Using POLSIM to Investigate Noise Characteristics

The POLSIM application is a useful tool for investigating the noise within a set of observed intensity images. It takes in a cube of Stokes vectors as produced by POLCAL, together with a set of template intensity images, and creates a set of intensity images analogous to the templates, but filled with the expected intensity values given by equation . The analyser properties (angle, efficiency and transmission) are defined by the templates, as are the required pixel positions.

So if you use POLCAL to generate a cube of Stokes vectors from a set of observed intensity images, you could then use POLSIM to convert the Stokes vectors back into intensity estimates, using the original observed intensity images as templates. In a noise-free world, the resulting estimated intensity images should be identical to the original observed data. The presence of noise in the input data will result in this not being the case, and the residuals between the two sets of images will give an indication of the noise in the input images.

POLSIM can also be used to verify that the Stokes vectors produced by POLCAL are consistent with the observed data.