Summary

accor determines the amplitude calibration from auto-correlations. 

The accor task determines the amplitude corrections from the apparent normalization of the mean autocorrelation spectra. Mis-normalization of the autocorrelations (and thus also the cross-correlations) is caused by errors in sampler thresholds during an observation. This correction is typically required for data correlated with the DiFX correlator (such as VLBA data). Other correlators (such as the SFXC correlator, which is used to correlate EVN data at JIVE) may already apply this correction at the correlator. In these cases, running this task is not necessary (but shouldn't hurt).

The accor task should be run with a solution interval (solint) adequate to track variations in effective sampler level optimization (including resets), typically on timescales of seconds to minutes.

See Solving for Calibration for more information on the task parameters accor shares with all calibration solving tasks, including data selection, general solving properties, and arranging prior calibration (i.e., specifying other caltables to pre-apply before solving). In most cases, no prior calibration is required, since the raw mis-normalization of the autocorrelations is essentially the calibration sought from accor.