Keywords: mrtcal-user-manual

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## Weight array

MRTCAL offers the possibility to associate a weight array (Associated Array W) together with the spectrum intensities (`RY`). This weight varies in frequency. The weight at channel is:

| (1)

where , and are respectively the integration time (seconds), the frequency resolution (MHz) and the airmass (same scalar values shared by all channels), and is the opacity at channel . is the zenithal system temperature, which can be found in the calibration products from a calibration scan (see subsection ).

By default, MRTCAL does not save the weight array. This is activated by the command:

    MRTCAL> MSET OUTPUT WEIGHT YES

Beware that if enabled, this writes twice more data per spectrum, which typically doubles the CLASS file size! An example of a weight array is plotted in the Figure , produced with the following commands:

    LAS> file in 09054
    I-CONVERT,  File is  [Native]
    I-INPUT,  09054.30m successfully opened
    LAS> find /source controld
    I-FIND,  12 observations found
    LAS> get first
    I-GET,  Observation 3; Vers 1 Scan 201
    LAS> plot w

Figure: Weight array associated to a spectrum produced from the file iram30m-4mhz-20100930s200-imb.fits.

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