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3.16 Default detector responsivity

synopsis:  systematic flux uncertainty due to flux dependence of the detector responsivity level from revolution to revolution.

limitations and applicability:
The P3, C100 and C200 detectors are more sensitive to space weather conditions and to the ionizing radiation at the end of a revolution. Per orbital phase element, the default responsivity is an average value for the complete accessible flux range (from background level to saturation). Any dependence on the total illuminated flux is not accounted for. This can cause discrepancies as high as a factor 3 as found from chopped photometry analysis.

description:
In case the FCS measurement is inadequate to determine the detector responsivity, the default responsivity is used. The default responsivity is a function of position along the orbit and was determined by averaging many responsivity measurements along a revolution.

purpose correction:
Determination of the detector responsivity during an observation.

uncertainty/noise introduced:
For the default responsivity it is assumed that the responsivity does not vary from revolution to revolution. This assumption is for the SS, SL, P1, and P2 detectors probably good within a few percent. The other detectors P3, C100, and C200 are more sensitive to space weather conditions. As a result, the default responsivities for a given observing date can be as uncertain as several tens of percent.

auxillary data: Cal-G files PPRESP, PC1RESP, PC2RESP
uncertainties are supplied in the Cal G file.


next up previous contents
Next: 3.17 Aperture scaling of Up: 3. Derive SPD level Previous: 3.15 Detector responsivity PHT-C
ISOPHOT Error Budgets: Derive_SPD Processing Steps, Version 1.0, SAI/98-091/Dc