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In CLASS, the SET WEIGHT command offers 3 weighting modes (see
IRAM memo 2009-4):
- EQUAL: the weights are set to
,
- TIME: the weights are set to
, where
is the integration time
in seconds,
the frequency resolution in megaHertz, and
the system temperature in Kelvin.
- SIGMA: the weights are set to
, where
is the rms noise in
Kelvin.
is usually pre-computed by the BASELINE on
channel ranges with no signal. The
is introduced to match
the
unit of the TIME weight.
These are relative weights between spectra to be combined in commands
like AVERAGE, XY_MAP, etc. Absolute weights involve an
additional constant factor which is not described here. The weighting
modes can not be mixed: when combining spectra, all weights are EQUAL, or all weights are TIME, or all weights are SIGMA. Note that the TIME weight is a theoretical value based
on parameter values taken at observation time, while the SIGMA
is a measured value based on the actual noise property of the
spectrum.
Next: Switching modes
Up: class-weighting
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Gildas manager
2023-06-01