Polarization calibration of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO)

This paper describes the polarimetric design of the instrument, the test setup, the polarimetric model, the tests performed, and some results. It is demonstrated that HMI achieves an accuracy of 1% or better on the crosstalks between Q, U, and V and that our model can reproduce the intensities in our calibration sequences to about 0.4%.

The amount of depolarization is negligible when the instrument is operated as intended which, combined with the flexibility of the polarimeter design, means that the polarimetric efficiency is excellent.