Simple Calibration

It is possible that there is a phase offset between polarisation which will effect the phase of the cross polarisation correlation, and so give rise to spurious polarisation. rotate_xyphase can be used to correct for this error. At this point, the user must know how to determine the size of the phase offset themselves.

  ASAP>scans.rotate_xyphase(10.5)            # Degrees

Note that if this function is run twice, the sum of the two values is applied because it is done in-situ.

A correction for the receiver parallactic angle may need to be made, generally because of how it is mounted. Use rotate_linpolphase to correct the position angle. Running this function twice results in the sum of the corrections being applied because it is applied in-situ.

  ASAP>scans.rotate_linpolphase(-45) # Degrees; correct for receiver mounting

If the sign of the complex correlation is wrong (this can happen depending on the correlator configuration), use invert_phase to change take the complex conjugate of the complex correlation term. This is always performed in-situ.

  ASAP>scans.invert_phase()

Depending on how the correlator is configured, ``BA'' may be correlated instead of ``AB''. Use swap_linears to correct for this problem:

  ASAP>scans.swap_linears()