The scans in the current index are grouped in intervals of maximum duration `delta_time' (in seconds); source changes will also be used to separate intervals. In each interval a straight line is fitted in the variation of atmospheric emission as a function of time; this line will be the reference value for the atmospheric correction.
The default for `delta_time' is 3600 s, which usually results in using the on-source time between two phase calibrator observations as intervals for evaluation of .
One may also try and extend `delta_time' and use this command to process the source observations and the phase calibrator observations separately (but beware that using very long times will produce long term phase drifts into the phase correction, which will have to be removed by the usual phase calibrations anyway).
After using this command, one may plot using SET Y ATM_REF and SET X TIME, in antenna mode; itself is available with SET Y ATM_EM.
After a plot, one may check the coefficients used by typing SHOW CORR. The coefficients are given in radians per unit of .