synopsis: (1) statistical uncertainty in the responsivity from statistical uncertainty in the FCS signal (2) systematic uncertainty from a systematic uncertainty in the FCS signal (due to transients) (3) systematic uncertainty due to uncertainties in the aperture scaling (see section 3.17).
limitations and applicability:
(1) In case no valid FCS measurement is present, a default responsivity is
applied. (2) the geometric scaling of the FCS power with the geometric area
of the aperture introduces errors due to the non-homogeneous illumination
by the FCS.
description:
The responsivity for the filter in which the FCS measurement is taken,
is obtained from the FCS power on the detector (Pfcs)
normalized to 1 mm2 and the FCS signal sFCS (see 3.13).
where
is the weighted mean signal of the FCS
measurement (in V/s),
for a given FCS power and filter.
purpose correction:
Determination of the responsivity of the detector, which is necessary
to perform the flux calibration. The responsivity varies along a revolution
due to cosmic ray impacts and there is a strong dependence on space weather
environment.
uncertainty/noise introduced:
(1) The mean signal of an FCS measurement has a statistical uncertainty
which propagates into the uncertainty of the responsivity. This error
will contribute to the systematic uncertainty of the sky measurement(s).
(2) the photometric bias propagates in the responsivity determination.
(3) the geometric scaling to the aperture area adds no uncertainties in
case a standard aperture is used for the FCS measurement otherwise
uncertainties up to 100% are possible.
auxillary data: none
