Atmospheric calibration

Atmospheric calibration works in basically the same way as in single-dish observing. Correlators are switched to auto-correlation mode. A tweak of the correlator is made. The receiver tables are used to make one auto-correlation measurement on source and one on the loads. The OBS $\backslash$CALIBRATE command starts this procedure. It accepts optional argument COLD to measure also the cold load, and hence derive receiver temperatures.

Data, including the continuum detectors output, are stored in the Date.IPB files. The CLIC $\backslash$SOLVE ATMOSPHERE command can be used in quasi-real time for data reduction.

The atmospheric transmission can be estimated using a single measurement by the OBS $\backslash$CALIBRATE command. This should be done rather frequently to monitor atmospheric variations. Depending on the calibration mode (HUMIDITY, TREC, AUTO, MANUAL), the observer should specify the receiver temperature (SET TREC), the water vapor content (SET WATER, or the atmospheric temperatures and opacities SET ATMOSPHERE and SET OPACITY). In the HUMIDITY mode, theoretical water vapor content is derived from the humidity, temperature and pressure measured by the meteo station.