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

Chapter 20
Advanced data calibration
In this chapter of the CIA User’s Manual different calibration methods and algorithms are briefly
reviewed and their implementation in CIA is described. Detailed information on calibration
algorithms can be found in the technical reports listed in Appendix K. Probably the most
helpful report for a novice is the ISOCAM Handbook. This report contains a broad treatment
of calibration algorithms – it, and the technical reports, will be referenced throughout the
chapter where appropriate. Since more up-to-date algorithms and routines are continually being
developed it is also a good idea to refer to the on-line help or cia help (see Section 2.3.2).
20.1 Before reading this chapter. . .
Throughout this chapter references are made to the Prepared Data Structure (PDS) (Section
15.5) and the CIA calibration routines (Chapter 13). Familiarity with both topics is assumed.
You will also frequently encounter references such as .IMAGE, .CUBE, .MASK, etc. . . .
These are general references to fields and substructures in the PDS.
20.2 Core calibration
You have already been introduced to the core calibration routines in Section 13.2.1. Here we
will look a little deeper into the different correction methods that are available for each of the
core calibration routines. The chosen correction method can be specified with the keyword
method. Each method is implemented by a low-level routine which may accept keywords for
tuning algorithm parameters. These keywords may be specified when calling the core calibration
routine and IDL will pass the keywords to the low-level routine (i.e. using IDL’s keyword
inheritance functionality). To find out what tuning can be done for a particular method, look
for the relevant low-level routine in the online help (Section 2.3.2).
20.2.1 Dark correction
In principle, dark correction is a simple procedure – a matter of subtracting the DARK image
from the IMAGE. The hard part is choosing a good DARK. All dark correction methods are
handled by corr dark. Technical details of some of these methods can be found in the references
given below.
In general, corr dark performs the dark correction in the following manner:
1. Obtains the DARK as instructed by the user setting of the keyword method or indark.
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