For measurements with FCS heating power outside the validity range, the default responsivity is used, see Section 7.10. The validity ranges are given in the header of the P*FCSPOW*.FITS CalG files, see Section 14.12. Sparse maps may have different FCS settings. The FCS with a setting inside the validity range is used in case the setting of the other falls outside. The selected responsivity calibration (single, both, first, second, default) is indicated in the SPD product file header. For P1 and P2 detectors there is no severe impact on calibration quality by using default responsivities.
Caveat: A poorer calibration accuracy can be expected for observations with detectors P3, C100 or C200 for which the headers of the PHT SPD data products indicate that the FCS power settings were outside the validity range and default responsivities were used. Due to the dependence of the FIR detector responsivities on space weather conditions calibration offsets by 30-50% are possible.
Caveat: The FCS calibration for P3, C100 and C200 before revolution 94 is less well sampled with standard calibration observations than after revolution 94. Therefore, the photometric calibration of observations taken before revolution 94 can be poorer than that of later observations. This caveat also applies to the FCS flat-field calibration for the C100 and C200 detectors.