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: http://xmm.vilspa.esa.es/calibration/documentation/CALHB/node252.html
Дата изменения: Tue Sep 20 19:45:19 2011 Дата индексирования: Mon Apr 11 02:51:12 2016 Кодировка: |
Many calibration quantities depend on basic instrument operation parameters such as the temperature of the focal plane. It is to be expected that items such as temperatures will be changed over the coarse of the mission, but this will only occur at certain infrequent points in time. Such a change of operation parameters influences the instrument calibrations in many areas, and in a complex way. The decision of change of operation parameters is triggered by a certain degradation of instrument performance. Given the complexity of a possible parameterization, together with the somewhat unpredictable degradation of performance, and the infrequent changes of parameter settings, does not justify to fully parameterize this dependence as part of the CCF and the CAL. Therefore these changes will be incorporated with updates of both CCF and CAL functions.
The consistency, however, of choice of operating parameters (available from telemetry) and validity of CCF files will be checked by the CAL functions that are accessing the relevant CCF constituent. In order to indicate the parameters that should be checked, they will also be listed in the following per CAL function as input parameters or state variables, but with the appended attribute (check).
As an example, the instrumental bad pixel table depends on operation temperature of the CCD's. The CCF BadPix contains only data for one temperature, which is given in a keyword in its header. The CAL functions CAL_getBadPixelList & CAL_getBadPixelMap use the CAL state variable temperature only to check that the current operating temperature is consistent with the CCF constituent BadPix. No interpolation is attempted either by CAL_getBadPixelList nor by CAL_getBadPixelMap. In case of inconsistent temperatures, the user will be informed to obtain an updated version of the CCF in question.
Since the measured temperatures (as obtained from the telemetry) will not necessarily have the same value as the nominal validity temperature which is given in the headers of the respective CCF constituents, a range is defined. Per temperature (the CCD temperature temperature, and the temperature of the electronics FPA_temp) an allowed range is specified in CCF MiscData. This will be used to check the actual temperature versus the one that is required for a certain CCF constituent.
The following possible dependencies of the instrument calibrations are currently neglected as they are at this point in time not considered to cause important effects: