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Data: dumps
At NOEMA, the correlator outputs a spectrum every second. Storing the
spectra every second would result in an huge file. In practice one can
average the spectrum to the limit that it does not produce
unacceptable beam smearing. Depending on the desired field of view,
observing frequency and interferometer configuration, the acceptable
averaging time ranges from a few seconds to a few minutes. Two kind of
averages are stored in the data. First, every second, a spectral
average is produced for each spectral window, resulting in a data
point every second. These are refered to as the continuum dumps. Then,
for each integration time, two spectra are produced for each spectral
window: one is the average of all the spectra obtained within the
integration window, the second is the same, but the spectra are
corrected for an atmospheric phase before integration. The correction
is nowadays coming from the water vapor radiometers, but for some
time, a correction using the 1mm receiver total power was also
used. These constitutes the line data.
An observation is hence usually composed of
dumps, where
is
the integration time in seconds. The first
dumps contain only
continuuum data, the last two dumps contain both continuum and line
data, for the uncorrected and phase-corrected spectra respectively.
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Gildas manager
2023-06-01