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SOLVE AMPLITUDE

CLIC\SOLVE AMPLITUDE [/PLOT] [/BREAK kind time [kind time ...]
[/POLYNOMIAL [degree]] [/WEIGHT] [/RESET]
This command fits a mathematical function into the measured amplitude of
the sources in the current index (presumably calibrators). This data
must have been selected and plotted in axes : SET X TIME and SET Y AM-
PLITUDE for the baselines and bands of interest, specified by the corre-
sponding SET commands. The calibration function is kept in memory. Com-
mand STORE AMPLITUDE should be used next to store this function in the
header of source observations, after a change in the index to select the
appropriate scans.
SOLVE AMPLITUDE internally and temporarily resets SET AMPLITUDE to
SCALED.
In antenna mode (selected by SET AMPLITUDE ANTENNA), the averaged phase
and amplitude closures are computed, as well as their standard devia-
tions. The phase closures should be close to zero, while the amplitude
closures should be close to 100%. Strong deviations of amplitude clo-
sures from 100% are an indication of amplitude loss on long baselines,
due to phase decorrelation during the time averaging. The fit then shows
strong systematic errors; if this occurs, baseline based calibration of
the amplitudes might be preferred.
Option /PLOT will plot the fitted curve over the data. Option /RESET
will reset the calibration curve in memory.
Fitted curves may be of two kinds:
- Cubic splines (the default). By default knots are regularly spaced
with an interval between knots set by the SET STEP command. Addi-
tional knots may be introduced with the option "/BREAK kind time
[kind time ...]" which introduces a break at abscissa 'time';
'kind' is an integer in the range 0-3; 0 means that a discontinuity
will be present, 1 that the first derivative will be discontinuous,
and so on. Several breaks may be introduced. The program will de-
tect an error if too many breaks are introduced, compared to the
density of data points.
- Polynomial curves may be used instead. For this the option is:
/POLYNOMIAL [degree] indicating the degree of the polynomial (de-
fault 0).
Normally the data points are all assigned the same weight for the fit.
With option /WEIGHT, the data points are weighted according to their er-
rors.

Gildas manager
2022-01-17