Calibrating Polarization Data Recalibrating WFPC2 Data Calibrating Polarization Data Work to calibrate the WFPC2 polarizers is still underway. In this section, we provide a preliminary sketch of how polarizer data are expected to be calibrated. Polarization measurements require that observations be taken with the polarizers set to three or more angles relative to the target. This can be achieved in a number of ways, by either using different quads of the polarizer filter, rotating the polarizer filter, rotating the spacecraft, or combinations of these methods.
Initial calibration proceeds in the same way as with any other images.
The data are bias, dark, and flatfield corrected in the normal manner. Next, the polarization properties of the source are derived by effectively plotting measured counts vs. polarizer position angle on the sky. Finally, sine curves are fit to these plots. The polarization angle of the target will then be derived from the phase of the fitted sine wave. Calibrations should be completed early in 1996, and a report will then be available giving details of the analysis methods.