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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 $ n+2$ dumps, where $ n$ is the integration time in seconds. The first $ n$ 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 2022-01-17