As mentioned in section 3.2.2, radiation damage may cause the response of the SIS to vary over the face of the CCD on a time-scale of a year, and so the response will be a complicated multi-dimensional entity. Possible short-term activation as a result of passing through the SAA will also require consideration. The same is true for the GIS, although to a lesser degree. It is also anticipated that our knowledge of the response will improve as the mission progresses, requiring the systematic implementation of calibration updates. For these reasons, and to make Astro-Danalysis as smooth as possible, the analysis software will cause the response, appropriate to the FSF under analysis, to be generated automatically from calibration data. In particular, response generation will be executed by a program written in ANSII-standard C or FORTRAN and capable of incorporation into IRAF/PROS (just like SAOIMAGE), XANADU and IDL. To ensure that this CPU-intensive process is not executed more often than necessary, response generation will occur once a region for spectral integration has been selected.
The same basic idea of automatic generation will be applied to the creation of exposure and background maps. An exposure map will be generated once a sample of data has been selected for analysis, but before spatial subsamples (i.e., regions within the full field of view) have been selected for spectral and timing analysis or for further image analysis. The same will occur for background maps which will be generated at the same time as the exposure maps. However, in subsequent analysis, it will be possible to select sections of the exposure and background maps as appropriate.