16869

This program will obtain spectropolarimetry observations of a second polarized source to better calibrate the wavelengths < 0.75 microns comma and to rule out an ambiguity in the polarization angle zero point from the first polarized source. In addition comma the existing observations of the polarized calibrator are not sufficient to calibrate at wavelengths shorter that virgul0.65 micronswith any fidelity comma but do provide insight into the calibration at longer wavelengths.The main goal is to commission a new capability for HST-ACS-WFC by calibrating the combination of the G800L grism with the POLV polarizers to provide spectropolarimetry (R = 69 - 131) from 0.55 - 1.05 microns.