The polarimetric radars o er the advantage of knowing about properties of target's surface by acquiring information of how the incident electromagnetic energy is scattered respect to orthogonal polarization vectors. Bistatic sensors of opportunity, such as SABRINA, can be adapted to perform polarimetric measurements if they found an illuminator which transmits pulses with orthogonal polarizations. In such scenario, calibration is required to scale properly the measurements in magnitude and phase in order to be able to interpret the data. In this work, we use the concepts of calibration in the monostatic case to obtain and study a polarimetric calibration based on PARCs for a bistatic sensor of opportunity.