with the CAL-G FLAT during a
flat builder session. flat builder can be called directly or via corr flat (Section 20.2.5). If
the later is chosen then upon exiting of flat builder the custom FLAT will be automatically
applied to the data. If the former is chosen then the custom FLAT must be used as input to
corr flat.
To call flat builder directly:
CIA> built_flat=flat_builder(raster_pds.image, calg=raster_pds.calg.flat)
Looking at Figure 20.4 you can see the main flat builder window. An additional window
(not in the figure) displays all the EXPOSUREs for reference – we will call this the reference
window. The following steps should guide you through using flat builder: