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3.9 Discarding signals in chopped measurement

synopsis:  (1) statistical uncertainty increase due to decrease in effective integration time, (2) systematic uncertainty decrease due to removal of highly unstable signals.

limitations and applicability:
The correction is only applied to chopped observations, PHT32 is also excluded. The signal redundancy per chopper plateau is minimized, often to 2 signals per chopper plateau or less.

description:
For chopped measurements in general, the plateaux show upward transients for the on-source signals and downward transients for the off-source signals. To minimize influences by the initial jump, the first half of all signals on a chopper plateau is discarded.

purpose correction:
Better definition plateau signal. The same method is used in the derivation of the correction factors for signal losses in chopped mode.

uncertainty/noise introduced:
The effective integration time is decreased by 50%, thereby increasing the statistical uncertainty by $\sqrt{2}$.

auxillary data:
Deglitch parameters.



ISOPHOT Error Budgets: Derive_SPD Processing Steps, Version 1.0, SAI/98-091/Dc