# Polarimetry

The presence of polarimetric measurements in the IMBFITS file is described in the POLAR column of the BACKEND table. For a non-polarimetric scan, all the chunks in the POLAR column have the NONE value. For a polarimetric scan, values can be NONE, AXIS, REAL or IMAG (note that non-polarimetric chunks -NONE- can be mixed with polarimetric ones).

In addition, calibration scans for polarimetric measurements must provide a calGrid subscan. It absent, MRTCAL will mark this scan failed as it can not be used to calibrate polarimetric science scans.