Astrophysics with a Soft X-ray Polarimeter

We are developing instrumentation for a telescope design capable of measuring linear X-ray polarization over a broad-band using conventional spectroscopic optics. Multilayer-coated mirrors are key to this approach, being used as Bragg reflectors at the Brewster angle. By laterally grading the multilayer mirrors and matching to the dispersion of a spectrometer, one may take advantage of high multilayer reflectivities and achieve modulation factors of nearly 100% over the entire 0.2-0.8 keV band. We present progress on laboratory work to demonstrate the capabilities of existing laterally graded multilayer coated mirrors. We also present plans for a suborbital rocket experiment designed to detect a polarization level of 10% for an active galactic nucleus in the soft X-ray band.