We describe the incorporation of polarized radiative transfer into the atmospheric radiative transfer modelling code vstar ( Versatile Software for Transfer of Atmospheric Radiation ) .
Using a vector discrete-ordinate radiative transfer code we are able to generate maps of radiance and polarization across the disc of a planet , and integrate over these to get the full-disc polarization .
In this way we are able to obtain disc-resolved , phase-resolved and spectrally-resolved intensity and polarization for any of the wide range of atmopsheres that can be modelled with vstar .
We have tested the code by reproducing a standard benchmark problem , as well as by comparing with classic calculations of the polarization phase curves of Venus .
We apply the code to modelling the polarization phase curves of the hot Jupiter system HD 189733b .
We find that the highest polarization amplitudes are produced with optically thick Rayleigh scattering clouds and these would result in a polarization amplitude of 27 ppm for the planetary signal seen in the combined light of the star and planet .
A more realistic cloud model consistent with the observed transmission spectrum results is an amplitude of \sim 20 ppm .
Decreasing the optical depth of the cloud , or making the cloud particles more absorbing , both have the effect of increasing the polarization of the reflected light but reducing the amount of reflected light and hence the observed polarization amplitude .